a9b5d968e5c6ca057af17dce49f8426ffb876641
[exim.git] / doc / doc-docbook / spec.xfpt
1 . /////////////////////////////////////////////////////////////////////////////
2 . This is the primary source of the Exim Manual. It is an xfpt document that is
3 . converted into DocBook XML for subsequent conversion into printing and online
4 . formats. The markup used herein is "standard" xfpt markup, with some extras.
5 . The markup is summarized in a file called Markup.txt.
6 .
7 . WARNING: When you use the .new macro, make sure it appears *before* any
8 . adjacent index items; otherwise you get an empty "paragraph" which causes
9 . unwanted vertical space.
10 . /////////////////////////////////////////////////////////////////////////////
11
12 .include stdflags
13 .include stdmacs
14
15 . /////////////////////////////////////////////////////////////////////////////
16 . This outputs the standard DocBook boilerplate.
17 . /////////////////////////////////////////////////////////////////////////////
18
19 .docbook
20
21 . /////////////////////////////////////////////////////////////////////////////
22 . These lines are processing instructions for the Simple DocBook Processor that
23 . Philip Hazel has developed as a less cumbersome way of making PostScript and
24 . PDFs than using xmlto and fop. They will be ignored by all other XML
25 . processors.
26 . /////////////////////////////////////////////////////////////////////////////
27
28 .literal xml
29 <?sdop
30 foot_right_recto="&chaptertitle; (&chapternumber;)"
31 foot_right_verso="&chaptertitle; (&chapternumber;)"
32 toc_chapter_blanks="yes,yes"
33 table_warn_overflow="overprint"
34 ?>
35 .literal off
36
37 . /////////////////////////////////////////////////////////////////////////////
38 . This generate the outermost <book> element that wraps then entire document.
39 . /////////////////////////////////////////////////////////////////////////////
40
41 .book
42
43 . /////////////////////////////////////////////////////////////////////////////
44 . These definitions set some parameters and save some typing.
45 . Update the Copyright year (only) when changing content.
46 . /////////////////////////////////////////////////////////////////////////////
47
48 .set previousversion "4.91"
49 .include ./local_params
50
51 .set ACL "access control lists (ACLs)"
52 .set I "&nbsp;&nbsp;&nbsp;&nbsp;"
53
54 .macro copyyear
55 2018
56 .endmacro
57
58 . /////////////////////////////////////////////////////////////////////////////
59 . Additional xfpt markup used by this document, over and above the default
60 . provided in the xfpt library.
61 . /////////////////////////////////////////////////////////////////////////////
62
63 . --- Override the &$ flag to automatically insert a $ with the variable name
64
65 .flag &$ $& "<varname>$" "</varname>"
66
67 . --- Short flags for daggers in option headings. They will always be inside
68 . --- an italic string, but we want the daggers to be roman.
69
70 .flag &!! "</emphasis>&dagger;<emphasis>"
71 .flag &!? "</emphasis>&Dagger;<emphasis>"
72
73 . --- A macro for an Exim option definition heading, generating a one-line
74 . --- table with four columns. For cases when the option name is given with
75 . --- a space, so that it can be split, a fifth argument is used for the
76 . --- index entry.
77
78 .macro option
79 .arg 5
80 .oindex "&%$5%&"
81 .endarg
82 .arg -5
83 .oindex "&%$1%&"
84 .endarg
85 .itable all 0 0 4 8* left 6* center 6* center 6* right
86 .row "&%$1%&" "Use: &'$2'&" "Type: &'$3'&" "Default: &'$4'&"
87 .endtable
88 .endmacro
89
90 . --- A macro for the common 2-column tables. The width of the first column
91 . --- is suitable for the many tables at the start of the main options chapter;
92 . --- the small number of other 2-column tables override it.
93
94 .macro table2 196pt 254pt
95 .itable none 0 0 2 $1 left $2 left
96 .endmacro
97
98 . --- A macro that generates .row, but puts &I; at the start of the first
99 . --- argument, thus indenting it. Assume a minimum of two arguments, and
100 . --- allow up to four arguments, which is as many as we'll ever need.
101
102 .macro irow
103 .arg 4
104 .row "&I;$1" "$2" "$3" "$4"
105 .endarg
106 .arg -4
107 .arg 3
108 .row "&I;$1" "$2" "$3"
109 .endarg
110 .arg -3
111 .row "&I;$1" "$2"
112 .endarg
113 .endarg
114 .endmacro
115
116 . --- Macros for option, variable, and concept index entries. For a "range"
117 . --- style of entry, use .scindex for the start and .ecindex for the end. The
118 . --- first argument of .scindex and the only argument of .ecindex must be the
119 . --- ID that ties them together.
120
121 .macro cindex
122 &<indexterm role="concept">&
123 &<primary>&$1&</primary>&
124 .arg 2
125 &<secondary>&$2&</secondary>&
126 .endarg
127 &</indexterm>&
128 .endmacro
129
130 .macro scindex
131 &<indexterm role="concept" id="$1" class="startofrange">&
132 &<primary>&$2&</primary>&
133 .arg 3
134 &<secondary>&$3&</secondary>&
135 .endarg
136 &</indexterm>&
137 .endmacro
138
139 .macro ecindex
140 &<indexterm role="concept" startref="$1" class="endofrange"/>&
141 .endmacro
142
143 .macro oindex
144 &<indexterm role="option">&
145 &<primary>&$1&</primary>&
146 .arg 2
147 &<secondary>&$2&</secondary>&
148 .endarg
149 &</indexterm>&
150 .endmacro
151
152 .macro vindex
153 &<indexterm role="variable">&
154 &<primary>&$1&</primary>&
155 .arg 2
156 &<secondary>&$2&</secondary>&
157 .endarg
158 &</indexterm>&
159 .endmacro
160
161 .macro index
162 .echo "** Don't use .index; use .cindex or .oindex or .vindex"
163 .endmacro
164 . ////////////////////////////////////////////////////////////////////////////
165
166
167 . ////////////////////////////////////////////////////////////////////////////
168 . The <bookinfo> element is removed from the XML before processing for Ascii
169 . output formats.
170 . ////////////////////////////////////////////////////////////////////////////
171
172 .literal xml
173 <bookinfo>
174 <title>Specification of the Exim Mail Transfer Agent</title>
175 <titleabbrev>The Exim MTA</titleabbrev>
176 <date>
177 .fulldate
178 </date>
179 <author><firstname>Exim</firstname><surname>Maintainers</surname></author>
180 <authorinitials>EM</authorinitials>
181 <revhistory><revision>
182 .versiondatexml
183 <authorinitials>EM</authorinitials>
184 </revision></revhistory>
185 <copyright><year>
186 .copyyear
187 </year><holder>University of Cambridge</holder></copyright>
188 </bookinfo>
189 .literal off
190
191
192 . /////////////////////////////////////////////////////////////////////////////
193 . This chunk of literal XML implements index entries of the form "x, see y" and
194 . "x, see also y". However, the DocBook DTD doesn't allow <indexterm> entries
195 . at the top level, so we have to put the .chapter directive first.
196 . /////////////////////////////////////////////////////////////////////////////
197
198 .chapter "Introduction" "CHID1"
199 .literal xml
200
201 <indexterm role="variable">
202 <primary>$1, $2, etc.</primary>
203 <see><emphasis>numerical variables</emphasis></see>
204 </indexterm>
205 <indexterm role="concept">
206 <primary>address</primary>
207 <secondary>rewriting</secondary>
208 <see><emphasis>rewriting</emphasis></see>
209 </indexterm>
210 <indexterm role="concept">
211 <primary>Bounce Address Tag Validation</primary>
212 <see><emphasis>BATV</emphasis></see>
213 </indexterm>
214 <indexterm role="concept">
215 <primary>Client SMTP Authorization</primary>
216 <see><emphasis>CSA</emphasis></see>
217 </indexterm>
218 <indexterm role="concept">
219 <primary>CR character</primary>
220 <see><emphasis>carriage return</emphasis></see>
221 </indexterm>
222 <indexterm role="concept">
223 <primary>CRL</primary>
224 <see><emphasis>certificate revocation list</emphasis></see>
225 </indexterm>
226 <indexterm role="concept">
227 <primary>delivery</primary>
228 <secondary>failure report</secondary>
229 <see><emphasis>bounce message</emphasis></see>
230 </indexterm>
231 <indexterm role="concept">
232 <primary>dialup</primary>
233 <see><emphasis>intermittently connected hosts</emphasis></see>
234 </indexterm>
235 <indexterm role="concept">
236 <primary>exiscan</primary>
237 <see><emphasis>content scanning</emphasis></see>
238 </indexterm>
239 <indexterm role="concept">
240 <primary>failover</primary>
241 <see><emphasis>fallback</emphasis></see>
242 </indexterm>
243 <indexterm role="concept">
244 <primary>fallover</primary>
245 <see><emphasis>fallback</emphasis></see>
246 </indexterm>
247 <indexterm role="concept">
248 <primary>filter</primary>
249 <secondary>Sieve</secondary>
250 <see><emphasis>Sieve filter</emphasis></see>
251 </indexterm>
252 <indexterm role="concept">
253 <primary>ident</primary>
254 <see><emphasis>RFC 1413</emphasis></see>
255 </indexterm>
256 <indexterm role="concept">
257 <primary>LF character</primary>
258 <see><emphasis>linefeed</emphasis></see>
259 </indexterm>
260 <indexterm role="concept">
261 <primary>maximum</primary>
262 <seealso><emphasis>limit</emphasis></seealso>
263 </indexterm>
264 <indexterm role="concept">
265 <primary>monitor</primary>
266 <see><emphasis>Exim monitor</emphasis></see>
267 </indexterm>
268 <indexterm role="concept">
269 <primary>no_<emphasis>xxx</emphasis></primary>
270 <see>entry for xxx</see>
271 </indexterm>
272 <indexterm role="concept">
273 <primary>NUL</primary>
274 <see><emphasis>binary zero</emphasis></see>
275 </indexterm>
276 <indexterm role="concept">
277 <primary>passwd file</primary>
278 <see><emphasis>/etc/passwd</emphasis></see>
279 </indexterm>
280 <indexterm role="concept">
281 <primary>process id</primary>
282 <see><emphasis>pid</emphasis></see>
283 </indexterm>
284 <indexterm role="concept">
285 <primary>RBL</primary>
286 <see><emphasis>DNS list</emphasis></see>
287 </indexterm>
288 <indexterm role="concept">
289 <primary>redirection</primary>
290 <see><emphasis>address redirection</emphasis></see>
291 </indexterm>
292 <indexterm role="concept">
293 <primary>return path</primary>
294 <seealso><emphasis>envelope sender</emphasis></seealso>
295 </indexterm>
296 <indexterm role="concept">
297 <primary>scanning</primary>
298 <see><emphasis>content scanning</emphasis></see>
299 </indexterm>
300 <indexterm role="concept">
301 <primary>SSL</primary>
302 <see><emphasis>TLS</emphasis></see>
303 </indexterm>
304 <indexterm role="concept">
305 <primary>string</primary>
306 <secondary>expansion</secondary>
307 <see><emphasis>expansion</emphasis></see>
308 </indexterm>
309 <indexterm role="concept">
310 <primary>top bit</primary>
311 <see><emphasis>8-bit characters</emphasis></see>
312 </indexterm>
313 <indexterm role="concept">
314 <primary>variables</primary>
315 <see><emphasis>expansion, variables</emphasis></see>
316 </indexterm>
317 <indexterm role="concept">
318 <primary>zero, binary</primary>
319 <see><emphasis>binary zero</emphasis></see>
320 </indexterm>
321
322 .literal off
323
324
325 . /////////////////////////////////////////////////////////////////////////////
326 . This is the real start of the first chapter. See the comment above as to why
327 . we can't have the .chapter line here.
328 . chapter "Introduction"
329 . /////////////////////////////////////////////////////////////////////////////
330
331 Exim is a mail transfer agent (MTA) for hosts that are running Unix or
332 Unix-like operating systems. It was designed on the assumption that it would be
333 run on hosts that are permanently connected to the Internet. However, it can be
334 used on intermittently connected hosts with suitable configuration adjustments.
335
336 Configuration files currently exist for the following operating systems: AIX,
337 BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd,
338 GNU/Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD,
339 OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4,
340 Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and Unixware.
341 Some of these operating systems are no longer current and cannot easily be
342 tested, so the configuration files may no longer work in practice.
343
344 There are also configuration files for compiling Exim in the Cygwin environment
345 that can be installed on systems running Windows. However, this document does
346 not contain any information about running Exim in the Cygwin environment.
347
348 The terms and conditions for the use and distribution of Exim are contained in
349 the file &_NOTICE_&. Exim is distributed under the terms of the GNU General
350 Public Licence, a copy of which may be found in the file &_LICENCE_&.
351
352 The use, supply or promotion of Exim for the purpose of sending bulk,
353 unsolicited electronic mail is incompatible with the basic aims of the program,
354 which revolve around the free provision of a service that enhances the quality
355 of personal communications. The author of Exim regards indiscriminate
356 mass-mailing as an antisocial, irresponsible abuse of the Internet.
357
358 Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
359 experience of running and working on the Smail 3 code, I could never have
360 contemplated starting to write a new MTA. Many of the ideas and user interfaces
361 were originally taken from Smail 3, though the actual code of Exim is entirely
362 new, and has developed far beyond the initial concept.
363
364 Many people, both in Cambridge and around the world, have contributed to the
365 development and the testing of Exim, and to porting it to various operating
366 systems. I am grateful to them all. The distribution now contains a file called
367 &_ACKNOWLEDGMENTS_&, in which I have started recording the names of
368 contributors.
369
370
371 .section "Exim documentation" "SECID1"
372 . Keep this example change bar when updating the documentation!
373
374 .new
375 .cindex "documentation"
376 This edition of the Exim specification applies to version &version() of Exim.
377 Substantive changes from the &previousversion; edition are marked in some
378 renditions of the document; this paragraph is so marked if the rendition is
379 capable of showing a change indicator.
380 .wen
381
382 This document is very much a reference manual; it is not a tutorial. The reader
383 is expected to have some familiarity with the SMTP mail transfer protocol and
384 with general Unix system administration. Although there are some discussions
385 and examples in places, the information is mostly organized in a way that makes
386 it easy to look up, rather than in a natural order for sequential reading.
387 Furthermore, the manual aims to cover every aspect of Exim in detail, including
388 a number of rarely-used, special-purpose features that are unlikely to be of
389 very wide interest.
390
391 .cindex "books about Exim"
392 An &"easier"& discussion of Exim which provides more in-depth explanatory,
393 introductory, and tutorial material can be found in a book entitled &'The Exim
394 SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge
395 (&url(http://www.uit.co.uk/exim-book/)).
396
397 This book also contains a chapter that gives a general introduction to SMTP and
398 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
399 with the latest release of Exim. (Note that the earlier book about Exim,
400 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
401
402 .cindex "Debian" "information sources"
403 If you are using a Debian distribution of Exim, you will find information about
404 Debian-specific features in the file
405 &_/usr/share/doc/exim4-base/README.Debian_&.
406 The command &(man update-exim.conf)& is another source of Debian-specific
407 information.
408
409 .cindex "&_doc/NewStuff_&"
410 .cindex "&_doc/ChangeLog_&"
411 .cindex "change log"
412 As the program develops, there may be features in newer versions that have not
413 yet made it into this document, which is updated only when the most significant
414 digit of the fractional part of the version number changes. Specifications of
415 new features that are not yet in this manual are placed in the file
416 &_doc/NewStuff_& in the Exim distribution.
417
418 Some features may be classified as &"experimental"&. These may change
419 incompatibly while they are developing, or even be withdrawn. For this reason,
420 they are not documented in this manual. Information about experimental features
421 can be found in the file &_doc/experimental.txt_&.
422
423 All changes to the program (whether new features, bug fixes, or other kinds of
424 change) are noted briefly in the file called &_doc/ChangeLog_&.
425
426 .cindex "&_doc/spec.txt_&"
427 This specification itself is available as an ASCII file in &_doc/spec.txt_& so
428 that it can easily be searched with a text editor. Other files in the &_doc_&
429 directory are:
430
431 .table2 100pt
432 .row &_OptionLists.txt_& "list of all options in alphabetical order"
433 .row &_dbm.discuss.txt_& "discussion about DBM libraries"
434 .row &_exim.8_& "a man page of Exim's command line options"
435 .row &_experimental.txt_& "documentation of experimental features"
436 .row &_filter.txt_& "specification of the filter language"
437 .row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3"
438 .row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4"
439 .row &_openssl.txt_& "installing a current OpenSSL release"
440 .endtable
441
442 The main specification and the specification of the filtering language are also
443 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
444 &<<SECTavail>>& below tells you how to get hold of these.
445
446
447
448 .section "FTP and web sites" "SECID2"
449 .cindex "web site"
450 .cindex "FTP site"
451 The primary site for Exim source distributions is the &%exim.org%& FTP site,
452 available over HTTPS, HTTP and FTP. These services, and the &%exim.org%&
453 website, are hosted at the University of Cambridge.
454
455 .cindex "wiki"
456 .cindex "FAQ"
457 As well as Exim distribution tar files, the Exim web site contains a number of
458 differently formatted versions of the documentation. A recent addition to the
459 online information is the Exim wiki (&url(http://wiki.exim.org)),
460 which contains what used to be a separate FAQ, as well as various other
461 examples, tips, and know-how that have been contributed by Exim users.
462 The wiki site should always redirect to the correct place, which is currently
463 provided by GitHub, and is open to editing by anyone with a GitHub account.
464
465 .cindex Bugzilla
466 An Exim Bugzilla exists at &url(https://bugs.exim.org). You can use
467 this to report bugs, and also to add items to the wish list. Please search
468 first to check that you are not duplicating a previous entry.
469 Please do not ask for configuration help in the bug-tracker.
470
471
472 .section "Mailing lists" "SECID3"
473 .cindex "mailing lists" "for Exim users"
474 The following Exim mailing lists exist:
475
476 .table2 140pt
477 .row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
478 .row &'exim-users@exim.org'& "General discussion list"
479 .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc."
480 .row &'exim-cvs@exim.org'& "Automated commit messages from the VCS"
481 .endtable
482
483 You can subscribe to these lists, change your existing subscriptions, and view
484 or search the archives via the mailing lists link on the Exim home page.
485 .cindex "Debian" "mailing list for"
486 If you are using a Debian distribution of Exim, you may wish to subscribe to
487 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
488 via this web page:
489 .display
490 &url(http://lists.alioth.debian.org/mailman/listinfo/pkg-exim4-users)
491 .endd
492 Please ask Debian-specific questions on this list and not on the general Exim
493 lists.
494
495 .section "Bug reports" "SECID5"
496 .cindex "bug reports"
497 .cindex "reporting bugs"
498 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
499 via the Bugzilla (&url(https://bugs.exim.org)). However, if you are unsure
500 whether some behaviour is a bug or not, the best thing to do is to post a
501 message to the &'exim-dev'& mailing list and have it discussed.
502
503
504
505 .section "Where to find the Exim distribution" "SECTavail"
506 .cindex "FTP site"
507 .cindex "HTTPS download site"
508 .cindex "distribution" "ftp site"
509 .cindex "distribution" "https site"
510 The master distribution site for the Exim distribution is
511 .display
512 &*https://downloads.exim.org/*&
513 .endd
514 The service is available over HTTPS, HTTP and FTP.
515 We encourage people to migrate to HTTPS.
516
517 The content served at &'https://downloads.exim.org/'& is identical to the
518 content served at &'https://ftp.exim.org/pub/exim'& and
519 &'ftp://ftp.exim.org/pub/exim'&.
520
521 If accessing via a hostname containing &'ftp'&, then the file references that
522 follow are relative to the &_exim_& directories at these sites.
523 If accessing via the hostname &'downloads'& then the subdirectories described
524 here are top-level directories.
525
526 There are now quite a number of independent mirror sites around
527 the world. Those that I know about are listed in the file called &_Mirrors_&.
528
529 Within the top exim directory there are subdirectories called &_exim3_& (for
530 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
531 distributions), and &_Testing_& for testing versions. In the &_exim4_&
532 subdirectory, the current release can always be found in files called
533 .display
534 &_exim-n.nn.tar.xz_&
535 &_exim-n.nn.tar.gz_&
536 &_exim-n.nn.tar.bz2_&
537 .endd
538 where &'n.nn'& is the highest such version number in the directory. The three
539 files contain identical data; the only difference is the type of compression.
540 The &_.xz_& file is usually the smallest, while the &_.gz_& file is the
541 most portable to old systems.
542
543 .cindex "distribution" "signing details"
544 .cindex "distribution" "public key"
545 .cindex "public key for signed distribution"
546 The distributions will be PGP signed by an individual key of the Release
547 Coordinator. This key will have a uid containing an email address in the
548 &'exim.org'& domain and will have signatures from other people, including
549 other Exim maintainers. We expect that the key will be in the "strong set" of
550 PGP keys. There should be a trust path to that key from Nigel Metheringham's
551 PGP key, a version of which can be found in the release directory in the file
552 &_nigel-pubkey.asc_&. All keys used will be available in public keyserver pools,
553 such as &'pool.sks-keyservers.net'&.
554
555 At time of last update, releases were being made by Jeremy Harris and signed
556 with key &'0xBCE58C8CE41F32DF'&. Other recent keys used for signing are those
557 of Heiko Schlittermann, &'0x26101B62F69376CE'&,
558 and of Phil Pennock, &'0x4D1E900E14C1CC04'&.
559
560 The signatures for the tar bundles are in:
561 .display
562 &_exim-n.nn.tar.xz.asc_&
563 &_exim-n.nn.tar.gz.asc_&
564 &_exim-n.nn.tar.bz2.asc_&
565 .endd
566 For each released version, the log of changes is made separately available in a
567 separate file in the directory &_ChangeLogs_& so that it is possible to
568 find out what has changed without having to download the entire distribution.
569
570 .cindex "documentation" "available formats"
571 The main distribution contains ASCII versions of this specification and other
572 documentation; other formats of the documents are available in separate files
573 inside the &_exim4_& directory of the FTP site:
574 .display
575 &_exim-html-n.nn.tar.gz_&
576 &_exim-pdf-n.nn.tar.gz_&
577 &_exim-postscript-n.nn.tar.gz_&
578 &_exim-texinfo-n.nn.tar.gz_&
579 .endd
580 These tar files contain only the &_doc_& directory, not the complete
581 distribution, and are also available in &_.bz2_& and &_.xz_& forms.
582
583
584 .section "Limitations" "SECID6"
585 .ilist
586 .cindex "limitations of Exim"
587 .cindex "bang paths" "not handled by Exim"
588 Exim is designed for use as an Internet MTA, and therefore handles addresses in
589 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
590 simple two-component bang paths can be converted by a straightforward rewriting
591 configuration. This restriction does not prevent Exim from being interfaced to
592 UUCP as a transport mechanism, provided that domain addresses are used.
593 .next
594 .cindex "domainless addresses"
595 .cindex "address" "without domain"
596 Exim insists that every address it handles has a domain attached. For incoming
597 local messages, domainless addresses are automatically qualified with a
598 configured domain value. Configuration options specify from which remote
599 systems unqualified addresses are acceptable. These are then qualified on
600 arrival.
601 .next
602 .cindex "transport" "external"
603 .cindex "external transports"
604 The only external transport mechanisms that are currently implemented are SMTP
605 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
606 transport is available, and there are facilities for writing messages to files
607 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
608 to send messages to other transport mechanisms such as UUCP, provided they can
609 handle domain-style addresses. Batched SMTP input is also catered for.
610 .next
611 Exim is not designed for storing mail for dial-in hosts. When the volumes of
612 such mail are large, it is better to get the messages &"delivered"& into files
613 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
614 other means.
615 .next
616 Although Exim does have basic facilities for scanning incoming messages, these
617 are not comprehensive enough to do full virus or spam scanning. Such operations
618 are best carried out using additional specialized software packages. If you
619 compile Exim with the content-scanning extension, straightforward interfaces to
620 a number of common scanners are provided.
621 .endlist
622
623
624 .section "Run time configuration" "SECID7"
625 Exim's run time configuration is held in a single text file that is divided
626 into a number of sections. The entries in this file consist of keywords and
627 values, in the style of Smail 3 configuration files. A default configuration
628 file which is suitable for simple online installations is provided in the
629 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
630
631
632 .section "Calling interface" "SECID8"
633 .cindex "Sendmail compatibility" "command line interface"
634 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
635 can be a straight replacement for &_/usr/lib/sendmail_& or
636 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
637 about Sendmail in order to run Exim. For actions other than sending messages,
638 Sendmail-compatible options also exist, but those that produce output (for
639 example, &%-bp%&, which lists the messages on the queue) do so in Exim's own
640 format. There are also some additional options that are compatible with Smail
641 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
642 documents all Exim's command line options. This information is automatically
643 made into the man page that forms part of the Exim distribution.
644
645 Control of messages on the queue can be done via certain privileged command
646 line options. There is also an optional monitor program called &'eximon'&,
647 which displays current information in an X window, and which contains a menu
648 interface to Exim's command line administration options.
649
650
651
652 .section "Terminology" "SECID9"
653 .cindex "terminology definitions"
654 .cindex "body of message" "definition of"
655 The &'body'& of a message is the actual data that the sender wants to transmit.
656 It is the last part of a message, and is separated from the &'header'& (see
657 below) by a blank line.
658
659 .cindex "bounce message" "definition of"
660 When a message cannot be delivered, it is normally returned to the sender in a
661 delivery failure message or a &"non-delivery report"& (NDR). The term
662 &'bounce'& is commonly used for this action, and the error reports are often
663 called &'bounce messages'&. This is a convenient shorthand for &"delivery
664 failure error report"&. Such messages have an empty sender address in the
665 message's &'envelope'& (see below) to ensure that they cannot themselves give
666 rise to further bounce messages.
667
668 The term &'default'& appears frequently in this manual. It is used to qualify a
669 value which is used in the absence of any setting in the configuration. It may
670 also qualify an action which is taken unless a configuration setting specifies
671 otherwise.
672
673 The term &'defer'& is used when the delivery of a message to a specific
674 destination cannot immediately take place for some reason (a remote host may be
675 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
676 until a later time.
677
678 The word &'domain'& is sometimes used to mean all but the first component of a
679 host's name. It is &'not'& used in that sense here, where it normally refers to
680 the part of an email address following the @ sign.
681
682 .cindex "envelope, definition of"
683 .cindex "sender" "definition of"
684 A message in transit has an associated &'envelope'&, as well as a header and a
685 body. The envelope contains a sender address (to which bounce messages should
686 be delivered), and any number of recipient addresses. References to the
687 sender or the recipients of a message usually mean the addresses in the
688 envelope. An MTA uses these addresses for delivery, and for returning bounce
689 messages, not the addresses that appear in the header lines.
690
691 .cindex "message" "header, definition of"
692 .cindex "header section" "definition of"
693 The &'header'& of a message is the first part of a message's text, consisting
694 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
695 &'Subject:'&, etc. Long header lines can be split over several text lines by
696 indenting the continuations. The header is separated from the body by a blank
697 line.
698
699 .cindex "local part" "definition of"
700 .cindex "domain" "definition of"
701 The term &'local part'&, which is taken from RFC 2822, is used to refer to that
702 part of an email address that precedes the @ sign. The part that follows the
703 @ sign is called the &'domain'& or &'mail domain'&.
704
705 .cindex "local delivery" "definition of"
706 .cindex "remote delivery, definition of"
707 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
708 delivery to a file or a pipe on the local host from delivery by SMTP over
709 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
710 host it is running on are &'remote'&.
711
712 .cindex "return path" "definition of"
713 &'Return path'& is another name that is used for the sender address in a
714 message's envelope.
715
716 .cindex "queue" "definition of"
717 The term &'queue'& is used to refer to the set of messages awaiting delivery,
718 because this term is in widespread use in the context of MTAs. However, in
719 Exim's case the reality is more like a pool than a queue, because there is
720 normally no ordering of waiting messages.
721
722 .cindex "queue runner" "definition of"
723 The term &'queue runner'& is used to describe a process that scans the queue
724 and attempts to deliver those messages whose retry times have come. This term
725 is used by other MTAs, and also relates to the command &%runq%&, but in Exim
726 the waiting messages are normally processed in an unpredictable order.
727
728 .cindex "spool directory" "definition of"
729 The term &'spool directory'& is used for a directory in which Exim keeps the
730 messages on its queue &-- that is, those that it is in the process of
731 delivering. This should not be confused with the directory in which local
732 mailboxes are stored, which is called a &"spool directory"& by some people. In
733 the Exim documentation, &"spool"& is always used in the first sense.
734
735
736
737
738
739
740 . ////////////////////////////////////////////////////////////////////////////
741 . ////////////////////////////////////////////////////////////////////////////
742
743 .chapter "Incorporated code" "CHID2"
744 .cindex "incorporated code"
745 .cindex "regular expressions" "library"
746 .cindex "PCRE"
747 .cindex "OpenDMARC"
748 A number of pieces of external code are included in the Exim distribution.
749
750 .ilist
751 Regular expressions are supported in the main Exim program and in the
752 Exim monitor using the freely-distributable PCRE library, copyright
753 &copy; University of Cambridge. The source to PCRE is no longer shipped with
754 Exim, so you will need to use the version of PCRE shipped with your system,
755 or obtain and install the full version of the library from
756 &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
757 .next
758 .cindex "cdb" "acknowledgment"
759 Support for the cdb (Constant DataBase) lookup method is provided by code
760 contributed by Nigel Metheringham of (at the time he contributed it) Planet
761 Online Ltd. The implementation is completely contained within the code of Exim.
762 It does not link against an external cdb library. The code contains the
763 following statements:
764
765 .blockquote
766 Copyright &copy; 1998 Nigel Metheringham, Planet Online Ltd
767
768 This program is free software; you can redistribute it and/or modify it under
769 the terms of the GNU General Public License as published by the Free Software
770 Foundation; either version 2 of the License, or (at your option) any later
771 version.
772 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
773 the spec and sample code for cdb can be obtained from
774 &url(http://www.pobox.com/~djb/cdb.html). This implementation borrows
775 some code from Dan Bernstein's implementation (which has no license
776 restrictions applied to it).
777 .endblockquote
778 .next
779 .cindex "SPA authentication"
780 .cindex "Samba project"
781 .cindex "Microsoft Secure Password Authentication"
782 Client support for Microsoft's &'Secure Password Authentication'& is provided
783 by code contributed by Marc Prud'hommeaux. Server support was contributed by
784 Tom Kistner. This includes code taken from the Samba project, which is released
785 under the Gnu GPL.
786 .next
787 .cindex "Cyrus"
788 .cindex "&'pwcheck'& daemon"
789 .cindex "&'pwauthd'& daemon"
790 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
791 by code taken from the Cyrus-SASL library and adapted by Alexander S.
792 Sabourenkov. The permission notice appears below, in accordance with the
793 conditions expressed therein.
794
795 .blockquote
796 Copyright &copy; 2001 Carnegie Mellon University. All rights reserved.
797
798 Redistribution and use in source and binary forms, with or without
799 modification, are permitted provided that the following conditions
800 are met:
801
802 .olist
803 Redistributions of source code must retain the above copyright
804 notice, this list of conditions and the following disclaimer.
805 .next
806 Redistributions in binary form must reproduce the above copyright
807 notice, this list of conditions and the following disclaimer in
808 the documentation and/or other materials provided with the
809 distribution.
810 .next
811 The name &"Carnegie Mellon University"& must not be used to
812 endorse or promote products derived from this software without
813 prior written permission. For permission or any other legal
814 details, please contact
815 .display
816 Office of Technology Transfer
817 Carnegie Mellon University
818 5000 Forbes Avenue
819 Pittsburgh, PA 15213-3890
820 (412) 268-4387, fax: (412) 268-7395
821 tech-transfer@andrew.cmu.edu
822 .endd
823 .next
824 Redistributions of any form whatsoever must retain the following
825 acknowledgment:
826
827 &"This product includes software developed by Computing Services
828 at Carnegie Mellon University (&url(http://www.cmu.edu/computing/)."&
829
830 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
831 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
832 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
833 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
834 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
835 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
836 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
837 .endlist
838 .endblockquote
839
840 .next
841 .cindex "Exim monitor" "acknowledgment"
842 .cindex "X-windows"
843 .cindex "Athena"
844 The Exim Monitor program, which is an X-Window application, includes
845 modified versions of the Athena StripChart and TextPop widgets.
846 This code is copyright by DEC and MIT, and their permission notice appears
847 below, in accordance with the conditions expressed therein.
848
849 .blockquote
850 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
851 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
852
853 All Rights Reserved
854
855 Permission to use, copy, modify, and distribute this software and its
856 documentation for any purpose and without fee is hereby granted,
857 provided that the above copyright notice appear in all copies and that
858 both that copyright notice and this permission notice appear in
859 supporting documentation, and that the names of Digital or MIT not be
860 used in advertising or publicity pertaining to distribution of the
861 software without specific, written prior permission.
862
863 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
864 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
865 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
866 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
867 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
868 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
869 SOFTWARE.
870 .endblockquote
871
872 .next
873 .cindex "opendmarc" "acknowledgment"
874 The DMARC implementation uses the OpenDMARC library which is Copyrighted by
875 The Trusted Domain Project. Portions of Exim source which use OpenDMARC
876 derived code are indicated in the respective source files. The full OpenDMARC
877 license is provided in the LICENSE.opendmarc file contained in the distributed
878 source code.
879
880 .next
881 Many people have contributed code fragments, some large, some small, that were
882 not covered by any specific licence requirements. It is assumed that the
883 contributors are happy to see their code incorporated into Exim under the GPL.
884 .endlist
885
886
887
888
889
890 . ////////////////////////////////////////////////////////////////////////////
891 . ////////////////////////////////////////////////////////////////////////////
892
893 .chapter "How Exim receives and delivers mail" "CHID11" &&&
894 "Receiving and delivering mail"
895
896
897 .section "Overall philosophy" "SECID10"
898 .cindex "design philosophy"
899 Exim is designed to work efficiently on systems that are permanently connected
900 to the Internet and are handling a general mix of mail. In such circumstances,
901 most messages can be delivered immediately. Consequently, Exim does not
902 maintain independent queues of messages for specific domains or hosts, though
903 it does try to send several messages in a single SMTP connection after a host
904 has been down, and it also maintains per-host retry information.
905
906
907 .section "Policy control" "SECID11"
908 .cindex "policy control" "overview"
909 Policy controls are now an important feature of MTAs that are connected to the
910 Internet. Perhaps their most important job is to stop MTAs being abused as
911 &"open relays"& by misguided individuals who send out vast amounts of
912 unsolicited junk, and want to disguise its source. Exim provides flexible
913 facilities for specifying policy controls on incoming mail:
914
915 .ilist
916 .cindex "&ACL;" "introduction"
917 Exim 4 (unlike previous versions of Exim) implements policy controls on
918 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
919 series of statements that may either grant or deny access. ACLs can be used at
920 several places in the SMTP dialogue while receiving a message from a remote
921 host. However, the most common places are after each RCPT command, and at the
922 very end of the message. The sysadmin can specify conditions for accepting or
923 rejecting individual recipients or the entire message, respectively, at these
924 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
925 error code.
926 .next
927 An ACL is also available for locally generated, non-SMTP messages. In this
928 case, the only available actions are to accept or deny the entire message.
929 .next
930 When Exim is compiled with the content-scanning extension, facilities are
931 provided in the ACL mechanism for passing the message to external virus and/or
932 spam scanning software. The result of such a scan is passed back to the ACL,
933 which can then use it to decide what to do with the message.
934 .next
935 When a message has been received, either from a remote host or from the local
936 host, but before the final acknowledgment has been sent, a locally supplied C
937 function called &[local_scan()]& can be run to inspect the message and decide
938 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
939 is accepted, the list of recipients can be modified by the function.
940 .next
941 Using the &[local_scan()]& mechanism is another way of calling external scanner
942 software. The &%SA-Exim%& add-on package works this way. It does not require
943 Exim to be compiled with the content-scanning extension.
944 .next
945 After a message has been accepted, a further checking mechanism is available in
946 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
947 runs at the start of every delivery process.
948 .endlist
949
950
951
952 .section "User filters" "SECID12"
953 .cindex "filter" "introduction"
954 .cindex "Sieve filter"
955 In a conventional Exim configuration, users are able to run private filters by
956 setting up appropriate &_.forward_& files in their home directories. See
957 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
958 configuration needed to support this, and the separate document entitled
959 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
960 of filtering are available:
961
962 .ilist
963 Sieve filters are written in the standard filtering language that is defined
964 by RFC 3028.
965 .next
966 Exim filters are written in a syntax that is unique to Exim, but which is more
967 powerful than Sieve, which it pre-dates.
968 .endlist
969
970 User filters are run as part of the routing process, described below.
971
972
973
974 .section "Message identification" "SECTmessiden"
975 .cindex "message ids" "details of format"
976 .cindex "format" "of message id"
977 .cindex "id of message"
978 .cindex "base62"
979 .cindex "base36"
980 .cindex "Darwin"
981 .cindex "Cygwin"
982 Every message handled by Exim is given a &'message id'& which is sixteen
983 characters long. It is divided into three parts, separated by hyphens, for
984 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
985 normally encoding numbers in base 62. However, in the Darwin operating
986 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
987 (avoiding the use of lower case letters) is used instead, because the message
988 id is used to construct file names, and the names of files in those systems are
989 not always case-sensitive.
990
991 .cindex "pid (process id)" "re-use of"
992 The detail of the contents of the message id have changed as Exim has evolved.
993 Earlier versions relied on the operating system not re-using a process id (pid)
994 within one second. On modern operating systems, this assumption can no longer
995 be made, so the algorithm had to be changed. To retain backward compatibility,
996 the format of the message id was retained, which is why the following rules are
997 somewhat eccentric:
998
999 .ilist
1000 The first six characters of the message id are the time at which the message
1001 started to be received, to a granularity of one second. That is, this field
1002 contains the number of seconds since the start of the epoch (the normal Unix
1003 way of representing the date and time of day).
1004 .next
1005 After the first hyphen, the next six characters are the id of the process that
1006 received the message.
1007 .next
1008 There are two different possibilities for the final two characters:
1009 .olist
1010 .oindex "&%localhost_number%&"
1011 If &%localhost_number%& is not set, this value is the fractional part of the
1012 time of reception, normally in units of 1/2000 of a second, but for systems
1013 that must use base 36 instead of base 62 (because of case-insensitive file
1014 systems), the units are 1/1000 of a second.
1015 .next
1016 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
1017 the fractional part of the time, which in this case is in units of 1/200
1018 (1/100) of a second.
1019 .endlist
1020 .endlist
1021
1022 After a message has been received, Exim waits for the clock to tick at the
1023 appropriate resolution before proceeding, so that if another message is
1024 received by the same process, or by another process with the same (re-used)
1025 pid, it is guaranteed that the time will be different. In most cases, the clock
1026 will already have ticked while the message was being received.
1027
1028
1029 .section "Receiving mail" "SECID13"
1030 .cindex "receiving mail"
1031 .cindex "message" "reception"
1032 The only way Exim can receive mail from another host is using SMTP over
1033 TCP/IP, in which case the sender and recipient addresses are transferred using
1034 SMTP commands. However, from a locally running process (such as a user's MUA),
1035 there are several possibilities:
1036
1037 .ilist
1038 If the process runs Exim with the &%-bm%& option, the message is read
1039 non-interactively (usually via a pipe), with the recipients taken from the
1040 command line, or from the body of the message if &%-t%& is also used.
1041 .next
1042 If the process runs Exim with the &%-bS%& option, the message is also read
1043 non-interactively, but in this case the recipients are listed at the start of
1044 the message in a series of SMTP RCPT commands, terminated by a DATA
1045 command. This is so-called &"batch SMTP"& format,
1046 but it isn't really SMTP. The SMTP commands are just another way of passing
1047 envelope addresses in a non-interactive submission.
1048 .next
1049 If the process runs Exim with the &%-bs%& option, the message is read
1050 interactively, using the SMTP protocol. A two-way pipe is normally used for
1051 passing data between the local process and the Exim process.
1052 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1053 example, the ACLs for SMTP commands are used for this form of submission.
1054 .next
1055 A local process may also make a TCP/IP call to the host's loopback address
1056 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1057 does not treat the loopback address specially. It treats all such connections
1058 in the same way as connections from other hosts.
1059 .endlist
1060
1061
1062 .cindex "message sender, constructed by Exim"
1063 .cindex "sender" "constructed by Exim"
1064 In the three cases that do not involve TCP/IP, the sender address is
1065 constructed from the login name of the user that called Exim and a default
1066 qualification domain (which can be set by the &%qualify_domain%& configuration
1067 option). For local or batch SMTP, a sender address that is passed using the
1068 SMTP MAIL command is ignored. However, the system administrator may allow
1069 certain users (&"trusted users"&) to specify a different sender address
1070 unconditionally, or all users to specify certain forms of different sender
1071 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1072 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1073 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1074 users to change sender addresses.
1075
1076 Messages received by either of the non-interactive mechanisms are subject to
1077 checking by the non-SMTP ACL, if one is defined. Messages received using SMTP
1078 (either over TCP/IP, or interacting with a local process) can be checked by a
1079 number of ACLs that operate at different times during the SMTP session. Either
1080 individual recipients, or the entire message, can be rejected if local policy
1081 requirements are not met. The &[local_scan()]& function (see chapter
1082 &<<CHAPlocalscan>>&) is run for all incoming messages.
1083
1084 Exim can be configured not to start a delivery process when a message is
1085 received; this can be unconditional, or depend on the number of incoming SMTP
1086 connections or the system load. In these situations, new messages wait on the
1087 queue until a queue runner process picks them up. However, in standard
1088 configurations under normal conditions, delivery is started as soon as a
1089 message is received.
1090
1091
1092
1093
1094
1095 .section "Handling an incoming message" "SECID14"
1096 .cindex "spool directory" "files that hold a message"
1097 .cindex "file" "how a message is held"
1098 When Exim accepts a message, it writes two files in its spool directory. The
1099 first contains the envelope information, the current status of the message, and
1100 the header lines, and the second contains the body of the message. The names of
1101 the two spool files consist of the message id, followed by &`-H`& for the
1102 file containing the envelope and header, and &`-D`& for the data file.
1103
1104 .cindex "spool directory" "&_input_& sub-directory"
1105 By default all these message files are held in a single directory called
1106 &_input_& inside the general Exim spool directory. Some operating systems do
1107 not perform very well if the number of files in a directory gets large; to
1108 improve performance in such cases, the &%split_spool_directory%& option can be
1109 used. This causes Exim to split up the input files into 62 sub-directories
1110 whose names are single letters or digits. When this is done, the queue is
1111 processed one sub-directory at a time instead of all at once, which can improve
1112 overall performance even when there are not enough files in each directory to
1113 affect file system performance.
1114
1115 The envelope information consists of the address of the message's sender and
1116 the addresses of the recipients. This information is entirely separate from
1117 any addresses contained in the header lines. The status of the message includes
1118 a list of recipients who have already received the message. The format of the
1119 first spool file is described in chapter &<<CHAPspool>>&.
1120
1121 .cindex "rewriting" "addresses"
1122 Address rewriting that is specified in the rewrite section of the configuration
1123 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1124 both in the header lines and the envelope, at the time the message is accepted.
1125 If during the course of delivery additional addresses are generated (for
1126 example, via aliasing), these new addresses are rewritten as soon as they are
1127 generated. At the time a message is actually delivered (transported) further
1128 rewriting can take place; because this is a transport option, it can be
1129 different for different forms of delivery. It is also possible to specify the
1130 addition or removal of certain header lines at the time the message is
1131 delivered (see chapters &<<CHAProutergeneric>>& and
1132 &<<CHAPtransportgeneric>>&).
1133
1134
1135
1136 .section "Life of a message" "SECID15"
1137 .cindex "message" "life of"
1138 .cindex "message" "frozen"
1139 A message remains in the spool directory until it is completely delivered to
1140 its recipients or to an error address, or until it is deleted by an
1141 administrator or by the user who originally created it. In cases when delivery
1142 cannot proceed &-- for example, when a message can neither be delivered to its
1143 recipients nor returned to its sender, the message is marked &"frozen"& on the
1144 spool, and no more deliveries are attempted.
1145
1146 .cindex "frozen messages" "thawing"
1147 .cindex "message" "thawing frozen"
1148 An administrator can &"thaw"& such messages when the problem has been
1149 corrected, and can also freeze individual messages by hand if necessary. In
1150 addition, an administrator can force a delivery error, causing a bounce message
1151 to be sent.
1152
1153 .oindex "&%timeout_frozen_after%&"
1154 .oindex "&%ignore_bounce_errors_after%&"
1155 There are options called &%ignore_bounce_errors_after%& and
1156 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1157 The first applies only to frozen bounces, the second to any frozen messages.
1158
1159 .cindex "message" "log file for"
1160 .cindex "log" "file for each message"
1161 While Exim is working on a message, it writes information about each delivery
1162 attempt to its main log file. This includes successful, unsuccessful, and
1163 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1164 lines are also written to a separate &'message log'& file for each message.
1165 These logs are solely for the benefit of the administrator, and are normally
1166 deleted along with the spool files when processing of a message is complete.
1167 The use of individual message logs can be disabled by setting
1168 &%no_message_logs%&; this might give an improvement in performance on very busy
1169 systems.
1170
1171 .cindex "journal file"
1172 .cindex "file" "journal"
1173 All the information Exim itself needs to set up a delivery is kept in the first
1174 spool file, along with the header lines. When a successful delivery occurs, the
1175 address is immediately written at the end of a journal file, whose name is the
1176 message id followed by &`-J`&. At the end of a delivery run, if there are some
1177 addresses left to be tried again later, the first spool file (the &`-H`& file)
1178 is updated to indicate which these are, and the journal file is then deleted.
1179 Updating the spool file is done by writing a new file and renaming it, to
1180 minimize the possibility of data loss.
1181
1182 Should the system or the program crash after a successful delivery but before
1183 the spool file has been updated, the journal is left lying around. The next
1184 time Exim attempts to deliver the message, it reads the journal file and
1185 updates the spool file before proceeding. This minimizes the chances of double
1186 deliveries caused by crashes.
1187
1188
1189
1190 .section "Processing an address for delivery" "SECTprocaddress"
1191 .cindex "drivers" "definition of"
1192 .cindex "router" "definition of"
1193 .cindex "transport" "definition of"
1194 The main delivery processing elements of Exim are called &'routers'& and
1195 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1196 number of them is provided in the source distribution, and compile-time options
1197 specify which ones are included in the binary. Run time options specify which
1198 ones are actually used for delivering messages.
1199
1200 .cindex "drivers" "instance definition"
1201 Each driver that is specified in the run time configuration is an &'instance'&
1202 of that particular driver type. Multiple instances are allowed; for example,
1203 you can set up several different &(smtp)& transports, each with different
1204 option values that might specify different ports or different timeouts. Each
1205 instance has its own identifying name. In what follows we will normally use the
1206 instance name when discussing one particular instance (that is, one specific
1207 configuration of the driver), and the generic driver name when discussing
1208 the driver's features in general.
1209
1210 A &'router'& is a driver that operates on an address, either determining how
1211 its delivery should happen, by assigning it to a specific transport, or
1212 converting the address into one or more new addresses (for example, via an
1213 alias file). A router may also explicitly choose to fail an address, causing it
1214 to be bounced.
1215
1216 A &'transport'& is a driver that transmits a copy of the message from Exim's
1217 spool to some destination. There are two kinds of transport: for a &'local'&
1218 transport, the destination is a file or a pipe on the local host, whereas for a
1219 &'remote'& transport the destination is some other host. A message is passed
1220 to a specific transport as a result of successful routing. If a message has
1221 several recipients, it may be passed to a number of different transports.
1222
1223 .cindex "preconditions" "definition of"
1224 An address is processed by passing it to each configured router instance in
1225 turn, subject to certain preconditions, until a router accepts the address or
1226 specifies that it should be bounced. We will describe this process in more
1227 detail shortly. First, as a simple example, we consider how each recipient
1228 address in a message is processed in a small configuration of three routers.
1229
1230 To make this a more concrete example, it is described in terms of some actual
1231 routers, but remember, this is only an example. You can configure Exim's
1232 routers in many different ways, and there may be any number of routers in a
1233 configuration.
1234
1235 The first router that is specified in a configuration is often one that handles
1236 addresses in domains that are not recognized specially by the local host. These
1237 are typically addresses for arbitrary domains on the Internet. A precondition
1238 is set up which looks for the special domains known to the host (for example,
1239 its own domain name), and the router is run for addresses that do &'not'&
1240 match. Typically, this is a router that looks up domains in the DNS in order to
1241 find the hosts to which this address routes. If it succeeds, the address is
1242 assigned to a suitable SMTP transport; if it does not succeed, the router is
1243 configured to fail the address.
1244
1245 The second router is reached only when the domain is recognized as one that
1246 &"belongs"& to the local host. This router does redirection &-- also known as
1247 aliasing and forwarding. When it generates one or more new addresses from the
1248 original, each of them is routed independently from the start. Otherwise, the
1249 router may cause an address to fail, or it may simply decline to handle the
1250 address, in which case the address is passed to the next router.
1251
1252 The final router in many configurations is one that checks to see if the
1253 address belongs to a local mailbox. The precondition may involve a check to
1254 see if the local part is the name of a login account, or it may look up the
1255 local part in a file or a database. If its preconditions are not met, or if
1256 the router declines, we have reached the end of the routers. When this happens,
1257 the address is bounced.
1258
1259
1260
1261 .section "Processing an address for verification" "SECID16"
1262 .cindex "router" "for verification"
1263 .cindex "verifying address" "overview"
1264 As well as being used to decide how to deliver to an address, Exim's routers
1265 are also used for &'address verification'&. Verification can be requested as
1266 one of the checks to be performed in an ACL for incoming messages, on both
1267 sender and recipient addresses, and it can be tested using the &%-bv%& and
1268 &%-bvs%& command line options.
1269
1270 When an address is being verified, the routers are run in &"verify mode"&. This
1271 does not affect the way the routers work, but it is a state that can be
1272 detected. By this means, a router can be skipped or made to behave differently
1273 when verifying. A common example is a configuration in which the first router
1274 sends all messages to a message-scanning program, unless they have been
1275 previously scanned. Thus, the first router accepts all addresses without any
1276 checking, making it useless for verifying. Normally, the &%no_verify%& option
1277 would be set for such a router, causing it to be skipped in verify mode.
1278
1279
1280
1281
1282 .section "Running an individual router" "SECTrunindrou"
1283 .cindex "router" "running details"
1284 .cindex "preconditions" "checking"
1285 .cindex "router" "result of running"
1286 As explained in the example above, a number of preconditions are checked before
1287 running a router. If any are not met, the router is skipped, and the address is
1288 passed to the next router. When all the preconditions on a router &'are'& met,
1289 the router is run. What happens next depends on the outcome, which is one of
1290 the following:
1291
1292 .ilist
1293 &'accept'&: The router accepts the address, and either assigns it to a
1294 transport, or generates one or more &"child"& addresses. Processing the
1295 original address ceases,
1296 .oindex "&%unseen%&"
1297 unless the &%unseen%& option is set on the router. This option
1298 can be used to set up multiple deliveries with different routing (for example,
1299 for keeping archive copies of messages). When &%unseen%& is set, the address is
1300 passed to the next router. Normally, however, an &'accept'& return marks the
1301 end of routing.
1302
1303 Any child addresses generated by the router are processed independently,
1304 starting with the first router by default. It is possible to change this by
1305 setting the &%redirect_router%& option to specify which router to start at for
1306 child addresses. Unlike &%pass_router%& (see below) the router specified by
1307 &%redirect_router%& may be anywhere in the router configuration.
1308 .next
1309 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1310 requests that the address be passed to another router. By default the address
1311 is passed to the next router, but this can be changed by setting the
1312 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1313 must be below the current router (to avoid loops).
1314 .next
1315 &'decline'&: The router declines to accept the address because it does not
1316 recognize it at all. By default, the address is passed to the next router, but
1317 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1318 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1319 &'decline'& into &'fail'&.
1320 .next
1321 &'fail'&: The router determines that the address should fail, and queues it for
1322 the generation of a bounce message. There is no further processing of the
1323 original address unless &%unseen%& is set on the router.
1324 .next
1325 &'defer'&: The router cannot handle the address at the present time. (A
1326 database may be offline, or a DNS lookup may have timed out.) No further
1327 processing of the address happens in this delivery attempt. It is tried again
1328 next time the message is considered for delivery.
1329 .next
1330 &'error'&: There is some error in the router (for example, a syntax error in
1331 its configuration). The action is as for defer.
1332 .endlist
1333
1334 If an address reaches the end of the routers without having been accepted by
1335 any of them, it is bounced as unrouteable. The default error message in this
1336 situation is &"unrouteable address"&, but you can set your own message by
1337 making use of the &%cannot_route_message%& option. This can be set for any
1338 router; the value from the last router that &"saw"& the address is used.
1339
1340 Sometimes while routing you want to fail a delivery when some conditions are
1341 met but others are not, instead of passing the address on for further routing.
1342 You can do this by having a second router that explicitly fails the delivery
1343 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1344 facility for this purpose.
1345
1346
1347 .section "Duplicate addresses" "SECID17"
1348 .cindex "case of local parts"
1349 .cindex "address duplicate, discarding"
1350 .cindex "duplicate addresses"
1351 Once routing is complete, Exim scans the addresses that are assigned to local
1352 and remote transports, and discards any duplicates that it finds. During this
1353 check, local parts are treated as case-sensitive. This happens only when
1354 actually delivering a message; when testing routers with &%-bt%&, all the
1355 routed addresses are shown.
1356
1357
1358
1359 .section "Router preconditions" "SECTrouprecon"
1360 .cindex "router" "preconditions, order of processing"
1361 .cindex "preconditions" "order of processing"
1362 The preconditions that are tested for each router are listed below, in the
1363 order in which they are tested. The individual configuration options are
1364 described in more detail in chapter &<<CHAProutergeneric>>&.
1365
1366 .ilist
1367 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1368 the local parts handled by the router may or must have certain prefixes and/or
1369 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1370 skipped. These conditions are tested first. When an affix is present, it is
1371 removed from the local part before further processing, including the evaluation
1372 of any other conditions.
1373 .next
1374 Routers can be designated for use only when not verifying an address, that is,
1375 only when routing it for delivery (or testing its delivery routing). If the
1376 &%verify%& option is set false, the router is skipped when Exim is verifying an
1377 address.
1378 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1379 &%verify_recipient%&, which independently control the use of the router for
1380 sender and recipient verification. You can set these options directly if
1381 you want a router to be used for only one type of verification.
1382 Note that cutthrough delivery is classed as a recipient verification for this purpose.
1383 .next
1384 If the &%address_test%& option is set false, the router is skipped when Exim is
1385 run with the &%-bt%& option to test an address routing. This can be helpful
1386 when the first router sends all new messages to a scanner of some sort; it
1387 makes it possible to use &%-bt%& to test subsequent delivery routing without
1388 having to simulate the effect of the scanner.
1389 .next
1390 Routers can be designated for use only when verifying an address, as
1391 opposed to routing it for delivery. The &%verify_only%& option controls this.
1392 Again, cutthrough delivery counts as a verification.
1393 .next
1394 Individual routers can be explicitly skipped when running the routers to
1395 check an address given in the SMTP EXPN command (see the &%expn%& option).
1396 .next
1397 If the &%domains%& option is set, the domain of the address must be in the set
1398 of domains that it defines.
1399 .next
1400 .vindex "&$local_part_prefix$&"
1401 .vindex "&$local_part$&"
1402 .vindex "&$local_part_suffix$&"
1403 If the &%local_parts%& option is set, the local part of the address must be in
1404 the set of local parts that it defines. If &%local_part_prefix%& or
1405 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1406 part before this check. If you want to do precondition tests on local parts
1407 that include affixes, you can do so by using a &%condition%& option (see below)
1408 that uses the variables &$local_part$&, &$local_part_prefix$&, and
1409 &$local_part_suffix$& as necessary.
1410 .next
1411 .vindex "&$local_user_uid$&"
1412 .vindex "&$local_user_gid$&"
1413 .vindex "&$home$&"
1414 If the &%check_local_user%& option is set, the local part must be the name of
1415 an account on the local host. If this check succeeds, the uid and gid of the
1416 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1417 user's home directory is placed in &$home$&; these values can be used in the
1418 remaining preconditions.
1419 .next
1420 If the &%router_home_directory%& option is set, it is expanded at this point,
1421 because it overrides the value of &$home$&. If this expansion were left till
1422 later, the value of &$home$& as set by &%check_local_user%& would be used in
1423 subsequent tests. Having two different values of &$home$& in the same router
1424 could lead to confusion.
1425 .next
1426 If the &%senders%& option is set, the envelope sender address must be in the
1427 set of addresses that it defines.
1428 .next
1429 If the &%require_files%& option is set, the existence or non-existence of
1430 specified files is tested.
1431 .next
1432 .cindex "customizing" "precondition"
1433 If the &%condition%& option is set, it is evaluated and tested. This option
1434 uses an expanded string to allow you to set up your own custom preconditions.
1435 Expanded strings are described in chapter &<<CHAPexpand>>&.
1436 .endlist
1437
1438
1439 Note that &%require_files%& comes near the end of the list, so you cannot use
1440 it to check for the existence of a file in which to lookup up a domain, local
1441 part, or sender. However, as these options are all expanded, you can use the
1442 &%exists%& expansion condition to make such tests within each condition. The
1443 &%require_files%& option is intended for checking files that the router may be
1444 going to use internally, or which are needed by a specific transport (for
1445 example, &_.procmailrc_&).
1446
1447
1448
1449 .section "Delivery in detail" "SECID18"
1450 .cindex "delivery" "in detail"
1451 When a message is to be delivered, the sequence of events is as follows:
1452
1453 .ilist
1454 If a system-wide filter file is specified, the message is passed to it. The
1455 filter may add recipients to the message, replace the recipients, discard the
1456 message, cause a new message to be generated, or cause the message delivery to
1457 fail. The format of the system filter file is the same as for Exim user filter
1458 files, described in the separate document entitled &'Exim's interfaces to mail
1459 filtering'&.
1460 .cindex "Sieve filter" "not available for system filter"
1461 (&*Note*&: Sieve cannot be used for system filter files.)
1462
1463 Some additional features are available in system filters &-- see chapter
1464 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1465 filter only once per delivery attempt, however many recipients it has. However,
1466 if there are several delivery attempts because one or more addresses could not
1467 be immediately delivered, the system filter is run each time. The filter
1468 condition &%first_delivery%& can be used to detect the first run of the system
1469 filter.
1470 .next
1471 Each recipient address is offered to each configured router in turn, subject to
1472 its preconditions, until one is able to handle it. If no router can handle the
1473 address, that is, if they all decline, the address is failed. Because routers
1474 can be targeted at particular domains, several locally handled domains can be
1475 processed entirely independently of each other.
1476 .next
1477 .cindex "routing" "loops in"
1478 .cindex "loop" "while routing"
1479 A router that accepts an address may assign it to a local or a remote
1480 transport. However, the transport is not run at this time. Instead, the address
1481 is placed on a list for the particular transport, which will be run later.
1482 Alternatively, the router may generate one or more new addresses (typically
1483 from alias, forward, or filter files). New addresses are fed back into this
1484 process from the top, but in order to avoid loops, a router ignores any address
1485 which has an identically-named ancestor that was processed by itself.
1486 .next
1487 When all the routing has been done, addresses that have been successfully
1488 handled are passed to their assigned transports. When local transports are
1489 doing real local deliveries, they handle only one address at a time, but if a
1490 local transport is being used as a pseudo-remote transport (for example, to
1491 collect batched SMTP messages for transmission by some other means) multiple
1492 addresses can be handled. Remote transports can always handle more than one
1493 address at a time, but can be configured not to do so, or to restrict multiple
1494 addresses to the same domain.
1495 .next
1496 Each local delivery to a file or a pipe runs in a separate process under a
1497 non-privileged uid, and these deliveries are run one at a time. Remote
1498 deliveries also run in separate processes, normally under a uid that is private
1499 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1500 run in parallel. The maximum number of simultaneous remote deliveries for any
1501 one message is set by the &%remote_max_parallel%& option.
1502 The order in which deliveries are done is not defined, except that all local
1503 deliveries happen before any remote deliveries.
1504 .next
1505 .cindex "queue runner"
1506 When it encounters a local delivery during a queue run, Exim checks its retry
1507 database to see if there has been a previous temporary delivery failure for the
1508 address before running the local transport. If there was a previous failure,
1509 Exim does not attempt a new delivery until the retry time for the address is
1510 reached. However, this happens only for delivery attempts that are part of a
1511 queue run. Local deliveries are always attempted when delivery immediately
1512 follows message reception, even if retry times are set for them. This makes for
1513 better behaviour if one particular message is causing problems (for example,
1514 causing quota overflow, or provoking an error in a filter file).
1515 .next
1516 .cindex "delivery" "retry in remote transports"
1517 Remote transports do their own retry handling, since an address may be
1518 deliverable to one of a number of hosts, each of which may have a different
1519 retry time. If there have been previous temporary failures and no host has
1520 reached its retry time, no delivery is attempted, whether in a queue run or
1521 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1522 .next
1523 If there were any permanent errors, a bounce message is returned to an
1524 appropriate address (the sender in the common case), with details of the error
1525 for each failing address. Exim can be configured to send copies of bounce
1526 messages to other addresses.
1527 .next
1528 .cindex "delivery" "deferral"
1529 If one or more addresses suffered a temporary failure, the message is left on
1530 the queue, to be tried again later. Delivery of these addresses is said to be
1531 &'deferred'&.
1532 .next
1533 When all the recipient addresses have either been delivered or bounced,
1534 handling of the message is complete. The spool files and message log are
1535 deleted, though the message log can optionally be preserved if required.
1536 .endlist
1537
1538
1539
1540
1541 .section "Retry mechanism" "SECID19"
1542 .cindex "delivery" "retry mechanism"
1543 .cindex "retry" "description of mechanism"
1544 .cindex "queue runner"
1545 Exim's mechanism for retrying messages that fail to get delivered at the first
1546 attempt is the queue runner process. You must either run an Exim daemon that
1547 uses the &%-q%& option with a time interval to start queue runners at regular
1548 intervals, or use some other means (such as &'cron'&) to start them. If you do
1549 not arrange for queue runners to be run, messages that fail temporarily at the
1550 first attempt will remain on your queue for ever. A queue runner process works
1551 its way through the queue, one message at a time, trying each delivery that has
1552 passed its retry time.
1553 You can run several queue runners at once.
1554
1555 Exim uses a set of configured rules to determine when next to retry the failing
1556 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1557 should give up trying to deliver to the address, at which point it generates a
1558 bounce message. If no retry rules are set for a particular host, address, and
1559 error combination, no retries are attempted, and temporary errors are treated
1560 as permanent.
1561
1562
1563
1564 .section "Temporary delivery failure" "SECID20"
1565 .cindex "delivery" "temporary failure"
1566 There are many reasons why a message may not be immediately deliverable to a
1567 particular address. Failure to connect to a remote machine (because it, or the
1568 connection to it, is down) is one of the most common. Temporary failures may be
1569 detected during routing as well as during the transport stage of delivery.
1570 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1571 is on a file system where the user is over quota. Exim can be configured to
1572 impose its own quotas on local mailboxes; where system quotas are set they will
1573 also apply.
1574
1575 If a host is unreachable for a period of time, a number of messages may be
1576 waiting for it by the time it recovers, and sending them in a single SMTP
1577 connection is clearly beneficial. Whenever a delivery to a remote host is
1578 deferred,
1579 .cindex "hints database" "deferred deliveries"
1580 Exim makes a note in its hints database, and whenever a successful
1581 SMTP delivery has happened, it looks to see if any other messages are waiting
1582 for the same host. If any are found, they are sent over the same SMTP
1583 connection, subject to a configuration limit as to the maximum number in any
1584 one connection.
1585
1586
1587
1588 .section "Permanent delivery failure" "SECID21"
1589 .cindex "delivery" "permanent failure"
1590 .cindex "bounce message" "when generated"
1591 When a message cannot be delivered to some or all of its intended recipients, a
1592 bounce message is generated. Temporary delivery failures turn into permanent
1593 errors when their timeout expires. All the addresses that fail in a given
1594 delivery attempt are listed in a single message. If the original message has
1595 many recipients, it is possible for some addresses to fail in one delivery
1596 attempt and others to fail subsequently, giving rise to more than one bounce
1597 message. The wording of bounce messages can be customized by the administrator.
1598 See chapter &<<CHAPemsgcust>>& for details.
1599
1600 .cindex "&'X-Failed-Recipients:'& header line"
1601 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1602 failed addresses, for the benefit of programs that try to analyse such messages
1603 automatically.
1604
1605 .cindex "bounce message" "recipient of"
1606 A bounce message is normally sent to the sender of the original message, as
1607 obtained from the message's envelope. For incoming SMTP messages, this is the
1608 address given in the MAIL command. However, when an address is expanded via a
1609 forward or alias file, an alternative address can be specified for delivery
1610 failures of the generated addresses. For a mailing list expansion (see section
1611 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1612 of the list.
1613
1614
1615
1616 .section "Failures to deliver bounce messages" "SECID22"
1617 .cindex "bounce message" "failure to deliver"
1618 If a bounce message (either locally generated or received from a remote host)
1619 itself suffers a permanent delivery failure, the message is left on the queue,
1620 but it is frozen, awaiting the attention of an administrator. There are options
1621 that can be used to make Exim discard such failed messages, or to keep them
1622 for only a short time (see &%timeout_frozen_after%& and
1623 &%ignore_bounce_errors_after%&).
1624
1625
1626
1627
1628
1629 . ////////////////////////////////////////////////////////////////////////////
1630 . ////////////////////////////////////////////////////////////////////////////
1631
1632 .chapter "Building and installing Exim" "CHID3"
1633 .scindex IIDbuex "building Exim"
1634
1635 .section "Unpacking" "SECID23"
1636 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1637 creates a directory with the name of the current release (for example,
1638 &_exim-&version()_&) into which the following files are placed:
1639
1640 .table2 140pt
1641 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1642 .irow &_CHANGES_& "contains a reference to where changes are &&&
1643 documented"
1644 .irow &_LICENCE_& "the GNU General Public Licence"
1645 .irow &_Makefile_& "top-level make file"
1646 .irow &_NOTICE_& "conditions for the use of Exim"
1647 .irow &_README_& "list of files, directories and simple build &&&
1648 instructions"
1649 .endtable
1650
1651 Other files whose names begin with &_README_& may also be present. The
1652 following subdirectories are created:
1653
1654 .table2 140pt
1655 .irow &_Local_& "an empty directory for local configuration files"
1656 .irow &_OS_& "OS-specific files"
1657 .irow &_doc_& "documentation files"
1658 .irow &_exim_monitor_& "source files for the Exim monitor"
1659 .irow &_scripts_& "scripts used in the build process"
1660 .irow &_src_& "remaining source files"
1661 .irow &_util_& "independent utilities"
1662 .endtable
1663
1664 The main utility programs are contained in the &_src_& directory, and are built
1665 with the Exim binary. The &_util_& directory contains a few optional scripts
1666 that may be useful to some sites.
1667
1668
1669 .section "Multiple machine architectures and operating systems" "SECID24"
1670 .cindex "building Exim" "multiple OS/architectures"
1671 The building process for Exim is arranged to make it easy to build binaries for
1672 a number of different architectures and operating systems from the same set of
1673 source files. Compilation does not take place in the &_src_& directory.
1674 Instead, a &'build directory'& is created for each architecture and operating
1675 system.
1676 .cindex "symbolic link" "to build directory"
1677 Symbolic links to the sources are installed in this directory, which is where
1678 the actual building takes place. In most cases, Exim can discover the machine
1679 architecture and operating system for itself, but the defaults can be
1680 overridden if necessary.
1681 .cindex compiler requirements
1682 .cindex compiler version
1683 A C99-capable compiler will be required for the build.
1684
1685
1686 .section "PCRE library" "SECTpcre"
1687 .cindex "PCRE library"
1688 Exim no longer has an embedded PCRE library as the vast majority of
1689 modern systems include PCRE as a system library, although you may need
1690 to install the PCRE or PCRE development package for your operating
1691 system. If your system has a normal PCRE installation the Exim build
1692 process will need no further configuration. If the library or the
1693 headers are in an unusual location you will need to either set the PCRE_LIBS
1694 and INCLUDE directives appropriately,
1695 or set PCRE_CONFIG=yes to use the installed &(pcre-config)& command.
1696 If your operating system has no
1697 PCRE support then you will need to obtain and build the current PCRE
1698 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
1699 More information on PCRE is available at &url(http://www.pcre.org/).
1700
1701 .section "DBM libraries" "SECTdb"
1702 .cindex "DBM libraries" "discussion of"
1703 .cindex "hints database" "DBM files used for"
1704 Even if you do not use any DBM files in your configuration, Exim still needs a
1705 DBM library in order to operate, because it uses indexed files for its hints
1706 databases. Unfortunately, there are a number of DBM libraries in existence, and
1707 different operating systems often have different ones installed.
1708
1709 .cindex "Solaris" "DBM library for"
1710 .cindex "IRIX, DBM library for"
1711 .cindex "BSD, DBM library for"
1712 .cindex "Linux, DBM library for"
1713 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1714 Linux distribution, the DBM configuration should happen automatically, and you
1715 may be able to ignore this section. Otherwise, you may have to learn more than
1716 you would like about DBM libraries from what follows.
1717
1718 .cindex "&'ndbm'& DBM library"
1719 Licensed versions of Unix normally contain a library of DBM functions operating
1720 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1721 versions of Unix seem to vary in what they contain as standard. In particular,
1722 some early versions of Linux have no default DBM library, and different
1723 distributors have chosen to bundle different libraries with their packaged
1724 versions. However, the more recent releases seem to have standardized on the
1725 Berkeley DB library.
1726
1727 Different DBM libraries have different conventions for naming the files they
1728 use. When a program opens a file called &_dbmfile_&, there are several
1729 possibilities:
1730
1731 .olist
1732 A traditional &'ndbm'& implementation, such as that supplied as part of
1733 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1734 .next
1735 .cindex "&'gdbm'& DBM library"
1736 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1737 compatibility interface it makes two different hard links to it with names
1738 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1739 file name is used unmodified.
1740 .next
1741 .cindex "Berkeley DB library"
1742 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1743 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1744 programmer exactly the same as the traditional &'ndbm'& implementation.
1745 .next
1746 If the Berkeley package is used in its native mode, it operates on a single
1747 file called &_dbmfile_&; the programmer's interface is somewhat different to
1748 the traditional &'ndbm'& interface.
1749 .next
1750 To complicate things further, there are several very different versions of the
1751 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1752 2.&'x'& and 3.&'x'& were current for a while, but the latest versions are now
1753 numbered 4.&'x'&. Maintenance of some of the earlier releases has ceased. All
1754 versions of Berkeley DB can be obtained from
1755 &url(http://www.sleepycat.com/).
1756 .next
1757 .cindex "&'tdb'& DBM library"
1758 Yet another DBM library, called &'tdb'&, is available from
1759 &url(http://download.sourceforge.net/tdb). It has its own interface, and also
1760 operates on a single file.
1761 .endlist
1762
1763 .cindex "USE_DB"
1764 .cindex "DBM libraries" "configuration for building"
1765 Exim and its utilities can be compiled to use any of these interfaces. In order
1766 to use any version of the Berkeley DB package in native mode, you must set
1767 USE_DB in an appropriate configuration file (typically
1768 &_Local/Makefile_&). For example:
1769 .code
1770 USE_DB=yes
1771 .endd
1772 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1773 error is diagnosed if you set more than one of these.
1774
1775 At the lowest level, the build-time configuration sets none of these options,
1776 thereby assuming an interface of type (1). However, some operating system
1777 configuration files (for example, those for the BSD operating systems and
1778 Linux) assume type (4) by setting USE_DB as their default, and the
1779 configuration files for Cygwin set USE_GDBM. Anything you set in
1780 &_Local/Makefile_&, however, overrides these system defaults.
1781
1782 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1783 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1784 in one of these lines:
1785 .code
1786 DBMLIB = -ldb
1787 DBMLIB = -ltdb
1788 .endd
1789 Settings like that will work if the DBM library is installed in the standard
1790 place. Sometimes it is not, and the library's header file may also not be in
1791 the default path. You may need to set INCLUDE to specify where the header
1792 file is, and to specify the path to the library more fully in DBMLIB, as in
1793 this example:
1794 .code
1795 INCLUDE=-I/usr/local/include/db-4.1
1796 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1797 .endd
1798 There is further detailed discussion about the various DBM libraries in the
1799 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1800
1801
1802
1803 .section "Pre-building configuration" "SECID25"
1804 .cindex "building Exim" "pre-building configuration"
1805 .cindex "configuration for building Exim"
1806 .cindex "&_Local/Makefile_&"
1807 .cindex "&_src/EDITME_&"
1808 Before building Exim, a local configuration file that specifies options
1809 independent of any operating system has to be created with the name
1810 &_Local/Makefile_&. A template for this file is supplied as the file
1811 &_src/EDITME_&, and it contains full descriptions of all the option settings
1812 therein. These descriptions are therefore not repeated here. If you are
1813 building Exim for the first time, the simplest thing to do is to copy
1814 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1815
1816 There are three settings that you must supply, because Exim will not build
1817 without them. They are the location of the run time configuration file
1818 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1819 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1820 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1821 a colon-separated list of file names; Exim uses the first of them that exists.
1822
1823 There are a few other parameters that can be specified either at build time or
1824 at run time, to enable the same binary to be used on a number of different
1825 machines. However, if the locations of Exim's spool directory and log file
1826 directory (if not within the spool directory) are fixed, it is recommended that
1827 you specify them in &_Local/Makefile_& instead of at run time, so that errors
1828 detected early in Exim's execution (such as a malformed configuration file) can
1829 be logged.
1830
1831 .cindex "content scanning" "specifying at build time"
1832 Exim's interfaces for calling virus and spam scanning software directly from
1833 access control lists are not compiled by default. If you want to include these
1834 facilities, you need to set
1835 .code
1836 WITH_CONTENT_SCAN=yes
1837 .endd
1838 in your &_Local/Makefile_&. For details of the facilities themselves, see
1839 chapter &<<CHAPexiscan>>&.
1840
1841
1842 .cindex "&_Local/eximon.conf_&"
1843 .cindex "&_exim_monitor/EDITME_&"
1844 If you are going to build the Exim monitor, a similar configuration process is
1845 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1846 your installation and saved under the name &_Local/eximon.conf_&. If you are
1847 happy with the default settings described in &_exim_monitor/EDITME_&,
1848 &_Local/eximon.conf_& can be empty, but it must exist.
1849
1850 This is all the configuration that is needed in straightforward cases for known
1851 operating systems. However, the building process is set up so that it is easy
1852 to override options that are set by default or by operating-system-specific
1853 configuration files, for example to change the name of the C compiler, which
1854 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1855 do this.
1856
1857
1858
1859 .section "Support for iconv()" "SECID26"
1860 .cindex "&[iconv()]& support"
1861 .cindex "RFC 2047"
1862 The contents of header lines in messages may be encoded according to the rules
1863 described RFC 2047. This makes it possible to transmit characters that are not
1864 in the ASCII character set, and to label them as being in a particular
1865 character set. When Exim is inspecting header lines by means of the &%$h_%&
1866 mechanism, it decodes them, and translates them into a specified character set
1867 (default is set at build time). The translation is possible only if the operating system
1868 supports the &[iconv()]& function.
1869
1870 However, some of the operating systems that supply &[iconv()]& do not support
1871 very many conversions. The GNU &%libiconv%& library (available from
1872 &url(http://www.gnu.org/software/libiconv/)) can be installed on such
1873 systems to remedy this deficiency, as well as on systems that do not supply
1874 &[iconv()]& at all. After installing &%libiconv%&, you should add
1875 .code
1876 HAVE_ICONV=yes
1877 .endd
1878 to your &_Local/Makefile_& and rebuild Exim.
1879
1880
1881
1882 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1883 .cindex "TLS" "including support for TLS"
1884 .cindex "encryption" "including support for"
1885 .cindex "SUPPORT_TLS"
1886 .cindex "OpenSSL" "building Exim with"
1887 .cindex "GnuTLS" "building Exim with"
1888 Exim can be built to support encrypted SMTP connections, using the STARTTLS
1889 command as per RFC 2487. It can also support legacy clients that expect to
1890 start a TLS session immediately on connection to a non-standard port (see the
1891 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1892 line option).
1893
1894 If you want to build Exim with TLS support, you must first install either the
1895 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1896 implementing SSL.
1897
1898 If OpenSSL is installed, you should set
1899 .code
1900 SUPPORT_TLS=yes
1901 TLS_LIBS=-lssl -lcrypto
1902 .endd
1903 in &_Local/Makefile_&. You may also need to specify the locations of the
1904 OpenSSL library and include files. For example:
1905 .code
1906 SUPPORT_TLS=yes
1907 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1908 TLS_INCLUDE=-I/usr/local/openssl/include/
1909 .endd
1910 .cindex "pkg-config" "OpenSSL"
1911 If you have &'pkg-config'& available, then instead you can just use:
1912 .code
1913 SUPPORT_TLS=yes
1914 USE_OPENSSL_PC=openssl
1915 .endd
1916 .cindex "USE_GNUTLS"
1917 If GnuTLS is installed, you should set
1918 .code
1919 SUPPORT_TLS=yes
1920 USE_GNUTLS=yes
1921 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1922 .endd
1923 in &_Local/Makefile_&, and again you may need to specify the locations of the
1924 library and include files. For example:
1925 .code
1926 SUPPORT_TLS=yes
1927 USE_GNUTLS=yes
1928 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1929 TLS_INCLUDE=-I/usr/gnu/include
1930 .endd
1931 .cindex "pkg-config" "GnuTLS"
1932 If you have &'pkg-config'& available, then instead you can just use:
1933 .code
1934 SUPPORT_TLS=yes
1935 USE_GNUTLS=yes
1936 USE_GNUTLS_PC=gnutls
1937 .endd
1938
1939 You do not need to set TLS_INCLUDE if the relevant directory is already
1940 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1941 given in chapter &<<CHAPTLS>>&.
1942
1943
1944
1945
1946 .section "Use of tcpwrappers" "SECID27"
1947
1948 .cindex "tcpwrappers, building Exim to support"
1949 .cindex "USE_TCP_WRAPPERS"
1950 .cindex "TCP_WRAPPERS_DAEMON_NAME"
1951 .cindex "tcp_wrappers_daemon_name"
1952 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
1953 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
1954 alternative to Exim's own checking facilities for installations that are
1955 already making use of &'tcpwrappers'& for other purposes. To do this, you
1956 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
1957 &_tcpd.h_& to be available at compile time, and also ensure that the library
1958 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
1959 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
1960 you might have
1961 .code
1962 USE_TCP_WRAPPERS=yes
1963 CFLAGS=-O -I/usr/local/include
1964 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
1965 .endd
1966 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
1967 files is &"exim"&. For example, the line
1968 .code
1969 exim : LOCAL 192.168.1. .friendly.domain.example
1970 .endd
1971 in your &_/etc/hosts.allow_& file allows connections from the local host, from
1972 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
1973 All other connections are denied. The daemon name used by &'tcpwrappers'&
1974 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
1975 &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
1976 configure file. Consult the &'tcpwrappers'& documentation for
1977 further details.
1978
1979
1980 .section "Including support for IPv6" "SECID28"
1981 .cindex "IPv6" "including support for"
1982 Exim contains code for use on systems that have IPv6 support. Setting
1983 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
1984 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
1985 where the IPv6 support is not fully integrated into the normal include and
1986 library files.
1987
1988 Two different types of DNS record for handling IPv6 addresses have been
1989 defined. AAAA records (analogous to A records for IPv4) are in use, and are
1990 currently seen as the mainstream. Another record type called A6 was proposed
1991 as better than AAAA because it had more flexibility. However, it was felt to be
1992 over-complex, and its status was reduced to &"experimental"&.
1993 Exim used to
1994 have a compile option for including A6 record support but this has now been
1995 withdrawn.
1996
1997
1998
1999 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
2000 .cindex "lookup modules"
2001 .cindex "dynamic modules"
2002 .cindex ".so building"
2003 On some platforms, Exim supports not compiling all lookup types directly into
2004 the main binary, instead putting some into external modules which can be loaded
2005 on demand.
2006 This permits packagers to build Exim with support for lookups with extensive
2007 library dependencies without requiring all users to install all of those
2008 dependencies.
2009 Most, but not all, lookup types can be built this way.
2010
2011 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2012 installed; Exim will only load modules from that directory, as a security
2013 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2014 for your OS; see &_OS/Makefile-Linux_& for an example.
2015 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2016 see &_src/EDITME_& for details.
2017
2018 Then, for each module to be loaded dynamically, define the relevant
2019 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2020 For example, this will build in lsearch but load sqlite and mysql support
2021 on demand:
2022 .code
2023 LOOKUP_LSEARCH=yes
2024 LOOKUP_SQLITE=2
2025 LOOKUP_MYSQL=2
2026 .endd
2027
2028
2029 .section "The building process" "SECID29"
2030 .cindex "build directory"
2031 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2032 created, run &'make'& at the top level. It determines the architecture and
2033 operating system types, and creates a build directory if one does not exist.
2034 For example, on a Sun system running Solaris 8, the directory
2035 &_build-SunOS5-5.8-sparc_& is created.
2036 .cindex "symbolic link" "to source files"
2037 Symbolic links to relevant source files are installed in the build directory.
2038
2039 If this is the first time &'make'& has been run, it calls a script that builds
2040 a make file inside the build directory, using the configuration files from the
2041 &_Local_& directory. The new make file is then passed to another instance of
2042 &'make'&. This does the real work, building a number of utility scripts, and
2043 then compiling and linking the binaries for the Exim monitor (if configured), a
2044 number of utility programs, and finally Exim itself. The command &`make
2045 makefile`& can be used to force a rebuild of the make file in the build
2046 directory, should this ever be necessary.
2047
2048 If you have problems building Exim, check for any comments there may be in the
2049 &_README_& file concerning your operating system, and also take a look at the
2050 FAQ, where some common problems are covered.
2051
2052
2053
2054 .section 'Output from &"make"&' "SECID283"
2055 The output produced by the &'make'& process for compile lines is often very
2056 unreadable, because these lines can be very long. For this reason, the normal
2057 output is suppressed by default, and instead output similar to that which
2058 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2059 each module that is being compiled or linked. However, it is still possible to
2060 get the full output, by calling &'make'& like this:
2061 .code
2062 FULLECHO='' make -e
2063 .endd
2064 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2065 command reflection in &'make'&. When you ask for the full output, it is
2066 given in addition to the short output.
2067
2068
2069
2070 .section "Overriding build-time options for Exim" "SECToverride"
2071 .cindex "build-time options, overriding"
2072 The main make file that is created at the beginning of the building process
2073 consists of the concatenation of a number of files which set configuration
2074 values, followed by a fixed set of &'make'& instructions. If a value is set
2075 more than once, the last setting overrides any previous ones. This provides a
2076 convenient way of overriding defaults. The files that are concatenated are, in
2077 order:
2078 .display
2079 &_OS/Makefile-Default_&
2080 &_OS/Makefile-_&<&'ostype'&>
2081 &_Local/Makefile_&
2082 &_Local/Makefile-_&<&'ostype'&>
2083 &_Local/Makefile-_&<&'archtype'&>
2084 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2085 &_OS/Makefile-Base_&
2086 .endd
2087 .cindex "&_Local/Makefile_&"
2088 .cindex "building Exim" "operating system type"
2089 .cindex "building Exim" "architecture type"
2090 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2091 architecture type. &_Local/Makefile_& is required to exist, and the building
2092 process fails if it is absent. The other three &_Local_& files are optional,
2093 and are often not needed.
2094
2095 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2096 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2097 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2098 values are used, thereby providing a means of forcing particular settings.
2099 Otherwise, the scripts try to get values from the &%uname%& command. If this
2100 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2101 of &'ad hoc'& transformations are then applied, to produce the standard names
2102 that Exim expects. You can run these scripts directly from the shell in order
2103 to find out what values are being used on your system.
2104
2105
2106 &_OS/Makefile-Default_& contains comments about the variables that are set
2107 therein. Some (but not all) are mentioned below. If there is something that
2108 needs changing, review the contents of this file and the contents of the make
2109 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2110 default values are.
2111
2112
2113 .cindex "building Exim" "overriding default settings"
2114 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2115 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2116 need to change the original files. Instead, you should make the changes by
2117 putting the new values in an appropriate &_Local_& file. For example,
2118 .cindex "Tru64-Unix build-time settings"
2119 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2120 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2121 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2122 called with the option &%-std1%&, to make it recognize some of the features of
2123 Standard C that Exim uses. (Most other compilers recognize Standard C by
2124 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2125 containing the lines
2126 .code
2127 CC=cc
2128 CFLAGS=-std1
2129 .endd
2130 If you are compiling for just one operating system, it may be easier to put
2131 these lines directly into &_Local/Makefile_&.
2132
2133 Keeping all your local configuration settings separate from the distributed
2134 files makes it easy to transfer them to new versions of Exim simply by copying
2135 the contents of the &_Local_& directory.
2136
2137
2138 .cindex "NIS lookup type" "including support for"
2139 .cindex "NIS+ lookup type" "including support for"
2140 .cindex "LDAP" "including support for"
2141 .cindex "lookup" "inclusion in binary"
2142 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2143 lookup, but not all systems have these components installed, so the default is
2144 not to include the relevant code in the binary. All the different kinds of file
2145 and database lookup that Exim supports are implemented as separate code modules
2146 which are included only if the relevant compile-time options are set. In the
2147 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2148 .code
2149 LOOKUP_LDAP=yes
2150 LOOKUP_NIS=yes
2151 LOOKUP_NISPLUS=yes
2152 .endd
2153 and similar settings apply to the other lookup types. They are all listed in
2154 &_src/EDITME_&. In many cases the relevant include files and interface
2155 libraries need to be installed before compiling Exim.
2156 .cindex "cdb" "including support for"
2157 However, there are some optional lookup types (such as cdb) for which
2158 the code is entirely contained within Exim, and no external include
2159 files or libraries are required. When a lookup type is not included in the
2160 binary, attempts to configure Exim to use it cause run time configuration
2161 errors.
2162
2163 .cindex "pkg-config" "lookups"
2164 .cindex "pkg-config" "authenticators"
2165 Many systems now use a tool called &'pkg-config'& to encapsulate information
2166 about how to compile against a library; Exim has some initial support for
2167 being able to use pkg-config for lookups and authenticators. For any given
2168 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2169 variable with the &`_PC`& suffix in the name and assign as the value the
2170 name of the package to be queried. The results of querying via the
2171 &'pkg-config'& command will be added to the appropriate Makefile variables
2172 with &`+=`& directives, so your version of &'make'& will need to support that
2173 syntax. For instance:
2174 .code
2175 LOOKUP_SQLITE=yes
2176 LOOKUP_SQLITE_PC=sqlite3
2177 AUTH_GSASL=yes
2178 AUTH_GSASL_PC=libgsasl
2179 AUTH_HEIMDAL_GSSAPI=yes
2180 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2181 .endd
2182
2183 .cindex "Perl" "including support for"
2184 Exim can be linked with an embedded Perl interpreter, allowing Perl
2185 subroutines to be called during string expansion. To enable this facility,
2186 .code
2187 EXIM_PERL=perl.o
2188 .endd
2189 must be defined in &_Local/Makefile_&. Details of this facility are given in
2190 chapter &<<CHAPperl>>&.
2191
2192 .cindex "X11 libraries, location of"
2193 The location of the X11 libraries is something that varies a lot between
2194 operating systems, and there may be different versions of X11 to cope
2195 with. Exim itself makes no use of X11, but if you are compiling the Exim
2196 monitor, the X11 libraries must be available.
2197 The following three variables are set in &_OS/Makefile-Default_&:
2198 .code
2199 X11=/usr/X11R6
2200 XINCLUDE=-I$(X11)/include
2201 XLFLAGS=-L$(X11)/lib
2202 .endd
2203 These are overridden in some of the operating-system configuration files. For
2204 example, in &_OS/Makefile-SunOS5_& there is
2205 .code
2206 X11=/usr/openwin
2207 XINCLUDE=-I$(X11)/include
2208 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2209 .endd
2210 If you need to override the default setting for your operating system, place a
2211 definition of all three of these variables into your
2212 &_Local/Makefile-<ostype>_& file.
2213
2214 .cindex "EXTRALIBS"
2215 If you need to add any extra libraries to the link steps, these can be put in a
2216 variable called EXTRALIBS, which appears in all the link commands, but by
2217 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2218 command for linking the main Exim binary, and not for any associated utilities.
2219
2220 .cindex "DBM libraries" "configuration for building"
2221 There is also DBMLIB, which appears in the link commands for binaries that
2222 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2223 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2224 binary, and which can be used, for example, to include additional X11
2225 libraries.
2226
2227 .cindex "configuration file" "editing"
2228 The make file copes with rebuilding Exim correctly if any of the configuration
2229 files are edited. However, if an optional configuration file is deleted, it is
2230 necessary to touch the associated non-optional file (that is,
2231 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2232
2233
2234 .section "OS-specific header files" "SECID30"
2235 .cindex "&_os.h_&"
2236 .cindex "building Exim" "OS-specific C header files"
2237 The &_OS_& directory contains a number of files with names of the form
2238 &_os.h-<ostype>_&. These are system-specific C header files that should not
2239 normally need to be changed. There is a list of macro settings that are
2240 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2241 are porting Exim to a new operating system.
2242
2243
2244
2245 .section "Overriding build-time options for the monitor" "SECID31"
2246 .cindex "building Eximon"
2247 A similar process is used for overriding things when building the Exim monitor,
2248 where the files that are involved are
2249 .display
2250 &_OS/eximon.conf-Default_&
2251 &_OS/eximon.conf-_&<&'ostype'&>
2252 &_Local/eximon.conf_&
2253 &_Local/eximon.conf-_&<&'ostype'&>
2254 &_Local/eximon.conf-_&<&'archtype'&>
2255 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2256 .endd
2257 .cindex "&_Local/eximon.conf_&"
2258 As with Exim itself, the final three files need not exist, and in this case the
2259 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2260 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2261 variables of the same name, preceded by EXIMON_. For example, setting
2262 EXIMON_LOG_DEPTH in the environment overrides the value of
2263 LOG_DEPTH at run time.
2264 .ecindex IIDbuex
2265
2266
2267 .section "Installing Exim binaries and scripts" "SECID32"
2268 .cindex "installing Exim"
2269 .cindex "BIN_DIRECTORY"
2270 The command &`make install`& runs the &(exim_install)& script with no
2271 arguments. The script copies binaries and utility scripts into the directory
2272 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2273 .cindex "setuid" "installing Exim with"
2274 The install script copies files only if they are newer than the files they are
2275 going to replace. The Exim binary is required to be owned by root and have the
2276 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2277 install`& as root so that it can set up the Exim binary in this way. However, in
2278 some special situations (for example, if a host is doing no local deliveries)
2279 it may be possible to run Exim without making the binary setuid root (see
2280 chapter &<<CHAPsecurity>>& for details).
2281
2282 .cindex "CONFIGURE_FILE"
2283 Exim's run time configuration file is named by the CONFIGURE_FILE setting
2284 in &_Local/Makefile_&. If this names a single file, and the file does not
2285 exist, the default configuration file &_src/configure.default_& is copied there
2286 by the installation script. If a run time configuration file already exists, it
2287 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2288 alternative files, no default is installed.
2289
2290 .cindex "system aliases file"
2291 .cindex "&_/etc/aliases_&"
2292 One change is made to the default configuration file when it is installed: the
2293 default configuration contains a router that references a system aliases file.
2294 The path to this file is set to the value specified by
2295 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2296 If the system aliases file does not exist, the installation script creates it,
2297 and outputs a comment to the user.
2298
2299 The created file contains no aliases, but it does contain comments about the
2300 aliases a site should normally have. Mail aliases have traditionally been
2301 kept in &_/etc/aliases_&. However, some operating systems are now using
2302 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2303 Exim's configuration if necessary.
2304
2305 The default configuration uses the local host's name as the only local domain,
2306 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2307 running as the local user. System aliases and &_.forward_& files in users' home
2308 directories are supported, but no NIS or NIS+ support is configured. Domains
2309 other than the name of the local host are routed using the DNS, with delivery
2310 over SMTP.
2311
2312 It is possible to install Exim for special purposes (such as building a binary
2313 distribution) in a private part of the file system. You can do this by a
2314 command such as
2315 .code
2316 make DESTDIR=/some/directory/ install
2317 .endd
2318 This has the effect of pre-pending the specified directory to all the file
2319 paths, except the name of the system aliases file that appears in the default
2320 configuration. (If a default alias file is created, its name &'is'& modified.)
2321 For backwards compatibility, ROOT is used if DESTDIR is not set,
2322 but this usage is deprecated.
2323
2324 .cindex "installing Exim" "what is not installed"
2325 Running &'make install'& does not copy the Exim 4 conversion script
2326 &'convert4r4'&. You will probably run this only once if you are
2327 upgrading from Exim 3. None of the documentation files in the &_doc_&
2328 directory are copied, except for the info files when you have set
2329 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2330
2331 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2332 to their names. The Exim binary itself, however, is handled differently. It is
2333 installed under a name that includes the version number and the compile number,
2334 for example &_exim-&version()-1_&. The script then arranges for a symbolic link
2335 called &_exim_& to point to the binary. If you are updating a previous version
2336 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2337 from the directory (as seen by other processes).
2338
2339 .cindex "installing Exim" "testing the script"
2340 If you want to see what the &'make install'& will do before running it for
2341 real, you can pass the &%-n%& option to the installation script by this
2342 command:
2343 .code
2344 make INSTALL_ARG=-n install
2345 .endd
2346 The contents of the variable INSTALL_ARG are passed to the installation
2347 script. You do not need to be root to run this test. Alternatively, you can run
2348 the installation script directly, but this must be from within the build
2349 directory. For example, from the top-level Exim directory you could use this
2350 command:
2351 .code
2352 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2353 .endd
2354 .cindex "installing Exim" "install script options"
2355 There are two other options that can be supplied to the installation script.
2356
2357 .ilist
2358 &%-no_chown%& bypasses the call to change the owner of the installed binary
2359 to root, and the call to make it a setuid binary.
2360 .next
2361 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2362 installed binary.
2363 .endlist
2364
2365 INSTALL_ARG can be used to pass these options to the script. For example:
2366 .code
2367 make INSTALL_ARG=-no_symlink install
2368 .endd
2369 The installation script can also be given arguments specifying which files are
2370 to be copied. For example, to install just the Exim binary, and nothing else,
2371 without creating the symbolic link, you could use:
2372 .code
2373 make INSTALL_ARG='-no_symlink exim' install
2374 .endd
2375
2376
2377
2378 .section "Installing info documentation" "SECTinsinfdoc"
2379 .cindex "installing Exim" "&'info'& documentation"
2380 Not all systems use the GNU &'info'& system for documentation, and for this
2381 reason, the Texinfo source of Exim's documentation is not included in the main
2382 distribution. Instead it is available separately from the ftp site (see section
2383 &<<SECTavail>>&).
2384
2385 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2386 source of the documentation is found in the source tree, running &`make
2387 install`& automatically builds the info files and installs them.
2388
2389
2390
2391 .section "Setting up the spool directory" "SECID33"
2392 .cindex "spool directory" "creating"
2393 When it starts up, Exim tries to create its spool directory if it does not
2394 exist. The Exim uid and gid are used for the owner and group of the spool
2395 directory. Sub-directories are automatically created in the spool directory as
2396 necessary.
2397
2398
2399
2400
2401 .section "Testing" "SECID34"
2402 .cindex "testing" "installation"
2403 Having installed Exim, you can check that the run time configuration file is
2404 syntactically valid by running the following command, which assumes that the
2405 Exim binary directory is within your PATH environment variable:
2406 .code
2407 exim -bV
2408 .endd
2409 If there are any errors in the configuration file, Exim outputs error messages.
2410 Otherwise it outputs the version number and build date,
2411 the DBM library that is being used, and information about which drivers and
2412 other optional code modules are included in the binary.
2413 Some simple routing tests can be done by using the address testing option. For
2414 example,
2415 .display
2416 &`exim -bt`& <&'local username'&>
2417 .endd
2418 should verify that it recognizes a local mailbox, and
2419 .display
2420 &`exim -bt`& <&'remote address'&>
2421 .endd
2422 a remote one. Then try getting it to deliver mail, both locally and remotely.
2423 This can be done by passing messages directly to Exim, without going through a
2424 user agent. For example:
2425 .code
2426 exim -v postmaster@your.domain.example
2427 From: user@your.domain.example
2428 To: postmaster@your.domain.example
2429 Subject: Testing Exim
2430
2431 This is a test message.
2432 ^D
2433 .endd
2434 The &%-v%& option causes Exim to output some verification of what it is doing.
2435 In this case you should see copies of three log lines, one for the message's
2436 arrival, one for its delivery, and one containing &"Completed"&.
2437
2438 .cindex "delivery" "problems with"
2439 If you encounter problems, look at Exim's log files (&'mainlog'& and
2440 &'paniclog'&) to see if there is any relevant information there. Another source
2441 of information is running Exim with debugging turned on, by specifying the
2442 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2443 with debugging turned on by a command of the form
2444 .display
2445 &`exim -d -M`& <&'exim-message-id'&>
2446 .endd
2447 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2448 produces rather a lot of output, but you can cut this down to specific areas.
2449 For example, if you use &%-d-all+route%& only the debugging information
2450 relevant to routing is included. (See the &%-d%& option in chapter
2451 &<<CHAPcommandline>>& for more details.)
2452
2453 .cindex '&"sticky"& bit'
2454 .cindex "lock files"
2455 One specific problem that has shown up on some sites is the inability to do
2456 local deliveries into a shared mailbox directory, because it does not have the
2457 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2458 writing to a mailbox file, and if it cannot create the lock file, the delivery
2459 is deferred. You can get round this either by setting the &"sticky bit"& on the
2460 directory, or by setting a specific group for local deliveries and allowing
2461 that group to create files in the directory (see the comments above the
2462 &(local_delivery)& transport in the default configuration file). Another
2463 approach is to configure Exim not to use lock files, but just to rely on
2464 &[fcntl()]& locking instead. However, you should do this only if all user
2465 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2466 see chapter &<<CHAPappendfile>>&.
2467
2468 One thing that cannot be tested on a system that is already running an MTA is
2469 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2470 &%-oX%& option can be used to run an Exim daemon that listens on some other
2471 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2472 &'exim_checkaccess'& utility can be used to check out policy controls on
2473 incoming SMTP mail.
2474
2475 Testing a new version on a system that is already running Exim can most easily
2476 be done by building a binary with a different CONFIGURE_FILE setting. From
2477 within the run time configuration, all other file and directory names
2478 that Exim uses can be altered, in order to keep it entirely clear of the
2479 production version.
2480
2481
2482 .section "Replacing another MTA with Exim" "SECID35"
2483 .cindex "replacing another MTA"
2484 Building and installing Exim for the first time does not of itself put it in
2485 general use. The name by which the system's MTA is called by mail user agents
2486 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2487 operating system), and it is necessary to make this name point to the &'exim'&
2488 binary in order to get the user agents to pass messages to Exim. This is
2489 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2490 or &_/usr/lib/sendmail_&
2491 .cindex "symbolic link" "to &'exim'& binary"
2492 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2493 privilege and executable status from the old MTA. It is then necessary to stop
2494 and restart the mailer daemon, if one is running.
2495
2496 .cindex "FreeBSD, MTA indirection"
2497 .cindex "&_/etc/mail/mailer.conf_&"
2498 Some operating systems have introduced alternative ways of switching MTAs. For
2499 example, if you are running FreeBSD, you need to edit the file
2500 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2501 described. A typical example of the contents of this file for running Exim is
2502 as follows:
2503 .code
2504 sendmail /usr/exim/bin/exim
2505 send-mail /usr/exim/bin/exim
2506 mailq /usr/exim/bin/exim -bp
2507 newaliases /usr/bin/true
2508 .endd
2509 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2510 your Exim installation is &"live"&. Check it by sending a message from your
2511 favourite user agent.
2512
2513 You should consider what to tell your users about the change of MTA. Exim may
2514 have different capabilities to what was previously running, and there are
2515 various operational differences such as the text of messages produced by
2516 command line options and in bounce messages. If you allow your users to make
2517 use of Exim's filtering capabilities, you should make the document entitled
2518 &'Exim's interface to mail filtering'& available to them.
2519
2520
2521
2522 .section "Upgrading Exim" "SECID36"
2523 .cindex "upgrading Exim"
2524 If you are already running Exim on your host, building and installing a new
2525 version automatically makes it available to MUAs, or any other programs that
2526 call the MTA directly. However, if you are running an Exim daemon, you do need
2527 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2528 new binary. You do not need to stop processing mail in order to install a new
2529 version of Exim. The install script does not modify an existing runtime
2530 configuration file.
2531
2532
2533
2534
2535 .section "Stopping the Exim daemon on Solaris" "SECID37"
2536 .cindex "Solaris" "stopping Exim on"
2537 The standard command for stopping the mailer daemon on Solaris is
2538 .code
2539 /etc/init.d/sendmail stop
2540 .endd
2541 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2542 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2543 for the text &"sendmail"&; this is not present because the actual program name
2544 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2545 solution is to replace the line that finds the process id with something like
2546 .code
2547 pid=`cat /var/spool/exim/exim-daemon.pid`
2548 .endd
2549 to obtain the daemon's pid directly from the file that Exim saves it in.
2550
2551 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2552 still be received from local processes, and if automatic delivery is configured
2553 (the normal case), deliveries will still occur.
2554
2555
2556
2557
2558 . ////////////////////////////////////////////////////////////////////////////
2559 . ////////////////////////////////////////////////////////////////////////////
2560
2561 .chapter "The Exim command line" "CHAPcommandline"
2562 .scindex IIDclo1 "command line" "options"
2563 .scindex IIDclo2 "options" "command line"
2564 Exim's command line takes the standard Unix form of a sequence of options,
2565 each starting with a hyphen character, followed by a number of arguments. The
2566 options are compatible with the main options of Sendmail, and there are also
2567 some additional options, some of which are compatible with Smail 3. Certain
2568 combinations of options do not make sense, and provoke an error if used.
2569 The form of the arguments depends on which options are set.
2570
2571
2572 .section "Setting options by program name" "SECID38"
2573 .cindex "&'mailq'&"
2574 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2575 were present before any other options.
2576 The &%-bp%& option requests a listing of the contents of the mail queue on the
2577 standard output.
2578 This feature is for compatibility with some systems that contain a command of
2579 that name in one of the standard libraries, symbolically linked to
2580 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2581
2582 .cindex "&'rsmtp'&"
2583 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2584 were present before any other options, for compatibility with Smail. The
2585 &%-bS%& option is used for reading in a number of messages in batched SMTP
2586 format.
2587
2588 .cindex "&'rmail'&"
2589 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2590 &%-oee%& options were present before any other options, for compatibility with
2591 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2592
2593 .cindex "&'runq'&"
2594 .cindex "queue runner"
2595 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2596 were present before any other options, for compatibility with Smail. The &%-q%&
2597 option causes a single queue runner process to be started.
2598
2599 .cindex "&'newaliases'&"
2600 .cindex "alias file" "building"
2601 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2602 If Exim is called under the name &'newaliases'& it behaves as if the option
2603 &%-bi%& were present before any other options, for compatibility with Sendmail.
2604 This option is used for rebuilding Sendmail's alias file. Exim does not have
2605 the concept of a single alias file, but can be configured to run a given
2606 command if called with the &%-bi%& option.
2607
2608
2609 .section "Trusted and admin users" "SECTtrustedadmin"
2610 Some Exim options are available only to &'trusted users'& and others are
2611 available only to &'admin users'&. In the description below, the phrases &"Exim
2612 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2613 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2614 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2615
2616 .ilist
2617 .cindex "trusted users" "definition of"
2618 .cindex "user" "trusted definition of"
2619 The trusted users are root, the Exim user, any user listed in the
2620 &%trusted_users%& configuration option, and any user whose current group or any
2621 supplementary group is one of those listed in the &%trusted_groups%&
2622 configuration option. Note that the Exim group is not automatically trusted.
2623
2624 .cindex '&"From"& line'
2625 .cindex "envelope sender"
2626 Trusted users are always permitted to use the &%-f%& option or a leading
2627 &"From&~"& line to specify the envelope sender of a message that is passed to
2628 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2629 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2630 users to set envelope senders.
2631
2632 .cindex "&'From:'& header line"
2633 .cindex "&'Sender:'& header line"
2634 .cindex "header lines" "From:"
2635 .cindex "header lines" "Sender:"
2636 For a trusted user, there is never any check on the contents of the &'From:'&
2637 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2638 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2639
2640 Trusted users may also specify a host name, host address, interface address,
2641 protocol name, ident value, and authentication data when submitting a message
2642 locally. Thus, they are able to insert messages into Exim's queue locally that
2643 have the characteristics of messages received from a remote host. Untrusted
2644 users may in some circumstances use &%-f%&, but can never set the other values
2645 that are available to trusted users.
2646 .next
2647 .cindex "user" "admin definition of"
2648 .cindex "admin user" "definition of"
2649 The admin users are root, the Exim user, and any user that is a member of the
2650 Exim group or of any group listed in the &%admin_groups%& configuration option.
2651 The current group does not have to be one of these groups.
2652
2653 Admin users are permitted to list the queue, and to carry out certain
2654 operations on messages, for example, to force delivery failures. It is also
2655 necessary to be an admin user in order to see the full information provided by
2656 the Exim monitor, and full debugging output.
2657
2658 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2659 Exim to attempt delivery of messages on its queue is restricted to admin users.
2660 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2661 option false (that is, specifying &%no_prod_requires_admin%&).
2662
2663 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2664 is restricted to admin users unless &%queue_list_requires_admin%& is set
2665 false.
2666 .endlist
2667
2668
2669 &*Warning*&: If you configure your system so that admin users are able to
2670 edit Exim's configuration file, you are giving those users an easy way of
2671 getting root. There is further discussion of this issue at the start of chapter
2672 &<<CHAPconf>>&.
2673
2674
2675
2676
2677 .section "Command line options" "SECID39"
2678 Exim's command line options are described in alphabetical order below. If none
2679 of the options that specifies a specific action (such as starting the daemon or
2680 a queue runner, or testing an address, or receiving a message in a specific
2681 format, or listing the queue) are present, and there is at least one argument
2682 on the command line, &%-bm%& (accept a local message on the standard input,
2683 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2684 outputs a brief message about itself and exits.
2685
2686 . ////////////////////////////////////////////////////////////////////////////
2687 . Insert a stylized XML comment here, to identify the start of the command line
2688 . options. This is for the benefit of the Perl script that automatically
2689 . creates a man page for the options.
2690 . ////////////////////////////////////////////////////////////////////////////
2691
2692 .literal xml
2693 <!-- === Start of command line options === -->
2694 .literal off
2695
2696
2697 .vlist
2698 .vitem &%--%&
2699 .oindex "--"
2700 .cindex "options" "command line; terminating"
2701 This is a pseudo-option whose only purpose is to terminate the options and
2702 therefore to cause subsequent command line items to be treated as arguments
2703 rather than options, even if they begin with hyphens.
2704
2705 .vitem &%--help%&
2706 .oindex "&%--help%&"
2707 This option causes Exim to output a few sentences stating what it is.
2708 The same output is generated if the Exim binary is called with no options and
2709 no arguments.
2710
2711 .vitem &%--version%&
2712 .oindex "&%--version%&"
2713 This option is an alias for &%-bV%& and causes version information to be
2714 displayed.
2715
2716 .vitem &%-Ac%& &&&
2717 &%-Am%&
2718 .oindex "&%-Ac%&"
2719 .oindex "&%-Am%&"
2720 These options are used by Sendmail for selecting configuration files and are
2721 ignored by Exim.
2722
2723 .vitem &%-B%&<&'type'&>
2724 .oindex "&%-B%&"
2725 .cindex "8-bit characters"
2726 .cindex "Sendmail compatibility" "8-bit characters"
2727 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2728 clean; it ignores this option.
2729
2730 .vitem &%-bd%&
2731 .oindex "&%-bd%&"
2732 .cindex "daemon"
2733 .cindex "SMTP" "listener"
2734 .cindex "queue runner"
2735 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2736 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2737 that the daemon should also initiate periodic queue runs.
2738
2739 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2740 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2741 disconnect from the controlling terminal. When running this way, it can be
2742 stopped by pressing ctrl-C.
2743
2744 By default, Exim listens for incoming connections to the standard SMTP port on
2745 all the host's running interfaces. However, it is possible to listen on other
2746 ports, on multiple ports, and only on specific interfaces. Chapter
2747 &<<CHAPinterfaces>>& contains a description of the options that control this.
2748
2749 When a listening daemon
2750 .cindex "daemon" "process id (pid)"
2751 .cindex "pid (process id)" "of daemon"
2752 is started without the use of &%-oX%& (that is, without overriding the normal
2753 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2754 in Exim's spool directory. This location can be overridden by setting
2755 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2756 running as root.
2757
2758 When &%-oX%& is used on the command line to start a listening daemon, the
2759 process id is not written to the normal pid file path. However, &%-oP%& can be
2760 used to specify a path on the command line if a pid file is required.
2761
2762 The SIGHUP signal
2763 .cindex "SIGHUP"
2764 .cindex "daemon" "restarting"
2765 can be used to cause the daemon to re-execute itself. This should be done
2766 whenever Exim's configuration file, or any file that is incorporated into it by
2767 means of the &%.include%& facility, is changed, and also whenever a new version
2768 of Exim is installed. It is not necessary to do this when other files that are
2769 referenced from the configuration (for example, alias files) are changed,
2770 because these are reread each time they are used.
2771
2772 .vitem &%-bdf%&
2773 .oindex "&%-bdf%&"
2774 This option has the same effect as &%-bd%& except that it never disconnects
2775 from the controlling terminal, even when no debugging is specified.
2776
2777 .vitem &%-be%&
2778 .oindex "&%-be%&"
2779 .cindex "testing" "string expansion"
2780 .cindex "expansion" "testing"
2781 Run Exim in expansion testing mode. Exim discards its root privilege, to
2782 prevent ordinary users from using this mode to read otherwise inaccessible
2783 files. If no arguments are given, Exim runs interactively, prompting for lines
2784 of data. Otherwise, it processes each argument in turn.
2785
2786 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2787 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2788 used without command line arguments. If successful, it uses the &[readline()]&
2789 function, which provides extensive line-editing facilities, for reading the
2790 test data. A line history is supported.
2791
2792 Long expansion expressions can be split over several lines by using backslash
2793 continuations. As in Exim's run time configuration, white space at the start of
2794 continuation lines is ignored. Each argument or data line is passed through the
2795 string expansion mechanism, and the result is output. Variable values from the
2796 configuration file (for example, &$qualify_domain$&) are available, but no
2797 message-specific values (such as &$message_exim_id$&) are set, because no message
2798 is being processed (but see &%-bem%& and &%-Mset%&).
2799
2800 &*Note*&: If you use this mechanism to test lookups, and you change the data
2801 files or databases you are using, you must exit and restart Exim before trying
2802 the same lookup again. Otherwise, because each Exim process caches the results
2803 of lookups, you will just get the same result as before.
2804
2805 Macro processing is done on lines before string-expansion: new macros can be
2806 defined and macros will be expanded.
2807 Because macros in the config file are often used for secrets, those are only
2808 available to admin users.
2809
2810 .vitem &%-bem%&&~<&'filename'&>
2811 .oindex "&%-bem%&"
2812 .cindex "testing" "string expansion"
2813 .cindex "expansion" "testing"
2814 This option operates like &%-be%& except that it must be followed by the name
2815 of a file. For example:
2816 .code
2817 exim -bem /tmp/testmessage
2818 .endd
2819 The file is read as a message (as if receiving a locally-submitted non-SMTP
2820 message) before any of the test expansions are done. Thus, message-specific
2821 variables such as &$message_size$& and &$header_from:$& are available. However,
2822 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2823 recipients are read from the headers in the normal way, and are shown in the
2824 &$recipients$& variable. Note that recipients cannot be given on the command
2825 line, because further arguments are taken as strings to expand (just like
2826 &%-be%&).
2827
2828 .vitem &%-bF%&&~<&'filename'&>
2829 .oindex "&%-bF%&"
2830 .cindex "system filter" "testing"
2831 .cindex "testing" "system filter"
2832 This option is the same as &%-bf%& except that it assumes that the filter being
2833 tested is a system filter. The additional commands that are available only in
2834 system filters are recognized.
2835
2836 .vitem &%-bf%&&~<&'filename'&>
2837 .oindex "&%-bf%&"
2838 .cindex "filter" "testing"
2839 .cindex "testing" "filter file"
2840 .cindex "forward file" "testing"
2841 .cindex "testing" "forward file"
2842 .cindex "Sieve filter" "testing"
2843 This option runs Exim in user filter testing mode; the file is the filter file
2844 to be tested, and a test message must be supplied on the standard input. If
2845 there are no message-dependent tests in the filter, an empty file can be
2846 supplied.
2847
2848 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2849 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2850 filter and a user filter in the same run. For example:
2851 .code
2852 exim -bF /system/filter -bf /user/filter </test/message
2853 .endd
2854 This is helpful when the system filter adds header lines or sets filter
2855 variables that are used by the user filter.
2856
2857 If the test filter file does not begin with one of the special lines
2858 .code
2859 # Exim filter
2860 # Sieve filter
2861 .endd
2862 it is taken to be a normal &_.forward_& file, and is tested for validity under
2863 that interpretation. See sections &<<SECTitenonfilred>>& to
2864 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2865 redirection lists.
2866
2867 The result of an Exim command that uses &%-bf%&, provided no errors are
2868 detected, is a list of the actions that Exim would try to take if presented
2869 with the message for real. More details of filter testing are given in the
2870 separate document entitled &'Exim's interfaces to mail filtering'&.
2871
2872 When testing a filter file,
2873 .cindex "&""From""& line"
2874 .cindex "envelope sender"
2875 .oindex "&%-f%&" "for filter testing"
2876 the envelope sender can be set by the &%-f%& option,
2877 or by a &"From&~"& line at the start of the test message. Various parameters
2878 that would normally be taken from the envelope recipient address of the message
2879 can be set by means of additional command line options (see the next four
2880 options).
2881
2882 .vitem &%-bfd%&&~<&'domain'&>
2883 .oindex "&%-bfd%&"
2884 .vindex "&$qualify_domain$&"
2885 This sets the domain of the recipient address when a filter file is being
2886 tested by means of the &%-bf%& option. The default is the value of
2887 &$qualify_domain$&.
2888
2889 .vitem &%-bfl%&&~<&'local&~part'&>
2890 .oindex "&%-bfl%&"
2891 This sets the local part of the recipient address when a filter file is being
2892 tested by means of the &%-bf%& option. The default is the username of the
2893 process that calls Exim. A local part should be specified with any prefix or
2894 suffix stripped, because that is how it appears to the filter when a message is
2895 actually being delivered.
2896
2897 .vitem &%-bfp%&&~<&'prefix'&>
2898 .oindex "&%-bfp%&"
2899 This sets the prefix of the local part of the recipient address when a filter
2900 file is being tested by means of the &%-bf%& option. The default is an empty
2901 prefix.
2902
2903 .vitem &%-bfs%&&~<&'suffix'&>
2904 .oindex "&%-bfs%&"
2905 This sets the suffix of the local part of the recipient address when a filter
2906 file is being tested by means of the &%-bf%& option. The default is an empty
2907 suffix.
2908
2909 .vitem &%-bh%&&~<&'IP&~address'&>
2910 .oindex "&%-bh%&"
2911 .cindex "testing" "incoming SMTP"
2912 .cindex "SMTP" "testing incoming"
2913 .cindex "testing" "relay control"
2914 .cindex "relaying" "testing configuration"
2915 .cindex "policy control" "testing"
2916 .cindex "debugging" "&%-bh%& option"
2917 This option runs a fake SMTP session as if from the given IP address, using the
2918 standard input and output. The IP address may include a port number at the end,
2919 after a full stop. For example:
2920 .code
2921 exim -bh 10.9.8.7.1234
2922 exim -bh fe80::a00:20ff:fe86:a061.5678
2923 .endd
2924 When an IPv6 address is given, it is converted into canonical form. In the case
2925 of the second example above, the value of &$sender_host_address$& after
2926 conversion to the canonical form is
2927 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2928
2929 Comments as to what is going on are written to the standard error file. These
2930 include lines beginning with &"LOG"& for anything that would have been logged.
2931 This facility is provided for testing configuration options for incoming
2932 messages, to make sure they implement the required policy. For example, you can
2933 test your relay controls using &%-bh%&.
2934
2935 &*Warning 1*&:
2936 .cindex "RFC 1413"
2937 You can test features of the configuration that rely on ident (RFC 1413)
2938 information by using the &%-oMt%& option. However, Exim cannot actually perform
2939 an ident callout when testing using &%-bh%& because there is no incoming SMTP
2940 connection.
2941
2942 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2943 are also skipped when testing using &%-bh%&. If you want these callouts to
2944 occur, use &%-bhc%& instead.
2945
2946 Messages supplied during the testing session are discarded, and nothing is
2947 written to any of the real log files. There may be pauses when DNS (and other)
2948 lookups are taking place, and of course these may time out. The &%-oMi%& option
2949 can be used to specify a specific IP interface and port if this is important,
2950 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
2951 session were authenticated.
2952
2953 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2954 output just states whether a given recipient address from a given host is
2955 acceptable or not. See section &<<SECTcheckaccess>>&.
2956
2957 Features such as authentication and encryption, where the client input is not
2958 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
2959 specialized SMTP test program such as
2960 &url(http://jetmore.org/john/code/#swaks,swaks).
2961
2962 .vitem &%-bhc%&&~<&'IP&~address'&>
2963 .oindex "&%-bhc%&"
2964 This option operates in the same way as &%-bh%&, except that address
2965 verification callouts are performed if required. This includes consulting and
2966 updating the callout cache database.
2967
2968 .vitem &%-bi%&
2969 .oindex "&%-bi%&"
2970 .cindex "alias file" "building"
2971 .cindex "building alias file"
2972 .cindex "Sendmail compatibility" "&%-bi%& option"
2973 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
2974 Exim does not have the concept of a single alias file, and so it cannot mimic
2975 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
2976 tend to appear in various scripts such as NIS make files, so the option must be
2977 recognized.
2978
2979 If &%-bi%& is encountered, the command specified by the &%bi_command%&
2980 configuration option is run, under the uid and gid of the caller of Exim. If
2981 the &%-oA%& option is used, its value is passed to the command as an argument.
2982 The command set by &%bi_command%& may not contain arguments. The command can
2983 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
2984 if this is required. If the &%bi_command%& option is not set, calling Exim with
2985 &%-bi%& is a no-op.
2986
2987 . // Keep :help first, then the rest in alphabetical order
2988 .vitem &%-bI:help%&
2989 .oindex "&%-bI:help%&"
2990 .cindex "querying exim information"
2991 We shall provide various options starting &`-bI:`& for querying Exim for
2992 information. The output of many of these will be intended for machine
2993 consumption. This one is not. The &%-bI:help%& option asks Exim for a
2994 synopsis of supported options beginning &`-bI:`&. Use of any of these
2995 options shall cause Exim to exit after producing the requested output.
2996
2997 .vitem &%-bI:dscp%&
2998 .oindex "&%-bI:dscp%&"
2999 .cindex "DSCP" "values"
3000 This option causes Exim to emit an alphabetically sorted list of all
3001 recognised DSCP names.
3002
3003 .vitem &%-bI:sieve%&
3004 .oindex "&%-bI:sieve%&"
3005 .cindex "Sieve filter" "capabilities"
3006 This option causes Exim to emit an alphabetically sorted list of all supported
3007 Sieve protocol extensions on stdout, one per line. This is anticipated to be
3008 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
3009 &`SIEVE`& capability response line. As the precise list may depend upon
3010 compile-time build options, which this option will adapt to, this is the only
3011 way to guarantee a correct response.
3012
3013 .vitem &%-bm%&
3014 .oindex "&%-bm%&"
3015 .cindex "local message reception"
3016 This option runs an Exim receiving process that accepts an incoming,
3017 locally-generated message on the standard input. The recipients are given as the
3018 command arguments (except when &%-t%& is also present &-- see below). Each
3019 argument can be a comma-separated list of RFC 2822 addresses. This is the
3020 default option for selecting the overall action of an Exim call; it is assumed
3021 if no other conflicting option is present.
3022
3023 If any addresses in the message are unqualified (have no domain), they are
3024 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3025 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3026 suppressing this for special cases.
3027
3028 Policy checks on the contents of local messages can be enforced by means of
3029 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3030
3031 .cindex "return code" "for &%-bm%&"
3032 The return code is zero if the message is successfully accepted. Otherwise, the
3033 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3034
3035 The format
3036 .cindex "message" "format"
3037 .cindex "format" "message"
3038 .cindex "&""From""& line"
3039 .cindex "UUCP" "&""From""& line"
3040 .cindex "Sendmail compatibility" "&""From""& line"
3041 of the message must be as defined in RFC 2822, except that, for
3042 compatibility with Sendmail and Smail, a line in one of the forms
3043 .code
3044 From sender Fri Jan 5 12:55 GMT 1997
3045 From sender Fri, 5 Jan 97 12:55:01
3046 .endd
3047 (with the weekday optional, and possibly with additional text after the date)
3048 is permitted to appear at the start of the message. There appears to be no
3049 authoritative specification of the format of this line. Exim recognizes it by
3050 matching against the regular expression defined by the &%uucp_from_pattern%&
3051 option, which can be changed if necessary.
3052
3053 .oindex "&%-f%&" "overriding &""From""& line"
3054 The specified sender is treated as if it were given as the argument to the
3055 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3056 preference to the address taken from the message. The caller of Exim must be a
3057 trusted user for the sender of a message to be set in this way.
3058
3059 .vitem &%-bmalware%&&~<&'filename'&>
3060 .oindex "&%-bmalware%&"
3061 .cindex "testing", "malware"
3062 .cindex "malware scan test"
3063 This debugging option causes Exim to scan the given file or directory
3064 (depending on the used scanner interface),
3065 using the malware scanning framework. The option of &%av_scanner%& influences
3066 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3067 the expansion should have defaults which apply to this invocation. ACLs are
3068 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3069 will never be populated and &%-bmalware%& will fail.
3070
3071 Exim will have changed working directory before resolving the filename, so
3072 using fully qualified pathnames is advisable. Exim will be running as the Exim
3073 user when it tries to open the file, rather than as the invoking user.
3074 This option requires admin privileges.
3075
3076 The &%-bmalware%& option will not be extended to be more generally useful,
3077 there are better tools for file-scanning. This option exists to help
3078 administrators verify their Exim and AV scanner configuration.
3079
3080 .vitem &%-bnq%&
3081 .oindex "&%-bnq%&"
3082 .cindex "address qualification, suppressing"
3083 By default, Exim automatically qualifies unqualified addresses (those
3084 without domains) that appear in messages that are submitted locally (that
3085 is, not over TCP/IP). This qualification applies both to addresses in
3086 envelopes, and addresses in header lines. Sender addresses are qualified using
3087 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3088 defaults to the value of &%qualify_domain%&).
3089
3090 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3091 being used to re-submit messages that originally came from remote hosts after
3092 content scanning, you probably do not want to qualify unqualified addresses in
3093 header lines. (Such lines will be present only if you have not enabled a header
3094 syntax check in the appropriate ACL.)
3095
3096 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3097 messages that originate on the local host. When this is used, unqualified
3098 addresses in the envelope provoke errors (causing message rejection) and
3099 unqualified addresses in header lines are left alone.
3100
3101
3102 .vitem &%-bP%&
3103 .oindex "&%-bP%&"
3104 .cindex "configuration options" "extracting"
3105 .cindex "options" "configuration &-- extracting"
3106 If this option is given with no arguments, it causes the values of all Exim's
3107 main configuration options to be written to the standard output. The values
3108 of one or more specific options can be requested by giving their names as
3109 arguments, for example:
3110 .code
3111 exim -bP qualify_domain hold_domains
3112 .endd
3113 .cindex "hiding configuration option values"
3114 .cindex "configuration options" "hiding value of"
3115 .cindex "options" "hiding value of"
3116 However, any option setting that is preceded by the word &"hide"& in the
3117 configuration file is not shown in full, except to an admin user. For other
3118 users, the output is as in this example:
3119 .code
3120 mysql_servers = <value not displayable>
3121 .endd
3122 If &%config%& is given as an argument, the config is
3123 output, as it was parsed, any include file resolved, any comment removed.
3124
3125 If &%config_file%& is given as an argument, the name of the run time
3126 configuration file is output. (&%configure_file%& works too, for
3127 backward compatibility.)
3128 If a list of configuration files was supplied, the value that is output here
3129 is the name of the file that was actually used.
3130
3131 .cindex "options" "hiding name of"
3132 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3133 name will not be output.
3134
3135 .cindex "daemon" "process id (pid)"
3136 .cindex "pid (process id)" "of daemon"
3137 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3138 directories where log files and daemon pid files are written are output,
3139 respectively. If these values are unset, log files are written in a
3140 sub-directory of the spool directory called &%log%&, and the pid file is
3141 written directly into the spool directory.
3142
3143 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3144 .code
3145 exim -bP +local_domains
3146 .endd
3147 it searches for a matching named list of any type (domain, host, address, or
3148 local part) and outputs what it finds.
3149
3150 .cindex "options" "router &-- extracting"
3151 .cindex "options" "transport &-- extracting"
3152 .cindex "options" "authenticator &-- extracting"
3153 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3154 followed by the name of an appropriate driver instance, the option settings for
3155 that driver are output. For example:
3156 .code
3157 exim -bP transport local_delivery
3158 .endd
3159 The generic driver options are output first, followed by the driver's private
3160 options. A list of the names of drivers of a particular type can be obtained by
3161 using one of the words &%router_list%&, &%transport_list%&, or
3162 &%authenticator_list%&, and a complete list of all drivers with their option
3163 settings can be obtained by using &%routers%&, &%transports%&, or
3164 &%authenticators%&.
3165
3166 .cindex "environment"
3167 If &%environment%& is given as an argument, the set of environment
3168 variables is output, line by line. Using the &%-n%& flag suppresses the value of the
3169 variables.
3170
3171 .cindex "options" "macro &-- extracting"
3172 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3173 are available, similarly to the drivers. Because macros are sometimes used
3174 for storing passwords, this option is restricted.
3175 The output format is one item per line.
3176 For the "-bP macro <name>" form, if no such macro is found
3177 the exit status will be nonzero.
3178
3179 .vitem &%-bp%&
3180 .oindex "&%-bp%&"
3181 .cindex "queue" "listing messages on"
3182 .cindex "listing" "messages on the queue"
3183 This option requests a listing of the contents of the mail queue on the
3184 standard output. If the &%-bp%& option is followed by a list of message ids,
3185 just those messages are listed. By default, this option can be used only by an
3186 admin user. However, the &%queue_list_requires_admin%& option can be set false
3187 to allow any user to see the queue.
3188
3189 Each message on the queue is displayed as in the following example:
3190 .code
3191 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3192 red.king@looking-glass.fict.example
3193 <other addresses>
3194 .endd
3195 .cindex "message" "size in queue listing"
3196 .cindex "size" "of message"
3197 The first line contains the length of time the message has been on the queue
3198 (in this case 25 minutes), the size of the message (2.9K), the unique local
3199 identifier for the message, and the message sender, as contained in the
3200 envelope. For bounce messages, the sender address is empty, and appears as
3201 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3202 the default sender address, the user's login name is shown in parentheses
3203 before the sender address.
3204
3205 .cindex "frozen messages" "in queue listing"
3206 If the message is frozen (attempts to deliver it are suspended) then the text
3207 &"*** frozen ***"& is displayed at the end of this line.
3208
3209 The recipients of the message (taken from the envelope, not the headers) are
3210 displayed on subsequent lines. Those addresses to which the message has already
3211 been delivered are marked with the letter D. If an original address gets
3212 expanded into several addresses via an alias or forward file, the original is
3213 displayed with a D only when deliveries for all of its child addresses are
3214 complete.
3215
3216
3217 .vitem &%-bpa%&
3218 .oindex "&%-bpa%&"
3219 This option operates like &%-bp%&, but in addition it shows delivered addresses
3220 that were generated from the original top level address(es) in each message by
3221 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3222 of just &"D"&.
3223
3224
3225 .vitem &%-bpc%&
3226 .oindex "&%-bpc%&"
3227 .cindex "queue" "count of messages on"
3228 This option counts the number of messages on the queue, and writes the total
3229 to the standard output. It is restricted to admin users, unless
3230 &%queue_list_requires_admin%& is set false.
3231
3232
3233 .vitem &%-bpr%&
3234 .oindex "&%-bpr%&"
3235 This option operates like &%-bp%&, but the output is not sorted into
3236 chronological order of message arrival. This can speed it up when there are
3237 lots of messages on the queue, and is particularly useful if the output is
3238 going to be post-processed in a way that doesn't need the sorting.
3239
3240 .vitem &%-bpra%&
3241 .oindex "&%-bpra%&"
3242 This option is a combination of &%-bpr%& and &%-bpa%&.
3243
3244 .vitem &%-bpru%&
3245 .oindex "&%-bpru%&"
3246 This option is a combination of &%-bpr%& and &%-bpu%&.
3247
3248
3249 .vitem &%-bpu%&
3250 .oindex "&%-bpu%&"
3251 This option operates like &%-bp%& but shows only undelivered top-level
3252 addresses for each message displayed. Addresses generated by aliasing or
3253 forwarding are not shown, unless the message was deferred after processing by a
3254 router with the &%one_time%& option set.
3255
3256
3257 .vitem &%-brt%&
3258 .oindex "&%-brt%&"
3259 .cindex "testing" "retry configuration"
3260 .cindex "retry" "configuration testing"
3261 This option is for testing retry rules, and it must be followed by up to three
3262 arguments. It causes Exim to look for a retry rule that matches the values
3263 and to write it to the standard output. For example:
3264 .code
3265 exim -brt bach.comp.mus.example
3266 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3267 .endd
3268 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3269 argument, which is required, can be a complete address in the form
3270 &'local_part@domain'&, or it can be just a domain name. If the second argument
3271 contains a dot, it is interpreted as an optional second domain name; if no
3272 retry rule is found for the first argument, the second is tried. This ties in
3273 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3274 rule is found that matches the host, one that matches the mail domain is
3275 sought. Finally, an argument that is the name of a specific delivery error, as
3276 used in setting up retry rules, can be given. For example:
3277 .code
3278 exim -brt haydn.comp.mus.example quota_3d
3279 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3280 .endd
3281
3282 .vitem &%-brw%&
3283 .oindex "&%-brw%&"
3284 .cindex "testing" "rewriting"
3285 .cindex "rewriting" "testing"
3286 This option is for testing address rewriting rules, and it must be followed by
3287 a single argument, consisting of either a local part without a domain, or a
3288 complete address with a fully qualified domain. Exim outputs how this address
3289 would be rewritten for each possible place it might appear. See chapter
3290 &<<CHAPrewrite>>& for further details.
3291
3292 .vitem &%-bS%&
3293 .oindex "&%-bS%&"
3294 .cindex "SMTP" "batched incoming"
3295 .cindex "batched SMTP input"
3296 This option is used for batched SMTP input, which is an alternative interface
3297 for non-interactive local message submission. A number of messages can be
3298 submitted in a single run. However, despite its name, this is not really SMTP
3299 input. Exim reads each message's envelope from SMTP commands on the standard
3300 input, but generates no responses. If the caller is trusted, or
3301 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3302 believed; otherwise the sender is always the caller of Exim.
3303
3304 The message itself is read from the standard input, in SMTP format (leading
3305 dots doubled), terminated by a line containing just a single dot. An error is
3306 provoked if the terminating dot is missing. A further message may then follow.
3307
3308 As for other local message submissions, the contents of incoming batch SMTP
3309 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3310 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3311 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3312
3313 Some other SMTP commands are recognized in the input. HELO and EHLO act
3314 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3315 QUIT quits, ignoring the rest of the standard input.
3316
3317 .cindex "return code" "for &%-bS%&"
3318 If any error is encountered, reports are written to the standard output and
3319 error streams, and Exim gives up immediately. The return code is 0 if no error
3320 was detected; it is 1 if one or more messages were accepted before the error
3321 was detected; otherwise it is 2.
3322
3323 More details of input using batched SMTP are given in section
3324 &<<SECTincomingbatchedSMTP>>&.
3325
3326 .vitem &%-bs%&
3327 .oindex "&%-bs%&"
3328 .cindex "SMTP" "local input"
3329 .cindex "local SMTP input"
3330 This option causes Exim to accept one or more messages by reading SMTP commands
3331 on the standard input, and producing SMTP replies on the standard output. SMTP
3332 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3333 Some user agents use this interface as a way of passing locally-generated
3334 messages to the MTA.
3335
3336 In
3337 .cindex "sender" "source of"
3338 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3339 set, the senders of messages are taken from the SMTP MAIL commands.
3340 Otherwise the content of these commands is ignored and the sender is set up as
3341 the calling user. Unqualified addresses are automatically qualified using
3342 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3343 &%-bnq%& option is used.
3344
3345 .cindex "inetd"
3346 The
3347 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3348 using a listening daemon. Exim can distinguish the two cases by checking
3349 whether the standard input is a TCP/IP socket. When Exim is called from
3350 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3351 above concerning senders and qualification do not apply. In this situation,
3352 Exim behaves in exactly the same way as it does when receiving a message via
3353 the listening daemon.
3354
3355 .vitem &%-bt%&
3356 .oindex "&%-bt%&"
3357 .cindex "testing" "addresses"
3358 .cindex "address" "testing"
3359 This option runs Exim in address testing mode, in which each argument is taken
3360 as a recipient address to be tested for deliverability. The results are
3361 written to the standard output. If a test fails, and the caller is not an admin
3362 user, no details of the failure are output, because these might contain
3363 sensitive information such as usernames and passwords for database lookups.
3364
3365 If no arguments are given, Exim runs in an interactive manner, prompting with a
3366 right angle bracket for addresses to be tested.
3367
3368 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3369 &[readline()]& function, because it is running as &'root'& and there are
3370 security issues.
3371
3372 Each address is handled as if it were the recipient address of a message
3373 (compare the &%-bv%& option). It is passed to the routers and the result is
3374 written to the standard output. However, any router that has
3375 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3376 genuine routing tests if your first router passes everything to a scanner
3377 program.
3378
3379 .cindex "return code" "for &%-bt%&"
3380 The return code is 2 if any address failed outright; it is 1 if no address
3381 failed outright but at least one could not be resolved for some reason. Return
3382 code 0 is given only when all addresses succeed.
3383
3384 .cindex "duplicate addresses"
3385 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3386 addresses after routing is complete, so that only one delivery takes place.
3387 This does not happen when testing with &%-bt%&; the full results of routing are
3388 always shown.
3389
3390 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3391 routers in the configuration makes any tests on the sender address of a
3392 message,
3393 .oindex "&%-f%&" "for address testing"
3394 you can use the &%-f%& option to set an appropriate sender when running
3395 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3396 default qualifying domain. However, if you have set up (for example) routers
3397 whose behaviour depends on the contents of an incoming message, you cannot test
3398 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3399 doing such tests.
3400
3401 .vitem &%-bV%&
3402 .oindex "&%-bV%&"
3403 .cindex "version number of Exim"
3404 This option causes Exim to write the current version number, compilation
3405 number, and compilation date of the &'exim'& binary to the standard output.
3406 It also lists the DBM library that is being used, the optional modules (such as
3407 specific lookup types), the drivers that are included in the binary, and the
3408 name of the run time configuration file that is in use.
3409
3410 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3411 configuration file. However, this is a static check only. It cannot check
3412 values that are to be expanded. For example, although a misspelt ACL verb is
3413 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3414 alone to discover (for example) all the typos in the configuration; some
3415 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3416 dynamic testing facilities.
3417
3418 .vitem &%-bv%&
3419 .oindex "&%-bv%&"
3420 .cindex "verifying address" "using &%-bv%&"
3421 .cindex "address" "verification"
3422 This option runs Exim in address verification mode, in which each argument is
3423 taken as a recipient address to be verified by the routers. (This does
3424 not involve any verification callouts). During normal operation, verification
3425 happens mostly as a consequence processing a &%verify%& condition in an ACL
3426 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3427 including callouts, see the &%-bh%& and &%-bhc%& options.
3428
3429 If verification fails, and the caller is not an admin user, no details of the
3430 failure are output, because these might contain sensitive information such as
3431 usernames and passwords for database lookups.
3432
3433 If no arguments are given, Exim runs in an interactive manner, prompting with a
3434 right angle bracket for addresses to be verified.
3435
3436 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3437 &[readline()]& function, because it is running as &'exim'& and there are
3438 security issues.
3439
3440 Verification differs from address testing (the &%-bt%& option) in that routers
3441 that have &%no_verify%& set are skipped, and if the address is accepted by a
3442 router that has &%fail_verify%& set, verification fails. The address is
3443 verified as a recipient if &%-bv%& is used; to test verification for a sender
3444 address, &%-bvs%& should be used.
3445
3446 If the &%-v%& option is not set, the output consists of a single line for each
3447 address, stating whether it was verified or not, and giving a reason in the
3448 latter case. Without &%-v%&, generating more than one address by redirection
3449 causes verification to end successfully, without considering the generated
3450 addresses. However, if just one address is generated, processing continues,
3451 and the generated address must verify successfully for the overall verification
3452 to succeed.
3453
3454 When &%-v%& is set, more details are given of how the address has been handled,
3455 and in the case of address redirection, all the generated addresses are also
3456 considered. Verification may succeed for some and fail for others.
3457
3458 The
3459 .cindex "return code" "for &%-bv%&"
3460 return code is 2 if any address failed outright; it is 1 if no address
3461 failed outright but at least one could not be resolved for some reason. Return
3462 code 0 is given only when all addresses succeed.
3463
3464 If any of the routers in the configuration makes any tests on the sender
3465 address of a message, you should use the &%-f%& option to set an appropriate
3466 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3467 calling user at the default qualifying domain.
3468
3469 .vitem &%-bvs%&
3470 .oindex "&%-bvs%&"
3471 This option acts like &%-bv%&, but verifies the address as a sender rather
3472 than a recipient address. This affects any rewriting and qualification that
3473 might happen.
3474
3475 .vitem &%-bw%&
3476 .oindex "&%-bw%&"
3477 .cindex "daemon"
3478 .cindex "inetd"
3479 .cindex "inetd" "wait mode"
3480 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3481 similarly to the &%-bd%& option. All port specifications on the command-line
3482 and in the configuration file are ignored. Queue-running may not be specified.
3483
3484 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3485 listening for connections. This permits the system to start up and have
3486 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3487 each port only when the first connection is received.
3488
3489 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3490 which the daemon will exit, which should cause inetd to listen once more.
3491
3492 .vitem &%-C%&&~<&'filelist'&>
3493 .oindex "&%-C%&"
3494 .cindex "configuration file" "alternate"
3495 .cindex "CONFIGURE_FILE"
3496 .cindex "alternate configuration file"
3497 This option causes Exim to find the run time configuration file from the given
3498 list instead of from the list specified by the CONFIGURE_FILE
3499 compile-time setting. Usually, the list will consist of just a single file
3500 name, but it can be a colon-separated list of names. In this case, the first
3501 file that exists is used. Failure to open an existing file stops Exim from
3502 proceeding any further along the list, and an error is generated.
3503
3504 When this option is used by a caller other than root, and the list is different
3505 from the compiled-in list, Exim gives up its root privilege immediately, and
3506 runs with the real and effective uid and gid set to those of the caller.
3507 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3508 file contains a list of full pathnames, one per line, for configuration files
3509 which are trusted. Root privilege is retained for any configuration file so
3510 listed, as long as the caller is the Exim user (or the user specified in the
3511 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3512 not writeable by inappropriate users or groups.
3513
3514 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3515 configuration using &%-C%& right through message reception and delivery,
3516 even if the caller is root. The reception works, but by that time, Exim is
3517 running as the Exim user, so when it re-executes to regain privilege for the
3518 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3519 test reception and delivery using two separate commands (one to put a message
3520 on the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3521
3522 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3523 prefix string with which any file named in a &%-C%& command line option
3524 must start. In addition, the file name must not contain the sequence &`/../`&.
3525 However, if the value of the &%-C%& option is identical to the value of
3526 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3527 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3528 unset, any file name can be used with &%-C%&.
3529
3530 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3531 to a directory to which only root has access. This prevents someone who has
3532 broken into the Exim account from running a privileged Exim with an arbitrary
3533 configuration file.
3534
3535 The &%-C%& facility is useful for ensuring that configuration files are
3536 syntactically correct, but cannot be used for test deliveries, unless the
3537 caller is privileged, or unless it is an exotic configuration that does not
3538 require privilege. No check is made on the owner or group of the files
3539 specified by this option.
3540
3541
3542 .vitem &%-D%&<&'macro'&>=<&'value'&>
3543 .oindex "&%-D%&"
3544 .cindex "macro" "setting on command line"
3545 This option can be used to override macro definitions in the configuration file
3546 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3547 unprivileged caller, it causes Exim to give up its root privilege.
3548 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3549 completely disabled, and its use causes an immediate error exit.
3550
3551 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3552 colon-separated list of macros which are considered safe and, if &%-D%& only
3553 supplies macros from this list, and the values are acceptable, then Exim will
3554 not give up root privilege if the caller is root, the Exim run-time user, or
3555 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3556 to be removed in the future. Acceptable values for the macros satisfy the
3557 regexp: &`^[A-Za-z0-9_/.-]*$`&
3558
3559 The entire option (including equals sign if present) must all be within one
3560 command line item. &%-D%& can be used to set the value of a macro to the empty
3561 string, in which case the equals sign is optional. These two commands are
3562 synonymous:
3563 .code
3564 exim -DABC ...
3565 exim -DABC= ...
3566 .endd
3567 To include spaces in a macro definition item, quotes must be used. If you use
3568 quotes, spaces are permitted around the macro name and the equals sign. For
3569 example:
3570 .code
3571 exim '-D ABC = something' ...
3572 .endd
3573 &%-D%& may be repeated up to 10 times on a command line.
3574 Only macro names up to 22 letters long can be set.
3575
3576
3577 .vitem &%-d%&<&'debug&~options'&>
3578 .oindex "&%-d%&"
3579 .cindex "debugging" "list of selectors"
3580 .cindex "debugging" "&%-d%& option"
3581 This option causes debugging information to be written to the standard
3582 error stream. It is restricted to admin users because debugging output may show
3583 database queries that contain password information. Also, the details of users'
3584 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3585 writes an error message to the standard error stream and exits with a non-zero
3586 return code.
3587
3588 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3589 standard debugging data is output. This can be reduced, or increased to include
3590 some more rarely needed information, by directly following &%-d%& with a string
3591 made up of names preceded by plus or minus characters. These add or remove sets
3592 of debugging data, respectively. For example, &%-d+filter%& adds filter
3593 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3594 no spaces are allowed in the debug setting. The available debugging categories
3595 are:
3596 .display
3597 &`acl `& ACL interpretation
3598 &`auth `& authenticators
3599 &`deliver `& general delivery logic
3600 &`dns `& DNS lookups (see also resolver)
3601 &`dnsbl `& DNS black list (aka RBL) code
3602 &`exec `& arguments for &[execv()]& calls
3603 &`expand `& detailed debugging for string expansions
3604 &`filter `& filter handling
3605 &`hints_lookup `& hints data lookups
3606 &`host_lookup `& all types of name-to-IP address handling
3607 &`ident `& ident lookup
3608 &`interface `& lists of local interfaces
3609 &`lists `& matching things in lists
3610 &`load `& system load checks
3611 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3612 &<<CHAPlocalscan>>&)
3613 &`lookup `& general lookup code and all lookups
3614 &`memory `& memory handling
3615 &`pid `& add pid to debug output lines
3616 &`process_info `& setting info for the process log
3617 &`queue_run `& queue runs
3618 &`receive `& general message reception logic
3619 &`resolver `& turn on the DNS resolver's debugging output
3620 &`retry `& retry handling
3621 &`rewrite `& address rewriting
3622 &`route `& address routing
3623 &`timestamp `& add timestamp to debug output lines
3624 &`tls `& TLS logic
3625 &`transport `& transports
3626 &`uid `& changes of uid/gid and looking up uid/gid
3627 &`verify `& address verification logic
3628 &`all `& almost all of the above (see below), and also &%-v%&
3629 .endd
3630 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3631 for &`-all`&. The reason for this is that &`+all`& is something that people
3632 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3633 is included, an awful lot of output that is very rarely of interest is
3634 generated, so it now has to be explicitly requested. However, &`-all`& does
3635 turn everything off.
3636
3637 .cindex "resolver, debugging output"
3638 .cindex "DNS resolver, debugging output"
3639 The &`resolver`& option produces output only if the DNS resolver was compiled
3640 with DEBUG enabled. This is not the case in some operating systems. Also,
3641 unfortunately, debugging output from the DNS resolver is written to stdout
3642 rather than stderr.
3643
3644 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3645 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3646 However, the &`pid`& selector is forced when debugging is turned on for a
3647 daemon, which then passes it on to any re-executed Exims. Exim also
3648 automatically adds the pid to debug lines when several remote deliveries are
3649 run in parallel.
3650
3651 The &`timestamp`& selector causes the current time to be inserted at the start
3652 of all debug output lines. This can be useful when trying to track down delays
3653 in processing.
3654
3655 If the &%debug_print%& option is set in any driver, it produces output whenever
3656 any debugging is selected, or if &%-v%& is used.
3657
3658 .vitem &%-dd%&<&'debug&~options'&>
3659 .oindex "&%-dd%&"
3660 This option behaves exactly like &%-d%& except when used on a command that
3661 starts a daemon process. In that case, debugging is turned off for the
3662 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3663 behaviour of the daemon without creating as much output as full debugging does.
3664
3665 .vitem &%-dropcr%&
3666 .oindex "&%-dropcr%&"
3667 This is an obsolete option that is now a no-op. It used to affect the way Exim
3668 handled CR and LF characters in incoming messages. What happens now is
3669 described in section &<<SECTlineendings>>&.
3670
3671 .vitem &%-E%&
3672 .oindex "&%-E%&"
3673 .cindex "bounce message" "generating"
3674 This option specifies that an incoming message is a locally-generated delivery
3675 failure report. It is used internally by Exim when handling delivery failures
3676 and is not intended for external use. Its only effect is to stop Exim
3677 generating certain messages to the postmaster, as otherwise message cascades
3678 could occur in some situations. As part of the same option, a message id may
3679 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3680 new message contains the id, following &"R="&, as a cross-reference.
3681
3682 .vitem &%-e%&&'x'&
3683 .oindex "&%-e%&&'x'&"
3684 There are a number of Sendmail options starting with &%-oe%& which seem to be
3685 called by various programs without the leading &%o%& in the option. For
3686 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3687 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3688
3689 .vitem &%-F%&&~<&'string'&>
3690 .oindex "&%-F%&"
3691 .cindex "sender" "name"
3692 .cindex "name" "of sender"
3693 This option sets the sender's full name for use when a locally-generated
3694 message is being accepted. In the absence of this option, the user's &'gecos'&
3695 entry from the password data is used. As users are generally permitted to alter
3696 their &'gecos'& entries, no security considerations are involved. White space
3697 between &%-F%& and the <&'string'&> is optional.
3698
3699 .vitem &%-f%&&~<&'address'&>
3700 .oindex "&%-f%&"
3701 .cindex "sender" "address"
3702 .cindex "address" "sender"
3703 .cindex "trusted users"
3704 .cindex "envelope sender"
3705 .cindex "user" "trusted"
3706 This option sets the address of the envelope sender of a locally-generated
3707 message (also known as the return path). The option can normally be used only
3708 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3709 users to use it.
3710
3711 Processes running as root or the Exim user are always trusted. Other
3712 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3713 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3714 of a local message is set to the caller's login name at the default qualify
3715 domain.
3716
3717 There is one exception to the restriction on the use of &%-f%&: an empty sender
3718 can be specified by any user, trusted or not, to create a message that can
3719 never provoke a bounce. An empty sender can be specified either as an empty
3720 string, or as a pair of angle brackets with nothing between them, as in these
3721 examples of shell commands:
3722 .code
3723 exim -f '<>' user@domain
3724 exim -f "" user@domain
3725 .endd
3726 In addition, the use of &%-f%& is not restricted when testing a filter file
3727 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3728 &%-bv%& options.
3729
3730 Allowing untrusted users to change the sender address does not of itself make
3731 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3732 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3733 though this can be overridden by setting &%no_local_from_check%&.
3734
3735 White
3736 .cindex "&""From""& line"
3737 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3738 given as two arguments or one combined argument). The sender of a
3739 locally-generated message can also be set (when permitted) by an initial
3740 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3741 if &%-f%& is also present, it overrides &"From&~"&.
3742
3743 .vitem &%-G%&
3744 .oindex "&%-G%&"
3745 .cindex "submission fixups, suppressing (command-line)"
3746 This option is equivalent to an ACL applying:
3747 .code
3748 control = suppress_local_fixups
3749 .endd
3750 for every message received. Note that Sendmail will complain about such
3751 bad formatting, where Exim silently just does not fix it up. This may change
3752 in future.
3753
3754 As this affects audit information, the caller must be a trusted user to use
3755 this option.
3756
3757 .vitem &%-h%&&~<&'number'&>
3758 .oindex "&%-h%&"
3759 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3760 This option is accepted for compatibility with Sendmail, but has no effect. (In
3761 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3762 headers.)
3763
3764 .vitem &%-i%&
3765 .oindex "&%-i%&"
3766 .cindex "Solaris" "&'mail'& command"
3767 .cindex "dot" "in incoming non-SMTP message"
3768 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3769 line by itself should not terminate an incoming, non-SMTP message. I can find
3770 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3771 command in Solaris 2.4 uses it. See also &%-ti%&.
3772
3773 .vitem &%-L%&&~<&'tag'&>
3774 .oindex "&%-L%&"
3775 .cindex "syslog" "process name; set with flag"
3776 This option is equivalent to setting &%syslog_processname%& in the config
3777 file and setting &%log_file_path%& to &`syslog`&.
3778 Its use is restricted to administrators. The configuration file has to be
3779 read and parsed, to determine access rights, before this is set and takes
3780 effect, so early configuration file errors will not honour this flag.
3781
3782 The tag should not be longer than 32 characters.
3783
3784 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3785 .oindex "&%-M%&"
3786 .cindex "forcing delivery"
3787 .cindex "delivery" "forcing attempt"
3788 .cindex "frozen messages" "forcing delivery"
3789 This option requests Exim to run a delivery attempt on each message in turn. If
3790 any of the messages are frozen, they are automatically thawed before the
3791 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3792 and &%hold_domains%& are ignored.
3793
3794 Retry
3795 .cindex "hints database" "overriding retry hints"
3796 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3797 the normal retry time has not yet been reached. This option requires the caller
3798 to be an admin user. However, there is an option called &%prod_requires_admin%&
3799 which can be set false to relax this restriction (and also the same requirement
3800 for the &%-q%&, &%-R%&, and &%-S%& options).
3801
3802 The deliveries happen synchronously, that is, the original Exim process does
3803 not terminate until all the delivery attempts have finished. No output is
3804 produced unless there is a serious error. If you want to see what is happening,
3805 use the &%-v%& option as well, or inspect Exim's main log.
3806
3807 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3808 .oindex "&%-Mar%&"
3809 .cindex "message" "adding recipients"
3810 .cindex "recipient" "adding"
3811 This option requests Exim to add the addresses to the list of recipients of the
3812 message (&"ar"& for &"add recipients"&). The first argument must be a message
3813 id, and the remaining ones must be email addresses. However, if the message is
3814 active (in the middle of a delivery attempt), it is not altered. This option
3815 can be used only by an admin user.
3816
3817 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3818 &~<&'message&~id'&>"
3819 .oindex "&%-MC%&"
3820 .cindex "SMTP" "passed connection"
3821 .cindex "SMTP" "multiple deliveries"
3822 .cindex "multiple SMTP deliveries"
3823 This option is not intended for use by external callers. It is used internally
3824 by Exim to invoke another instance of itself to deliver a waiting message using
3825 an existing SMTP connection, which is passed as the standard input. Details are
3826 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3827 must be root or the Exim user in order to use it.
3828
3829 .vitem &%-MCA%&
3830 .oindex "&%-MCA%&"
3831 This option is not intended for use by external callers. It is used internally
3832 by Exim in conjunction with the &%-MC%& option. It signifies that the
3833 connection to the remote host has been authenticated.
3834
3835 .vitem &%-MCD%&
3836 .oindex "&%-MCD%&"
3837 This option is not intended for use by external callers. It is used internally
3838 by Exim in conjunction with the &%-MC%& option. It signifies that the
3839 remote host supports the ESMTP &_DSN_& extension.
3840
3841 .vitem &%-MCG%&&~<&'queue&~name'&>
3842 .oindex "&%-MCG%&"
3843 This option is not intended for use by external callers. It is used internally
3844 by Exim in conjunction with the &%-MC%& option. It signifies that an
3845 alternate queue is used, named by the following argument.
3846
3847 .vitem &%-MCK%&
3848 .oindex "&%-MCK%&"
3849 This option is not intended for use by external callers. It is used internally
3850 by Exim in conjunction with the &%-MC%& option. It signifies that a
3851 remote host supports the ESMTP &_CHUNKING_& extension.
3852
3853 .vitem &%-MCP%&
3854 .oindex "&%-MCP%&"
3855 This option is not intended for use by external callers. It is used internally
3856 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3857 which Exim is connected supports pipelining.
3858
3859 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3860 .oindex "&%-MCQ%&"
3861 This option is not intended for use by external callers. It is used internally
3862 by Exim in conjunction with the &%-MC%& option when the original delivery was
3863 started by a queue runner. It passes on the process id of the queue runner,
3864 together with the file descriptor number of an open pipe. Closure of the pipe
3865 signals the final completion of the sequence of processes that are passing
3866 messages through the same SMTP connection.
3867
3868 .vitem &%-MCS%&
3869 .oindex "&%-MCS%&"
3870 This option is not intended for use by external callers. It is used internally
3871 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3872 SMTP SIZE option should be used on messages delivered down the existing
3873 connection.
3874
3875 .vitem &%-MCT%&
3876 .oindex "&%-MCT%&"
3877 This option is not intended for use by external callers. It is used internally
3878 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3879 host to which Exim is connected supports TLS encryption.
3880
3881 .vitem &%-MCt%&&~<&'IP&~address'&>&~<&'port'&>&~<&'cipher'&>
3882 .oindex "&%-MCt%&"
3883 This option is not intended for use by external callers. It is used internally
3884 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3885 connection is being proxied by a parent process for handling TLS encryption.
3886 The arguments give the local address and port being proxied, and the TLS cipher.
3887
3888 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3889 .oindex "&%-Mc%&"
3890 .cindex "hints database" "not overridden by &%-Mc%&"
3891 .cindex "delivery" "manually started &-- not forced"
3892 This option requests Exim to run a delivery attempt on each message in turn,
3893 but unlike the &%-M%& option, it does check for retry hints, and respects any
3894 that are found. This option is not very useful to external callers. It is
3895 provided mainly for internal use by Exim when it needs to re-invoke itself in
3896 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3897 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3898 respects retry times and other options such as &%hold_domains%& that are
3899 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3900 If you want to run a specific delivery as if in a queue run, you should use
3901 &%-q%& with a message id argument. A distinction between queue run deliveries
3902 and other deliveries is made in one or two places.
3903
3904 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3905 .oindex "&%-Mes%&"
3906 .cindex "message" "changing sender"
3907 .cindex "sender" "changing"
3908 This option requests Exim to change the sender address in the message to the
3909 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3910 &"edit sender"&). There must be exactly two arguments. The first argument must
3911 be a message id, and the second one an email address. However, if the message
3912 is active (in the middle of a delivery attempt), its status is not altered.
3913 This option can be used only by an admin user.
3914
3915 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3916 .oindex "&%-Mf%&"
3917 .cindex "freezing messages"
3918 .cindex "message" "manually freezing"
3919 This option requests Exim to mark each listed message as &"frozen"&. This
3920 prevents any delivery attempts taking place until the message is &"thawed"&,
3921 either manually or as a result of the &%auto_thaw%& configuration option.
3922 However, if any of the messages are active (in the middle of a delivery
3923 attempt), their status is not altered. This option can be used only by an admin
3924 user.
3925
3926 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3927 .oindex "&%-Mg%&"
3928 .cindex "giving up on messages"
3929 .cindex "message" "abandoning delivery attempts"
3930 .cindex "delivery" "abandoning further attempts"
3931 This option requests Exim to give up trying to deliver the listed messages,
3932 including any that are frozen. However, if any of the messages are active,
3933 their status is not altered. For non-bounce messages, a delivery error message
3934 is sent to the sender, containing the text &"cancelled by administrator"&.
3935 Bounce messages are just discarded. This option can be used only by an admin
3936 user.
3937
3938 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3939 .oindex "&%-Mmad%&"
3940 .cindex "delivery" "cancelling all"
3941 This option requests Exim to mark all the recipient addresses in the messages
3942 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
3943 message is active (in the middle of a delivery attempt), its status is not
3944 altered. This option can be used only by an admin user.
3945
3946 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3947 .oindex "&%-Mmd%&"
3948 .cindex "delivery" "cancelling by address"
3949 .cindex "recipient" "removing"
3950 .cindex "removing recipients"
3951 This option requests Exim to mark the given addresses as already delivered
3952 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
3953 the remaining ones must be email addresses. These are matched to recipient
3954 addresses in the message in a case-sensitive manner. If the message is active
3955 (in the middle of a delivery attempt), its status is not altered. This option
3956 can be used only by an admin user.
3957
3958 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3959 .oindex "&%-Mrm%&"
3960 .cindex "removing messages"
3961 .cindex "abandoning mail"
3962 .cindex "message" "manually discarding"
3963 This option requests Exim to remove the given messages from the queue. No
3964 bounce messages are sent; each message is simply forgotten. However, if any of
3965 the messages are active, their status is not altered. This option can be used
3966 only by an admin user or by the user who originally caused the message to be
3967 placed on the queue.
3968
3969 . .new
3970 . .vitem &%-MS%&
3971 . .oindex "&%-MS%&"
3972 . .cindex REQUIRETLS
3973 . This option is used to request REQUIRETLS processing on the message.
3974 . It is used internally by Exim in conjunction with -E when generating
3975 . a bounce message.
3976 . .wen
3977
3978 .vitem &%-Mset%&&~<&'message&~id'&>
3979 .oindex "&%-Mset%&"
3980 .cindex "testing" "string expansion"
3981 .cindex "expansion" "testing"
3982 This option is useful only in conjunction with &%-be%& (that is, when testing
3983 string expansions). Exim loads the given message from its spool before doing
3984 the test expansions, thus setting message-specific variables such as
3985 &$message_size$& and the header variables. The &$recipients$& variable is made
3986 available. This feature is provided to make it easier to test expansions that
3987 make use of these variables. However, this option can be used only by an admin
3988 user. See also &%-bem%&.
3989
3990 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3991 .oindex "&%-Mt%&"
3992 .cindex "thawing messages"
3993 .cindex "unfreezing messages"
3994 .cindex "frozen messages" "thawing"
3995 .cindex "message" "thawing frozen"
3996 This option requests Exim to &"thaw"& any of the listed messages that are
3997 &"frozen"&, so that delivery attempts can resume. However, if any of the
3998 messages are active, their status is not altered. This option can be used only
3999 by an admin user.
4000
4001 .vitem &%-Mvb%&&~<&'message&~id'&>
4002 .oindex "&%-Mvb%&"
4003 .cindex "listing" "message body"
4004 .cindex "message" "listing body of"
4005 This option causes the contents of the message body (-D) spool file to be
4006 written to the standard output. This option can be used only by an admin user.
4007
4008 .vitem &%-Mvc%&&~<&'message&~id'&>
4009 .oindex "&%-Mvc%&"
4010 .cindex "message" "listing in RFC 2822 format"
4011 .cindex "listing" "message in RFC 2822 format"
4012 This option causes a copy of the complete message (header lines plus body) to
4013 be written to the standard output in RFC 2822 format. This option can be used
4014 only by an admin user.
4015
4016 .vitem &%-Mvh%&&~<&'message&~id'&>
4017 .oindex "&%-Mvh%&"
4018 .cindex "listing" "message headers"
4019 .cindex "header lines" "listing"
4020 .cindex "message" "listing header lines"
4021 This option causes the contents of the message headers (-H) spool file to be
4022 written to the standard output. This option can be used only by an admin user.
4023
4024 .vitem &%-Mvl%&&~<&'message&~id'&>
4025 .oindex "&%-Mvl%&"
4026 .cindex "listing" "message log"
4027 .cindex "message" "listing message log"
4028 This option causes the contents of the message log spool file to be written to
4029 the standard output. This option can be used only by an admin user.
4030
4031 .vitem &%-m%&
4032 .oindex "&%-m%&"
4033 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
4034 treats it that way too.
4035
4036 .vitem &%-N%&
4037 .oindex "&%-N%&"
4038 .cindex "debugging" "&%-N%& option"
4039 .cindex "debugging" "suppressing delivery"
4040 This is a debugging option that inhibits delivery of a message at the transport
4041 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
4042 it just doesn't actually transport the message, but instead behaves as if it
4043 had successfully done so. However, it does not make any updates to the retry
4044 database, and the log entries for deliveries are flagged with &"*>"& rather
4045 than &"=>"&.
4046
4047 Because &%-N%& discards any message to which it applies, only root or the Exim
4048 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
4049 words, an ordinary user can use it only when supplying an incoming message to
4050 which it will apply. Although transportation never fails when &%-N%& is set, an
4051 address may be deferred because of a configuration problem on a transport, or a
4052 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
4053 the message, and applies to any subsequent delivery attempts that may happen
4054 for that message.
4055
4056 .vitem &%-n%&
4057 .oindex "&%-n%&"
4058 This option is interpreted by Sendmail to mean &"no aliasing"&.
4059 For normal modes of operation, it is ignored by Exim.
4060 When combined with &%-bP%& it makes the output more terse (suppresses
4061 option names, environment values and config pretty printing).
4062
4063 .vitem &%-O%&&~<&'data'&>
4064 .oindex "&%-O%&"
4065 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4066 Exim.
4067
4068 .vitem &%-oA%&&~<&'file&~name'&>
4069 .oindex "&%-oA%&"
4070 .cindex "Sendmail compatibility" "&%-oA%& option"
4071 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4072 alternative alias file name. Exim handles &%-bi%& differently; see the
4073 description above.
4074
4075 .vitem &%-oB%&&~<&'n'&>
4076 .oindex "&%-oB%&"
4077 .cindex "SMTP" "passed connection"
4078 .cindex "SMTP" "multiple deliveries"
4079 .cindex "multiple SMTP deliveries"
4080 This is a debugging option which limits the maximum number of messages that can
4081 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4082 transport. If <&'n'&> is omitted, the limit is set to 1.
4083
4084 .vitem &%-odb%&
4085 .oindex "&%-odb%&"
4086 .cindex "background delivery"
4087 .cindex "delivery" "in the background"
4088 This option applies to all modes in which Exim accepts incoming messages,
4089 including the listening daemon. It requests &"background"& delivery of such
4090 messages, which means that the accepting process automatically starts a
4091 delivery process for each message received, but does not wait for the delivery
4092 processes to finish.
4093
4094 When all the messages have been received, the reception process exits,
4095 leaving the delivery processes to finish in their own time. The standard output
4096 and error streams are closed at the start of each delivery process.
4097 This is the default action if none of the &%-od%& options are present.
4098
4099 If one of the queueing options in the configuration file
4100 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4101 overrides it if &%queue_only_override%& is set true, which is the default
4102 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4103
4104 .vitem &%-odf%&
4105 .oindex "&%-odf%&"
4106 .cindex "foreground delivery"
4107 .cindex "delivery" "in the foreground"
4108 This option requests &"foreground"& (synchronous) delivery when Exim has
4109 accepted a locally-generated message. (For the daemon it is exactly the same as
4110 &%-odb%&.) A delivery process is automatically started to deliver the message,
4111 and Exim waits for it to complete before proceeding.
4112
4113 The original Exim reception process does not finish until the delivery
4114 process for the final message has ended. The standard error stream is left open
4115 during deliveries.
4116
4117 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4118 false and one of the queueing options in the configuration file is in effect.
4119
4120 If there is a temporary delivery error during foreground delivery, the
4121 message is left on the queue for later delivery, and the original reception
4122 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4123 restricted configuration that never queues messages.
4124
4125
4126 .vitem &%-odi%&
4127 .oindex "&%-odi%&"
4128 This option is synonymous with &%-odf%&. It is provided for compatibility with
4129 Sendmail.
4130
4131 .vitem &%-odq%&
4132 .oindex "&%-odq%&"
4133 .cindex "non-immediate delivery"
4134 .cindex "delivery" "suppressing immediate"
4135 .cindex "queueing incoming messages"
4136 This option applies to all modes in which Exim accepts incoming messages,
4137 including the listening daemon. It specifies that the accepting process should
4138 not automatically start a delivery process for each message received. Messages
4139 are placed on the queue, and remain there until a subsequent queue runner
4140 process encounters them. There are several configuration options (such as
4141 &%queue_only%&) that can be used to queue incoming messages under certain
4142 conditions. This option overrides all of them and also &%-odqs%&. It always
4143 forces queueing.
4144
4145 .vitem &%-odqs%&
4146 .oindex "&%-odqs%&"
4147 .cindex "SMTP" "delaying delivery"
4148 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4149 However, like &%-odb%& and &%-odi%&, this option has no effect if
4150 &%queue_only_override%& is false and one of the queueing options in the
4151 configuration file is in effect.
4152
4153 When &%-odqs%& does operate, a delivery process is started for each incoming
4154 message, in the background by default, but in the foreground if &%-odi%& is
4155 also present. The recipient addresses are routed, and local deliveries are done
4156 in the normal way. However, if any SMTP deliveries are required, they are not
4157 done at this time, so the message remains on the queue until a subsequent queue
4158 runner process encounters it. Because routing was done, Exim knows which
4159 messages are waiting for which hosts, and so a number of messages for the same
4160 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4161 configuration option has the same effect for specific domains. See also the
4162 &%-qq%& option.
4163
4164 .vitem &%-oee%&
4165 .oindex "&%-oee%&"
4166 .cindex "error" "reporting"
4167 If an error is detected while a non-SMTP message is being received (for
4168 example, a malformed address), the error is reported to the sender in a mail
4169 message.
4170
4171 .cindex "return code" "for &%-oee%&"
4172 Provided
4173 this error message is successfully sent, the Exim receiving process
4174 exits with a return code of zero. If not, the return code is 2 if the problem
4175 is that the original message has no recipients, or 1 for any other error.
4176 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4177
4178 .vitem &%-oem%&
4179 .oindex "&%-oem%&"
4180 .cindex "error" "reporting"
4181 .cindex "return code" "for &%-oem%&"
4182 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4183 return code, whether or not the error message was successfully sent.
4184 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4185
4186 .vitem &%-oep%&
4187 .oindex "&%-oep%&"
4188 .cindex "error" "reporting"
4189 If an error is detected while a non-SMTP message is being received, the
4190 error is reported by writing a message to the standard error file (stderr).
4191 .cindex "return code" "for &%-oep%&"
4192 The return code is 1 for all errors.
4193
4194 .vitem &%-oeq%&
4195 .oindex "&%-oeq%&"
4196 .cindex "error" "reporting"
4197 This option is supported for compatibility with Sendmail, but has the same
4198 effect as &%-oep%&.
4199
4200 .vitem &%-oew%&
4201 .oindex "&%-oew%&"
4202 .cindex "error" "reporting"
4203 This option is supported for compatibility with Sendmail, but has the same
4204 effect as &%-oem%&.
4205
4206 .vitem &%-oi%&
4207 .oindex "&%-oi%&"
4208 .cindex "dot" "in incoming non-SMTP message"
4209 This option, which has the same effect as &%-i%&, specifies that a dot on a
4210 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4211 single dot does terminate, though Exim does no special processing for other
4212 lines that start with a dot. This option is set by default if Exim is called as
4213 &'rmail'&. See also &%-ti%&.
4214
4215 .vitem &%-oitrue%&
4216 .oindex "&%-oitrue%&"
4217 This option is treated as synonymous with &%-oi%&.
4218
4219 .vitem &%-oMa%&&~<&'host&~address'&>
4220 .oindex "&%-oMa%&"
4221 .cindex "sender" "host address, specifying for local message"
4222 A number of options starting with &%-oM%& can be used to set values associated
4223 with remote hosts on locally-submitted messages (that is, messages not received
4224 over TCP/IP). These options can be used by any caller in conjunction with the
4225 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4226 other circumstances, they are ignored unless the caller is trusted.
4227
4228 The &%-oMa%& option sets the sender host address. This may include a port
4229 number at the end, after a full stop (period). For example:
4230 .code
4231 exim -bs -oMa 10.9.8.7.1234
4232 .endd
4233 An alternative syntax is to enclose the IP address in square brackets,
4234 followed by a colon and the port number:
4235 .code
4236 exim -bs -oMa [10.9.8.7]:1234
4237 .endd
4238 The IP address is placed in the &$sender_host_address$& variable, and the
4239 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4240 are present on the command line, the sender host IP address is taken from
4241 whichever one is last.
4242
4243 .vitem &%-oMaa%&&~<&'name'&>
4244 .oindex "&%-oMaa%&"
4245 .cindex "authentication" "name, specifying for local message"
4246 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4247 option sets the value of &$sender_host_authenticated$& (the authenticator
4248 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4249 This option can be used with &%-bh%& and &%-bs%& to set up an
4250 authenticated SMTP session without actually using the SMTP AUTH command.
4251
4252 .vitem &%-oMai%&&~<&'string'&>
4253 .oindex "&%-oMai%&"
4254 .cindex "authentication" "id, specifying for local message"
4255 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4256 option sets the value of &$authenticated_id$& (the id that was authenticated).
4257 This overrides the default value (the caller's login id, except with &%-bh%&,
4258 where there is no default) for messages from local sources. See chapter
4259 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4260
4261 .vitem &%-oMas%&&~<&'address'&>
4262 .oindex "&%-oMas%&"
4263 .cindex "authentication" "sender, specifying for local message"
4264 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4265 option sets the authenticated sender value in &$authenticated_sender$&. It
4266 overrides the sender address that is created from the caller's login id for
4267 messages from local sources, except when &%-bh%& is used, when there is no
4268 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4269 specified on a MAIL command overrides this value. See chapter
4270 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4271
4272 .vitem &%-oMi%&&~<&'interface&~address'&>
4273 .oindex "&%-oMi%&"
4274 .cindex "interface" "address, specifying for local message"
4275 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4276 option sets the IP interface address value. A port number may be included,
4277 using the same syntax as for &%-oMa%&. The interface address is placed in
4278 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4279
4280 .vitem &%-oMm%&&~<&'message&~reference'&>
4281 .oindex "&%-oMm%&"
4282 .cindex "message reference" "message reference, specifying for local message"
4283 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4284 option sets the message reference, e.g. message-id, and is logged during
4285 delivery. This is useful when some kind of audit trail is required to tie
4286 messages together. The format of the message reference is checked and will
4287 abort if the format is invalid. The option will only be accepted if exim is
4288 running in trusted mode, not as any regular user.
4289
4290 The best example of a message reference is when Exim sends a bounce message.
4291 The message reference is the message-id of the original message for which Exim
4292 is sending the bounce.
4293
4294 .vitem &%-oMr%&&~<&'protocol&~name'&>
4295 .oindex "&%-oMr%&"
4296 .cindex "protocol, specifying for local message"
4297 .vindex "&$received_protocol$&"
4298 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4299 option sets the received protocol value that is stored in
4300 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4301 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4302 SMTP protocol names (see the description of &$received_protocol$& in section
4303 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4304 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4305 be set by &%-oMr%&. Repeated use of this option is not supported.
4306
4307 .vitem &%-oMs%&&~<&'host&~name'&>
4308 .oindex "&%-oMs%&"
4309 .cindex "sender" "host name, specifying for local message"
4310 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4311 option sets the sender host name in &$sender_host_name$&. When this option is
4312 present, Exim does not attempt to look up a host name from an IP address; it
4313 uses the name it is given.
4314
4315 .vitem &%-oMt%&&~<&'ident&~string'&>
4316 .oindex "&%-oMt%&"
4317 .cindex "sender" "ident string, specifying for local message"
4318 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4319 option sets the sender ident value in &$sender_ident$&. The default setting for
4320 local callers is the login id of the calling process, except when &%-bh%& is
4321 used, when there is no default.
4322
4323 .vitem &%-om%&
4324 .oindex "&%-om%&"
4325 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4326 In Sendmail, this option means &"me too"&, indicating that the sender of a
4327 message should receive a copy of the message if the sender appears in an alias
4328 expansion. Exim always does this, so the option does nothing.
4329
4330 .vitem &%-oo%&
4331 .oindex "&%-oo%&"
4332 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4333 This option is ignored. In Sendmail it specifies &"old style headers"&,
4334 whatever that means.
4335
4336 .vitem &%-oP%&&~<&'path'&>
4337 .oindex "&%-oP%&"
4338 .cindex "pid (process id)" "of daemon"
4339 .cindex "daemon" "process id (pid)"
4340 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4341 value. The option specifies the file to which the process id of the daemon is
4342 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4343 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4344 because in those cases, the normal pid file is not used.
4345
4346 .vitem &%-or%&&~<&'time'&>
4347 .oindex "&%-or%&"
4348 .cindex "timeout" "for non-SMTP input"
4349 This option sets a timeout value for incoming non-SMTP messages. If it is not
4350 set, Exim will wait forever for the standard input. The value can also be set
4351 by the &%receive_timeout%& option. The format used for specifying times is
4352 described in section &<<SECTtimeformat>>&.
4353
4354 .vitem &%-os%&&~<&'time'&>
4355 .oindex "&%-os%&"
4356 .cindex "timeout" "for SMTP input"
4357 .cindex "SMTP" "input timeout"
4358 This option sets a timeout value for incoming SMTP messages. The timeout
4359 applies to each SMTP command and block of data. The value can also be set by
4360 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4361 for specifying times is described in section &<<SECTtimeformat>>&.
4362
4363 .vitem &%-ov%&
4364 .oindex "&%-ov%&"
4365 This option has exactly the same effect as &%-v%&.
4366
4367 .vitem &%-oX%&&~<&'number&~or&~string'&>
4368 .oindex "&%-oX%&"
4369 .cindex "TCP/IP" "setting listening ports"
4370 .cindex "TCP/IP" "setting listening interfaces"
4371 .cindex "port" "receiving TCP/IP"
4372 This option is relevant only when the &%-bd%& (start listening daemon) option
4373 is also given. It controls which ports and interfaces the daemon uses. Details
4374 of the syntax, and how it interacts with configuration file options, are given
4375 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4376 file is written unless &%-oP%& is also present to specify a pid file name.
4377
4378 .vitem &%-pd%&
4379 .oindex "&%-pd%&"
4380 .cindex "Perl" "starting the interpreter"
4381 This option applies when an embedded Perl interpreter is linked with Exim (see
4382 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4383 option, forcing the starting of the interpreter to be delayed until it is
4384 needed.
4385
4386 .vitem &%-ps%&
4387 .oindex "&%-ps%&"
4388 .cindex "Perl" "starting the interpreter"
4389 This option applies when an embedded Perl interpreter is linked with Exim (see
4390 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4391 option, forcing the starting of the interpreter to occur as soon as Exim is
4392 started.
4393
4394 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4395 .oindex "&%-p%&"
4396 For compatibility with Sendmail, this option is equivalent to
4397 .display
4398 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4399 .endd
4400 It sets the incoming protocol and host name (for trusted callers). The
4401 host name and its colon can be omitted when only the protocol is to be set.
4402 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4403 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4404 or &`s`& using this option (but that does not seem a real limitation).
4405 Repeated use of this option is not supported.
4406
4407 .vitem &%-q%&
4408 .oindex "&%-q%&"
4409 .cindex "queue runner" "starting manually"
4410 This option is normally restricted to admin users. However, there is a
4411 configuration option called &%prod_requires_admin%& which can be set false to
4412 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4413 and &%-S%& options).
4414
4415 .cindex "queue runner" "description of operation"
4416 If other commandline options do not specify an action,
4417 the &%-q%& option starts one queue runner process. This scans the queue of
4418 waiting messages, and runs a delivery process for each one in turn. It waits
4419 for each delivery process to finish before starting the next one. A delivery
4420 process may not actually do any deliveries if the retry times for the addresses
4421 have not been reached. Use &%-qf%& (see below) if you want to override this.
4422
4423 If
4424 .cindex "SMTP" "passed connection"
4425 .cindex "SMTP" "multiple deliveries"
4426 .cindex "multiple SMTP deliveries"
4427 the delivery process spawns other processes to deliver other messages down
4428 passed SMTP connections, the queue runner waits for these to finish before
4429 proceeding.
4430
4431 When all the queued messages have been considered, the original queue runner
4432 process terminates. In other words, a single pass is made over the waiting
4433 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4434 this to be repeated periodically.
4435
4436 Exim processes the waiting messages in an unpredictable order. It isn't very
4437 random, but it is likely to be different each time, which is all that matters.
4438 If one particular message screws up a remote MTA, other messages to the same
4439 MTA have a chance of getting through if they get tried first.
4440
4441 It is possible to cause the messages to be processed in lexical message id
4442 order, which is essentially the order in which they arrived, by setting the
4443 &%queue_run_in_order%& option, but this is not recommended for normal use.
4444
4445 .vitem &%-q%&<&'qflags'&>
4446 The &%-q%& option may be followed by one or more flag letters that change its
4447 behaviour. They are all optional, but if more than one is present, they must
4448 appear in the correct order. Each flag is described in a separate item below.
4449
4450 .vitem &%-qq...%&
4451 .oindex "&%-qq%&"
4452 .cindex "queue" "double scanning"
4453 .cindex "queue" "routing"
4454 .cindex "routing" "whole queue before delivery"
4455 An option starting with &%-qq%& requests a two-stage queue run. In the first
4456 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4457 every domain. Addresses are routed, local deliveries happen, but no remote
4458 transports are run.
4459
4460 .cindex "hints database" "remembering routing"
4461 The hints database that remembers which messages are waiting for specific hosts
4462 is updated, as if delivery to those hosts had been deferred. After this is
4463 complete, a second, normal queue scan happens, with routing and delivery taking
4464 place as normal. Messages that are routed to the same host should mostly be
4465 delivered down a single SMTP
4466 .cindex "SMTP" "passed connection"
4467 .cindex "SMTP" "multiple deliveries"
4468 .cindex "multiple SMTP deliveries"
4469 connection because of the hints that were set up during the first queue scan.
4470 This option may be useful for hosts that are connected to the Internet
4471 intermittently.
4472
4473 .vitem &%-q[q]i...%&
4474 .oindex "&%-qi%&"
4475 .cindex "queue" "initial delivery"
4476 If the &'i'& flag is present, the queue runner runs delivery processes only for
4477 those messages that haven't previously been tried. (&'i'& stands for &"initial
4478 delivery"&.) This can be helpful if you are putting messages on the queue using
4479 &%-odq%& and want a queue runner just to process the new messages.
4480
4481 .vitem &%-q[q][i]f...%&
4482 .oindex "&%-qf%&"
4483 .cindex "queue" "forcing delivery"
4484 .cindex "delivery" "forcing in queue run"
4485 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4486 message, whereas without &'f'& only those non-frozen addresses that have passed
4487 their retry times are tried.
4488
4489 .vitem &%-q[q][i]ff...%&
4490 .oindex "&%-qff%&"
4491 .cindex "frozen messages" "forcing delivery"
4492 If &'ff'& is present, a delivery attempt is forced for every message, whether
4493 frozen or not.
4494
4495 .vitem &%-q[q][i][f[f]]l%&
4496 .oindex "&%-ql%&"
4497 .cindex "queue" "local deliveries only"
4498 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4499 be done. If a message requires any remote deliveries, it remains on the queue
4500 for later delivery.
4501
4502 .vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
4503 .oindex "&%-qG%&"
4504 .cindex queue named
4505 .cindex "named queues"
4506 .cindex "queue" "delivering specific messages"
4507 If the &'G'& flag and a name is present, the queue runner operates on the
4508 queue with the given name rather than the default queue.
4509 The name should not contain a &'/'& character.
4510 For a periodic queue run (see below)
4511 append to the name a slash and a time value.
4512
4513 If other commandline options specify an action, a &'-qG<name>'& option
4514 will specify a queue to operate on.
4515 For example:
4516 .code
4517 exim -bp -qGquarantine
4518 mailq -qGquarantine
4519 exim -qGoffpeak -Rf @special.domain.example
4520 .endd
4521
4522 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4523 When scanning the queue, Exim can be made to skip over messages whose ids are
4524 lexically less than a given value by following the &%-q%& option with a
4525 starting message id. For example:
4526 .code
4527 exim -q 0t5C6f-0000c8-00
4528 .endd
4529 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4530 second message id is given, messages whose ids are lexically greater than it
4531 are also skipped. If the same id is given twice, for example,
4532 .code
4533 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4534 .endd
4535 just one delivery process is started, for that message. This differs from
4536 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4537 that it counts as a delivery from a queue run. Note that the selection
4538 mechanism does not affect the order in which the messages are scanned. There
4539 are also other ways of selecting specific sets of messages for delivery in a
4540 queue run &-- see &%-R%& and &%-S%&.
4541
4542 .vitem &%-q%&<&'qflags'&><&'time'&>
4543 .cindex "queue runner" "starting periodically"
4544 .cindex "periodic queue running"
4545 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4546 starting a queue runner process at intervals specified by the given time value
4547 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4548 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4549 single daemon process handles both functions. A common way of starting up a
4550 combined daemon at system boot time is to use a command such as
4551 .code
4552 /usr/exim/bin/exim -bd -q30m
4553 .endd
4554 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4555 process every 30 minutes.
4556
4557 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4558 pid file is written unless one is explicitly requested by the &%-oP%& option.
4559
4560 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4561 .oindex "&%-qR%&"
4562 This option is synonymous with &%-R%&. It is provided for Sendmail
4563 compatibility.
4564
4565 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4566 .oindex "&%-qS%&"
4567 This option is synonymous with &%-S%&.
4568
4569 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4570 .oindex "&%-R%&"
4571 .cindex "queue runner" "for specific recipients"
4572 .cindex "delivery" "to given domain"
4573 .cindex "domain" "delivery to"
4574 The <&'rsflags'&> may be empty, in which case the white space before the string
4575 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4576 which are the possible values for <&'rsflags'&>. White space is required if
4577 <&'rsflags'&> is not empty.
4578
4579 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4580 perform a single queue run, except that, when scanning the messages on the
4581 queue, Exim processes only those that have at least one undelivered recipient
4582 address containing the given string, which is checked in a case-independent
4583 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4584 regular expression; otherwise it is a literal string.
4585
4586 If you want to do periodic queue runs for messages with specific recipients,
4587 you can combine &%-R%& with &%-q%& and a time value. For example:
4588 .code
4589 exim -q25m -R @special.domain.example
4590 .endd
4591 This example does a queue run for messages with recipients in the given domain
4592 every 25 minutes. Any additional flags that are specified with &%-q%& are
4593 applied to each queue run.
4594
4595 Once a message is selected for delivery by this mechanism, all its addresses
4596 are processed. For the first selected message, Exim overrides any retry
4597 information and forces a delivery attempt for each undelivered address. This
4598 means that if delivery of any address in the first message is successful, any
4599 existing retry information is deleted, and so delivery attempts for that
4600 address in subsequently selected messages (which are processed without forcing)
4601 will run. However, if delivery of any address does not succeed, the retry
4602 information is updated, and in subsequently selected messages, the failing
4603 address will be skipped.
4604
4605 .cindex "frozen messages" "forcing delivery"
4606 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4607 all selected messages, not just the first; frozen messages are included when
4608 &'ff'& is present.
4609
4610 The &%-R%& option makes it straightforward to initiate delivery of all messages
4611 to a given domain after a host has been down for some time. When the SMTP
4612 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4613 effect is to run Exim with the &%-R%& option, but it can be configured to run
4614 an arbitrary command instead.
4615
4616 .vitem &%-r%&
4617 .oindex "&%-r%&"
4618 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4619
4620 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4621 .oindex "&%-S%&"
4622 .cindex "delivery" "from given sender"
4623 .cindex "queue runner" "for specific senders"
4624 This option acts like &%-R%& except that it checks the string against each
4625 message's sender instead of against the recipients. If &%-R%& is also set, both
4626 conditions must be met for a message to be selected. If either of the options
4627 has &'f'& or &'ff'& in its flags, the associated action is taken.
4628
4629 .vitem &%-Tqt%&&~<&'times'&>
4630 .oindex "&%-Tqt%&"
4631 This is an option that is exclusively for use by the Exim testing suite. It is not
4632 recognized when Exim is run normally. It allows for the setting up of explicit
4633 &"queue times"& so that various warning/retry features can be tested.
4634
4635 .vitem &%-t%&
4636 .oindex "&%-t%&"
4637 .cindex "recipient" "extracting from header lines"
4638 .cindex "&'Bcc:'& header line"
4639 .cindex "&'Cc:'& header line"
4640 .cindex "&'To:'& header line"
4641 When Exim is receiving a locally-generated, non-SMTP message on its standard
4642 input, the &%-t%& option causes the recipients of the message to be obtained
4643 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4644 from the command arguments. The addresses are extracted before any rewriting
4645 takes place and the &'Bcc:'& header line, if present, is then removed.
4646
4647 .cindex "Sendmail compatibility" "&%-t%& option"
4648 If the command has any arguments, they specify addresses to which the message
4649 is &'not'& to be delivered. That is, the argument addresses are removed from
4650 the recipients list obtained from the headers. This is compatible with Smail 3
4651 and in accordance with the documented behaviour of several versions of
4652 Sendmail, as described in man pages on a number of operating systems (e.g.
4653 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4654 argument addresses to those obtained from the headers, and the O'Reilly
4655 Sendmail book documents it that way. Exim can be made to add argument addresses
4656 instead of subtracting them by setting the option
4657 &%extract_addresses_remove_arguments%& false.
4658
4659 .cindex "&%Resent-%& header lines" "with &%-t%&"
4660 If there are any &%Resent-%& header lines in the message, Exim extracts
4661 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4662 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4663 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4664 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4665
4666 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4667 message is resent several times). The RFC also specifies that they should be
4668 added at the front of the message, and separated by &'Received:'& lines. It is
4669 not at all clear how &%-t%& should operate in the present of multiple sets,
4670 nor indeed exactly what constitutes a &"set"&.
4671 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4672 are often added at the end of the header, and if a message is resent more than
4673 once, it is common for the original set of &%Resent-%& headers to be renamed as
4674 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4675
4676 .vitem &%-ti%&
4677 .oindex "&%-ti%&"
4678 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4679 compatibility with Sendmail.
4680
4681 .vitem &%-tls-on-connect%&
4682 .oindex "&%-tls-on-connect%&"
4683 .cindex "TLS" "use without STARTTLS"
4684 .cindex "TLS" "automatic start"
4685 This option is available when Exim is compiled with TLS support. It forces all
4686 incoming SMTP connections to behave as if the incoming port is listed in the
4687 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4688 &<<CHAPTLS>>& for further details.
4689
4690
4691 .vitem &%-U%&
4692 .oindex "&%-U%&"
4693 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4694 Sendmail uses this option for &"initial message submission"&, and its
4695 documentation states that in future releases, it may complain about
4696 syntactically invalid messages rather than fixing them when this flag is not
4697 set. Exim ignores this option.
4698
4699 .vitem &%-v%&
4700 .oindex "&%-v%&"
4701 This option causes Exim to write information to the standard error stream,
4702 describing what it is doing. In particular, it shows the log lines for
4703 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4704 dialogue is shown. Some of the log lines shown may not actually be written to
4705 the log if the setting of &%log_selector%& discards them. Any relevant
4706 selectors are shown with each log line. If none are shown, the logging is
4707 unconditional.
4708
4709 .vitem &%-x%&
4710 .oindex "&%-x%&"
4711 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4712 National Language Support extended characters in the body of the mail item"&).
4713 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4714 this option.
4715
4716 .vitem &%-X%&&~<&'logfile'&>
4717 .oindex "&%-X%&"
4718 This option is interpreted by Sendmail to cause debug information to be sent
4719 to the named file. It is ignored by Exim.
4720
4721 .vitem &%-z%&&~<&'log-line'&>
4722 .oindex "&%-z%&"
4723 This option writes its argument to Exim's logfile.
4724 Use is restricted to administrators; the intent is for operational notes.
4725 Quotes should be used to maintain a multi-word item as a single argument,
4726 under most shells.
4727 .endlist
4728
4729 .ecindex IIDclo1
4730 .ecindex IIDclo2
4731
4732
4733 . ////////////////////////////////////////////////////////////////////////////
4734 . Insert a stylized DocBook comment here, to identify the end of the command
4735 . line options. This is for the benefit of the Perl script that automatically
4736 . creates a man page for the options.
4737 . ////////////////////////////////////////////////////////////////////////////
4738
4739 .literal xml
4740 <!-- === End of command line options === -->
4741 .literal off
4742
4743
4744
4745
4746
4747 . ////////////////////////////////////////////////////////////////////////////
4748 . ////////////////////////////////////////////////////////////////////////////
4749
4750
4751 .chapter "The Exim run time configuration file" "CHAPconf" &&&
4752 "The runtime configuration file"
4753
4754 .cindex "run time configuration"
4755 .cindex "configuration file" "general description"
4756 .cindex "CONFIGURE_FILE"
4757 .cindex "configuration file" "errors in"
4758 .cindex "error" "in configuration file"
4759 .cindex "return code" "for bad configuration"
4760 Exim uses a single run time configuration file that is read whenever an Exim
4761 binary is executed. Note that in normal operation, this happens frequently,
4762 because Exim is designed to operate in a distributed manner, without central
4763 control.
4764
4765 If a syntax error is detected while reading the configuration file, Exim
4766 writes a message on the standard error, and exits with a non-zero return code.
4767 The message is also written to the panic log. &*Note*&: Only simple syntax
4768 errors can be detected at this time. The values of any expanded options are
4769 not checked until the expansion happens, even when the expansion does not
4770 actually alter the string.
4771
4772 The name of the configuration file is compiled into the binary for security
4773 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4774 most configurations, this specifies a single file. However, it is permitted to
4775 give a colon-separated list of file names, in which case Exim uses the first
4776 existing file in the list.
4777
4778 .cindex "EXIM_USER"
4779 .cindex "EXIM_GROUP"
4780 .cindex "CONFIGURE_OWNER"
4781 .cindex "CONFIGURE_GROUP"
4782 .cindex "configuration file" "ownership"
4783 .cindex "ownership" "configuration file"
4784 The run time configuration file must be owned by root or by the user that is
4785 specified at compile time by the CONFIGURE_OWNER option (if set). The
4786 configuration file must not be world-writeable, or group-writeable unless its
4787 group is the root group or the one specified at compile time by the
4788 CONFIGURE_GROUP option.
4789
4790 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4791 to root, anybody who is able to edit the run time configuration file has an
4792 easy way to run commands as root. If you specify a user or group in the
4793 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4794 who are members of that group will trivially be able to obtain root privileges.
4795
4796 Up to Exim version 4.72, the run time configuration file was also permitted to
4797 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4798 since it offered a simple privilege escalation for any attacker who managed to
4799 compromise the Exim user account.
4800
4801 A default configuration file, which will work correctly in simple situations,
4802 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4803 defines just one file name, the installation process copies the default
4804 configuration to a new file of that name if it did not previously exist. If
4805 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4806 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4807 configuration.
4808
4809
4810
4811 .section "Using a different configuration file" "SECID40"
4812 .cindex "configuration file" "alternate"
4813 A one-off alternate configuration can be specified by the &%-C%& command line
4814 option, which may specify a single file or a list of files. However, when
4815 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4816 unless the argument for &%-C%& is identical to the built-in value from
4817 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4818 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4819 is useful mainly for checking the syntax of configuration files before
4820 installing them. No owner or group checks are done on a configuration file
4821 specified by &%-C%&, if root privilege has been dropped.
4822
4823 Even the Exim user is not trusted to specify an arbitrary configuration file
4824 with the &%-C%& option to be used with root privileges, unless that file is
4825 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
4826 testing a configuration using &%-C%& right through message reception and
4827 delivery, even if the caller is root. The reception works, but by that time,
4828 Exim is running as the Exim user, so when it re-execs to regain privilege for
4829 the delivery, the use of &%-C%& causes privilege to be lost. However, root
4830 can test reception and delivery using two separate commands (one to put a
4831 message on the queue, using &%-odq%&, and another to do the delivery, using
4832 &%-M%&).
4833
4834 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4835 prefix string with which any file named in a &%-C%& command line option must
4836 start. In addition, the file name must not contain the sequence &"&`/../`&"&.
4837 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any file
4838 name can be used with &%-C%&.
4839
4840 One-off changes to a configuration can be specified by the &%-D%& command line
4841 option, which defines and overrides values for macros used inside the
4842 configuration file. However, like &%-C%&, the use of this option by a
4843 non-privileged user causes Exim to discard its root privilege.
4844 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4845 completely disabled, and its use causes an immediate error exit.
4846
4847 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
4848 to declare certain macro names trusted, such that root privilege will not
4849 necessarily be discarded.
4850 WHITELIST_D_MACROS defines a colon-separated list of macros which are
4851 considered safe and, if &%-D%& only supplies macros from this list, and the
4852 values are acceptable, then Exim will not give up root privilege if the caller
4853 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
4854 transition mechanism and is expected to be removed in the future. Acceptable
4855 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
4856
4857 Some sites may wish to use the same Exim binary on different machines that
4858 share a file system, but to use different configuration files on each machine.
4859 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4860 looks for a file whose name is the configuration file name followed by a dot
4861 and the machine's node name, as obtained from the &[uname()]& function. If this
4862 file does not exist, the standard name is tried. This processing occurs for
4863 each file name in the list given by CONFIGURE_FILE or &%-C%&.
4864
4865 In some esoteric situations different versions of Exim may be run under
4866 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4867 help with this. See the comments in &_src/EDITME_& for details.
4868
4869
4870
4871 .section "Configuration file format" "SECTconffilfor"
4872 .cindex "configuration file" "format of"
4873 .cindex "format" "configuration file"
4874 Exim's configuration file is divided into a number of different parts. General
4875 option settings must always appear at the start of the file. The other parts
4876 are all optional, and may appear in any order. Each part other than the first
4877 is introduced by the word &"begin"& followed by at least one literal
4878 space, and the name of the part. The optional parts are:
4879
4880 .ilist
4881 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
4882 &<<CHAPACL>>&).
4883 .next
4884 .cindex "AUTH" "configuration"
4885 &'authenticators'&: Configuration settings for the authenticator drivers. These
4886 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4887 .next
4888 &'routers'&: Configuration settings for the router drivers. Routers process
4889 addresses and determine how the message is to be delivered (see chapters
4890 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
4891 .next
4892 &'transports'&: Configuration settings for the transport drivers. Transports
4893 define mechanisms for copying messages to destinations (see chapters
4894 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
4895 .next
4896 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
4897 If there is no retry section, or if it is empty (that is, no retry rules are
4898 defined), Exim will not retry deliveries. In this situation, temporary errors
4899 are treated the same as permanent errors. Retry rules are discussed in chapter
4900 &<<CHAPretry>>&.
4901 .next
4902 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4903 when new addresses are generated during delivery. Rewriting is discussed in
4904 chapter &<<CHAPrewrite>>&.
4905 .next
4906 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4907 want to use this feature, you must set
4908 .code
4909 LOCAL_SCAN_HAS_OPTIONS=yes
4910 .endd
4911 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
4912 facility are given in chapter &<<CHAPlocalscan>>&.
4913 .endlist
4914
4915 .cindex "configuration file" "leading white space in"
4916 .cindex "configuration file" "trailing white space in"
4917 .cindex "white space" "in configuration file"
4918 Leading and trailing white space in configuration lines is always ignored.
4919
4920 Blank lines in the file, and lines starting with a # character (ignoring
4921 leading white space) are treated as comments and are ignored. &*Note*&: A
4922 # character other than at the beginning of a line is not treated specially,
4923 and does not introduce a comment.
4924
4925 Any non-comment line can be continued by ending it with a backslash. Note that
4926 the general rule for white space means that trailing white space after the
4927 backslash and leading white space at the start of continuation
4928 lines is ignored. Comment lines beginning with # (but not empty lines) may
4929 appear in the middle of a sequence of continuation lines.
4930
4931 A convenient way to create a configuration file is to start from the
4932 default, which is supplied in &_src/configure.default_&, and add, delete, or
4933 change settings as required.
4934
4935 The ACLs, retry rules, and rewriting rules have their own syntax which is
4936 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
4937 respectively. The other parts of the configuration file have some syntactic
4938 items in common, and these are described below, from section &<<SECTcos>>&
4939 onwards. Before that, the inclusion, macro, and conditional facilities are
4940 described.
4941
4942
4943
4944 .section "File inclusions in the configuration file" "SECID41"
4945 .cindex "inclusions in configuration file"
4946 .cindex "configuration file" "including other files"
4947 .cindex "&`.include`& in configuration file"
4948 .cindex "&`.include_if_exists`& in configuration file"
4949 You can include other files inside Exim's run time configuration file by
4950 using this syntax:
4951 .display
4952 &`.include`& <&'file name'&>
4953 &`.include_if_exists`& <&'file name'&>
4954 .endd
4955 on a line by itself. Double quotes round the file name are optional. If you use
4956 the first form, a configuration error occurs if the file does not exist; the
4957 second form does nothing for non-existent files.
4958 The first form allows a relative name. It is resolved relative to
4959 the directory of the including file. For the second form an absolute file
4960 name is required.
4961
4962 Includes may be nested to any depth, but remember that Exim reads its
4963 configuration file often, so it is a good idea to keep them to a minimum.
4964 If you change the contents of an included file, you must HUP the daemon,
4965 because an included file is read only when the configuration itself is read.
4966
4967 The processing of inclusions happens early, at a physical line level, so, like
4968 comment lines, an inclusion can be used in the middle of an option setting,
4969 for example:
4970 .code
4971 hosts_lookup = a.b.c \
4972 .include /some/file
4973 .endd
4974 Include processing happens after macro processing (see below). Its effect is to
4975 process the lines of the included file as if they occurred inline where the
4976 inclusion appears.
4977
4978
4979
4980 .section "Macros in the configuration file" "SECTmacrodefs"
4981 .cindex "macro" "description of"
4982 .cindex "configuration file" "macros"
4983 If a line in the main part of the configuration (that is, before the first
4984 &"begin"& line) begins with an upper case letter, it is taken as a macro
4985 definition, and must be of the form
4986 .display
4987 <&'name'&> = <&'rest of line'&>
4988 .endd
4989 The name must consist of letters, digits, and underscores, and need not all be
4990 in upper case, though that is recommended. The rest of the line, including any
4991 continuations, is the replacement text, and has leading and trailing white
4992 space removed. Quotes are not removed. The replacement text can never end with
4993 a backslash character, but this doesn't seem to be a serious limitation.
4994
4995 Macros may also be defined between router, transport, authenticator, or ACL
4996 definitions. They may not, however, be defined within an individual driver or
4997 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
4998
4999 .section "Macro substitution" "SECID42"
5000 Once a macro is defined, all subsequent lines in the file (and any included
5001 files) are scanned for the macro name; if there are several macros, the line is
5002 scanned for each in turn, in the order in which the macros are defined. The
5003 replacement text is not re-scanned for the current macro, though it is scanned
5004 for subsequently defined macros. For this reason, a macro name may not contain
5005 the name of a previously defined macro as a substring. You could, for example,
5006 define
5007 .display
5008 &`ABCD_XYZ = `&<&'something'&>
5009 &`ABCD = `&<&'something else'&>
5010 .endd
5011 but putting the definitions in the opposite order would provoke a configuration
5012 error. Macro expansion is applied to individual physical lines from the file,
5013 before checking for line continuation or file inclusion (see above). If a line
5014 consists solely of a macro name, and the expansion of the macro is empty, the
5015 line is ignored. A macro at the start of a line may turn the line into a
5016 comment line or a &`.include`& line.
5017
5018
5019 .section "Redefining macros" "SECID43"
5020 Once defined, the value of a macro can be redefined later in the configuration
5021 (or in an included file). Redefinition is specified by using &'=='& instead of
5022 &'='&. For example:
5023 .code
5024 MAC = initial value
5025 ...
5026 MAC == updated value
5027 .endd
5028 Redefinition does not alter the order in which the macros are applied to the
5029 subsequent lines of the configuration file. It is still the same order in which
5030 the macros were originally defined. All that changes is the macro's value.
5031 Redefinition makes it possible to accumulate values. For example:
5032 .code
5033 MAC = initial value
5034 ...
5035 MAC == MAC and something added
5036 .endd
5037 This can be helpful in situations where the configuration file is built
5038 from a number of other files.
5039
5040 .section "Overriding macro values" "SECID44"
5041 The values set for macros in the configuration file can be overridden by the
5042 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
5043 used, unless called by root or the Exim user. A definition on the command line
5044 using the &%-D%& option causes all definitions and redefinitions within the
5045 file to be ignored.
5046
5047
5048
5049 .section "Example of macro usage" "SECID45"
5050 As an example of macro usage, consider a configuration where aliases are looked
5051 up in a MySQL database. It helps to keep the file less cluttered if long
5052 strings such as SQL statements are defined separately as macros, for example:
5053 .code
5054 ALIAS_QUERY = select mailbox from user where \
5055 login='${quote_mysql:$local_part}';
5056 .endd
5057 This can then be used in a &(redirect)& router setting like this:
5058 .code
5059 data = ${lookup mysql{ALIAS_QUERY}}
5060 .endd
5061 In earlier versions of Exim macros were sometimes used for domain, host, or
5062 address lists. In Exim 4 these are handled better by named lists &-- see
5063 section &<<SECTnamedlists>>&.
5064
5065
5066 .section "Builtin macros" "SECTbuiltinmacros"
5067 Exim defines some macros depending on facilities available, which may
5068 differ due to build-time definitions and from one release to another.
5069 All of these macros start with an underscore.
5070 They can be used to conditionally include parts of a configuration
5071 (see below).
5072
5073 The following classes of macros are defined:
5074 .display
5075 &` _HAVE_* `& build-time defines
5076 &` _DRIVER_ROUTER_* `& router drivers
5077 &` _DRIVER_TRANSPORT_* `& transport drivers
5078 &` _DRIVER_AUTHENTICATOR_* `& authenticator drivers
5079 &` _LOG_* `& log_selector values
5080 &` _OPT_MAIN_* `& main config options
5081 &` _OPT_ROUTERS_* `& generic router options
5082 &` _OPT_TRANSPORTS_* `& generic transport options
5083 &` _OPT_AUTHENTICATORS_* `& generic authenticator options
5084 &` _OPT_ROUTER_*_* `& private router options
5085 &` _OPT_TRANSPORT_*_* `& private transport options
5086 &` _OPT_AUTHENTICATOR_*_* `& private authenticator options
5087 .endd
5088
5089 Use an &"exim -bP macros"& command to get the list of macros.
5090
5091
5092 .section "Conditional skips in the configuration file" "SECID46"
5093 .cindex "configuration file" "conditional skips"
5094 .cindex "&`.ifdef`&"
5095 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
5096 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
5097 portions of the configuration file. The processing happens whenever the file is
5098 read (that is, when an Exim binary starts to run).
5099
5100 The implementation is very simple. Instances of the first four directives must
5101 be followed by text that includes the names of one or macros. The condition
5102 that is tested is whether or not any macro substitution has taken place in the
5103 line. Thus:
5104 .code
5105 .ifdef AAA
5106 message_size_limit = 50M
5107 .else
5108 message_size_limit = 100M
5109 .endif
5110 .endd
5111 sets a message size limit of 50M if the macro &`AAA`& is defined
5112 (or &`A`& or &`AA`&), and 100M
5113 otherwise. If there is more than one macro named on the line, the condition
5114 is true if any of them are defined. That is, it is an &"or"& condition. To
5115 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5116
5117 Although you can use a macro expansion to generate one of these directives,
5118 it is not very useful, because the condition &"there was a macro substitution
5119 in this line"& will always be true.
5120
5121 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5122 to clarify complicated nestings.
5123
5124
5125
5126 .section "Common option syntax" "SECTcos"
5127 .cindex "common option syntax"
5128 .cindex "syntax of common options"
5129 .cindex "configuration file" "common option syntax"
5130 For the main set of options, driver options, and &[local_scan()]& options,
5131 each setting is on a line by itself, and starts with a name consisting of
5132 lower-case letters and underscores. Many options require a data value, and in
5133 these cases the name must be followed by an equals sign (with optional white
5134 space) and then the value. For example:
5135 .code
5136 qualify_domain = mydomain.example.com
5137 .endd
5138 .cindex "hiding configuration option values"
5139 .cindex "configuration options" "hiding value of"
5140 .cindex "options" "hiding value of"
5141 Some option settings may contain sensitive data, for example, passwords for
5142 accessing databases. To stop non-admin users from using the &%-bP%& command
5143 line option to read these values, you can precede the option settings with the
5144 word &"hide"&. For example:
5145 .code
5146 hide mysql_servers = localhost/users/admin/secret-password
5147 .endd
5148 For non-admin users, such options are displayed like this:
5149 .code
5150 mysql_servers = <value not displayable>
5151 .endd
5152 If &"hide"& is used on a driver option, it hides the value of that option on
5153 all instances of the same driver.
5154
5155 The following sections describe the syntax used for the different data types
5156 that are found in option settings.
5157
5158
5159 .section "Boolean options" "SECID47"
5160 .cindex "format" "boolean"
5161 .cindex "boolean configuration values"
5162 .oindex "&%no_%&&'xxx'&"
5163 .oindex "&%not_%&&'xxx'&"
5164 Options whose type is given as boolean are on/off switches. There are two
5165 different ways of specifying such options: with and without a data value. If
5166 the option name is specified on its own without data, the switch is turned on;
5167 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5168 boolean options may be followed by an equals sign and one of the words
5169 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5170 the following two settings have exactly the same effect:
5171 .code
5172 queue_only
5173 queue_only = true
5174 .endd
5175 The following two lines also have the same (opposite) effect:
5176 .code
5177 no_queue_only
5178 queue_only = false
5179 .endd
5180 You can use whichever syntax you prefer.
5181
5182
5183
5184
5185 .section "Integer values" "SECID48"
5186 .cindex "integer configuration values"
5187 .cindex "format" "integer"
5188 If an option's type is given as &"integer"&, the value can be given in decimal,
5189 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5190 number is assumed. Otherwise, it is treated as an octal number unless it starts
5191 with the characters &"0x"&, in which case the remainder is interpreted as a
5192 hexadecimal number.
5193
5194 If an integer value is followed by the letter K, it is multiplied by 1024; if
5195 it is followed by the letter M, it is multiplied by 1024x1024;
5196 if by the letter G, 1024x1024x1024.
5197 When the values
5198 of integer option settings are output, values which are an exact multiple of
5199 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5200 and M. The printing style is independent of the actual input format that was
5201 used.
5202
5203
5204 .section "Octal integer values" "SECID49"
5205 .cindex "integer format"
5206 .cindex "format" "octal integer"
5207 If an option's type is given as &"octal integer"&, its value is always
5208 interpreted as an octal number, whether or not it starts with the digit zero.
5209 Such options are always output in octal.
5210
5211
5212 .section "Fixed point numbers" "SECID50"
5213 .cindex "fixed point configuration values"
5214 .cindex "format" "fixed point"
5215 If an option's type is given as &"fixed-point"&, its value must be a decimal
5216 integer, optionally followed by a decimal point and up to three further digits.
5217
5218
5219
5220 .section "Time intervals" "SECTtimeformat"
5221 .cindex "time interval" "specifying in configuration"
5222 .cindex "format" "time interval"
5223 A time interval is specified as a sequence of numbers, each followed by one of
5224 the following letters, with no intervening white space:
5225
5226 .table2 30pt
5227 .irow &%s%& seconds
5228 .irow &%m%& minutes
5229 .irow &%h%& hours
5230 .irow &%d%& days
5231 .irow &%w%& weeks
5232 .endtable
5233
5234 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5235 intervals are output in the same format. Exim does not restrict the values; it
5236 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5237
5238
5239
5240 .section "String values" "SECTstrings"
5241 .cindex "string" "format of configuration values"
5242 .cindex "format" "string"
5243 If an option's type is specified as &"string"&, the value can be specified with
5244 or without double-quotes. If it does not start with a double-quote, the value
5245 consists of the remainder of the line plus any continuation lines, starting at
5246 the first character after any leading white space, with trailing white space
5247 removed, and with no interpretation of the characters in the string. Because
5248 Exim removes comment lines (those beginning with #) at an early stage, they can
5249 appear in the middle of a multi-line string. The following two settings are
5250 therefore equivalent:
5251 .code
5252 trusted_users = uucp:mail
5253 trusted_users = uucp:\
5254 # This comment line is ignored
5255 mail
5256 .endd
5257 .cindex "string" "quoted"
5258 .cindex "escape characters in quoted strings"
5259 If a string does start with a double-quote, it must end with a closing
5260 double-quote, and any backslash characters other than those used for line
5261 continuation are interpreted as escape characters, as follows:
5262
5263 .table2 100pt
5264 .irow &`\\`& "single backslash"
5265 .irow &`\n`& "newline"
5266 .irow &`\r`& "carriage return"
5267 .irow &`\t`& "tab"
5268 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5269 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5270 character"
5271 .endtable
5272
5273 If a backslash is followed by some other character, including a double-quote
5274 character, that character replaces the pair.
5275
5276 Quoting is necessary only if you want to make use of the backslash escapes to
5277 insert special characters, or if you need to specify a value with leading or
5278 trailing spaces. These cases are rare, so quoting is almost never needed in
5279 current versions of Exim. In versions of Exim before 3.14, quoting was required
5280 in order to continue lines, so you may come across older configuration files
5281 and examples that apparently quote unnecessarily.
5282
5283
5284 .section "Expanded strings" "SECID51"
5285 .cindex "expansion" "definition of"
5286 Some strings in the configuration file are subjected to &'string expansion'&,
5287 by which means various parts of the string may be changed according to the
5288 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5289 is as just described; in particular, the handling of backslashes in quoted
5290 strings is done as part of the input process, before expansion takes place.
5291 However, backslash is also an escape character for the expander, so any
5292 backslashes that are required for that reason must be doubled if they are
5293 within a quoted configuration string.
5294
5295
5296 .section "User and group names" "SECID52"
5297 .cindex "user name" "format of"
5298 .cindex "format" "user name"
5299 .cindex "groups" "name format"
5300 .cindex "format" "group name"
5301 User and group names are specified as strings, using the syntax described
5302 above, but the strings are interpreted specially. A user or group name must
5303 either consist entirely of digits, or be a name that can be looked up using the
5304 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5305
5306
5307 .section "List construction" "SECTlistconstruct"
5308 .cindex "list" "syntax of in configuration"
5309 .cindex "format" "list item in configuration"
5310 .cindex "string" "list, definition of"
5311 The data for some configuration options is a list of items, with colon as the
5312 default separator. Many of these options are shown with type &"string list"& in
5313 the descriptions later in this document. Others are listed as &"domain list"&,
5314 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5315 are all the same; however, those other than &"string list"& are subject to
5316 particular kinds of interpretation, as described in chapter
5317 &<<CHAPdomhosaddlists>>&.
5318
5319 In all these cases, the entire list is treated as a single string as far as the
5320 input syntax is concerned. The &%trusted_users%& setting in section
5321 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5322 in a list, it must be entered as two colons. Leading and trailing white space
5323 on each item in a list is ignored. This makes it possible to include items that
5324 start with a colon, and in particular, certain forms of IPv6 address. For
5325 example, the list
5326 .code
5327 local_interfaces = 127.0.0.1 : ::::1
5328 .endd
5329 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5330
5331 &*Note*&: Although leading and trailing white space is ignored in individual
5332 list items, it is not ignored when parsing the list. The space after the first
5333 colon in the example above is necessary. If it were not there, the list would
5334 be interpreted as the two items 127.0.0.1:: and 1.
5335
5336 .section "Changing list separators" "SECTlistsepchange"
5337 .cindex "list separator" "changing"
5338 .cindex "IPv6" "addresses in lists"
5339 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5340 introduced to allow the separator character to be changed. If a list begins
5341 with a left angle bracket, followed by any punctuation character, that
5342 character is used instead of colon as the list separator. For example, the list
5343 above can be rewritten to use a semicolon separator like this:
5344 .code
5345 local_interfaces = <; 127.0.0.1 ; ::1
5346 .endd
5347 This facility applies to all lists, with the exception of the list in
5348 &%log_file_path%&. It is recommended that the use of non-colon separators be
5349 confined to circumstances where they really are needed.
5350
5351 .cindex "list separator" "newline as"
5352 .cindex "newline" "as list separator"
5353 It is also possible to use newline and other control characters (those with
5354 code values less than 32, plus DEL) as separators in lists. Such separators
5355 must be provided literally at the time the list is processed. For options that
5356 are string-expanded, you can write the separator using a normal escape
5357 sequence. This will be processed by the expander before the string is
5358 interpreted as a list. For example, if a newline-separated list of domains is
5359 generated by a lookup, you can process it directly by a line such as this:
5360 .code
5361 domains = <\n ${lookup mysql{.....}}
5362 .endd
5363 This avoids having to change the list separator in such data. You are unlikely
5364 to want to use a control character as a separator in an option that is not
5365 expanded, because the value is literal text. However, it can be done by giving
5366 the value in quotes. For example:
5367 .code
5368 local_interfaces = "<\n 127.0.0.1 \n ::1"
5369 .endd
5370 Unlike printing character separators, which can be included in list items by
5371 doubling, it is not possible to include a control character as data when it is
5372 set as the separator. Two such characters in succession are interpreted as
5373 enclosing an empty list item.
5374
5375
5376
5377 .section "Empty items in lists" "SECTempitelis"
5378 .cindex "list" "empty item in"
5379 An empty item at the end of a list is always ignored. In other words, trailing
5380 separator characters are ignored. Thus, the list in
5381 .code
5382 senders = user@domain :
5383 .endd
5384 contains only a single item. If you want to include an empty string as one item
5385 in a list, it must not be the last item. For example, this list contains three
5386 items, the second of which is empty:
5387 .code
5388 senders = user1@domain : : user2@domain
5389 .endd
5390 &*Note*&: There must be white space between the two colons, as otherwise they
5391 are interpreted as representing a single colon data character (and the list
5392 would then contain just one item). If you want to specify a list that contains
5393 just one, empty item, you can do it as in this example:
5394 .code
5395 senders = :
5396 .endd
5397 In this case, the first item is empty, and the second is discarded because it
5398 is at the end of the list.
5399
5400
5401
5402
5403 .section "Format of driver configurations" "SECTfordricon"
5404 .cindex "drivers" "configuration format"
5405 There are separate parts in the configuration for defining routers, transports,
5406 and authenticators. In each part, you are defining a number of driver
5407 instances, each with its own set of options. Each driver instance is defined by
5408 a sequence of lines like this:
5409 .display
5410 <&'instance name'&>:
5411 <&'option'&>
5412 ...
5413 <&'option'&>
5414 .endd
5415 In the following example, the instance name is &(localuser)&, and it is
5416 followed by three options settings:
5417 .code
5418 localuser:
5419 driver = accept
5420 check_local_user
5421 transport = local_delivery
5422 .endd
5423 For each driver instance, you specify which Exim code module it uses &-- by the
5424 setting of the &%driver%& option &-- and (optionally) some configuration
5425 settings. For example, in the case of transports, if you want a transport to
5426 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5427 a local file you would use the &(appendfile)& driver. Each of the drivers is
5428 described in detail in its own separate chapter later in this manual.
5429
5430 You can have several routers, transports, or authenticators that are based on
5431 the same underlying driver (each must have a different instance name).
5432
5433 The order in which routers are defined is important, because addresses are
5434 passed to individual routers one by one, in order. The order in which
5435 transports are defined does not matter at all. The order in which
5436 authenticators are defined is used only when Exim, as a client, is searching
5437 them to find one that matches an authentication mechanism offered by the
5438 server.
5439
5440 .cindex "generic options"
5441 .cindex "options" "generic &-- definition of"
5442 Within a driver instance definition, there are two kinds of option: &'generic'&
5443 and &'private'&. The generic options are those that apply to all drivers of the
5444 same type (that is, all routers, all transports or all authenticators). The
5445 &%driver%& option is a generic option that must appear in every definition.
5446 .cindex "private options"
5447 The private options are special for each driver, and none need appear, because
5448 they all have default values.
5449
5450 The options may appear in any order, except that the &%driver%& option must
5451 precede any private options, since these depend on the particular driver. For
5452 this reason, it is recommended that &%driver%& always be the first option.
5453
5454 Driver instance names, which are used for reference in log entries and
5455 elsewhere, can be any sequence of letters, digits, and underscores (starting
5456 with a letter) and must be unique among drivers of the same type. A router and
5457 a transport (for example) can each have the same name, but no two router
5458 instances can have the same name. The name of a driver instance should not be
5459 confused with the name of the underlying driver module. For example, the
5460 configuration lines:
5461 .code
5462 remote_smtp:
5463 driver = smtp
5464 .endd
5465 create an instance of the &(smtp)& transport driver whose name is
5466 &(remote_smtp)&. The same driver code can be used more than once, with
5467 different instance names and different option settings each time. A second
5468 instance of the &(smtp)& transport, with different options, might be defined
5469 thus:
5470 .code
5471 special_smtp:
5472 driver = smtp
5473 port = 1234
5474 command_timeout = 10s
5475 .endd
5476 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5477 these transport instances from routers, and these names would appear in log
5478 lines.
5479
5480 Comment lines may be present in the middle of driver specifications. The full
5481 list of option settings for any particular driver instance, including all the
5482 defaulted values, can be extracted by making use of the &%-bP%& command line
5483 option.
5484
5485
5486
5487
5488
5489
5490 . ////////////////////////////////////////////////////////////////////////////
5491 . ////////////////////////////////////////////////////////////////////////////
5492
5493 .chapter "The default configuration file" "CHAPdefconfil"
5494 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5495 .cindex "default" "configuration file &""walk through""&"
5496 The default configuration file supplied with Exim as &_src/configure.default_&
5497 is sufficient for a host with simple mail requirements. As an introduction to
5498 the way Exim is configured, this chapter &"walks through"& the default
5499 configuration, giving brief explanations of the settings. Detailed descriptions
5500 of the options are given in subsequent chapters. The default configuration file
5501 itself contains extensive comments about ways you might want to modify the
5502 initial settings. However, note that there are many options that are not
5503 mentioned at all in the default configuration.
5504
5505
5506
5507 .section "Main configuration settings" "SECTdefconfmain"
5508 The main (global) configuration option settings must always come first in the
5509 file. The first thing you'll see in the file, after some initial comments, is
5510 the line
5511 .code
5512 # primary_hostname =
5513 .endd
5514 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5515 to know the official, fully qualified name of your host, and this is where you
5516 can specify it. However, in most cases you do not need to set this option. When
5517 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5518
5519 The first three non-comment configuration lines are as follows:
5520 .code
5521 domainlist local_domains = @
5522 domainlist relay_to_domains =
5523 hostlist relay_from_hosts = 127.0.0.1
5524 .endd
5525 These are not, in fact, option settings. They are definitions of two named
5526 domain lists and one named host list. Exim allows you to give names to lists of
5527 domains, hosts, and email addresses, in order to make it easier to manage the
5528 configuration file (see section &<<SECTnamedlists>>&).
5529
5530 The first line defines a domain list called &'local_domains'&; this is used
5531 later in the configuration to identify domains that are to be delivered
5532 on the local host.
5533
5534 .cindex "@ in a domain list"
5535 There is just one item in this list, the string &"@"&. This is a special form
5536 of entry which means &"the name of the local host"&. Thus, if the local host is
5537 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5538 be delivered locally. Because the local host's name is referenced indirectly,
5539 the same configuration file can be used on different hosts.
5540
5541 The second line defines a domain list called &'relay_to_domains'&, but the
5542 list itself is empty. Later in the configuration we will come to the part that
5543 controls mail relaying through the local host; it allows relaying to any
5544 domains in this list. By default, therefore, no relaying on the basis of a mail
5545 domain is permitted.
5546
5547 The third line defines a host list called &'relay_from_hosts'&. This list is
5548 used later in the configuration to permit relaying from any host or IP address
5549 that matches the list. The default contains just the IP address of the IPv4
5550 loopback interface, which means that processes on the local host are able to
5551 submit mail for relaying by sending it over TCP/IP to that interface. No other
5552 hosts are permitted to submit messages for relaying.
5553
5554 Just to be sure there's no misunderstanding: at this point in the configuration
5555 we aren't actually setting up any controls. We are just defining some domains
5556 and hosts that will be used in the controls that are specified later.
5557
5558 The next two configuration lines are genuine option settings:
5559 .code
5560 acl_smtp_rcpt = acl_check_rcpt
5561 acl_smtp_data = acl_check_data
5562 .endd
5563 These options specify &'Access Control Lists'& (ACLs) that are to be used
5564 during an incoming SMTP session for every recipient of a message (every RCPT
5565 command), and after the contents of the message have been received,
5566 respectively. The names of the lists are &'acl_check_rcpt'& and
5567 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5568 section of the configuration. The RCPT ACL controls which recipients are
5569 accepted for an incoming message &-- if a configuration does not provide an ACL
5570 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5571 contents of a message to be checked.
5572
5573 Two commented-out option settings are next:
5574 .code
5575 # av_scanner = clamd:/tmp/clamd
5576 # spamd_address = 127.0.0.1 783
5577 .endd
5578 These are example settings that can be used when Exim is compiled with the
5579 content-scanning extension. The first specifies the interface to the virus
5580 scanner, and the second specifies the interface to SpamAssassin. Further
5581 details are given in chapter &<<CHAPexiscan>>&.
5582
5583 Three more commented-out option settings follow:
5584 .code
5585 # tls_advertise_hosts = *
5586 # tls_certificate = /etc/ssl/exim.crt
5587 # tls_privatekey = /etc/ssl/exim.pem
5588 .endd
5589 These are example settings that can be used when Exim is compiled with
5590 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5591 first one specifies the list of clients that are allowed to use TLS when
5592 connecting to this server; in this case the wildcard means all clients. The
5593 other options specify where Exim should find its TLS certificate and private
5594 key, which together prove the server's identity to any clients that connect.
5595 More details are given in chapter &<<CHAPTLS>>&.
5596
5597 Another two commented-out option settings follow:
5598 .code
5599 # daemon_smtp_ports = 25 : 465 : 587
5600 # tls_on_connect_ports = 465
5601 .endd
5602 .cindex "port" "465 and 587"
5603 .cindex "port" "for message submission"
5604 .cindex "message" "submission, ports for"
5605 .cindex "submissions protocol"
5606 .cindex "smtps protocol"
5607 .cindex "ssmtp protocol"
5608 .cindex "SMTP" "submissions protocol"
5609 .cindex "SMTP" "ssmtp protocol"
5610 .cindex "SMTP" "smtps protocol"
5611 These options provide better support for roaming users who wish to use this
5612 server for message submission. They are not much use unless you have turned on
5613 TLS (as described in the previous paragraph) and authentication (about which
5614 more in section &<<SECTdefconfauth>>&).
5615 Mail submission from mail clients (MUAs) should be separate from inbound mail
5616 to your domain (MX delivery) for various good reasons (eg, ability to impose
5617 much saner TLS protocol and ciphersuite requirements without unintended
5618 consequences).
5619 RFC 6409 (previously 4409) specifies use of port 587 for SMTP Submission,
5620 which uses STARTTLS, so this is the &"submission"& port.
5621 RFC 8314 specifies use of port 465 as the &"submissions"& protocol,
5622 which should be used in preference to 587.
5623 You should also consider deploying SRV records to help clients find
5624 these ports.
5625 Older names for &"submissions"& are &"smtps"& and &"ssmtp"&.
5626
5627 Two more commented-out options settings follow:
5628 .code
5629 # qualify_domain =
5630 # qualify_recipient =
5631 .endd
5632 The first of these specifies a domain that Exim uses when it constructs a
5633 complete email address from a local login name. This is often needed when Exim
5634 receives a message from a local process. If you do not set &%qualify_domain%&,
5635 the value of &%primary_hostname%& is used. If you set both of these options,
5636 you can have different qualification domains for sender and recipient
5637 addresses. If you set only the first one, its value is used in both cases.
5638
5639 .cindex "domain literal" "recognizing format"
5640 The following line must be uncommented if you want Exim to recognize
5641 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5642 (an IP address within square brackets) instead of a named domain.
5643 .code
5644 # allow_domain_literals
5645 .endd
5646 The RFCs still require this form, but many people think that in the modern
5647 Internet it makes little sense to permit mail to be sent to specific hosts by
5648 quoting their IP addresses. This ancient format has been used by people who
5649 try to abuse hosts by using them for unwanted relaying. However, some
5650 people believe there are circumstances (for example, messages addressed to
5651 &'postmaster'&) where domain literals are still useful.
5652
5653 The next configuration line is a kind of trigger guard:
5654 .code
5655 never_users = root
5656 .endd
5657 It specifies that no delivery must ever be run as the root user. The normal
5658 convention is to set up &'root'& as an alias for the system administrator. This
5659 setting is a guard against slips in the configuration.
5660 The list of users specified by &%never_users%& is not, however, the complete
5661 list; the build-time configuration in &_Local/Makefile_& has an option called
5662 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5663 contents of &%never_users%& are added to this list. By default
5664 FIXED_NEVER_USERS also specifies root.
5665
5666 When a remote host connects to Exim in order to send mail, the only information
5667 Exim has about the host's identity is its IP address. The next configuration
5668 line,
5669 .code
5670 host_lookup = *
5671 .endd
5672 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5673 in order to get a host name. This improves the quality of the logging
5674 information, but if you feel it is too expensive, you can remove it entirely,
5675 or restrict the lookup to hosts on &"nearby"& networks.
5676 Note that it is not always possible to find a host name from an IP address,
5677 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5678 unreachable.
5679
5680 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5681 1413 (hence their names):
5682 .code
5683 rfc1413_hosts = *
5684 rfc1413_query_timeout = 0s
5685 .endd
5686 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5687 Few hosts offer RFC1413 service these days; calls have to be
5688 terminated by a timeout and this needlessly delays the startup
5689 of an incoming SMTP connection.
5690 If you have hosts for which you trust RFC1413 and need this
5691 information, you can change this.
5692
5693 This line enables an efficiency SMTP option. It is negotiated by clients
5694 and not expected to cause problems but can be disabled if needed.
5695 .code
5696 prdr_enable = true
5697 .endd
5698
5699 When Exim receives messages over SMTP connections, it expects all addresses to
5700 be fully qualified with a domain, as required by the SMTP definition. However,
5701 if you are running a server to which simple clients submit messages, you may
5702 find that they send unqualified addresses. The two commented-out options:
5703 .code
5704 # sender_unqualified_hosts =
5705 # recipient_unqualified_hosts =
5706 .endd
5707 show how you can specify hosts that are permitted to send unqualified sender
5708 and recipient addresses, respectively.
5709
5710 The &%log_selector%& option is used to increase the detail of logging
5711 over the default:
5712 .code
5713 log_selector = +smtp_protocol_error +smtp_syntax_error \
5714 +tls_certificate_verified
5715 .endd
5716
5717 The &%percent_hack_domains%& option is also commented out:
5718 .code
5719 # percent_hack_domains =
5720 .endd
5721 It provides a list of domains for which the &"percent hack"& is to operate.
5722 This is an almost obsolete form of explicit email routing. If you do not know
5723 anything about it, you can safely ignore this topic.
5724
5725 The next two settings in the main part of the default configuration are
5726 concerned with messages that have been &"frozen"& on Exim's queue. When a
5727 message is frozen, Exim no longer continues to try to deliver it. Freezing
5728 occurs when a bounce message encounters a permanent failure because the sender
5729 address of the original message that caused the bounce is invalid, so the
5730 bounce cannot be delivered. This is probably the most common case, but there
5731 are also other conditions that cause freezing, and frozen messages are not
5732 always bounce messages.
5733 .code
5734 ignore_bounce_errors_after = 2d
5735 timeout_frozen_after = 7d
5736 .endd
5737 The first of these options specifies that failing bounce messages are to be
5738 discarded after 2 days on the queue. The second specifies that any frozen
5739 message (whether a bounce message or not) is to be timed out (and discarded)
5740 after a week. In this configuration, the first setting ensures that no failing
5741 bounce message ever lasts a week.
5742
5743 Exim queues it's messages in a spool directory. If you expect to have
5744 large queues, you may consider using this option. It splits the spool
5745 directory into subdirectories to avoid file system degradation from
5746 many files in a single directory, resulting in better performance.
5747 Manual manipulation of queued messages becomes more complex (though fortunately
5748 not often needed).
5749 .code
5750 # split_spool_directory = true
5751 .endd
5752
5753 In an ideal world everybody follows the standards. For non-ASCII
5754 messages RFC 2047 is a standard, allowing a maximum line length of 76
5755 characters. Exim adheres that standard and won't process messages which
5756 violate this standard. (Even ${rfc2047:...} expansions will fail.)
5757 In particular, the Exim maintainers have had multiple reports of
5758 problems from Russian administrators of issues until they disable this
5759 check, because of some popular, yet buggy, mail composition software.
5760 .code
5761 # check_rfc2047_length = false
5762 .endd
5763
5764 If you need to be strictly RFC compliant you may wish to disable the
5765 8BITMIME advertisement. Use this, if you exchange mails with systems
5766 that are not 8-bit clean.
5767 .code
5768 # accept_8bitmime = false
5769 .endd
5770
5771 Libraries you use may depend on specific environment settings. This
5772 imposes a security risk (e.g. PATH). There are two lists:
5773 &%keep_environment%& for the variables to import as they are, and
5774 &%add_environment%& for variables we want to set to a fixed value.
5775 Note that TZ is handled separately, by the $%timezone%$ runtime
5776 option and by the TIMEZONE_DEFAULT buildtime option.
5777 .code
5778 # keep_environment = ^LDAP
5779 # add_environment = PATH=/usr/bin::/bin
5780 .endd
5781
5782
5783 .section "ACL configuration" "SECID54"
5784 .cindex "default" "ACLs"
5785 .cindex "&ACL;" "default configuration"
5786 In the default configuration, the ACL section follows the main configuration.
5787 It starts with the line
5788 .code
5789 begin acl
5790 .endd
5791 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5792 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5793 and &%acl_smtp_data%& above.
5794
5795 .cindex "RCPT" "ACL for"
5796 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5797 RCPT command specifies one of the message's recipients. The ACL statements
5798 are considered in order, until the recipient address is either accepted or
5799 rejected. The RCPT command is then accepted or rejected, according to the
5800 result of the ACL processing.
5801 .code
5802 acl_check_rcpt:
5803 .endd
5804 This line, consisting of a name terminated by a colon, marks the start of the
5805 ACL, and names it.
5806 .code
5807 accept hosts = :
5808 .endd
5809 This ACL statement accepts the recipient if the sending host matches the list.
5810 But what does that strange list mean? It doesn't actually contain any host
5811 names or IP addresses. The presence of the colon puts an empty item in the
5812 list; Exim matches this only if the incoming message did not come from a remote
5813 host, because in that case, the remote hostname is empty. The colon is
5814 important. Without it, the list itself is empty, and can never match anything.
5815
5816 What this statement is doing is to accept unconditionally all recipients in
5817 messages that are submitted by SMTP from local processes using the standard
5818 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5819 manner.
5820 .code
5821 deny message = Restricted characters in address
5822 domains = +local_domains
5823 local_parts = ^[.] : ^.*[@%!/|]
5824
5825 deny message = Restricted characters in address
5826 domains = !+local_domains
5827 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5828 .endd
5829 These statements are concerned with local parts that contain any of the
5830 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5831 Although these characters are entirely legal in local parts (in the case of
5832 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5833 in Internet mail addresses.
5834
5835 The first three have in the past been associated with explicitly routed
5836 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5837 option). Addresses containing these characters are regularly tried by spammers
5838 in an attempt to bypass relaying restrictions, and also by open relay testing
5839 programs. Unless you really need them it is safest to reject these characters
5840 at this early stage. This configuration is heavy-handed in rejecting these
5841 characters for all messages it accepts from remote hosts. This is a deliberate
5842 policy of being as safe as possible.
5843
5844 The first rule above is stricter, and is applied to messages that are addressed
5845 to one of the local domains handled by this host. This is implemented by the
5846 first condition, which restricts it to domains that are listed in the
5847 &'local_domains'& domain list. The &"+"& character is used to indicate a
5848 reference to a named list. In this configuration, there is just one domain in
5849 &'local_domains'&, but in general there may be many.
5850
5851 The second condition on the first statement uses two regular expressions to
5852 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5853 or &"|"&. If you have local accounts that include these characters, you will
5854 have to modify this rule.
5855
5856 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5857 allows them because they have been encountered in practice. (Consider the
5858 common convention of local parts constructed as
5859 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5860 the author of Exim, who has no second initial.) However, a local part starting
5861 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5862 file name (for example, for a mailing list). This is also true for local parts
5863 that contain slashes. A pipe symbol can also be troublesome if the local part
5864 is incorporated unthinkingly into a shell command line.
5865
5866 The second rule above applies to all other domains, and is less strict. This
5867 allows your own users to send outgoing messages to sites that use slashes
5868 and vertical bars in their local parts. It blocks local parts that begin
5869 with a dot, slash, or vertical bar, but allows these characters within the
5870 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5871 and &"!"& is blocked, as before. The motivation here is to prevent your users
5872 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5873 .code
5874 accept local_parts = postmaster
5875 domains = +local_domains
5876 .endd
5877 This statement, which has two conditions, accepts an incoming address if the
5878 local part is &'postmaster'& and the domain is one of those listed in the
5879 &'local_domains'& domain list. The &"+"& character is used to indicate a
5880 reference to a named list. In this configuration, there is just one domain in
5881 &'local_domains'&, but in general there may be many.
5882
5883 The presence of this statement means that mail to postmaster is never blocked
5884 by any of the subsequent tests. This can be helpful while sorting out problems
5885 in cases where the subsequent tests are incorrectly denying access.
5886 .code
5887 require verify = sender
5888 .endd
5889 This statement requires the sender address to be verified before any subsequent
5890 ACL statement can be used. If verification fails, the incoming recipient
5891 address is refused. Verification consists of trying to route the address, to
5892 see if a bounce message could be delivered to it. In the case of remote
5893 addresses, basic verification checks only the domain, but &'callouts'& can be
5894 used for more verification if required. Section &<<SECTaddressverification>>&
5895 discusses the details of address verification.
5896 .code
5897 accept hosts = +relay_from_hosts
5898 control = submission
5899 .endd
5900 This statement accepts the address if the message is coming from one of the
5901 hosts that are defined as being allowed to relay through this host. Recipient
5902 verification is omitted here, because in many cases the clients are dumb MUAs
5903 that do not cope well with SMTP error responses. For the same reason, the
5904 second line specifies &"submission mode"& for messages that are accepted. This
5905 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
5906 messages that are deficient in some way, for example, because they lack a
5907 &'Date:'& header line. If you are actually relaying out from MTAs, you should
5908 probably add recipient verification here, and disable submission mode.
5909 .code
5910 accept authenticated = *
5911 control = submission
5912 .endd
5913 This statement accepts the address if the client host has authenticated itself.
5914 Submission mode is again specified, on the grounds that such messages are most
5915 likely to come from MUAs. The default configuration does not define any
5916 authenticators, though it does include some nearly complete commented-out
5917 examples described in &<<SECTdefconfauth>>&. This means that no client can in
5918 fact authenticate until you complete the authenticator definitions.
5919 .code
5920 require message = relay not permitted
5921 domains = +local_domains : +relay_to_domains
5922 .endd
5923 This statement rejects the address if its domain is neither a local domain nor
5924 one of the domains for which this host is a relay.
5925 .code
5926 require verify = recipient
5927 .endd
5928 This statement requires the recipient address to be verified; if verification
5929 fails, the address is rejected.
5930 .code
5931 # deny message = rejected because $sender_host_address \
5932 # is in a black list at $dnslist_domain\n\
5933 # $dnslist_text
5934 # dnslists = black.list.example
5935 #
5936 # warn dnslists = black.list.example
5937 # add_header = X-Warning: $sender_host_address is in \
5938 # a black list at $dnslist_domain
5939 # log_message = found in $dnslist_domain
5940 .endd
5941 These commented-out lines are examples of how you could configure Exim to check
5942 sending hosts against a DNS black list. The first statement rejects messages
5943 from blacklisted hosts, whereas the second just inserts a warning header
5944 line.
5945 .code
5946 # require verify = csa
5947 .endd
5948 This commented-out line is an example of how you could turn on client SMTP
5949 authorization (CSA) checking. Such checks do DNS lookups for special SRV
5950 records.
5951 .code
5952 accept
5953 .endd
5954 The final statement in the first ACL unconditionally accepts any recipient
5955 address that has successfully passed all the previous tests.
5956 .code
5957 acl_check_data:
5958 .endd
5959 This line marks the start of the second ACL, and names it. Most of the contents
5960 of this ACL are commented out:
5961 .code
5962 # deny malware = *
5963 # message = This message contains a virus \
5964 # ($malware_name).
5965 .endd
5966 These lines are examples of how to arrange for messages to be scanned for
5967 viruses when Exim has been compiled with the content-scanning extension, and a
5968 suitable virus scanner is installed. If the message is found to contain a
5969 virus, it is rejected with the given custom error message.
5970 .code
5971 # warn spam = nobody
5972 # message = X-Spam_score: $spam_score\n\
5973 # X-Spam_score_int: $spam_score_int\n\
5974 # X-Spam_bar: $spam_bar\n\
5975 # X-Spam_report: $spam_report
5976 .endd
5977 These lines are an example of how to arrange for messages to be scanned by
5978 SpamAssassin when Exim has been compiled with the content-scanning extension,
5979 and SpamAssassin has been installed. The SpamAssassin check is run with
5980 &`nobody`& as its user parameter, and the results are added to the message as a
5981 series of extra header line. In this case, the message is not rejected,
5982 whatever the spam score.
5983 .code
5984 accept
5985 .endd
5986 This final line in the DATA ACL accepts the message unconditionally.
5987
5988
5989 .section "Router configuration" "SECID55"
5990 .cindex "default" "routers"
5991 .cindex "routers" "default"
5992 The router configuration comes next in the default configuration, introduced
5993 by the line
5994 .code
5995 begin routers
5996 .endd
5997 Routers are the modules in Exim that make decisions about where to send
5998 messages. An address is passed to each router in turn, until it is either
5999 accepted, or failed. This means that the order in which you define the routers
6000 matters. Each router is fully described in its own chapter later in this
6001 manual. Here we give only brief overviews.
6002 .code
6003 # domain_literal:
6004 # driver = ipliteral
6005 # domains = !+local_domains
6006 # transport = remote_smtp
6007 .endd
6008 .cindex "domain literal" "default router"
6009 This router is commented out because the majority of sites do not want to
6010 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
6011 you uncomment this router, you also need to uncomment the setting of
6012 &%allow_domain_literals%& in the main part of the configuration.
6013 .code
6014 dnslookup:
6015 driver = dnslookup
6016 domains = ! +local_domains
6017 transport = remote_smtp
6018 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
6019 no_more
6020 .endd
6021 The first uncommented router handles addresses that do not involve any local
6022 domains. This is specified by the line
6023 .code
6024 domains = ! +local_domains
6025 .endd
6026 The &%domains%& option lists the domains to which this router applies, but the
6027 exclamation mark is a negation sign, so the router is used only for domains
6028 that are not in the domain list called &'local_domains'& (which was defined at
6029 the start of the configuration). The plus sign before &'local_domains'&
6030 indicates that it is referring to a named list. Addresses in other domains are
6031 passed on to the following routers.
6032
6033 The name of the router driver is &(dnslookup)&,
6034 and is specified by the &%driver%& option. Do not be confused by the fact that
6035 the name of this router instance is the same as the name of the driver. The
6036 instance name is arbitrary, but the name set in the &%driver%& option must be
6037 one of the driver modules that is in the Exim binary.
6038
6039 The &(dnslookup)& router routes addresses by looking up their domains in the
6040 DNS in order to obtain a list of hosts to which the address is routed. If the
6041 router succeeds, the address is queued for the &(remote_smtp)& transport, as
6042 specified by the &%transport%& option. If the router does not find the domain
6043 in the DNS, no further routers are tried because of the &%no_more%& setting, so
6044 the address fails and is bounced.
6045
6046 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
6047 be entirely ignored. This option is present because a number of cases have been
6048 encountered where MX records in the DNS point to host names
6049 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
6050 Completely ignoring these IP addresses causes Exim to fail to route the
6051 email address, so it bounces. Otherwise, Exim would log a routing problem, and
6052 continue to try to deliver the message periodically until the address timed
6053 out.
6054 .code
6055 system_aliases:
6056 driver = redirect
6057 allow_fail
6058 allow_defer
6059 data = ${lookup{$local_part}lsearch{/etc/aliases}}
6060 # user = exim
6061 file_transport = address_file
6062 pipe_transport = address_pipe
6063 .endd
6064 Control reaches this and subsequent routers only for addresses in the local
6065 domains. This router checks to see whether the local part is defined as an
6066 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
6067 data that it looks up from that file. If no data is found for the local part,
6068 the value of the &%data%& option is empty, causing the address to be passed to
6069 the next router.
6070
6071 &_/etc/aliases_& is a conventional name for the system aliases file that is
6072 often used. That is why it is referenced by from the default configuration
6073 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
6074 &_Local/Makefile_& before building Exim.
6075 .code
6076 userforward:
6077 driver = redirect
6078 check_local_user
6079 # local_part_suffix = +* : -*
6080 # local_part_suffix_optional
6081 file = $home/.forward
6082 # allow_filter
6083 no_verify
6084 no_expn
6085 check_ancestor
6086 file_transport = address_file
6087 pipe_transport = address_pipe
6088 reply_transport = address_reply
6089 .endd
6090 This is the most complicated router in the default configuration. It is another
6091 redirection router, but this time it is looking for forwarding data set up by
6092 individual users. The &%check_local_user%& setting specifies a check that the
6093 local part of the address is the login name of a local user. If it is not, the
6094 router is skipped. The two commented options that follow &%check_local_user%&,
6095 namely:
6096 .code
6097 # local_part_suffix = +* : -*
6098 # local_part_suffix_optional
6099 .endd
6100 .vindex "&$local_part_suffix$&"
6101 show how you can specify the recognition of local part suffixes. If the first
6102 is uncommented, a suffix beginning with either a plus or a minus sign, followed
6103 by any sequence of characters, is removed from the local part and placed in the
6104 variable &$local_part_suffix$&. The second suffix option specifies that the
6105 presence of a suffix in the local part is optional. When a suffix is present,
6106 the check for a local login uses the local part with the suffix removed.
6107
6108 When a local user account is found, the file called &_.forward_& in the user's
6109 home directory is consulted. If it does not exist, or is empty, the router
6110 declines. Otherwise, the contents of &_.forward_& are interpreted as
6111 redirection data (see chapter &<<CHAPredirect>>& for more details).
6112
6113 .cindex "Sieve filter" "enabling in default router"
6114 Traditional &_.forward_& files contain just a list of addresses, pipes, or
6115 files. Exim supports this by default. However, if &%allow_filter%& is set (it
6116 is commented out by default), the contents of the file are interpreted as a set
6117 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
6118 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
6119 separate document entitled &'Exim's interfaces to mail filtering'&.
6120
6121 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
6122 verifying addresses, or when running as a consequence of an SMTP EXPN command.
6123 There are two reasons for doing this:
6124
6125 .olist
6126 Whether or not a local user has a &_.forward_& file is not really relevant when
6127 checking an address for validity; it makes sense not to waste resources doing
6128 unnecessary work.
6129 .next
6130 More importantly, when Exim is verifying addresses or handling an EXPN
6131 command during an SMTP session, it is running as the Exim user, not as root.
6132 The group is the Exim group, and no additional groups are set up.
6133 It may therefore not be possible for Exim to read users' &_.forward_& files at
6134 this time.
6135 .endlist
6136
6137 The setting of &%check_ancestor%& prevents the router from generating a new
6138 address that is the same as any previous address that was redirected. (This
6139 works round a problem concerning a bad interaction between aliasing and
6140 forwarding &-- see section &<<SECTredlocmai>>&).
6141
6142 The final three option settings specify the transports that are to be used when
6143 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
6144 auto-reply, respectively. For example, if a &_.forward_& file contains
6145 .code
6146 a.nother@elsewhere.example, /home/spqr/archive
6147 .endd
6148 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
6149 transport.
6150 .code
6151 localuser:
6152 driver = accept
6153 check_local_user
6154 # local_part_suffix = +* : -*
6155 # local_part_suffix_optional
6156 transport = local_delivery
6157 .endd
6158 The final router sets up delivery into local mailboxes, provided that the local
6159 part is the name of a local login, by accepting the address and assigning it to
6160 the &(local_delivery)& transport. Otherwise, we have reached the end of the
6161 routers, so the address is bounced. The commented suffix settings fulfil the
6162 same purpose as they do for the &(userforward)& router.
6163
6164
6165 .section "Transport configuration" "SECID56"
6166 .cindex "default" "transports"
6167 .cindex "transports" "default"
6168 Transports define mechanisms for actually delivering messages. They operate
6169 only when referenced from routers, so the order in which they are defined does
6170 not matter. The transports section of the configuration starts with
6171 .code
6172 begin transports
6173 .endd
6174 One remote transport and four local transports are defined.
6175 .code
6176 remote_smtp:
6177 driver = smtp
6178 hosts_try_prdr = *
6179 .endd
6180 This transport is used for delivering messages over SMTP connections.
6181 The list of remote hosts comes from the router.
6182 The &%hosts_try_prdr%& option enables an efficiency SMTP option.
6183 It is negotiated between client and server
6184 and not expected to cause problems but can be disabled if needed.
6185 All other options are defaulted.
6186 .code
6187 local_delivery:
6188 driver = appendfile
6189 file = /var/mail/$local_part
6190 delivery_date_add
6191 envelope_to_add
6192 return_path_add
6193 # group = mail
6194 # mode = 0660
6195 .endd
6196 This &(appendfile)& transport is used for local delivery to user mailboxes in
6197 traditional BSD mailbox format. By default it runs under the uid and gid of the
6198 local user, which requires the sticky bit to be set on the &_/var/mail_&
6199 directory. Some systems use the alternative approach of running mail deliveries
6200 under a particular group instead of using the sticky bit. The commented options
6201 show how this can be done.
6202
6203 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6204 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6205 similarly-named options above.
6206 .code
6207 address_pipe:
6208 driver = pipe
6209 return_output
6210 .endd
6211 This transport is used for handling deliveries to pipes that are generated by
6212 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6213 option specifies that any output on stdout or stderr generated by the pipe is to
6214 be returned to the sender.
6215 .code
6216 address_file:
6217 driver = appendfile
6218 delivery_date_add
6219 envelope_to_add
6220 return_path_add
6221 .endd
6222 This transport is used for handling deliveries to files that are generated by
6223 redirection. The name of the file is not specified in this instance of
6224 &(appendfile)&, because it comes from the &(redirect)& router.
6225 .code
6226 address_reply:
6227 driver = autoreply
6228 .endd
6229 This transport is used for handling automatic replies generated by users'
6230 filter files.
6231
6232
6233
6234 .section "Default retry rule" "SECID57"
6235 .cindex "retry" "default rule"
6236 .cindex "default" "retry rule"
6237 The retry section of the configuration file contains rules which affect the way
6238 Exim retries deliveries that cannot be completed at the first attempt. It is
6239 introduced by the line
6240 .code
6241 begin retry
6242 .endd
6243 In the default configuration, there is just one rule, which applies to all
6244 errors:
6245 .code
6246 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6247 .endd
6248 This causes any temporarily failing address to be retried every 15 minutes for
6249 2 hours, then at intervals starting at one hour and increasing by a factor of
6250 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6251 is not delivered after 4 days of temporary failure, it is bounced. The time is
6252 measured from first failure, not from the time the message was received.
6253
6254 If the retry section is removed from the configuration, or is empty (that is,
6255 if no retry rules are defined), Exim will not retry deliveries. This turns
6256 temporary errors into permanent errors.
6257
6258
6259 .section "Rewriting configuration" "SECID58"
6260 The rewriting section of the configuration, introduced by
6261 .code
6262 begin rewrite
6263 .endd
6264 contains rules for rewriting addresses in messages as they arrive. There are no
6265 rewriting rules in the default configuration file.
6266
6267
6268
6269 .section "Authenticators configuration" "SECTdefconfauth"
6270 .cindex "AUTH" "configuration"
6271 The authenticators section of the configuration, introduced by
6272 .code
6273 begin authenticators
6274 .endd
6275 defines mechanisms for the use of the SMTP AUTH command. The default
6276 configuration file contains two commented-out example authenticators
6277 which support plaintext username/password authentication using the
6278 standard PLAIN mechanism and the traditional but non-standard LOGIN
6279 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6280 to support most MUA software.
6281
6282 The example PLAIN authenticator looks like this:
6283 .code
6284 #PLAIN:
6285 # driver = plaintext
6286 # server_set_id = $auth2
6287 # server_prompts = :
6288 # server_condition = Authentication is not yet configured
6289 # server_advertise_condition = ${if def:tls_in_cipher }
6290 .endd
6291 And the example LOGIN authenticator looks like this:
6292 .code
6293 #LOGIN:
6294 # driver = plaintext
6295 # server_set_id = $auth1
6296 # server_prompts = <| Username: | Password:
6297 # server_condition = Authentication is not yet configured
6298 # server_advertise_condition = ${if def:tls_in_cipher }
6299 .endd
6300
6301 The &%server_set_id%& option makes Exim remember the authenticated username
6302 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6303 &%server_prompts%& option configures the &(plaintext)& authenticator so
6304 that it implements the details of the specific authentication mechanism,
6305 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6306 when Exim offers authentication to clients; in the examples, this is only
6307 when TLS or SSL has been started, so to enable the authenticators you also
6308 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6309
6310 The &%server_condition%& setting defines how to verify that the username and
6311 password are correct. In the examples it just produces an error message.
6312 To make the authenticators work, you can use a string expansion
6313 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6314
6315 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6316 usercode and password are in different positions.
6317 Chapter &<<CHAPplaintext>>& covers both.
6318
6319 .ecindex IIDconfiwal
6320
6321
6322
6323 . ////////////////////////////////////////////////////////////////////////////
6324 . ////////////////////////////////////////////////////////////////////////////
6325
6326 .chapter "Regular expressions" "CHAPregexp"
6327
6328 .cindex "regular expressions" "library"
6329 .cindex "PCRE"
6330 Exim supports the use of regular expressions in many of its options. It
6331 uses the PCRE regular expression library; this provides regular expression
6332 matching that is compatible with Perl 5. The syntax and semantics of
6333 regular expressions is discussed in
6334 online Perl manpages, in
6335 many Perl reference books, and also in
6336 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6337 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6338
6339 The documentation for the syntax and semantics of the regular expressions that
6340 are supported by PCRE is included in the PCRE distribution, and no further
6341 description is included here. The PCRE functions are called from Exim using
6342 the default option settings (that is, with no PCRE options set), except that
6343 the PCRE_CASELESS option is set when the matching is required to be
6344 case-insensitive.
6345
6346 In most cases, when a regular expression is required in an Exim configuration,
6347 it has to start with a circumflex, in order to distinguish it from plain text
6348 or an &"ends with"& wildcard. In this example of a configuration setting, the
6349 second item in the colon-separated list is a regular expression.
6350 .code
6351 domains = a.b.c : ^\\d{3} : *.y.z : ...
6352 .endd
6353 The doubling of the backslash is required because of string expansion that
6354 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6355 of this issue, and a way of avoiding the need for doubling backslashes. The
6356 regular expression that is eventually used in this example contains just one
6357 backslash. The circumflex is included in the regular expression, and has the
6358 normal effect of &"anchoring"& it to the start of the string that is being
6359 matched.
6360
6361 There are, however, two cases where a circumflex is not required for the
6362 recognition of a regular expression: these are the &%match%& condition in a
6363 string expansion, and the &%matches%& condition in an Exim filter file. In
6364 these cases, the relevant string is always treated as a regular expression; if
6365 it does not start with a circumflex, the expression is not anchored, and can
6366 match anywhere in the subject string.
6367
6368 In all cases, if you want a regular expression to match at the end of a string,
6369 you must code the $ metacharacter to indicate this. For example:
6370 .code
6371 domains = ^\\d{3}\\.example
6372 .endd
6373 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6374 You need to use:
6375 .code
6376 domains = ^\\d{3}\\.example\$
6377 .endd
6378 if you want &'example'& to be the top-level domain. The backslash before the
6379 $ is needed because string expansion also interprets dollar characters.
6380
6381
6382
6383 . ////////////////////////////////////////////////////////////////////////////
6384 . ////////////////////////////////////////////////////////////////////////////
6385
6386 .chapter "File and database lookups" "CHAPfdlookup"
6387 .scindex IIDfidalo1 "file" "lookups"
6388 .scindex IIDfidalo2 "database" "lookups"
6389 .cindex "lookup" "description of"
6390 Exim can be configured to look up data in files or databases as it processes
6391 messages. Two different kinds of syntax are used:
6392
6393 .olist
6394 A string that is to be expanded may contain explicit lookup requests. These
6395 cause parts of the string to be replaced by data that is obtained from the
6396 lookup. Lookups of this type are conditional expansion items. Different results
6397 can be defined for the cases of lookup success and failure. See chapter
6398 &<<CHAPexpand>>&, where string expansions are described in detail.
6399 The key for the lookup is specified as part of the string expansion.
6400 .next
6401 Lists of domains, hosts, and email addresses can contain lookup requests as a
6402 way of avoiding excessively long linear lists. In this case, the data that is
6403 returned by the lookup is often (but not always) discarded; whether the lookup
6404 succeeds or fails is what really counts. These kinds of list are described in
6405 chapter &<<CHAPdomhosaddlists>>&.
6406 The key for the lookup is given by the context in which the list is expanded.
6407 .endlist
6408
6409 String expansions, lists, and lookups interact with each other in such a way
6410 that there is no order in which to describe any one of them that does not
6411 involve references to the others. Each of these three chapters makes more sense
6412 if you have read the other two first. If you are reading this for the first
6413 time, be aware that some of it will make a lot more sense after you have read
6414 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6415
6416 .section "Examples of different lookup syntax" "SECID60"
6417 It is easy to confuse the two different kinds of lookup, especially as the
6418 lists that may contain the second kind are always expanded before being
6419 processed as lists. Therefore, they may also contain lookups of the first kind.
6420 Be careful to distinguish between the following two examples:
6421 .code
6422 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6423 domains = lsearch;/some/file
6424 .endd
6425 The first uses a string expansion, the result of which must be a domain list.
6426 No strings have been specified for a successful or a failing lookup; the
6427 defaults in this case are the looked-up data and an empty string, respectively.
6428 The expansion takes place before the string is processed as a list, and the
6429 file that is searched could contain lines like this:
6430 .code
6431 192.168.3.4: domain1:domain2:...
6432 192.168.1.9: domain3:domain4:...
6433 .endd
6434 When the lookup succeeds, the result of the expansion is a list of domains (and
6435 possibly other types of item that are allowed in domain lists).
6436
6437 In the second example, the lookup is a single item in a domain list. It causes
6438 Exim to use a lookup to see if the domain that is being processed can be found
6439 in the file. The file could contains lines like this:
6440 .code
6441 domain1:
6442 domain2:
6443 .endd
6444 Any data that follows the keys is not relevant when checking that the domain
6445 matches the list item.
6446
6447 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6448 Consider a file containing lines like this:
6449 .code
6450 192.168.5.6: lsearch;/another/file
6451 .endd
6452 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6453 first &%domains%& setting above generates the second setting, which therefore
6454 causes a second lookup to occur.
6455
6456 The rest of this chapter describes the different lookup types that are
6457 available. Any of them can be used in any part of the configuration where a
6458 lookup is permitted.
6459
6460
6461 .section "Lookup types" "SECID61"
6462 .cindex "lookup" "types of"
6463 .cindex "single-key lookup" "definition of"
6464 Two different types of data lookup are implemented:
6465
6466 .ilist
6467 The &'single-key'& type requires the specification of a file in which to look,
6468 and a single key to search for. The key must be a non-empty string for the
6469 lookup to succeed. The lookup type determines how the file is searched.
6470 .next
6471 .cindex "query-style lookup" "definition of"
6472 The &'query-style'& type accepts a generalized database query. No particular
6473 key value is assumed by Exim for query-style lookups. You can use whichever
6474 Exim variables you need to construct the database query.
6475 .endlist
6476
6477 The code for each lookup type is in a separate source file that is included in
6478 the binary of Exim only if the corresponding compile-time option is set. The
6479 default settings in &_src/EDITME_& are:
6480 .code
6481 LOOKUP_DBM=yes
6482 LOOKUP_LSEARCH=yes
6483 .endd
6484 which means that only linear searching and DBM lookups are included by default.
6485 For some types of lookup (e.g. SQL databases), you need to install appropriate
6486 libraries and header files before building Exim.
6487
6488
6489
6490
6491 .section "Single-key lookup types" "SECTsinglekeylookups"
6492 .cindex "lookup" "single-key types"
6493 .cindex "single-key lookup" "list of types"
6494 The following single-key lookup types are implemented:
6495
6496 .ilist
6497 .cindex "cdb" "description of"
6498 .cindex "lookup" "cdb"
6499 .cindex "binary zero" "in lookup key"
6500 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6501 string without a terminating binary zero. The cdb format is designed for
6502 indexed files that are read frequently and never updated, except by total
6503 re-creation. As such, it is particularly suitable for large files containing
6504 aliases or other indexed data referenced by an MTA. Information about cdb can
6505 be found in several places:
6506 .display
6507 &url(http://www.pobox.com/~djb/cdb.html)
6508 &url(ftp://ftp.corpit.ru/pub/tinycdb/)
6509 &url(http://packages.debian.org/stable/utils/freecdb.html)
6510 .endd
6511 A cdb distribution is not needed in order to build Exim with cdb support,
6512 because the code for reading cdb files is included directly in Exim itself.
6513 However, no means of building or testing cdb files is provided with Exim, so
6514 you need to obtain a cdb distribution in order to do this.
6515 .next
6516 .cindex "DBM" "lookup type"
6517 .cindex "lookup" "dbm"
6518 .cindex "binary zero" "in lookup key"
6519 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6520 DBM file by looking up the record with the given key. A terminating binary
6521 zero is included in the key that is passed to the DBM library. See section
6522 &<<SECTdb>>& for a discussion of DBM libraries.
6523
6524 .cindex "Berkeley DB library" "file format"
6525 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6526 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6527 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6528 the DB_UNKNOWN option. This enables it to handle any of the types of database
6529 that the library supports, and can be useful for accessing DBM files created by
6530 other applications. (For earlier DB versions, DB_HASH is always used.)
6531 .next
6532 .cindex "lookup" "dbmjz"
6533 .cindex "lookup" "dbm &-- embedded NULs"
6534 .cindex "sasldb2"
6535 .cindex "dbmjz lookup type"
6536 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6537 interpreted as an Exim list; the elements of the list are joined together with
6538 ASCII NUL characters to form the lookup key. An example usage would be to
6539 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6540 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6541 &(cram_md5)& authenticator.
6542 .next
6543 .cindex "lookup" "dbmnz"
6544 .cindex "lookup" "dbm &-- terminating zero"
6545 .cindex "binary zero" "in lookup key"
6546 .cindex "Courier"
6547 .cindex "&_/etc/userdbshadow.dat_&"
6548 .cindex "dbmnz lookup type"
6549 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6550 is not included in the key that is passed to the DBM library. You may need this
6551 if you want to look up data in files that are created by or shared with some
6552 other application that does not use terminating zeros. For example, you need to
6553 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6554 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6555 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6556 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6557 .next
6558 .cindex "lookup" "dsearch"
6559 .cindex "dsearch lookup type"
6560 &(dsearch)&: The given file must be a directory; this is searched for an entry
6561 whose name is the key by calling the &[lstat()]& function. The key may not
6562 contain any forward slash characters. If &[lstat()]& succeeds, the result of
6563 the lookup is the name of the entry, which may be a file, directory,
6564 symbolic link, or any other kind of directory entry. An example of how this
6565 lookup can be used to support virtual domains is given in section
6566 &<<SECTvirtualdomains>>&.
6567 .next
6568 .cindex "lookup" "iplsearch"
6569 .cindex "iplsearch lookup type"
6570 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6571 terminated by a colon or white space or the end of the line. The keys in the
6572 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6573 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6574 being interpreted as a key terminator. For example:
6575 .code
6576 1.2.3.4: data for 1.2.3.4
6577 192.168.0.0/16: data for 192.168.0.0/16
6578 "abcd::cdab": data for abcd::cdab
6579 "abcd:abcd::/32" data for abcd:abcd::/32
6580 .endd
6581 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6582 file is searched linearly, using the CIDR masks where present, until a matching
6583 key is found. The first key that matches is used; there is no attempt to find a
6584 &"best"& match. Apart from the way the keys are matched, the processing for
6585 &(iplsearch)& is the same as for &(lsearch)&.
6586
6587 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6588 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6589 lookup types support only literal keys.
6590
6591 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6592 the implicit key is the host's IP address rather than its name (see section
6593 &<<SECThoslispatsikey>>&).
6594 .next
6595 .cindex "linear search"
6596 .cindex "lookup" "lsearch"
6597 .cindex "lsearch lookup type"
6598 .cindex "case sensitivity" "in lsearch lookup"
6599 &(lsearch)&: The given file is a text file that is searched linearly for a
6600 line beginning with the search key, terminated by a colon or white space or the
6601 end of the line. The search is case-insensitive; that is, upper and lower case
6602 letters are treated as the same. The first occurrence of the key that is found
6603 in the file is used.
6604
6605 White space between the key and the colon is permitted. The remainder of the
6606 line, with leading and trailing white space removed, is the data. This can be
6607 continued onto subsequent lines by starting them with any amount of white
6608 space, but only a single space character is included in the data at such a
6609 junction. If the data begins with a colon, the key must be terminated by a
6610 colon, for example:
6611 .code
6612 baduser: :fail:
6613 .endd
6614 Empty lines and lines beginning with # are ignored, even if they occur in the
6615 middle of an item. This is the traditional textual format of alias files. Note
6616 that the keys in an &(lsearch)& file are literal strings. There is no
6617 wildcarding of any kind.
6618
6619 .cindex "lookup" "lsearch &-- colons in keys"
6620 .cindex "white space" "in lsearch key"
6621 In most &(lsearch)& files, keys are not required to contain colons or #
6622 characters, or white space. However, if you need this feature, it is available.
6623 If a key begins with a doublequote character, it is terminated only by a
6624 matching quote (or end of line), and the normal escaping rules apply to its
6625 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6626 quoted keys (exactly as for unquoted keys). There is no special handling of
6627 quotes for the data part of an &(lsearch)& line.
6628
6629 .next
6630 .cindex "NIS lookup type"
6631 .cindex "lookup" "NIS"
6632 .cindex "binary zero" "in lookup key"
6633 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
6634 the given key, without a terminating binary zero. There is a variant called
6635 &(nis0)& which does include the terminating binary zero in the key. This is
6636 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6637 aliases; the full map names must be used.
6638
6639 .next
6640 .cindex "wildlsearch lookup type"
6641 .cindex "lookup" "wildlsearch"
6642 .cindex "nwildlsearch lookup type"
6643 .cindex "lookup" "nwildlsearch"
6644 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6645 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6646 the file may be wildcarded. The difference between these two lookup types is
6647 that for &(wildlsearch)&, each key in the file is string-expanded before being
6648 used, whereas for &(nwildlsearch)&, no expansion takes place.
6649
6650 .cindex "case sensitivity" "in (n)wildlsearch lookup"
6651 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
6652 file that are regular expressions can be made case-sensitive by the use of
6653 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
6654
6655 . ==== As this is a nested list, any displays it contains must be indented
6656 . ==== as otherwise they are too far to the left.
6657
6658 .olist
6659 The string may begin with an asterisk to mean &"ends with"&. For example:
6660 .code
6661 *.a.b.c data for anything.a.b.c
6662 *fish data for anythingfish
6663 .endd
6664 .next
6665 The string may begin with a circumflex to indicate a regular expression. For
6666 example, for &(wildlsearch)&:
6667 .code
6668 ^\N\d+\.a\.b\N data for <digits>.a.b
6669 .endd
6670 Note the use of &`\N`& to disable expansion of the contents of the regular
6671 expression. If you are using &(nwildlsearch)&, where the keys are not
6672 string-expanded, the equivalent entry is:
6673 .code
6674 ^\d+\.a\.b data for <digits>.a.b
6675 .endd
6676 The case-insensitive flag is set at the start of compiling the regular
6677 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
6678 For example, to make the entire pattern case-sensitive:
6679 .code
6680 ^(?-i)\d+\.a\.b data for <digits>.a.b
6681 .endd
6682
6683 If the regular expression contains white space or colon characters, you must
6684 either quote it (see &(lsearch)& above), or represent these characters in other
6685 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
6686 colon. This may be easier than quoting, because if you quote, you have to
6687 escape all the backslashes inside the quotes.
6688
6689 &*Note*&: It is not possible to capture substrings in a regular expression
6690 match for later use, because the results of all lookups are cached. If a lookup
6691 is repeated, the result is taken from the cache, and no actual pattern matching
6692 takes place. The values of all the numeric variables are unset after a
6693 &((n)wildlsearch)& match.
6694
6695 .next
6696 Although I cannot see it being of much use, the general matching function that
6697 is used to implement &((n)wildlsearch)& means that the string may begin with a
6698 lookup name terminated by a semicolon, and followed by lookup data. For
6699 example:
6700 .code
6701 cdb;/some/file data for keys that match the file
6702 .endd
6703 The data that is obtained from the nested lookup is discarded.
6704 .endlist olist
6705
6706 Keys that do not match any of these patterns are interpreted literally. The
6707 continuation rules for the data are the same as for &(lsearch)&, and keys may
6708 be followed by optional colons.
6709
6710 &*Warning*&: Unlike most other single-key lookup types, a file of data for
6711 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
6712 lookup types support only literal keys.
6713 .endlist ilist
6714
6715
6716 .section "Query-style lookup types" "SECTquerystylelookups"
6717 .cindex "lookup" "query-style types"
6718 .cindex "query-style lookup" "list of types"
6719 The supported query-style lookup types are listed below. Further details about
6720 many of them are given in later sections.
6721
6722 .ilist
6723 .cindex "DNS" "as a lookup type"
6724 .cindex "lookup" "DNS"
6725 &(dnsdb)&: This does a DNS search for one or more records whose domain names
6726 are given in the supplied query. The resulting data is the contents of the
6727 records. See section &<<SECTdnsdb>>&.
6728 .next
6729 .cindex "InterBase lookup type"
6730 .cindex "lookup" "InterBase"
6731 &(ibase)&: This does a lookup in an InterBase database.
6732 .next
6733 .cindex "LDAP" "lookup type"
6734 .cindex "lookup" "LDAP"
6735 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
6736 returns attributes from a single entry. There is a variant called &(ldapm)&
6737 that permits values from multiple entries to be returned. A third variant
6738 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
6739 any attribute values. See section &<<SECTldap>>&.
6740 .next
6741 .cindex "MySQL" "lookup type"
6742 .cindex "lookup" "MySQL"
6743 &(mysql)&: The format of the query is an SQL statement that is passed to a
6744 MySQL database. See section &<<SECTsql>>&.
6745 .next
6746 .cindex "NIS+ lookup type"
6747 .cindex "lookup" "NIS+"
6748 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
6749 the field to be returned. See section &<<SECTnisplus>>&.
6750 .next
6751 .cindex "Oracle" "lookup type"
6752 .cindex "lookup" "Oracle"
6753 &(oracle)&: The format of the query is an SQL statement that is passed to an
6754 Oracle database. See section &<<SECTsql>>&.
6755 .next
6756 .cindex "lookup" "passwd"
6757 .cindex "passwd lookup type"
6758 .cindex "&_/etc/passwd_&"
6759 &(passwd)& is a query-style lookup with queries that are just user names. The
6760 lookup calls &[getpwnam()]& to interrogate the system password data, and on
6761 success, the result string is the same as you would get from an &(lsearch)&
6762 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
6763 password value. For example:
6764 .code
6765 *:42:42:King Rat:/home/kr:/bin/bash
6766 .endd
6767 .next
6768 .cindex "PostgreSQL lookup type"
6769 .cindex "lookup" "PostgreSQL"
6770 &(pgsql)&: The format of the query is an SQL statement that is passed to a
6771 PostgreSQL database. See section &<<SECTsql>>&.
6772
6773 .next
6774 .cindex "Redis lookup type"
6775 .cindex lookup Redis
6776 &(redis)&: The format of the query is either a simple get or simple set,
6777 passed to a Redis database. See section &<<SECTsql>>&.
6778
6779 .next
6780 .cindex "sqlite lookup type"
6781 .cindex "lookup" "sqlite"
6782 &(sqlite)&: The format of the query is a file name followed by an SQL statement
6783 that is passed to an SQLite database. See section &<<SECTsqlite>>&.
6784
6785 .next
6786 &(testdb)&: This is a lookup type that is used for testing Exim. It is
6787 not likely to be useful in normal operation.
6788 .next
6789 .cindex "whoson lookup type"
6790 .cindex "lookup" "whoson"
6791 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
6792 allows a server to check whether a particular (dynamically allocated) IP
6793 address is currently allocated to a known (trusted) user and, optionally, to
6794 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
6795 at one time for &"POP before SMTP"& authentication, but that approach has been
6796 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
6797 &"POP before SMTP"& checking using ACL statements such as
6798 .code
6799 require condition = \
6800 ${lookup whoson {$sender_host_address}{yes}{no}}
6801 .endd
6802 The query consists of a single IP address. The value returned is the name of
6803 the authenticated user, which is stored in the variable &$value$&. However, in
6804 this example, the data in &$value$& is not used; the result of the lookup is
6805 one of the fixed strings &"yes"& or &"no"&.
6806 .endlist
6807
6808
6809
6810 .section "Temporary errors in lookups" "SECID63"
6811 .cindex "lookup" "temporary error in"
6812 Lookup functions can return temporary error codes if the lookup cannot be
6813 completed. For example, an SQL or LDAP database might be unavailable. For this
6814 reason, it is not advisable to use a lookup that might do this for critical
6815 options such as a list of local domains.
6816
6817 When a lookup cannot be completed in a router or transport, delivery
6818 of the message (to the relevant address) is deferred, as for any other
6819 temporary error. In other circumstances Exim may assume the lookup has failed,
6820 or may give up altogether.
6821
6822
6823
6824 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
6825 .cindex "wildcard lookups"
6826 .cindex "lookup" "default values"
6827 .cindex "lookup" "wildcard"
6828 .cindex "lookup" "* added to type"
6829 .cindex "default" "in single-key lookups"
6830 In this context, a &"default value"& is a value specified by the administrator
6831 that is to be used if a lookup fails.
6832
6833 &*Note:*& This section applies only to single-key lookups. For query-style
6834 lookups, the facilities of the query language must be used. An attempt to
6835 specify a default for a query-style lookup provokes an error.
6836
6837 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
6838 and the initial lookup fails, the key &"*"& is looked up in the file to
6839 provide a default value. See also the section on partial matching below.
6840
6841 .cindex "*@ with single-key lookup"
6842 .cindex "lookup" "*@ added to type"
6843 .cindex "alias file" "per-domain default"
6844 Alternatively, if &"*@"& is added to a single-key lookup type (for example
6845 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
6846 character, a second lookup is done with everything before the last @ replaced
6847 by *. This makes it possible to provide per-domain defaults in alias files
6848 that include the domains in the keys. If the second lookup fails (or doesn't
6849 take place because there is no @ in the key), &"*"& is looked up.
6850 For example, a &(redirect)& router might contain:
6851 .code
6852 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
6853 .endd
6854 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
6855 looks up these keys, in this order:
6856 .code
6857 jane@eyre.example
6858 *@eyre.example
6859 *
6860 .endd
6861 The data is taken from whichever key it finds first. &*Note*&: In an
6862 &(lsearch)& file, this does not mean the first of these keys in the file. A
6863 complete scan is done for each key, and only if it is not found at all does
6864 Exim move on to try the next key.
6865
6866
6867
6868 .section "Partial matching in single-key lookups" "SECTpartiallookup"
6869 .cindex "partial matching"
6870 .cindex "wildcard lookups"
6871 .cindex "lookup" "partial matching"
6872 .cindex "lookup" "wildcard"
6873 .cindex "asterisk" "in search type"
6874 The normal operation of a single-key lookup is to search the file for an exact
6875 match with the given key. However, in a number of situations where domains are
6876 being looked up, it is useful to be able to do partial matching. In this case,
6877 information in the file that has a key starting with &"*."& is matched by any
6878 domain that ends with the components that follow the full stop. For example, if
6879 a key in a DBM file is
6880 .code
6881 *.dates.fict.example
6882 .endd
6883 then when partial matching is enabled this is matched by (amongst others)
6884 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
6885 by &'dates.fict.example'&, if that does not appear as a separate key in the
6886 file.
6887
6888 &*Note*&: Partial matching is not available for query-style lookups. It is
6889 also not available for any lookup items in address lists (see section
6890 &<<SECTaddresslist>>&).
6891
6892 Partial matching is implemented by doing a series of separate lookups using
6893 keys constructed by modifying the original subject key. This means that it can
6894 be used with any of the single-key lookup types, provided that
6895 partial matching keys
6896 beginning with a special prefix (default &"*."&) are included in the data file.
6897 Keys in the file that do not begin with the prefix are matched only by
6898 unmodified subject keys when partial matching is in use.
6899
6900 Partial matching is requested by adding the string &"partial-"& to the front of
6901 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
6902 is done, the subject key is first looked up unmodified; if that fails, &"*."&
6903 is added at the start of the subject key, and it is looked up again. If that
6904 fails, further lookups are tried with dot-separated components removed from the
6905 start of the subject key, one-by-one, and &"*."& added on the front of what
6906 remains.
6907
6908 A minimum number of two non-* components are required. This can be adjusted
6909 by including a number before the hyphen in the search type. For example,
6910 &%partial3-lsearch%& specifies a minimum of three non-* components in the
6911 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
6912 subject key is &'2250.dates.fict.example'& then the following keys are looked
6913 up when the minimum number of non-* components is two:
6914 .code
6915 2250.dates.fict.example
6916 *.2250.dates.fict.example
6917 *.dates.fict.example
6918 *.fict.example
6919 .endd
6920 As soon as one key in the sequence is successfully looked up, the lookup
6921 finishes.
6922
6923 .cindex "lookup" "partial matching &-- changing prefix"
6924 .cindex "prefix" "for partial matching"
6925 The use of &"*."& as the partial matching prefix is a default that can be
6926 changed. The motivation for this feature is to allow Exim to operate with file
6927 formats that are used by other MTAs. A different prefix can be supplied in
6928 parentheses instead of the hyphen after &"partial"&. For example:
6929 .code
6930 domains = partial(.)lsearch;/some/file
6931 .endd
6932 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
6933 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
6934 components is unchanged). The prefix may consist of any punctuation characters
6935 other than a closing parenthesis. It may be empty, for example:
6936 .code
6937 domains = partial1()cdb;/some/file
6938 .endd
6939 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
6940 &`a.b.c`&, &`b.c`&, and &`c`&.
6941
6942 If &"partial0"& is specified, what happens at the end (when the lookup with
6943 just one non-wild component has failed, and the original key is shortened right
6944 down to the null string) depends on the prefix:
6945
6946 .ilist
6947 If the prefix has zero length, the whole lookup fails.
6948 .next
6949 If the prefix has length 1, a lookup for just the prefix is done. For
6950 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
6951 .next
6952 Otherwise, if the prefix ends in a dot, the dot is removed, and the
6953 remainder is looked up. With the default prefix, therefore, the final lookup is
6954 for &"*"& on its own.
6955 .next
6956 Otherwise, the whole prefix is looked up.
6957 .endlist
6958
6959
6960 If the search type ends in &"*"& or &"*@"& (see section
6961 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
6962 this implies happens after all partial lookups have failed. If &"partial0"& is
6963 specified, adding &"*"& to the search type has no effect with the default
6964 prefix, because the &"*"& key is already included in the sequence of partial
6965 lookups. However, there might be a use for lookup types such as
6966 &"partial0(.)lsearch*"&.
6967
6968 The use of &"*"& in lookup partial matching differs from its use as a wildcard
6969 in domain lists and the like. Partial matching works only in terms of
6970 dot-separated components; a key such as &`*fict.example`&
6971 in a database file is useless, because the asterisk in a partial matching
6972 subject key is always followed by a dot.
6973
6974
6975
6976
6977 .section "Lookup caching" "SECID64"
6978 .cindex "lookup" "caching"
6979 .cindex "caching" "lookup data"
6980 Exim caches all lookup results in order to avoid needless repetition of
6981 lookups. However, because (apart from the daemon) Exim operates as a collection
6982 of independent, short-lived processes, this caching applies only within a
6983 single Exim process. There is no inter-process lookup caching facility.
6984
6985 For single-key lookups, Exim keeps the relevant files open in case there is
6986 another lookup that needs them. In some types of configuration this can lead to
6987 many files being kept open for messages with many recipients. To avoid hitting
6988 the operating system limit on the number of simultaneously open files, Exim
6989 closes the least recently used file when it needs to open more files than its
6990 own internal limit, which can be changed via the &%lookup_open_max%& option.
6991
6992 The single-key lookup files are closed and the lookup caches are flushed at
6993 strategic points during delivery &-- for example, after all routing is
6994 complete.
6995
6996
6997
6998
6999 .section "Quoting lookup data" "SECID65"
7000 .cindex "lookup" "quoting"
7001 .cindex "quoting" "in lookups"
7002 When data from an incoming message is included in a query-style lookup, there
7003 is the possibility of special characters in the data messing up the syntax of
7004 the query. For example, a NIS+ query that contains
7005 .code
7006 [name=$local_part]
7007 .endd
7008 will be broken if the local part happens to contain a closing square bracket.
7009 For NIS+, data can be enclosed in double quotes like this:
7010 .code
7011 [name="$local_part"]
7012 .endd
7013 but this still leaves the problem of a double quote in the data. The rule for
7014 NIS+ is that double quotes must be doubled. Other lookup types have different
7015 rules, and to cope with the differing requirements, an expansion operator
7016 of the following form is provided:
7017 .code
7018 ${quote_<lookup-type>:<string>}
7019 .endd
7020 For example, the safest way to write the NIS+ query is
7021 .code
7022 [name="${quote_nisplus:$local_part}"]
7023 .endd
7024 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
7025 operator can be used for all lookup types, but has no effect for single-key
7026 lookups, since no quoting is ever needed in their key strings.
7027
7028
7029
7030
7031 .section "More about dnsdb" "SECTdnsdb"
7032 .cindex "dnsdb lookup"
7033 .cindex "lookup" "dnsdb"
7034 .cindex "DNS" "as a lookup type"
7035 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
7036 of a record type and a domain name, separated by an equals sign. For example,
7037 an expansion string could contain:
7038 .code
7039 ${lookup dnsdb{mx=a.b.example}{$value}fail}
7040 .endd
7041 If the lookup succeeds, the result is placed in &$value$&, which in this case
7042 is used on its own as the result. If the lookup does not succeed, the
7043 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
7044 &<<SECTforexpfai>>& for an explanation of what this means.
7045
7046 The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
7047 and TXT, and, when Exim is compiled with IPv6 support, AAAA.
7048 If no type is given, TXT is assumed.
7049
7050 For any record type, if multiple records are found, the data is returned as a
7051 concatenation, with newline as the default separator. The order, of course,
7052 depends on the DNS resolver. You can specify a different separator character
7053 between multiple records by putting a right angle-bracket followed immediately
7054 by the new separator at the start of the query. For example:
7055 .code
7056 ${lookup dnsdb{>: a=host1.example}}
7057 .endd
7058 It is permitted to specify a space as the separator character. Further
7059 white space is ignored.
7060 For lookup types that return multiple fields per record,
7061 an alternate field separator can be specified using a comma after the main
7062 separator character, followed immediately by the field separator.
7063
7064 .cindex "PTR record" "in &(dnsdb)& lookup"
7065 When the type is PTR,
7066 the data can be an IP address, written as normal; inversion and the addition of
7067 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
7068 .code
7069 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
7070 .endd
7071 If the data for a PTR record is not a syntactically valid IP address, it is not
7072 altered and nothing is added.
7073
7074 .cindex "MX record" "in &(dnsdb)& lookup"
7075 .cindex "SRV record" "in &(dnsdb)& lookup"
7076 For an MX lookup, both the preference value and the host name are returned for
7077 each record, separated by a space. For an SRV lookup, the priority, weight,
7078 port, and host name are returned for each record, separated by spaces.
7079 The field separator can be modified as above.
7080
7081 .cindex "TXT record" "in &(dnsdb)& lookup"
7082 .cindex "SPF record" "in &(dnsdb)& lookup"
7083 For TXT records with multiple items of data, only the first item is returned,
7084 unless a field separator is specified.
7085 To concatenate items without a separator, use a semicolon instead.
7086 For SPF records the
7087 default behaviour is to concatenate multiple items without using a separator.
7088 .code
7089 ${lookup dnsdb{>\n,: txt=a.b.example}}
7090 ${lookup dnsdb{>\n; txt=a.b.example}}
7091 ${lookup dnsdb{spf=example.org}}
7092 .endd
7093 It is permitted to specify a space as the separator character. Further
7094 white space is ignored.
7095
7096 .cindex "SOA record" "in &(dnsdb)& lookup"
7097 For an SOA lookup, while no result is obtained the lookup is redone with
7098 successively more leading components dropped from the given domain.
7099 Only the primary-nameserver field is returned unless a field separator is
7100 specified.
7101 .code
7102 ${lookup dnsdb{>:,; soa=a.b.example.com}}
7103 .endd
7104
7105 .section "Dnsdb lookup modifiers" "SECTdnsdb_mod"
7106 .cindex "dnsdb modifiers"
7107 .cindex "modifiers" "dnsdb"
7108 .cindex "options" "dnsdb"
7109 Modifiers for &(dnsdb)& lookups are given by optional keywords,
7110 each followed by a comma,
7111 that may appear before the record type.
7112
7113 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
7114 temporary DNS error for any of them, the behaviour is controlled by
7115 a defer-option modifier.
7116 The possible keywords are
7117 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
7118 With &"strict"& behaviour, any temporary DNS error causes the
7119 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
7120 ignored, and the behaviour is as if the DNS lookup failed to find anything.
7121 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
7122 error causes the whole lookup to defer only if none of the other lookups
7123 succeed. The default is &"lax"&, so the following lookups are equivalent:
7124 .code
7125 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
7126 ${lookup dnsdb{a=one.host.com:two.host.com}}
7127 .endd
7128 Thus, in the default case, as long as at least one of the DNS lookups
7129 yields some data, the lookup succeeds.
7130
7131 .cindex "DNSSEC" "dns lookup"
7132 Use of &(DNSSEC)& is controlled by a dnssec modifier.
7133 The possible keywords are
7134 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
7135 With &"strict"& or &"lax"& DNSSEC information is requested
7136 with the lookup.
7137 With &"strict"& a response from the DNS resolver that
7138 is not labelled as authenticated data
7139 is treated as equivalent to a temporary DNS error.
7140 The default is &"never"&.
7141
7142 See also the &$lookup_dnssec_authenticated$& variable.
7143
7144 .cindex timeout "dns lookup"
7145 .cindex "DNS" timeout
7146 Timeout for the dnsdb lookup can be controlled by a retrans modifier.
7147 The form is &"retrans_VAL"& where VAL is an Exim time specification
7148 (e.g. &"5s"&).
7149 The default value is set by the main configuration option &%dns_retrans%&.
7150
7151 Retries for the dnsdb lookup can be controlled by a retry modifier.
7152 The form if &"retry_VAL"& where VAL is an integer.
7153 The default count is set by the main configuration option &%dns_retry%&.
7154
7155 .cindex caching "of dns lookup"
7156 .cindex TTL "of dns lookup"
7157 .cindex DNS TTL
7158 Dnsdb lookup results are cached within a single process (and its children).
7159 The cache entry lifetime is limited to the smallest time-to-live (TTL)
7160 value of the set of returned DNS records.
7161
7162
7163 .section "Pseudo dnsdb record types" "SECID66"
7164 .cindex "MX record" "in &(dnsdb)& lookup"
7165 By default, both the preference value and the host name are returned for
7166 each MX record, separated by a space. If you want only host names, you can use
7167 the pseudo-type MXH:
7168 .code
7169 ${lookup dnsdb{mxh=a.b.example}}
7170 .endd
7171 In this case, the preference values are omitted, and just the host names are
7172 returned.
7173
7174 .cindex "name server for enclosing domain"
7175 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
7176 records on the given domain, but if none are found, it removes the first
7177 component of the domain name, and tries again. This process continues until NS
7178 records are found or there are no more components left (or there is a DNS
7179 error). In other words, it may return the name servers for a top-level domain,
7180 but it never returns the root name servers. If there are no NS records for the
7181 top-level domain, the lookup fails. Consider these examples:
7182 .code
7183 ${lookup dnsdb{zns=xxx.quercite.com}}
7184 ${lookup dnsdb{zns=xxx.edu}}
7185 .endd
7186 Assuming that in each case there are no NS records for the full domain name,
7187 the first returns the name servers for &%quercite.com%&, and the second returns
7188 the name servers for &%edu%&.
7189
7190 You should be careful about how you use this lookup because, unless the
7191 top-level domain does not exist, the lookup always returns some host names. The
7192 sort of use to which this might be put is for seeing if the name servers for a
7193 given domain are on a blacklist. You can probably assume that the name servers
7194 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
7195 such a list.
7196
7197 .cindex "CSA" "in &(dnsdb)& lookup"
7198 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
7199 records according to the CSA rules, which are described in section
7200 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
7201 not sufficient because of the extra parent domain search behaviour of CSA. The
7202 result of a successful lookup such as:
7203 .code
7204 ${lookup dnsdb {csa=$sender_helo_name}}
7205 .endd
7206 has two space-separated fields: an authorization code and a target host name.
7207 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
7208 authorization required but absent, or &"?"& for unknown.
7209
7210 .cindex "A+" "in &(dnsdb)& lookup"
7211 The pseudo-type A+ performs an AAAA
7212 and then an A lookup. All results are returned; defer processing
7213 (see below) is handled separately for each lookup. Example:
7214 .code
7215 ${lookup dnsdb {>; a+=$sender_helo_name}}
7216 .endd
7217
7218
7219 .section "Multiple dnsdb lookups" "SECID67"
7220 In the previous sections, &(dnsdb)& lookups for a single domain are described.
7221 However, you can specify a list of domains or IP addresses in a single
7222 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
7223 the default separator, but with the ability to change this. For example:
7224 .code
7225 ${lookup dnsdb{one.domain.com:two.domain.com}}
7226 ${lookup dnsdb{a=one.host.com:two.host.com}}
7227 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
7228 .endd
7229 In order to retain backwards compatibility, there is one special case: if
7230 the lookup type is PTR and no change of separator is specified, Exim looks
7231 to see if the rest of the string is precisely one IPv6 address. In this
7232 case, it does not treat it as a list.
7233
7234 The data from each lookup is concatenated, with newline separators by default,
7235 in the same way that multiple DNS records for a single item are handled. A
7236 different separator can be specified, as described above.
7237
7238
7239
7240
7241 .section "More about LDAP" "SECTldap"
7242 .cindex "LDAP" "lookup, more about"
7243 .cindex "lookup" "LDAP"
7244 .cindex "Solaris" "LDAP"
7245 The original LDAP implementation came from the University of Michigan; this has
7246 become &"Open LDAP"&, and there are now two different releases. Another
7247 implementation comes from Netscape, and Solaris 7 and subsequent releases
7248 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7249 the lookup function level, their error handling is different. For this reason
7250 it is necessary to set a compile-time variable when building Exim with LDAP, to
7251 indicate which LDAP library is in use. One of the following should appear in
7252 your &_Local/Makefile_&:
7253 .code
7254 LDAP_LIB_TYPE=UMICHIGAN
7255 LDAP_LIB_TYPE=OPENLDAP1
7256 LDAP_LIB_TYPE=OPENLDAP2
7257 LDAP_LIB_TYPE=NETSCAPE
7258 LDAP_LIB_TYPE=SOLARIS
7259 .endd
7260 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7261 same interface as the University of Michigan version.
7262
7263 There are three LDAP lookup types in Exim. These behave slightly differently in
7264 the way they handle the results of a query:
7265
7266 .ilist
7267 &(ldap)& requires the result to contain just one entry; if there are more, it
7268 gives an error.
7269 .next
7270 &(ldapdn)& also requires the result to contain just one entry, but it is the
7271 Distinguished Name that is returned rather than any attribute values.
7272 .next
7273 &(ldapm)& permits the result to contain more than one entry; the attributes
7274 from all of them are returned.
7275 .endlist
7276
7277
7278 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7279 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7280 the data returned by a successful lookup is described in the next section.
7281 First we explain how LDAP queries are coded.
7282
7283
7284 .section "Format of LDAP queries" "SECTforldaque"
7285 .cindex "LDAP" "query format"
7286 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7287 the configuration of a &(redirect)& router one might have this setting:
7288 .code
7289 data = ${lookup ldap \
7290 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7291 c=UK?mailbox?base?}}
7292 .endd
7293 .cindex "LDAP" "with TLS"
7294 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7295 secure (encrypted) LDAP connections. The second of these ensures that an
7296 encrypted TLS connection is used.
7297
7298 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7299 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7300 See the &%ldap_start_tls%& option.
7301
7302 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7303 controlled. Every part of the TLS configuration can be configured by settings in
7304 &_exim.conf_&. Depending on the version of the client libraries installed on
7305 your system, some of the initialization may have required setting options in
7306 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7307 certificates. This revealed a nuance where the current UID that exim was
7308 running as could affect which config files it read. With Exim 4.83, these
7309 methods become optional, only taking effect if not specifically set in
7310 &_exim.conf_&.
7311
7312
7313 .section "LDAP quoting" "SECID68"
7314 .cindex "LDAP" "quoting"
7315 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7316 and the second because the LDAP query is represented as a URL. Furthermore,
7317 within an LDAP query, two different kinds of quoting are required. For this
7318 reason, there are two different LDAP-specific quoting operators.
7319
7320 The &%quote_ldap%& operator is designed for use on strings that are part of
7321 filter specifications. Conceptually, it first does the following conversions on
7322 the string:
7323 .code
7324 * => \2A
7325 ( => \28
7326 ) => \29
7327 \ => \5C
7328 .endd
7329 in accordance with RFC 2254. The resulting string is then quoted according
7330 to the rules for URLs, that is, all non-alphanumeric characters except
7331 .code
7332 ! $ ' - . _ ( ) * +
7333 .endd
7334 are converted to their hex values, preceded by a percent sign. For example:
7335 .code
7336 ${quote_ldap: a(bc)*, a<yz>; }
7337 .endd
7338 yields
7339 .code
7340 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7341 .endd
7342 Removing the URL quoting, this is (with a leading and a trailing space):
7343 .code
7344 a\28bc\29\2A, a<yz>;
7345 .endd
7346 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7347 base DN specifications in queries. Conceptually, it first converts the string
7348 by inserting a backslash in front of any of the following characters:
7349 .code
7350 , + " \ < > ;
7351 .endd
7352 It also inserts a backslash before any leading spaces or # characters, and
7353 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7354 is then quoted according to the rules for URLs. For example:
7355 .code
7356 ${quote_ldap_dn: a(bc)*, a<yz>; }
7357 .endd
7358 yields
7359 .code
7360 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7361 .endd
7362 Removing the URL quoting, this is (with a trailing space):
7363 .code
7364 \ a(bc)*\, a\<yz\>\;\
7365 .endd
7366 There are some further comments about quoting in the section on LDAP
7367 authentication below.
7368
7369
7370 .section "LDAP connections" "SECID69"
7371 .cindex "LDAP" "connections"
7372 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7373 is in use, via a Unix domain socket. The example given above does not specify
7374 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7375 by starting it with
7376 .code
7377 ldap://<hostname>:<port>/...
7378 .endd
7379 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7380 used. When no server is specified in a query, a list of default servers is
7381 taken from the &%ldap_default_servers%& configuration option. This supplies a
7382 colon-separated list of servers which are tried in turn until one successfully
7383 handles a query, or there is a serious error. Successful handling either
7384 returns the requested data, or indicates that it does not exist. Serious errors
7385 are syntactical, or multiple values when only a single value is expected.
7386 Errors which cause the next server to be tried are connection failures, bind
7387 failures, and timeouts.
7388
7389 For each server name in the list, a port number can be given. The standard way
7390 of specifying a host and port is to use a colon separator (RFC 1738). Because
7391 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7392 doubled. For example
7393 .code
7394 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7395 .endd
7396 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7397 to the LDAP library with no server name, and the library's default (normally
7398 the local host) is used.
7399
7400 If you are using the OpenLDAP library, you can connect to an LDAP server using
7401 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7402 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7403 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7404 not available.
7405
7406 For this type of connection, instead of a host name for the server, a pathname
7407 for the socket is required, and the port number is not relevant. The pathname
7408 can be specified either as an item in &%ldap_default_servers%&, or inline in
7409 the query. In the former case, you can have settings such as
7410 .code
7411 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7412 .endd
7413 When the pathname is given in the query, you have to escape the slashes as
7414 &`%2F`& to fit in with the LDAP URL syntax. For example:
7415 .code
7416 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7417 .endd
7418 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7419 a pathname, it uses the Unix domain socket code, even if the query actually
7420 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7421 socket connection. This behaviour means that you can use a setting of
7422 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7423 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7424 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7425 backup host.
7426
7427 If an explicit &`ldapi`& type is given in a query when a host name is
7428 specified, an error is diagnosed. However, if there are more items in
7429 &%ldap_default_servers%&, they are tried. In other words:
7430
7431 .ilist
7432 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7433 interface.
7434 .next
7435 Using &`ldapi`& with a host name causes an error.
7436 .endlist
7437
7438
7439 Using &`ldapi`& with no host or path in the query, and no setting of
7440 &%ldap_default_servers%&, does whatever the library does by default.
7441
7442
7443
7444 .section "LDAP authentication and control information" "SECID70"
7445 .cindex "LDAP" "authentication"
7446 The LDAP URL syntax provides no way of passing authentication and other control
7447 information to the server. To make this possible, the URL in an LDAP query may
7448 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7449 spaces. If a value contains spaces it must be enclosed in double quotes, and
7450 when double quotes are used, backslash is interpreted in the usual way inside
7451 them. The following names are recognized:
7452 .display
7453 &`DEREFERENCE`& set the dereferencing parameter
7454 &`NETTIME `& set a timeout for a network operation
7455 &`USER `& set the DN, for authenticating the LDAP bind
7456 &`PASS `& set the password, likewise
7457 &`REFERRALS `& set the referrals parameter
7458 &`SERVERS `& set alternate server list for this query only
7459 &`SIZE `& set the limit for the number of entries returned
7460 &`TIME `& set the maximum waiting time for a query
7461 .endd
7462 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7463 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7464 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7465 library from trying to follow referrals issued by the LDAP server.
7466
7467 .cindex LDAP timeout
7468 .cindex timeout "LDAP lookup"
7469 The name CONNECT is an obsolete name for NETTIME, retained for
7470 backwards compatibility. This timeout (specified as a number of seconds) is
7471 enforced from the client end for operations that can be carried out over a
7472 network. Specifically, it applies to network connections and calls to the
7473 &'ldap_result()'& function. If the value is greater than zero, it is used if
7474 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7475 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7476 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7477 Netscape SDK; for OpenLDAP no action is taken.
7478
7479 The TIME parameter (also a number of seconds) is passed to the server to
7480 set a server-side limit on the time taken to complete a search.
7481
7482 The SERVERS parameter allows you to specify an alternate list of ldap servers
7483 to use for an individual lookup. The global &%ldap_default_servers%& option provides a
7484 default list of ldap servers, and a single lookup can specify a single ldap
7485 server to use. But when you need to do a lookup with a list of servers that is
7486 different than the default list (maybe different order, maybe a completely
7487 different set of servers), the SERVERS parameter allows you to specify this
7488 alternate list (colon-separated).
7489
7490 Here is an example of an LDAP query in an Exim lookup that uses some of these
7491 values. This is a single line, folded to fit on the page:
7492 .code
7493 ${lookup ldap
7494 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7495 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7496 {$value}fail}
7497 .endd
7498 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7499 any of the auxiliary data. Exim configuration settings that include lookups
7500 which contain password information should be preceded by &"hide"& to prevent
7501 non-admin users from using the &%-bP%& option to see their values.
7502
7503 The auxiliary data items may be given in any order. The default is no
7504 connection timeout (the system timeout is used), no user or password, no limit
7505 on the number of entries returned, and no time limit on queries.
7506
7507 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7508 removes any URL quoting that it may contain before passing it LDAP. Apparently
7509 some libraries do this for themselves, but some do not. Removing the URL
7510 quoting has two advantages:
7511
7512 .ilist
7513 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7514 DNs as with DNs inside actual queries.
7515 .next
7516 It permits spaces inside USER= DNs.
7517 .endlist
7518
7519 For example, a setting such as
7520 .code
7521 USER=cn=${quote_ldap_dn:$1}
7522 .endd
7523 should work even if &$1$& contains spaces.
7524
7525 Expanded data for the PASS= value should be quoted using the &%quote%&
7526 expansion operator, rather than the LDAP quote operators. The only reason this
7527 field needs quoting is to ensure that it conforms to the Exim syntax, which
7528 does not allow unquoted spaces. For example:
7529 .code
7530 PASS=${quote:$3}
7531 .endd
7532 The LDAP authentication mechanism can be used to check passwords as part of
7533 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7534 &<<CHAPexpand>>&.
7535
7536
7537
7538 .section "Format of data returned by LDAP" "SECID71"
7539 .cindex "LDAP" "returned data formats"
7540 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7541 as a sequence of values, for example
7542 .code
7543 cn=manager,o=University of Cambridge,c=UK
7544 .endd
7545 The &(ldap)& lookup type generates an error if more than one entry matches the
7546 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7547 the result between the data from different entries. It is possible for multiple
7548 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7549 you know that whatever values are returned all came from a single entry in the
7550 directory.
7551
7552 In the common case where you specify a single attribute in your LDAP query, the
7553 result is not quoted, and does not contain the attribute name. If the attribute
7554 has multiple values, they are separated by commas. Any comma that is
7555 part of an attribute's value is doubled.
7556
7557 If you specify multiple attributes, the result contains space-separated, quoted
7558 strings, each preceded by the attribute name and an equals sign. Within the
7559 quotes, the quote character, backslash, and newline are escaped with
7560 backslashes, and commas are used to separate multiple values for the attribute.
7561 Any commas in attribute values are doubled
7562 (permitting treatment of the values as a comma-separated list).
7563 Apart from the escaping, the string within quotes takes the same form as the
7564 output when a single attribute is requested. Specifying no attributes is the
7565 same as specifying all of an entry's attributes.
7566
7567 Here are some examples of the output format. The first line of each pair is an
7568 LDAP query, and the second is the data that is returned. The attribute called
7569 &%attr1%& has two values, one of them with an embedded comma, whereas
7570 &%attr2%& has only one value. Both attributes are derived from &%attr%&
7571 (they have SUP &%attr%& in their schema definitions).
7572
7573 .code
7574 ldap:///o=base?attr1?sub?(uid=fred)
7575 value1.1,value1,,2
7576
7577 ldap:///o=base?attr2?sub?(uid=fred)
7578 value two
7579
7580 ldap:///o=base?attr?sub?(uid=fred)
7581 value1.1,value1,,2,value two
7582
7583 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7584 attr1="value1.1,value1,,2" attr2="value two"
7585
7586 ldap:///o=base??sub?(uid=fred)
7587 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
7588 .endd
7589 You can
7590 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7591 results of LDAP lookups.
7592 The &%extract%& operator in string expansions can be used to pick out
7593 individual fields from data that consists of &'key'&=&'value'& pairs.
7594 The &%listextract%& operator should be used to pick out individual values
7595 of attributes, even when only a single value is expected.
7596 The doubling of embedded commas allows you to use the returned data as a
7597 comma separated list (using the "<," syntax for changing the input list separator).
7598
7599
7600
7601
7602 .section "More about NIS+" "SECTnisplus"
7603 .cindex "NIS+ lookup type"
7604 .cindex "lookup" "NIS+"
7605 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7606 and field name. If this is given, the result of a successful query is the
7607 contents of the named field; otherwise the result consists of a concatenation
7608 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
7609 values containing spaces are quoted. For example, the query
7610 .code
7611 [name=mg1456],passwd.org_dir
7612 .endd
7613 might return the string
7614 .code
7615 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
7616 home=/home/mg1456 shell=/bin/bash shadow=""
7617 .endd
7618 (split over two lines here to fit on the page), whereas
7619 .code
7620 [name=mg1456],passwd.org_dir:gcos
7621 .endd
7622 would just return
7623 .code
7624 Martin Guerre
7625 .endd
7626 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
7627 for the given indexed key. The effect of the &%quote_nisplus%& expansion
7628 operator is to double any quote characters within the text.
7629
7630
7631
7632 .section "SQL lookups" "SECTsql"
7633 .cindex "SQL lookup types"
7634 .cindex "MySQL" "lookup type"
7635 .cindex "PostgreSQL lookup type"
7636 .cindex "lookup" "MySQL"
7637 .cindex "lookup" "PostgreSQL"
7638 .cindex "Oracle" "lookup type"
7639 .cindex "lookup" "Oracle"
7640 .cindex "InterBase lookup type"
7641 .cindex "lookup" "InterBase"
7642 .cindex "Redis lookup type"
7643 .cindex lookup Redis
7644 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, Redis,
7645 and SQLite
7646 databases. Queries for these databases contain SQL statements, so an example
7647 might be
7648 .code
7649 ${lookup mysql{select mailbox from users where id='userx'}\
7650 {$value}fail}
7651 .endd
7652 If the result of the query contains more than one field, the data for each
7653 field in the row is returned, preceded by its name, so the result of
7654 .code
7655 ${lookup pgsql{select home,name from users where id='userx'}\
7656 {$value}}
7657 .endd
7658 might be
7659 .code
7660 home=/home/userx name="Mister X"
7661 .endd
7662 Empty values and values containing spaces are double quoted, with embedded
7663 quotes escaped by a backslash. If the result of the query contains just one
7664 field, the value is passed back verbatim, without a field name, for example:
7665 .code
7666 Mister X
7667 .endd
7668 If the result of the query yields more than one row, it is all concatenated,
7669 with a newline between the data for each row.
7670
7671
7672 .section "More about MySQL, PostgreSQL, Oracle, InterBase, and Redis" "SECID72"
7673 .cindex "MySQL" "lookup type"
7674 .cindex "PostgreSQL lookup type"
7675 .cindex "lookup" "MySQL"
7676 .cindex "lookup" "PostgreSQL"
7677 .cindex "Oracle" "lookup type"
7678 .cindex "lookup" "Oracle"
7679 .cindex "InterBase lookup type"
7680 .cindex "lookup" "InterBase"
7681 .cindex "Redis lookup type"
7682 .cindex lookup Redis
7683 If any MySQL, PostgreSQL, Oracle, InterBase or Redis lookups are used, the
7684 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, &%ibase_servers%&,
7685 or &%redis_servers%&
7686 option (as appropriate) must be set to a colon-separated list of server
7687 information.
7688 (For MySQL and PostgreSQL, the global option need not be set if all
7689 queries contain their own server information &-- see section
7690 &<<SECTspeserque>>&.)
7691 For all but Redis
7692 each item in the list is a slash-separated list of four
7693 items: host name, database name, user name, and password. In the case of
7694 Oracle, the host name field is used for the &"service name"&, and the database
7695 name field is not used and should be empty. For example:
7696 .code
7697 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
7698 .endd
7699 Because password data is sensitive, you should always precede the setting with
7700 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
7701 option. Here is an example where two MySQL servers are listed:
7702 .code
7703 hide mysql_servers = localhost/users/root/secret:\
7704 otherhost/users/root/othersecret
7705 .endd
7706 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
7707 because this is a colon-separated list, the colon has to be doubled. For each
7708 query, these parameter groups are tried in order until a connection is made and
7709 a query is successfully processed. The result of a query may be that no data is
7710 found, but that is still a successful query. In other words, the list of
7711 servers provides a backup facility, not a list of different places to look.
7712
7713 For Redis the global option need not be specified if all queries contain their
7714 own server information &-- see section &<<SECTspeserque>>&.
7715 If specified, the option must be set to a colon-separated list of server
7716 information.
7717 Each item in the list is a slash-separated list of three items:
7718 host, database number, and password.
7719 .olist
7720 The host is required and may be either an IPv4 address and optional
7721 port number (separated by a colon, which needs doubling due to the
7722 higher-level list), or a Unix socket pathname enclosed in parentheses
7723 .next
7724 The database number is optional; if present that number is selected in the backend
7725 .next
7726 The password is optional; if present it is used to authenticate to the backend
7727 .endlist
7728
7729 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
7730 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
7731 respectively, and the characters single-quote, double-quote, and backslash
7732 itself are escaped with backslashes.
7733
7734 The &%quote_redis%& expansion operator
7735 escapes whitespace and backslash characters with a backslash.
7736
7737 .section "Specifying the server in the query" "SECTspeserque"
7738 For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
7739 it is possible to specify a list of servers with an individual query. This is
7740 done by starting the query with
7741 .display
7742 &`servers=`&&'server1:server2:server3:...'&&`;`&
7743 .endd
7744 Each item in the list may take one of two forms:
7745 .olist
7746 If it contains no slashes it is assumed to be just a host name. The appropriate
7747 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
7748 of the same name, and the remaining parameters (database, user, password) are
7749 taken from there.
7750 .next
7751 If it contains any slashes, it is taken as a complete parameter set.
7752 .endlist
7753 The list of servers is used in exactly the same way as the global list.
7754 Once a connection to a server has happened and a query has been
7755 successfully executed, processing of the lookup ceases.
7756
7757 This feature is intended for use in master/slave situations where updates
7758 are occurring and you want to update the master rather than a slave. If the
7759 master is in the list as a backup for reading, you might have a global setting
7760 like this:
7761 .code
7762 mysql_servers = slave1/db/name/pw:\
7763 slave2/db/name/pw:\
7764 master/db/name/pw
7765 .endd
7766 In an updating lookup, you could then write:
7767 .code
7768 ${lookup mysql{servers=master; UPDATE ...} }
7769 .endd
7770 That query would then be sent only to the master server. If, on the other hand,
7771 the master is not to be used for reading, and so is not present in the global
7772 option, you can still update it by a query of this form:
7773 .code
7774 ${lookup pgsql{servers=master/db/name/pw; UPDATE ...} }
7775 .endd
7776
7777
7778 .section "Special MySQL features" "SECID73"
7779 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
7780 causes a connection to the server on the local host by means of a Unix domain
7781 socket. An alternate socket can be specified in parentheses.
7782 An option group name for MySQL option files can be specified in square brackets;
7783 the default value is &"exim"&.
7784 The full syntax of each item in &%mysql_servers%& is:
7785 .display
7786 <&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
7787 <&'database'&>/<&'user'&>/<&'password'&>
7788 .endd
7789 Any of the four sub-parts of the first field can be omitted. For normal use on
7790 the local host it can be left blank or set to just &"localhost"&.
7791
7792 No database need be supplied &-- but if it is absent here, it must be given in
7793 the queries.
7794
7795 If a MySQL query is issued that does not request any data (an insert, update,
7796 or delete command), the result of the lookup is the number of rows affected.
7797
7798 &*Warning*&: This can be misleading. If an update does not actually change
7799 anything (for example, setting a field to the value it already has), the result
7800 is zero because no rows are affected.
7801
7802
7803 .section "Special PostgreSQL features" "SECID74"
7804 PostgreSQL lookups can also use Unix domain socket connections to the database.
7805 This is usually faster and costs less CPU time than a TCP/IP connection.
7806 However it can be used only if the mail server runs on the same machine as the
7807 database server. A configuration line for PostgreSQL via Unix domain sockets
7808 looks like this:
7809 .code
7810 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
7811 .endd
7812 In other words, instead of supplying a host name, a path to the socket is
7813 given. The path name is enclosed in parentheses so that its slashes aren't
7814 visually confused with the delimiters for the other server parameters.
7815
7816 If a PostgreSQL query is issued that does not request any data (an insert,
7817 update, or delete command), the result of the lookup is the number of rows
7818 affected.
7819
7820 .section "More about SQLite" "SECTsqlite"
7821 .cindex "lookup" "SQLite"
7822 .cindex "sqlite lookup type"
7823 SQLite is different to the other SQL lookups because a file name is required in
7824 addition to the SQL query. An SQLite database is a single file, and there is no
7825 daemon as in the other SQL databases. The interface to Exim requires the name
7826 of the file, as an absolute path, to be given at the start of the query. It is
7827 separated from the query by white space. This means that the path name cannot
7828 contain white space. Here is a lookup expansion example:
7829 .code
7830 ${lookup sqlite {/some/thing/sqlitedb \
7831 select name from aliases where id='userx';}}
7832 .endd
7833 In a list, the syntax is similar. For example:
7834 .code
7835 domainlist relay_to_domains = sqlite;/some/thing/sqlitedb \
7836 select * from relays where ip='$sender_host_address';
7837 .endd
7838 The only character affected by the &%quote_sqlite%& operator is a single
7839 quote, which it doubles.
7840
7841 .cindex timeout SQLite
7842 .cindex sqlite "lookup timeout"
7843 The SQLite library handles multiple simultaneous accesses to the database
7844 internally. Multiple readers are permitted, but only one process can
7845 update at once. Attempts to access the database while it is being updated
7846 are rejected after a timeout period, during which the SQLite library
7847 waits for the lock to be released. In Exim, the default timeout is set
7848 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
7849 option.
7850
7851 .section "More about Redis" "SECTredis"
7852 .cindex "lookup" "Redis"
7853 .cindex "redis lookup type"
7854 Redis is a non-SQL database. Commands are simple get and set.
7855 Examples:
7856 .code
7857 ${lookup redis{set keyname ${quote_redis:objvalue plus}}}
7858 ${lookup redis{get keyname}}
7859 .endd
7860
7861 As of release 4.91, "lightweight" support for Redis Cluster is available.
7862 Requires &%redis_servers%& list to contain all the servers in the cluster, all
7863 of which must be reachable from the running exim instance. If the cluster has
7864 master/slave replication, the list must contain all the master and slave
7865 servers.
7866
7867 When the Redis Cluster returns a "MOVED" response to a query, Exim does not
7868 immediately follow the redirection but treats the response as a DEFER, moving on
7869 to the next server in the &%redis_servers%& list until the correct server is
7870 reached.
7871
7872 .ecindex IIDfidalo1
7873 .ecindex IIDfidalo2
7874
7875
7876 . ////////////////////////////////////////////////////////////////////////////
7877 . ////////////////////////////////////////////////////////////////////////////
7878
7879 .chapter "Domain, host, address, and local part lists" &&&
7880 "CHAPdomhosaddlists" &&&
7881 "Domain, host, and address lists"
7882 .scindex IIDdohoadli "lists of domains; hosts; etc."
7883 A number of Exim configuration options contain lists of domains, hosts,
7884 email addresses, or local parts. For example, the &%hold_domains%& option
7885 contains a list of domains whose delivery is currently suspended. These lists
7886 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
7887 arguments to expansion conditions such as &%match_domain%&.
7888
7889 Each item in one of these lists is a pattern to be matched against a domain,
7890 host, email address, or local part, respectively. In the sections below, the
7891 different types of pattern for each case are described, but first we cover some
7892 general facilities that apply to all four kinds of list.
7893
7894 Note that other parts of Exim use a &'string list'& which does not
7895 support all the complexity available in
7896 domain, host, address and local part lists.
7897
7898
7899
7900 .section "Expansion of lists" "SECTlistexpand"
7901 .cindex "expansion" "of lists"
7902 Each list is expanded as a single string before it is used.
7903
7904 &'Exception: the router headers_remove option, where list-item
7905 splitting is done before string-expansion.'&
7906
7907 The result of
7908 expansion must be a list, possibly containing empty items, which is split up
7909 into separate items for matching. By default, colon is the separator character,
7910 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
7911 &<<SECTempitelis>>& for details of the list syntax; the second of these
7912 discusses the way to specify empty list items.
7913
7914
7915 If the string expansion is forced to fail, Exim behaves as if the item it is
7916 testing (domain, host, address, or local part) is not in the list. Other
7917 expansion failures cause temporary errors.
7918
7919 If an item in a list is a regular expression, backslashes, dollars and possibly
7920 other special characters in the expression must be protected against
7921 misinterpretation by the string expander. The easiest way to do this is to use
7922 the &`\N`& expansion feature to indicate that the contents of the regular
7923 expression should not be expanded. For example, in an ACL you might have:
7924 .code
7925 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
7926 ${lookup{$domain}lsearch{/badsenders/bydomain}}
7927 .endd
7928 The first item is a regular expression that is protected from expansion by
7929 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
7930 senders based on the receiving domain.
7931
7932
7933
7934
7935 .section "Negated items in lists" "SECID76"
7936 .cindex "list" "negation"
7937 .cindex "negation" "in lists"
7938 Items in a list may be positive or negative. Negative items are indicated by a
7939 leading exclamation mark, which may be followed by optional white space. A list
7940 defines a set of items (domains, etc). When Exim processes one of these lists,
7941 it is trying to find out whether a domain, host, address, or local part
7942 (respectively) is in the set that is defined by the list. It works like this:
7943
7944 The list is scanned from left to right. If a positive item is matched, the
7945 subject that is being checked is in the set; if a negative item is matched, the
7946 subject is not in the set. If the end of the list is reached without the
7947 subject having matched any of the patterns, it is in the set if the last item
7948 was a negative one, but not if it was a positive one. For example, the list in
7949 .code
7950 domainlist relay_to_domains = !a.b.c : *.b.c
7951 .endd
7952 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
7953 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
7954 list is positive. However, if the setting were
7955 .code
7956 domainlist relay_to_domains = !a.b.c
7957 .endd
7958 then all domains other than &'a.b.c'& would match because the last item in the
7959 list is negative. In other words, a list that ends with a negative item behaves
7960 as if it had an extra item &`:*`& on the end.
7961
7962 Another way of thinking about positive and negative items in lists is to read
7963 the connector as &"or"& after a positive item and as &"and"& after a negative
7964 item.
7965
7966
7967
7968 .section "File names in lists" "SECTfilnamlis"
7969 .cindex "list" "file name in"
7970 If an item in a domain, host, address, or local part list is an absolute file
7971 name (beginning with a slash character), each line of the file is read and
7972 processed as if it were an independent item in the list, except that further
7973 file names are not allowed,
7974 and no expansion of the data from the file takes place.
7975 Empty lines in the file are ignored, and the file may also contain comment
7976 lines:
7977
7978 .ilist
7979 For domain and host lists, if a # character appears anywhere in a line of the
7980 file, it and all following characters are ignored.
7981 .next
7982 Because local parts may legitimately contain # characters, a comment in an
7983 address list or local part list file is recognized only if # is preceded by
7984 white space or the start of the line. For example:
7985 .code
7986 not#comment@x.y.z # but this is a comment
7987 .endd
7988 .endlist
7989
7990 Putting a file name in a list has the same effect as inserting each line of the
7991 file as an item in the list (blank lines and comments excepted). However, there
7992 is one important difference: the file is read each time the list is processed,
7993 so if its contents vary over time, Exim's behaviour changes.
7994
7995 If a file name is preceded by an exclamation mark, the sense of any match
7996 within the file is inverted. For example, if
7997 .code
7998 hold_domains = !/etc/nohold-domains
7999 .endd
8000 and the file contains the lines
8001 .code
8002 !a.b.c
8003 *.b.c
8004 .endd
8005 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
8006 any domain matching &`*.b.c`& is not.
8007
8008
8009
8010 .section "An lsearch file is not an out-of-line list" "SECID77"
8011 As will be described in the sections that follow, lookups can be used in lists
8012 to provide indexed methods of checking list membership. There has been some
8013 confusion about the way &(lsearch)& lookups work in lists. Because
8014 an &(lsearch)& file contains plain text and is scanned sequentially, it is
8015 sometimes thought that it is allowed to contain wild cards and other kinds of
8016 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
8017 always fixed strings, just as for any other single-key lookup type.
8018
8019 If you want to use a file to contain wild-card patterns that form part of a
8020 list, just give the file name on its own, without a search type, as described
8021 in the previous section. You could also use the &(wildlsearch)& or
8022 &(nwildlsearch)&, but there is no advantage in doing this.
8023
8024
8025
8026
8027 .section "Named lists" "SECTnamedlists"
8028 .cindex "named lists"
8029 .cindex "list" "named"
8030 A list of domains, hosts, email addresses, or local parts can be given a name
8031 which is then used to refer to the list elsewhere in the configuration. This is
8032 particularly convenient if the same list is required in several different
8033 places. It also allows lists to be given meaningful names, which can improve
8034 the readability of the configuration. For example, it is conventional to define
8035 a domain list called &'local_domains'& for all the domains that are handled
8036 locally on a host, using a configuration line such as
8037 .code
8038 domainlist local_domains = localhost:my.dom.example
8039 .endd
8040 Named lists are referenced by giving their name preceded by a plus sign, so,
8041 for example, a router that is intended to handle local domains would be
8042 configured with the line
8043 .code
8044 domains = +local_domains
8045 .endd
8046 The first router in a configuration is often one that handles all domains
8047 except the local ones, using a configuration with a negated item like this:
8048 .code
8049 dnslookup:
8050 driver = dnslookup
8051 domains = ! +local_domains
8052 transport = remote_smtp
8053 no_more
8054 .endd
8055 The four kinds of named list are created by configuration lines starting with
8056 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
8057 respectively. Then there follows the name that you are defining, followed by an
8058 equals sign and the list itself. For example:
8059 .code
8060 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
8061 addresslist bad_senders = cdb;/etc/badsenders
8062 .endd
8063 A named list may refer to other named lists:
8064 .code
8065 domainlist dom1 = first.example : second.example
8066 domainlist dom2 = +dom1 : third.example
8067 domainlist dom3 = fourth.example : +dom2 : fifth.example
8068 .endd
8069 &*Warning*&: If the last item in a referenced list is a negative one, the
8070 effect may not be what you intended, because the negation does not propagate
8071 out to the higher level. For example, consider:
8072 .code
8073 domainlist dom1 = !a.b
8074 domainlist dom2 = +dom1 : *.b
8075 .endd
8076 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
8077 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
8078 means it matches the second list as well. The effect is not the same as
8079 .code
8080 domainlist dom2 = !a.b : *.b
8081 .endd
8082 where &'x.y'& does not match. It's best to avoid negation altogether in
8083 referenced lists if you can.
8084
8085 Named lists may have a performance advantage. When Exim is routing an
8086 address or checking an incoming message, it caches the result of tests on named
8087 lists. So, if you have a setting such as
8088 .code
8089 domains = +local_domains
8090 .endd
8091 on several of your routers
8092 or in several ACL statements,
8093 the actual test is done only for the first one. However, the caching works only
8094 if there are no expansions within the list itself or any sublists that it
8095 references. In other words, caching happens only for lists that are known to be
8096 the same each time they are referenced.
8097
8098 By default, there may be up to 16 named lists of each type. This limit can be
8099 extended by changing a compile-time variable. The use of domain and host lists
8100 is recommended for concepts such as local domains, relay domains, and relay
8101 hosts. The default configuration is set up like this.
8102
8103
8104
8105 .section "Named lists compared with macros" "SECID78"
8106 .cindex "list" "named compared with macro"
8107 .cindex "macro" "compared with named list"
8108 At first sight, named lists might seem to be no different from macros in the
8109 configuration file. However, macros are just textual substitutions. If you
8110 write
8111 .code
8112 ALIST = host1 : host2
8113 auth_advertise_hosts = !ALIST
8114 .endd
8115 it probably won't do what you want, because that is exactly the same as
8116 .code
8117 auth_advertise_hosts = !host1 : host2
8118 .endd
8119 Notice that the second host name is not negated. However, if you use a host
8120 list, and write
8121 .code
8122 hostlist alist = host1 : host2
8123 auth_advertise_hosts = ! +alist
8124 .endd
8125 the negation applies to the whole list, and so that is equivalent to
8126 .code
8127 auth_advertise_hosts = !host1 : !host2
8128 .endd
8129
8130
8131 .section "Named list caching" "SECID79"
8132 .cindex "list" "caching of named"
8133 .cindex "caching" "named lists"
8134 While processing a message, Exim caches the result of checking a named list if
8135 it is sure that the list is the same each time. In practice, this means that
8136 the cache operates only if the list contains no $ characters, which guarantees
8137 that it will not change when it is expanded. Sometimes, however, you may have
8138 an expanded list that you know will be the same each time within a given
8139 message. For example:
8140 .code
8141 domainlist special_domains = \
8142 ${lookup{$sender_host_address}cdb{/some/file}}
8143 .endd
8144 This provides a list of domains that depends only on the sending host's IP
8145 address. If this domain list is referenced a number of times (for example,
8146 in several ACL lines, or in several routers) the result of the check is not
8147 cached by default, because Exim does not know that it is going to be the
8148 same list each time.
8149
8150 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
8151 cache the result anyway. For example:
8152 .code
8153 domainlist_cache special_domains = ${lookup{...
8154 .endd
8155 If you do this, you should be absolutely sure that caching is going to do
8156 the right thing in all cases. When in doubt, leave it out.
8157
8158
8159
8160 .section "Domain lists" "SECTdomainlist"
8161 .cindex "domain list" "patterns for"
8162 .cindex "list" "domain list"
8163 Domain lists contain patterns that are to be matched against a mail domain.
8164 The following types of item may appear in domain lists:
8165
8166 .ilist
8167 .cindex "primary host name"
8168 .cindex "host name" "matched in domain list"
8169 .oindex "&%primary_hostname%&"
8170 .cindex "domain list" "matching primary host name"
8171 .cindex "@ in a domain list"
8172 If a pattern consists of a single @ character, it matches the local host name,
8173 as set by the &%primary_hostname%& option (or defaulted). This makes it
8174 possible to use the same configuration file on several different hosts that
8175 differ only in their names.
8176 .next
8177 .cindex "@[] in a domain list"
8178 .cindex "domain list" "matching local IP interfaces"
8179 .cindex "domain literal"
8180 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
8181 in square brackets (as in an email address that contains a domain literal), but
8182 only if that IP address is recognized as local for email routing purposes. The
8183 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
8184 control which of a host's several IP addresses are treated as local.
8185 In today's Internet, the use of domain literals is controversial.
8186 .next
8187 .cindex "@mx_any"
8188 .cindex "@mx_primary"
8189 .cindex "@mx_secondary"
8190 .cindex "domain list" "matching MX pointers to local host"
8191 If a pattern consists of the string &`@mx_any`& it matches any domain that
8192 has an MX record pointing to the local host or to any host that is listed in
8193 .oindex "&%hosts_treat_as_local%&"
8194 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
8195 are similar, except that the first matches only when a primary MX target is the
8196 local host, and the second only when no primary MX target is the local host,
8197 but a secondary MX target is. &"Primary"& means an MX record with the lowest
8198 preference value &-- there may of course be more than one of them.
8199
8200 The MX lookup that takes place when matching a pattern of this type is
8201 performed with the resolver options for widening names turned off. Thus, for
8202 example, a single-component domain will &'not'& be expanded by adding the
8203 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
8204 options of the &(dnslookup)& router for a discussion of domain widening.
8205
8206 Sometimes you may want to ignore certain IP addresses when using one of these
8207 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
8208 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
8209 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
8210 on a router). For example:
8211 .code
8212 domains = @mx_any/ignore=127.0.0.1
8213 .endd
8214 This example matches any domain that has an MX record pointing to one of
8215 the local host's IP addresses other than 127.0.0.1.
8216
8217 The list of IP addresses is in fact processed by the same code that processes
8218 host lists, so it may contain CIDR-coded network specifications and it may also
8219 contain negative items.
8220
8221 Because the list of IP addresses is a sublist within a domain list, you have to
8222 be careful about delimiters if there is more than one address. Like any other
8223 list, the default delimiter can be changed. Thus, you might have:
8224 .code
8225 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
8226 an.other.domain : ...
8227 .endd
8228 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
8229 involved, it is easiest to change the delimiter for the main list as well:
8230 .code
8231 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
8232 an.other.domain ? ...
8233 .endd
8234 .next
8235 .cindex "asterisk" "in domain list"
8236 .cindex "domain list" "asterisk in"
8237 .cindex "domain list" "matching &""ends with""&"
8238 If a pattern starts with an asterisk, the remaining characters of the pattern
8239 are compared with the terminating characters of the domain. The use of &"*"& in
8240 domain lists differs from its use in partial matching lookups. In a domain
8241 list, the character following the asterisk need not be a dot, whereas partial
8242 matching works only in terms of dot-separated components. For example, a domain
8243 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
8244 &'cipher.key.ex'&.
8245
8246 .next
8247 .cindex "regular expressions" "in domain list"
8248 .cindex "domain list" "matching regular expression"
8249 If a pattern starts with a circumflex character, it is treated as a regular
8250 expression, and matched against the domain using a regular expression matching
8251 function. The circumflex is treated as part of the regular expression.
8252 Email domains are case-independent, so this regular expression match is by
8253 default case-independent, but you can make it case-dependent by starting it
8254 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
8255 are given in chapter &<<CHAPregexp>>&.
8256
8257 &*Warning*&: Because domain lists are expanded before being processed, you
8258 must escape any backslash and dollar characters in the regular expression, or
8259 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
8260 it is not to be expanded (unless you really do want to build a regular
8261 expression by expansion, of course).
8262 .next
8263 .cindex "lookup" "in domain list"
8264 .cindex "domain list" "matching by lookup"
8265 If a pattern starts with the name of a single-key lookup type followed by a
8266 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
8267 must be a file name in a suitable format for the lookup type. For example, for
8268 &"cdb;"& it must be an absolute path:
8269 .code
8270 domains = cdb;/etc/mail/local_domains.cdb
8271 .endd
8272 The appropriate type of lookup is done on the file using the domain name as the
8273 key. In most cases, the data that is looked up is not used; Exim is interested
8274 only in whether or not the key is present in the file. However, when a lookup
8275 is used for the &%domains%& option on a router
8276 or a &%domains%& condition in an ACL statement, the data is preserved in the
8277 &$domain_data$& variable and can be referred to in other router options or
8278 other statements in the same ACL.
8279
8280 .next
8281 Any of the single-key lookup type names may be preceded by
8282 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8283 .code
8284 domains = partial-dbm;/partial/domains
8285 .endd
8286 This causes partial matching logic to be invoked; a description of how this
8287 works is given in section &<<SECTpartiallookup>>&.
8288
8289 .next
8290 .cindex "asterisk" "in lookup type"
8291 Any of the single-key lookup types may be followed by an asterisk. This causes
8292 a default lookup for a key consisting of a single asterisk to be done if the
8293 original lookup fails. This is not a useful feature when using a domain list to
8294 select particular domains (because any domain would match), but it might have
8295 value if the result of the lookup is being used via the &$domain_data$&
8296 expansion variable.
8297 .next
8298 If the pattern starts with the name of a query-style lookup type followed by a
8299 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8300 pattern must be an appropriate query for the lookup type, as described in
8301 chapter &<<CHAPfdlookup>>&. For example:
8302 .code
8303 hold_domains = mysql;select domain from holdlist \
8304 where domain = '${quote_mysql:$domain}';
8305 .endd
8306 In most cases, the data that is looked up is not used (so for an SQL query, for
8307 example, it doesn't matter what field you select). Exim is interested only in
8308 whether or not the query succeeds. However, when a lookup is used for the
8309 &%domains%& option on a router, the data is preserved in the &$domain_data$&
8310 variable and can be referred to in other options.
8311 .next
8312 .cindex "domain list" "matching literal domain name"
8313 If none of the above cases apply, a caseless textual comparison is made
8314 between the pattern and the domain.
8315 .endlist
8316
8317 Here is an example that uses several different kinds of pattern:
8318 .code
8319 domainlist funny_domains = \
8320 @ : \
8321 lib.unseen.edu : \
8322 *.foundation.fict.example : \
8323 \N^[1-2]\d{3}\.fict\.example$\N : \
8324 partial-dbm;/opt/data/penguin/book : \
8325 nis;domains.byname : \
8326 nisplus;[name=$domain,status=local],domains.org_dir
8327 .endd
8328 There are obvious processing trade-offs among the various matching modes. Using
8329 an asterisk is faster than a regular expression, and listing a few names
8330 explicitly probably is too. The use of a file or database lookup is expensive,
8331 but may be the only option if hundreds of names are required. Because the
8332 patterns are tested in order, it makes sense to put the most commonly matched
8333 patterns earlier.
8334
8335
8336
8337 .section "Host lists" "SECThostlist"
8338 .cindex "host list" "patterns in"
8339 .cindex "list" "host list"
8340 Host lists are used to control what remote hosts are allowed to do. For
8341 example, some hosts may be allowed to use the local host as a relay, and some
8342 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8343 two different ways, by name or by IP address. In a host list, some types of
8344 pattern are matched to a host name, and some are matched to an IP address.
8345 You need to be particularly careful with this when single-key lookups are
8346 involved, to ensure that the right value is being used as the key.
8347
8348
8349 .section "Special host list patterns" "SECID80"
8350 .cindex "empty item in hosts list"
8351 .cindex "host list" "empty string in"
8352 If a host list item is the empty string, it matches only when no remote host is
8353 involved. This is the case when a message is being received from a local
8354 process using SMTP on the standard input, that is, when a TCP/IP connection is
8355 not used.
8356
8357 .cindex "asterisk" "in host list"
8358 The special pattern &"*"& in a host list matches any host or no host. Neither
8359 the IP address nor the name is actually inspected.
8360
8361
8362
8363 .section "Host list patterns that match by IP address" "SECThoslispatip"
8364 .cindex "host list" "matching IP addresses"
8365 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8366 the incoming address actually appears in the IPv6 host as
8367 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8368 list, it is converted into a traditional IPv4 address first. (Not all operating
8369 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8370 concerns.)
8371
8372 The following types of pattern in a host list check the remote host by
8373 inspecting its IP address:
8374
8375 .ilist
8376 If the pattern is a plain domain name (not a regular expression, not starting
8377 with *, not a lookup of any kind), Exim calls the operating system function
8378 to find the associated IP address(es). Exim uses the newer
8379 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8380 This typically causes a forward DNS lookup of the name. The result is compared
8381 with the IP address of the subject host.
8382
8383 If there is a temporary problem (such as a DNS timeout) with the host name
8384 lookup, a temporary error occurs. For example, if the list is being used in an
8385 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8386 temporary SMTP error code. If no IP address can be found for the host name,
8387 what happens is described in section &<<SECTbehipnot>>& below.
8388
8389 .next
8390 .cindex "@ in a host list"
8391 If the pattern is &"@"&, the primary host name is substituted and used as a
8392 domain name, as just described.
8393
8394 .next
8395 If the pattern is an IP address, it is matched against the IP address of the
8396 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8397 IPv6 addresses can be given in colon-separated format, but the colons have to
8398 be doubled so as not to be taken as item separators when the default list
8399 separator is used. IPv6 addresses are recognized even when Exim is compiled
8400 without IPv6 support. This means that if they appear in a host list on an
8401 IPv4-only host, Exim will not treat them as host names. They are just addresses
8402 that can never match a client host.
8403
8404 .next
8405 .cindex "@[] in a host list"
8406 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8407 the local host. For example, if the local host is an IPv4 host with one
8408 interface address 10.45.23.56, these two ACL statements have the same effect:
8409 .code
8410 accept hosts = 127.0.0.1 : 10.45.23.56
8411 accept hosts = @[]
8412 .endd
8413 .next
8414 .cindex "CIDR notation"
8415 If the pattern is an IP address followed by a slash and a mask length (for
8416 example 10.11.42.0/24), it is matched against the IP address of the subject
8417 host under the given mask. This allows, an entire network of hosts to be
8418 included (or excluded) by a single item. The mask uses CIDR notation; it
8419 specifies the number of address bits that must match, starting from the most
8420 significant end of the address.
8421
8422 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8423 of a range of addresses. It is the number of bits in the network portion of the
8424 address. The above example specifies a 24-bit netmask, so it matches all 256
8425 addresses in the 10.11.42.0 network. An item such as
8426 .code
8427 192.168.23.236/31
8428 .endd
8429 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8430 32 for an IPv4 address is the same as no mask at all; just a single address
8431 matches.
8432
8433 Here is another example which shows an IPv4 and an IPv6 network:
8434 .code
8435 recipient_unqualified_hosts = 192.168.0.0/16: \
8436 3ffe::ffff::836f::::/48
8437 .endd
8438 The doubling of list separator characters applies only when these items
8439 appear inline in a host list. It is not required when indirecting via a file.
8440 For example:
8441 .code
8442 recipient_unqualified_hosts = /opt/exim/unqualnets
8443 .endd
8444 could make use of a file containing
8445 .code
8446 172.16.0.0/12
8447 3ffe:ffff:836f::/48
8448 .endd
8449 to have exactly the same effect as the previous example. When listing IPv6
8450 addresses inline, it is usually more convenient to use the facility for
8451 changing separator characters. This list contains the same two networks:
8452 .code
8453 recipient_unqualified_hosts = <; 172.16.0.0/12; \
8454 3ffe:ffff:836f::/48
8455 .endd
8456 The separator is changed to semicolon by the leading &"<;"& at the start of the
8457 list.
8458 .endlist
8459
8460
8461
8462 .section "Host list patterns for single-key lookups by host address" &&&
8463 "SECThoslispatsikey"
8464 .cindex "host list" "lookup of IP address"
8465 When a host is to be identified by a single-key lookup of its complete IP
8466 address, the pattern takes this form:
8467 .display
8468 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8469 .endd
8470 For example:
8471 .code
8472 hosts_lookup = net-cdb;/hosts-by-ip.db
8473 .endd
8474 The text form of the IP address of the subject host is used as the lookup key.
8475 IPv6 addresses are converted to an unabbreviated form, using lower case
8476 letters, with dots as separators because colon is the key terminator in
8477 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
8478 quoting the keys, but this is a facility that was added later.] The data
8479 returned by the lookup is not used.
8480
8481 .cindex "IP address" "masking"
8482 .cindex "host list" "masked IP address"
8483 Single-key lookups can also be performed using masked IP addresses, using
8484 patterns of this form:
8485 .display
8486 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8487 .endd
8488 For example:
8489 .code
8490 net24-dbm;/networks.db
8491 .endd
8492 The IP address of the subject host is masked using <&'number'&> as the mask
8493 length. A textual string is constructed from the masked value, followed by the
8494 mask, and this is used as the lookup key. For example, if the host's IP address
8495 is 192.168.34.6, the key that is looked up for the above example is
8496 &"192.168.34.0/24"&.
8497
8498 When an IPv6 address is converted to a string, dots are normally used instead
8499 of colons, so that keys in &(lsearch)& files need not contain colons (which
8500 terminate &(lsearch)& keys). This was implemented some time before the ability
8501 to quote keys was made available in &(lsearch)& files. However, the more
8502 recently implemented &(iplsearch)& files do require colons in IPv6 keys
8503 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
8504 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
8505 converted using colons and not dots. In all cases, full, unabbreviated IPv6
8506 addresses are always used.
8507
8508 Ideally, it would be nice to tidy up this anomalous situation by changing to
8509 colons in all cases, given that quoting is now available for &(lsearch)&.
8510 However, this would be an incompatible change that might break some existing
8511 configurations.
8512
8513 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
8514 IPv6 address) is not the same as specifying just &%net-%& without a number. In
8515 the former case the key strings include the mask value, whereas in the latter
8516 case the IP address is used on its own.
8517
8518
8519
8520 .section "Host list patterns that match by host name" "SECThoslispatnam"
8521 .cindex "host" "lookup failures"
8522 .cindex "unknown host name"
8523 .cindex "host list" "matching host name"
8524 There are several types of pattern that require Exim to know the name of the
8525 remote host. These are either wildcard patterns or lookups by name. (If a
8526 complete hostname is given without any wildcarding, it is used to find an IP
8527 address to match against, as described in section &<<SECThoslispatip>>&
8528 above.)
8529
8530 If the remote host name is not already known when Exim encounters one of these
8531 patterns, it has to be found from the IP address.
8532 Although many sites on the Internet are conscientious about maintaining reverse
8533 DNS data for their hosts, there are also many that do not do this.
8534 Consequently, a name cannot always be found, and this may lead to unwanted
8535 effects. Take care when configuring host lists with wildcarded name patterns.
8536 Consider what will happen if a name cannot be found.
8537
8538 Because of the problems of determining host names from IP addresses, matching
8539 against host names is not as common as matching against IP addresses.
8540
8541 By default, in order to find a host name, Exim first does a reverse DNS lookup;
8542 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
8543 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
8544 are done can be changed by setting the &%host_lookup_order%& option. For
8545 security, once Exim has found one or more names, it looks up the IP addresses
8546 for these names and compares them with the IP address that it started with.
8547 Only those names whose IP addresses match are accepted. Any other names are
8548 discarded. If no names are left, Exim behaves as if the host name cannot be
8549 found. In the most common case there is only one name and one IP address.
8550
8551 There are some options that control what happens if a host name cannot be
8552 found. These are described in section &<<SECTbehipnot>>& below.
8553
8554 .cindex "host" "alias for"
8555 .cindex "alias for host"
8556 As a result of aliasing, hosts may have more than one name. When processing any
8557 of the following types of pattern, all the host's names are checked:
8558
8559 .ilist
8560 .cindex "asterisk" "in host list"
8561 If a pattern starts with &"*"& the remainder of the item must match the end of
8562 the host name. For example, &`*.b.c`& matches all hosts whose names end in
8563 &'.b.c'&. This special simple form is provided because this is a very common
8564 requirement. Other kinds of wildcarding require the use of a regular
8565 expression.
8566 .next
8567 .cindex "regular expressions" "in host list"
8568 .cindex "host list" "regular expression in"
8569 If the item starts with &"^"& it is taken to be a regular expression which is
8570 matched against the host name. Host names are case-independent, so this regular
8571 expression match is by default case-independent, but you can make it
8572 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
8573 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
8574 example,
8575 .code
8576 ^(a|b)\.c\.d$
8577 .endd
8578 is a regular expression that matches either of the two hosts &'a.c.d'& or
8579 &'b.c.d'&. When a regular expression is used in a host list, you must take care
8580 that backslash and dollar characters are not misinterpreted as part of the
8581 string expansion. The simplest way to do this is to use &`\N`& to mark that
8582 part of the string as non-expandable. For example:
8583 .code
8584 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
8585 .endd
8586 &*Warning*&: If you want to match a complete host name, you must include the
8587 &`$`& terminating metacharacter in the regular expression, as in the above
8588 example. Without it, a match at the start of the host name is all that is
8589 required.
8590 .endlist
8591
8592
8593
8594
8595 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
8596 .cindex "host" "lookup failures, permanent"
8597 While processing a host list, Exim may need to look up an IP address from a
8598 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
8599 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
8600 behaviour when it fails to find the information it is seeking is the same.
8601
8602 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
8603 apply to temporary DNS errors, whose handling is described in the next section.
8604
8605 .cindex "&`+include_unknown`&"
8606 .cindex "&`+ignore_unknown`&"
8607 Exim parses a host list from left to right. If it encounters a permanent
8608 lookup failure in any item in the host list before it has found a match,
8609 Exim treats it as a failure and the default behavior is as if the host
8610 does not match the list. This may not always be what you want to happen.
8611 To change Exim's behaviour, the special items &`+include_unknown`& or
8612 &`+ignore_unknown`& may appear in the list (at top level &-- they are
8613 not recognized in an indirected file).
8614
8615 .ilist
8616 If any item that follows &`+include_unknown`& requires information that
8617 cannot found, Exim behaves as if the host does match the list. For example,
8618 .code
8619 host_reject_connection = +include_unknown:*.enemy.ex
8620 .endd
8621 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
8622 any hosts whose name it cannot find.
8623
8624 .next
8625 If any item that follows &`+ignore_unknown`& requires information that cannot
8626 be found, Exim ignores that item and proceeds to the rest of the list. For
8627 example:
8628 .code
8629 accept hosts = +ignore_unknown : friend.example : \
8630 192.168.4.5
8631 .endd
8632 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
8633 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
8634 name can be found for 192.168.4.5, it is rejected.
8635 .endlist
8636
8637 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
8638 list. The effect of each one lasts until the next, or until the end of the
8639 list.
8640
8641 .section "Mixing wildcarded host names and addresses in host lists" &&&
8642 "SECTmixwilhos"
8643 .cindex "host list" "mixing names and addresses in"
8644
8645 This section explains the host/ip processing logic with the same concepts
8646 as the previous section, but specifically addresses what happens when a
8647 wildcarded hostname is one of the items in the hostlist.
8648
8649 .ilist
8650 If you have name lookups or wildcarded host names and
8651 IP addresses in the same host list, you should normally put the IP
8652 addresses first. For example, in an ACL you could have:
8653 .code
8654 accept hosts = 10.9.8.7 : *.friend.example
8655 .endd
8656 The reason you normally would order it this way lies in the
8657 left-to-right way that Exim processes lists. It can test IP addresses
8658 without doing any DNS lookups, but when it reaches an item that requires
8659 a host name, it fails if it cannot find a host name to compare with the
8660 pattern. If the above list is given in the opposite order, the
8661 &%accept%& statement fails for a host whose name cannot be found, even
8662 if its IP address is 10.9.8.7.
8663
8664 .next
8665 If you really do want to do the name check first, and still recognize the IP
8666 address, you can rewrite the ACL like this:
8667 .code
8668 accept hosts = *.friend.example
8669 accept hosts = 10.9.8.7
8670 .endd
8671 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
8672 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
8673 &`+ignore_unknown`&, which was discussed in depth in the first example in
8674 this section.
8675 .endlist
8676
8677
8678 .section "Temporary DNS errors when looking up host information" &&&
8679 "SECTtemdnserr"
8680 .cindex "host" "lookup failures, temporary"
8681 .cindex "&`+include_defer`&"
8682 .cindex "&`+ignore_defer`&"
8683 A temporary DNS lookup failure normally causes a defer action (except when
8684 &%dns_again_means_nonexist%& converts it into a permanent error). However,
8685 host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
8686 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
8687 section. These options should be used with care, probably only in non-critical
8688 host lists such as whitelists.
8689
8690
8691
8692 .section "Host list patterns for single-key lookups by host name" &&&
8693 "SECThoslispatnamsk"
8694 .cindex "unknown host name"
8695 .cindex "host list" "matching host name"
8696 If a pattern is of the form
8697 .display
8698 <&'single-key-search-type'&>;<&'search-data'&>
8699 .endd
8700 for example
8701 .code
8702 dbm;/host/accept/list
8703 .endd
8704 a single-key lookup is performed, using the host name as its key. If the
8705 lookup succeeds, the host matches the item. The actual data that is looked up
8706 is not used.
8707
8708 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
8709 keys in the file, not IP addresses. If you want to do lookups based on IP
8710 addresses, you must precede the search type with &"net-"& (see section
8711 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
8712 two items in the same list, one doing an address lookup and one doing a name
8713 lookup, both using the same file.
8714
8715
8716
8717 .section "Host list patterns for query-style lookups" "SECID81"
8718 If a pattern is of the form
8719 .display
8720 <&'query-style-search-type'&>;<&'query'&>
8721 .endd
8722 the query is obeyed, and if it succeeds, the host matches the item. The actual
8723 data that is looked up is not used. The variables &$sender_host_address$& and
8724 &$sender_host_name$& can be used in the query. For example:
8725 .code
8726 hosts_lookup = pgsql;\
8727 select ip from hostlist where ip='$sender_host_address'
8728 .endd
8729 The value of &$sender_host_address$& for an IPv6 address contains colons. You
8730 can use the &%sg%& expansion item to change this if you need to. If you want to
8731 use masked IP addresses in database queries, you can use the &%mask%& expansion
8732 operator.
8733
8734 If the query contains a reference to &$sender_host_name$&, Exim automatically
8735 looks up the host name if it has not already done so. (See section
8736 &<<SECThoslispatnam>>& for comments on finding host names.)
8737
8738 Historical note: prior to release 4.30, Exim would always attempt to find a
8739 host name before running the query, unless the search type was preceded by
8740 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
8741 still recognized for query-style lookups, but its presence or absence has no
8742 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
8743 See section &<<SECThoslispatsikey>>&.)
8744
8745
8746
8747
8748
8749 .section "Address lists" "SECTaddresslist"
8750 .cindex "list" "address list"
8751 .cindex "address list" "empty item"
8752 .cindex "address list" "patterns"
8753 Address lists contain patterns that are matched against mail addresses. There
8754 is one special case to be considered: the sender address of a bounce message is
8755 always empty. You can test for this by providing an empty item in an address
8756 list. For example, you can set up a router to process bounce messages by
8757 using this option setting:
8758 .code
8759 senders = :
8760 .endd
8761 The presence of the colon creates an empty item. If you do not provide any
8762 data, the list is empty and matches nothing. The empty sender can also be
8763 detected by a regular expression that matches an empty string,
8764 and by a query-style lookup that succeeds when &$sender_address$& is empty.
8765
8766 Non-empty items in an address list can be straightforward email addresses. For
8767 example:
8768 .code
8769 senders = jbc@askone.example : hs@anacreon.example
8770 .endd
8771 A certain amount of wildcarding is permitted. If a pattern contains an @
8772 character, but is not a regular expression and does not begin with a
8773 semicolon-terminated lookup type (described below), the local part of the
8774 subject address is compared with the local part of the pattern, which may start
8775 with an asterisk. If the local parts match, the domain is checked in exactly
8776 the same way as for a pattern in a domain list. For example, the domain can be
8777 wildcarded, refer to a named list, or be a lookup:
8778 .code
8779 deny senders = *@*.spamming.site:\
8780 *@+hostile_domains:\
8781 bozo@partial-lsearch;/list/of/dodgy/sites:\
8782 *@dbm;/bad/domains.db
8783 .endd
8784 .cindex "local part" "starting with !"
8785 .cindex "address list" "local part starting with !"
8786 If a local part that begins with an exclamation mark is required, it has to be
8787 specified using a regular expression, because otherwise the exclamation mark is
8788 treated as a sign of negation, as is standard in lists.
8789
8790 If a non-empty pattern that is not a regular expression or a lookup does not
8791 contain an @ character, it is matched against the domain part of the subject
8792 address. The only two formats that are recognized this way are a literal
8793 domain, or a domain pattern that starts with *. In both these cases, the effect
8794 is the same as if &`*@`& preceded the pattern. For example:
8795 .code
8796 deny senders = enemy.domain : *.enemy.domain
8797 .endd
8798
8799 The following kinds of more complicated address list pattern can match any
8800 address, including the empty address that is characteristic of bounce message
8801 senders:
8802
8803 .ilist
8804 .cindex "regular expressions" "in address list"
8805 .cindex "address list" "regular expression in"
8806 If (after expansion) a pattern starts with &"^"&, a regular expression match is
8807 done against the complete address, with the pattern as the regular expression.
8808 You must take care that backslash and dollar characters are not misinterpreted
8809 as part of the string expansion. The simplest way to do this is to use &`\N`&
8810 to mark that part of the string as non-expandable. For example:
8811 .code
8812 deny senders = \N^.*this.*@example\.com$\N : \
8813 \N^\d{8}.+@spamhaus.example$\N : ...
8814 .endd
8815 The &`\N`& sequences are removed by the expansion, so these items do indeed
8816 start with &"^"& by the time they are being interpreted as address patterns.
8817
8818 .next
8819 .cindex "address list" "lookup for complete address"
8820 Complete addresses can be looked up by using a pattern that starts with a
8821 lookup type terminated by a semicolon, followed by the data for the lookup. For
8822 example:
8823 .code
8824 deny senders = cdb;/etc/blocked.senders : \
8825 mysql;select address from blocked where \
8826 address='${quote_mysql:$sender_address}'
8827 .endd
8828 Both query-style and single-key lookup types can be used. For a single-key
8829 lookup type, Exim uses the complete address as the key. However, empty keys are
8830 not supported for single-key lookups, so a match against the empty address
8831 always fails. This restriction does not apply to query-style lookups.
8832
8833 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
8834 cannot be used, and is ignored if specified, with an entry being written to the
8835 panic log.
8836 .cindex "*@ with single-key lookup"
8837 However, you can configure lookup defaults, as described in section
8838 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
8839 default. For example, with this lookup:
8840 .code
8841 accept senders = lsearch*@;/some/file
8842 .endd
8843 the file could contains lines like this:
8844 .code
8845 user1@domain1.example
8846 *@domain2.example
8847 .endd
8848 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
8849 that are tried is:
8850 .code
8851 nimrod@jaeger.example
8852 *@jaeger.example
8853 *
8854 .endd
8855 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
8856 would mean that every address matches, thus rendering the test useless.
8857
8858 &*Warning 2*&: Do not confuse these two kinds of item:
8859 .code
8860 deny recipients = dbm*@;/some/file
8861 deny recipients = *@dbm;/some/file
8862 .endd
8863 The first does a whole address lookup, with defaulting, as just described,
8864 because it starts with a lookup type. The second matches the local part and
8865 domain independently, as described in a bullet point below.
8866 .endlist
8867
8868
8869 The following kinds of address list pattern can match only non-empty addresses.
8870 If the subject address is empty, a match against any of these pattern types
8871 always fails.
8872
8873
8874 .ilist
8875 .cindex "@@ with single-key lookup"
8876 .cindex "address list" "@@ lookup type"
8877 .cindex "address list" "split local part and domain"
8878 If a pattern starts with &"@@"& followed by a single-key lookup item
8879 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
8880 split into a local part and a domain. The domain is looked up in the file. If
8881 it is not found, there is no match. If it is found, the data that is looked up
8882 from the file is treated as a colon-separated list of local part patterns, each
8883 of which is matched against the subject local part in turn.
8884
8885 .cindex "asterisk" "in address list"
8886 The lookup may be a partial one, and/or one involving a search for a default
8887 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
8888 patterns that are looked up can be regular expressions or begin with &"*"&, or
8889 even be further lookups. They may also be independently negated. For example,
8890 with
8891 .code
8892 deny senders = @@dbm;/etc/reject-by-domain
8893 .endd
8894 the data from which the DBM file is built could contain lines like
8895 .code
8896 baddomain.com: !postmaster : *
8897 .endd
8898 to reject all senders except &%postmaster%& from that domain.
8899
8900 .cindex "local part" "starting with !"
8901 If a local part that actually begins with an exclamation mark is required, it
8902 has to be specified using a regular expression. In &(lsearch)& files, an entry
8903 may be split over several lines by indenting the second and subsequent lines,
8904 but the separating colon must still be included at line breaks. White space
8905 surrounding the colons is ignored. For example:
8906 .code
8907 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
8908 spammer3 : spammer4
8909 .endd
8910 As in all colon-separated lists in Exim, a colon can be included in an item by
8911 doubling.
8912
8913 If the last item in the list starts with a right angle-bracket, the remainder
8914 of the item is taken as a new key to look up in order to obtain a continuation
8915 list of local parts. The new key can be any sequence of characters. Thus one
8916 might have entries like
8917 .code
8918 aol.com: spammer1 : spammer 2 : >*
8919 xyz.com: spammer3 : >*
8920 *: ^\d{8}$
8921 .endd
8922 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
8923 local parts for all domains, in addition to the specific local parts listed for
8924 each domain. Of course, using this feature costs another lookup each time a
8925 chain is followed, but the effort needed to maintain the data is reduced.
8926
8927 .cindex "loop" "in lookups"
8928 It is possible to construct loops using this facility, and in order to catch
8929 them, the chains may be no more than fifty items long.
8930
8931 .next
8932 The @@<&'lookup'&> style of item can also be used with a query-style
8933 lookup, but in this case, the chaining facility is not available. The lookup
8934 can only return a single list of local parts.
8935 .endlist
8936
8937 &*Warning*&: There is an important difference between the address list items
8938 in these two examples:
8939 .code
8940 senders = +my_list
8941 senders = *@+my_list
8942 .endd
8943 In the first one, &`my_list`& is a named address list, whereas in the second
8944 example it is a named domain list.
8945
8946
8947
8948
8949 .section "Case of letters in address lists" "SECTcasletadd"
8950 .cindex "case of local parts"
8951 .cindex "address list" "case forcing"
8952 .cindex "case forcing in address lists"
8953 Domains in email addresses are always handled caselessly, but for local parts
8954 case may be significant on some systems (see &%caseful_local_part%& for how
8955 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
8956 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
8957 blocking lists should be done in a case-independent manner. Since most address
8958 lists in Exim are used for this kind of control, Exim attempts to do this by
8959 default.
8960
8961 The domain portion of an address is always lowercased before matching it to an
8962 address list. The local part is lowercased by default, and any string
8963 comparisons that take place are done caselessly. This means that the data in
8964 the address list itself, in files included as plain file names, and in any file
8965 that is looked up using the &"@@"& mechanism, can be in any case. However, the
8966 keys in files that are looked up by a search type other than &(lsearch)& (which
8967 works caselessly) must be in lower case, because these lookups are not
8968 case-independent.
8969
8970 .cindex "&`+caseful`&"
8971 To allow for the possibility of caseful address list matching, if an item in
8972 an address list is the string &"+caseful"&, the original case of the local
8973 part is restored for any comparisons that follow, and string comparisons are no
8974 longer case-independent. This does not affect the domain, which remains in
8975 lower case. However, although independent matches on the domain alone are still
8976 performed caselessly, regular expressions that match against an entire address
8977 become case-sensitive after &"+caseful"& has been seen.
8978
8979
8980
8981 .section "Local part lists" "SECTlocparlis"
8982 .cindex "list" "local part list"
8983 .cindex "local part" "list"
8984 Case-sensitivity in local part lists is handled in the same way as for address
8985 lists, as just described. The &"+caseful"& item can be used if required. In a
8986 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
8987 set false, the subject is lowercased and the matching is initially
8988 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
8989 matching in the local part list, but not elsewhere in the router. If
8990 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
8991 option is case-sensitive from the start.
8992
8993 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
8994 comments are handled in the same way as address lists &-- they are recognized
8995 only if the # is preceded by white space or the start of the line.
8996 Otherwise, local part lists are matched in the same way as domain lists, except
8997 that the special items that refer to the local host (&`@`&, &`@[]`&,
8998 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
8999 Refer to section &<<SECTdomainlist>>& for details of the other available item
9000 types.
9001 .ecindex IIDdohoadli
9002
9003
9004
9005
9006 . ////////////////////////////////////////////////////////////////////////////
9007 . ////////////////////////////////////////////////////////////////////////////
9008
9009 .chapter "String expansions" "CHAPexpand"
9010 .scindex IIDstrexp "expansion" "of strings"
9011 Many strings in Exim's run time configuration are expanded before use. Some of
9012 them are expanded every time they are used; others are expanded only once.
9013
9014 When a string is being expanded it is copied verbatim from left to right except
9015 when a dollar or backslash character is encountered. A dollar specifies the
9016 start of a portion of the string that is interpreted and replaced as described
9017 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
9018 escape character, as described in the following section.
9019
9020 Whether a string is expanded depends upon the context. Usually this is solely
9021 dependent upon the option for which a value is sought; in this documentation,
9022 options for which string expansion is performed are marked with &dagger; after
9023 the data type. ACL rules always expand strings. A couple of expansion
9024 conditions do not expand some of the brace-delimited branches, for security
9025 reasons.
9026
9027
9028
9029 .section "Literal text in expanded strings" "SECTlittext"
9030 .cindex "expansion" "including literal text"
9031 An uninterpreted dollar can be included in an expanded string by putting a
9032 backslash in front of it. A backslash can be used to prevent any special
9033 character being treated specially in an expansion, including backslash itself.
9034 If the string appears in quotes in the configuration file, two backslashes are
9035 required because the quotes themselves cause interpretation of backslashes when
9036 the string is read in (see section &<<SECTstrings>>&).
9037
9038 .cindex "expansion" "non-expandable substrings"
9039 A portion of the string can specified as non-expandable by placing it between
9040 two occurrences of &`\N`&. This is particularly useful for protecting regular
9041 expressions, which often contain backslashes and dollar signs. For example:
9042 .code
9043 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
9044 .endd
9045 On encountering the first &`\N`&, the expander copies subsequent characters
9046 without interpretation until it reaches the next &`\N`& or the end of the
9047 string.
9048
9049
9050
9051 .section "Character escape sequences in expanded strings" "SECID82"
9052 .cindex "expansion" "escape sequences"
9053 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
9054 expanded string is recognized as an escape sequence for the character newline,
9055 carriage return, or tab, respectively. A backslash followed by up to three
9056 octal digits is recognized as an octal encoding for a single character, and a
9057 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
9058 encoding.
9059
9060 These escape sequences are also recognized in quoted strings when they are read
9061 in. Their interpretation in expansions as well is useful for unquoted strings,
9062 and for other cases such as looked-up strings that are then expanded.
9063
9064
9065 .section "Testing string expansions" "SECID83"
9066 .cindex "expansion" "testing"
9067 .cindex "testing" "string expansion"
9068 .oindex "&%-be%&"
9069 Many expansions can be tested by calling Exim with the &%-be%& option. This
9070 takes the command arguments, or lines from the standard input if there are no
9071 arguments, runs them through the string expansion code, and writes the results
9072 to the standard output. Variables based on configuration values are set up, but
9073 since no message is being processed, variables such as &$local_part$& have no
9074 value. Nevertheless the &%-be%& option can be useful for checking out file and
9075 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
9076 and &%nhash%&.
9077
9078 Exim gives up its root privilege when it is called with the &%-be%& option, and
9079 instead runs under the uid and gid it was called with, to prevent users from
9080 using &%-be%& for reading files to which they do not have access.
9081
9082 .oindex "&%-bem%&"
9083 If you want to test expansions that include variables whose values are taken
9084 from a message, there are two other options that can be used. The &%-bem%&
9085 option is like &%-be%& except that it is followed by a file name. The file is
9086 read as a message before doing the test expansions. For example:
9087 .code
9088 exim -bem /tmp/test.message '$h_subject:'
9089 .endd
9090 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
9091 Exim message identifier. For example:
9092 .code
9093 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
9094 .endd
9095 This loads the message from Exim's spool before doing the test expansions, and
9096 is therefore restricted to admin users.
9097
9098
9099 .section "Forced expansion failure" "SECTforexpfai"
9100 .cindex "expansion" "forced failure"
9101 A number of expansions that are described in the following section have
9102 alternative &"true"& and &"false"& substrings, enclosed in brace characters
9103 (which are sometimes called &"curly brackets"&). Which of the two strings is
9104 used depends on some condition that is evaluated as part of the expansion. If,
9105 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
9106 the entire string expansion fails in a way that can be detected by the code
9107 that requested the expansion. This is called &"forced expansion failure"&, and
9108 its consequences depend on the circumstances. In some cases it is no different
9109 from any other expansion failure, but in others a different action may be
9110 taken. Such variations are mentioned in the documentation of the option that is
9111 being expanded.
9112
9113
9114
9115
9116 .section "Expansion items" "SECTexpansionitems"
9117 The following items are recognized in expanded strings. White space may be used
9118 between sub-items that are keywords or substrings enclosed in braces inside an
9119 outer set of braces, to improve readability. &*Warning*&: Within braces,
9120 white space is significant.
9121
9122 .vlist
9123 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
9124 .cindex "expansion" "variables"
9125 Substitute the contents of the named variable, for example:
9126 .code
9127 $local_part
9128 ${domain}
9129 .endd
9130 The second form can be used to separate the name from subsequent alphanumeric
9131 characters. This form (using braces) is available only for variables; it does
9132 &'not'& apply to message headers. The names of the variables are given in
9133 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
9134 given, the expansion fails.
9135
9136 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
9137 .cindex "expansion" "operators"
9138 The string is first itself expanded, and then the operation specified by
9139 <&'op'&> is applied to it. For example:
9140 .code
9141 ${lc:$local_part}
9142 .endd
9143 The string starts with the first character after the colon, which may be
9144 leading white space. A list of operators is given in section &<<SECTexpop>>&
9145 below. The operator notation is used for simple expansion items that have just
9146 one argument, because it reduces the number of braces and therefore makes the
9147 string easier to understand.
9148
9149 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
9150 This item inserts &"basic"& header lines. It is described with the &%header%&
9151 expansion item below.
9152
9153
9154 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
9155 .cindex "expansion" "calling an acl"
9156 .cindex "&%acl%&" "call from expansion"
9157 The name and zero to nine argument strings are first expanded separately. The expanded
9158 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
9159 Any unused are made empty. The variable &$acl_narg$& is set to the number of
9160 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
9161 and may use the variables; if another acl expansion is used the values
9162 are restored after it returns. If the ACL sets
9163 a value using a "message =" modifier and returns accept or deny, the value becomes
9164 the result of the expansion.
9165 If no message is set and the ACL returns accept or deny
9166 the expansion result is an empty string.
9167 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
9168
9169
9170 .vitem "&*${authresults{*&<&'authserv-id'&>&*}}*&"
9171 .cindex authentication "results header"
9172 .cindex headers "authentication-results:"
9173 .cindex authentication "expansion item"
9174 This item returns a string suitable for insertion as an
9175 &'Authentication-Results"'&
9176 header line.
9177 The given <&'authserv-id'&> is included in the result; typically this
9178 will be a domain name identifying the system performing the authentications.
9179 Methods that might be present in the result include:
9180 .code
9181 none
9182 iprev
9183 auth
9184 spf
9185 dkim
9186 .endd
9187
9188 Example use (as an ACL modifier):
9189 .code
9190 add_header = :at_start:${authresults {$primary_hostname}}
9191 .endd
9192 This is safe even if no authentication results are available.
9193
9194
9195 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
9196 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9197 .cindex "expansion" "extracting certificate fields"
9198 .cindex "&%certextract%&" "certificate fields"
9199 .cindex "certificate" "extracting fields"
9200 The <&'certificate'&> must be a variable of type certificate.
9201 The field name is expanded and used to retrieve the relevant field from
9202 the certificate. Supported fields are:
9203 .display
9204 &`version `&
9205 &`serial_number `&
9206 &`subject `& RFC4514 DN
9207 &`issuer `& RFC4514 DN
9208 &`notbefore `& time
9209 &`notafter `& time
9210 &`sig_algorithm `&
9211 &`signature `&
9212 &`subj_altname `& tagged list
9213 &`ocsp_uri `& list
9214 &`crl_uri `& list
9215 .endd
9216 If the field is found,
9217 <&'string2'&> is expanded, and replaces the whole item;
9218 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9219 variable &$value$& contains the value that has been extracted. Afterwards, it
9220 is restored to any previous value it might have had.
9221
9222 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9223 key is not found. If {<&'string2'&>} is also omitted, the value that was
9224 extracted is used.
9225
9226 Some field names take optional modifiers, appended and separated by commas.
9227
9228 The field selectors marked as "RFC4514" above
9229 output a Distinguished Name string which is
9230 not quite
9231 parseable by Exim as a comma-separated tagged list
9232 (the exceptions being elements containing commas).
9233 RDN elements of a single type may be selected by
9234 a modifier of the type label; if so the expansion
9235 result is a list (newline-separated by default).
9236 The separator may be changed by another modifier of
9237 a right angle-bracket followed immediately by the new separator.
9238 Recognised RDN type labels include "CN", "O", "OU" and "DC".
9239
9240 The field selectors marked as "time" above
9241 take an optional modifier of "int"
9242 for which the result is the number of seconds since epoch.
9243 Otherwise the result is a human-readable string
9244 in the timezone selected by the main "timezone" option.
9245
9246 The field selectors marked as "list" above return a list,
9247 newline-separated by default,
9248 (embedded separator characters in elements are doubled).
9249 The separator may be changed by a modifier of
9250 a right angle-bracket followed immediately by the new separator.
9251
9252 The field selectors marked as "tagged" above
9253 prefix each list element with a type string and an equals sign.
9254 Elements of only one type may be selected by a modifier
9255 which is one of "dns", "uri" or "mail";
9256 if so the element tags are omitted.
9257
9258 If not otherwise noted field values are presented in human-readable form.
9259
9260 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
9261 {*&<&'arg'&>&*}...}*&"
9262 .cindex &%dlfunc%&
9263 This expansion dynamically loads and then calls a locally-written C function.
9264 This functionality is available only if Exim is compiled with
9265 .code
9266 EXPAND_DLFUNC=yes
9267 .endd
9268 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
9269 object so that it doesn't reload the same object file in the same Exim process
9270 (but of course Exim does start new processes frequently).
9271
9272 There may be from zero to eight arguments to the function. When compiling
9273 a local function that is to be called in this way, &_local_scan.h_& should be
9274 included. The Exim variables and functions that are defined by that API
9275 are also available for dynamically loaded functions. The function itself
9276 must have the following type:
9277 .code
9278 int dlfunction(uschar **yield, int argc, uschar *argv[])
9279 .endd
9280 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
9281 function should return one of the following values:
9282
9283 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
9284 into the expanded string that is being built.
9285
9286 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
9287 from &'yield'&, if it is set.
9288
9289 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
9290 taken from &'yield'& if it is set.
9291
9292 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
9293
9294 When compiling a function that is to be used in this way with gcc,
9295 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
9296 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
9297
9298
9299 .vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
9300 .cindex "expansion" "extracting value from environment"
9301 .cindex "environment" "values from"
9302 The key is first expanded separately, and leading and trailing white space
9303 removed.
9304 This is then searched for as a name in the environment.
9305 If a variable is found then its value is placed in &$value$&
9306 and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
9307
9308 Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
9309 appear, for example:
9310 .code
9311 ${env{USER}{$value} fail }
9312 .endd
9313 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9314 {<&'string1'&>} must be present for &"fail"& to be recognized.
9315
9316 If {<&'string2'&>} is omitted an empty string is substituted on
9317 search failure.
9318 If {<&'string1'&>} is omitted the search result is substituted on
9319 search success.
9320
9321 The environment is adjusted by the &%keep_environment%& and
9322 &%add_environment%& main section options.
9323
9324
9325 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9326 {*&<&'string3'&>&*}}*&"
9327 .cindex "expansion" "extracting substrings by key"
9328 .cindex "&%extract%&" "substrings by key"
9329 The key and <&'string1'&> are first expanded separately. Leading and trailing
9330 white space is removed from the key (but not from any of the strings). The key
9331 must not be empty and must not consist entirely of digits.
9332 The expanded <&'string1'&> must be of the form:
9333 .display
9334 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9335 .endd
9336 .vindex "&$value$&"
9337 where the equals signs and spaces (but not both) are optional. If any of the
9338 values contain white space, they must be enclosed in double quotes, and any
9339 values that are enclosed in double quotes are subject to escape processing as
9340 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9341 for the value that corresponds to the key. The search is case-insensitive. If
9342 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9343 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9344 variable &$value$& contains the value that has been extracted. Afterwards, it
9345 is restored to any previous value it might have had.
9346
9347 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9348 key is not found. If {<&'string2'&>} is also omitted, the value that was
9349 extracted is used. Thus, for example, these two expansions are identical, and
9350 yield &"2001"&:
9351 .code
9352 ${extract{gid}{uid=1984 gid=2001}}
9353 ${extract{gid}{uid=1984 gid=2001}{$value}}
9354 .endd
9355 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9356 appear, for example:
9357 .code
9358 ${extract{Z}{A=... B=...}{$value} fail }
9359 .endd
9360 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9361 {<&'string2'&>} must be present for &"fail"& to be recognized.
9362
9363
9364 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
9365 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9366 .cindex "expansion" "extracting substrings by number"
9367 .cindex "&%extract%&" "substrings by number"
9368 The <&'number'&> argument must consist entirely of decimal digits,
9369 apart from leading and trailing white space, which is ignored.
9370 This is what distinguishes this form of &%extract%& from the previous kind. It
9371 behaves in the same way, except that, instead of extracting a named field, it
9372 extracts from <&'string1'&> the field whose number is given as the first
9373 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
9374 <&'string3'&> as before.
9375
9376 The fields in the string are separated by any one of the characters in the
9377 separator string. These may include space or tab characters.
9378 The first field is numbered one. If the number is negative, the fields are
9379 counted from the end of the string, with the rightmost one numbered -1. If the
9380 number given is zero, the entire string is returned. If the modulus of the
9381 number is greater than the number of fields in the string, the result is the
9382 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
9383 provided. For example:
9384 .code
9385 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
9386 .endd
9387 yields &"42"&, and
9388 .code
9389 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
9390 .endd
9391 yields &"99"&. Two successive separators mean that the field between them is
9392 empty (for example, the fifth field above).
9393
9394
9395 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
9396 .cindex "list" "selecting by condition"
9397 .cindex "expansion" "selecting from list by condition"
9398 .vindex "&$item$&"
9399 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9400 default, but the separator can be changed in the usual way. For each item
9401 in this list, its value is place in &$item$&, and then the condition is
9402 evaluated. If the condition is true, &$item$& is added to the output as an
9403 item in a new list; if the condition is false, the item is discarded. The
9404 separator used for the output list is the same as the one used for the
9405 input, but a separator setting is not included in the output. For example:
9406 .code
9407 ${filter{a:b:c}{!eq{$item}{b}}}
9408 .endd
9409 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
9410 to what it was before. See also the &*map*& and &*reduce*& expansion items.
9411
9412
9413 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9414 .cindex "hash function" "textual"
9415 .cindex "expansion" "textual hash"
9416 This is a textual hashing function, and was the first to be implemented in
9417 early versions of Exim. In current releases, there are other hashing functions
9418 (numeric, MD5, and SHA-1), which are described below.
9419
9420 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
9421 <&'n'&>. If you are using fixed values for these numbers, that is, if
9422 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
9423 use the simpler operator notation that avoids some of the braces:
9424 .code
9425 ${hash_<n>_<m>:<string>}
9426 .endd
9427 The second number is optional (in both notations). If <&'n'&> is greater than
9428 or equal to the length of the string, the expansion item returns the string.
9429 Otherwise it computes a new string of length <&'n'&> by applying a hashing
9430 function to the string. The new string consists of characters taken from the
9431 first <&'m'&> characters of the string
9432 .code
9433 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
9434 .endd
9435 If <&'m'&> is not present the value 26 is used, so that only lower case
9436 letters appear. For example:
9437 .display
9438 &`$hash{3}{monty}} `& yields &`jmg`&
9439 &`$hash{5}{monty}} `& yields &`monty`&
9440 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
9441 .endd
9442
9443 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
9444 &*$h_*&<&'header&~name'&>&*:*&" &&&
9445 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9446 &*$bh_*&<&'header&~name'&>&*:*&" &&&
9447 "&*$lheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9448 &*$lh_*&<&'header&~name'&>&*:*&"
9449 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9450 &*$rh_*&<&'header&~name'&>&*:*&"
9451 .cindex "expansion" "header insertion"
9452 .vindex "&$header_$&"
9453 .vindex "&$bheader_$&"
9454 .vindex "&$lheader_$&"
9455 .vindex "&$rheader_$&"
9456 .cindex "header lines" "in expansion strings"
9457 .cindex "header lines" "character sets"
9458 .cindex "header lines" "decoding"
9459 Substitute the contents of the named message header line, for example
9460 .code
9461 $header_reply-to:
9462 .endd
9463 The newline that terminates a header line is not included in the expansion, but
9464 internal newlines (caused by splitting the header line over several physical
9465 lines) may be present.
9466
9467 The difference between the four pairs of expansions is in the way
9468 the data in the header line is interpreted.
9469
9470 .ilist
9471 .cindex "white space" "in header lines"
9472 &%rheader%& gives the original &"raw"& content of the header line, with no
9473 processing at all, and without the removal of leading and trailing white space.
9474
9475 .next
9476 .cindex "list" "of header lines"
9477 &%lheader%& gives a colon-separated list, one element per header when there
9478 are multiple headers with a given name.
9479 Any embedded colon characters within an element are doubled, so normal Exim
9480 list-processing facilities can be used.
9481 The terminating newline of each element is removed; in other respects
9482 the content is &"raw"&.
9483
9484 .next
9485 .cindex "base64 encoding" "in header lines"
9486 &%bheader%& removes leading and trailing white space, and then decodes base64
9487 or quoted-printable MIME &"words"& within the header text, but does no
9488 character set translation. If decoding of what looks superficially like a MIME
9489 &"word"& fails, the raw string is returned. If decoding
9490 .cindex "binary zero" "in header line"
9491 produces a binary zero character, it is replaced by a question mark &-- this is
9492 what Exim does for binary zeros that are actually received in header lines.
9493
9494 .next
9495 &%header%& tries to translate the string as decoded by &%bheader%& to a
9496 standard character set. This is an attempt to produce the same string as would
9497 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
9498 returned. Translation is attempted only on operating systems that support the
9499 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
9500 a system Makefile or in &_Local/Makefile_&.
9501 .endlist ilist
9502
9503 In a filter file, the target character set for &%header%& can be specified by a
9504 command of the following form:
9505 .code
9506 headers charset "UTF-8"
9507 .endd
9508 This command affects all references to &$h_$& (or &$header_$&) expansions in
9509 subsequently obeyed filter commands. In the absence of this command, the target
9510 character set in a filter is taken from the setting of the &%headers_charset%&
9511 option in the runtime configuration. The value of this option defaults to the
9512 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
9513 ISO-8859-1.
9514
9515 Header names follow the syntax of RFC 2822, which states that they may contain
9516 any printing characters except space and colon. Consequently, curly brackets
9517 &'do not'& terminate header names, and should not be used to enclose them as
9518 if they were variables. Attempting to do so causes a syntax error.
9519
9520 Only header lines that are common to all copies of a message are visible to
9521 this mechanism. These are the original header lines that are received with the
9522 message, and any that are added by an ACL statement or by a system
9523 filter. Header lines that are added to a particular copy of a message by a
9524 router or transport are not accessible.
9525
9526 For incoming SMTP messages, no header lines are visible in
9527 ACLs that are obeyed before the data phase completes,
9528 because the header structure is not set up until the message is received.
9529 They are visible in DKIM, PRDR and DATA ACLs.
9530 Header lines that are added in a RCPT ACL (for example)
9531 are saved until the message's incoming header lines are available, at which
9532 point they are added.
9533 When any of the above ACLs ar
9534 running, however, header lines added by earlier ACLs are visible.
9535
9536 Upper case and lower case letters are synonymous in header names. If the
9537 following character is white space, the terminating colon may be omitted, but
9538 this is not recommended, because you may then forget it when it is needed. When
9539 white space terminates the header name, this white space is included in the
9540 expanded string. If the message does not contain the given header, the
9541 expansion item is replaced by an empty string. (See the &%def%& condition in
9542 section &<<SECTexpcond>>& for a means of testing for the existence of a
9543 header.)
9544
9545 If there is more than one header with the same name, they are all concatenated
9546 to form the substitution string, up to a maximum length of 64K. Unless
9547 &%rheader%& is being used, leading and trailing white space is removed from
9548 each header before concatenation, and a completely empty header is ignored. A
9549 newline character is then inserted between non-empty headers, but there is no
9550 newline at the very end. For the &%header%& and &%bheader%& expansion, for
9551 those headers that contain lists of addresses, a comma is also inserted at the
9552 junctions between headers. This does not happen for the &%rheader%& expansion.
9553
9554
9555 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
9556 .cindex "expansion" "hmac hashing"
9557 .cindex &%hmac%&
9558 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
9559 shared secret and some text into a message authentication code, as specified in
9560 RFC 2104. This differs from &`${md5:secret_text...}`& or
9561 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
9562 cryptographic hash, allowing for authentication that is not possible with MD5
9563 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
9564 present. For example:
9565 .code
9566 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
9567 .endd
9568 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
9569 produces:
9570 .code
9571 dd97e3ba5d1a61b5006108f8c8252953
9572 .endd
9573 As an example of how this might be used, you might put in the main part of
9574 an Exim configuration:
9575 .code
9576 SPAMSCAN_SECRET=cohgheeLei2thahw
9577 .endd
9578 In a router or a transport you could then have:
9579 .code
9580 headers_add = \
9581 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
9582 ${hmac{md5}{SPAMSCAN_SECRET}\
9583 {${primary_hostname},${message_exim_id},$h_message-id:}}
9584 .endd
9585 Then given a message, you can check where it was scanned by looking at the
9586 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
9587 this header line is authentic by recomputing the authentication code from the
9588 host name, message ID and the &'Message-id:'& header line. This can be done
9589 using Exim's &%-be%& option, or by other means, for example by using the
9590 &'hmac_md5_hex()'& function in Perl.
9591
9592
9593 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9594 .cindex "expansion" "conditional"
9595 .cindex "&%if%&, expansion item"
9596 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
9597 item; otherwise <&'string2'&> is used. The available conditions are described
9598 in section &<<SECTexpcond>>& below. For example:
9599 .code
9600 ${if eq {$local_part}{postmaster} {yes}{no} }
9601 .endd
9602 The second string need not be present; if it is not and the condition is not
9603 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
9604 be present instead of the second string (without any curly brackets). In this
9605 case, the expansion is forced to fail if the condition is not true (see section
9606 &<<SECTforexpfai>>&).
9607
9608 If both strings are omitted, the result is the string &`true`& if the condition
9609 is true, and the empty string if the condition is false. This makes it less
9610 cumbersome to write custom ACL and router conditions. For example, instead of
9611 .code
9612 condition = ${if >{$acl_m4}{3}{true}{false}}
9613 .endd
9614 you can use
9615 .code
9616 condition = ${if >{$acl_m4}{3}}
9617 .endd
9618
9619
9620
9621 .vitem &*${imapfolder{*&<&'foldername'&>&*}}*&
9622 .cindex expansion "imap folder"
9623 .cindex "&%imapfolder%& expansion item"
9624 This item converts a (possibly multilevel, or with non-ASCII characters)
9625 folder specification to a Maildir name for filesystem use.
9626 For information on internationalisation support see &<<SECTi18nMDA>>&.
9627
9628
9629
9630 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9631 .cindex "expansion" "string truncation"
9632 .cindex "&%length%& expansion item"
9633 The &%length%& item is used to extract the initial portion of a string. Both
9634 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
9635 you are using a fixed value for the number, that is, if <&'string1'&> does not
9636 change when expanded, you can use the simpler operator notation that avoids
9637 some of the braces:
9638 .code
9639 ${length_<n>:<string>}
9640 .endd
9641 The result of this item is either the first <&'n'&> bytes or the whole
9642 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
9643 &%strlen%&, which gives the length of a string.
9644 All measurement is done in bytes and is not UTF-8 aware.
9645
9646
9647 .vitem "&*${listextract{*&<&'number'&>&*}&&&
9648 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9649 .cindex "expansion" "extracting list elements by number"
9650 .cindex "&%listextract%&" "extract list elements by number"
9651 .cindex "list" "extracting elements by number"
9652 The <&'number'&> argument must consist entirely of decimal digits,
9653 apart from an optional leading minus,
9654 and leading and trailing white space (which is ignored).
9655
9656 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9657 default, but the separator can be changed in the usual way.
9658
9659 The first field of the list is numbered one.
9660 If the number is negative, the fields are
9661 counted from the end of the list, with the rightmost one numbered -1.
9662 The numbered element of the list is extracted and placed in &$value$&,
9663 then <&'string2'&> is expanded as the result.
9664
9665 If the modulus of the
9666 number is zero or greater than the number of fields in the string,
9667 the result is the expansion of <&'string3'&>.
9668
9669 For example:
9670 .code
9671 ${listextract{2}{x:42:99}}
9672 .endd
9673 yields &"42"&, and
9674 .code
9675 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
9676 .endd
9677 yields &"result: 42"&.
9678
9679 If {<&'string3'&>} is omitted, an empty string is used for string3.
9680 If {<&'string2'&>} is also omitted, the value that was
9681 extracted is used.
9682 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
9683
9684
9685 .vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
9686 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9687 This is the first of one of two different types of lookup item, which are both
9688 described in the next item.
9689
9690 .vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
9691 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9692 .cindex "expansion" "lookup in"
9693 .cindex "file" "lookups"
9694 .cindex "lookup" "in expanded string"
9695 The two forms of lookup item specify data lookups in files and databases, as
9696 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
9697 lookups, and the second is used for query-style lookups. The <&'key'&>,
9698 <&'file'&>, and <&'query'&> strings are expanded before use.
9699
9700 If there is any white space in a lookup item which is part of a filter command,
9701 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
9702 other place where white space is significant, the lookup item must be enclosed
9703 in double quotes. The use of data lookups in users' filter files may be locked
9704 out by the system administrator.
9705
9706 .vindex "&$value$&"
9707 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
9708 During its expansion, the variable &$value$& contains the data returned by the
9709 lookup. Afterwards it reverts to the value it had previously (at the outer
9710 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
9711 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
9712 string on failure. If <&'string2'&> is provided, it can itself be a nested
9713 lookup, thus providing a mechanism for looking up a default value when the
9714 original lookup fails.
9715
9716 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
9717 data for the outer lookup while the parameters of the second lookup are
9718 expanded, and also while <&'string2'&> of the second lookup is expanded, should
9719 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
9720 appear, and in this case, if the lookup fails, the entire expansion is forced
9721 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
9722 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
9723 successful lookup, and nothing in the case of failure.
9724
9725 For single-key lookups, the string &"partial"& is permitted to precede the
9726 search type in order to do partial matching, and * or *@ may follow a search
9727 type to request default lookups if the key does not match (see sections
9728 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
9729
9730 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
9731 If a partial search is used, the variables &$1$& and &$2$& contain the wild
9732 and non-wild parts of the key during the expansion of the replacement text.
9733 They return to their previous values at the end of the lookup item.
9734
9735 This example looks up the postmaster alias in the conventional alias file:
9736 .code
9737 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
9738 .endd
9739 This example uses NIS+ to look up the full name of the user corresponding to
9740 the local part of an address, forcing the expansion to fail if it is not found:
9741 .code
9742 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
9743 {$value}fail}
9744 .endd
9745
9746
9747 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9748 .cindex "expansion" "list creation"
9749 .vindex "&$item$&"
9750 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9751 default, but the separator can be changed in the usual way. For each item
9752 in this list, its value is place in &$item$&, and then <&'string2'&> is
9753 expanded and added to the output as an item in a new list. The separator used
9754 for the output list is the same as the one used for the input, but a separator
9755 setting is not included in the output. For example:
9756 .code
9757 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
9758 .endd
9759 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
9760 value of &$item$& is restored to what it was before. See also the &*filter*&
9761 and &*reduce*& expansion items.
9762
9763 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9764 .cindex "expansion" "numeric hash"
9765 .cindex "hash function" "numeric"
9766 The three strings are expanded; the first two must yield numbers. Call them
9767 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9768 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9769 can use the simpler operator notation that avoids some of the braces:
9770 .code
9771 ${nhash_<n>_<m>:<string>}
9772 .endd
9773 The second number is optional (in both notations). If there is only one number,
9774 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
9775 processed by a div/mod hash function that returns two numbers, separated by a
9776 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
9777 example,
9778 .code
9779 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
9780 .endd
9781 returns the string &"6/33"&.
9782
9783
9784
9785 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
9786 .cindex "Perl" "use in expanded string"
9787 .cindex "expansion" "calling Perl from"
9788 This item is available only if Exim has been built to include an embedded Perl
9789 interpreter. The subroutine name and the arguments are first separately
9790 expanded, and then the Perl subroutine is called with those arguments. No
9791 additional arguments need be given; the maximum number permitted, including the
9792 name of the subroutine, is nine.
9793
9794 The return value of the subroutine is inserted into the expanded string, unless
9795 the return value is &%undef%&. In that case, the expansion fails in the same
9796 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
9797 Whatever you return is evaluated in a scalar context. For example, if you
9798 return the name of a Perl vector, the return value is the size of the vector,
9799 not its contents.
9800
9801 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
9802 with the error message that was passed to &%die%&. More details of the embedded
9803 Perl facility are given in chapter &<<CHAPperl>>&.
9804
9805 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
9806 out the use of this expansion item in filter files.
9807
9808
9809 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
9810 .cindex "&%prvs%& expansion item"
9811 The first argument is a complete email address and the second is secret
9812 keystring. The third argument, specifying a key number, is optional. If absent,
9813 it defaults to 0. The result of the expansion is a prvs-signed email address,
9814 to be typically used with the &%return_path%& option on an &(smtp)& transport
9815 as part of a bounce address tag validation (BATV) scheme. For more discussion
9816 and an example, see section &<<SECTverifyPRVS>>&.
9817
9818 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
9819 {*&<&'string'&>&*}}*&"
9820 .cindex "&%prvscheck%& expansion item"
9821 This expansion item is the complement of the &%prvs%& item. It is used for
9822 checking prvs-signed addresses. If the expansion of the first argument does not
9823 yield a syntactically valid prvs-signed address, the whole item expands to the
9824 empty string. When the first argument does expand to a syntactically valid
9825 prvs-signed address, the second argument is expanded, with the prvs-decoded
9826 version of the address and the key number extracted from the address in the
9827 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
9828
9829 These two variables can be used in the expansion of the second argument to
9830 retrieve the secret. The validity of the prvs-signed address is then checked
9831 against the secret. The result is stored in the variable &$prvscheck_result$&,
9832 which is empty for failure or &"1"& for success.
9833
9834 The third argument is optional; if it is missing, it defaults to an empty
9835 string. This argument is now expanded. If the result is an empty string, the
9836 result of the expansion is the decoded version of the address. This is the case
9837 whether or not the signature was valid. Otherwise, the result of the expansion
9838 is the expansion of the third argument.
9839
9840 All three variables can be used in the expansion of the third argument.
9841 However, once the expansion is complete, only &$prvscheck_result$& remains set.
9842 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
9843
9844 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
9845 .cindex "expansion" "inserting an entire file"
9846 .cindex "file" "inserting into expansion"
9847 .cindex "&%readfile%& expansion item"
9848 The file name and end-of-line string are first expanded separately. The file is
9849 then read, and its contents replace the entire item. All newline characters in
9850 the file are replaced by the end-of-line string if it is present. Otherwise,
9851 newlines are left in the string.
9852 String expansion is not applied to the contents of the file. If you want this,
9853 you must wrap the item in an &%expand%& operator. If the file cannot be read,
9854 the string expansion fails.
9855
9856 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
9857 locks out the use of this expansion item in filter files.
9858
9859
9860
9861 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
9862 {*&<&'options'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
9863 .cindex "expansion" "inserting from a socket"
9864 .cindex "socket, use of in expansion"
9865 .cindex "&%readsocket%& expansion item"
9866 This item inserts data from a Unix domain or TCP socket into the expanded
9867 string. The minimal way of using it uses just two arguments, as in these
9868 examples:
9869 .code
9870 ${readsocket{/socket/name}{request string}}
9871 ${readsocket{inet:some.host:1234}{request string}}
9872 .endd
9873 For a Unix domain socket, the first substring must be the path to the socket.
9874 For an Internet socket, the first substring must contain &`inet:`& followed by
9875 a host name or IP address, followed by a colon and a port, which can be a
9876 number or the name of a TCP port in &_/etc/services_&. An IP address may
9877 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
9878 example:
9879 .code
9880 ${readsocket{inet:[::1]:1234}{request string}}
9881 .endd
9882 Only a single host name may be given, but if looking it up yields more than
9883 one IP address, they are each tried in turn until a connection is made. For
9884 both kinds of socket, Exim makes a connection, writes the request string
9885 unless it is an empty string; and no terminating NUL is ever sent)
9886 and reads from the socket until an end-of-file
9887 is read. A timeout of 5 seconds is applied. Additional, optional arguments
9888 extend what can be done. Firstly, you can vary the timeout. For example:
9889 .code
9890 ${readsocket{/socket/name}{request string}{3s}}
9891 .endd
9892
9893 The third argument is a list of options, of which the first element is the timeout
9894 and must be present if the argument is given.
9895 Further elements are options of form &'name=value'&.
9896 Two option types is currently recognised: shutdown and tls.
9897 The first defines whether (the default)
9898 or not a shutdown is done on the connection after sending the request.
9899 Example, to not do so (preferred, eg. by some webservers):
9900 .code
9901 ${readsocket{/socket/name}{request string}{3s:shutdown=no}}
9902 .endd
9903 .new
9904 The second, tls, controls the use of TLS on the connection. Example:
9905 .code
9906 ${readsocket{/socket/name}{request string}{3s:tls=yes}}
9907 .endd
9908 The default is to not use TLS.
9909 If it is enabled, a shutdown as descripbed above is never done.
9910 .wen
9911
9912 A fourth argument allows you to change any newlines that are in the data
9913 that is read, in the same way as for &%readfile%& (see above). This example
9914 turns them into spaces:
9915 .code
9916 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
9917 .endd
9918 As with all expansions, the substrings are expanded before the processing
9919 happens. Errors in these sub-expansions cause the expansion to fail. In
9920 addition, the following errors can occur:
9921
9922 .ilist
9923 Failure to create a socket file descriptor;
9924 .next
9925 Failure to connect the socket;
9926 .next
9927 Failure to write the request string;
9928 .next
9929 Timeout on reading from the socket.
9930 .endlist
9931
9932 By default, any of these errors causes the expansion to fail. However, if
9933 you supply a fifth substring, it is expanded and used when any of the above
9934 errors occurs. For example:
9935 .code
9936 ${readsocket{/socket/name}{request string}{3s}{\n}\
9937 {socket failure}}
9938 .endd
9939 You can test for the existence of a Unix domain socket by wrapping this
9940 expansion in &`${if exists`&, but there is a race condition between that test
9941 and the actual opening of the socket, so it is safer to use the fifth argument
9942 if you want to be absolutely sure of avoiding an expansion error for a
9943 non-existent Unix domain socket, or a failure to connect to an Internet socket.
9944
9945 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
9946 locks out the use of this expansion item in filter files.
9947
9948
9949 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9950 .cindex "expansion" "reducing a list to a scalar"
9951 .cindex "list" "reducing to a scalar"
9952 .vindex "&$value$&"
9953 .vindex "&$item$&"
9954 This operation reduces a list to a single, scalar string. After expansion,
9955 <&'string1'&> is interpreted as a list, colon-separated by default, but the
9956 separator can be changed in the usual way. Then <&'string2'&> is expanded and
9957 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
9958 list is assigned to &$item$& in turn, and <&'string3'&> is expanded for each of
9959 them. The result of that expansion is assigned to &$value$& before the next
9960 iteration. When the end of the list is reached, the final value of &$value$& is
9961 added to the expansion output. The &*reduce*& expansion item can be used in a
9962 number of ways. For example, to add up a list of numbers:
9963 .code
9964 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
9965 .endd
9966 The result of that expansion would be &`6`&. The maximum of a list of numbers
9967 can be found:
9968 .code
9969 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
9970 .endd
9971 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
9972 restored to what they were before. See also the &*filter*& and &*map*&
9973 expansion items.
9974
9975 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
9976 This item inserts &"raw"& header lines. It is described with the &%header%&
9977 expansion item above.
9978
9979 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
9980 {*&<&'string2'&>&*}}*&"
9981 .cindex "expansion" "running a command"
9982 .cindex "&%run%& expansion item"
9983 The command and its arguments are first expanded as one string. The string is
9984 split apart into individual arguments by spaces, and then the command is run
9985 in a separate process, but under the same uid and gid. As in other command
9986 executions from Exim, a shell is not used by default. If the command requires
9987 a shell, you must explicitly code it.
9988
9989 Since the arguments are split by spaces, when there is a variable expansion
9990 which has an empty result, it will cause the situation that the argument will
9991 simply be omitted when the program is actually executed by Exim. If the
9992 script/program requires a specific number of arguments and the expanded
9993 variable could possibly result in this empty expansion, the variable must be
9994 quoted. This is more difficult if the expanded variable itself could result
9995 in a string containing quotes, because it would interfere with the quotes
9996 around the command arguments. A possible guard against this is to wrap the
9997 variable in the &%sg%& operator to change any quote marks to some other
9998 character.
9999
10000 The standard input for the command exists, but is empty. The standard output
10001 and standard error are set to the same file descriptor.
10002 .cindex "return code" "from &%run%& expansion"
10003 .vindex "&$value$&"
10004 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
10005 and replaces the entire item; during this expansion, the standard output/error
10006 from the command is in the variable &$value$&. If the command fails,
10007 <&'string2'&>, if present, is expanded and used. Once again, during the
10008 expansion, the standard output/error from the command is in the variable
10009 &$value$&.
10010
10011 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
10012 can be the word &"fail"& (not in braces) to force expansion failure if the
10013 command does not succeed. If both strings are omitted, the result is contents
10014 of the standard output/error on success, and nothing on failure.
10015
10016 .vindex "&$run_in_acl$&"
10017 The standard output/error of the command is put in the variable &$value$&.
10018 In this ACL example, the output of a command is logged for the admin to
10019 troubleshoot:
10020 .code
10021 warn condition = ${run{/usr/bin/id}{yes}{no}}
10022 log_message = Output of id: $value
10023 .endd
10024 If the command requires shell idioms, such as the > redirect operator, the
10025 shell must be invoked directly, such as with:
10026 .code
10027 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
10028 .endd
10029
10030 .vindex "&$runrc$&"
10031 The return code from the command is put in the variable &$runrc$&, and this
10032 remains set afterwards, so in a filter file you can do things like this:
10033 .code
10034 if "${run{x y z}{}}$runrc" is 1 then ...
10035 elif $runrc is 2 then ...
10036 ...
10037 endif
10038 .endd
10039 If execution of the command fails (for example, the command does not exist),
10040 the return code is 127 &-- the same code that shells use for non-existent
10041 commands.
10042
10043 &*Warning*&: In a router or transport, you cannot assume the order in which
10044 option values are expanded, except for those preconditions whose order of
10045 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
10046 by the expansion of one option, and use it in another.
10047
10048 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
10049 out the use of this expansion item in filter files.
10050
10051
10052 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
10053 .cindex "expansion" "string substitution"
10054 .cindex "&%sg%& expansion item"
10055 This item works like Perl's substitution operator (s) with the global (/g)
10056 option; hence its name. However, unlike the Perl equivalent, Exim does not
10057 modify the subject string; instead it returns the modified string for insertion
10058 into the overall expansion. The item takes three arguments: the subject string,
10059 a regular expression, and a substitution string. For example:
10060 .code
10061 ${sg{abcdefabcdef}{abc}{xyz}}
10062 .endd
10063 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
10064 if any $, } or \ characters are required in the regular expression or in the
10065 substitution string, they have to be escaped. For example:
10066 .code
10067 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
10068 .endd
10069 yields &"defabc"&, and
10070 .code
10071 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
10072 .endd
10073 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
10074 the regular expression from string expansion.
10075
10076 The regular expression is compiled in 8-bit mode, working against bytes
10077 rather than any Unicode-aware character handling.
10078
10079
10080 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
10081 .cindex sorting "a list"
10082 .cindex list sorting
10083 .cindex expansion "list sorting"
10084 After expansion, <&'string'&> is interpreted as a list, colon-separated by
10085 default, but the separator can be changed in the usual way.
10086 The <&'comparator'&> argument is interpreted as the operator
10087 of a two-argument expansion condition.
10088 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
10089 The comparison should return true when applied to two values
10090 if the first value should sort before the second value.
10091 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
10092 the element being placed in &$item$&,
10093 to give values for comparison.
10094
10095 The item result is a sorted list,
10096 with the original list separator,
10097 of the list elements (in full) of the original.
10098
10099 Examples:
10100 .code
10101 ${sort{3:2:1:4}{<}{$item}}
10102 .endd
10103 sorts a list of numbers, and
10104 .code
10105 ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
10106 .endd
10107 will sort an MX lookup into priority order.
10108
10109
10110 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10111 .cindex "&%substr%& expansion item"
10112 .cindex "substring extraction"
10113 .cindex "expansion" "substring extraction"
10114 The three strings are expanded; the first two must yield numbers. Call them
10115 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10116 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10117 can use the simpler operator notation that avoids some of the braces:
10118 .code
10119 ${substr_<n>_<m>:<string>}
10120 .endd
10121 The second number is optional (in both notations).
10122 If it is absent in the simpler format, the preceding underscore must also be
10123 omitted.
10124
10125 The &%substr%& item can be used to extract more general substrings than
10126 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
10127 length required. For example
10128 .code
10129 ${substr{3}{2}{$local_part}}
10130 .endd
10131 If the starting offset is greater than the string length the result is the
10132 null string; if the length plus starting offset is greater than the string
10133 length, the result is the right-hand part of the string, starting from the
10134 given offset. The first byte (character) in the string has offset zero.
10135
10136 The &%substr%& expansion item can take negative offset values to count
10137 from the right-hand end of its operand. The last byte (character) is offset -1,
10138 the second-last is offset -2, and so on. Thus, for example,
10139 .code
10140 ${substr{-5}{2}{1234567}}
10141 .endd
10142 yields &"34"&. If the absolute value of a negative offset is greater than the
10143 length of the string, the substring starts at the beginning of the string, and
10144 the length is reduced by the amount of overshoot. Thus, for example,
10145 .code
10146 ${substr{-5}{2}{12}}
10147 .endd
10148 yields an empty string, but
10149 .code
10150 ${substr{-3}{2}{12}}
10151 .endd
10152 yields &"1"&.
10153
10154 When the second number is omitted from &%substr%&, the remainder of the string
10155 is taken if the offset is positive. If it is negative, all bytes (characters) in the
10156 string preceding the offset point are taken. For example, an offset of -1 and
10157 no length, as in these semantically identical examples:
10158 .code
10159 ${substr_-1:abcde}
10160 ${substr{-1}{abcde}}
10161 .endd
10162 yields all but the last character of the string, that is, &"abcd"&.
10163
10164 All measurement is done in bytes and is not UTF-8 aware.
10165
10166
10167
10168 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
10169 {*&<&'replacements'&>&*}}*&"
10170 .cindex "expansion" "character translation"
10171 .cindex "&%tr%& expansion item"
10172 This item does single-character (in bytes) translation on its subject string. The second
10173 argument is a list of characters to be translated in the subject string. Each
10174 matching character is replaced by the corresponding character from the
10175 replacement list. For example
10176 .code
10177 ${tr{abcdea}{ac}{13}}
10178 .endd
10179 yields &`1b3de1`&. If there are duplicates in the second character string, the
10180 last occurrence is used. If the third string is shorter than the second, its
10181 last character is replicated. However, if it is empty, no translation takes
10182 place.
10183
10184 All character handling is done in bytes and is not UTF-8 aware.
10185
10186 .endlist
10187
10188
10189
10190 .section "Expansion operators" "SECTexpop"
10191 .cindex "expansion" "operators"
10192 For expansion items that perform transformations on a single argument string,
10193 the &"operator"& notation is used because it is simpler and uses fewer braces.
10194 The substring is first expanded before the operation is applied to it. The
10195 following operations can be performed:
10196
10197 .vlist
10198 .vitem &*${address:*&<&'string'&>&*}*&
10199 .cindex "expansion" "RFC 2822 address handling"
10200 .cindex "&%address%& expansion item"
10201 The string is interpreted as an RFC 2822 address, as it might appear in a
10202 header line, and the effective address is extracted from it. If the string does
10203 not parse successfully, the result is empty.
10204
10205 The parsing correctly handles SMTPUTF8 Unicode in the string.
10206
10207
10208 .vitem &*${addresses:*&<&'string'&>&*}*&
10209 .cindex "expansion" "RFC 2822 address handling"
10210 .cindex "&%addresses%& expansion item"
10211 The string (after expansion) is interpreted as a list of addresses in RFC
10212 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
10213 operative address (&'local-part@domain'&) is extracted from each item, and the
10214 result of the expansion is a colon-separated list, with appropriate
10215 doubling of colons should any happen to be present in the email addresses.
10216 Syntactically invalid RFC2822 address items are omitted from the output.
10217
10218 It is possible to specify a character other than colon for the output
10219 separator by starting the string with > followed by the new separator
10220 character. For example:
10221 .code
10222 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
10223 .endd
10224 expands to &`ceo@up.stairs&&sec@base.ment`&. The string is expanded
10225 first, so if the expanded string starts with >, it may change the output
10226 separator unintentionally. This can be avoided by setting the output
10227 separator explicitly:
10228 .code
10229 ${addresses:>:$h_from:}
10230 .endd
10231
10232 Compare the &*address*& (singular)
10233 expansion item, which extracts the working address from a single RFC2822
10234 address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
10235 processing lists.
10236
10237 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
10238 a strict interpretation of header line formatting. Exim parses the bare,
10239 unquoted portion of an email address and if it finds a comma, treats it as an
10240 email address separator. For the example header line:
10241 .code
10242 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
10243 .endd
10244 The first example below demonstrates that Q-encoded email addresses are parsed
10245 properly if it is given the raw header (in this example, &`$rheader_from:`&).
10246 It does not see the comma because it's still encoded as "=2C". The second
10247 example below is passed the contents of &`$header_from:`&, meaning it gets
10248 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
10249 The third example shows that the presence of a comma is skipped when it is
10250 quoted. The fourth example shows SMTPUTF8 handling.
10251 .code
10252 # exim -be '${addresses:From: \
10253 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
10254 user@example.com
10255 # exim -be '${addresses:From: Last, First <user@example.com>}'
10256 Last:user@example.com
10257 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
10258 user@example.com
10259 # exim -be '${addresses:フィル <フィリップ@example.jp>}'
10260 フィリップ@example.jp
10261 .endd
10262
10263 .vitem &*${base32:*&<&'digits'&>&*}*&
10264 .cindex "&%base32%& expansion item"
10265 .cindex "expansion" "conversion to base 32"
10266 The string must consist entirely of decimal digits. The number is converted to
10267 base 32 and output as a (empty, for zero) string of characters.
10268 Only lowercase letters are used.
10269
10270 .vitem &*${base32d:*&<&'base-32&~digits'&>&*}*&
10271 .cindex "&%base32d%& expansion item"
10272 .cindex "expansion" "conversion to base 32"
10273 The string must consist entirely of base-32 digits.
10274 The number is converted to decimal and output as a string.
10275
10276 .vitem &*${base62:*&<&'digits'&>&*}*&
10277 .cindex "&%base62%& expansion item"
10278 .cindex "expansion" "conversion to base 62"
10279 The string must consist entirely of decimal digits. The number is converted to
10280 base 62 and output as a string of six characters, including leading zeros. In
10281 the few operating environments where Exim uses base 36 instead of base 62 for
10282 its message identifiers (because those systems do not have case-sensitive file
10283 names), base 36 is used by this operator, despite its name. &*Note*&: Just to
10284 be absolutely clear: this is &'not'& base64 encoding.
10285
10286 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
10287 .cindex "&%base62d%& expansion item"
10288 .cindex "expansion" "conversion to base 62"
10289 The string must consist entirely of base-62 digits, or, in operating
10290 environments where Exim uses base 36 instead of base 62 for its message
10291 identifiers, base-36 digits. The number is converted to decimal and output as a
10292 string.
10293
10294 .vitem &*${base64:*&<&'string'&>&*}*&
10295 .cindex "expansion" "base64 encoding"
10296 .cindex "base64 encoding" "in string expansion"
10297 .cindex "&%base64%& expansion item"
10298 .cindex certificate "base64 of DER"
10299 This operator converts a string into one that is base64 encoded.
10300
10301 If the string is a single variable of type certificate,
10302 returns the base64 encoding of the DER form of the certificate.
10303
10304
10305 .vitem &*${base64d:*&<&'string'&>&*}*&
10306 .cindex "expansion" "base64 decoding"
10307 .cindex "base64 decoding" "in string expansion"
10308 .cindex "&%base64d%& expansion item"
10309 This operator converts a base64-encoded string into the un-coded form.
10310
10311
10312 .vitem &*${domain:*&<&'string'&>&*}*&
10313 .cindex "domain" "extraction"
10314 .cindex "expansion" "domain extraction"
10315 The string is interpreted as an RFC 2822 address and the domain is extracted
10316 from it. If the string does not parse successfully, the result is empty.
10317
10318
10319 .vitem &*${escape:*&<&'string'&>&*}*&
10320 .cindex "expansion" "escaping non-printing characters"
10321 .cindex "&%escape%& expansion item"
10322 If the string contains any non-printing characters, they are converted to
10323 escape sequences starting with a backslash. Whether characters with the most
10324 significant bit set (so-called &"8-bit characters"&) count as printing or not
10325 is controlled by the &%print_topbitchars%& option.
10326
10327 .vitem &*${escape8bit:*&<&'string'&>&*}*&
10328 .cindex "expansion" "escaping 8-bit characters"
10329 .cindex "&%escape8bit%& expansion item"
10330 If the string contains and characters with the most significant bit set,
10331 they are converted to escape sequences starting with a backslash.
10332 Backslashes and DEL characters are also converted.
10333
10334
10335 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
10336 .cindex "expansion" "expression evaluation"
10337 .cindex "expansion" "arithmetic expression"
10338 .cindex "&%eval%& expansion item"
10339 These items supports simple arithmetic and bitwise logical operations in
10340 expansion strings. The string (after expansion) must be a conventional
10341 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
10342 logical operators, and parentheses. All operations are carried out using
10343 integer arithmetic. The operator priorities are as follows (the same as in the
10344 C programming language):
10345 .table2 70pt 300pt
10346 .irow &'highest:'& "not (~), negate (-)"
10347 .irow "" "multiply (*), divide (/), remainder (%)"
10348 .irow "" "plus (+), minus (-)"
10349 .irow "" "shift-left (<<), shift-right (>>)"
10350 .irow "" "and (&&)"
10351 .irow "" "xor (^)"
10352 .irow &'lowest:'& "or (|)"
10353 .endtable
10354 Binary operators with the same priority are evaluated from left to right. White
10355 space is permitted before or after operators.
10356
10357 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
10358 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
10359 decimal, even if they start with a leading zero; hexadecimal numbers are not
10360 permitted. This can be useful when processing numbers extracted from dates or
10361 times, which often do have leading zeros.
10362
10363 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
10364 or 1024*1024*1024,
10365 respectively. Negative numbers are supported. The result of the computation is
10366 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
10367
10368 .display
10369 &`${eval:1+1} `& yields 2
10370 &`${eval:1+2*3} `& yields 7
10371 &`${eval:(1+2)*3} `& yields 9
10372 &`${eval:2+42%5} `& yields 4
10373 &`${eval:0xc&amp;5} `& yields 4
10374 &`${eval:0xc|5} `& yields 13
10375 &`${eval:0xc^5} `& yields 9
10376 &`${eval:0xc>>1} `& yields 6
10377 &`${eval:0xc<<1} `& yields 24
10378 &`${eval:~255&amp;0x1234} `& yields 4608
10379 &`${eval:-(~255&amp;0x1234)} `& yields -4608
10380 .endd
10381
10382 As a more realistic example, in an ACL you might have
10383 .code
10384 deny message = Too many bad recipients
10385 condition = \
10386 ${if and { \
10387 {>{$rcpt_count}{10}} \
10388 { \
10389 < \
10390 {$recipients_count} \
10391 {${eval:$rcpt_count/2}} \
10392 } \
10393 }{yes}{no}}
10394 .endd
10395 The condition is true if there have been more than 10 RCPT commands and
10396 fewer than half of them have resulted in a valid recipient.
10397
10398
10399 .vitem &*${expand:*&<&'string'&>&*}*&
10400 .cindex "expansion" "re-expansion of substring"
10401 The &%expand%& operator causes a string to be expanded for a second time. For
10402 example,
10403 .code
10404 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
10405 .endd
10406 first looks up a string in a file while expanding the operand for &%expand%&,
10407 and then re-expands what it has found.
10408
10409
10410 .vitem &*${from_utf8:*&<&'string'&>&*}*&
10411 .cindex "Unicode"
10412 .cindex "UTF-8" "conversion from"
10413 .cindex "expansion" "UTF-8 conversion"
10414 .cindex "&%from_utf8%& expansion item"
10415 The world is slowly moving towards Unicode, although there are no standards for
10416 email yet. However, other applications (including some databases) are starting
10417 to store data in Unicode, using UTF-8 encoding. This operator converts from a
10418 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
10419 converted to underscores. The input must be a valid UTF-8 string. If it is not,
10420 the result is an undefined sequence of bytes.
10421
10422 Unicode code points with values less than 256 are compatible with ASCII and
10423 ISO-8859-1 (also known as Latin-1).
10424 For example, character 169 is the copyright symbol in both cases, though the
10425 way it is encoded is different. In UTF-8, more than one byte is needed for
10426 characters with code values greater than 127, whereas ISO-8859-1 is a
10427 single-byte encoding (but thereby limited to 256 characters). This makes
10428 translation from UTF-8 to ISO-8859-1 straightforward.
10429
10430
10431 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10432 .cindex "hash function" "textual"
10433 .cindex "expansion" "textual hash"
10434 The &%hash%& operator is a simpler interface to the hashing function that can
10435 be used when the two parameters are fixed numbers (as opposed to strings that
10436 change when expanded). The effect is the same as
10437 .code
10438 ${hash{<n>}{<m>}{<string>}}
10439 .endd
10440 See the description of the general &%hash%& item above for details. The
10441 abbreviation &%h%& can be used when &%hash%& is used as an operator.
10442
10443
10444
10445 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
10446 .cindex "base64 encoding" "conversion from hex"
10447 .cindex "expansion" "hex to base64"
10448 .cindex "&%hex2b64%& expansion item"
10449 This operator converts a hex string into one that is base64 encoded. This can
10450 be useful for processing the output of the various hashing functions.
10451
10452
10453
10454 .vitem &*${hexquote:*&<&'string'&>&*}*&
10455 .cindex "quoting" "hex-encoded unprintable characters"
10456 .cindex "&%hexquote%& expansion item"
10457 This operator converts non-printable characters in a string into a hex
10458 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
10459 as is, and other byte values are converted to &`\xNN`&, for example a
10460 byte value 127 is converted to &`\x7f`&.
10461
10462
10463 .vitem &*${ipv6denorm:*&<&'string'&>&*}*&
10464 .cindex "&%ipv6denorm%& expansion item"
10465 .cindex "IP address" normalisation
10466 This expands an IPv6 address to a full eight-element colon-separated set
10467 of hex digits including leading zeroes.
10468 A trailing ipv4-style dotted-decimal set is converted to hex.
10469 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
10470
10471 .vitem &*${ipv6norm:*&<&'string'&>&*}*&
10472 .cindex "&%ipv6norm%& expansion item"
10473 .cindex "IP address" normalisation
10474 .cindex "IP address" "canonical form"
10475 This converts an IPv6 address to canonical form.
10476 Leading zeroes of groups are omitted, and the longest
10477 set of zero-valued groups is replaced with a double colon.
10478 A trailing ipv4-style dotted-decimal set is converted to hex.
10479 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
10480
10481
10482 .vitem &*${lc:*&<&'string'&>&*}*&
10483 .cindex "case forcing in strings"
10484 .cindex "string" "case forcing"
10485 .cindex "lower casing"
10486 .cindex "expansion" "case forcing"
10487 .cindex "&%lc%& expansion item"
10488 This forces the letters in the string into lower-case, for example:
10489 .code
10490 ${lc:$local_part}
10491 .endd
10492 Case is defined per the system C locale.
10493
10494 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
10495 .cindex "expansion" "string truncation"
10496 .cindex "&%length%& expansion item"
10497 The &%length%& operator is a simpler interface to the &%length%& function that
10498 can be used when the parameter is a fixed number (as opposed to a string that
10499 changes when expanded). The effect is the same as
10500 .code
10501 ${length{<number>}{<string>}}
10502 .endd
10503 See the description of the general &%length%& item above for details. Note that
10504 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
10505 when &%length%& is used as an operator.
10506 All measurement is done in bytes and is not UTF-8 aware.
10507
10508
10509 .vitem &*${listcount:*&<&'string'&>&*}*&
10510 .cindex "expansion" "list item count"
10511 .cindex "list" "item count"
10512 .cindex "list" "count of items"
10513 .cindex "&%listcount%& expansion item"
10514 The string is interpreted as a list and the number of items is returned.
10515
10516
10517 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
10518 .cindex "expansion" "named list"
10519 .cindex "&%listnamed%& expansion item"
10520 The name is interpreted as a named list and the content of the list is returned,
10521 expanding any referenced lists, re-quoting as needed for colon-separation.
10522 If the optional type is given it must be one of "a", "d", "h" or "l"
10523 and selects address-, domain-, host- or localpart- lists to search among respectively.
10524 Otherwise all types are searched in an undefined order and the first
10525 matching list is returned.
10526
10527
10528 .vitem &*${local_part:*&<&'string'&>&*}*&
10529 .cindex "expansion" "local part extraction"
10530 .cindex "&%local_part%& expansion item"
10531 The string is interpreted as an RFC 2822 address and the local part is
10532 extracted from it. If the string does not parse successfully, the result is
10533 empty.
10534 The parsing correctly handles SMTPUTF8 Unicode in the string.
10535
10536
10537 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
10538 .cindex "masked IP address"
10539 .cindex "IP address" "masking"
10540 .cindex "CIDR notation"
10541 .cindex "expansion" "IP address masking"
10542 .cindex "&%mask%& expansion item"
10543 If the form of the string to be operated on is not an IP address followed by a
10544 slash and an integer (that is, a network address in CIDR notation), the
10545 expansion fails. Otherwise, this operator converts the IP address to binary,
10546 masks off the least significant bits according to the bit count, and converts
10547 the result back to text, with mask appended. For example,
10548 .code
10549 ${mask:10.111.131.206/28}
10550 .endd
10551 returns the string &"10.111.131.192/28"&. Since this operation is expected to
10552 be mostly used for looking up masked addresses in files, the result for an IPv6
10553 address uses dots to separate components instead of colons, because colon
10554 terminates a key string in lsearch files. So, for example,
10555 .code
10556 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
10557 .endd
10558 returns the string
10559 .code
10560 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
10561 .endd
10562 Letters in IPv6 addresses are always output in lower case.
10563
10564
10565 .vitem &*${md5:*&<&'string'&>&*}*&
10566 .cindex "MD5 hash"
10567 .cindex "expansion" "MD5 hash"
10568 .cindex certificate fingerprint
10569 .cindex "&%md5%& expansion item"
10570 The &%md5%& operator computes the MD5 hash value of the string, and returns it
10571 as a 32-digit hexadecimal number, in which any letters are in lower case.
10572
10573 If the string is a single variable of type certificate,
10574 returns the MD5 hash fingerprint of the certificate.
10575
10576
10577 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10578 .cindex "expansion" "numeric hash"
10579 .cindex "hash function" "numeric"
10580 The &%nhash%& operator is a simpler interface to the numeric hashing function
10581 that can be used when the two parameters are fixed numbers (as opposed to
10582 strings that change when expanded). The effect is the same as
10583 .code
10584 ${nhash{<n>}{<m>}{<string>}}
10585 .endd
10586 See the description of the general &%nhash%& item above for details.
10587
10588
10589 .vitem &*${quote:*&<&'string'&>&*}*&
10590 .cindex "quoting" "in string expansions"
10591 .cindex "expansion" "quoting"
10592 .cindex "&%quote%& expansion item"
10593 The &%quote%& operator puts its argument into double quotes if it
10594 is an empty string or
10595 contains anything other than letters, digits, underscores, dots, and hyphens.
10596 Any occurrences of double quotes and backslashes are escaped with a backslash.
10597 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
10598 respectively For example,
10599 .code
10600 ${quote:ab"*"cd}
10601 .endd
10602 becomes
10603 .code
10604 "ab\"*\"cd"
10605 .endd
10606 The place where this is useful is when the argument is a substitution from a
10607 variable or a message header.
10608
10609 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
10610 .cindex "&%quote_local_part%& expansion item"
10611 This operator is like &%quote%&, except that it quotes the string only if
10612 required to do so by the rules of RFC 2822 for quoting local parts. For
10613 example, a plus sign would not cause quoting (but it would for &%quote%&).
10614 If you are creating a new email address from the contents of &$local_part$&
10615 (or any other unknown data), you should always use this operator.
10616
10617 This quoting determination is not SMTPUTF8-aware, thus quoting non-ASCII data
10618 will likely use the quoting form.
10619 Thus &'${quote_local_part:フィル}'& will always become &'"フィル"'&.
10620
10621
10622 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
10623 .cindex "quoting" "lookup-specific"
10624 This operator applies lookup-specific quoting rules to the string. Each
10625 query-style lookup type has its own quoting rules which are described with
10626 the lookups in chapter &<<CHAPfdlookup>>&. For example,
10627 .code
10628 ${quote_ldap:two * two}
10629 .endd
10630 returns
10631 .code
10632 two%20%5C2A%20two
10633 .endd
10634 For single-key lookup types, no quoting is ever necessary and this operator
10635 yields an unchanged string.
10636
10637
10638 .vitem &*${randint:*&<&'n'&>&*}*&
10639 .cindex "random number"
10640 This operator returns a somewhat random number which is less than the
10641 supplied number and is at least 0. The quality of this randomness depends
10642 on how Exim was built; the values are not suitable for keying material.
10643 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
10644 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
10645 for versions of GnuTLS with that function.
10646 Otherwise, the implementation may be arc4random(), random() seeded by
10647 srandomdev() or srandom(), or a custom implementation even weaker than
10648 random().
10649
10650
10651 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
10652 .cindex "expansion" "IP address"
10653 This operator reverses an IP address; for IPv4 addresses, the result is in
10654 dotted-quad decimal form, while for IPv6 addresses the result is in
10655 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
10656 for DNS. For example,
10657 .code
10658 ${reverse_ip:192.0.2.4}
10659 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
10660 .endd
10661 returns
10662 .code
10663 4.2.0.192
10664 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
10665 .endd
10666
10667
10668 .vitem &*${rfc2047:*&<&'string'&>&*}*&
10669 .cindex "expansion" "RFC 2047"
10670 .cindex "RFC 2047" "expansion operator"
10671 .cindex "&%rfc2047%& expansion item"
10672 This operator encodes text according to the rules of RFC 2047. This is an
10673 encoding that is used in header lines to encode non-ASCII characters. It is
10674 assumed that the input string is in the encoding specified by the
10675 &%headers_charset%& option, which gets its default at build time. If the string
10676 contains only characters in the range 33&--126, and no instances of the
10677 characters
10678 .code
10679 ? = ( ) < > @ , ; : \ " . [ ] _
10680 .endd
10681 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
10682 string, using as many &"encoded words"& as necessary to encode all the
10683 characters.
10684
10685
10686 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
10687 .cindex "expansion" "RFC 2047"
10688 .cindex "RFC 2047" "decoding"
10689 .cindex "&%rfc2047d%& expansion item"
10690 This operator decodes strings that are encoded as per RFC 2047. Binary zero
10691 bytes are replaced by question marks. Characters are converted into the
10692 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
10693 not recognized unless &%check_rfc2047_length%& is set false.
10694
10695 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
10696 access a header line, RFC 2047 decoding is done automatically. You do not need
10697 to use this operator as well.
10698
10699
10700
10701 .vitem &*${rxquote:*&<&'string'&>&*}*&
10702 .cindex "quoting" "in regular expressions"
10703 .cindex "regular expressions" "quoting"
10704 .cindex "&%rxquote%& expansion item"
10705 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
10706 characters in its argument. This is useful when substituting the values of
10707 variables or headers inside regular expressions.
10708
10709
10710 .vitem &*${sha1:*&<&'string'&>&*}*&
10711 .cindex "SHA-1 hash"
10712 .cindex "expansion" "SHA-1 hashing"
10713 .cindex certificate fingerprint
10714 .cindex "&%sha1%& expansion item"
10715 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
10716 it as a 40-digit hexadecimal number, in which any letters are in upper case.
10717
10718 If the string is a single variable of type certificate,
10719 returns the SHA-1 hash fingerprint of the certificate.
10720
10721
10722 .vitem &*${sha256:*&<&'string'&>&*}*&
10723 .cindex "SHA-256 hash"
10724 .cindex certificate fingerprint
10725 .cindex "expansion" "SHA-256 hashing"
10726 .cindex "&%sha256%& expansion item"
10727 The &%sha256%& operator computes the SHA-256 hash value of the string
10728 and returns
10729 it as a 64-digit hexadecimal number, in which any letters are in upper case.
10730
10731 If the string is a single variable of type certificate,
10732 returns the SHA-256 hash fingerprint of the certificate.
10733
10734
10735 .vitem &*${sha3:*&<&'string'&>&*}*& &&&
10736 &*${sha3_<n>:*&<&'string'&>&*}*&
10737 .cindex "SHA3 hash"
10738 .cindex "expansion" "SHA3 hashing"
10739 .cindex "&%sha3%& expansion item"
10740 The &%sha3%& operator computes the SHA3-256 hash value of the string
10741 and returns
10742 it as a 64-digit hexadecimal number, in which any letters are in upper case.
10743
10744 If a number is appended, separated by an underbar, it specifies
10745 the output length. Values of 224, 256, 384 and 512 are accepted;
10746 with 256 being the default.
10747
10748 The &%sha3%& expansion item is only supported if Exim has been
10749 compiled with GnuTLS 3.5.0 or later,
10750 or OpenSSL 1.1.1 or later.
10751 The macro "_CRYPTO_HASH_SHA3" will be defined if it is supported.
10752
10753
10754 .vitem &*${stat:*&<&'string'&>&*}*&
10755 .cindex "expansion" "statting a file"
10756 .cindex "file" "extracting characteristics"
10757 .cindex "&%stat%& expansion item"
10758 The string, after expansion, must be a file path. A call to the &[stat()]&
10759 function is made for this path. If &[stat()]& fails, an error occurs and the
10760 expansion fails. If it succeeds, the data from the stat replaces the item, as a
10761 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
10762 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
10763 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
10764 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
10765 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
10766 can extract individual fields using the &%extract%& expansion item.
10767
10768 The use of the &%stat%& expansion in users' filter files can be locked out by
10769 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
10770 systems for files larger than 2GB.
10771
10772 .vitem &*${str2b64:*&<&'string'&>&*}*&
10773 .cindex "&%str2b64%& expansion item"
10774 Now deprecated, a synonym for the &%base64%& expansion operator.
10775
10776
10777
10778 .vitem &*${strlen:*&<&'string'&>&*}*&
10779 .cindex "expansion" "string length"
10780 .cindex "string" "length in expansion"
10781 .cindex "&%strlen%& expansion item"
10782 The item is replace by the length of the expanded string, expressed as a
10783 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
10784 All measurement is done in bytes and is not UTF-8 aware.
10785
10786
10787 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
10788 .cindex "&%substr%& expansion item"
10789 .cindex "substring extraction"
10790 .cindex "expansion" "substring expansion"
10791 The &%substr%& operator is a simpler interface to the &%substr%& function that
10792 can be used when the two parameters are fixed numbers (as opposed to strings
10793 that change when expanded). The effect is the same as
10794 .code
10795 ${substr{<start>}{<length>}{<string>}}
10796 .endd
10797 See the description of the general &%substr%& item above for details. The
10798 abbreviation &%s%& can be used when &%substr%& is used as an operator.
10799 All measurement is done in bytes and is not UTF-8 aware.
10800
10801 .vitem &*${time_eval:*&<&'string'&>&*}*&
10802 .cindex "&%time_eval%& expansion item"
10803 .cindex "time interval" "decoding"
10804 This item converts an Exim time interval such as &`2d4h5m`& into a number of
10805 seconds.
10806
10807 .vitem &*${time_interval:*&<&'string'&>&*}*&
10808 .cindex "&%time_interval%& expansion item"
10809 .cindex "time interval" "formatting"
10810 The argument (after sub-expansion) must be a sequence of decimal digits that
10811 represents an interval of time as a number of seconds. It is converted into a
10812 number of larger units and output in Exim's normal time format, for example,
10813 &`1w3d4h2m6s`&.
10814
10815 .vitem &*${uc:*&<&'string'&>&*}*&
10816 .cindex "case forcing in strings"
10817 .cindex "string" "case forcing"
10818 .cindex "upper casing"
10819 .cindex "expansion" "case forcing"
10820 .cindex "&%uc%& expansion item"
10821 This forces the letters in the string into upper-case.
10822 Case is defined per the system C locale.
10823
10824 .vitem &*${utf8clean:*&<&'string'&>&*}*&
10825 .cindex "correction of invalid utf-8 sequences in strings"
10826 .cindex "utf-8" "utf-8 sequences"
10827 .cindex "incorrect utf-8"
10828 .cindex "expansion" "utf-8 forcing"
10829 .cindex "&%utf8clean%& expansion item"
10830 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
10831 .new
10832 In versions of Exim before 4.92, this did not correctly do so for a truncated
10833 final codepoint's encoding, and the character would be silently dropped.
10834 If you must handle detection of this scenario across both sets of Exim behavior,
10835 the complexity will depend upon the task.
10836 For instance, to detect if the first character is multibyte and a 1-byte
10837 extraction can be successfully used as a path component (as is common for
10838 dividing up delivery folders), you might use:
10839 .code
10840 condition = ${if inlist{${utf8clean:${length_1:$local_part}}}{:?}{yes}{no}}
10841 .endd
10842 (which will false-positive if the first character of the local part is a
10843 literal question mark).
10844 .wen
10845
10846 .vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
10847 "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
10848 "&*${utf8_localpart_to_alabel:*&<&'string'&>&*}*&" &&&
10849 "&*${utf8_localpart_from_alabel:*&<&'string'&>&*}*&"
10850 .cindex expansion UTF-8
10851 .cindex UTF-8 expansion
10852 .cindex EAI
10853 .cindex internationalisation
10854 .cindex "&%utf8_domain_to_alabel%& expansion item"
10855 .cindex "&%utf8_domain_from_alabel%& expansion item"
10856 .cindex "&%utf8_localpart_to_alabel%& expansion item"
10857 .cindex "&%utf8_localpart_from_alabel%& expansion item"
10858 These convert EAI mail name components between UTF-8 and a-label forms.
10859 For information on internationalisation support see &<<SECTi18nMTA>>&.
10860 .endlist
10861
10862
10863
10864
10865
10866
10867 .section "Expansion conditions" "SECTexpcond"
10868 .scindex IIDexpcond "expansion" "conditions"
10869 The following conditions are available for testing by the &%${if%& construct
10870 while expanding strings:
10871
10872 .vlist
10873 .vitem &*!*&<&'condition'&>
10874 .cindex "expansion" "negating a condition"
10875 .cindex "negation" "in expansion condition"
10876 Preceding any condition with an exclamation mark negates the result of the
10877 condition.
10878
10879 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10880 .cindex "numeric comparison"
10881 .cindex "expansion" "numeric comparison"
10882 There are a number of symbolic operators for doing numeric comparisons. They
10883 are:
10884 .display
10885 &`= `& equal
10886 &`== `& equal
10887 &`> `& greater
10888 &`>= `& greater or equal
10889 &`< `& less
10890 &`<= `& less or equal
10891 .endd
10892 For example:
10893 .code
10894 ${if >{$message_size}{10M} ...
10895 .endd
10896 Note that the general negation operator provides for inequality testing. The
10897 two strings must take the form of optionally signed decimal integers,
10898 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
10899 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
10900 As a special case, the numerical value of an empty string is taken as
10901 zero.
10902
10903 In all cases, a relative comparator OP is testing if <&'string1'&> OP
10904 <&'string2'&>; the above example is checking if &$message_size$& is larger than
10905 10M, not if 10M is larger than &$message_size$&.
10906
10907
10908 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
10909 {*&<&'arg2'&>&*}...}*&
10910 .cindex "expansion" "calling an acl"
10911 .cindex "&%acl%&" "expansion condition"
10912 The name and zero to nine argument strings are first expanded separately. The expanded
10913 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
10914 Any unused are made empty. The variable &$acl_narg$& is set to the number of
10915 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
10916 and may use the variables; if another acl expansion is used the values
10917 are restored after it returns. If the ACL sets
10918 a value using a "message =" modifier the variable $value becomes
10919 the result of the expansion, otherwise it is empty.
10920 If the ACL returns accept the condition is true; if deny, false.
10921 If the ACL returns defer the result is a forced-fail.
10922
10923 .vitem &*bool&~{*&<&'string'&>&*}*&
10924 .cindex "expansion" "boolean parsing"
10925 .cindex "&%bool%& expansion condition"
10926 This condition turns a string holding a true or false representation into
10927 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
10928 (case-insensitively); also integer numbers map to true if non-zero,
10929 false if zero.
10930 An empty string is treated as false.
10931 Leading and trailing whitespace is ignored;
10932 thus a string consisting only of whitespace is false.
10933 All other string values will result in expansion failure.
10934
10935 When combined with ACL variables, this expansion condition will let you
10936 make decisions in one place and act on those decisions in another place.
10937 For example:
10938 .code
10939 ${if bool{$acl_m_privileged_sender} ...
10940 .endd
10941
10942
10943 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
10944 .cindex "expansion" "boolean parsing"
10945 .cindex "&%bool_lax%& expansion condition"
10946 Like &%bool%&, this condition turns a string into a boolean state. But
10947 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
10948 loose definition that the Router &%condition%& option uses. The empty string
10949 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
10950 true. Leading and trailing whitespace is ignored.
10951
10952 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
10953
10954 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10955 .cindex "expansion" "encrypted comparison"
10956 .cindex "encrypted strings, comparing"
10957 .cindex "&%crypteq%& expansion condition"
10958 This condition is included in the Exim binary if it is built to support any
10959 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
10960 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
10961 included in the binary.
10962
10963 The &%crypteq%& condition has two arguments. The first is encrypted and
10964 compared against the second, which is already encrypted. The second string may
10965 be in the LDAP form for storing encrypted strings, which starts with the
10966 encryption type in curly brackets, followed by the data. If the second string
10967 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
10968 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
10969 Typically this will be a field from a password file. An example of an encrypted
10970 string in LDAP form is:
10971 .code
10972 {md5}CY9rzUYh03PK3k6DJie09g==
10973 .endd
10974 If such a string appears directly in an expansion, the curly brackets have to
10975 be quoted, because they are part of the expansion syntax. For example:
10976 .code
10977 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
10978 .endd
10979 The following encryption types (whose names are matched case-independently) are
10980 supported:
10981
10982 .ilist
10983 .cindex "MD5 hash"
10984 .cindex "base64 encoding" "in encrypted password"
10985 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
10986 printable characters to compare with the remainder of the second string. If the
10987 length of the comparison string is 24, Exim assumes that it is base64 encoded
10988 (as in the above example). If the length is 32, Exim assumes that it is a
10989 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
10990 comparison fails.
10991
10992 .next
10993 .cindex "SHA-1 hash"
10994 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
10995 printable characters to compare with the remainder of the second string. If the
10996 length of the comparison string is 28, Exim assumes that it is base64 encoded.
10997 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
10998 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
10999
11000 .next
11001 .cindex "&[crypt()]&"
11002 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
11003 only the first eight characters of the password. However, in modern operating
11004 systems this is no longer true, and in many cases the entire password is used,
11005 whatever its length.
11006
11007 .next
11008 .cindex "&[crypt16()]&"
11009 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
11010 use up to 16 characters of the password in some operating systems. Again, in
11011 modern operating systems, more characters may be used.
11012 .endlist
11013 Exim has its own version of &[crypt16()]&, which is just a double call to
11014 &[crypt()]&. For operating systems that have their own version, setting
11015 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
11016 operating system version instead of its own. This option is set by default in
11017 the OS-dependent &_Makefile_& for those operating systems that are known to
11018 support &[crypt16()]&.
11019
11020 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
11021 it was not using the same algorithm as some operating systems' versions. It
11022 turns out that as well as &[crypt16()]& there is a function called
11023 &[bigcrypt()]& in some operating systems. This may or may not use the same
11024 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
11025
11026 However, since there is now a move away from the traditional &[crypt()]&
11027 functions towards using SHA1 and other algorithms, tidying up this area of
11028 Exim is seen as very low priority.
11029
11030 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
11031 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
11032 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
11033 default is &`{crypt}`&. Whatever the default, you can always use either
11034 function by specifying it explicitly in curly brackets.
11035
11036 .vitem &*def:*&<&'variable&~name'&>
11037 .cindex "expansion" "checking for empty variable"
11038 .cindex "&%def%& expansion condition"
11039 The &%def%& condition must be followed by the name of one of the expansion
11040 variables defined in section &<<SECTexpvar>>&. The condition is true if the
11041 variable does not contain the empty string. For example:
11042 .code
11043 ${if def:sender_ident {from $sender_ident}}
11044 .endd
11045 Note that the variable name is given without a leading &%$%& character. If the
11046 variable does not exist, the expansion fails.
11047
11048 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
11049 &~&*def:h_*&<&'header&~name'&>&*:*&"
11050 .cindex "expansion" "checking header line existence"
11051 This condition is true if a message is being processed and the named header
11052 exists in the message. For example,
11053 .code
11054 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
11055 .endd
11056 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
11057 the header name must be terminated by a colon if white space does not follow.
11058
11059 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11060 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11061 .cindex "string" "comparison"
11062 .cindex "expansion" "string comparison"
11063 .cindex "&%eq%& expansion condition"
11064 .cindex "&%eqi%& expansion condition"
11065 The two substrings are first expanded. The condition is true if the two
11066 resulting strings are identical. For &%eq%& the comparison includes the case of
11067 letters, whereas for &%eqi%& the comparison is case-independent, where
11068 case is defined per the system C locale.
11069
11070 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
11071 .cindex "expansion" "file existence test"
11072 .cindex "file" "existence test"
11073 .cindex "&%exists%&, expansion condition"
11074 The substring is first expanded and then interpreted as an absolute path. The
11075 condition is true if the named file (or directory) exists. The existence test
11076 is done by calling the &[stat()]& function. The use of the &%exists%& test in
11077 users' filter files may be locked out by the system administrator.
11078
11079 .vitem &*first_delivery*&
11080 .cindex "delivery" "first"
11081 .cindex "first delivery"
11082 .cindex "expansion" "first delivery test"
11083 .cindex "&%first_delivery%& expansion condition"
11084 This condition, which has no data, is true during a message's first delivery
11085 attempt. It is false during any subsequent delivery attempts.
11086
11087
11088 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
11089 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
11090 .cindex "list" "iterative conditions"
11091 .cindex "expansion" "&*forall*& condition"
11092 .cindex "expansion" "&*forany*& condition"
11093 .vindex "&$item$&"
11094 These conditions iterate over a list. The first argument is expanded to form
11095 the list. By default, the list separator is a colon, but it can be changed by
11096 the normal method. The second argument is interpreted as a condition that is to
11097 be applied to each item in the list in turn. During the interpretation of the
11098 condition, the current list item is placed in a variable called &$item$&.
11099 .ilist
11100 For &*forany*&, interpretation stops if the condition is true for any item, and
11101 the result of the whole condition is true. If the condition is false for all
11102 items in the list, the overall condition is false.
11103 .next
11104 For &*forall*&, interpretation stops if the condition is false for any item,
11105 and the result of the whole condition is false. If the condition is true for
11106 all items in the list, the overall condition is true.
11107 .endlist
11108 Note that negation of &*forany*& means that the condition must be false for all
11109 items for the overall condition to succeed, and negation of &*forall*& means
11110 that the condition must be false for at least one item. In this example, the
11111 list separator is changed to a comma:
11112 .code
11113 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
11114 .endd
11115 The value of &$item$& is saved and restored while &*forany*& or &*forall*& is
11116 being processed, to enable these expansion items to be nested.
11117
11118 To scan a named list, expand it with the &*listnamed*& operator.
11119
11120
11121 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11122 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11123 .cindex "string" "comparison"
11124 .cindex "expansion" "string comparison"
11125 .cindex "&%ge%& expansion condition"
11126 .cindex "&%gei%& expansion condition"
11127 The two substrings are first expanded. The condition is true if the first
11128 string is lexically greater than or equal to the second string. For &%ge%& the
11129 comparison includes the case of letters, whereas for &%gei%& the comparison is
11130 case-independent.
11131 Case and collation order are defined per the system C locale.
11132
11133 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11134 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11135 .cindex "string" "comparison"
11136 .cindex "expansion" "string comparison"
11137 .cindex "&%gt%& expansion condition"
11138 .cindex "&%gti%& expansion condition"
11139 The two substrings are first expanded. The condition is true if the first
11140 string is lexically greater than the second string. For &%gt%& the comparison
11141 includes the case of letters, whereas for &%gti%& the comparison is
11142 case-independent.
11143 Case and collation order are defined per the system C locale.
11144
11145 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11146 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11147 .cindex "string" "comparison"
11148 .cindex "list" "iterative conditions"
11149 Both strings are expanded; the second string is treated as a list of simple
11150 strings; if the first string is a member of the second, then the condition
11151 is true.
11152 For the case-independent &%inlisti%& condition, case is defined per the system C locale.
11153
11154 These are simpler to use versions of the more powerful &*forany*& condition.
11155 Examples, and the &*forany*& equivalents:
11156 .code
11157 ${if inlist{needle}{foo:needle:bar}}
11158 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
11159 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
11160 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
11161 .endd
11162
11163 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
11164 &*isip4&~{*&<&'string'&>&*}*& &&&
11165 &*isip6&~{*&<&'string'&>&*}*&
11166 .cindex "IP address" "testing string format"
11167 .cindex "string" "testing for IP address"
11168 .cindex "&%isip%& expansion condition"
11169 .cindex "&%isip4%& expansion condition"
11170 .cindex "&%isip6%& expansion condition"
11171 The substring is first expanded, and then tested to see if it has the form of
11172 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
11173 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
11174
11175 For an IPv4 address, the test is for four dot-separated components, each of
11176 which consists of from one to three digits. For an IPv6 address, up to eight
11177 colon-separated components are permitted, each containing from one to four
11178 hexadecimal digits. There may be fewer than eight components if an empty
11179 component (adjacent colons) is present. Only one empty component is permitted.
11180
11181 &*Note*&: The checks used to be just on the form of the address; actual numerical
11182 values were not considered. Thus, for example, 999.999.999.999 passed the IPv4
11183 check.
11184 This is no longer the case.
11185
11186 The main use of these tests is to distinguish between IP addresses and
11187 host names, or between IPv4 and IPv6 addresses. For example, you could use
11188 .code
11189 ${if isip4{$sender_host_address}...
11190 .endd
11191 to test which IP version an incoming SMTP connection is using.
11192
11193 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
11194 .cindex "LDAP" "use for authentication"
11195 .cindex "expansion" "LDAP authentication test"
11196 .cindex "&%ldapauth%& expansion condition"
11197 This condition supports user authentication using LDAP. See section
11198 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
11199 queries. For this use, the query must contain a user name and password. The
11200 query itself is not used, and can be empty. The condition is true if the
11201 password is not empty, and the user name and password are accepted by the LDAP
11202 server. An empty password is rejected without calling LDAP because LDAP binds
11203 with an empty password are considered anonymous regardless of the username, and
11204 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
11205 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
11206 this can be used.
11207
11208
11209 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11210 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11211 .cindex "string" "comparison"
11212 .cindex "expansion" "string comparison"
11213 .cindex "&%le%& expansion condition"
11214 .cindex "&%lei%& expansion condition"
11215 The two substrings are first expanded. The condition is true if the first
11216 string is lexically less than or equal to the second string. For &%le%& the
11217 comparison includes the case of letters, whereas for &%lei%& the comparison is
11218 case-independent.
11219 Case and collation order are defined per the system C locale.
11220
11221 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11222 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11223 .cindex "string" "comparison"
11224 .cindex "expansion" "string comparison"
11225 .cindex "&%lt%& expansion condition"
11226 .cindex "&%lti%& expansion condition"
11227 The two substrings are first expanded. The condition is true if the first
11228 string is lexically less than the second string. For &%lt%& the comparison
11229 includes the case of letters, whereas for &%lti%& the comparison is
11230 case-independent.
11231 Case and collation order are defined per the system C locale.
11232
11233
11234 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11235 .cindex "expansion" "regular expression comparison"
11236 .cindex "regular expressions" "match in expanded string"
11237 .cindex "&%match%& expansion condition"
11238 The two substrings are first expanded. The second is then treated as a regular
11239 expression and applied to the first. Because of the pre-expansion, if the
11240 regular expression contains dollar, or backslash characters, they must be
11241 escaped. Care must also be taken if the regular expression contains braces
11242 (curly brackets). A closing brace must be escaped so that it is not taken as a
11243 premature termination of <&'string2'&>. The easiest approach is to use the
11244 &`\N`& feature to disable expansion of the regular expression.
11245 For example,
11246 .code
11247 ${if match {$local_part}{\N^\d{3}\N} ...
11248 .endd
11249 If the whole expansion string is in double quotes, further escaping of
11250 backslashes is also required.
11251
11252 The condition is true if the regular expression match succeeds.
11253 The regular expression is not required to begin with a circumflex
11254 metacharacter, but if there is no circumflex, the expression is not anchored,
11255 and it may match anywhere in the subject, not just at the start. If you want
11256 the pattern to match at the end of the subject, you must include the &`$`&
11257 metacharacter at an appropriate point.
11258 All character handling is done in bytes and is not UTF-8 aware,
11259 but we might change this in a future Exim release.
11260
11261 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
11262 At the start of an &%if%& expansion the values of the numeric variable
11263 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
11264 succeeds causes them to be reset to the substrings of that condition and they
11265 will have these values during the expansion of the success string. At the end
11266 of the &%if%& expansion, the previous values are restored. After testing a
11267 combination of conditions using &%or%&, the subsequent values of the numeric
11268 variables are those of the condition that succeeded.
11269
11270 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11271 .cindex "&%match_address%& expansion condition"
11272 See &*match_local_part*&.
11273
11274 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11275 .cindex "&%match_domain%& expansion condition"
11276 See &*match_local_part*&.
11277
11278 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11279 .cindex "&%match_ip%& expansion condition"
11280 This condition matches an IP address to a list of IP address patterns. It must
11281 be followed by two argument strings. The first (after expansion) must be an IP
11282 address or an empty string. The second (not expanded) is a restricted host
11283 list that can match only an IP address, not a host name. For example:
11284 .code
11285 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
11286 .endd
11287 The specific types of host list item that are permitted in the list are:
11288
11289 .ilist
11290 An IP address, optionally with a CIDR mask.
11291 .next
11292 A single asterisk, which matches any IP address.
11293 .next
11294 An empty item, which matches only if the IP address is empty. This could be
11295 useful for testing for a locally submitted message or one from specific hosts
11296 in a single test such as
11297 . ==== As this is a nested list, any displays it contains must be indented
11298 . ==== as otherwise they are too far to the left. This comment applies to
11299 . ==== the use of xmlto plus fop. There's no problem when formatting with
11300 . ==== sdop, with or without the extra indent.
11301 .code
11302 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
11303 .endd
11304 where the first item in the list is the empty string.
11305 .next
11306 The item @[] matches any of the local host's interface addresses.
11307 .next
11308 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
11309 even if &`net-`& is not specified. There is never any attempt to turn the IP
11310 address into a host name. The most common type of linear search for
11311 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
11312 masks. For example:
11313 .code
11314 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
11315 .endd
11316 It is of course possible to use other kinds of lookup, and in such a case, you
11317 do need to specify the &`net-`& prefix if you want to specify a specific
11318 address mask, for example:
11319 .code
11320 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
11321 .endd
11322 However, unless you are combining a &%match_ip%& condition with others, it is
11323 just as easy to use the fact that a lookup is itself a condition, and write:
11324 .code
11325 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
11326 .endd
11327 .endlist ilist
11328
11329 Note that <&'string2'&> is not itself subject to string expansion, unless
11330 Exim was built with the EXPAND_LISTMATCH_RHS option.
11331
11332 Consult section &<<SECThoslispatip>>& for further details of these patterns.
11333
11334 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11335 .cindex "domain list" "in expansion condition"
11336 .cindex "address list" "in expansion condition"
11337 .cindex "local part" "list, in expansion condition"
11338 .cindex "&%match_local_part%& expansion condition"
11339 This condition, together with &%match_address%& and &%match_domain%&, make it
11340 possible to test domain, address, and local part lists within expansions. Each
11341 condition requires two arguments: an item and a list to match. A trivial
11342 example is:
11343 .code
11344 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
11345 .endd
11346 In each case, the second argument may contain any of the allowable items for a
11347 list of the appropriate type. Also, because the second argument
11348 is a standard form of list, it is possible to refer to a named list.
11349 Thus, you can use conditions like this:
11350 .code
11351 ${if match_domain{$domain}{+local_domains}{...
11352 .endd
11353 .cindex "&`+caseful`&"
11354 For address lists, the matching starts off caselessly, but the &`+caseful`&
11355 item can be used, as in all address lists, to cause subsequent items to
11356 have their local parts matched casefully. Domains are always matched
11357 caselessly.
11358
11359 Note that <&'string2'&> is not itself subject to string expansion, unless
11360 Exim was built with the EXPAND_LISTMATCH_RHS option.
11361
11362 &*Note*&: Host lists are &'not'& supported in this way. This is because
11363 hosts have two identities: a name and an IP address, and it is not clear
11364 how to specify cleanly how such a test would work. However, IP addresses can be
11365 matched using &%match_ip%&.
11366
11367 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
11368 .cindex "PAM authentication"
11369 .cindex "AUTH" "with PAM"
11370 .cindex "Solaris" "PAM support"
11371 .cindex "expansion" "PAM authentication test"
11372 .cindex "&%pam%& expansion condition"
11373 &'Pluggable Authentication Modules'&
11374 (&url(http://www.kernel.org/pub/linux/libs/pam/)) are a facility that is
11375 available in the latest releases of Solaris and in some GNU/Linux
11376 distributions. The Exim support, which is intended for use in conjunction with
11377 the SMTP AUTH command, is available only if Exim is compiled with
11378 .code
11379 SUPPORT_PAM=yes
11380 .endd
11381 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
11382 in some releases of GNU/Linux &%-ldl%& is also needed.
11383
11384 The argument string is first expanded, and the result must be a
11385 colon-separated list of strings. Leading and trailing white space is ignored.
11386 The PAM module is initialized with the service name &"exim"& and the user name
11387 taken from the first item in the colon-separated data string (<&'string1'&>).
11388 The remaining items in the data string are passed over in response to requests
11389 from the authentication function. In the simple case there will only be one
11390 request, for a password, so the data consists of just two strings.
11391
11392 There can be problems if any of the strings are permitted to contain colon
11393 characters. In the usual way, these have to be doubled to avoid being taken as
11394 separators. If the data is being inserted from a variable, the &%sg%& expansion
11395 item can be used to double any existing colons. For example, the configuration
11396 of a LOGIN authenticator might contain this setting:
11397 .code
11398 server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
11399 .endd
11400 For a PLAIN authenticator you could use:
11401 .code
11402 server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
11403 .endd
11404 In some operating systems, PAM authentication can be done only from a process
11405 running as root. Since Exim is running as the Exim user when receiving
11406 messages, this means that PAM cannot be used directly in those systems.
11407 A patched version of the &'pam_unix'& module that comes with the
11408 Linux PAM package is available from &url(http://www.e-admin.de/pam_exim/).
11409 The patched module allows one special uid/gid combination, in addition to root,
11410 to authenticate. If you build the patched module to allow the Exim user and
11411 group, PAM can then be used from an Exim authenticator.
11412
11413
11414 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
11415 .cindex "&'pwcheck'& daemon"
11416 .cindex "Cyrus"
11417 .cindex "expansion" "&'pwcheck'& authentication test"
11418 .cindex "&%pwcheck%& expansion condition"
11419 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
11420 This is one way of making it possible for passwords to be checked by a process
11421 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
11422 deprecated. Its replacement is &'saslauthd'& (see below).
11423
11424 The pwcheck support is not included in Exim by default. You need to specify
11425 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
11426 building Exim. For example:
11427 .code
11428 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
11429 .endd
11430 You do not need to install the full Cyrus software suite in order to use
11431 the pwcheck daemon. You can compile and install just the daemon alone
11432 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
11433 access to the &_/var/pwcheck_& directory.
11434
11435 The &%pwcheck%& condition takes one argument, which must be the user name and
11436 password, separated by a colon. For example, in a LOGIN authenticator
11437 configuration, you might have this:
11438 .code
11439 server_condition = ${if pwcheck{$auth1:$auth2}}
11440 .endd
11441 Again, for a PLAIN authenticator configuration, this would be:
11442 .code
11443 server_condition = ${if pwcheck{$auth2:$auth3}}
11444 .endd
11445 .vitem &*queue_running*&
11446 .cindex "queue runner" "detecting when delivering from"
11447 .cindex "expansion" "queue runner test"
11448 .cindex "&%queue_running%& expansion condition"
11449 This condition, which has no data, is true during delivery attempts that are
11450 initiated by queue runner processes, and false otherwise.
11451
11452
11453 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
11454 .cindex "Radius"
11455 .cindex "expansion" "Radius authentication"
11456 .cindex "&%radius%& expansion condition"
11457 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
11458 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
11459 the Radius client configuration file in order to build Exim with Radius
11460 support.
11461
11462 With just that one setting, Exim expects to be linked with the &%radiusclient%&
11463 library, using the original API. If you are using release 0.4.0 or later of
11464 this library, you need to set
11465 .code
11466 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
11467 .endd
11468 in &_Local/Makefile_& when building Exim. You can also link Exim with the
11469 &%libradius%& library that comes with FreeBSD. To do this, set
11470 .code
11471 RADIUS_LIB_TYPE=RADLIB
11472 .endd
11473 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
11474 You may also have to supply a suitable setting in EXTRALIBS so that the
11475 Radius library can be found when Exim is linked.
11476
11477 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
11478 Radius client library, which calls the Radius server. The condition is true if
11479 the authentication is successful. For example:
11480 .code
11481 server_condition = ${if radius{<arguments>}}
11482 .endd
11483
11484
11485 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
11486 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
11487 .cindex "&'saslauthd'& daemon"
11488 .cindex "Cyrus"
11489 .cindex "expansion" "&'saslauthd'& authentication test"
11490 .cindex "&%saslauthd%& expansion condition"
11491 This condition supports user authentication using the Cyrus &'saslauthd'&
11492 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
11493 Using this daemon is one way of making it possible for passwords to be checked
11494 by a process that is not running as root.
11495
11496 The saslauthd support is not included in Exim by default. You need to specify
11497 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
11498 building Exim. For example:
11499 .code
11500 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
11501 .endd
11502 You do not need to install the full Cyrus software suite in order to use
11503 the saslauthd daemon. You can compile and install just the daemon alone
11504 from the Cyrus SASL library.
11505
11506 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
11507 two are mandatory. For example:
11508 .code
11509 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
11510 .endd
11511 The service and the realm are optional (which is why the arguments are enclosed
11512 in their own set of braces). For details of the meaning of the service and
11513 realm, and how to run the daemon, consult the Cyrus documentation.
11514 .endlist vlist
11515
11516
11517
11518 .section "Combining expansion conditions" "SECID84"
11519 .cindex "expansion" "combining conditions"
11520 Several conditions can be tested at once by combining them using the &%and%&
11521 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
11522 conditions on their own, and precede their lists of sub-conditions. Each
11523 sub-condition must be enclosed in braces within the overall braces that contain
11524 the list. No repetition of &%if%& is used.
11525
11526
11527 .vlist
11528 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
11529 .cindex "&""or""& expansion condition"
11530 .cindex "expansion" "&""or""& of conditions"
11531 The sub-conditions are evaluated from left to right. The condition is true if
11532 any one of the sub-conditions is true.
11533 For example,
11534 .code
11535 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
11536 .endd
11537 When a true sub-condition is found, the following ones are parsed but not
11538 evaluated. If there are several &"match"& sub-conditions the values of the
11539 numeric variables afterwards are taken from the first one that succeeds.
11540
11541 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
11542 .cindex "&""and""& expansion condition"
11543 .cindex "expansion" "&""and""& of conditions"
11544 The sub-conditions are evaluated from left to right. The condition is true if
11545 all of the sub-conditions are true. If there are several &"match"&
11546 sub-conditions, the values of the numeric variables afterwards are taken from
11547 the last one. When a false sub-condition is found, the following ones are
11548 parsed but not evaluated.
11549 .endlist
11550 .ecindex IIDexpcond
11551
11552
11553
11554
11555 .section "Expansion variables" "SECTexpvar"
11556 .cindex "expansion" "variables, list of"
11557 This section contains an alphabetical list of all the expansion variables. Some
11558 of them are available only when Exim is compiled with specific options such as
11559 support for TLS or the content scanning extension.
11560
11561 .vlist
11562 .vitem "&$0$&, &$1$&, etc"
11563 .cindex "numerical variables (&$1$& &$2$& etc)"
11564 When a &%match%& expansion condition succeeds, these variables contain the
11565 captured substrings identified by the regular expression during subsequent
11566 processing of the success string of the containing &%if%& expansion item.
11567 In the expansion condition case
11568 they do not retain their values afterwards; in fact, their previous
11569 values are restored at the end of processing an &%if%& item. The numerical
11570 variables may also be set externally by some other matching process which
11571 precedes the expansion of the string. For example, the commands available in
11572 Exim filter files include an &%if%& command with its own regular expression
11573 matching condition.
11574
11575 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
11576 Within an acl condition, expansion condition or expansion item
11577 any arguments are copied to these variables,
11578 any unused variables being made empty.
11579
11580 .vitem "&$acl_c...$&"
11581 Values can be placed in these variables by the &%set%& modifier in an ACL. They
11582 can be given any name that starts with &$acl_c$& and is at least six characters
11583 long, but the sixth character must be either a digit or an underscore. For
11584 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
11585 variables persist throughout the lifetime of an SMTP connection. They can be
11586 used to pass information between ACLs and between different invocations of the
11587 same ACL. When a message is received, the values of these variables are saved
11588 with the message, and can be accessed by filters, routers, and transports
11589 during subsequent delivery.
11590
11591 .vitem "&$acl_m...$&"
11592 These variables are like the &$acl_c...$& variables, except that their values
11593 are reset after a message has been received. Thus, if several messages are
11594 received in one SMTP connection, &$acl_m...$& values are not passed on from one
11595 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
11596 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
11597 message is received, the values of these variables are saved with the message,
11598 and can be accessed by filters, routers, and transports during subsequent
11599 delivery.
11600
11601 .vitem &$acl_narg$&
11602 Within an acl condition, expansion condition or expansion item
11603 this variable has the number of arguments.
11604
11605 .vitem &$acl_verify_message$&
11606 .vindex "&$acl_verify_message$&"
11607 After an address verification has failed, this variable contains the failure
11608 message. It retains its value for use in subsequent modifiers. The message can
11609 be preserved by coding like this:
11610 .code
11611 warn !verify = sender
11612 set acl_m0 = $acl_verify_message
11613 .endd
11614 You can use &$acl_verify_message$& during the expansion of the &%message%& or
11615 &%log_message%& modifiers, to include information about the verification
11616 failure.
11617
11618 .vitem &$address_data$&
11619 .vindex "&$address_data$&"
11620 This variable is set by means of the &%address_data%& option in routers. The
11621 value then remains with the address while it is processed by subsequent routers
11622 and eventually a transport. If the transport is handling multiple addresses,
11623 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
11624 for more details. &*Note*&: The contents of &$address_data$& are visible in
11625 user filter files.
11626
11627 If &$address_data$& is set when the routers are called from an ACL to verify
11628 a recipient address, the final value is still in the variable for subsequent
11629 conditions and modifiers of the ACL statement. If routing the address caused it
11630 to be redirected to just one address, the child address is also routed as part
11631 of the verification, and in this case the final value of &$address_data$& is
11632 from the child's routing.
11633
11634 If &$address_data$& is set when the routers are called from an ACL to verify a
11635 sender address, the final value is also preserved, but this time in
11636 &$sender_address_data$&, to distinguish it from data from a recipient
11637 address.
11638
11639 In both cases (recipient and sender verification), the value does not persist
11640 after the end of the current ACL statement. If you want to preserve
11641 these values for longer, you can save them in ACL variables.
11642
11643 .vitem &$address_file$&
11644 .vindex "&$address_file$&"
11645 When, as a result of aliasing, forwarding, or filtering, a message is directed
11646 to a specific file, this variable holds the name of the file when the transport
11647 is running. At other times, the variable is empty. For example, using the
11648 default configuration, if user &%r2d2%& has a &_.forward_& file containing
11649 .code
11650 /home/r2d2/savemail
11651 .endd
11652 then when the &(address_file)& transport is running, &$address_file$&
11653 contains the text string &`/home/r2d2/savemail`&.
11654 .cindex "Sieve filter" "value of &$address_file$&"
11655 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
11656 then up to the transport configuration to generate an appropriate absolute path
11657 to the relevant file.
11658
11659 .vitem &$address_pipe$&
11660 .vindex "&$address_pipe$&"
11661 When, as a result of aliasing or forwarding, a message is directed to a pipe,
11662 this variable holds the pipe command when the transport is running.
11663
11664 .vitem "&$auth1$& &-- &$auth3$&"
11665 .vindex "&$auth1$&, &$auth2$&, etc"
11666 These variables are used in SMTP authenticators (see chapters
11667 &<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
11668
11669 .vitem &$authenticated_id$&
11670 .cindex "authentication" "id"
11671 .vindex "&$authenticated_id$&"
11672 When a server successfully authenticates a client it may be configured to
11673 preserve some of the authentication information in the variable
11674 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
11675 user/password authenticator configuration might preserve the user name for use
11676 in the routers. Note that this is not the same information that is saved in
11677 &$sender_host_authenticated$&.
11678
11679 When a message is submitted locally (that is, not over a TCP connection)
11680 the value of &$authenticated_id$& is normally the login name of the calling
11681 process. However, a trusted user can override this by means of the &%-oMai%&
11682 command line option.
11683 This second case also sets up inforamtion used by the
11684 &$authresults$& expansion item.
11685
11686 .vitem &$authenticated_fail_id$&
11687 .cindex "authentication" "fail" "id"
11688 .vindex "&$authenticated_fail_id$&"
11689 When an authentication attempt fails, the variable &$authenticated_fail_id$&
11690 will contain the failed authentication id. If more than one authentication
11691 id is attempted, it will contain only the last one. The variable is
11692 available for processing in the ACL's, generally the quit or notquit ACL.
11693 A message to a local recipient could still be accepted without requiring
11694 authentication, which means this variable could also be visible in all of
11695 the ACL's as well.
11696
11697
11698 .vitem &$authenticated_sender$&
11699 .cindex "sender" "authenticated"
11700 .cindex "authentication" "sender"
11701 .cindex "AUTH" "on MAIL command"
11702 .vindex "&$authenticated_sender$&"
11703 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
11704 SMTP MAIL command if it believes the sender is sufficiently trusted, as
11705 described in section &<<SECTauthparamail>>&. Unless the data is the string
11706 &"<>"&, it is set as the authenticated sender of the message, and the value is
11707 available during delivery in the &$authenticated_sender$& variable. If the
11708 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
11709
11710 .vindex "&$qualify_domain$&"
11711 When a message is submitted locally (that is, not over a TCP connection), the
11712 value of &$authenticated_sender$& is an address constructed from the login
11713 name of the calling process and &$qualify_domain$&, except that a trusted user
11714 can override this by means of the &%-oMas%& command line option.
11715
11716
11717 .vitem &$authentication_failed$&
11718 .cindex "authentication" "failure"
11719 .vindex "&$authentication_failed$&"
11720 This variable is set to &"1"& in an Exim server if a client issues an AUTH
11721 command that does not succeed. Otherwise it is set to &"0"&. This makes it
11722 possible to distinguish between &"did not try to authenticate"&
11723 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
11724 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
11725 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
11726 negative response to an AUTH command, including (for example) an attempt to use
11727 an undefined mechanism.
11728
11729 .vitem &$av_failed$&
11730 .cindex "content scanning" "AV scanner failure"
11731 This variable is available when Exim is compiled with the content-scanning
11732 extension. It is set to &"0"& by default, but will be set to &"1"& if any
11733 problem occurs with the virus scanner (specified by &%av_scanner%&) during
11734 the ACL malware condition.
11735
11736 .vitem &$body_linecount$&
11737 .cindex "message body" "line count"
11738 .cindex "body of message" "line count"
11739 .vindex "&$body_linecount$&"
11740 When a message is being received or delivered, this variable contains the
11741 number of lines in the message's body. See also &$message_linecount$&.
11742
11743 .vitem &$body_zerocount$&
11744 .cindex "message body" "binary zero count"
11745 .cindex "body of message" "binary zero count"
11746 .cindex "binary zero" "in message body"
11747 .vindex "&$body_zerocount$&"
11748 When a message is being received or delivered, this variable contains the
11749 number of binary zero bytes (ASCII NULs) in the message's body.
11750
11751 .vitem &$bounce_recipient$&
11752 .vindex "&$bounce_recipient$&"
11753 This is set to the recipient address of a bounce message while Exim is creating
11754 it. It is useful if a customized bounce message text file is in use (see
11755 chapter &<<CHAPemsgcust>>&).
11756
11757 .vitem &$bounce_return_size_limit$&
11758 .vindex "&$bounce_return_size_limit$&"
11759 This contains the value set in the &%bounce_return_size_limit%& option, rounded
11760 up to a multiple of 1000. It is useful when a customized error message text
11761 file is in use (see chapter &<<CHAPemsgcust>>&).
11762
11763 .vitem &$caller_gid$&
11764 .cindex "gid (group id)" "caller"
11765 .vindex "&$caller_gid$&"
11766 The real group id under which the process that called Exim was running. This is
11767 not the same as the group id of the originator of a message (see
11768 &$originator_gid$&). If Exim re-execs itself, this variable in the new
11769 incarnation normally contains the Exim gid.
11770
11771 .vitem &$caller_uid$&
11772 .cindex "uid (user id)" "caller"
11773 .vindex "&$caller_uid$&"
11774 The real user id under which the process that called Exim was running. This is
11775 not the same as the user id of the originator of a message (see
11776 &$originator_uid$&). If Exim re-execs itself, this variable in the new
11777 incarnation normally contains the Exim uid.
11778
11779 .vitem &$callout_address$&
11780 .vindex "&$callout_address$&"
11781 After a callout for verification, spamd or malware daemon service, the
11782 address that was connected to.
11783
11784 .vitem &$compile_number$&
11785 .vindex "&$compile_number$&"
11786 The building process for Exim keeps a count of the number
11787 of times it has been compiled. This serves to distinguish different
11788 compilations of the same version of the program.
11789
11790 .vitem &$config_dir$&
11791 .vindex "&$config_dir$&"
11792 The directory name of the main configuration file. That is, the content of
11793 &$config_file$& with the last component stripped. The value does not
11794 contain the trailing slash. If &$config_file$& does not contain a slash,
11795 &$config_dir$& is ".".
11796
11797 .vitem &$config_file$&
11798 .vindex "&$config_file$&"
11799 The name of the main configuration file Exim is using.
11800
11801 .vitem &$dkim_verify_status$&
11802 Results of DKIM verification.
11803 For details see section &<<SECDKIMVFY>>&.
11804
11805 .vitem &$dkim_cur_signer$& &&&
11806 &$dkim_verify_reason$& &&&
11807 &$dkim_domain$& &&&
11808 &$dkim_identity$& &&&
11809 &$dkim_selector$& &&&
11810 &$dkim_algo$& &&&
11811 &$dkim_canon_body$& &&&
11812 &$dkim_canon_headers$& &&&
11813 &$dkim_copiedheaders$& &&&
11814 &$dkim_bodylength$& &&&
11815 &$dkim_created$& &&&
11816 &$dkim_expires$& &&&
11817 &$dkim_headernames$& &&&
11818 &$dkim_key_testing$& &&&
11819 &$dkim_key_nosubdomains$& &&&
11820 &$dkim_key_srvtype$& &&&
11821 &$dkim_key_granularity$& &&&
11822 &$dkim_key_notes$& &&&
11823 &$dkim_key_length$&
11824 These variables are only available within the DKIM ACL.
11825 For details see section &<<SECDKIMVFY>>&.
11826
11827 .vitem &$dkim_signers$&
11828 .vindex &$dkim_signers$&
11829 When a message has been received this variable contains
11830 a colon-separated list of signer domains and identities for the message.
11831 For details see section &<<SECDKIMVFY>>&.
11832
11833 .vitem &$dnslist_domain$& &&&
11834 &$dnslist_matched$& &&&
11835 &$dnslist_text$& &&&
11836 &$dnslist_value$&
11837 .vindex "&$dnslist_domain$&"
11838 .vindex "&$dnslist_matched$&"
11839 .vindex "&$dnslist_text$&"
11840 .vindex "&$dnslist_value$&"
11841 .cindex "black list (DNS)"
11842 When a DNS (black) list lookup succeeds, these variables are set to contain
11843 the following data from the lookup: the list's domain name, the key that was
11844 looked up, the contents of any associated TXT record, and the value from the
11845 main A record. See section &<<SECID204>>& for more details.
11846
11847 .vitem &$domain$&
11848 .vindex "&$domain$&"
11849 When an address is being routed, or delivered on its own, this variable
11850 contains the domain. Uppercase letters in the domain are converted into lower
11851 case for &$domain$&.
11852
11853 Global address rewriting happens when a message is received, so the value of
11854 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
11855 is set during user filtering, but not during system filtering, because a
11856 message may have many recipients and the system filter is called just once.
11857
11858 When more than one address is being delivered at once (for example, several
11859 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
11860 have the same domain. Transports can be restricted to handling only one domain
11861 at a time if the value of &$domain$& is required at transport time &-- this is
11862 the default for local transports. For further details of the environment in
11863 which local transports are run, see chapter &<<CHAPenvironment>>&.
11864
11865 .oindex "&%delay_warning_condition%&"
11866 At the end of a delivery, if all deferred addresses have the same domain, it is
11867 set in &$domain$& during the expansion of &%delay_warning_condition%&.
11868
11869 The &$domain$& variable is also used in some other circumstances:
11870
11871 .ilist
11872 When an ACL is running for a RCPT command, &$domain$& contains the domain of
11873 the recipient address. The domain of the &'sender'& address is in
11874 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
11875 normally set during the running of the MAIL ACL. However, if the sender address
11876 is verified with a callout during the MAIL ACL, the sender domain is placed in
11877 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
11878 the &(smtp)& transport.
11879
11880 .next
11881 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
11882 &$domain$& contains the domain portion of the address that is being rewritten;
11883 it can be used in the expansion of the replacement address, for example, to
11884 rewrite domains by file lookup.
11885
11886 .next
11887 With one important exception, whenever a domain list is being scanned,
11888 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
11889 a &%sender_domains%& condition in an ACL is being processed, the subject domain
11890 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
11891 that, in a RCPT ACL, the sender domain list can be dependent on the
11892 recipient domain (which is what is in &$domain$& at this time).
11893
11894 .next
11895 .cindex "ETRN" "value of &$domain$&"
11896 .oindex "&%smtp_etrn_command%&"
11897 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
11898 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
11899 .endlist
11900
11901
11902 .vitem &$domain_data$&
11903 .vindex "&$domain_data$&"
11904 When the &%domains%& option on a router matches a domain by
11905 means of a lookup, the data read by the lookup is available during the running
11906 of the router as &$domain_data$&. In addition, if the driver routes the
11907 address to a transport, the value is available in that transport. If the
11908 transport is handling multiple addresses, the value from the first address is
11909 used.
11910
11911 &$domain_data$& is also set when the &%domains%& condition in an ACL matches a
11912 domain by means of a lookup. The data read by the lookup is available during
11913 the rest of the ACL statement. In all other situations, this variable expands
11914 to nothing.
11915
11916 .vitem &$exim_gid$&
11917 .vindex "&$exim_gid$&"
11918 This variable contains the numerical value of the Exim group id.
11919
11920 .vitem &$exim_path$&
11921 .vindex "&$exim_path$&"
11922 This variable contains the path to the Exim binary.
11923
11924 .vitem &$exim_uid$&
11925 .vindex "&$exim_uid$&"
11926 This variable contains the numerical value of the Exim user id.
11927
11928 .vitem &$exim_version$&
11929 .vindex "&$exim_version$&"
11930 This variable contains the version string of the Exim build.
11931 The first character is a major version number, currently 4.
11932 Then after a dot, the next group of digits is a minor version number.
11933 There may be other characters following the minor version.
11934
11935 .vitem &$header_$&<&'name'&>
11936 This is not strictly an expansion variable. It is expansion syntax for
11937 inserting the message header line with the given name. Note that the name must
11938 be terminated by colon or white space, because it may contain a wide variety of
11939 characters. Note also that braces must &'not'& be used.
11940
11941 .vitem &$headers_added$&
11942 .vindex "&$headers_added$&"
11943 Within an ACL this variable contains the headers added so far by
11944 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
11945 The headers are a newline-separated list.
11946
11947 .vitem &$home$&
11948 .vindex "&$home$&"
11949 When the &%check_local_user%& option is set for a router, the user's home
11950 directory is placed in &$home$& when the check succeeds. In particular, this
11951 means it is set during the running of users' filter files. A router may also
11952 explicitly set a home directory for use by a transport; this can be overridden
11953 by a setting on the transport itself.
11954
11955 When running a filter test via the &%-bf%& option, &$home$& is set to the value
11956 of the environment variable HOME, which is subject to the
11957 &%keep_environment%& and &%add_environment%& main config options.
11958
11959 .vitem &$host$&
11960 .vindex "&$host$&"
11961 If a router assigns an address to a transport (any transport), and passes a
11962 list of hosts with the address, the value of &$host$& when the transport starts
11963 to run is the name of the first host on the list. Note that this applies both
11964 to local and remote transports.
11965
11966 .cindex "transport" "filter"
11967 .cindex "filter" "transport filter"
11968 For the &(smtp)& transport, if there is more than one host, the value of
11969 &$host$& changes as the transport works its way through the list. In
11970 particular, when the &(smtp)& transport is expanding its options for encryption
11971 using TLS, or for specifying a transport filter (see chapter
11972 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
11973 is connected.
11974
11975 When used in the client part of an authenticator configuration (see chapter
11976 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
11977 client is connected.
11978
11979
11980 .vitem &$host_address$&
11981 .vindex "&$host_address$&"
11982 This variable is set to the remote host's IP address whenever &$host$& is set
11983 for a remote connection. It is also set to the IP address that is being checked
11984 when the &%ignore_target_hosts%& option is being processed.
11985
11986 .vitem &$host_data$&
11987 .vindex "&$host_data$&"
11988 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
11989 result of the lookup is made available in the &$host_data$& variable. This
11990 allows you, for example, to do things like this:
11991 .code
11992 deny hosts = net-lsearch;/some/file
11993 message = $host_data
11994 .endd
11995 .vitem &$host_lookup_deferred$&
11996 .cindex "host name" "lookup, failure of"
11997 .vindex "&$host_lookup_deferred$&"
11998 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
11999 message comes from a remote host and there is an attempt to look up the host's
12000 name from its IP address, and the attempt is not successful, one of these
12001 variables is set to &"1"&.
12002
12003 .ilist
12004 If the lookup receives a definite negative response (for example, a DNS lookup
12005 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
12006
12007 .next
12008 If there is any kind of problem during the lookup, such that Exim cannot
12009 tell whether or not the host name is defined (for example, a timeout for a DNS
12010 lookup), &$host_lookup_deferred$& is set to &"1"&.
12011 .endlist ilist
12012
12013 Looking up a host's name from its IP address consists of more than just a
12014 single reverse lookup. Exim checks that a forward lookup of at least one of the
12015 names it receives from a reverse lookup yields the original IP address. If this
12016 is not the case, Exim does not accept the looked up name(s), and
12017 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
12018 IP address (for example, the existence of a PTR record in the DNS) is not
12019 sufficient on its own for the success of a host name lookup. If the reverse
12020 lookup succeeds, but there is a lookup problem such as a timeout when checking
12021 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
12022 &"1"&. See also &$sender_host_name$&.
12023
12024 .cindex authentication "expansion item"
12025 Performing these checks sets up information used by the
12026 &$authresults$& expansion item.
12027
12028
12029 .vitem &$host_lookup_failed$&
12030 .vindex "&$host_lookup_failed$&"
12031 See &$host_lookup_deferred$&.
12032
12033 .vitem &$host_port$&
12034 .vindex "&$host_port$&"
12035 This variable is set to the remote host's TCP port whenever &$host$& is set
12036 for an outbound connection.
12037
12038 .vitem &$initial_cwd$&
12039 .vindex "&$initial_cwd$&
12040 This variable contains the full path name of the initial working
12041 directory of the current Exim process. This may differ from the current
12042 working directory, as Exim changes this to "/" during early startup, and
12043 to &$spool_directory$& later.
12044
12045 .vitem &$inode$&
12046 .vindex "&$inode$&"
12047 The only time this variable is set is while expanding the &%directory_file%&
12048 option in the &(appendfile)& transport. The variable contains the inode number
12049 of the temporary file which is about to be renamed. It can be used to construct
12050 a unique name for the file.
12051
12052 .vitem &$interface_address$&
12053 .vindex "&$interface_address$&"
12054 This is an obsolete name for &$received_ip_address$&.
12055
12056 .vitem &$interface_port$&
12057 .vindex "&$interface_port$&"
12058 This is an obsolete name for &$received_port$&.
12059
12060 .vitem &$item$&
12061 .vindex "&$item$&"
12062 This variable is used during the expansion of &*forall*& and &*forany*&
12063 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
12064 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
12065 empty.
12066
12067 .vitem &$ldap_dn$&
12068 .vindex "&$ldap_dn$&"
12069 This variable, which is available only when Exim is compiled with LDAP support,
12070 contains the DN from the last entry in the most recently successful LDAP
12071 lookup.
12072
12073 .vitem &$load_average$&
12074 .vindex "&$load_average$&"
12075 This variable contains the system load average, multiplied by 1000 so that it
12076 is an integer. For example, if the load average is 0.21, the value of the
12077 variable is 210. The value is recomputed every time the variable is referenced.
12078
12079 .vitem &$local_part$&
12080 .vindex "&$local_part$&"
12081 When an address is being routed, or delivered on its own, this
12082 variable contains the local part. When a number of addresses are being
12083 delivered together (for example, multiple RCPT commands in an SMTP
12084 session), &$local_part$& is not set.
12085
12086 Global address rewriting happens when a message is received, so the value of
12087 &$local_part$& during routing and delivery is the value after rewriting.
12088 &$local_part$& is set during user filtering, but not during system filtering,
12089 because a message may have many recipients and the system filter is called just
12090 once.
12091
12092 .vindex "&$local_part_prefix$&"
12093 .vindex "&$local_part_suffix$&"
12094 If a local part prefix or suffix has been recognized, it is not included in the
12095 value of &$local_part$& during routing and subsequent delivery. The values of
12096 any prefix or suffix are in &$local_part_prefix$& and
12097 &$local_part_suffix$&, respectively.
12098
12099 When a message is being delivered to a file, pipe, or autoreply transport as a
12100 result of aliasing or forwarding, &$local_part$& is set to the local part of
12101 the parent address, not to the file name or command (see &$address_file$& and
12102 &$address_pipe$&).
12103
12104 When an ACL is running for a RCPT command, &$local_part$& contains the
12105 local part of the recipient address.
12106
12107 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12108 &$local_part$& contains the local part of the address that is being rewritten;
12109 it can be used in the expansion of the replacement address, for example.
12110
12111 In all cases, all quoting is removed from the local part. For example, for both
12112 the addresses
12113 .code
12114 "abc:xyz"@test.example
12115 abc\:xyz@test.example
12116 .endd
12117 the value of &$local_part$& is
12118 .code
12119 abc:xyz
12120 .endd
12121 If you use &$local_part$& to create another address, you should always wrap it
12122 inside a quoting operator. For example, in a &(redirect)& router you could
12123 have:
12124 .code
12125 data = ${quote_local_part:$local_part}@new.domain.example
12126 .endd
12127 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
12128 to process local parts in a case-dependent manner in a router, you can set the
12129 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
12130
12131 .vitem &$local_part_data$&
12132 .vindex "&$local_part_data$&"
12133 When the &%local_parts%& option on a router matches a local part by means of a
12134 lookup, the data read by the lookup is available during the running of the
12135 router as &$local_part_data$&. In addition, if the driver routes the address
12136 to a transport, the value is available in that transport. If the transport is
12137 handling multiple addresses, the value from the first address is used.
12138
12139 &$local_part_data$& is also set when the &%local_parts%& condition in an ACL
12140 matches a local part by means of a lookup. The data read by the lookup is
12141 available during the rest of the ACL statement. In all other situations, this
12142 variable expands to nothing.
12143
12144 .vitem &$local_part_prefix$&
12145 .vindex "&$local_part_prefix$&"
12146 When an address is being routed or delivered, and a
12147 specific prefix for the local part was recognized, it is available in this
12148 variable, having been removed from &$local_part$&.
12149
12150 .vitem &$local_part_suffix$&
12151 .vindex "&$local_part_suffix$&"
12152 When an address is being routed or delivered, and a
12153 specific suffix for the local part was recognized, it is available in this
12154 variable, having been removed from &$local_part$&.
12155
12156 .vitem &$local_scan_data$&
12157 .vindex "&$local_scan_data$&"
12158 This variable contains the text returned by the &[local_scan()]& function when
12159 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
12160
12161 .vitem &$local_user_gid$&
12162 .vindex "&$local_user_gid$&"
12163 See &$local_user_uid$&.
12164
12165 .vitem &$local_user_uid$&
12166 .vindex "&$local_user_uid$&"
12167 This variable and &$local_user_gid$& are set to the uid and gid after the
12168 &%check_local_user%& router precondition succeeds. This means that their values
12169 are available for the remaining preconditions (&%senders%&, &%require_files%&,
12170 and &%condition%&), for the &%address_data%& expansion, and for any
12171 router-specific expansions. At all other times, the values in these variables
12172 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
12173
12174 .vitem &$localhost_number$&
12175 .vindex "&$localhost_number$&"
12176 This contains the expanded value of the
12177 &%localhost_number%& option. The expansion happens after the main options have
12178 been read.
12179
12180 .vitem &$log_inodes$&
12181 .vindex "&$log_inodes$&"
12182 The number of free inodes in the disk partition where Exim's
12183 log files are being written. The value is recalculated whenever the variable is
12184 referenced. If the relevant file system does not have the concept of inodes,
12185 the value of is -1. See also the &%check_log_inodes%& option.
12186
12187 .vitem &$log_space$&
12188 .vindex "&$log_space$&"
12189 The amount of free space (as a number of kilobytes) in the disk
12190 partition where Exim's log files are being written. The value is recalculated
12191 whenever the variable is referenced. If the operating system does not have the
12192 ability to find the amount of free space (only true for experimental systems),
12193 the space value is -1. See also the &%check_log_space%& option.
12194
12195
12196 .vitem &$lookup_dnssec_authenticated$&
12197 .vindex "&$lookup_dnssec_authenticated$&"
12198 This variable is set after a DNS lookup done by
12199 a dnsdb lookup expansion, dnslookup router or smtp transport.
12200 .cindex "DNS" "DNSSEC"
12201 It will be empty if &(DNSSEC)& was not requested,
12202 &"no"& if the result was not labelled as authenticated data
12203 and &"yes"& if it was.
12204 Results that are labelled as authoritative answer that match
12205 the &%dns_trust_aa%& configuration variable count also
12206 as authenticated data.
12207
12208 .vitem &$mailstore_basename$&
12209 .vindex "&$mailstore_basename$&"
12210 This variable is set only when doing deliveries in &"mailstore"& format in the
12211 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
12212 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
12213 contains the basename of the files that are being written, that is, the name
12214 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
12215 variable is empty.
12216
12217 .vitem &$malware_name$&
12218 .vindex "&$malware_name$&"
12219 This variable is available when Exim is compiled with the
12220 content-scanning extension. It is set to the name of the virus that was found
12221 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
12222
12223 .vitem &$max_received_linelength$&
12224 .vindex "&$max_received_linelength$&"
12225 .cindex "maximum" "line length"
12226 .cindex "line length" "maximum"
12227 This variable contains the number of bytes in the longest line that was
12228 received as part of the message, not counting the line termination
12229 character(s).
12230 It is not valid if the &%spool_files_wireformat%& option is used.
12231
12232 .vitem &$message_age$&
12233 .cindex "message" "age of"
12234 .vindex "&$message_age$&"
12235 This variable is set at the start of a delivery attempt to contain the number
12236 of seconds since the message was received. It does not change during a single
12237 delivery attempt.
12238
12239 .vitem &$message_body$&
12240 .cindex "body of message" "expansion variable"
12241 .cindex "message body" "in expansion"
12242 .cindex "binary zero" "in message body"
12243 .vindex "&$message_body$&"
12244 .oindex "&%message_body_visible%&"
12245 This variable contains the initial portion of a message's body while it is
12246 being delivered, and is intended mainly for use in filter files. The maximum
12247 number of characters of the body that are put into the variable is set by the
12248 &%message_body_visible%& configuration option; the default is 500.
12249
12250 .oindex "&%message_body_newlines%&"
12251 By default, newlines are converted into spaces in &$message_body$&, to make it
12252 easier to search for phrases that might be split over a line break. However,
12253 this can be disabled by setting &%message_body_newlines%& to be true. Binary
12254 zeros are always converted into spaces.
12255
12256 .vitem &$message_body_end$&
12257 .cindex "body of message" "expansion variable"
12258 .cindex "message body" "in expansion"
12259 .vindex "&$message_body_end$&"
12260 This variable contains the final portion of a message's
12261 body while it is being delivered. The format and maximum size are as for
12262 &$message_body$&.
12263
12264 .vitem &$message_body_size$&
12265 .cindex "body of message" "size"
12266 .cindex "message body" "size"
12267 .vindex "&$message_body_size$&"
12268 When a message is being delivered, this variable contains the size of the body
12269 in bytes. The count starts from the character after the blank line that
12270 separates the body from the header. Newlines are included in the count. See
12271 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
12272
12273 If the spool file is wireformat
12274 (see the &%spool_files_wireformat%& main option)
12275 the CRLF line-terminators are included in the count.
12276
12277 .vitem &$message_exim_id$&
12278 .vindex "&$message_exim_id$&"
12279 When a message is being received or delivered, this variable contains the
12280 unique message id that is generated and used by Exim to identify the message.
12281 An id is not created for a message until after its header has been successfully
12282 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
12283 line; it is the local id that Exim assigns to the message, for example:
12284 &`1BXTIK-0001yO-VA`&.
12285
12286 .vitem &$message_headers$&
12287 .vindex &$message_headers$&
12288 This variable contains a concatenation of all the header lines when a message
12289 is being processed, except for lines added by routers or transports. The header
12290 lines are separated by newline characters. Their contents are decoded in the
12291 same way as a header line that is inserted by &%bheader%&.
12292
12293 .vitem &$message_headers_raw$&
12294 .vindex &$message_headers_raw$&
12295 This variable is like &$message_headers$& except that no processing of the
12296 contents of header lines is done.
12297
12298 .vitem &$message_id$&
12299 This is an old name for &$message_exim_id$&. It is now deprecated.
12300
12301 .vitem &$message_linecount$&
12302 .vindex "&$message_linecount$&"
12303 This variable contains the total number of lines in the header and body of the
12304 message. Compare &$body_linecount$&, which is the count for the body only.
12305 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
12306 number of lines received. Before delivery happens (that is, before filters,
12307 routers, and transports run) the count is increased to include the
12308 &'Received:'& header line that Exim standardly adds, and also any other header
12309 lines that are added by ACLs. The blank line that separates the message header
12310 from the body is not counted.
12311
12312 As with the special case of &$message_size$&, during the expansion of the
12313 appendfile transport's maildir_tag option in maildir format, the value of
12314 &$message_linecount$& is the precise size of the number of newlines in the
12315 file that has been written (minus one for the blank line between the
12316 header and the body).
12317
12318 Here is an example of the use of this variable in a DATA ACL:
12319 .code
12320 deny message = Too many lines in message header
12321 condition = \
12322 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
12323 .endd
12324 In the MAIL and RCPT ACLs, the value is zero because at that stage the
12325 message has not yet been received.
12326
12327 This variable is not valid if the &%spool_files_wireformat%& option is used.
12328
12329 .vitem &$message_size$&
12330 .cindex "size" "of message"
12331 .cindex "message" "size"
12332 .vindex "&$message_size$&"
12333 When a message is being processed, this variable contains its size in bytes. In
12334 most cases, the size includes those headers that were received with the
12335 message, but not those (such as &'Envelope-to:'&) that are added to individual
12336 deliveries as they are written. However, there is one special case: during the
12337 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
12338 doing a delivery in maildir format, the value of &$message_size$& is the
12339 precise size of the file that has been written. See also
12340 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
12341
12342 .cindex "RCPT" "value of &$message_size$&"
12343 While running a per message ACL (mail/rcpt/predata), &$message_size$&
12344 contains the size supplied on the MAIL command, or -1 if no size was given. The
12345 value may not, of course, be truthful.
12346
12347 .vitem &$mime_$&&'xxx'&
12348 A number of variables whose names start with &$mime$& are
12349 available when Exim is compiled with the content-scanning extension. For
12350 details, see section &<<SECTscanmimepart>>&.
12351
12352 .vitem "&$n0$& &-- &$n9$&"
12353 These variables are counters that can be incremented by means
12354 of the &%add%& command in filter files.
12355
12356 .vitem &$original_domain$&
12357 .vindex "&$domain$&"
12358 .vindex "&$original_domain$&"
12359 When a top-level address is being processed for delivery, this contains the
12360 same value as &$domain$&. However, if a &"child"& address (for example,
12361 generated by an alias, forward, or filter file) is being processed, this
12362 variable contains the domain of the original address (lower cased). This
12363 differs from &$parent_domain$& only when there is more than one level of
12364 aliasing or forwarding. When more than one address is being delivered in a
12365 single transport run, &$original_domain$& is not set.
12366
12367 If a new address is created by means of a &%deliver%& command in a system
12368 filter, it is set up with an artificial &"parent"& address. This has the local
12369 part &'system-filter'& and the default qualify domain.
12370
12371 .vitem &$original_local_part$&
12372 .vindex "&$local_part$&"
12373 .vindex "&$original_local_part$&"
12374 When a top-level address is being processed for delivery, this contains the
12375 same value as &$local_part$&, unless a prefix or suffix was removed from the
12376 local part, because &$original_local_part$& always contains the full local
12377 part. When a &"child"& address (for example, generated by an alias, forward, or
12378 filter file) is being processed, this variable contains the full local part of
12379 the original address.
12380
12381 If the router that did the redirection processed the local part
12382 case-insensitively, the value in &$original_local_part$& is in lower case.
12383 This variable differs from &$parent_local_part$& only when there is more than
12384 one level of aliasing or forwarding. When more than one address is being
12385 delivered in a single transport run, &$original_local_part$& is not set.
12386
12387 If a new address is created by means of a &%deliver%& command in a system
12388 filter, it is set up with an artificial &"parent"& address. This has the local
12389 part &'system-filter'& and the default qualify domain.
12390
12391 .vitem &$originator_gid$&
12392 .cindex "gid (group id)" "of originating user"
12393 .cindex "sender" "gid"
12394 .vindex "&$caller_gid$&"
12395 .vindex "&$originator_gid$&"
12396 This variable contains the value of &$caller_gid$& that was set when the
12397 message was received. For messages received via the command line, this is the
12398 gid of the sending user. For messages received by SMTP over TCP/IP, this is
12399 normally the gid of the Exim user.
12400
12401 .vitem &$originator_uid$&
12402 .cindex "uid (user id)" "of originating user"
12403 .cindex "sender" "uid"
12404 .vindex "&$caller_uid$&"
12405 .vindex "&$originator_uid$&"
12406 The value of &$caller_uid$& that was set when the message was received. For
12407 messages received via the command line, this is the uid of the sending user.
12408 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
12409 user.
12410
12411 .vitem &$parent_domain$&
12412 .vindex "&$parent_domain$&"
12413 This variable is similar to &$original_domain$& (see
12414 above), except that it refers to the immediately preceding parent address.
12415
12416 .vitem &$parent_local_part$&
12417 .vindex "&$parent_local_part$&"
12418 This variable is similar to &$original_local_part$&
12419 (see above), except that it refers to the immediately preceding parent address.
12420
12421 .vitem &$pid$&
12422 .cindex "pid (process id)" "of current process"
12423 .vindex "&$pid$&"
12424 This variable contains the current process id.
12425
12426 .vitem &$pipe_addresses$&
12427 .cindex "filter" "transport filter"
12428 .cindex "transport" "filter"
12429 .vindex "&$pipe_addresses$&"
12430 This is not an expansion variable, but is mentioned here because the string
12431 &`$pipe_addresses`& is handled specially in the command specification for the
12432 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
12433 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
12434 It cannot be used in general expansion strings, and provokes an &"unknown
12435 variable"& error if encountered.
12436
12437 .vitem &$primary_hostname$&
12438 .vindex "&$primary_hostname$&"
12439 This variable contains the value set by &%primary_hostname%& in the
12440 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
12441 a single-component name, Exim calls &[gethostbyname()]& (or
12442 &[getipnodebyname()]& where available) in an attempt to acquire a fully
12443 qualified host name. See also &$smtp_active_hostname$&.
12444
12445
12446 .vitem &$proxy_external_address$& &&&
12447 &$proxy_external_port$& &&&
12448 &$proxy_local_address$& &&&
12449 &$proxy_local_port$& &&&
12450 &$proxy_session$&
12451 These variables are only available when built with Proxy Protocol
12452 or SOCKS5 support.
12453 For details see chapter &<<SECTproxyInbound>>&.
12454
12455 .vitem &$prdr_requested$&
12456 .cindex "PRDR" "variable for"
12457 This variable is set to &"yes"& if PRDR was requested by the client for the
12458 current message, otherwise &"no"&.
12459
12460 .vitem &$prvscheck_address$&
12461 This variable is used in conjunction with the &%prvscheck%& expansion item,
12462 which is described in sections &<<SECTexpansionitems>>& and
12463 &<<SECTverifyPRVS>>&.
12464
12465 .vitem &$prvscheck_keynum$&
12466 This variable is used in conjunction with the &%prvscheck%& expansion item,
12467 which is described in sections &<<SECTexpansionitems>>& and
12468 &<<SECTverifyPRVS>>&.
12469
12470 .vitem &$prvscheck_result$&
12471 This variable is used in conjunction with the &%prvscheck%& expansion item,
12472 which is described in sections &<<SECTexpansionitems>>& and
12473 &<<SECTverifyPRVS>>&.
12474
12475 .vitem &$qualify_domain$&
12476 .vindex "&$qualify_domain$&"
12477 The value set for the &%qualify_domain%& option in the configuration file.
12478
12479 .vitem &$qualify_recipient$&
12480 .vindex "&$qualify_recipient$&"
12481 The value set for the &%qualify_recipient%& option in the configuration file,
12482 or if not set, the value of &$qualify_domain$&.
12483
12484 .vitem &$queue_name$&
12485 .vindex &$queue_name$&
12486 .cindex "named queues"
12487 .cindex queues named
12488 The name of the spool queue in use; empty for the default queue.
12489
12490 .vitem &$rcpt_count$&
12491 .vindex "&$rcpt_count$&"
12492 When a message is being received by SMTP, this variable contains the number of
12493 RCPT commands received for the current message. If this variable is used in a
12494 RCPT ACL, its value includes the current command.
12495
12496 .vitem &$rcpt_defer_count$&
12497 .vindex "&$rcpt_defer_count$&"
12498 .cindex "4&'xx'& responses" "count of"
12499 When a message is being received by SMTP, this variable contains the number of
12500 RCPT commands in the current message that have previously been rejected with a
12501 temporary (4&'xx'&) response.
12502
12503 .vitem &$rcpt_fail_count$&
12504 .vindex "&$rcpt_fail_count$&"
12505 When a message is being received by SMTP, this variable contains the number of
12506 RCPT commands in the current message that have previously been rejected with a
12507 permanent (5&'xx'&) response.
12508
12509 .vitem &$received_count$&
12510 .vindex "&$received_count$&"
12511 This variable contains the number of &'Received:'& header lines in the message,
12512 including the one added by Exim (so its value is always greater than zero). It
12513 is available in the DATA ACL, the non-SMTP ACL, and while routing and
12514 delivering.
12515
12516 .vitem &$received_for$&
12517 .vindex "&$received_for$&"
12518 If there is only a single recipient address in an incoming message, this
12519 variable contains that address when the &'Received:'& header line is being
12520 built. The value is copied after recipient rewriting has happened, but before
12521 the &[local_scan()]& function is run.
12522
12523 .vitem &$received_ip_address$&
12524 .vindex "&$received_ip_address$&"
12525 As soon as an Exim server starts processing an incoming TCP/IP connection, this
12526 variable is set to the address of the local IP interface, and &$received_port$&
12527 is set to the local port number. (The remote IP address and port are in
12528 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
12529 the port value is -1 unless it has been set using the &%-oMi%& command line
12530 option.
12531
12532 As well as being useful in ACLs (including the &"connect"& ACL), these variable
12533 could be used, for example, to make the file name for a TLS certificate depend
12534 on which interface and/or port is being used for the incoming connection. The
12535 values of &$received_ip_address$& and &$received_port$& are saved with any
12536 messages that are received, thus making these variables available at delivery
12537 time.
12538 For outbound connections see &$sending_ip_address$&.
12539
12540 .vitem &$received_port$&
12541 .vindex "&$received_port$&"
12542 See &$received_ip_address$&.
12543
12544 .vitem &$received_protocol$&
12545 .vindex "&$received_protocol$&"
12546 When a message is being processed, this variable contains the name of the
12547 protocol by which it was received. Most of the names used by Exim are defined
12548 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
12549 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
12550 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
12551 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
12552 connection and the client was successfully authenticated.
12553
12554 Exim uses the protocol name &"smtps"& for the case when encryption is
12555 automatically set up on connection without the use of STARTTLS (see
12556 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
12557 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
12558 where the client initially uses EHLO, sets up an encrypted connection using
12559 STARTTLS, and then uses HELO afterwards.
12560
12561 The &%-oMr%& option provides a way of specifying a custom protocol name for
12562 messages that are injected locally by trusted callers. This is commonly used to
12563 identify messages that are being re-injected after some kind of scanning.
12564
12565 .vitem &$received_time$&
12566 .vindex "&$received_time$&"
12567 This variable contains the date and time when the current message was received,
12568 as a number of seconds since the start of the Unix epoch.
12569
12570 .vitem &$recipient_data$&
12571 .vindex "&$recipient_data$&"
12572 This variable is set after an indexing lookup success in an ACL &%recipients%&
12573 condition. It contains the data from the lookup, and the value remains set
12574 until the next &%recipients%& test. Thus, you can do things like this:
12575 .display
12576 &`require recipients = cdb*@;/some/file`&
12577 &`deny `&&'some further test involving'& &`$recipient_data`&
12578 .endd
12579 &*Warning*&: This variable is set only when a lookup is used as an indexing
12580 method in the address list, using the semicolon syntax as in the example above.
12581 The variable is not set for a lookup that is used as part of the string
12582 expansion that all such lists undergo before being interpreted.
12583
12584 .vitem &$recipient_verify_failure$&
12585 .vindex "&$recipient_verify_failure$&"
12586 In an ACL, when a recipient verification fails, this variable contains
12587 information about the failure. It is set to one of the following words:
12588
12589 .ilist
12590 &"qualify"&: The address was unqualified (no domain), and the message
12591 was neither local nor came from an exempted host.
12592
12593 .next
12594 &"route"&: Routing failed.
12595
12596 .next
12597 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
12598 or before the MAIL command (that is, on initial connection, HELO, or
12599 MAIL).
12600
12601 .next
12602 &"recipient"&: The RCPT command in a callout was rejected.
12603 .next
12604
12605 &"postmaster"&: The postmaster check in a callout was rejected.
12606 .endlist
12607
12608 The main use of this variable is expected to be to distinguish between
12609 rejections of MAIL and rejections of RCPT.
12610
12611 .vitem &$recipients$&
12612 .vindex "&$recipients$&"
12613 This variable contains a list of envelope recipients for a message. A comma and
12614 a space separate the addresses in the replacement text. However, the variable
12615 is not generally available, to prevent exposure of Bcc recipients in
12616 unprivileged users' filter files. You can use &$recipients$& only in these
12617 cases:
12618
12619 .olist
12620 In a system filter file.
12621 .next
12622 In the ACLs associated with the DATA command and with non-SMTP messages, that
12623 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
12624 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
12625 &%acl_not_smtp_mime%&.
12626 .next
12627 From within a &[local_scan()]& function.
12628 .endlist
12629
12630
12631 .vitem &$recipients_count$&
12632 .vindex "&$recipients_count$&"
12633 When a message is being processed, this variable contains the number of
12634 envelope recipients that came with the message. Duplicates are not excluded
12635 from the count. While a message is being received over SMTP, the number
12636 increases for each accepted recipient. It can be referenced in an ACL.
12637
12638
12639 .vitem &$regex_match_string$&
12640 .vindex "&$regex_match_string$&"
12641 This variable is set to contain the matching regular expression after a
12642 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
12643
12644 .vitem "&$regex1$&, &$regex2$&, etc"
12645 .cindex "regex submatch variables (&$1regex$& &$2regex$& etc)"
12646 When a &%regex%& or &%mime_regex%& ACL condition succeeds,
12647 these variables contain the
12648 captured substrings identified by the regular expression.
12649
12650
12651 .vitem &$reply_address$&
12652 .vindex "&$reply_address$&"
12653 When a message is being processed, this variable contains the contents of the
12654 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
12655 contents of the &'From:'& header line. Apart from the removal of leading
12656 white space, the value is not processed in any way. In particular, no RFC 2047
12657 decoding or character code translation takes place.
12658
12659 .vitem &$return_path$&
12660 .vindex "&$return_path$&"
12661 When a message is being delivered, this variable contains the return path &--
12662 the sender field that will be sent as part of the envelope. It is not enclosed
12663 in <> characters. At the start of routing an address, &$return_path$& has the
12664 same value as &$sender_address$&, but if, for example, an incoming message to a
12665 mailing list has been expanded by a router which specifies a different address
12666 for bounce messages, &$return_path$& subsequently contains the new bounce
12667 address, whereas &$sender_address$& always contains the original sender address
12668 that was received with the message. In other words, &$sender_address$& contains
12669 the incoming envelope sender, and &$return_path$& contains the outgoing
12670 envelope sender.
12671
12672 .vitem &$return_size_limit$&
12673 .vindex "&$return_size_limit$&"
12674 This is an obsolete name for &$bounce_return_size_limit$&.
12675
12676 .vitem &$router_name$&
12677 .cindex "router" "name"
12678 .cindex "name" "of router"
12679 .vindex "&$router_name$&"
12680 During the running of a router this variable contains its name.
12681
12682 .vitem &$runrc$&
12683 .cindex "return code" "from &%run%& expansion"
12684 .vindex "&$runrc$&"
12685 This variable contains the return code from a command that is run by the
12686 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
12687 assume the order in which option values are expanded, except for those
12688 preconditions whose order of testing is documented. Therefore, you cannot
12689 reliably expect to set &$runrc$& by the expansion of one option, and use it in
12690 another.
12691
12692 .vitem &$self_hostname$&
12693 .oindex "&%self%&" "value of host name"
12694 .vindex "&$self_hostname$&"
12695 When an address is routed to a supposedly remote host that turns out to be the
12696 local host, what happens is controlled by the &%self%& generic router option.
12697 One of its values causes the address to be passed to another router. When this
12698 happens, &$self_hostname$& is set to the name of the local host that the
12699 original router encountered. In other circumstances its contents are null.
12700
12701 .vitem &$sender_address$&
12702 .vindex "&$sender_address$&"
12703 When a message is being processed, this variable contains the sender's address
12704 that was received in the message's envelope. The case of letters in the address
12705 is retained, in both the local part and the domain. For bounce messages, the
12706 value of this variable is the empty string. See also &$return_path$&.
12707
12708 .vitem &$sender_address_data$&
12709 .vindex "&$address_data$&"
12710 .vindex "&$sender_address_data$&"
12711 If &$address_data$& is set when the routers are called from an ACL to verify a
12712 sender address, the final value is preserved in &$sender_address_data$&, to
12713 distinguish it from data from a recipient address. The value does not persist
12714 after the end of the current ACL statement. If you want to preserve it for
12715 longer, you can save it in an ACL variable.
12716
12717 .vitem &$sender_address_domain$&
12718 .vindex "&$sender_address_domain$&"
12719 The domain portion of &$sender_address$&.
12720
12721 .vitem &$sender_address_local_part$&
12722 .vindex "&$sender_address_local_part$&"
12723 The local part portion of &$sender_address$&.
12724
12725 .vitem &$sender_data$&
12726 .vindex "&$sender_data$&"
12727 This variable is set after a lookup success in an ACL &%senders%& condition or
12728 in a router &%senders%& option. It contains the data from the lookup, and the
12729 value remains set until the next &%senders%& test. Thus, you can do things like
12730 this:
12731 .display
12732 &`require senders = cdb*@;/some/file`&
12733 &`deny `&&'some further test involving'& &`$sender_data`&
12734 .endd
12735 &*Warning*&: This variable is set only when a lookup is used as an indexing
12736 method in the address list, using the semicolon syntax as in the example above.
12737 The variable is not set for a lookup that is used as part of the string
12738 expansion that all such lists undergo before being interpreted.
12739
12740 .vitem &$sender_fullhost$&
12741 .vindex "&$sender_fullhost$&"
12742 When a message is received from a remote host, this variable contains the host
12743 name and IP address in a single string. It ends with the IP address in square
12744 brackets, followed by a colon and a port number if the logging of ports is
12745 enabled. The format of the rest of the string depends on whether the host
12746 issued a HELO or EHLO SMTP command, and whether the host name was verified by
12747 looking up its IP address. (Looking up the IP address can be forced by the
12748 &%host_lookup%& option, independent of verification.) A plain host name at the
12749 start of the string is a verified host name; if this is not present,
12750 verification either failed or was not requested. A host name in parentheses is
12751 the argument of a HELO or EHLO command. This is omitted if it is identical to
12752 the verified host name or to the host's IP address in square brackets.
12753
12754 .vitem &$sender_helo_dnssec$&
12755 .vindex "&$sender_helo_dnssec$&"
12756 This boolean variable is true if a successful HELO verification was
12757 .cindex "DNS" "DNSSEC"
12758 done using DNS information the resolver library stated was authenticated data.
12759
12760 .vitem &$sender_helo_name$&
12761 .vindex "&$sender_helo_name$&"
12762 When a message is received from a remote host that has issued a HELO or EHLO
12763 command, the argument of that command is placed in this variable. It is also
12764 set if HELO or EHLO is used when a message is received using SMTP locally via
12765 the &%-bs%& or &%-bS%& options.
12766
12767 .vitem &$sender_host_address$&
12768 .vindex "&$sender_host_address$&"
12769 When a message is received from a remote host using SMTP,
12770 this variable contains that
12771 host's IP address. For locally non-SMTP submitted messages, it is empty.
12772
12773 .vitem &$sender_host_authenticated$&
12774 .vindex "&$sender_host_authenticated$&"
12775 This variable contains the name (not the public name) of the authenticator
12776 driver that successfully authenticated the client from which the message was
12777 received. It is empty if there was no successful authentication. See also
12778 &$authenticated_id$&.
12779
12780 .vitem &$sender_host_dnssec$&
12781 .vindex "&$sender_host_dnssec$&"
12782 If an attempt to populate &$sender_host_name$& has been made
12783 (by reference, &%hosts_lookup%& or
12784 otherwise) then this boolean will have been set true if, and only if, the
12785 resolver library states that both
12786 the reverse and forward DNS were authenticated data. At all
12787 other times, this variable is false.
12788
12789 .cindex "DNS" "DNSSEC"
12790 It is likely that you will need to coerce DNSSEC support on in the resolver
12791 library, by setting:
12792 .code
12793 dns_dnssec_ok = 1
12794 .endd
12795
12796 Exim does not perform DNSSEC validation itself, instead leaving that to a
12797 validating resolver (e.g. unbound, or bind with suitable configuration).
12798
12799 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
12800 mechanism in the list, then this variable will be false.
12801
12802 This requires that your system resolver library support EDNS0 (and that
12803 DNSSEC flags exist in the system headers). If the resolver silently drops
12804 all EDNS0 options, then this will have no effect. OpenBSD's asr resolver
12805 is known to currently ignore EDNS0, documented in CAVEATS of asr_run(3).
12806
12807
12808 .vitem &$sender_host_name$&
12809 .vindex "&$sender_host_name$&"
12810 When a message is received from a remote host, this variable contains the
12811 host's name as obtained by looking up its IP address. For messages received by
12812 other means, this variable is empty.
12813
12814 .vindex "&$host_lookup_failed$&"
12815 If the host name has not previously been looked up, a reference to
12816 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
12817 A looked up name is accepted only if it leads back to the original IP address
12818 via a forward lookup. If either the reverse or the forward lookup fails to find
12819 any data, or if the forward lookup does not yield the original IP address,
12820 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
12821
12822 .vindex "&$host_lookup_deferred$&"
12823 However, if either of the lookups cannot be completed (for example, there is a
12824 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
12825 &$host_lookup_failed$& remains set to &"0"&.
12826
12827 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
12828 host name again if there is a subsequent reference to &$sender_host_name$&
12829 in the same Exim process, but it does try again if &$host_lookup_deferred$&
12830 is set to &"1"&.
12831
12832 Exim does not automatically look up every calling host's name. If you want
12833 maximum efficiency, you should arrange your configuration so that it avoids
12834 these lookups altogether. The lookup happens only if one or more of the
12835 following are true:
12836
12837 .ilist
12838 A string containing &$sender_host_name$& is expanded.
12839 .next
12840 The calling host matches the list in &%host_lookup%&. In the default
12841 configuration, this option is set to *, so it must be changed if lookups are
12842 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
12843 .next
12844 Exim needs the host name in order to test an item in a host list. The items
12845 that require this are described in sections &<<SECThoslispatnam>>& and
12846 &<<SECThoslispatnamsk>>&.
12847 .next
12848 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
12849 In this case, the host name is required to compare with the name quoted in any
12850 EHLO or HELO commands that the client issues.
12851 .next
12852 The remote host issues a EHLO or HELO command that quotes one of the
12853 domains in &%helo_lookup_domains%&. The default value of this option is
12854 . ==== As this is a nested list, any displays it contains must be indented
12855 . ==== as otherwise they are too far to the left.
12856 .code
12857 helo_lookup_domains = @ : @[]
12858 .endd
12859 which causes a lookup if a remote host (incorrectly) gives the server's name or
12860 IP address in an EHLO or HELO command.
12861 .endlist
12862
12863
12864 .vitem &$sender_host_port$&
12865 .vindex "&$sender_host_port$&"
12866 When a message is received from a remote host, this variable contains the port
12867 number that was used on the remote host.
12868
12869 .vitem &$sender_ident$&
12870 .vindex "&$sender_ident$&"
12871 When a message is received from a remote host, this variable contains the
12872 identification received in response to an RFC 1413 request. When a message has
12873 been received locally, this variable contains the login name of the user that
12874 called Exim.
12875
12876 .vitem &$sender_rate_$&&'xxx'&
12877 A number of variables whose names begin &$sender_rate_$& are set as part of the
12878 &%ratelimit%& ACL condition. Details are given in section
12879 &<<SECTratelimiting>>&.
12880
12881 .vitem &$sender_rcvhost$&
12882 .cindex "DNS" "reverse lookup"
12883 .cindex "reverse DNS lookup"
12884 .vindex "&$sender_rcvhost$&"
12885 This is provided specifically for use in &'Received:'& headers. It starts with
12886 either the verified host name (as obtained from a reverse DNS lookup) or, if
12887 there is no verified host name, the IP address in square brackets. After that
12888 there may be text in parentheses. When the first item is a verified host name,
12889 the first thing in the parentheses is the IP address in square brackets,
12890 followed by a colon and a port number if port logging is enabled. When the
12891 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
12892 the parentheses.
12893
12894 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
12895 was used and its argument was not identical to the real host name or IP
12896 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
12897 all three items are present in the parentheses, a newline and tab are inserted
12898 into the string, to improve the formatting of the &'Received:'& header.
12899
12900 .vitem &$sender_verify_failure$&
12901 .vindex "&$sender_verify_failure$&"
12902 In an ACL, when a sender verification fails, this variable contains information
12903 about the failure. The details are the same as for
12904 &$recipient_verify_failure$&.
12905
12906 .vitem &$sending_ip_address$&
12907 .vindex "&$sending_ip_address$&"
12908 This variable is set whenever an outgoing SMTP connection to another host has
12909 been set up. It contains the IP address of the local interface that is being
12910 used. This is useful if a host that has more than one IP address wants to take
12911 on different personalities depending on which one is being used. For incoming
12912 connections, see &$received_ip_address$&.
12913
12914 .vitem &$sending_port$&
12915 .vindex "&$sending_port$&"
12916 This variable is set whenever an outgoing SMTP connection to another host has
12917 been set up. It contains the local port that is being used. For incoming
12918 connections, see &$received_port$&.
12919
12920 .vitem &$smtp_active_hostname$&
12921 .vindex "&$smtp_active_hostname$&"
12922 During an incoming SMTP session, this variable contains the value of the active
12923 host name, as specified by the &%smtp_active_hostname%& option. The value of
12924 &$smtp_active_hostname$& is saved with any message that is received, so its
12925 value can be consulted during routing and delivery.
12926
12927 .vitem &$smtp_command$&
12928 .vindex "&$smtp_command$&"
12929 During the processing of an incoming SMTP command, this variable contains the
12930 entire command. This makes it possible to distinguish between HELO and EHLO in
12931 the HELO ACL, and also to distinguish between commands such as these:
12932 .code
12933 MAIL FROM:<>
12934 MAIL FROM: <>
12935 .endd
12936 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
12937 command, the address in &$smtp_command$& is the original address before any
12938 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
12939 the address after SMTP-time rewriting.
12940
12941 .vitem &$smtp_command_argument$&
12942 .cindex "SMTP" "command, argument for"
12943 .vindex "&$smtp_command_argument$&"
12944 While an ACL is running to check an SMTP command, this variable contains the
12945 argument, that is, the text that follows the command name, with leading white
12946 space removed. Following the introduction of &$smtp_command$&, this variable is
12947 somewhat redundant, but is retained for backwards compatibility.
12948
12949 .vitem &$smtp_command_history$&
12950 .cindex SMTP "command history"
12951 .vindex "&$smtp_command_history$&"
12952 A comma-separated list (with no whitespace) of the most-recent SMTP commands
12953 received, in time-order left to right. Only a limited number of commands
12954 are remembered.
12955
12956 .vitem &$smtp_count_at_connection_start$&
12957 .vindex "&$smtp_count_at_connection_start$&"
12958 This variable is set greater than zero only in processes spawned by the Exim
12959 daemon for handling incoming SMTP connections. The name is deliberately long,
12960 in order to emphasize what the contents are. When the daemon accepts a new
12961 connection, it increments this variable. A copy of the variable is passed to
12962 the child process that handles the connection, but its value is fixed, and
12963 never changes. It is only an approximation of how many incoming connections
12964 there actually are, because many other connections may come and go while a
12965 single connection is being processed. When a child process terminates, the
12966 daemon decrements its copy of the variable.
12967
12968 .vitem "&$sn0$& &-- &$sn9$&"
12969 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
12970 that were current at the end of the system filter file. This allows a system
12971 filter file to set values that can be tested in users' filter files. For
12972 example, a system filter could set a value indicating how likely it is that a
12973 message is junk mail.
12974
12975 .vitem &$spam_$&&'xxx'&
12976 A number of variables whose names start with &$spam$& are available when Exim
12977 is compiled with the content-scanning extension. For details, see section
12978 &<<SECTscanspamass>>&.
12979
12980 .vitem &$spf_header_comment$& &&&
12981 &$spf_received$& &&&
12982 &$spf_result$& &&&
12983 &$spf_result_guessed$& &&&
12984 &$spf_smtp_comment$&
12985 These variables are only available if Exim is built with SPF support.
12986 For details see section &<<SECSPF>>&.
12987
12988 .vitem &$spool_directory$&
12989 .vindex "&$spool_directory$&"
12990 The name of Exim's spool directory.
12991
12992 .vitem &$spool_inodes$&
12993 .vindex "&$spool_inodes$&"
12994 The number of free inodes in the disk partition where Exim's spool files are
12995 being written. The value is recalculated whenever the variable is referenced.
12996 If the relevant file system does not have the concept of inodes, the value of
12997 is -1. See also the &%check_spool_inodes%& option.
12998
12999 .vitem &$spool_space$&
13000 .vindex "&$spool_space$&"
13001 The amount of free space (as a number of kilobytes) in the disk partition where
13002 Exim's spool files are being written. The value is recalculated whenever the
13003 variable is referenced. If the operating system does not have the ability to
13004 find the amount of free space (only true for experimental systems), the space
13005 value is -1. For example, to check in an ACL that there is at least 50
13006 megabytes free on the spool, you could write:
13007 .code
13008 condition = ${if > {$spool_space}{50000}}
13009 .endd
13010 See also the &%check_spool_space%& option.
13011
13012
13013 .vitem &$thisaddress$&
13014 .vindex "&$thisaddress$&"
13015 This variable is set only during the processing of the &%foranyaddress%&
13016 command in a filter file. Its use is explained in the description of that
13017 command, which can be found in the separate document entitled &'Exim's
13018 interfaces to mail filtering'&.
13019
13020 .vitem &$tls_in_bits$&
13021 .vindex "&$tls_in_bits$&"
13022 Contains an approximation of the TLS cipher's bit-strength
13023 on the inbound connection; the meaning of
13024 this depends upon the TLS implementation used.
13025 If TLS has not been negotiated, the value will be 0.
13026 The value of this is automatically fed into the Cyrus SASL authenticator
13027 when acting as a server, to specify the "external SSF" (a SASL term).
13028
13029 The deprecated &$tls_bits$& variable refers to the inbound side
13030 except when used in the context of an outbound SMTP delivery, when it refers to
13031 the outbound.
13032
13033 .vitem &$tls_out_bits$&
13034 .vindex "&$tls_out_bits$&"
13035 Contains an approximation of the TLS cipher's bit-strength
13036 on an outbound SMTP connection; the meaning of
13037 this depends upon the TLS implementation used.
13038 If TLS has not been negotiated, the value will be 0.
13039
13040 .vitem &$tls_in_ourcert$&
13041 .vindex "&$tls_in_ourcert$&"
13042 .cindex certificate variables
13043 This variable refers to the certificate presented to the peer of an
13044 inbound connection when the message was received.
13045 It is only useful as the argument of a
13046 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13047 or a &%def%& condition.
13048
13049 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
13050 when a list of more than one
13051 file is used for &%tls_certificate%&, this variable is not reliable.
13052
13053 .vitem &$tls_in_peercert$&
13054 .vindex "&$tls_in_peercert$&"
13055 This variable refers to the certificate presented by the peer of an
13056 inbound connection when the message was received.
13057 It is only useful as the argument of a
13058 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13059 or a &%def%& condition.
13060 If certificate verification fails it may refer to a failing chain element
13061 which is not the leaf.
13062
13063 .vitem &$tls_out_ourcert$&
13064 .vindex "&$tls_out_ourcert$&"
13065 This variable refers to the certificate presented to the peer of an
13066 outbound connection. It is only useful as the argument of a
13067 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13068 or a &%def%& condition.
13069
13070 .vitem &$tls_out_peercert$&
13071 .vindex "&$tls_out_peercert$&"
13072 This variable refers to the certificate presented by the peer of an
13073 outbound connection. It is only useful as the argument of a
13074 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13075 or a &%def%& condition.
13076 If certificate verification fails it may refer to a failing chain element
13077 which is not the leaf.
13078
13079 .vitem &$tls_in_certificate_verified$&
13080 .vindex "&$tls_in_certificate_verified$&"
13081 This variable is set to &"1"& if a TLS certificate was verified when the
13082 message was received, and &"0"& otherwise.
13083
13084 The deprecated &$tls_certificate_verified$& variable refers to the inbound side
13085 except when used in the context of an outbound SMTP delivery, when it refers to
13086 the outbound.
13087
13088 .vitem &$tls_out_certificate_verified$&
13089 .vindex "&$tls_out_certificate_verified$&"
13090 This variable is set to &"1"& if a TLS certificate was verified when an
13091 outbound SMTP connection was made,
13092 and &"0"& otherwise.
13093
13094 .vitem &$tls_in_cipher$&
13095 .vindex "&$tls_in_cipher$&"
13096 .vindex "&$tls_cipher$&"
13097 When a message is received from a remote host over an encrypted SMTP
13098 connection, this variable is set to the cipher suite that was negotiated, for
13099 example DES-CBC3-SHA. In other circumstances, in particular, for message
13100 received over unencrypted connections, the variable is empty. Testing
13101 &$tls_in_cipher$& for emptiness is one way of distinguishing between encrypted and
13102 non-encrypted connections during ACL processing.
13103
13104 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
13105 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
13106 becomes the same as &$tls_out_cipher$&.
13107
13108 .vitem &$tls_out_cipher$&
13109 .vindex "&$tls_out_cipher$&"
13110 This variable is
13111 cleared before any outgoing SMTP connection is made,
13112 and then set to the outgoing cipher suite if one is negotiated. See chapter
13113 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
13114 details of the &(smtp)& transport.
13115
13116 .vitem &$tls_out_dane$&
13117 .vindex &$tls_out_dane$&
13118 DANE active status. See section &<<SECDANE>>&.
13119
13120 .vitem &$tls_in_ocsp$&
13121 .vindex "&$tls_in_ocsp$&"
13122 When a message is received from a remote client connection
13123 the result of any OCSP request from the client is encoded in this variable:
13124 .code
13125 0 OCSP proof was not requested (default value)
13126 1 No response to request
13127 2 Response not verified
13128 3 Verification failed
13129 4 Verification succeeded
13130 .endd
13131
13132 .vitem &$tls_out_ocsp$&
13133 .vindex "&$tls_out_ocsp$&"
13134 When a message is sent to a remote host connection
13135 the result of any OCSP request made is encoded in this variable.
13136 See &$tls_in_ocsp$& for values.
13137
13138 .vitem &$tls_in_peerdn$&
13139 .vindex "&$tls_in_peerdn$&"
13140 .vindex "&$tls_peerdn$&"
13141 .cindex certificate "extracting fields"
13142 When a message is received from a remote host over an encrypted SMTP
13143 connection, and Exim is configured to request a certificate from the client,
13144 the value of the Distinguished Name of the certificate is made available in the
13145 &$tls_in_peerdn$& during subsequent processing.
13146 If certificate verification fails it may refer to a failing chain element
13147 which is not the leaf.
13148
13149 The deprecated &$tls_peerdn$& variable refers to the inbound side
13150 except when used in the context of an outbound SMTP delivery, when it refers to
13151 the outbound.
13152
13153 .vitem &$tls_out_peerdn$&
13154 .vindex "&$tls_out_peerdn$&"
13155 When a message is being delivered to a remote host over an encrypted SMTP
13156 connection, and Exim is configured to request a certificate from the server,
13157 the value of the Distinguished Name of the certificate is made available in the
13158 &$tls_out_peerdn$& during subsequent processing.
13159 If certificate verification fails it may refer to a failing chain element
13160 which is not the leaf.
13161
13162 .vitem &$tls_in_sni$&
13163 .vindex "&$tls_in_sni$&"
13164 .vindex "&$tls_sni$&"
13165 .cindex "TLS" "Server Name Indication"
13166 When a TLS session is being established, if the client sends the Server
13167 Name Indication extension, the value will be placed in this variable.
13168 If the variable appears in &%tls_certificate%& then this option and
13169 some others, described in &<<SECTtlssni>>&,
13170 will be re-expanded early in the TLS session, to permit
13171 a different certificate to be presented (and optionally a different key to be
13172 used) to the client, based upon the value of the SNI extension.
13173
13174 The deprecated &$tls_sni$& variable refers to the inbound side
13175 except when used in the context of an outbound SMTP delivery, when it refers to
13176 the outbound.
13177
13178 .vitem &$tls_out_sni$&
13179 .vindex "&$tls_out_sni$&"
13180 .cindex "TLS" "Server Name Indication"
13181 During outbound
13182 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
13183 the transport.
13184
13185 .vitem &$tls_out_tlsa_usage$&
13186 .vindex &$tls_out_tlsa_usage$&
13187 Bitfield of TLSA record types found. See section &<<SECDANE>>&.
13188
13189 .vitem &$tod_bsdinbox$&
13190 .vindex "&$tod_bsdinbox$&"
13191 The time of day and the date, in the format required for BSD-style mailbox
13192 files, for example: Thu Oct 17 17:14:09 1995.
13193
13194 .vitem &$tod_epoch$&
13195 .vindex "&$tod_epoch$&"
13196 The time and date as a number of seconds since the start of the Unix epoch.
13197
13198 .vitem &$tod_epoch_l$&
13199 .vindex "&$tod_epoch_l$&"
13200 The time and date as a number of microseconds since the start of the Unix epoch.
13201
13202 .vitem &$tod_full$&
13203 .vindex "&$tod_full$&"
13204 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
13205 +0100. The timezone is always given as a numerical offset from UTC, with
13206 positive values used for timezones that are ahead (east) of UTC, and negative
13207 values for those that are behind (west).
13208
13209 .vitem &$tod_log$&
13210 .vindex "&$tod_log$&"
13211 The time and date in the format used for writing Exim's log files, for example:
13212 1995-10-12 15:32:29, but without a timezone.
13213
13214 .vitem &$tod_logfile$&
13215 .vindex "&$tod_logfile$&"
13216 This variable contains the date in the format yyyymmdd. This is the format that
13217 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
13218 flag.
13219
13220 .vitem &$tod_zone$&
13221 .vindex "&$tod_zone$&"
13222 This variable contains the numerical value of the local timezone, for example:
13223 -0500.
13224
13225 .vitem &$tod_zulu$&
13226 .vindex "&$tod_zulu$&"
13227 This variable contains the UTC date and time in &"Zulu"& format, as specified
13228 by ISO 8601, for example: 20030221154023Z.
13229
13230 .vitem &$transport_name$&
13231 .cindex "transport" "name"
13232 .cindex "name" "of transport"
13233 .vindex "&$transport_name$&"
13234 During the running of a transport, this variable contains its name.
13235
13236 .vitem &$value$&
13237 .vindex "&$value$&"
13238 This variable contains the result of an expansion lookup, extraction operation,
13239 or external command, as described above. It is also used during a
13240 &*reduce*& expansion.
13241
13242 .vitem &$verify_mode$&
13243 .vindex "&$verify_mode$&"
13244 While a router or transport is being run in verify mode or for cutthrough delivery,
13245 contains "S" for sender-verification or "R" for recipient-verification.
13246 Otherwise, empty.
13247
13248 .vitem &$version_number$&
13249 .vindex "&$version_number$&"
13250 The version number of Exim.
13251
13252 .vitem &$warn_message_delay$&
13253 .vindex "&$warn_message_delay$&"
13254 This variable is set only during the creation of a message warning about a
13255 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
13256
13257 .vitem &$warn_message_recipients$&
13258 .vindex "&$warn_message_recipients$&"
13259 This variable is set only during the creation of a message warning about a
13260 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
13261 .endlist
13262 .ecindex IIDstrexp
13263
13264
13265
13266 . ////////////////////////////////////////////////////////////////////////////
13267 . ////////////////////////////////////////////////////////////////////////////
13268
13269 .chapter "Embedded Perl" "CHAPperl"
13270 .scindex IIDperl "Perl" "calling from Exim"
13271 Exim can be built to include an embedded Perl interpreter. When this is done,
13272 Perl subroutines can be called as part of the string expansion process. To make
13273 use of the Perl support, you need version 5.004 or later of Perl installed on
13274 your system. To include the embedded interpreter in the Exim binary, include
13275 the line
13276 .code
13277 EXIM_PERL = perl.o
13278 .endd
13279 in your &_Local/Makefile_& and then build Exim in the normal way.
13280
13281
13282 .section "Setting up so Perl can be used" "SECID85"
13283 .oindex "&%perl_startup%&"
13284 Access to Perl subroutines is via a global configuration option called
13285 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
13286 no &%perl_startup%& option in the Exim configuration file then no Perl
13287 interpreter is started and there is almost no overhead for Exim (since none of
13288 the Perl library will be paged in unless used). If there is a &%perl_startup%&
13289 option then the associated value is taken to be Perl code which is executed in
13290 a newly created Perl interpreter.
13291
13292 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
13293 need backslashes before any characters to escape special meanings. The option
13294 should usually be something like
13295 .code
13296 perl_startup = do '/etc/exim.pl'
13297 .endd
13298 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
13299 use from Exim. Exim can be configured either to start up a Perl interpreter as
13300 soon as it is entered, or to wait until the first time it is needed. Starting
13301 the interpreter at the beginning ensures that it is done while Exim still has
13302 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
13303 fact used in a particular run. Also, note that this does not mean that Exim is
13304 necessarily running as root when Perl is called at a later time. By default,
13305 the interpreter is started only when it is needed, but this can be changed in
13306 two ways:
13307
13308 .ilist
13309 .oindex "&%perl_at_start%&"
13310 Setting &%perl_at_start%& (a boolean option) in the configuration requests
13311 a startup when Exim is entered.
13312 .next
13313 The command line option &%-ps%& also requests a startup when Exim is entered,
13314 overriding the setting of &%perl_at_start%&.
13315 .endlist
13316
13317 There is also a command line option &%-pd%& (for delay) which suppresses the
13318 initial startup, even if &%perl_at_start%& is set.
13319
13320 .ilist
13321 .oindex "&%perl_taintmode%&"
13322 .cindex "Perl" "taintmode"
13323 To provide more security executing Perl code via the embedded Perl
13324 interpreter, the &%perl_taintmode%& option can be set. This enables the
13325 taint mode of the Perl interpreter. You are encouraged to set this
13326 option to a true value. To avoid breaking existing installations, it
13327 defaults to false.
13328
13329
13330 .section "Calling Perl subroutines" "SECID86"
13331 When the configuration file includes a &%perl_startup%& option you can make use
13332 of the string expansion item to call the Perl subroutines that are defined
13333 by the &%perl_startup%& code. The operator is used in any of the following
13334 forms:
13335 .code
13336 ${perl{foo}}
13337 ${perl{foo}{argument}}
13338 ${perl{foo}{argument1}{argument2} ... }
13339 .endd
13340 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
13341 arguments may be passed. Passing more than this results in an expansion failure
13342 with an error message of the form
13343 .code
13344 Too many arguments passed to Perl subroutine "foo" (max is 8)
13345 .endd
13346 The return value of the Perl subroutine is evaluated in a scalar context before
13347 it is passed back to Exim to be inserted into the expanded string. If the
13348 return value is &'undef'&, the expansion is forced to fail in the same way as
13349 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
13350 by obeying Perl's &%die%& function, the expansion fails with the error message
13351 that was passed to &%die%&.
13352
13353
13354 .section "Calling Exim functions from Perl" "SECID87"
13355 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
13356 is available to call back into Exim's string expansion function. For example,
13357 the Perl code
13358 .code
13359 my $lp = Exim::expand_string('$local_part');
13360 .endd
13361 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
13362 Note those are single quotes and not double quotes to protect against
13363 &$local_part$& being interpolated as a Perl variable.
13364
13365 If the string expansion is forced to fail by a &"fail"& item, the result of
13366 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
13367 expansion string, the Perl call from the original expansion string fails with
13368 an appropriate error message, in the same way as if &%die%& were used.
13369
13370 .cindex "debugging" "from embedded Perl"
13371 .cindex "log" "writing from embedded Perl"
13372 Two other Exim functions are available for use from within Perl code.
13373 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
13374 debugging is enabled. If you want a newline at the end, you must supply it.
13375 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
13376 timestamp. In this case, you should not supply a terminating newline.
13377
13378
13379 .section "Use of standard output and error by Perl" "SECID88"
13380 .cindex "Perl" "standard output and error"
13381 You should not write to the standard error or output streams from within your
13382 Perl code, as it is not defined how these are set up. In versions of Exim
13383 before 4.50, it is possible for the standard output or error to refer to the
13384 SMTP connection during message reception via the daemon. Writing to this stream
13385 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
13386 error streams are connected to &_/dev/null_& in the daemon. The chaos is
13387 avoided, but the output is lost.
13388
13389 .cindex "Perl" "use of &%warn%&"
13390 The Perl &%warn%& statement writes to the standard error stream by default.
13391 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
13392 you have no control. When Exim starts up the Perl interpreter, it arranges for
13393 output from the &%warn%& statement to be written to the Exim main log. You can
13394 change this by including appropriate Perl magic somewhere in your Perl code.
13395 For example, to discard &%warn%& output completely, you need this:
13396 .code
13397 $SIG{__WARN__} = sub { };
13398 .endd
13399 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
13400 example, the code for the subroutine is empty, so it does nothing, but you can
13401 include any Perl code that you like. The text of the &%warn%& message is passed
13402 as the first subroutine argument.
13403 .ecindex IIDperl
13404
13405
13406 . ////////////////////////////////////////////////////////////////////////////
13407 . ////////////////////////////////////////////////////////////////////////////
13408
13409 .chapter "Starting the daemon and the use of network interfaces" &&&
13410 "CHAPinterfaces" &&&
13411 "Starting the daemon"
13412 .cindex "daemon" "starting"
13413 .cindex "interface" "listening"
13414 .cindex "network interface"
13415 .cindex "interface" "network"
13416 .cindex "IP address" "for listening"
13417 .cindex "daemon" "listening IP addresses"
13418 .cindex "TCP/IP" "setting listening interfaces"
13419 .cindex "TCP/IP" "setting listening ports"
13420 A host that is connected to a TCP/IP network may have one or more physical
13421 hardware network interfaces. Each of these interfaces may be configured as one
13422 or more &"logical"& interfaces, which are the entities that a program actually
13423 works with. Each of these logical interfaces is associated with an IP address.
13424 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
13425 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
13426 knowledge about the host's interfaces for use in three different circumstances:
13427
13428 .olist
13429 When a listening daemon is started, Exim needs to know which interfaces
13430 and ports to listen on.
13431 .next
13432 When Exim is routing an address, it needs to know which IP addresses
13433 are associated with local interfaces. This is required for the correct
13434 processing of MX lists by removing the local host and others with the
13435 same or higher priority values. Also, Exim needs to detect cases
13436 when an address is routed to an IP address that in fact belongs to the
13437 local host. Unless the &%self%& router option or the &%allow_localhost%&
13438 option of the smtp transport is set (as appropriate), this is treated
13439 as an error situation.
13440 .next
13441 When Exim connects to a remote host, it may need to know which interface to use
13442 for the outgoing connection.
13443 .endlist
13444
13445
13446 Exim's default behaviour is likely to be appropriate in the vast majority
13447 of cases. If your host has only one interface, and you want all its IP
13448 addresses to be treated in the same way, and you are using only the
13449 standard SMTP port, you should not need to take any special action. The
13450 rest of this chapter does not apply to you.
13451
13452 In a more complicated situation you may want to listen only on certain
13453 interfaces, or on different ports, and for this reason there are a number of
13454 options that can be used to influence Exim's behaviour. The rest of this
13455 chapter describes how they operate.
13456
13457 When a message is received over TCP/IP, the interface and port that were
13458 actually used are set in &$received_ip_address$& and &$received_port$&.
13459
13460
13461
13462 .section "Starting a listening daemon" "SECID89"
13463 When a listening daemon is started (by means of the &%-bd%& command line
13464 option), the interfaces and ports on which it listens are controlled by the
13465 following options:
13466
13467 .ilist
13468 &%daemon_smtp_ports%& contains a list of default ports
13469 or service names.
13470 (For backward compatibility, this option can also be specified in the singular.)
13471 .next
13472 &%local_interfaces%& contains list of interface IP addresses on which to
13473 listen. Each item may optionally also specify a port.
13474 .endlist
13475
13476 The default list separator in both cases is a colon, but this can be changed as
13477 described in section &<<SECTlistconstruct>>&. When IPv6 addresses are involved,
13478 it is usually best to change the separator to avoid having to double all the
13479 colons. For example:
13480 .code
13481 local_interfaces = <; 127.0.0.1 ; \
13482 192.168.23.65 ; \
13483 ::1 ; \
13484 3ffe:ffff:836f::fe86:a061
13485 .endd
13486 There are two different formats for specifying a port along with an IP address
13487 in &%local_interfaces%&:
13488
13489 .olist
13490 The port is added onto the address with a dot separator. For example, to listen
13491 on port 1234 on two different IP addresses:
13492 .code
13493 local_interfaces = <; 192.168.23.65.1234 ; \
13494 3ffe:ffff:836f::fe86:a061.1234
13495 .endd
13496 .next
13497 The IP address is enclosed in square brackets, and the port is added
13498 with a colon separator, for example:
13499 .code
13500 local_interfaces = <; [192.168.23.65]:1234 ; \
13501 [3ffe:ffff:836f::fe86:a061]:1234
13502 .endd
13503 .endlist
13504
13505 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
13506 default setting contains just one port:
13507 .code
13508 daemon_smtp_ports = smtp
13509 .endd
13510 If more than one port is listed, each interface that does not have its own port
13511 specified listens on all of them. Ports that are listed in
13512 &%daemon_smtp_ports%& can be identified either by name (defined in
13513 &_/etc/services_&) or by number. However, when ports are given with individual
13514 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
13515
13516
13517
13518 .section "Special IP listening addresses" "SECID90"
13519 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
13520 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
13521 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
13522 instead of setting up separate listening sockets for each interface. The
13523 default value of &%local_interfaces%& is
13524 .code
13525 local_interfaces = 0.0.0.0
13526 .endd
13527 when Exim is built without IPv6 support; otherwise it is:
13528 .code
13529 local_interfaces = <; ::0 ; 0.0.0.0
13530 .endd
13531 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
13532
13533
13534
13535 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
13536 The &%-oX%& command line option can be used to override the values of
13537 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
13538 instance. Another way of doing this would be to use macros and the &%-D%&
13539 option. However, &%-oX%& can be used by any admin user, whereas modification of
13540 the runtime configuration by &%-D%& is allowed only when the caller is root or
13541 exim.
13542
13543 The value of &%-oX%& is a list of items. The default colon separator can be
13544 changed in the usual way if required. If there are any items that do not
13545 contain dots or colons (that is, are not IP addresses), the value of
13546 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
13547 items that do contain dots or colons, the value of &%local_interfaces%& is
13548 replaced by those items. Thus, for example,
13549 .code
13550 -oX 1225
13551 .endd
13552 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
13553 whereas
13554 .code
13555 -oX 192.168.34.5.1125
13556 .endd
13557 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
13558 (However, since &%local_interfaces%& now contains no items without ports, the
13559 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
13560
13561
13562
13563 .section "Support for the submissions (aka SSMTP or SMTPS) protocol" "SECTsupobssmt"
13564 .cindex "submissions protocol"
13565 .cindex "ssmtp protocol"
13566 .cindex "smtps protocol"
13567 .cindex "SMTP" "ssmtp protocol"
13568 .cindex "SMTP" "smtps protocol"
13569 Exim supports the use of TLS-on-connect, used by mail clients in the
13570 &"submissions"& protocol, historically also known as SMTPS or SSMTP.
13571 For some years, IETF Standards Track documents only blessed the
13572 STARTTLS-based Submission service (port 587) while common practice was to support
13573 the same feature set on port 465, but using TLS-on-connect.
13574 If your installation needs to provide service to mail clients
13575 (Mail User Agents, MUAs) then you should provide service on both the 587 and
13576 the 465 TCP ports.
13577
13578 If the &%tls_on_connect_ports%& option is set to a list of port numbers or
13579 service names, connections to those ports must first establish TLS, before
13580 proceeding to the application layer use of the SMTP protocol.
13581
13582 The common use of this option is expected to be
13583 .code
13584 tls_on_connect_ports = 465
13585 .endd
13586 per RFC 8314.
13587 There is also a command line option &%-tls-on-connect%&, which forces all ports
13588 to behave in this way when a daemon is started.
13589
13590 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
13591 daemon to listen on those ports. You must still specify them in
13592 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
13593 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
13594 connections via the daemon.)
13595
13596
13597
13598
13599 .section "IPv6 address scopes" "SECID92"
13600 .cindex "IPv6" "address scopes"
13601 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
13602 can, in principle, have the same link-local IPv6 address on different
13603 interfaces. Thus, additional information is needed, over and above the IP
13604 address, to distinguish individual interfaces. A convention of using a
13605 percent sign followed by something (often the interface name) has been
13606 adopted in some cases, leading to addresses like this:
13607 .code
13608 fe80::202:b3ff:fe03:45c1%eth0
13609 .endd
13610 To accommodate this usage, a percent sign followed by an arbitrary string is
13611 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
13612 to convert a textual IPv6 address for actual use. This function recognizes the
13613 percent convention in operating systems that support it, and it processes the
13614 address appropriately. Unfortunately, some older libraries have problems with
13615 &[getaddrinfo()]&. If
13616 .code
13617 IPV6_USE_INET_PTON=yes
13618 .endd
13619 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
13620 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
13621 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
13622 function.) Of course, this means that the additional functionality of
13623 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
13624
13625 .section "Disabling IPv6" "SECID93"
13626 .cindex "IPv6" "disabling"
13627 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
13628 run on a host whose kernel does not support IPv6. The binary will fall back to
13629 using IPv4, but it may waste resources looking up AAAA records, and trying to
13630 connect to IPv6 addresses, causing delays to mail delivery. If you set the
13631 .oindex "&%disable_ipv6%&"
13632 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
13633 activities take place. AAAA records are never looked up, and any IPv6 addresses
13634 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
13635 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
13636 to handle IPv6 literal addresses.
13637
13638 On the other hand, when IPv6 is in use, there may be times when you want to
13639 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
13640 option to globally suppress the lookup of AAAA records for specified domains,
13641 and you can use the &%ignore_target_hosts%& generic router option to ignore
13642 IPv6 addresses in an individual router.
13643
13644
13645
13646 .section "Examples of starting a listening daemon" "SECID94"
13647 The default case in an IPv6 environment is
13648 .code
13649 daemon_smtp_ports = smtp
13650 local_interfaces = <; ::0 ; 0.0.0.0
13651 .endd
13652 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
13653 Either one or two sockets may be used, depending on the characteristics of
13654 the TCP/IP stack. (This is complicated and messy; for more information,
13655 read the comments in the &_daemon.c_& source file.)
13656
13657 To specify listening on ports 25 and 26 on all interfaces:
13658 .code
13659 daemon_smtp_ports = 25 : 26
13660 .endd
13661 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
13662 .code
13663 local_interfaces = <; ::0.25 ; ::0.26 \
13664 0.0.0.0.25 ; 0.0.0.0.26
13665 .endd
13666 To listen on the default port on all IPv4 interfaces, and on port 26 on the
13667 IPv4 loopback address only:
13668 .code
13669 local_interfaces = 0.0.0.0 : 127.0.0.1.26
13670 .endd
13671 To specify listening on the default port on specific interfaces only:
13672 .code
13673 local_interfaces = 10.0.0.67 : 192.168.34.67
13674 .endd
13675 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
13676
13677
13678
13679 .section "Recognizing the local host" "SECTreclocipadd"
13680 The &%local_interfaces%& option is also used when Exim needs to determine
13681 whether or not an IP address refers to the local host. That is, the IP
13682 addresses of all the interfaces on which a daemon is listening are always
13683 treated as local.
13684
13685 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
13686 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
13687 available interfaces from the operating system, and extracts the relevant
13688 (that is, IPv4 or IPv6) addresses to use for checking.
13689
13690 Some systems set up large numbers of virtual interfaces in order to provide
13691 many virtual web servers. In this situation, you may want to listen for
13692 email on only a few of the available interfaces, but nevertheless treat all
13693 interfaces as local when routing. You can do this by setting
13694 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
13695 &"all"& wildcard values. These addresses are recognized as local, but are not
13696 used for listening. Consider this example:
13697 .code
13698 local_interfaces = <; 127.0.0.1 ; ::1 ; \
13699 192.168.53.235 ; \
13700 3ffe:2101:12:1:a00:20ff:fe86:a061
13701
13702 extra_local_interfaces = <; ::0 ; 0.0.0.0
13703 .endd
13704 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
13705 address, but all available interface addresses are treated as local when
13706 Exim is routing.
13707
13708 In some environments the local host name may be in an MX list, but with an IP
13709 address that is not assigned to any local interface. In other cases it may be
13710 desirable to treat other host names as if they referred to the local host. Both
13711 these cases can be handled by setting the &%hosts_treat_as_local%& option.
13712 This contains host names rather than IP addresses. When a host is referenced
13713 during routing, either via an MX record or directly, it is treated as the local
13714 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
13715 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
13716
13717
13718
13719 .section "Delivering to a remote host" "SECID95"
13720 Delivery to a remote host is handled by the smtp transport. By default, it
13721 allows the system's TCP/IP functions to choose which interface to use (if
13722 there is more than one) when connecting to a remote host. However, the
13723 &%interface%& option can be set to specify which interface is used. See the
13724 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
13725 details.
13726
13727
13728
13729
13730 . ////////////////////////////////////////////////////////////////////////////
13731 . ////////////////////////////////////////////////////////////////////////////
13732
13733 .chapter "Main configuration" "CHAPmainconfig"
13734 .scindex IIDconfima "configuration file" "main section"
13735 .scindex IIDmaiconf "main configuration"
13736 The first part of the run time configuration file contains three types of item:
13737
13738 .ilist
13739 Macro definitions: These lines start with an upper case letter. See section
13740 &<<SECTmacrodefs>>& for details of macro processing.
13741 .next
13742 Named list definitions: These lines start with one of the words &"domainlist"&,
13743 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
13744 section &<<SECTnamedlists>>&.
13745 .next
13746 Main configuration settings: Each setting occupies one line of the file
13747 (with possible continuations). If any setting is preceded by the word
13748 &"hide"&, the &%-bP%& command line option displays its value to admin users
13749 only. See section &<<SECTcos>>& for a description of the syntax of these option
13750 settings.
13751 .endlist
13752
13753 This chapter specifies all the main configuration options, along with their
13754 types and default values. For ease of finding a particular option, they appear
13755 in alphabetical order in section &<<SECTalomo>>& below. However, because there
13756 are now so many options, they are first listed briefly in functional groups, as
13757 an aid to finding the name of the option you are looking for. Some options are
13758 listed in more than one group.
13759
13760 .section "Miscellaneous" "SECID96"
13761 .table2
13762 .row &%bi_command%& "to run for &%-bi%& command line option"
13763 .row &%debug_store%& "do extra internal checks"
13764 .row &%disable_ipv6%& "do no IPv6 processing"
13765 .row &%keep_malformed%& "for broken files &-- should not happen"
13766 .row &%localhost_number%& "for unique message ids in clusters"
13767 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
13768 .row &%message_body_visible%& "how much to show in &$message_body$&"
13769 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
13770 .row &%print_topbitchars%& "top-bit characters are printing"
13771 .row &%spool_wireformat%& "use wire-format spool data files when possible"
13772 .row &%timezone%& "force time zone"
13773 .endtable
13774
13775
13776 .section "Exim parameters" "SECID97"
13777 .table2
13778 .row &%exim_group%& "override compiled-in value"
13779 .row &%exim_path%& "override compiled-in value"
13780 .row &%exim_user%& "override compiled-in value"
13781 .row &%primary_hostname%& "default from &[uname()]&"
13782 .row &%split_spool_directory%& "use multiple directories"
13783 .row &%spool_directory%& "override compiled-in value"
13784 .endtable
13785
13786
13787
13788 .section "Privilege controls" "SECID98"
13789 .table2
13790 .row &%admin_groups%& "groups that are Exim admin users"
13791 .row &%commandline_checks_require_admin%& "require admin for various checks"
13792 .row &%deliver_drop_privilege%& "drop root for delivery processes"
13793 .row &%local_from_check%& "insert &'Sender:'& if necessary"
13794 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
13795 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
13796 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
13797 .row &%never_users%& "do not run deliveries as these"
13798 .row &%prod_requires_admin%& "forced delivery requires admin user"
13799 .row &%queue_list_requires_admin%& "queue listing requires admin user"
13800 .row &%trusted_groups%& "groups that are trusted"
13801 .row &%trusted_users%& "users that are trusted"
13802 .endtable
13803
13804
13805
13806 .section "Logging" "SECID99"
13807 .table2
13808 .row &%event_action%& "custom logging"
13809 .row &%hosts_connection_nolog%& "exemption from connect logging"
13810 .row &%log_file_path%& "override compiled-in value"
13811 .row &%log_selector%& "set/unset optional logging"
13812 .row &%log_timezone%& "add timezone to log lines"
13813 .row &%message_logs%& "create per-message logs"
13814 .row &%preserve_message_logs%& "after message completion"
13815 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
13816 .row &%slow_lookup_log%& "control logging of slow DNS lookups"
13817 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
13818 .row &%syslog_facility%& "set syslog &""facility""& field"
13819 .row &%syslog_pid%& "pid in syslog lines"
13820 .row &%syslog_processname%& "set syslog &""ident""& field"
13821 .row &%syslog_timestamp%& "timestamp syslog lines"
13822 .row &%write_rejectlog%& "control use of message log"
13823 .endtable
13824
13825
13826
13827 .section "Frozen messages" "SECID100"
13828 .table2
13829 .row &%auto_thaw%& "sets time for retrying frozen messages"
13830 .row &%freeze_tell%& "send message when freezing"
13831 .row &%move_frozen_messages%& "to another directory"
13832 .row &%timeout_frozen_after%& "keep frozen messages only so long"
13833 .endtable
13834
13835
13836
13837 .section "Data lookups" "SECID101"
13838 .table2
13839 .row &%ibase_servers%& "InterBase servers"
13840 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
13841 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
13842 .row &%ldap_cert_file%& "client cert file for LDAP"
13843 .row &%ldap_cert_key%& "client key file for LDAP"
13844 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
13845 .row &%ldap_default_servers%& "used if no server in query"
13846 .row &%ldap_require_cert%& "action to take without LDAP server cert"
13847 .row &%ldap_start_tls%& "require TLS within LDAP"
13848 .row &%ldap_version%& "set protocol version"
13849 .row &%lookup_open_max%& "lookup files held open"
13850 .row &%mysql_servers%& "default MySQL servers"
13851 .row &%oracle_servers%& "Oracle servers"
13852 .row &%pgsql_servers%& "default PostgreSQL servers"
13853 .row &%sqlite_lock_timeout%& "as it says"
13854 .endtable
13855
13856
13857
13858 .section "Message ids" "SECID102"
13859 .table2
13860 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
13861 .row &%message_id_header_text%& "ditto"
13862 .endtable
13863
13864
13865
13866 .section "Embedded Perl Startup" "SECID103"
13867 .table2
13868 .row &%perl_at_start%& "always start the interpreter"
13869 .row &%perl_startup%& "code to obey when starting Perl"
13870 .row &%perl_taintmode%& "enable taint mode in Perl"
13871 .endtable
13872
13873
13874
13875 .section "Daemon" "SECID104"
13876 .table2
13877 .row &%daemon_smtp_ports%& "default ports"
13878 .row &%daemon_startup_retries%& "number of times to retry"
13879 .row &%daemon_startup_sleep%& "time to sleep between tries"
13880 .row &%extra_local_interfaces%& "not necessarily listened on"
13881 .row &%local_interfaces%& "on which to listen, with optional ports"
13882 .row &%pid_file_path%& "override compiled-in value"
13883 .row &%queue_run_max%& "maximum simultaneous queue runners"
13884 .endtable
13885
13886
13887
13888 .section "Resource control" "SECID105"
13889 .table2
13890 .row &%check_log_inodes%& "before accepting a message"
13891 .row &%check_log_space%& "before accepting a message"
13892 .row &%check_spool_inodes%& "before accepting a message"
13893 .row &%check_spool_space%& "before accepting a message"
13894 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
13895 .row &%queue_only_load%& "queue incoming if load high"
13896 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
13897 .row &%queue_run_max%& "maximum simultaneous queue runners"
13898 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
13899 .row &%smtp_accept_max%& "simultaneous incoming connections"
13900 .row &%smtp_accept_max_nonmail%& "non-mail commands"
13901 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
13902 .row &%smtp_accept_max_per_connection%& "messages per connection"
13903 .row &%smtp_accept_max_per_host%& "connections from one host"
13904 .row &%smtp_accept_queue%& "queue mail if more connections"
13905 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
13906 connection"
13907 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
13908 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
13909 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
13910 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
13911 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
13912 .endtable
13913
13914
13915
13916 .section "Policy controls" "SECID106"
13917 .table2
13918 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
13919 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
13920 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
13921 .row &%acl_smtp_auth%& "ACL for AUTH"
13922 .row &%acl_smtp_connect%& "ACL for connection"
13923 .row &%acl_smtp_data%& "ACL for DATA"
13924 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
13925 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
13926 .row &%acl_smtp_etrn%& "ACL for ETRN"
13927 .row &%acl_smtp_expn%& "ACL for EXPN"
13928 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
13929 .row &%acl_smtp_mail%& "ACL for MAIL"
13930 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
13931 .row &%acl_smtp_mime%& "ACL for MIME parts"
13932 .row &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
13933 .row &%acl_smtp_predata%& "ACL for start of data"
13934 .row &%acl_smtp_quit%& "ACL for QUIT"
13935 .row &%acl_smtp_rcpt%& "ACL for RCPT"
13936 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
13937 .row &%acl_smtp_vrfy%& "ACL for VRFY"
13938 .row &%av_scanner%& "specify virus scanner"
13939 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
13940 words""&"
13941 .row &%dns_cname_loops%& "follow CNAMEs returned by resolver"
13942 .row &%dns_csa_search_limit%& "control CSA parent search depth"
13943 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
13944 .row &%header_maxsize%& "total size of message header"
13945 .row &%header_line_maxsize%& "individual header line limit"
13946 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
13947 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
13948 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
13949 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
13950 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
13951 .row &%host_lookup%& "host name looked up for these hosts"
13952 .row &%host_lookup_order%& "order of DNS and local name lookups"
13953 .row &%hosts_proxy%& "use proxy protocol for these hosts"
13954 .row &%host_reject_connection%& "reject connection from these hosts"
13955 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
13956 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
13957 .row &%message_size_limit%& "for all messages"
13958 .row &%percent_hack_domains%& "recognize %-hack for these domains"
13959 .row &%spamd_address%& "set interface to SpamAssassin"
13960 .row &%strict_acl_vars%& "object to unset ACL variables"
13961 .endtable
13962
13963
13964
13965 .section "Callout cache" "SECID107"
13966 .table2
13967 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
13968 item"
13969 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
13970 item"
13971 .row &%callout_negative_expire%& "timeout for negative address cache item"
13972 .row &%callout_positive_expire%& "timeout for positive address cache item"
13973 .row &%callout_random_local_part%& "string to use for &""random""& testing"
13974 .endtable
13975
13976
13977
13978 .section "TLS" "SECID108"
13979 .table2
13980 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
13981 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
13982 .row &%openssl_options%& "adjust OpenSSL compatibility options"
13983 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
13984 .row &%tls_certificate%& "location of server certificate"
13985 .row &%tls_crl%& "certificate revocation list"
13986 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
13987 .row &%tls_dhparam%& "DH parameters for server"
13988 .row &%tls_eccurve%& "EC curve selection for server"
13989 .row &%tls_ocsp_file%& "location of server certificate status proof"
13990 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
13991 .row &%tls_privatekey%& "location of server private key"
13992 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
13993 .row &%tls_require_ciphers%& "specify acceptable ciphers"
13994 .row &%tls_try_verify_hosts%& "try to verify client certificate"
13995 .row &%tls_verify_certificates%& "expected client certificates"
13996 .row &%tls_verify_hosts%& "insist on client certificate verify"
13997 .endtable
13998
13999
14000
14001 .section "Local user handling" "SECID109"
14002 .table2
14003 .row &%finduser_retries%& "useful in NIS environments"
14004 .row &%gecos_name%& "used when creating &'Sender:'&"
14005 .row &%gecos_pattern%& "ditto"
14006 .row &%max_username_length%& "for systems that truncate"
14007 .row &%unknown_login%& "used when no login name found"
14008 .row &%unknown_username%& "ditto"
14009 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
14010 .row &%uucp_from_sender%& "ditto"
14011 .endtable
14012
14013
14014
14015 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
14016 .table2
14017 .row &%header_maxsize%& "total size of message header"
14018 .row &%header_line_maxsize%& "individual header line limit"
14019 .row &%message_size_limit%& "applies to all messages"
14020 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14021 .row &%received_header_text%& "expanded to make &'Received:'&"
14022 .row &%received_headers_max%& "for mail loop detection"
14023 .row &%recipients_max%& "limit per message"
14024 .row &%recipients_max_reject%& "permanently reject excess recipients"
14025 .endtable
14026
14027
14028
14029
14030 .section "Non-SMTP incoming messages" "SECID111"
14031 .table2
14032 .row &%receive_timeout%& "for non-SMTP messages"
14033 .endtable
14034
14035
14036
14037
14038
14039 .section "Incoming SMTP messages" "SECID112"
14040 See also the &'Policy controls'& section above.
14041
14042 .table2
14043 .row &%dkim_verify_signers%& "DKIM domain for which DKIM ACL is run"
14044 .row &%host_lookup%& "host name looked up for these hosts"
14045 .row &%host_lookup_order%& "order of DNS and local name lookups"
14046 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
14047 .row &%rfc1413_hosts%& "make ident calls to these hosts"
14048 .row &%rfc1413_query_timeout%& "zero disables ident calls"
14049 .row &%sender_unqualified_hosts%& "may send unqualified senders"
14050 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
14051 .row &%smtp_accept_max%& "simultaneous incoming connections"
14052 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14053 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14054 .row &%smtp_accept_max_per_connection%& "messages per connection"
14055 .row &%smtp_accept_max_per_host%& "connections from one host"
14056 .row &%smtp_accept_queue%& "queue mail if more connections"
14057 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14058 connection"
14059 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14060 .row &%smtp_active_hostname%& "host name to use in messages"
14061 .row &%smtp_banner%& "text for welcome banner"
14062 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14063 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14064 .row &%smtp_enforce_sync%& "of SMTP command/responses"
14065 .row &%smtp_etrn_command%& "what to run for ETRN"
14066 .row &%smtp_etrn_serialize%& "only one at once"
14067 .row &%smtp_load_reserve%& "only reserve hosts if this load"
14068 .row &%smtp_max_unknown_commands%& "before dropping connection"
14069 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
14070 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
14071 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
14072 .row &%smtp_receive_timeout%& "per command or data line"
14073 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14074 .row &%smtp_return_error_details%& "give detail on rejections"
14075 .endtable
14076
14077
14078
14079 .section "SMTP extensions" "SECID113"
14080 .table2
14081 .row &%accept_8bitmime%& "advertise 8BITMIME"
14082 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
14083 .row &%chunking_advertise_hosts%& "advertise CHUNKING to these hosts"
14084 .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
14085 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
14086 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
14087 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
14088 .row &%prdr_enable%& "advertise PRDR to all hosts"
14089 .row &%smtputf8_advertise_hosts%& "advertise SMTPUTF8 to these hosts"
14090 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14091 .endtable
14092
14093
14094
14095 .section "Processing messages" "SECID114"
14096 .table2
14097 .row &%allow_domain_literals%& "recognize domain literal syntax"
14098 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
14099 .row &%allow_utf8_domains%& "in addresses"
14100 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14101 words""&"
14102 .row &%delivery_date_remove%& "from incoming messages"
14103 .row &%envelope_to_remove%& "from incoming messages"
14104 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
14105 .row &%headers_charset%& "default for translations"
14106 .row &%qualify_domain%& "default for senders"
14107 .row &%qualify_recipient%& "default for recipients"
14108 .row &%return_path_remove%& "from incoming messages"
14109 .row &%strip_excess_angle_brackets%& "in addresses"
14110 .row &%strip_trailing_dot%& "at end of addresses"
14111 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
14112 .endtable
14113
14114
14115
14116 .section "System filter" "SECID115"
14117 .table2
14118 .row &%system_filter%& "locate system filter"
14119 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
14120 directory"
14121 .row &%system_filter_file_transport%& "transport for delivery to a file"
14122 .row &%system_filter_group%& "group for filter running"
14123 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
14124 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
14125 .row &%system_filter_user%& "user for filter running"
14126 .endtable
14127
14128
14129
14130 .section "Routing and delivery" "SECID116"
14131 .table2
14132 .row &%disable_ipv6%& "do no IPv6 processing"
14133 .row &%dns_again_means_nonexist%& "for broken domains"
14134 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
14135 .row &%dns_dnssec_ok%& "parameter for resolver"
14136 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
14137 .row &%dns_retrans%& "parameter for resolver"
14138 .row &%dns_retry%& "parameter for resolver"
14139 .row &%dns_trust_aa%& "DNS zones trusted as authentic"
14140 .row &%dns_use_edns0%& "parameter for resolver"
14141 .row &%hold_domains%& "hold delivery for these domains"
14142 .row &%local_interfaces%& "for routing checks"
14143 .row &%queue_domains%& "no immediate delivery for these"
14144 .row &%queue_only%& "no immediate delivery at all"
14145 .row &%queue_only_file%& "no immediate delivery if file exists"
14146 .row &%queue_only_load%& "no immediate delivery if load is high"
14147 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14148 .row &%queue_only_override%& "allow command line to override"
14149 .row &%queue_run_in_order%& "order of arrival"
14150 .row &%queue_run_max%& "of simultaneous queue runners"
14151 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
14152 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14153 .row &%remote_sort_domains%& "order of remote deliveries"
14154 .row &%retry_data_expire%& "timeout for retry data"
14155 .row &%retry_interval_max%& "safety net for retry rules"
14156 .endtable
14157
14158
14159
14160 .section "Bounce and warning messages" "SECID117"
14161 .table2
14162 .row &%bounce_message_file%& "content of bounce"
14163 .row &%bounce_message_text%& "content of bounce"
14164 .row &%bounce_return_body%& "include body if returning message"
14165 .row &%bounce_return_linesize_limit%& "limit on returned message line length"
14166 .row &%bounce_return_message%& "include original message in bounce"
14167 .row &%bounce_return_size_limit%& "limit on returned message"
14168 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
14169 .row &%dsn_from%& "set &'From:'& contents in bounces"
14170 .row &%errors_copy%& "copy bounce messages"
14171 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
14172 .row &%delay_warning%& "time schedule"
14173 .row &%delay_warning_condition%& "condition for warning messages"
14174 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
14175 .row &%smtp_return_error_details%& "give detail on rejections"
14176 .row &%warn_message_file%& "content of warning message"
14177 .endtable
14178
14179
14180
14181 .section "Alphabetical list of main options" "SECTalomo"
14182 Those options that undergo string expansion before use are marked with
14183 &dagger;.
14184
14185 .option accept_8bitmime main boolean true
14186 .cindex "8BITMIME"
14187 .cindex "8-bit characters"
14188 .cindex "log" "selectors"
14189 .cindex "log" "8BITMIME"
14190 This option causes Exim to send 8BITMIME in its response to an SMTP
14191 EHLO command, and to accept the BODY= parameter on MAIL commands.
14192 However, though Exim is 8-bit clean, it is not a protocol converter, and it
14193 takes no steps to do anything special with messages received by this route.
14194
14195 Historically Exim kept this option off by default, but the maintainers
14196 feel that in today's Internet, this causes more problems than it solves.
14197 It now defaults to true.
14198 A more detailed analysis of the issues is provided by Dan Bernstein:
14199 .display
14200 &url(http://cr.yp.to/smtp/8bitmime.html)
14201 .endd
14202
14203 To log received 8BITMIME status use
14204 .code
14205 log_selector = +8bitmime
14206 .endd
14207
14208 .option acl_not_smtp main string&!! unset
14209 .cindex "&ACL;" "for non-SMTP messages"
14210 .cindex "non-SMTP messages" "ACLs for"
14211 This option defines the ACL that is run when a non-SMTP message has been
14212 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
14213 further details.
14214
14215 .option acl_not_smtp_mime main string&!! unset
14216 This option defines the ACL that is run for individual MIME parts of non-SMTP
14217 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
14218 SMTP messages.
14219
14220 .option acl_not_smtp_start main string&!! unset
14221 .cindex "&ACL;" "at start of non-SMTP message"
14222 .cindex "non-SMTP messages" "ACLs for"
14223 This option defines the ACL that is run before Exim starts reading a
14224 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
14225
14226 .option acl_smtp_auth main string&!! unset
14227 .cindex "&ACL;" "setting up for SMTP commands"
14228 .cindex "AUTH" "ACL for"
14229 This option defines the ACL that is run when an SMTP AUTH command is
14230 received. See chapter &<<CHAPACL>>& for further details.
14231
14232 .option acl_smtp_connect main string&!! unset
14233 .cindex "&ACL;" "on SMTP connection"
14234 This option defines the ACL that is run when an SMTP connection is received.
14235 See chapter &<<CHAPACL>>& for further details.
14236
14237 .option acl_smtp_data main string&!! unset
14238 .cindex "DATA" "ACL for"
14239 This option defines the ACL that is run after an SMTP DATA command has been
14240 processed and the message itself has been received, but before the final
14241 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
14242
14243 .option acl_smtp_data_prdr main string&!! accept
14244 .cindex "PRDR" "ACL for"
14245 .cindex "DATA" "PRDR ACL for"
14246 .cindex "&ACL;" "PRDR-related"
14247 .cindex "&ACL;" "per-user data processing"
14248 This option defines the ACL that,
14249 if the PRDR feature has been negotiated,
14250 is run for each recipient after an SMTP DATA command has been
14251 processed and the message itself has been received, but before the
14252 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
14253
14254 .option acl_smtp_dkim main string&!! unset
14255 .cindex DKIM "ACL for"
14256 This option defines the ACL that is run for each DKIM signature
14257 (by default, or as specified in the dkim_verify_signers option)
14258 of a received message.
14259 See section &<<SECDKIMVFY>>& for further details.
14260
14261 .option acl_smtp_etrn main string&!! unset
14262 .cindex "ETRN" "ACL for"
14263 This option defines the ACL that is run when an SMTP ETRN command is
14264 received. See chapter &<<CHAPACL>>& for further details.
14265
14266 .option acl_smtp_expn main string&!! unset
14267 .cindex "EXPN" "ACL for"
14268 This option defines the ACL that is run when an SMTP EXPN command is
14269 received. See chapter &<<CHAPACL>>& for further details.
14270
14271 .option acl_smtp_helo main string&!! unset
14272 .cindex "EHLO" "ACL for"
14273 .cindex "HELO" "ACL for"
14274 This option defines the ACL that is run when an SMTP EHLO or HELO
14275 command is received. See chapter &<<CHAPACL>>& for further details.
14276
14277
14278 .option acl_smtp_mail main string&!! unset
14279 .cindex "MAIL" "ACL for"
14280 This option defines the ACL that is run when an SMTP MAIL command is
14281 received. See chapter &<<CHAPACL>>& for further details.
14282
14283 .option acl_smtp_mailauth main string&!! unset
14284 .cindex "AUTH" "on MAIL command"
14285 This option defines the ACL that is run when there is an AUTH parameter on
14286 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
14287 &<<CHAPSMTPAUTH>>& for details of authentication.
14288
14289 .option acl_smtp_mime main string&!! unset
14290 .cindex "MIME content scanning" "ACL for"
14291 This option is available when Exim is built with the content-scanning
14292 extension. It defines the ACL that is run for each MIME part in a message. See
14293 section &<<SECTscanmimepart>>& for details.
14294
14295 .option acl_smtp_notquit main string&!! unset
14296 .cindex "not-QUIT, ACL for"
14297 This option defines the ACL that is run when an SMTP session
14298 ends without a QUIT command being received.
14299 See chapter &<<CHAPACL>>& for further details.
14300
14301 .option acl_smtp_predata main string&!! unset
14302 This option defines the ACL that is run when an SMTP DATA command is
14303 received, before the message itself is received. See chapter &<<CHAPACL>>& for
14304 further details.
14305
14306 .option acl_smtp_quit main string&!! unset
14307 .cindex "QUIT, ACL for"
14308 This option defines the ACL that is run when an SMTP QUIT command is
14309 received. See chapter &<<CHAPACL>>& for further details.
14310
14311 .option acl_smtp_rcpt main string&!! unset
14312 .cindex "RCPT" "ACL for"
14313 This option defines the ACL that is run when an SMTP RCPT command is
14314 received. See chapter &<<CHAPACL>>& for further details.
14315
14316 .option acl_smtp_starttls main string&!! unset
14317 .cindex "STARTTLS, ACL for"
14318 This option defines the ACL that is run when an SMTP STARTTLS command is
14319 received. See chapter &<<CHAPACL>>& for further details.
14320
14321 .option acl_smtp_vrfy main string&!! unset
14322 .cindex "VRFY" "ACL for"
14323 This option defines the ACL that is run when an SMTP VRFY command is
14324 received. See chapter &<<CHAPACL>>& for further details.
14325
14326 .option add_environment main "string list" empty
14327 .cindex "environment" "set values"
14328 This option allows to set individual environment variables that the
14329 currently linked libraries and programs in child processes use.
14330 See &<<SECTpipeenv>>& for the environment of &(pipe)& transports.
14331
14332 .option admin_groups main "string list&!!" unset
14333 .cindex "admin user"
14334 This option is expanded just once, at the start of Exim's processing. If the
14335 current group or any of the supplementary groups of an Exim caller is in this
14336 colon-separated list, the caller has admin privileges. If all your system
14337 programmers are in a specific group, for example, you can give them all Exim
14338 admin privileges by putting that group in &%admin_groups%&. However, this does
14339 not permit them to read Exim's spool files (whose group owner is the Exim gid).
14340 To permit this, you have to add individuals to the Exim group.
14341
14342 .option allow_domain_literals main boolean false
14343 .cindex "domain literal"
14344 If this option is set, the RFC 2822 domain literal format is permitted in
14345 email addresses. The option is not set by default, because the domain literal
14346 format is not normally required these days, and few people know about it. It
14347 has, however, been exploited by mail abusers.
14348
14349 Unfortunately, it seems that some DNS black list maintainers are using this
14350 format to report black listing to postmasters. If you want to accept messages
14351 addressed to your hosts by IP address, you need to set
14352 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
14353 domains (defined in the named domain list &%local_domains%& in the default
14354 configuration). This &"magic string"& matches the domain literal form of all
14355 the local host's IP addresses.
14356
14357
14358 .option allow_mx_to_ip main boolean false
14359 .cindex "MX record" "pointing to IP address"
14360 It appears that more and more DNS zone administrators are breaking the rules
14361 and putting domain names that look like IP addresses on the right hand side of
14362 MX records. Exim follows the rules and rejects this, giving an error message
14363 that explains the misconfiguration. However, some other MTAs support this
14364 practice, so to avoid &"Why can't Exim do this?"& complaints,
14365 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
14366 recommended, except when you have no other choice.
14367
14368 .option allow_utf8_domains main boolean false
14369 .cindex "domain" "UTF-8 characters in"
14370 .cindex "UTF-8" "in domain name"
14371 Lots of discussion is going on about internationalized domain names. One
14372 camp is strongly in favour of just using UTF-8 characters, and it seems
14373 that at least two other MTAs permit this. This option allows Exim users to
14374 experiment if they wish.
14375
14376 If it is set true, Exim's domain parsing function allows valid
14377 UTF-8 multicharacters to appear in domain name components, in addition to
14378 letters, digits, and hyphens. However, just setting this option is not
14379 enough; if you want to look up these domain names in the DNS, you must also
14380 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
14381 suitable setting is:
14382 .code
14383 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
14384 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
14385 .endd
14386 Alternatively, you can just disable this feature by setting
14387 .code
14388 dns_check_names_pattern =
14389 .endd
14390 That is, set the option to an empty string so that no check is done.
14391
14392
14393 .option auth_advertise_hosts main "host list&!!" *
14394 .cindex "authentication" "advertising"
14395 .cindex "AUTH" "advertising"
14396 If any server authentication mechanisms are configured, Exim advertises them in
14397 response to an EHLO command only if the calling host matches this list.
14398 Otherwise, Exim does not advertise AUTH.
14399 Exim does not accept AUTH commands from clients to which it has not
14400 advertised the availability of AUTH. The advertising of individual
14401 authentication mechanisms can be controlled by the use of the
14402 &%server_advertise_condition%& generic authenticator option on the individual
14403 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
14404
14405 Certain mail clients (for example, Netscape) require the user to provide a name
14406 and password for authentication if AUTH is advertised, even though it may
14407 not be needed (the host may accept messages from hosts on its local LAN without
14408 authentication, for example). The &%auth_advertise_hosts%& option can be used
14409 to make these clients more friendly by excluding them from the set of hosts to
14410 which Exim advertises AUTH.
14411
14412 .cindex "AUTH" "advertising when encrypted"
14413 If you want to advertise the availability of AUTH only when the connection
14414 is encrypted using TLS, you can make use of the fact that the value of this
14415 option is expanded, with a setting like this:
14416 .code
14417 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
14418 .endd
14419 .vindex "&$tls_in_cipher$&"
14420 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
14421 the expansion is empty, thus matching no hosts. Otherwise, the result of the
14422 expansion is *, which matches all hosts.
14423
14424
14425 .option auto_thaw main time 0s
14426 .cindex "thawing messages"
14427 .cindex "unfreezing messages"
14428 If this option is set to a time greater than zero, a queue runner will try a
14429 new delivery attempt on any frozen message, other than a bounce message, if
14430 this much time has passed since it was frozen. This may result in the message
14431 being re-frozen if nothing has changed since the last attempt. It is a way of
14432 saying &"keep on trying, even though there are big problems"&.
14433
14434 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
14435 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
14436 thought to be very useful any more, and its use should probably be avoided.
14437
14438
14439 .option av_scanner main string "see below"
14440 This option is available if Exim is built with the content-scanning extension.
14441 It specifies which anti-virus scanner to use. The default value is:
14442 .code
14443 sophie:/var/run/sophie
14444 .endd
14445 If the value of &%av_scanner%& starts with a dollar character, it is expanded
14446 before use. See section &<<SECTscanvirus>>& for further details.
14447
14448
14449 .option bi_command main string unset
14450 .oindex "&%-bi%&"
14451 This option supplies the name of a command that is run when Exim is called with
14452 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
14453 just the command name, it is not a complete command line. If an argument is
14454 required, it must come from the &%-oA%& command line option.
14455
14456
14457 .option bounce_message_file main string unset
14458 .cindex "bounce message" "customizing"
14459 .cindex "customizing" "bounce message"
14460 This option defines a template file containing paragraphs of text to be used
14461 for constructing bounce messages. Details of the file's contents are given in
14462 chapter &<<CHAPemsgcust>>&. See also &%warn_message_file%&.
14463
14464
14465 .option bounce_message_text main string unset
14466 When this option is set, its contents are included in the default bounce
14467 message immediately after &"This message was created automatically by mail
14468 delivery software."& It is not used if &%bounce_message_file%& is set.
14469
14470 .option bounce_return_body main boolean true
14471 .cindex "bounce message" "including body"
14472 This option controls whether the body of an incoming message is included in a
14473 bounce message when &%bounce_return_message%& is true. The default setting
14474 causes the entire message, both header and body, to be returned (subject to the
14475 value of &%bounce_return_size_limit%&). If this option is false, only the
14476 message header is included. In the case of a non-SMTP message containing an
14477 error that is detected during reception, only those header lines preceding the
14478 point at which the error was detected are returned.
14479 .cindex "bounce message" "including original"
14480
14481 .option bounce_return_linesize_limit main integer 998
14482 .cindex "size" "of bounce lines, limit"
14483 .cindex "bounce message" "line length limit"
14484 .cindex "limit" "bounce message line length"
14485 This option sets a limit in bytes on the line length of messages
14486 that are returned to senders due to delivery problems,
14487 when &%bounce_return_message%& is true.
14488 The default value corresponds to RFC limits.
14489 If the message being returned has lines longer than this value it is
14490 treated as if the &%bounce_return_size_limit%& (below) restriction was exceeded.
14491
14492 The option also applies to bounces returned when an error is detected
14493 during reception of a message.
14494 In this case lines from the original are truncated.
14495
14496 The option does not apply to messages generated by an &(autoreply)& transport.
14497
14498
14499 .option bounce_return_message main boolean true
14500 If this option is set false, none of the original message is included in
14501 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
14502 &%bounce_return_body%&.
14503
14504
14505 .option bounce_return_size_limit main integer 100K
14506 .cindex "size" "of bounce, limit"
14507 .cindex "bounce message" "size limit"
14508 .cindex "limit" "bounce message size"
14509 This option sets a limit in bytes on the size of messages that are returned to
14510 senders as part of bounce messages when &%bounce_return_message%& is true. The
14511 limit should be less than the value of the global &%message_size_limit%& and of
14512 any &%message_size_limit%& settings on transports, to allow for the bounce text
14513 that Exim generates. If this option is set to zero there is no limit.
14514
14515 When the body of any message that is to be included in a bounce message is
14516 greater than the limit, it is truncated, and a comment pointing this out is
14517 added at the top. The actual cutoff may be greater than the value given, owing
14518 to the use of buffering for transferring the message in chunks (typically 8K in
14519 size). The idea is to save bandwidth on those undeliverable 15-megabyte
14520 messages.
14521
14522 .option bounce_sender_authentication main string unset
14523 .cindex "bounce message" "sender authentication"
14524 .cindex "authentication" "bounce message"
14525 .cindex "AUTH" "on bounce message"
14526 This option provides an authenticated sender address that is sent with any
14527 bounce messages generated by Exim that are sent over an authenticated SMTP
14528 connection. A typical setting might be:
14529 .code
14530 bounce_sender_authentication = mailer-daemon@my.domain.example
14531 .endd
14532 which would cause bounce messages to be sent using the SMTP command:
14533 .code
14534 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
14535 .endd
14536 The value of &%bounce_sender_authentication%& must always be a complete email
14537 address.
14538
14539 .option callout_domain_negative_expire main time 3h
14540 .cindex "caching" "callout timeouts"
14541 .cindex "callout" "caching timeouts"
14542 This option specifies the expiry time for negative callout cache data for a
14543 domain. See section &<<SECTcallver>>& for details of callout verification, and
14544 section &<<SECTcallvercache>>& for details of the caching.
14545
14546
14547 .option callout_domain_positive_expire main time 7d
14548 This option specifies the expiry time for positive callout cache data for a
14549 domain. See section &<<SECTcallver>>& for details of callout verification, and
14550 section &<<SECTcallvercache>>& for details of the caching.
14551
14552
14553 .option callout_negative_expire main time 2h
14554 This option specifies the expiry time for negative callout cache data for an
14555 address. See section &<<SECTcallver>>& for details of callout verification, and
14556 section &<<SECTcallvercache>>& for details of the caching.
14557
14558
14559 .option callout_positive_expire main time 24h
14560 This option specifies the expiry time for positive callout cache data for an
14561 address. See section &<<SECTcallver>>& for details of callout verification, and
14562 section &<<SECTcallvercache>>& for details of the caching.
14563
14564
14565 .option callout_random_local_part main string&!! "see below"
14566 This option defines the &"random"& local part that can be used as part of
14567 callout verification. The default value is
14568 .code
14569 $primary_hostname-$tod_epoch-testing
14570 .endd
14571 See section &<<CALLaddparcall>>& for details of how this value is used.
14572
14573
14574 .option check_log_inodes main integer 100
14575 See &%check_spool_space%& below.
14576
14577
14578 .option check_log_space main integer 10M
14579 See &%check_spool_space%& below.
14580
14581 .oindex "&%check_rfc2047_length%&"
14582 .cindex "RFC 2047" "disabling length check"
14583 .option check_rfc2047_length main boolean true
14584 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
14585 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
14586 word; strings to be encoded that exceed this length are supposed to use
14587 multiple encoded words. By default, Exim does not recognize encoded words that
14588 exceed the maximum length. However, it seems that some software, in violation
14589 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
14590 set false, Exim recognizes encoded words of any length.
14591
14592
14593 .option check_spool_inodes main integer 100
14594 See &%check_spool_space%& below.
14595
14596
14597 .option check_spool_space main integer 10M
14598 .cindex "checking disk space"
14599 .cindex "disk space, checking"
14600 .cindex "spool directory" "checking space"
14601 The four &%check_...%& options allow for checking of disk resources before a
14602 message is accepted.
14603
14604 .vindex "&$log_inodes$&"
14605 .vindex "&$log_space$&"
14606 .vindex "&$spool_inodes$&"
14607 .vindex "&$spool_space$&"
14608 When any of these options are nonzero, they apply to all incoming messages. If you
14609 want to apply different checks to different kinds of message, you can do so by
14610 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
14611 &$spool_space$& in an ACL with appropriate additional conditions.
14612
14613
14614 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
14615 either value is greater than zero, for example:
14616 .code
14617 check_spool_space = 100M
14618 check_spool_inodes = 100
14619 .endd
14620 The spool partition is the one that contains the directory defined by
14621 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
14622 transit.
14623
14624 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
14625 files are written if either is greater than zero. These should be set only if
14626 &%log_file_path%& and &%spool_directory%& refer to different partitions.
14627
14628 If there is less space or fewer inodes than requested, Exim refuses to accept
14629 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
14630 error response to the MAIL command. If ESMTP is in use and there was a
14631 SIZE parameter on the MAIL command, its value is added to the
14632 &%check_spool_space%& value, and the check is performed even if
14633 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
14634
14635 The values for &%check_spool_space%& and &%check_log_space%& are held as a
14636 number of kilobytes (though specified in bytes).
14637 If a non-multiple of 1024 is specified, it is rounded up.
14638
14639 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
14640 failure a message is written to stderr and Exim exits with a non-zero code, as
14641 it obviously cannot send an error message of any kind.
14642
14643 There is a slight performance penalty for these checks.
14644 Versions of Exim preceding 4.88 had these disabled by default;
14645 high-rate installations confident they will never run out of resources
14646 may wish to deliberately disable them.
14647
14648 .option chunking_advertise_hosts main "host list&!!" *
14649 .cindex CHUNKING advertisement
14650 .cindex "RFC 3030" "CHUNKING"
14651 The CHUNKING extension (RFC3030) will be advertised in the EHLO message to
14652 these hosts.
14653 Hosts may use the BDAT command as an alternate to DATA.
14654
14655 .option commandline_checks_require_admin main boolean &`false`&
14656 .cindex "restricting access to features"
14657 This option restricts various basic checking features to require an
14658 administrative user.
14659 This affects most of the &%-b*%& options, such as &%-be%&.
14660
14661 .option debug_store main boolean &`false`&
14662 .cindex debugging "memory corruption"
14663 .cindex memory debugging
14664 This option, when true, enables extra checking in Exim's internal memory
14665 management. For use when a memory corruption issue is being investigated,
14666 it should normally be left as default.
14667
14668 .option daemon_smtp_ports main string &`smtp`&
14669 .cindex "port" "for daemon"
14670 .cindex "TCP/IP" "setting listening ports"
14671 This option specifies one or more default SMTP ports on which the Exim daemon
14672 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
14673 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
14674
14675 .option daemon_startup_retries main integer 9
14676 .cindex "daemon startup, retrying"
14677 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
14678 the daemon at startup when it cannot immediately bind a listening socket
14679 (typically because the socket is already in use): &%daemon_startup_retries%&
14680 defines the number of retries after the first failure, and
14681 &%daemon_startup_sleep%& defines the length of time to wait between retries.
14682
14683 .option daemon_startup_sleep main time 30s
14684 See &%daemon_startup_retries%&.
14685
14686 .option delay_warning main "time list" 24h
14687 .cindex "warning of delay"
14688 .cindex "delay warning, specifying"
14689 .cindex "queue" "delay warning"
14690 When a message is delayed, Exim sends a warning message to the sender at
14691 intervals specified by this option. The data is a colon-separated list of times
14692 after which to send warning messages. If the value of the option is an empty
14693 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
14694 message has been on the queue for longer than the last time, the last interval
14695 between the times is used to compute subsequent warning times. For example,
14696 with
14697 .code
14698 delay_warning = 4h:8h:24h
14699 .endd
14700 the first message is sent after 4 hours, the second after 8 hours, and
14701 the third one after 24 hours. After that, messages are sent every 16 hours,
14702 because that is the interval between the last two times on the list. If you set
14703 just one time, it specifies the repeat interval. For example, with:
14704 .code
14705 delay_warning = 6h
14706 .endd
14707 messages are repeated every six hours. To stop warnings after a given time, set
14708 a very large time at the end of the list. For example:
14709 .code
14710 delay_warning = 2h:12h:99d
14711 .endd
14712 Note that the option is only evaluated at the time a delivery attempt fails,
14713 which depends on retry and queue-runner configuration.
14714 Typically retries will be configured more frequently than warning messages.
14715
14716 .option delay_warning_condition main string&!! "see below"
14717 .vindex "&$domain$&"
14718 The string is expanded at the time a warning message might be sent. If all the
14719 deferred addresses have the same domain, it is set in &$domain$& during the
14720 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
14721 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
14722 &"false"& (the comparison being done caselessly) then the warning message is
14723 not sent. The default is:
14724 .code
14725 delay_warning_condition = ${if or {\
14726 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
14727 { match{$h_precedence:}{(?i)bulk|list|junk} }\
14728 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
14729 } {no}{yes}}
14730 .endd
14731 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
14732 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
14733 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
14734 &"auto-replied"& in an &'Auto-Submitted:'& header.
14735
14736 .option deliver_drop_privilege main boolean false
14737 .cindex "unprivileged delivery"
14738 .cindex "delivery" "unprivileged"
14739 If this option is set true, Exim drops its root privilege at the start of a
14740 delivery process, and runs as the Exim user throughout. This severely restricts
14741 the kinds of local delivery that are possible, but is viable in certain types
14742 of configuration. There is a discussion about the use of root privilege in
14743 chapter &<<CHAPsecurity>>&.
14744
14745 .option deliver_queue_load_max main fixed-point unset
14746 .cindex "load average"
14747 .cindex "queue runner" "abandoning"
14748 When this option is set, a queue run is abandoned if the system load average
14749 becomes greater than the value of the option. The option has no effect on
14750 ancient operating systems on which Exim cannot determine the load average.
14751 See also &%queue_only_load%& and &%smtp_load_reserve%&.
14752
14753
14754 .option delivery_date_remove main boolean true
14755 .cindex "&'Delivery-date:'& header line"
14756 Exim's transports have an option for adding a &'Delivery-date:'& header to a
14757 message when it is delivered, in exactly the same way as &'Return-path:'& is
14758 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
14759 should not be present in incoming messages, and this option causes them to be
14760 removed at the time the message is received, to avoid any problems that might
14761 occur when a delivered message is subsequently sent on to some other recipient.
14762
14763 .option disable_fsync main boolean false
14764 .cindex "&[fsync()]&, disabling"
14765 This option is available only if Exim was built with the compile-time option
14766 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
14767 a runtime configuration generates an &"unknown option"& error. You should not
14768 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
14769 really, really, really understand what you are doing. &'No pre-compiled
14770 distributions of Exim should ever make this option available.'&
14771
14772 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
14773 updated files' data to be written to disc before continuing. Unexpected events
14774 such as crashes and power outages may cause data to be lost or scrambled.
14775 Here be Dragons. &*Beware.*&
14776
14777
14778 .option disable_ipv6 main boolean false
14779 .cindex "IPv6" "disabling"
14780 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
14781 activities take place. AAAA records are never looked up, and any IPv6 addresses
14782 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
14783 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14784 to handle IPv6 literal addresses.
14785
14786
14787 .option dkim_verify_signers main "domain list&!!" $dkim_signers
14788 .cindex DKIM "controlling calls to the ACL"
14789 This option gives a list of DKIM domains for which the DKIM ACL is run.
14790 It is expanded after the message is received; by default it runs
14791 the ACL once for each signature in the message.
14792 See section &<<SECDKIMVFY>>&.
14793
14794
14795 .option dns_again_means_nonexist main "domain list&!!" unset
14796 .cindex "DNS" "&""try again""& response; overriding"
14797 DNS lookups give a &"try again"& response for the DNS errors
14798 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
14799 keep trying to deliver a message, or to give repeated temporary errors to
14800 incoming mail. Sometimes the effect is caused by a badly set up name server and
14801 may persist for a long time. If a domain which exhibits this problem matches
14802 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
14803 This option should be used with care. You can make it apply to reverse lookups
14804 by a setting such as this:
14805 .code
14806 dns_again_means_nonexist = *.in-addr.arpa
14807 .endd
14808 This option applies to all DNS lookups that Exim does. It also applies when the
14809 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
14810 since these are most likely to be caused by DNS lookup problems. The
14811 &(dnslookup)& router has some options of its own for controlling what happens
14812 when lookups for MX or SRV records give temporary errors. These more specific
14813 options are applied after this global option.
14814
14815 .option dns_check_names_pattern main string "see below"
14816 .cindex "DNS" "pre-check of name syntax"
14817 When this option is set to a non-empty string, it causes Exim to check domain
14818 names for characters that are not allowed in host names before handing them to
14819 the DNS resolver, because some resolvers give temporary errors for names that
14820 contain unusual characters. If a domain name contains any unwanted characters,
14821 a &"not found"& result is forced, and the resolver is not called. The check is
14822 done by matching the domain name against a regular expression, which is the
14823 value of this option. The default pattern is
14824 .code
14825 dns_check_names_pattern = \
14826 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
14827 .endd
14828 which permits only letters, digits, slashes, and hyphens in components, but
14829 they must start and end with a letter or digit. Slashes are not, in fact,
14830 permitted in host names, but they are found in certain NS records (which can be
14831 accessed in Exim by using a &%dnsdb%& lookup). If you set
14832 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
14833 empty string.
14834
14835 .option dns_csa_search_limit main integer 5
14836 This option controls the depth of parental searching for CSA SRV records in the
14837 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
14838
14839 .option dns_csa_use_reverse main boolean true
14840 This option controls whether or not an IP address, given as a CSA domain, is
14841 reversed and looked up in the reverse DNS, as described in more detail in
14842 section &<<SECTverifyCSA>>&.
14843
14844 .new
14845 .option dns_cname_loops main integer 1
14846 .cindex DNS "CNAME following"
14847 This option controls the following of CNAME chains, needed if the resolver does
14848 not do it internally.
14849 As of 2018 most should, and the default can be left.
14850 If you have an ancient one, a value of 10 is likely needed.
14851
14852 The default value of one CNAME-follow is needed
14853 thanks to the observed return for an MX request,
14854 given no MX presence but a CNAME to an A, of the CNAME.
14855 .wen
14856
14857
14858 .option dns_dnssec_ok main integer -1
14859 .cindex "DNS" "resolver options"
14860 .cindex "DNS" "DNSSEC"
14861 If this option is set to a non-negative number then Exim will initialise the
14862 DNS resolver library to either use or not use DNSSEC, overriding the system
14863 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
14864
14865 If the resolver library does not support DNSSEC then this option has no effect.
14866
14867
14868 .option dns_ipv4_lookup main "domain list&!!" unset
14869 .cindex "IPv6" "DNS lookup for AAAA records"
14870 .cindex "DNS" "IPv6 lookup for AAAA records"
14871 .cindex DNS "IPv6 disabling"
14872 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
14873 looks for IPv6 address records (AAAA records) as well as IPv4 address records
14874 (A records) when trying to find IP addresses for hosts, unless the host's
14875 domain matches this list.
14876
14877 This is a fudge to help with name servers that give big delays or otherwise do
14878 not work for the AAAA record type. In due course, when the world's name
14879 servers have all been upgraded, there should be no need for this option.
14880
14881
14882 .option dns_retrans main time 0s
14883 .cindex "DNS" "resolver options"
14884 .cindex timeout "dns lookup"
14885 .cindex "DNS" timeout
14886 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
14887 retransmission and retry parameters for DNS lookups. Values of zero (the
14888 defaults) leave the system default settings unchanged. The first value is the
14889 time between retries, and the second is the number of retries. It isn't
14890 totally clear exactly how these settings affect the total time a DNS lookup may
14891 take. I haven't found any documentation about timeouts on DNS lookups; these
14892 parameter values are available in the external resolver interface structure,
14893 but nowhere does it seem to describe how they are used or what you might want
14894 to set in them.
14895 See also the &%slow_lookup_log%& option.
14896
14897
14898 .option dns_retry main integer 0
14899 See &%dns_retrans%& above.
14900
14901
14902 .option dns_trust_aa main "domain list&!!" unset
14903 .cindex "DNS" "resolver options"
14904 .cindex "DNS" "DNSSEC"
14905 If this option is set then lookup results marked with the AA bit
14906 (Authoritative Answer) are trusted the same way as if they were
14907 DNSSEC-verified. The authority section's name of the answer must
14908 match with this expanded domain list.
14909
14910 Use this option only if you talk directly to a resolver that is
14911 authoritative for some zones and does not set the AD (Authentic Data)
14912 bit in the answer. Some DNS servers may have an configuration option to
14913 mark the answers from their own zones as verified (they set the AD bit).
14914 Others do not have this option. It is considered as poor practice using
14915 a resolver that is an authoritative server for some zones.
14916
14917 Use this option only if you really have to (e.g. if you want
14918 to use DANE for remote delivery to a server that is listed in the DNS
14919 zones that your resolver is authoritative for).
14920
14921 If the DNS answer packet has the AA bit set and contains resource record
14922 in the answer section, the name of the first NS record appearing in the
14923 authority section is compared against the list. If the answer packet is
14924 authoritative but the answer section is empty, the name of the first SOA
14925 record in the authoritative section is used instead.
14926
14927 .cindex "DNS" "resolver options"
14928 .option dns_use_edns0 main integer -1
14929 .cindex "DNS" "resolver options"
14930 .cindex "DNS" "EDNS0"
14931 .cindex "DNS" "OpenBSD
14932 If this option is set to a non-negative number then Exim will initialise the
14933 DNS resolver library to either use or not use EDNS0 extensions, overriding
14934 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
14935 on.
14936
14937 If the resolver library does not support EDNS0 then this option has no effect.
14938
14939 OpenBSD's asr resolver routines are known to ignore the EDNS0 option; this
14940 means that DNSSEC will not work with Exim on that platform either, unless Exim
14941 is linked against an alternative DNS client library.
14942
14943
14944 .option drop_cr main boolean false
14945 This is an obsolete option that is now a no-op. It used to affect the way Exim
14946 handled CR and LF characters in incoming messages. What happens now is
14947 described in section &<<SECTlineendings>>&.
14948
14949 .option dsn_advertise_hosts main "host list&!!" unset
14950 .cindex "bounce messages" "success"
14951 .cindex "DSN" "success"
14952 .cindex "Delivery Status Notification" "success"
14953 DSN extensions (RFC3461) will be advertised in the EHLO message to,
14954 and accepted from, these hosts.
14955 Hosts may use the NOTIFY and ENVID options on RCPT TO commands,
14956 and RET and ORCPT options on MAIL FROM commands.
14957 A NOTIFY=SUCCESS option requests success-DSN messages.
14958 A NOTIFY= option with no argument requests that no delay or failure DSNs
14959 are sent.
14960
14961 .option dsn_from main "string&!!" "see below"
14962 .cindex "&'From:'& header line" "in bounces"
14963 .cindex "bounce messages" "&'From:'& line, specifying"
14964 This option can be used to vary the contents of &'From:'& header lines in
14965 bounces and other automatically generated messages (&"Delivery Status
14966 Notifications"& &-- hence the name of the option). The default setting is:
14967 .code
14968 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
14969 .endd
14970 The value is expanded every time it is needed. If the expansion fails, a
14971 panic is logged, and the default value is used.
14972
14973 .option envelope_to_remove main boolean true
14974 .cindex "&'Envelope-to:'& header line"
14975 Exim's transports have an option for adding an &'Envelope-to:'& header to a
14976 message when it is delivered, in exactly the same way as &'Return-path:'& is
14977 handled. &'Envelope-to:'& records the original recipient address from the
14978 message's envelope that caused the delivery to happen. Such headers should not
14979 be present in incoming messages, and this option causes them to be removed at
14980 the time the message is received, to avoid any problems that might occur when a
14981 delivered message is subsequently sent on to some other recipient.
14982
14983
14984 .option errors_copy main "string list&!!" unset
14985 .cindex "bounce message" "copy to other address"
14986 .cindex "copy of bounce message"
14987 Setting this option causes Exim to send bcc copies of bounce messages that it
14988 generates to other addresses. &*Note*&: This does not apply to bounce messages
14989 coming from elsewhere. The value of the option is a colon-separated list of
14990 items. Each item consists of a pattern, terminated by white space, followed by
14991 a comma-separated list of email addresses. If a pattern contains spaces, it
14992 must be enclosed in double quotes.
14993
14994 Each pattern is processed in the same way as a single item in an address list
14995 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
14996 the bounce message, the message is copied to the addresses on the list. The
14997 items are scanned in order, and once a matching one is found, no further items
14998 are examined. For example:
14999 .code
15000 errors_copy = spqr@mydomain postmaster@mydomain.example :\
15001 rqps@mydomain hostmaster@mydomain.example,\
15002 postmaster@mydomain.example
15003 .endd
15004 .vindex "&$domain$&"
15005 .vindex "&$local_part$&"
15006 The address list is expanded before use. The expansion variables &$local_part$&
15007 and &$domain$& are set from the original recipient of the error message, and if
15008 there was any wildcard matching in the pattern, the expansion
15009 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
15010 variables &$0$&, &$1$&, etc. are set in the normal way.
15011
15012
15013 .option errors_reply_to main string unset
15014 .cindex "bounce message" "&'Reply-to:'& in"
15015 By default, Exim's bounce and delivery warning messages contain the header line
15016 .display
15017 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
15018 .endd
15019 .oindex &%quota_warn_message%&
15020 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
15021 A warning message that is generated by the &%quota_warn_message%& option in an
15022 &(appendfile)& transport may contain its own &'From:'& header line that
15023 overrides the default.
15024
15025 Experience shows that people reply to bounce messages. If the
15026 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
15027 and warning messages. For example:
15028 .code
15029 errors_reply_to = postmaster@my.domain.example
15030 .endd
15031 The value of the option is not expanded. It must specify a valid RFC 2822
15032 address. However, if a warning message that is generated by the
15033 &%quota_warn_message%& option in an &(appendfile)& transport contain its
15034 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
15035 not used.
15036
15037
15038 .option event_action main string&!! unset
15039 .cindex events
15040 This option declares a string to be expanded for Exim's events mechanism.
15041 For details see chapter &<<CHAPevents>>&.
15042
15043
15044 .option exim_group main string "compile-time configured"
15045 .cindex "gid (group id)" "Exim's own"
15046 .cindex "Exim group"
15047 This option changes the gid under which Exim runs when it gives up root
15048 privilege. The default value is compiled into the binary. The value of this
15049 option is used only when &%exim_user%& is also set. Unless it consists entirely
15050 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
15051 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
15052 security issues.
15053
15054
15055 .option exim_path main string "see below"
15056 .cindex "Exim binary, path name"
15057 This option specifies the path name of the Exim binary, which is used when Exim
15058 needs to re-exec itself. The default is set up to point to the file &'exim'& in
15059 the directory configured at compile time by the BIN_DIRECTORY setting. It
15060 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
15061 other place.
15062 &*Warning*&: Do not use a macro to define the value of this option, because
15063 you will break those Exim utilities that scan the configuration file to find
15064 where the binary is. (They then use the &%-bP%& option to extract option
15065 settings such as the value of &%spool_directory%&.)
15066
15067
15068 .option exim_user main string "compile-time configured"
15069 .cindex "uid (user id)" "Exim's own"
15070 .cindex "Exim user"
15071 This option changes the uid under which Exim runs when it gives up root
15072 privilege. The default value is compiled into the binary. Ownership of the run
15073 time configuration file and the use of the &%-C%& and &%-D%& command line
15074 options is checked against the values in the binary, not what is set here.
15075
15076 Unless it consists entirely of digits, the string is looked up using
15077 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
15078 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
15079 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
15080
15081
15082 .option extra_local_interfaces main "string list" unset
15083 This option defines network interfaces that are to be considered local when
15084 routing, but which are not used for listening by the daemon. See section
15085 &<<SECTreclocipadd>>& for details.
15086
15087
15088 . Allow this long option name to split; give it unsplit as a fifth argument
15089 . for the automatic .oindex that is generated by .option.
15090
15091 .option "extract_addresses_remove_arguments" main boolean true &&&
15092 extract_addresses_remove_arguments
15093 .oindex "&%-t%&"
15094 .cindex "command line" "addresses with &%-t%&"
15095 .cindex "Sendmail compatibility" "&%-t%& option"
15096 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
15097 are present on the command line when the &%-t%& option is used to build an
15098 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
15099 line addresses are removed from the recipients list. This is also how Smail
15100 behaves. However, other Sendmail documentation (the O'Reilly book) states that
15101 command line addresses are added to those obtained from the header lines. When
15102 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
15103 argument headers. If it is set false, Exim adds rather than removes argument
15104 addresses.
15105
15106
15107 .option finduser_retries main integer 0
15108 .cindex "NIS, retrying user lookups"
15109 On systems running NIS or other schemes in which user and group information is
15110 distributed from a remote system, there can be times when &[getpwnam()]& and
15111 related functions fail, even when given valid data, because things time out.
15112 Unfortunately these failures cannot be distinguished from genuine &"not found"&
15113 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
15114 many extra times to find a user or a group, waiting for one second between
15115 retries.
15116
15117 .cindex "&_/etc/passwd_&" "multiple reading of"
15118 You should not set this option greater than zero if your user information is in
15119 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
15120 search the file multiple times for non-existent users, and also cause delay.
15121
15122
15123
15124 .option freeze_tell main "string list, comma separated" unset
15125 .cindex "freezing messages" "sending a message when freezing"
15126 On encountering certain errors, or when configured to do so in a system filter,
15127 ACL, or special router, Exim freezes a message. This means that no further
15128 delivery attempts take place until an administrator thaws the message, or the
15129 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
15130 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
15131 warning message whenever it freezes something, unless the message it is
15132 freezing is a locally-generated bounce message. (Without this exception there
15133 is the possibility of looping.) The warning message is sent to the addresses
15134 supplied as the comma-separated value of this option. If several of the
15135 message's addresses cause freezing, only a single message is sent. If the
15136 freezing was automatic, the reason(s) for freezing can be found in the message
15137 log. If you configure freezing in a filter or ACL, you must arrange for any
15138 logging that you require.
15139
15140
15141 .option gecos_name main string&!! unset
15142 .cindex "HP-UX"
15143 .cindex "&""gecos""& field, parsing"
15144 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
15145 password file to hold other information in addition to users' real names. Exim
15146 looks up this field for use when it is creating &'Sender:'& or &'From:'&
15147 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
15148 of the field are used unchanged, except that, if an ampersand is encountered,
15149 it is replaced by the user's login name with the first character forced to
15150 upper case, since this is a convention that is observed on many systems.
15151
15152 When these options are set, &%gecos_pattern%& is treated as a regular
15153 expression that is to be applied to the field (again with && replaced by the
15154 login name), and if it matches, &%gecos_name%& is expanded and used as the
15155 user's name.
15156
15157 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
15158 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
15159 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
15160 name terminates at the first comma, the following can be used:
15161 .code
15162 gecos_pattern = ([^,]*)
15163 gecos_name = $1
15164 .endd
15165
15166 .option gecos_pattern main string unset
15167 See &%gecos_name%& above.
15168
15169
15170 .option gnutls_compat_mode main boolean unset
15171 This option controls whether GnuTLS is used in compatibility mode in an Exim
15172 server. This reduces security slightly, but improves interworking with older
15173 implementations of TLS.
15174
15175
15176 .option gnutls_allow_auto_pkcs11 main boolean unset
15177 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
15178 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
15179
15180 See
15181 &url(http://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
15182 for documentation.
15183
15184
15185
15186 .option headers_charset main string "see below"
15187 This option sets a default character set for translating from encoded MIME
15188 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
15189 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
15190 ultimate default is ISO-8859-1. For more details see the description of header
15191 insertions in section &<<SECTexpansionitems>>&.
15192
15193
15194
15195 .option header_maxsize main integer "see below"
15196 .cindex "header section" "maximum size of"
15197 .cindex "limit" "size of message header section"
15198 This option controls the overall maximum size of a message's header
15199 section. The default is the value of HEADER_MAXSIZE in
15200 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
15201 sections are rejected.
15202
15203
15204 .option header_line_maxsize main integer 0
15205 .cindex "header lines" "maximum size of"
15206 .cindex "limit" "size of one header line"
15207 This option limits the length of any individual header line in a message, after
15208 all the continuations have been joined together. Messages with individual
15209 header lines that are longer than the limit are rejected. The default value of
15210 zero means &"no limit"&.
15211
15212
15213
15214
15215 .option helo_accept_junk_hosts main "host list&!!" unset
15216 .cindex "HELO" "accepting junk data"
15217 .cindex "EHLO" "accepting junk data"
15218 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
15219 mail, and gives an error response for invalid data. Unfortunately, there are
15220 some SMTP clients that send syntactic junk. They can be accommodated by setting
15221 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
15222 if you want to do semantic checking.
15223 See also &%helo_allow_chars%& for a way of extending the permitted character
15224 set.
15225
15226
15227 .option helo_allow_chars main string unset
15228 .cindex "HELO" "underscores in"
15229 .cindex "EHLO" "underscores in"
15230 .cindex "underscore in EHLO/HELO"
15231 This option can be set to a string of rogue characters that are permitted in
15232 all EHLO and HELO names in addition to the standard letters, digits,
15233 hyphens, and dots. If you really must allow underscores, you can set
15234 .code
15235 helo_allow_chars = _
15236 .endd
15237 Note that the value is one string, not a list.
15238
15239
15240 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
15241 .cindex "HELO" "forcing reverse lookup"
15242 .cindex "EHLO" "forcing reverse lookup"
15243 If the domain given by a client in a HELO or EHLO command matches this
15244 list, a reverse lookup is done in order to establish the host's true name. The
15245 default forces a lookup if the client host gives the server's name or any of
15246 its IP addresses (in brackets), something that broken clients have been seen to
15247 do.
15248
15249
15250 .option helo_try_verify_hosts main "host list&!!" unset
15251 .cindex "HELO verifying" "optional"
15252 .cindex "EHLO" "verifying, optional"
15253 By default, Exim just checks the syntax of HELO and EHLO commands (see
15254 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
15255 to do more extensive checking of the data supplied by these commands. The ACL
15256 condition &`verify = helo`& is provided to make this possible.
15257 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
15258 to force the check to occur. From release 4.53 onwards, this is no longer
15259 necessary. If the check has not been done before &`verify = helo`& is
15260 encountered, it is done at that time. Consequently, this option is obsolete.
15261 Its specification is retained here for backwards compatibility.
15262
15263 When an EHLO or HELO command is received, if the calling host matches
15264 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
15265 EHLO command either:
15266
15267 .ilist
15268 is an IP literal matching the calling address of the host, or
15269 .next
15270 .cindex "DNS" "reverse lookup"
15271 .cindex "reverse DNS lookup"
15272 matches the host name that Exim obtains by doing a reverse lookup of the
15273 calling host address, or
15274 .next
15275 when looked up in DNS yields the calling host address.
15276 .endlist
15277
15278 However, the EHLO or HELO command is not rejected if any of the checks
15279 fail. Processing continues, but the result of the check is remembered, and can
15280 be detected later in an ACL by the &`verify = helo`& condition.
15281
15282 If DNS was used for successful verification, the variable
15283 .cindex "DNS" "DNSSEC"
15284 &$helo_verify_dnssec$& records the DNSSEC status of the lookups.
15285
15286 .option helo_verify_hosts main "host list&!!" unset
15287 .cindex "HELO verifying" "mandatory"
15288 .cindex "EHLO" "verifying, mandatory"
15289 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
15290 backwards compatibility. For hosts that match this option, Exim checks the host
15291 name given in the HELO or EHLO in the same way as for
15292 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
15293 rejected with a 550 error, and entries are written to the main and reject logs.
15294 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
15295 error.
15296
15297 .option hold_domains main "domain list&!!" unset
15298 .cindex "domain" "delaying delivery"
15299 .cindex "delivery" "delaying certain domains"
15300 This option allows mail for particular domains to be held on the queue
15301 manually. The option is overridden if a message delivery is forced with the
15302 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
15303 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
15304 item in &%hold_domains%&, no routing or delivery for that address is done, and
15305 it is deferred every time the message is looked at.
15306
15307 This option is intended as a temporary operational measure for delaying the
15308 delivery of mail while some problem is being sorted out, or some new
15309 configuration tested. If you just want to delay the processing of some
15310 domains until a queue run occurs, you should use &%queue_domains%& or
15311 &%queue_smtp_domains%&, not &%hold_domains%&.
15312
15313 A setting of &%hold_domains%& does not override Exim's code for removing
15314 messages from the queue if they have been there longer than the longest retry
15315 time in any retry rule. If you want to hold messages for longer than the normal
15316 retry times, insert a dummy retry rule with a long retry time.
15317
15318
15319 .option host_lookup main "host list&!!" unset
15320 .cindex "host name" "lookup, forcing"
15321 Exim does not look up the name of a calling host from its IP address unless it
15322 is required to compare against some host list, or the host matches
15323 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
15324 option (which normally contains IP addresses rather than host names). The
15325 default configuration file contains
15326 .code
15327 host_lookup = *
15328 .endd
15329 which causes a lookup to happen for all hosts. If the expense of these lookups
15330 is felt to be too great, the setting can be changed or removed.
15331
15332 After a successful reverse lookup, Exim does a forward lookup on the name it
15333 has obtained, to verify that it yields the IP address that it started with. If
15334 this check fails, Exim behaves as if the name lookup failed.
15335
15336 .vindex "&$host_lookup_failed$&"
15337 .vindex "&$sender_host_name$&"
15338 After any kind of failure, the host name (in &$sender_host_name$&) remains
15339 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
15340 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
15341 &`verify = reverse_host_lookup`& in ACLs.
15342
15343
15344 .option host_lookup_order main "string list" &`bydns:byaddr`&
15345 This option specifies the order of different lookup methods when Exim is trying
15346 to find a host name from an IP address. The default is to do a DNS lookup
15347 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
15348 if that fails. You can change the order of these lookups, or omit one entirely,
15349 if you want.
15350
15351 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
15352 multiple PTR records in the DNS and the IP address is not listed in
15353 &_/etc/hosts_&. Different operating systems give different results in this
15354 case. That is why the default tries a DNS lookup first.
15355
15356
15357
15358 .option host_reject_connection main "host list&!!" unset
15359 .cindex "host" "rejecting connections from"
15360 If this option is set, incoming SMTP calls from the hosts listed are rejected
15361 as soon as the connection is made.
15362 This option is obsolete, and retained only for backward compatibility, because
15363 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
15364 connections immediately.
15365
15366 The ability to give an immediate rejection (either by this option or using an
15367 ACL) is provided for use in unusual cases. Many hosts will just try again,
15368 sometimes without much delay. Normally, it is better to use an ACL to reject
15369 incoming messages at a later stage, such as after RCPT commands. See
15370 chapter &<<CHAPACL>>&.
15371
15372
15373 .option hosts_connection_nolog main "host list&!!" unset
15374 .cindex "host" "not logging connections from"
15375 This option defines a list of hosts for which connection logging does not
15376 happen, even though the &%smtp_connection%& log selector is set. For example,
15377 you might want not to log SMTP connections from local processes, or from
15378 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
15379 the daemon; you should therefore strive to restrict its value to a short inline
15380 list of IP addresses and networks. To disable logging SMTP connections from
15381 local processes, you must create a host list with an empty item. For example:
15382 .code
15383 hosts_connection_nolog = :
15384 .endd
15385 If the &%smtp_connection%& log selector is not set, this option has no effect.
15386
15387
15388
15389 .option hosts_proxy main "host list&!!" unset
15390 .cindex proxy "proxy protocol"
15391 This option enables use of Proxy Protocol proxies for incoming
15392 connections. For details see section &<<SECTproxyInbound>>&.
15393
15394
15395 .option hosts_treat_as_local main "domain list&!!" unset
15396 .cindex "local host" "domains treated as"
15397 .cindex "host" "treated as local"
15398 If this option is set, any host names that match the domain list are treated as
15399 if they were the local host when Exim is scanning host lists obtained from MX
15400 records
15401 or other sources. Note that the value of this option is a domain list, not a
15402 host list, because it is always used to check host names, not IP addresses.
15403
15404 This option also applies when Exim is matching the special items
15405 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
15406 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
15407 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
15408 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
15409 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
15410 interfaces and recognizing the local host.
15411
15412
15413 .option ibase_servers main "string list" unset
15414 .cindex "InterBase" "server list"
15415 This option provides a list of InterBase servers and associated connection data,
15416 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
15417 The option is available only if Exim has been built with InterBase support.
15418
15419
15420
15421 .option ignore_bounce_errors_after main time 10w
15422 .cindex "bounce message" "discarding"
15423 .cindex "discarding bounce message"
15424 This option affects the processing of bounce messages that cannot be delivered,
15425 that is, those that suffer a permanent delivery failure. (Bounce messages that
15426 suffer temporary delivery failures are of course retried in the usual way.)
15427
15428 After a permanent delivery failure, bounce messages are frozen,
15429 because there is no sender to whom they can be returned. When a frozen bounce
15430 message has been on the queue for more than the given time, it is unfrozen at
15431 the next queue run, and a further delivery is attempted. If delivery fails
15432 again, the bounce message is discarded. This makes it possible to keep failed
15433 bounce messages around for a shorter time than the normal maximum retry time
15434 for frozen messages. For example,
15435 .code
15436 ignore_bounce_errors_after = 12h
15437 .endd
15438 retries failed bounce message deliveries after 12 hours, discarding any further
15439 failures. If the value of this option is set to a zero time period, bounce
15440 failures are discarded immediately. Setting a very long time (as in the default
15441 value) has the effect of disabling this option. For ways of automatically
15442 dealing with other kinds of frozen message, see &%auto_thaw%& and
15443 &%timeout_frozen_after%&.
15444
15445
15446 .option ignore_fromline_hosts main "host list&!!" unset
15447 .cindex "&""From""& line"
15448 .cindex "UUCP" "&""From""& line"
15449 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
15450 the headers of a message. By default this is treated as the start of the
15451 message's body, which means that any following headers are not recognized as
15452 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
15453 match those hosts that insist on sending it. If the sender is actually a local
15454 process rather than a remote host, and is using &%-bs%& to inject the messages,
15455 &%ignore_fromline_local%& must be set to achieve this effect.
15456
15457
15458 .option ignore_fromline_local main boolean false
15459 See &%ignore_fromline_hosts%& above.
15460
15461 .option keep_environment main "string list" unset
15462 .cindex "environment" "values from"
15463 This option contains a string list of environment variables to keep.
15464 You have to trust these variables or you have to be sure that
15465 these variables do not impose any security risk. Keep in mind that
15466 during the startup phase Exim is running with an effective UID 0 in most
15467 installations. As the default value is an empty list, the default
15468 environment for using libraries, running embedded Perl code, or running
15469 external binaries is empty, and does not not even contain PATH or HOME.
15470
15471 Actually the list is interpreted as a list of patterns
15472 (&<<SECTlistexpand>>&), except that it is not expanded first.
15473
15474 WARNING: Macro substitution is still done first, so having a macro
15475 FOO and having FOO_HOME in your &%keep_environment%& option may have
15476 unexpected results. You may work around this using a regular expression
15477 that does not match the macro name: ^[F]OO_HOME$.
15478
15479 Current versions of Exim issue a warning during startup if you do not mention
15480 &%keep_environment%& in your runtime configuration file and if your
15481 current environment is not empty. Future versions may not issue that warning
15482 anymore.
15483
15484 See the &%add_environment%& main config option for a way to set
15485 environment variables to a fixed value. The environment for &(pipe)&
15486 transports is handled separately, see section &<<SECTpipeenv>>& for
15487 details.
15488
15489
15490 .option keep_malformed main time 4d
15491 This option specifies the length of time to keep messages whose spool files
15492 have been corrupted in some way. This should, of course, never happen. At the
15493 next attempt to deliver such a message, it gets removed. The incident is
15494 logged.
15495
15496
15497 .option ldap_ca_cert_dir main string unset
15498 .cindex "LDAP", "TLS CA certificate directory"
15499 .cindex certificate "directory for LDAP"
15500 This option indicates which directory contains CA certificates for verifying
15501 a TLS certificate presented by an LDAP server.
15502 While Exim does not provide a default value, your SSL library may.
15503 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
15504 and constrained to be a directory.
15505
15506
15507 .option ldap_ca_cert_file main string unset
15508 .cindex "LDAP", "TLS CA certificate file"
15509 .cindex certificate "file for LDAP"
15510 This option indicates which file contains CA certificates for verifying
15511 a TLS certificate presented by an LDAP server.
15512 While Exim does not provide a default value, your SSL library may.
15513 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
15514 and constrained to be a file.
15515
15516
15517 .option ldap_cert_file main string unset
15518 .cindex "LDAP" "TLS client certificate file"
15519 .cindex certificate "file for LDAP"
15520 This option indicates which file contains an TLS client certificate which
15521 Exim should present to the LDAP server during TLS negotiation.
15522 Should be used together with &%ldap_cert_key%&.
15523
15524
15525 .option ldap_cert_key main string unset
15526 .cindex "LDAP" "TLS client key file"
15527 .cindex certificate "key for LDAP"
15528 This option indicates which file contains the secret/private key to use
15529 to prove identity to the LDAP server during TLS negotiation.
15530 Should be used together with &%ldap_cert_file%&, which contains the
15531 identity to be proven.
15532
15533
15534 .option ldap_cipher_suite main string unset
15535 .cindex "LDAP" "TLS cipher suite"
15536 This controls the TLS cipher-suite negotiation during TLS negotiation with
15537 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
15538 cipher-suite options with OpenSSL (as used by LDAP client libraries).
15539
15540
15541 .option ldap_default_servers main "string list" unset
15542 .cindex "LDAP" "default servers"
15543 This option provides a list of LDAP servers which are tried in turn when an
15544 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
15545 details of LDAP queries. This option is available only when Exim has been built
15546 with LDAP support.
15547
15548
15549 .option ldap_require_cert main string unset.
15550 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
15551 This should be one of the values "hard", "demand", "allow", "try" or "never".
15552 A value other than one of these is interpreted as "never".
15553 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
15554 Although Exim does not set a default, the LDAP library probably defaults
15555 to hard/demand.
15556
15557
15558 .option ldap_start_tls main boolean false
15559 .cindex "LDAP" "whether or not to negotiate TLS"
15560 If set, Exim will attempt to negotiate TLS with the LDAP server when
15561 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
15562 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
15563 of SSL-on-connect.
15564 In the event of failure to negotiate TLS, the action taken is controlled
15565 by &%ldap_require_cert%&.
15566 This option is ignored for &`ldapi`& connections.
15567
15568
15569 .option ldap_version main integer unset
15570 .cindex "LDAP" "protocol version, forcing"
15571 This option can be used to force Exim to set a specific protocol version for
15572 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
15573 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
15574 the LDAP headers; otherwise it is 2. This option is available only when Exim
15575 has been built with LDAP support.
15576
15577
15578
15579 .option local_from_check main boolean true
15580 .cindex "&'Sender:'& header line" "disabling addition of"
15581 .cindex "&'From:'& header line" "disabling checking of"
15582 When a message is submitted locally (that is, not over a TCP/IP connection) by
15583 an untrusted user, Exim removes any existing &'Sender:'& header line, and
15584 checks that the &'From:'& header line matches the login of the calling user and
15585 the domain specified by &%qualify_domain%&.
15586
15587 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
15588 locally submitted message is automatically qualified by Exim, unless the
15589 &%-bnq%& command line option is used.
15590
15591 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
15592 on the local part. If the &'From:'& header line does not match, Exim adds a
15593 &'Sender:'& header with an address constructed from the calling user's login
15594 and the default qualify domain.
15595
15596 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
15597 and no &'Sender:'& header is ever added. If, in addition, you want to retain
15598 &'Sender:'& header lines supplied by untrusted users, you must also set
15599 &%local_sender_retain%& to be true.
15600
15601 .cindex "envelope sender"
15602 These options affect only the header lines in the message. The envelope sender
15603 is still forced to be the login id at the qualify domain unless
15604 &%untrusted_set_sender%& permits the user to supply an envelope sender.
15605
15606 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
15607 request similar header line checking. See section &<<SECTthesenhea>>&, which
15608 has more details about &'Sender:'& processing.
15609
15610
15611
15612
15613 .option local_from_prefix main string unset
15614 When Exim checks the &'From:'& header line of locally submitted messages for
15615 matching the login id (see &%local_from_check%& above), it can be configured to
15616 ignore certain prefixes and suffixes in the local part of the address. This is
15617 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
15618 appropriate lists, in the same form as the &%local_part_prefix%& and
15619 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
15620 example, if
15621 .code
15622 local_from_prefix = *-
15623 .endd
15624 is set, a &'From:'& line containing
15625 .code
15626 From: anything-user@your.domain.example
15627 .endd
15628 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
15629 matches the actual sender address that is constructed from the login name and
15630 qualify domain.
15631
15632
15633 .option local_from_suffix main string unset
15634 See &%local_from_prefix%& above.
15635
15636
15637 .option local_interfaces main "string list" "see below"
15638 This option controls which network interfaces are used by the daemon for
15639 listening; they are also used to identify the local host when routing. Chapter
15640 &<<CHAPinterfaces>>& contains a full description of this option and the related
15641 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
15642 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
15643 &%local_interfaces%& is
15644 .code
15645 local_interfaces = 0.0.0.0
15646 .endd
15647 when Exim is built without IPv6 support; otherwise it is
15648 .code
15649 local_interfaces = <; ::0 ; 0.0.0.0
15650 .endd
15651
15652 .option local_scan_timeout main time 5m
15653 .cindex "timeout" "for &[local_scan()]& function"
15654 .cindex "&[local_scan()]& function" "timeout"
15655 This timeout applies to the &[local_scan()]& function (see chapter
15656 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
15657 the incoming message is rejected with a temporary error if it is an SMTP
15658 message. For a non-SMTP message, the message is dropped and Exim ends with a
15659 non-zero code. The incident is logged on the main and reject logs.
15660
15661
15662
15663 .option local_sender_retain main boolean false
15664 .cindex "&'Sender:'& header line" "retaining from local submission"
15665 When a message is submitted locally (that is, not over a TCP/IP connection) by
15666 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
15667 do not want this to happen, you must set &%local_sender_retain%&, and you must
15668 also set &%local_from_check%& to be false (Exim will complain if you do not).
15669 See also the ACL modifier &`control = suppress_local_fixups`&. Section
15670 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
15671
15672
15673
15674
15675 .option localhost_number main string&!! unset
15676 .cindex "host" "locally unique number for"
15677 .cindex "message ids" "with multiple hosts"
15678 .vindex "&$localhost_number$&"
15679 Exim's message ids are normally unique only within the local host. If
15680 uniqueness among a set of hosts is required, each host must set a different
15681 value for the &%localhost_number%& option. The string is expanded immediately
15682 after reading the configuration file (so that a number can be computed from the
15683 host name, for example) and the result of the expansion must be a number in the
15684 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
15685 systems). This is available in subsequent string expansions via the variable
15686 &$localhost_number$&. When &%localhost_number is set%&, the final two
15687 characters of the message id, instead of just being a fractional part of the
15688 time, are computed from the time and the local host number as described in
15689 section &<<SECTmessiden>>&.
15690
15691
15692
15693 .option log_file_path main "string list&!!" "set at compile time"
15694 .cindex "log" "file path for"
15695 This option sets the path which is used to determine the names of Exim's log
15696 files, or indicates that logging is to be to syslog, or both. It is expanded
15697 when Exim is entered, so it can, for example, contain a reference to the host
15698 name. If no specific path is set for the log files at compile or run time,
15699 or if the option is unset at run time (i.e. &`log_file_path = `&)
15700 they are written in a sub-directory called &_log_& in Exim's spool directory.
15701 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
15702 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
15703 used. If this string is fixed at your installation (contains no expansion
15704 variables) it is recommended that you do not set this option in the
15705 configuration file, but instead supply the path using LOG_FILE_PATH in
15706 &_Local/Makefile_& so that it is available to Exim for logging errors detected
15707 early on &-- in particular, failure to read the configuration file.
15708
15709
15710 .option log_selector main string unset
15711 .cindex "log" "selectors"
15712 This option can be used to reduce or increase the number of things that Exim
15713 writes to its log files. Its argument is made up of names preceded by plus or
15714 minus characters. For example:
15715 .code
15716 log_selector = +arguments -retry_defer
15717 .endd
15718 A list of possible names and what they control is given in the chapter on
15719 logging, in section &<<SECTlogselector>>&.
15720
15721
15722 .option log_timezone main boolean false
15723 .cindex "log" "timezone for entries"
15724 .vindex "&$tod_log$&"
15725 .vindex "&$tod_zone$&"
15726 By default, the timestamps on log lines are in local time without the
15727 timezone. This means that if your timezone changes twice a year, the timestamps
15728 in log lines are ambiguous for an hour when the clocks go back. One way of
15729 avoiding this problem is to set the timezone to UTC. An alternative is to set
15730 &%log_timezone%& true. This turns on the addition of the timezone offset to
15731 timestamps in log lines. Turning on this option can add quite a lot to the size
15732 of log files because each line is extended by 6 characters. Note that the
15733 &$tod_log$& variable contains the log timestamp without the zone, but there is
15734 another variable called &$tod_zone$& that contains just the timezone offset.
15735
15736
15737 .option lookup_open_max main integer 25
15738 .cindex "too many open files"
15739 .cindex "open files, too many"
15740 .cindex "file" "too many open"
15741 .cindex "lookup" "maximum open files"
15742 .cindex "limit" "open files for lookups"
15743 This option limits the number of simultaneously open files for single-key
15744 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
15745 Exim normally keeps these files open during routing, because often the same
15746 file is required several times. If the limit is reached, Exim closes the least
15747 recently used file. Note that if you are using the &'ndbm'& library, it
15748 actually opens two files for each logical DBM database, though it still counts
15749 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
15750 open files"& errors with NDBM, you need to reduce the value of
15751 &%lookup_open_max%&.
15752
15753
15754 .option max_username_length main integer 0
15755 .cindex "length of login name"
15756 .cindex "user name" "maximum length"
15757 .cindex "limit" "user name length"
15758 Some operating systems are broken in that they truncate long arguments to
15759 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
15760 this option is set greater than zero, any attempt to call &[getpwnam()]& with
15761 an argument that is longer behaves as if &[getpwnam()]& failed.
15762
15763
15764 .option message_body_newlines main bool false
15765 .cindex "message body" "newlines in variables"
15766 .cindex "newline" "in message body variables"
15767 .vindex "&$message_body$&"
15768 .vindex "&$message_body_end$&"
15769 By default, newlines in the message body are replaced by spaces when setting
15770 the &$message_body$& and &$message_body_end$& expansion variables. If this
15771 option is set true, this no longer happens.
15772
15773
15774 .option message_body_visible main integer 500
15775 .cindex "body of message" "visible size"
15776 .cindex "message body" "visible size"
15777 .vindex "&$message_body$&"
15778 .vindex "&$message_body_end$&"
15779 This option specifies how much of a message's body is to be included in the
15780 &$message_body$& and &$message_body_end$& expansion variables.
15781
15782
15783 .option message_id_header_domain main string&!! unset
15784 .cindex "&'Message-ID:'& header line"
15785 If this option is set, the string is expanded and used as the right hand side
15786 (domain) of the &'Message-ID:'& header that Exim creates if a
15787 locally-originated incoming message does not have one. &"Locally-originated"&
15788 means &"not received over TCP/IP."&
15789 Otherwise, the primary host name is used.
15790 Only letters, digits, dot and hyphen are accepted; any other characters are
15791 replaced by hyphens. If the expansion is forced to fail, or if the result is an
15792 empty string, the option is ignored.
15793
15794
15795 .option message_id_header_text main string&!! unset
15796 If this variable is set, the string is expanded and used to augment the text of
15797 the &'Message-id:'& header that Exim creates if a locally-originated incoming
15798 message does not have one. The text of this header is required by RFC 2822 to
15799 take the form of an address. By default, Exim uses its internal message id as
15800 the local part, and the primary host name as the domain. If this option is set,
15801 it is expanded, and provided the expansion is not forced to fail, and does not
15802 yield an empty string, the result is inserted into the header immediately
15803 before the @, separated from the internal message id by a dot. Any characters
15804 that are illegal in an address are automatically converted into hyphens. This
15805 means that variables such as &$tod_log$& can be used, because the spaces and
15806 colons will become hyphens.
15807
15808
15809 .option message_logs main boolean true
15810 .cindex "message logs" "disabling"
15811 .cindex "log" "message log; disabling"
15812 If this option is turned off, per-message log files are not created in the
15813 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
15814 Exim, by reducing the number of files involved in handling a message from a
15815 minimum of four (header spool file, body spool file, delivery journal, and
15816 per-message log) to three. The other major I/O activity is Exim's main log,
15817 which is not affected by this option.
15818
15819
15820 .option message_size_limit main string&!! 50M
15821 .cindex "message" "size limit"
15822 .cindex "limit" "message size"
15823 .cindex "size" "of message, limit"
15824 This option limits the maximum size of message that Exim will process. The
15825 value is expanded for each incoming connection so, for example, it can be made
15826 to depend on the IP address of the remote host for messages arriving via
15827 TCP/IP. After expansion, the value must be a sequence of decimal digits,
15828 optionally followed by K or M.
15829
15830 &*Note*&: This limit cannot be made to depend on a message's sender or any
15831 other properties of an individual message, because it has to be advertised in
15832 the server's response to EHLO. String expansion failure causes a temporary
15833 error. A value of zero means no limit, but its use is not recommended. See also
15834 &%bounce_return_size_limit%&.
15835
15836 Incoming SMTP messages are failed with a 552 error if the limit is
15837 exceeded; locally-generated messages either get a stderr message or a delivery
15838 failure message to the sender, depending on the &%-oe%& setting. Rejection of
15839 an oversized message is logged in both the main and the reject logs. See also
15840 the generic transport option &%message_size_limit%&, which limits the size of
15841 message that an individual transport can process.
15842
15843 If you use a virus-scanner and set this option to to a value larger than the
15844 maximum size that your virus-scanner is configured to support, you may get
15845 failures triggered by large mails. The right size to configure for the
15846 virus-scanner depends upon what data is passed and the options in use but it's
15847 probably safest to just set it to a little larger than this value. E.g., with a
15848 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
15849 some problems may result.
15850
15851 A value of 0 will disable size limit checking; Exim will still advertise the
15852 SIZE extension in an EHLO response, but without a limit, so as to permit
15853 SMTP clients to still indicate the message size along with the MAIL verb.
15854
15855
15856 .option move_frozen_messages main boolean false
15857 .cindex "frozen messages" "moving"
15858 This option, which is available only if Exim has been built with the setting
15859 .code
15860 SUPPORT_MOVE_FROZEN_MESSAGES=yes
15861 .endd
15862 in &_Local/Makefile_&, causes frozen messages and their message logs to be
15863 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
15864 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
15865 standard utilities for handling such moved messages, and they do not show up in
15866 lists generated by &%-bp%& or by the Exim monitor.
15867
15868
15869 .option mua_wrapper main boolean false
15870 Setting this option true causes Exim to run in a very restrictive mode in which
15871 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
15872 contains a full description of this facility.
15873
15874
15875
15876 .option mysql_servers main "string list" unset
15877 .cindex "MySQL" "server list"
15878 This option provides a list of MySQL servers and associated connection data, to
15879 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
15880 option is available only if Exim has been built with MySQL support.
15881
15882
15883 .option never_users main "string list&!!" unset
15884 This option is expanded just once, at the start of Exim's processing. Local
15885 message deliveries are normally run in processes that are setuid to the
15886 recipient, and remote deliveries are normally run under Exim's own uid and gid.
15887 It is usually desirable to prevent any deliveries from running as root, as a
15888 safety precaution.
15889
15890 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
15891 list of users that must not be used for local deliveries. This list is fixed in
15892 the binary and cannot be overridden by the configuration file. By default, it
15893 contains just the single user name &"root"&. The &%never_users%& runtime option
15894 can be used to add more users to the fixed list.
15895
15896 If a message is to be delivered as one of the users on the fixed list or the
15897 &%never_users%& list, an error occurs, and delivery is deferred. A common
15898 example is
15899 .code
15900 never_users = root:daemon:bin
15901 .endd
15902 Including root is redundant if it is also on the fixed list, but it does no
15903 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
15904 transport driver.
15905
15906
15907 .option openssl_options main "string list" "+no_sslv2 +single_dh_use +no_ticket"
15908 .cindex "OpenSSL "compatibility options"
15909 This option allows an administrator to adjust the SSL options applied
15910 by OpenSSL to connections. It is given as a space-separated list of items,
15911 each one to be +added or -subtracted from the current value.
15912
15913 This option is only available if Exim is built against OpenSSL. The values
15914 available for this option vary according to the age of your OpenSSL install.
15915 The &"all"& value controls a subset of flags which are available, typically
15916 the bug workaround options. The &'SSL_CTX_set_options'& man page will
15917 list the values known on your system and Exim should support all the
15918 &"bug workaround"& options and many of the &"modifying"& options. The Exim
15919 names lose the leading &"SSL_OP_"& and are lower-cased.
15920
15921 Note that adjusting the options can have severe impact upon the security of
15922 SSL as used by Exim. It is possible to disable safety checks and shoot
15923 yourself in the foot in various unpleasant ways. This option should not be
15924 adjusted lightly. An unrecognised item will be detected at startup, by
15925 invoking Exim with the &%-bV%& flag.
15926
15927 The option affects Exim operating both as a server and as a client.
15928
15929 Historical note: prior to release 4.80, Exim defaulted this value to
15930 "+dont_insert_empty_fragments", which may still be needed for compatibility
15931 with some clients, but which lowers security by increasing exposure to
15932 some now infamous attacks.
15933
15934 Examples:
15935 .code
15936 # Make both old MS and old Eudora happy:
15937 openssl_options = -all +microsoft_big_sslv3_buffer \
15938 +dont_insert_empty_fragments
15939
15940 # Disable older protocol versions:
15941 openssl_options = +no_sslv2 +no_sslv3
15942 .endd
15943
15944 Possible options may include:
15945 .ilist
15946 &`all`&
15947 .next
15948 &`allow_unsafe_legacy_renegotiation`&
15949 .next
15950 &`cipher_server_preference`&
15951 .next
15952 &`dont_insert_empty_fragments`&
15953 .next
15954 &`ephemeral_rsa`&
15955 .next
15956 &`legacy_server_connect`&
15957 .next
15958 &`microsoft_big_sslv3_buffer`&
15959 .next
15960 &`microsoft_sess_id_bug`&
15961 .next
15962 &`msie_sslv2_rsa_padding`&
15963 .next
15964 &`netscape_challenge_bug`&
15965 .next
15966 &`netscape_reuse_cipher_change_bug`&
15967 .next
15968 &`no_compression`&
15969 .next
15970 &`no_session_resumption_on_renegotiation`&
15971 .next
15972 &`no_sslv2`&
15973 .next
15974 &`no_sslv3`&
15975 .next
15976 &`no_ticket`&
15977 .next
15978 &`no_tlsv1`&
15979 .next
15980 &`no_tlsv1_1`&
15981 .next
15982 &`no_tlsv1_2`&
15983 .next
15984 &`safari_ecdhe_ecdsa_bug`&
15985 .next
15986 &`single_dh_use`&
15987 .next
15988 &`single_ecdh_use`&
15989 .next
15990 &`ssleay_080_client_dh_bug`&
15991 .next
15992 &`sslref2_reuse_cert_type_bug`&
15993 .next
15994 &`tls_block_padding_bug`&
15995 .next
15996 &`tls_d5_bug`&
15997 .next
15998 &`tls_rollback_bug`&
15999 .endlist
16000
16001 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
16002 all clients connecting using the MacOS SecureTransport TLS facility prior
16003 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
16004 to negotiate TLS then this option value might help, provided that your OpenSSL
16005 release is new enough to contain this work-around. This may be a situation
16006 where you have to upgrade OpenSSL to get buggy clients working.
16007
16008
16009 .option oracle_servers main "string list" unset
16010 .cindex "Oracle" "server list"
16011 This option provides a list of Oracle servers and associated connection data,
16012 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
16013 The option is available only if Exim has been built with Oracle support.
16014
16015
16016 .option percent_hack_domains main "domain list&!!" unset
16017 .cindex "&""percent hack""&"
16018 .cindex "source routing" "in email address"
16019 .cindex "address" "source-routed"
16020 The &"percent hack"& is the convention whereby a local part containing a
16021 percent sign is re-interpreted as a new email address, with the percent
16022 replaced by @. This is sometimes called &"source routing"&, though that term is
16023 also applied to RFC 2822 addresses that begin with an @ character. If this
16024 option is set, Exim implements the percent facility for those domains listed,
16025 but no others. This happens before an incoming SMTP address is tested against
16026 an ACL.
16027
16028 &*Warning*&: The &"percent hack"& has often been abused by people who are
16029 trying to get round relaying restrictions. For this reason, it is best avoided
16030 if at all possible. Unfortunately, a number of less security-conscious MTAs
16031 implement it unconditionally. If you are running Exim on a gateway host, and
16032 routing mail through to internal MTAs without processing the local parts, it is
16033 a good idea to reject recipient addresses with percent characters in their
16034 local parts. Exim's default configuration does this.
16035
16036
16037 .option perl_at_start main boolean false
16038 .cindex "Perl"
16039 This option is available only when Exim is built with an embedded Perl
16040 interpreter. See chapter &<<CHAPperl>>& for details of its use.
16041
16042
16043 .option perl_startup main string unset
16044 .cindex "Perl"
16045 This option is available only when Exim is built with an embedded Perl
16046 interpreter. See chapter &<<CHAPperl>>& for details of its use.
16047
16048 .option perl_startup main boolean false
16049 .cindex "Perl"
16050 This Option enables the taint mode of the embedded Perl interpreter.
16051
16052
16053 .option pgsql_servers main "string list" unset
16054 .cindex "PostgreSQL lookup type" "server list"
16055 This option provides a list of PostgreSQL servers and associated connection
16056 data, to be used in conjunction with &(pgsql)& lookups (see section
16057 &<<SECID72>>&). The option is available only if Exim has been built with
16058 PostgreSQL support.
16059
16060
16061 .option pid_file_path main string&!! "set at compile time"
16062 .cindex "daemon" "pid file path"
16063 .cindex "pid file, path for"
16064 This option sets the name of the file to which the Exim daemon writes its
16065 process id. The string is expanded, so it can contain, for example, references
16066 to the host name:
16067 .code
16068 pid_file_path = /var/log/$primary_hostname/exim.pid
16069 .endd
16070 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
16071 spool directory.
16072 The value set by the option can be overridden by the &%-oP%& command line
16073 option. A pid file is not written if a &"non-standard"& daemon is run by means
16074 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
16075
16076
16077 .option pipelining_advertise_hosts main "host list&!!" *
16078 .cindex "PIPELINING" "suppressing advertising"
16079 This option can be used to suppress the advertisement of the SMTP
16080 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
16081 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
16082 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
16083 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
16084 that clients will use it; &"out of order"& commands that are &"expected"& do
16085 not count as protocol errors (see &%smtp_max_synprot_errors%&).
16086
16087
16088 .option prdr_enable main boolean false
16089 .cindex "PRDR" "enabling on server"
16090 This option can be used to enable the Per-Recipient Data Response extension
16091 to SMTP, defined by Eric Hall.
16092 If the option is set, PRDR is advertised by Exim when operating as a server.
16093 If the client requests PRDR, and more than one recipient, for a message
16094 an additional ACL is called for each recipient after the message content
16095 is received. See section &<<SECTPRDRACL>>&.
16096
16097 .option preserve_message_logs main boolean false
16098 .cindex "message logs" "preserving"
16099 If this option is set, message log files are not deleted when messages are
16100 completed. Instead, they are moved to a sub-directory of the spool directory
16101 called &_msglog.OLD_&, where they remain available for statistical or debugging
16102 purposes. This is a dangerous option to set on systems with any appreciable
16103 volume of mail. Use with care!
16104
16105
16106 .option primary_hostname main string "see below"
16107 .cindex "name" "of local host"
16108 .cindex "host" "name of local"
16109 .cindex "local host" "name of"
16110 .vindex "&$primary_hostname$&"
16111 This specifies the name of the current host. It is used in the default EHLO or
16112 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
16113 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
16114 The value is also used by default in some SMTP response messages from an Exim
16115 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
16116
16117 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
16118 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
16119 contains only one component, Exim passes it to &[gethostbyname()]& (or
16120 &[getipnodebyname()]& when available) in order to obtain the fully qualified
16121 version. The variable &$primary_hostname$& contains the host name, whether set
16122 explicitly by this option, or defaulted.
16123
16124
16125 .option print_topbitchars main boolean false
16126 .cindex "printing characters"
16127 .cindex "8-bit characters"
16128 By default, Exim considers only those characters whose codes lie in the range
16129 32&--126 to be printing characters. In a number of circumstances (for example,
16130 when writing log entries) non-printing characters are converted into escape
16131 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
16132 is set, code values of 128 and above are also considered to be printing
16133 characters.
16134
16135 This option also affects the header syntax checks performed by the
16136 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
16137 the user's full name when constructing From: and Sender: addresses (as
16138 described in section &<<SECTconstr>>&). Setting this option can cause
16139 Exim to generate eight bit message headers that do not conform to the
16140 standards.
16141
16142
16143 .option process_log_path main string unset
16144 .cindex "process log path"
16145 .cindex "log" "process log"
16146 .cindex "&'exiwhat'&"
16147 This option sets the name of the file to which an Exim process writes its
16148 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
16149 utility script. If this option is unset, the file called &_exim-process.info_&
16150 in Exim's spool directory is used. The ability to specify the name explicitly
16151 can be useful in environments where two different Exims are running, using
16152 different spool directories.
16153
16154
16155 .option prod_requires_admin main boolean true
16156 .cindex "restricting access to features"
16157 .oindex "&%-M%&"
16158 .oindex "&%-R%&"
16159 .oindex "&%-q%&"
16160 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
16161 admin user unless &%prod_requires_admin%& is set false. See also
16162 &%queue_list_requires_admin%& and &%commandline_checks_require_admin%&.
16163
16164
16165 .option qualify_domain main string "see below"
16166 .cindex "domain" "for qualifying addresses"
16167 .cindex "address" "qualification"
16168 This option specifies the domain name that is added to any envelope sender
16169 addresses that do not have a domain qualification. It also applies to
16170 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
16171 are accepted by default only for locally-generated messages. Qualification is
16172 also applied to addresses in header lines such as &'From:'& and &'To:'& for
16173 locally-generated messages, unless the &%-bnq%& command line option is used.
16174
16175 Messages from external sources must always contain fully qualified addresses,
16176 unless the sending host matches &%sender_unqualified_hosts%& or
16177 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
16178 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
16179 necessary. Internally, Exim always works with fully qualified envelope
16180 addresses. If &%qualify_domain%& is not set, it defaults to the
16181 &%primary_hostname%& value.
16182
16183
16184 .option qualify_recipient main string "see below"
16185 This option allows you to specify a different domain for qualifying recipient
16186 addresses to the one that is used for senders. See &%qualify_domain%& above.
16187
16188
16189
16190 .option queue_domains main "domain list&!!" unset
16191 .cindex "domain" "specifying non-immediate delivery"
16192 .cindex "queueing incoming messages"
16193 .cindex "message" "queueing certain domains"
16194 This option lists domains for which immediate delivery is not required.
16195 A delivery process is started whenever a message is received, but only those
16196 domains that do not match are processed. All other deliveries wait until the
16197 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
16198
16199
16200 .option queue_list_requires_admin main boolean true
16201 .cindex "restricting access to features"
16202 .oindex "&%-bp%&"
16203 The &%-bp%& command-line option, which lists the messages that are on the
16204 queue, requires the caller to be an admin user unless
16205 &%queue_list_requires_admin%& is set false.
16206 See also &%prod_requires_admin%& and &%commandline_checks_require_admin%&.
16207
16208
16209 .option queue_only main boolean false
16210 .cindex "queueing incoming messages"
16211 .cindex "message" "queueing unconditionally"
16212 If &%queue_only%& is set, a delivery process is not automatically started
16213 whenever a message is received. Instead, the message waits on the queue for the
16214 next queue run. Even if &%queue_only%& is false, incoming messages may not get
16215 delivered immediately when certain conditions (such as heavy load) occur.
16216
16217 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
16218 and &%-odi%& command line options override &%queue_only%& unless
16219 &%queue_only_override%& is set false. See also &%queue_only_file%&,
16220 &%queue_only_load%&, and &%smtp_accept_queue%&.
16221
16222
16223 .option queue_only_file main string unset
16224 .cindex "queueing incoming messages"
16225 .cindex "message" "queueing by file existence"
16226 This option can be set to a colon-separated list of absolute path names, each
16227 one optionally preceded by &"smtp"&. When Exim is receiving a message,
16228 it tests for the existence of each listed path using a call to &[stat()]&. For
16229 each path that exists, the corresponding queueing option is set.
16230 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
16231 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
16232 .code
16233 queue_only_file = smtp/some/file
16234 .endd
16235 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
16236 &_/some/file_& exists.
16237
16238
16239 .option queue_only_load main fixed-point unset
16240 .cindex "load average"
16241 .cindex "queueing incoming messages"
16242 .cindex "message" "queueing by load"
16243 If the system load average is higher than this value, incoming messages from
16244 all sources are queued, and no automatic deliveries are started. If this
16245 happens during local or remote SMTP input, all subsequent messages received on
16246 the same SMTP connection are queued by default, whatever happens to the load in
16247 the meantime, but this can be changed by setting &%queue_only_load_latch%&
16248 false.
16249
16250 Deliveries will subsequently be performed by queue runner processes. This
16251 option has no effect on ancient operating systems on which Exim cannot
16252 determine the load average. See also &%deliver_queue_load_max%& and
16253 &%smtp_load_reserve%&.
16254
16255
16256 .option queue_only_load_latch main boolean true
16257 .cindex "load average" "re-evaluating per message"
16258 When this option is true (the default), once one message has been queued
16259 because the load average is higher than the value set by &%queue_only_load%&,
16260 all subsequent messages received on the same SMTP connection are also queued.
16261 This is a deliberate choice; even though the load average may fall below the
16262 threshold, it doesn't seem right to deliver later messages on the same
16263 connection when not delivering earlier ones. However, there are special
16264 circumstances such as very long-lived connections from scanning appliances
16265 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
16266 should be set false. This causes the value of the load average to be
16267 re-evaluated for each message.
16268
16269
16270 .option queue_only_override main boolean true
16271 .cindex "queueing incoming messages"
16272 When this option is true, the &%-od%&&'x'& command line options override the
16273 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
16274 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
16275 to override; they are accepted, but ignored.
16276
16277
16278 .option queue_run_in_order main boolean false
16279 .cindex "queue runner" "processing messages in order"
16280 If this option is set, queue runs happen in order of message arrival instead of
16281 in an arbitrary order. For this to happen, a complete list of the entire queue
16282 must be set up before the deliveries start. When the queue is all held in a
16283 single directory (the default), a single list is created for both the ordered
16284 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
16285 single list is not created when &%queue_run_in_order%& is false. In this case,
16286 the sub-directories are processed one at a time (in a random order), and this
16287 avoids setting up one huge list for the whole queue. Thus, setting
16288 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
16289 when the queue is large, because of the extra work in setting up the single,
16290 large list. In most situations, &%queue_run_in_order%& should not be set.
16291
16292
16293
16294 .option queue_run_max main integer&!! 5
16295 .cindex "queue runner" "maximum number of"
16296 This controls the maximum number of queue runner processes that an Exim daemon
16297 can run simultaneously. This does not mean that it starts them all at once,
16298 but rather that if the maximum number are still running when the time comes to
16299 start another one, it refrains from starting another one. This can happen with
16300 very large queues and/or very sluggish deliveries. This option does not,
16301 however, interlock with other processes, so additional queue runners can be
16302 started by other means, or by killing and restarting the daemon.
16303
16304 Setting this option to zero does not suppress queue runs; rather, it disables
16305 the limit, allowing any number of simultaneous queue runner processes to be
16306 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
16307 the daemon's command line.
16308
16309 .cindex queues named
16310 .cindex "named queues"
16311 To set limits for different named queues use
16312 an expansion depending on the &$queue_name$& variable.
16313
16314 .option queue_smtp_domains main "domain list&!!" unset
16315 .cindex "queueing incoming messages"
16316 .cindex "message" "queueing remote deliveries"
16317 When this option is set, a delivery process is started whenever a message is
16318 received, routing is performed, and local deliveries take place.
16319 However, if any SMTP deliveries are required for domains that match
16320 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
16321 message waits on the queue for the next queue run. Since routing of the message
16322 has taken place, Exim knows to which remote hosts it must be delivered, and so
16323 when the queue run happens, multiple messages for the same host are delivered
16324 over a single SMTP connection. The &%-odqs%& command line option causes all
16325 SMTP deliveries to be queued in this way, and is equivalent to setting
16326 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
16327 &%queue_domains%&.
16328
16329
16330 .option receive_timeout main time 0s
16331 .cindex "timeout" "for non-SMTP input"
16332 This option sets the timeout for accepting a non-SMTP message, that is, the
16333 maximum time that Exim waits when reading a message on the standard input. If
16334 the value is zero, it will wait for ever. This setting is overridden by the
16335 &%-or%& command line option. The timeout for incoming SMTP messages is
16336 controlled by &%smtp_receive_timeout%&.
16337
16338 .option received_header_text main string&!! "see below"
16339 .cindex "customizing" "&'Received:'& header"
16340 .cindex "&'Received:'& header line" "customizing"
16341 This string defines the contents of the &'Received:'& message header that is
16342 added to each message, except for the timestamp, which is automatically added
16343 on at the end (preceded by a semicolon). The string is expanded each time it is
16344 used. If the expansion yields an empty string, no &'Received:'& header line is
16345 added to the message. Otherwise, the string should start with the text
16346 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
16347 header lines. The default setting is:
16348
16349 .code
16350 received_header_text = Received: \
16351 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
16352 {${if def:sender_ident \
16353 {from ${quote_local_part:$sender_ident} }}\
16354 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
16355 by $primary_hostname \
16356 ${if def:received_protocol {with $received_protocol}} \
16357 ${if def:tls_in_cipher {($tls_in_cipher)\n\t}}\
16358 (Exim $version_number)\n\t\
16359 ${if def:sender_address \
16360 {(envelope-from <$sender_address>)\n\t}}\
16361 id $message_exim_id\
16362 ${if def:received_for {\n\tfor $received_for}}
16363 .endd
16364
16365 The reference to the TLS cipher is omitted when Exim is built without TLS
16366 support. The use of conditional expansions ensures that this works for both
16367 locally generated messages and messages received from remote hosts, giving
16368 header lines such as the following:
16369 .code
16370 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
16371 by marley.carol.example with esmtp (Exim 4.00)
16372 (envelope-from <bob@carol.example>)
16373 id 16IOWa-00019l-00
16374 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
16375 Received: by scrooge.carol.example with local (Exim 4.00)
16376 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
16377 .endd
16378 Until the body of the message has been received, the timestamp is the time when
16379 the message started to be received. Once the body has arrived, and all policy
16380 checks have taken place, the timestamp is updated to the time at which the
16381 message was accepted.
16382
16383
16384 .option received_headers_max main integer 30
16385 .cindex "loop" "prevention"
16386 .cindex "mail loop prevention"
16387 .cindex "&'Received:'& header line" "counting"
16388 When a message is to be delivered, the number of &'Received:'& headers is
16389 counted, and if it is greater than this parameter, a mail loop is assumed to
16390 have occurred, the delivery is abandoned, and an error message is generated.
16391 This applies to both local and remote deliveries.
16392
16393
16394 .option recipient_unqualified_hosts main "host list&!!" unset
16395 .cindex "unqualified addresses"
16396 .cindex "host" "unqualified addresses from"
16397 This option lists those hosts from which Exim is prepared to accept unqualified
16398 recipient addresses in message envelopes. The addresses are made fully
16399 qualified by the addition of the &%qualify_recipient%& value. This option also
16400 affects message header lines. Exim does not reject unqualified recipient
16401 addresses in headers, but it qualifies them only if the message came from a
16402 host that matches &%recipient_unqualified_hosts%&,
16403 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
16404 option was not set.
16405
16406
16407 .option recipients_max main integer 0
16408 .cindex "limit" "number of recipients"
16409 .cindex "recipient" "maximum number"
16410 If this option is set greater than zero, it specifies the maximum number of
16411 original recipients for any message. Additional recipients that are generated
16412 by aliasing or forwarding do not count. SMTP messages get a 452 response for
16413 all recipients over the limit; earlier recipients are delivered as normal.
16414 Non-SMTP messages with too many recipients are failed, and no deliveries are
16415 done.
16416
16417 .cindex "RCPT" "maximum number of incoming"
16418 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
16419 RCPT commands in a single message.
16420
16421
16422 .option recipients_max_reject main boolean false
16423 If this option is set true, Exim rejects SMTP messages containing too many
16424 recipients by giving 552 errors to the surplus RCPT commands, and a 554
16425 error to the eventual DATA command. Otherwise (the default) it gives a 452
16426 error to the surplus RCPT commands and accepts the message on behalf of the
16427 initial set of recipients. The remote server should then re-send the message
16428 for the remaining recipients at a later time.
16429
16430
16431 .option remote_max_parallel main integer 2
16432 .cindex "delivery" "parallelism for remote"
16433 This option controls parallel delivery of one message to a number of remote
16434 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
16435 does all the remote deliveries for a message one by one. Otherwise, if a single
16436 message has to be delivered to more than one remote host, or if several copies
16437 have to be sent to the same remote host, up to &%remote_max_parallel%&
16438 deliveries are done simultaneously. If more than &%remote_max_parallel%&
16439 deliveries are required, the maximum number of processes are started, and as
16440 each one finishes, another is begun. The order of starting processes is the
16441 same as if sequential delivery were being done, and can be controlled by the
16442 &%remote_sort_domains%& option. If parallel delivery takes place while running
16443 with debugging turned on, the debugging output from each delivery process is
16444 tagged with its process id.
16445
16446 This option controls only the maximum number of parallel deliveries for one
16447 message in one Exim delivery process. Because Exim has no central queue
16448 manager, there is no way of controlling the total number of simultaneous
16449 deliveries if the configuration allows a delivery attempt as soon as a message
16450 is received.
16451
16452 .cindex "number of deliveries"
16453 .cindex "delivery" "maximum number of"
16454 If you want to control the total number of deliveries on the system, you
16455 need to set the &%queue_only%& option. This ensures that all incoming messages
16456 are added to the queue without starting a delivery process. Then set up an Exim
16457 daemon to start queue runner processes at appropriate intervals (probably
16458 fairly often, for example, every minute), and limit the total number of queue
16459 runners by setting the &%queue_run_max%& parameter. Because each queue runner
16460 delivers only one message at a time, the maximum number of deliveries that can
16461 then take place at once is &%queue_run_max%& multiplied by
16462 &%remote_max_parallel%&.
16463
16464 If it is purely remote deliveries you want to control, use
16465 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
16466 doing the SMTP routing before queueing, so that several messages for the same
16467 host will eventually get delivered down the same connection.
16468
16469
16470 .option remote_sort_domains main "domain list&!!" unset
16471 .cindex "sorting remote deliveries"
16472 .cindex "delivery" "sorting remote"
16473 When there are a number of remote deliveries for a message, they are sorted by
16474 domain into the order given by this list. For example,
16475 .code
16476 remote_sort_domains = *.cam.ac.uk:*.uk
16477 .endd
16478 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
16479 then to those in the &%uk%& domain, then to any others.
16480
16481
16482 .option retry_data_expire main time 7d
16483 .cindex "hints database" "data expiry"
16484 This option sets a &"use before"& time on retry information in Exim's hints
16485 database. Any older retry data is ignored. This means that, for example, once a
16486 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
16487 past failures.
16488
16489
16490 .option retry_interval_max main time 24h
16491 .cindex "retry" "limit on interval"
16492 .cindex "limit" "on retry interval"
16493 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
16494 intervals between delivery attempts for messages that cannot be delivered
16495 straight away. This option sets an overall limit to the length of time between
16496 retries. It cannot be set greater than 24 hours; any attempt to do so forces
16497 the default value.
16498
16499
16500 .option return_path_remove main boolean true
16501 .cindex "&'Return-path:'& header line" "removing"
16502 RFC 2821, section 4.4, states that an SMTP server must insert a
16503 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
16504 The &'Return-path:'& header preserves the sender address as received in the
16505 MAIL command. This description implies that this header should not be present
16506 in an incoming message. If &%return_path_remove%& is true, any existing
16507 &'Return-path:'& headers are removed from messages at the time they are
16508 received. Exim's transports have options for adding &'Return-path:'& headers at
16509 the time of delivery. They are normally used only for final local deliveries.
16510
16511
16512 .option return_size_limit main integer 100K
16513 This option is an obsolete synonym for &%bounce_return_size_limit%&.
16514
16515
16516 .option rfc1413_hosts main "host list&!!" @[]
16517 .cindex "RFC 1413"
16518 .cindex "host" "for RFC 1413 calls"
16519 RFC 1413 identification calls are made to any client host which matches
16520 an item in the list.
16521 The default value specifies just this host, being any local interface
16522 for the system.
16523
16524 .option rfc1413_query_timeout main time 0s
16525 .cindex "RFC 1413" "query timeout"
16526 .cindex "timeout" "for RFC 1413 call"
16527 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
16528 no RFC 1413 calls are ever made.
16529
16530
16531 .option sender_unqualified_hosts main "host list&!!" unset
16532 .cindex "unqualified addresses"
16533 .cindex "host" "unqualified addresses from"
16534 This option lists those hosts from which Exim is prepared to accept unqualified
16535 sender addresses. The addresses are made fully qualified by the addition of
16536 &%qualify_domain%&. This option also affects message header lines. Exim does
16537 not reject unqualified addresses in headers that contain sender addresses, but
16538 it qualifies them only if the message came from a host that matches
16539 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
16540 using TCP/IP), and the &%-bnq%& option was not set.
16541
16542 .option set_environment main "string list" empty
16543 .cindex "environment"
16544 This option allows to set individual environment variables that the
16545 currently linked libraries and programs in child processes use. The
16546 default list is empty,
16547
16548
16549 .option slow_lookup_log main integer 0
16550 .cindex "logging" "slow lookups"
16551 .cindex "dns" "logging slow lookups"
16552 This option controls logging of slow lookups.
16553 If the value is nonzero it is taken as a number of milliseconds
16554 and lookups taking longer than this are logged.
16555 Currently this applies only to DNS lookups.
16556
16557
16558
16559 .option smtp_accept_keepalive main boolean true
16560 .cindex "keepalive" "on incoming connection"
16561 This option controls the setting of the SO_KEEPALIVE option on incoming
16562 TCP/IP socket connections. When set, it causes the kernel to probe idle
16563 connections periodically, by sending packets with &"old"& sequence numbers. The
16564 other end of the connection should send an acknowledgment if the connection is
16565 still okay or a reset if the connection has been aborted. The reason for doing
16566 this is that it has the beneficial effect of freeing up certain types of
16567 connection that can get stuck when the remote host is disconnected without
16568 tidying up the TCP/IP call properly. The keepalive mechanism takes several
16569 hours to detect unreachable hosts.
16570
16571
16572
16573 .option smtp_accept_max main integer 20
16574 .cindex "limit" "incoming SMTP connections"
16575 .cindex "SMTP" "incoming connection count"
16576 .cindex "inetd"
16577 This option specifies the maximum number of simultaneous incoming SMTP calls
16578 that Exim will accept. It applies only to the listening daemon; there is no
16579 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
16580 value is set to zero, no limit is applied. However, it is required to be
16581 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
16582 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
16583
16584 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
16585 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
16586 that limit has not been reached for the client host, &%smtp_accept_reserve%&
16587 and &%smtp_load_reserve%& are then checked before accepting the connection.
16588
16589
16590 .option smtp_accept_max_nonmail main integer 10
16591 .cindex "limit" "non-mail SMTP commands"
16592 .cindex "SMTP" "limiting non-mail commands"
16593 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
16594 the connection if there are too many. This option defines &"too many"&. The
16595 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
16596 client looping sending EHLO, for example. The check is applied only if the
16597 client host matches &%smtp_accept_max_nonmail_hosts%&.
16598
16599 When a new message is expected, one occurrence of RSET is not counted. This
16600 allows a client to send one RSET between messages (this is not necessary,
16601 but some clients do it). Exim also allows one uncounted occurrence of HELO
16602 or EHLO, and one occurrence of STARTTLS between messages. After
16603 starting up a TLS session, another EHLO is expected, and so it too is not
16604 counted. The first occurrence of AUTH in a connection, or immediately
16605 following STARTTLS is not counted. Otherwise, all commands other than
16606 MAIL, RCPT, DATA, and QUIT are counted.
16607
16608
16609 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
16610 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
16611 check by setting this option. The default value makes it apply to all hosts. By
16612 changing the value, you can exclude any badly-behaved hosts that you have to
16613 live with.
16614
16615
16616 . Allow this long option name to split; give it unsplit as a fifth argument
16617 . for the automatic .oindex that is generated by .option.
16618 . We insert " &~&~" which is both pretty nasty visually and results in
16619 . non-searchable text. HowItWorks.txt mentions an option for inserting
16620 . zero-width-space, which would be nicer visually and results in (at least)
16621 . html that Firefox will split on when it's forced to reflow (rather than
16622 . inserting a horizontal scrollbar). However, the text is still not
16623 . searchable. NM changed this occurrence for bug 1197 to no longer allow
16624 . the option name to split.
16625
16626 .option "smtp_accept_max_per_connection" main integer 1000 &&&
16627 smtp_accept_max_per_connection
16628 .cindex "SMTP" "limiting incoming message count"
16629 .cindex "limit" "messages per SMTP connection"
16630 The value of this option limits the number of MAIL commands that Exim is
16631 prepared to accept over a single SMTP connection, whether or not each command
16632 results in the transfer of a message. After the limit is reached, a 421
16633 response is given to subsequent MAIL commands. This limit is a safety
16634 precaution against a client that goes mad (incidents of this type have been
16635 seen).
16636
16637
16638 .option smtp_accept_max_per_host main string&!! unset
16639 .cindex "limit" "SMTP connections from one host"
16640 .cindex "host" "limiting SMTP connections from"
16641 This option restricts the number of simultaneous IP connections from a single
16642 host (strictly, from a single IP address) to the Exim daemon. The option is
16643 expanded, to enable different limits to be applied to different hosts by
16644 reference to &$sender_host_address$&. Once the limit is reached, additional
16645 connection attempts from the same host are rejected with error code 421. This
16646 is entirely independent of &%smtp_accept_reserve%&. The option's default value
16647 of zero imposes no limit. If this option is set greater than zero, it is
16648 required that &%smtp_accept_max%& be non-zero.
16649
16650 &*Warning*&: When setting this option you should not use any expansion
16651 constructions that take an appreciable amount of time. The expansion and test
16652 happen in the main daemon loop, in order to reject additional connections
16653 without forking additional processes (otherwise a denial-of-service attack
16654 could cause a vast number or processes to be created). While the daemon is
16655 doing this processing, it cannot accept any other incoming connections.
16656
16657
16658
16659 .option smtp_accept_queue main integer 0
16660 .cindex "SMTP" "incoming connection count"
16661 .cindex "queueing incoming messages"
16662 .cindex "message" "queueing by SMTP connection count"
16663 If the number of simultaneous incoming SMTP connections being handled via the
16664 listening daemon exceeds this value, messages received by SMTP are just placed
16665 on the queue; no delivery processes are started automatically. The count is
16666 fixed at the start of an SMTP connection. It cannot be updated in the
16667 subprocess that receives messages, and so the queueing or not queueing applies
16668 to all messages received in the same connection.
16669
16670 A value of zero implies no limit, and clearly any non-zero value is useful only
16671 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
16672 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
16673 various &%-od%&&'x'& command line options.
16674
16675
16676 . See the comment on smtp_accept_max_per_connection
16677
16678 .option "smtp_accept_queue_per_connection" main integer 10 &&&
16679 smtp_accept_queue_per_connection
16680 .cindex "queueing incoming messages"
16681 .cindex "message" "queueing by message count"
16682 This option limits the number of delivery processes that Exim starts
16683 automatically when receiving messages via SMTP, whether via the daemon or by
16684 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
16685 and the number of messages received in a single SMTP session exceeds this
16686 number, subsequent messages are placed on the queue, but no delivery processes
16687 are started. This helps to limit the number of Exim processes when a server
16688 restarts after downtime and there is a lot of mail waiting for it on other
16689 systems. On large systems, the default should probably be increased, and on
16690 dial-in client systems it should probably be set to zero (that is, disabled).
16691
16692
16693 .option smtp_accept_reserve main integer 0
16694 .cindex "SMTP" "incoming call count"
16695 .cindex "host" "reserved"
16696 When &%smtp_accept_max%& is set greater than zero, this option specifies a
16697 number of SMTP connections that are reserved for connections from the hosts
16698 that are specified in &%smtp_reserve_hosts%&. The value set in
16699 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
16700 restricted to this number of connections; the option specifies a minimum number
16701 of connection slots for them, not a maximum. It is a guarantee that this group
16702 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
16703 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
16704 individual host.
16705
16706 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
16707 set to 5, once there are 45 active connections (from any hosts), new
16708 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
16709 provided the other criteria for acceptance are met.
16710
16711
16712 .option smtp_active_hostname main string&!! unset
16713 .cindex "host" "name in SMTP responses"
16714 .cindex "SMTP" "host name in responses"
16715 .vindex "&$primary_hostname$&"
16716 This option is provided for multi-homed servers that want to masquerade as
16717 several different hosts. At the start of an incoming SMTP connection, its value
16718 is expanded and used instead of the value of &$primary_hostname$& in SMTP
16719 responses. For example, it is used as domain name in the response to an
16720 incoming HELO or EHLO command.
16721
16722 .vindex "&$smtp_active_hostname$&"
16723 The active hostname is placed in the &$smtp_active_hostname$& variable, which
16724 is saved with any messages that are received. It is therefore available for use
16725 in routers and transports when the message is later delivered.
16726
16727 If this option is unset, or if its expansion is forced to fail, or if the
16728 expansion results in an empty string, the value of &$primary_hostname$& is
16729 used. Other expansion failures cause a message to be written to the main and
16730 panic logs, and the SMTP command receives a temporary error. Typically, the
16731 value of &%smtp_active_hostname%& depends on the incoming interface address.
16732 For example:
16733 .code
16734 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
16735 {cox.mydomain}{box.mydomain}}
16736 .endd
16737
16738 Although &$smtp_active_hostname$& is primarily concerned with incoming
16739 messages, it is also used as the default for HELO commands in callout
16740 verification if there is no remote transport from which to obtain a
16741 &%helo_data%& value.
16742
16743 .option smtp_banner main string&!! "see below"
16744 .cindex "SMTP" "welcome banner"
16745 .cindex "banner for SMTP"
16746 .cindex "welcome banner for SMTP"
16747 .cindex "customizing" "SMTP banner"
16748 This string, which is expanded every time it is used, is output as the initial
16749 positive response to an SMTP connection. The default setting is:
16750 .code
16751 smtp_banner = $smtp_active_hostname ESMTP Exim \
16752 $version_number $tod_full
16753 .endd
16754 Failure to expand the string causes a panic error. If you want to create a
16755 multiline response to the initial SMTP connection, use &"\n"& in the string at
16756 appropriate points, but not at the end. Note that the 220 code is not included
16757 in this string. Exim adds it automatically (several times in the case of a
16758 multiline response).
16759
16760
16761 .option smtp_check_spool_space main boolean true
16762 .cindex "checking disk space"
16763 .cindex "disk space, checking"
16764 .cindex "spool directory" "checking space"
16765 When this option is set, if an incoming SMTP session encounters the SIZE
16766 option on a MAIL command, it checks that there is enough space in the
16767 spool directory's partition to accept a message of that size, while still
16768 leaving free the amount specified by &%check_spool_space%& (even if that value
16769 is zero). If there isn't enough space, a temporary error code is returned.
16770
16771
16772 .option smtp_connect_backlog main integer 20
16773 .cindex "connection backlog"
16774 .cindex "SMTP" "connection backlog"
16775 .cindex "backlog of connections"
16776 This option specifies a maximum number of waiting SMTP connections. Exim passes
16777 this value to the TCP/IP system when it sets up its listener. Once this number
16778 of connections are waiting for the daemon's attention, subsequent connection
16779 attempts are refused at the TCP/IP level. At least, that is what the manuals
16780 say; in some circumstances such connection attempts have been observed to time
16781 out instead. For large systems it is probably a good idea to increase the
16782 value (to 50, say). It also gives some protection against denial-of-service
16783 attacks by SYN flooding.
16784
16785
16786 .option smtp_enforce_sync main boolean true
16787 .cindex "SMTP" "synchronization checking"
16788 .cindex "synchronization checking in SMTP"
16789 The SMTP protocol specification requires the client to wait for a response from
16790 the server at certain points in the dialogue. Without PIPELINING these
16791 synchronization points are after every command; with PIPELINING they are
16792 fewer, but they still exist.
16793
16794 Some spamming sites send out a complete set of SMTP commands without waiting
16795 for any response. Exim protects against this by rejecting a message if the
16796 client has sent further input when it should not have. The error response &"554
16797 SMTP synchronization error"& is sent, and the connection is dropped. Testing
16798 for this error cannot be perfect because of transmission delays (unexpected
16799 input may be on its way but not yet received when Exim checks). However, it
16800 does detect many instances.
16801
16802 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
16803 If you want to disable the check selectively (for example, only for certain
16804 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
16805 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
16806
16807
16808
16809 .option smtp_etrn_command main string&!! unset
16810 .cindex "ETRN" "command to be run"
16811 .vindex "&$domain$&"
16812 If this option is set, the given command is run whenever an SMTP ETRN
16813 command is received from a host that is permitted to issue such commands (see
16814 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
16815 are independently expanded. The expansion variable &$domain$& is set to the
16816 argument of the ETRN command, and no syntax checking is done on it. For
16817 example:
16818 .code
16819 smtp_etrn_command = /etc/etrn_command $domain \
16820 $sender_host_address
16821 .endd
16822 A new process is created to run the command, but Exim does not wait for it to
16823 complete. Consequently, its status cannot be checked. If the command cannot be
16824 run, a line is written to the panic log, but the ETRN caller still receives
16825 a 250 success response. Exim is normally running under its own uid when
16826 receiving SMTP, so it is not possible for it to change the uid before running
16827 the command.
16828
16829
16830 .option smtp_etrn_serialize main boolean true
16831 .cindex "ETRN" "serializing"
16832 When this option is set, it prevents the simultaneous execution of more than
16833 one identical command as a result of ETRN in an SMTP connection. See
16834 section &<<SECTETRN>>& for details.
16835
16836
16837 .option smtp_load_reserve main fixed-point unset
16838 .cindex "load average"
16839 If the system load average ever gets higher than this, incoming SMTP calls are
16840 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
16841 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
16842 the load is over the limit. The option has no effect on ancient operating
16843 systems on which Exim cannot determine the load average. See also
16844 &%deliver_queue_load_max%& and &%queue_only_load%&.
16845
16846
16847
16848 .option smtp_max_synprot_errors main integer 3
16849 .cindex "SMTP" "limiting syntax and protocol errors"
16850 .cindex "limit" "SMTP syntax and protocol errors"
16851 Exim rejects SMTP commands that contain syntax or protocol errors. In
16852 particular, a syntactically invalid email address, as in this command:
16853 .code
16854 RCPT TO:<abc xyz@a.b.c>
16855 .endd
16856 causes immediate rejection of the command, before any other tests are done.
16857 (The ACL cannot be run if there is no valid address to set up for it.) An
16858 example of a protocol error is receiving RCPT before MAIL. If there are
16859 too many syntax or protocol errors in one SMTP session, the connection is
16860 dropped. The limit is set by this option.
16861
16862 .cindex "PIPELINING" "expected errors"
16863 When the PIPELINING extension to SMTP is in use, some protocol errors are
16864 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
16865 Exim assumes that PIPELINING will be used if it advertises it (see
16866 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
16867 not count towards the limit.
16868
16869
16870
16871 .option smtp_max_unknown_commands main integer 3
16872 .cindex "SMTP" "limiting unknown commands"
16873 .cindex "limit" "unknown SMTP commands"
16874 If there are too many unrecognized commands in an incoming SMTP session, an
16875 Exim server drops the connection. This is a defence against some kinds of abuse
16876 that subvert web
16877 clients
16878 into making connections to SMTP ports; in these circumstances, a number of
16879 non-SMTP command lines are sent first.
16880
16881
16882
16883 .option smtp_ratelimit_hosts main "host list&!!" unset
16884 .cindex "SMTP" "rate limiting"
16885 .cindex "limit" "rate of message arrival"
16886 .cindex "RCPT" "rate limiting"
16887 Some sites find it helpful to be able to limit the rate at which certain hosts
16888 can send them messages, and the rate at which an individual message can specify
16889 recipients.
16890
16891 Exim has two rate-limiting facilities. This section describes the older
16892 facility, which can limit rates within a single connection. The newer
16893 &%ratelimit%& ACL condition can limit rates across all connections. See section
16894 &<<SECTratelimiting>>& for details of the newer facility.
16895
16896 When a host matches &%smtp_ratelimit_hosts%&, the values of
16897 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
16898 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
16899 respectively. Each option, if set, must contain a set of four comma-separated
16900 values:
16901
16902 .ilist
16903 A threshold, before which there is no rate limiting.
16904 .next
16905 An initial time delay. Unlike other times in Exim, numbers with decimal
16906 fractional parts are allowed here.
16907 .next
16908 A factor by which to increase the delay each time.
16909 .next
16910 A maximum value for the delay. This should normally be less than 5 minutes,
16911 because after that time, the client is liable to timeout the SMTP command.
16912 .endlist
16913
16914 For example, these settings have been used successfully at the site which
16915 first suggested this feature, for controlling mail from their customers:
16916 .code
16917 smtp_ratelimit_mail = 2,0.5s,1.05,4m
16918 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
16919 .endd
16920 The first setting specifies delays that are applied to MAIL commands after
16921 two have been received over a single connection. The initial delay is 0.5
16922 seconds, increasing by a factor of 1.05 each time. The second setting applies
16923 delays to RCPT commands when more than four occur in a single message.
16924
16925
16926 .option smtp_ratelimit_mail main string unset
16927 See &%smtp_ratelimit_hosts%& above.
16928
16929
16930 .option smtp_ratelimit_rcpt main string unset
16931 See &%smtp_ratelimit_hosts%& above.
16932
16933
16934 .option smtp_receive_timeout main time&!! 5m
16935 .cindex "timeout" "for SMTP input"
16936 .cindex "SMTP" "input timeout"
16937 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
16938 input, including batch SMTP. If a line of input (either an SMTP command or a
16939 data line) is not received within this time, the SMTP connection is dropped and
16940 the message is abandoned.
16941 A line is written to the log containing one of the following messages:
16942 .code
16943 SMTP command timeout on connection from...
16944 SMTP data timeout on connection from...
16945 .endd
16946 The former means that Exim was expecting to read an SMTP command; the latter
16947 means that it was in the DATA phase, reading the contents of a message.
16948
16949 If the first character of the option is a &"$"& the option is
16950 expanded before use and may depend on
16951 &$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
16952
16953
16954 .oindex "&%-os%&"
16955 The value set by this option can be overridden by the
16956 &%-os%& command-line option. A setting of zero time disables the timeout, but
16957 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
16958 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
16959 timeout is controlled by &%receive_timeout%& and &%-or%&.
16960
16961
16962 .option smtp_reserve_hosts main "host list&!!" unset
16963 This option defines hosts for which SMTP connections are reserved; see
16964 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
16965
16966
16967 .option smtp_return_error_details main boolean false
16968 .cindex "SMTP" "details policy failures"
16969 .cindex "policy control" "rejection, returning details"
16970 In the default state, Exim uses bland messages such as
16971 &"Administrative prohibition"& when it rejects SMTP commands for policy
16972 reasons. Many sysadmins like this because it gives away little information
16973 to spammers. However, some other sysadmins who are applying strict checking
16974 policies want to give out much fuller information about failures. Setting
16975 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
16976 example, instead of &"Administrative prohibition"&, it might give:
16977 .code
16978 550-Rejected after DATA: '>' missing at end of address:
16979 550 failing address in "From" header is: <user@dom.ain
16980 .endd
16981
16982
16983 .option smtputf8_advertise_hosts main "host list&!!" *
16984 .cindex "SMTPUTF8" "advertising"
16985 When Exim is built with support for internationalised mail names,
16986 the availability thereof is advertised in
16987 response to EHLO only to those client hosts that match this option. See
16988 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
16989
16990
16991 .option spamd_address main string "127.0.0.1 783"
16992 This option is available when Exim is compiled with the content-scanning
16993 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
16994 See section &<<SECTscanspamass>>& for more details.
16995
16996
16997
16998 .option spf_guess main string "v=spf1 a/24 mx/24 ptr ?all"
16999 This option is available when Exim is compiled with SPF support.
17000 See section &<<SECSPF>>& for more details.
17001
17002
17003
17004 .option split_spool_directory main boolean false
17005 .cindex "multiple spool directories"
17006 .cindex "spool directory" "split"
17007 .cindex "directories, multiple"
17008 If this option is set, it causes Exim to split its input directory into 62
17009 subdirectories, each with a single alphanumeric character as its name. The
17010 sixth character of the message id is used to allocate messages to
17011 subdirectories; this is the least significant base-62 digit of the time of
17012 arrival of the message.
17013
17014 Splitting up the spool in this way may provide better performance on systems
17015 where there are long mail queues, by reducing the number of files in any one
17016 directory. The msglog directory is also split up in a similar way to the input
17017 directory; however, if &%preserve_message_logs%& is set, all old msglog files
17018 are still placed in the single directory &_msglog.OLD_&.
17019
17020 It is not necessary to take any special action for existing messages when
17021 changing &%split_spool_directory%&. Exim notices messages that are in the
17022 &"wrong"& place, and continues to process them. If the option is turned off
17023 after a period of being on, the subdirectories will eventually empty and be
17024 automatically deleted.
17025
17026 When &%split_spool_directory%& is set, the behaviour of queue runner processes
17027 changes. Instead of creating a list of all messages in the queue, and then
17028 trying to deliver each one in turn, it constructs a list of those in one
17029 sub-directory and tries to deliver them, before moving on to the next
17030 sub-directory. The sub-directories are processed in a random order. This
17031 spreads out the scanning of the input directories, and uses less memory. It is
17032 particularly beneficial when there are lots of messages on the queue. However,
17033 if &%queue_run_in_order%& is set, none of this new processing happens. The
17034 entire queue has to be scanned and sorted before any deliveries can start.
17035
17036
17037 .option spool_directory main string&!! "set at compile time"
17038 .cindex "spool directory" "path to"
17039 This defines the directory in which Exim keeps its spool, that is, the messages
17040 it is waiting to deliver. The default value is taken from the compile-time
17041 configuration setting, if there is one. If not, this option must be set. The
17042 string is expanded, so it can contain, for example, a reference to
17043 &$primary_hostname$&.
17044
17045 If the spool directory name is fixed on your installation, it is recommended
17046 that you set it at build time rather than from this option, particularly if the
17047 log files are being written to the spool directory (see &%log_file_path%&).
17048 Otherwise log files cannot be used for errors that are detected early on, such
17049 as failures in the configuration file.
17050
17051 By using this option to override the compiled-in path, it is possible to run
17052 tests of Exim without using the standard spool.
17053
17054 .option spool_wireformat main boolean false
17055 .cindex "spool directory" "file formats"
17056 If this option is set, Exim may for some messages use an alternative format
17057 for data-files in the spool which matches the wire format.
17058 Doing this permits more efficient message reception and transmission.
17059 Currently it is only done for messages received using the ESMTP CHUNKING
17060 option.
17061
17062 The following variables will not have useful values:
17063 .code
17064 $max_received_linelength
17065 $body_linecount
17066 $body_zerocount
17067 .endd
17068
17069 Users of the local_scan() API (see &<<CHAPlocalscan>>&),
17070 and any external programs which are passed a reference to a message data file
17071 (except via the &"regex"&, &"malware"& or &"spam"&) ACL conditions)
17072 will need to be aware of the different formats potentially available.
17073
17074 Using any of the ACL conditions noted will negate the reception benefit
17075 (as a Unix-mbox-format file is constructed for them).
17076 The transmission benefit is maintained.
17077
17078 .option sqlite_lock_timeout main time 5s
17079 .cindex "sqlite lookup type" "lock timeout"
17080 This option controls the timeout that the &(sqlite)& lookup uses when trying to
17081 access an SQLite database. See section &<<SECTsqlite>>& for more details.
17082
17083 .option strict_acl_vars main boolean false
17084 .cindex "&ACL;" "variables, handling unset"
17085 This option controls what happens if a syntactically valid but undefined ACL
17086 variable is referenced. If it is false (the default), an empty string
17087 is substituted; if it is true, an error is generated. See section
17088 &<<SECTaclvariables>>& for details of ACL variables.
17089
17090 .option strip_excess_angle_brackets main boolean false
17091 .cindex "angle brackets, excess"
17092 If this option is set, redundant pairs of angle brackets round &"route-addr"&
17093 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
17094 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
17095 passed on to another MTA, the excess angle brackets are not passed on. If this
17096 option is not set, multiple pairs of angle brackets cause a syntax error.
17097
17098
17099 .option strip_trailing_dot main boolean false
17100 .cindex "trailing dot on domain"
17101 .cindex "dot" "trailing on domain"
17102 If this option is set, a trailing dot at the end of a domain in an address is
17103 ignored. If this is in the envelope and the message is passed on to another
17104 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
17105 domain causes a syntax error.
17106 However, addresses in header lines are checked only when an ACL requests header
17107 syntax checking.
17108
17109
17110 .option syslog_duplication main boolean true
17111 .cindex "syslog" "duplicate log lines; suppressing"
17112 When Exim is logging to syslog, it writes the log lines for its three
17113 separate logs at different syslog priorities so that they can in principle
17114 be separated on the logging hosts. Some installations do not require this
17115 separation, and in those cases, the duplication of certain log lines is a
17116 nuisance. If &%syslog_duplication%& is set false, only one copy of any
17117 particular log line is written to syslog. For lines that normally go to
17118 both the main log and the reject log, the reject log version (possibly
17119 containing message header lines) is written, at LOG_NOTICE priority.
17120 Lines that normally go to both the main and the panic log are written at
17121 the LOG_ALERT priority.
17122
17123
17124 .option syslog_facility main string unset
17125 .cindex "syslog" "facility; setting"
17126 This option sets the syslog &"facility"& name, used when Exim is logging to
17127 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
17128 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
17129 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
17130 details of Exim's logging.
17131
17132
17133 .option syslog_pid main boolean true
17134 .cindex "syslog" "pid"
17135 If &%syslog_pid%& is set false, the PID on Exim's log lines are
17136 omitted when these lines are sent to syslog. (Syslog normally prefixes
17137 the log lines with the PID of the logging process automatically.) You need
17138 to enable the &`+pid`& log selector item, if you want Exim to write it's PID
17139 into the logs.) See chapter &<<CHAPlog>>& for details of Exim's logging.
17140
17141
17142
17143 .option syslog_processname main string &`exim`&
17144 .cindex "syslog" "process name; setting"
17145 This option sets the syslog &"ident"& name, used when Exim is logging to
17146 syslog. The value must be no longer than 32 characters. See chapter
17147 &<<CHAPlog>>& for details of Exim's logging.
17148
17149
17150
17151 .option syslog_timestamp main boolean true
17152 .cindex "syslog" "timestamps"
17153 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
17154 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
17155 details of Exim's logging.
17156
17157
17158 .option system_filter main string&!! unset
17159 .cindex "filter" "system filter"
17160 .cindex "system filter" "specifying"
17161 .cindex "Sieve filter" "not available for system filter"
17162 This option specifies an Exim filter file that is applied to all messages at
17163 the start of each delivery attempt, before any routing is done. System filters
17164 must be Exim filters; they cannot be Sieve filters. If the system filter
17165 generates any deliveries to files or pipes, or any new mail messages, the
17166 appropriate &%system_filter_..._transport%& option(s) must be set, to define
17167 which transports are to be used. Details of this facility are given in chapter
17168 &<<CHAPsystemfilter>>&.
17169 A forced expansion failure results in no filter operation.
17170
17171
17172 .option system_filter_directory_transport main string&!! unset
17173 .vindex "&$address_file$&"
17174 This sets the name of the transport driver that is to be used when the
17175 &%save%& command in a system message filter specifies a path ending in &"/"&,
17176 implying delivery of each message into a separate file in some directory.
17177 During the delivery, the variable &$address_file$& contains the path name.
17178
17179
17180 .option system_filter_file_transport main string&!! unset
17181 .cindex "file" "transport for system filter"
17182 This sets the name of the transport driver that is to be used when the &%save%&
17183 command in a system message filter specifies a path not ending in &"/"&. During
17184 the delivery, the variable &$address_file$& contains the path name.
17185
17186 .option system_filter_group main string unset
17187 .cindex "gid (group id)" "system filter"
17188 This option is used only when &%system_filter_user%& is also set. It sets the
17189 gid under which the system filter is run, overriding any gid that is associated
17190 with the user. The value may be numerical or symbolic.
17191
17192 .option system_filter_pipe_transport main string&!! unset
17193 .cindex "&(pipe)& transport" "for system filter"
17194 .vindex "&$address_pipe$&"
17195 This specifies the transport driver that is to be used when a &%pipe%& command
17196 is used in a system filter. During the delivery, the variable &$address_pipe$&
17197 contains the pipe command.
17198
17199
17200 .option system_filter_reply_transport main string&!! unset
17201 .cindex "&(autoreply)& transport" "for system filter"
17202 This specifies the transport driver that is to be used when a &%mail%& command
17203 is used in a system filter.
17204
17205
17206 .option system_filter_user main string unset
17207 .cindex "uid (user id)" "system filter"
17208 If this option is set to root, the system filter is run in the main Exim
17209 delivery process, as root. Otherwise, the system filter runs in a separate
17210 process, as the given user, defaulting to the Exim run-time user.
17211 Unless the string consists entirely of digits, it
17212 is looked up in the password data. Failure to find the named user causes a
17213 configuration error. The gid is either taken from the password data, or
17214 specified by &%system_filter_group%&. When the uid is specified numerically,
17215 &%system_filter_group%& is required to be set.
17216
17217 If the system filter generates any pipe, file, or reply deliveries, the uid
17218 under which the filter is run is used when transporting them, unless a
17219 transport option overrides.
17220
17221
17222 .option tcp_nodelay main boolean true
17223 .cindex "daemon" "TCP_NODELAY on sockets"
17224 .cindex "Nagle algorithm"
17225 .cindex "TCP_NODELAY on listening sockets"
17226 If this option is set false, it stops the Exim daemon setting the
17227 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
17228 turns off the &"Nagle algorithm"&, which is a way of improving network
17229 performance in interactive (character-by-character) situations. Turning it off
17230 should improve Exim's performance a bit, so that is what happens by default.
17231 However, it appears that some broken clients cannot cope, and time out. Hence
17232 this option. It affects only those sockets that are set up for listening by the
17233 daemon. Sockets created by the smtp transport for delivering mail always set
17234 TCP_NODELAY.
17235
17236
17237 .option timeout_frozen_after main time 0s
17238 .cindex "frozen messages" "timing out"
17239 .cindex "timeout" "frozen messages"
17240 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
17241 message of any kind that has been on the queue for longer than the given time
17242 is automatically cancelled at the next queue run. If the frozen message is a
17243 bounce message, it is just discarded; otherwise, a bounce is sent to the
17244 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
17245 If you want to timeout frozen bounce messages earlier than other kinds of
17246 frozen message, see &%ignore_bounce_errors_after%&.
17247
17248 &*Note:*& the default value of zero means no timeouts; with this setting,
17249 frozen messages remain on the queue forever (except for any frozen bounce
17250 messages that are released by &%ignore_bounce_errors_after%&).
17251
17252
17253 .option timezone main string unset
17254 .cindex "timezone, setting"
17255 .cindex "environment" "values from"
17256 The value of &%timezone%& is used to set the environment variable TZ while
17257 running Exim (if it is different on entry). This ensures that all timestamps
17258 created by Exim are in the required timezone. If you want all your timestamps
17259 to be in UTC (aka GMT) you should set
17260 .code
17261 timezone = UTC
17262 .endd
17263 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
17264 or, if that is not set, from the value of the TZ environment variable when Exim
17265 is built. If &%timezone%& is set to the empty string, either at build or run
17266 time, any existing TZ variable is removed from the environment when Exim
17267 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
17268 unfortunately not all, operating systems.
17269
17270
17271 .option tls_advertise_hosts main "host list&!!" *
17272 .cindex "TLS" "advertising"
17273 .cindex "encryption" "on SMTP connection"
17274 .cindex "SMTP" "encrypted connection"
17275 When Exim is built with support for TLS encrypted connections, the availability
17276 of the STARTTLS command to set up an encrypted session is advertised in
17277 response to EHLO only to those client hosts that match this option. See
17278 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
17279 Note that the default value requires that a certificate be supplied
17280 using the &%tls_certificate%& option. If TLS support for incoming connections
17281 is not required the &%tls_advertise_hosts%& option should be set empty.
17282
17283
17284 .option tls_certificate main string list&!! unset
17285 .cindex "TLS" "server certificate; location of"
17286 .cindex "certificate" "server, location of"
17287 The value of this option is expanded, and must then be a list of absolute paths to
17288 files which contains the server's certificates. Commonly only one file is
17289 needed.
17290 The server's private key is also
17291 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
17292 &<<CHAPTLS>>& for further details.
17293
17294 &*Note*&: The certificates defined by this option are used only when Exim is
17295 receiving incoming messages as a server. If you want to supply certificates for
17296 use when sending messages as a client, you must set the &%tls_certificate%&
17297 option in the relevant &(smtp)& transport.
17298
17299 &*Note*&: If you use filenames based on IP addresses, change the list
17300 separator in the usual way to avoid confusion under IPv6.
17301
17302 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
17303 when a list of more than one
17304 file is used, the &$tls_in_ourcert$& variable is unreliable.
17305
17306 &*Note*&: OCSP stapling is not usable under OpenSSL
17307 when a list of more than one file is used.
17308
17309 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
17310 if the OpenSSL build supports TLS extensions and the TLS client sends the
17311 Server Name Indication extension, then this option and others documented in
17312 &<<SECTtlssni>>& will be re-expanded.
17313
17314 If this option is unset or empty a fresh self-signed certificate will be
17315 generated for every connection.
17316
17317 .option tls_crl main string&!! unset
17318 .cindex "TLS" "server certificate revocation list"
17319 .cindex "certificate" "revocation list for server"
17320 This option specifies a certificate revocation list. The expanded value must
17321 be the name of a file that contains CRLs in PEM format.
17322
17323 Under OpenSSL the option can specify a directory with CRL files.
17324
17325 &*Note:*& Under OpenSSL the option must, if given, supply a CRL
17326 for each signing element of the certificate chain (i.e. all but the leaf).
17327 For the file variant this can be multiple PEM blocks in the one file.
17328
17329 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
17330
17331
17332 .option tls_dh_max_bits main integer 2236
17333 .cindex "TLS" "D-H bit count"
17334 The number of bits used for Diffie-Hellman key-exchange may be suggested by
17335 the chosen TLS library. That value might prove to be too high for
17336 interoperability. This option provides a maximum clamp on the value
17337 suggested, trading off security for interoperability.
17338
17339 The value must be at least 1024.
17340
17341 The value 2236 was chosen because, at time of adding the option, it was the
17342 hard-coded maximum value supported by the NSS cryptographic library, as used
17343 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
17344
17345 If you prefer more security and are willing to break some clients, raise this
17346 number.
17347
17348 Note that the value passed to GnuTLS for *generating* a new prime may be a
17349 little less than this figure, because GnuTLS is inexact and may produce a
17350 larger prime than requested.
17351
17352
17353 .option tls_dhparam main string&!! unset
17354 .cindex "TLS" "D-H parameters for server"
17355 The value of this option is expanded and indicates the source of DH parameters
17356 to be used by Exim.
17357
17358 &*Note: The Exim Maintainers strongly recommend using a filename with site-generated
17359 local DH parameters*&, which has been supported across all versions of Exim. The
17360 other specific constants available are a fallback so that even when
17361 "unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
17362
17363 If &%tls_dhparam%& is a filename starting with a &`/`&,
17364 then it names a file from which DH
17365 parameters should be loaded. If the file exists, it should hold a PEM-encoded
17366 PKCS#3 representation of the DH prime. If the file does not exist, for
17367 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
17368 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
17369 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
17370 and treated as though the &%tls_dhparam%& were set to "none".
17371
17372 If this option expands to the string "none", then no DH parameters will be
17373 loaded by Exim.
17374
17375 If this option expands to the string "historic" and Exim is using GnuTLS, then
17376 Exim will attempt to load a file from inside the spool directory. If the file
17377 does not exist, Exim will attempt to create it.
17378 See section &<<SECTgnutlsparam>>& for further details.
17379
17380 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
17381 a default DH prime; the default is Exim-specific but lacks verifiable provenance.
17382
17383 In older versions of Exim the default was the 2048 bit prime described in section
17384 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
17385 in IKE is assigned number 23.
17386
17387 Otherwise, the option must expand to the name used by Exim for any of a number
17388 of DH primes specified in RFC 2409, RFC 3526, RFC 5114, RFC 7919, or from other
17389 sources. As names, Exim uses a standard specified name, else "ike" followed by
17390 the number used by IKE, or "default" which corresponds to
17391 &`exim.dev.20160529.3`&.
17392
17393 The available standard primes are:
17394 &`ffdhe2048`&, &`ffdhe3072`&, &`ffdhe4096`&, &`ffdhe6144`&, &`ffdhe8192`&,
17395 &`ike1`&, &`ike2`&, &`ike5`&,
17396 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
17397 &`ike22`&, &`ike23`& and &`ike24`&.
17398
17399 The available additional primes are:
17400 &`exim.dev.20160529.1`&, &`exim.dev.20160529.2`& and &`exim.dev.20160529.3`&.
17401
17402 Some of these will be too small to be accepted by clients.
17403 Some may be too large to be accepted by clients.
17404 The open cryptographic community has suspicions about the integrity of some
17405 of the later IKE values, which led into RFC7919 providing new fixed constants
17406 (the "ffdhe" identifiers).
17407
17408 At this point, all of the "ike" values should be considered obsolete;
17409 they're still in Exim to avoid breaking unusual configurations, but are
17410 candidates for removal the next time we have backwards-incompatible changes.
17411
17412 The TLS protocol does not negotiate an acceptable size for this; clients tend
17413 to hard-drop connections if what is offered by the server is unacceptable,
17414 whether too large or too small, and there's no provision for the client to
17415 tell the server what these constraints are. Thus, as a server operator, you
17416 need to make an educated guess as to what is most likely to work for your
17417 userbase.
17418
17419 Some known size constraints suggest that a bit-size in the range 2048 to 2236
17420 is most likely to maximise interoperability. The upper bound comes from
17421 applications using the Mozilla Network Security Services (NSS) library, which
17422 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
17423 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
17424 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
17425 acceptable bound from 1024 to 2048.
17426
17427
17428 .option tls_eccurve main string&!! &`auto`&
17429 .cindex TLS "EC cryptography"
17430 This option selects a EC curve for use by Exim when used with OpenSSL.
17431 It has no effect when Exim is used with GnuTLS.
17432
17433 After expansion it must contain a valid EC curve parameter, such as
17434 &`prime256v1`&, &`secp384r1`&, or &`P-512`&. Consult your OpenSSL manual
17435 for valid selections.
17436
17437 For OpenSSL versions before (and not including) 1.0.2, the string
17438 &`auto`& selects &`prime256v1`&. For more recent OpenSSL versions
17439 &`auto`& tells the library to choose.
17440
17441 If the option expands to an empty string, no EC curves will be enabled.
17442
17443
17444 .option tls_ocsp_file main string&!! unset
17445 .cindex TLS "certificate status"
17446 .cindex TLS "OCSP proof file"
17447 This option
17448 must if set expand to the absolute path to a file which contains a current
17449 status proof for the server's certificate, as obtained from the
17450 Certificate Authority.
17451
17452 Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
17453
17454 For GnuTLS 3.5.6 or later the expanded value of this option can be a list
17455 of files, to match a list given for the &%tls_certificate%& option.
17456 The ordering of the two lists must match.
17457
17458
17459 .option tls_on_connect_ports main "string list" unset
17460 .cindex SSMTP
17461 .cindex SMTPS
17462 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
17463 operate the SSMTP (SMTPS) protocol, where a TLS session is immediately
17464 set up without waiting for the client to issue a STARTTLS command. For
17465 further details, see section &<<SECTsupobssmt>>&.
17466
17467
17468
17469 .option tls_privatekey main string list&!! unset
17470 .cindex "TLS" "server private key; location of"
17471 The value of this option is expanded, and must then be a list of absolute paths to
17472 files which contains the server's private keys.
17473 If this option is unset, or if
17474 the expansion is forced to fail, or the result is an empty string, the private
17475 key is assumed to be in the same file as the server's certificates. See chapter
17476 &<<CHAPTLS>>& for further details.
17477
17478 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
17479
17480
17481 .option tls_remember_esmtp main boolean false
17482 .cindex "TLS" "esmtp state; remembering"
17483 .cindex "TLS" "broken clients"
17484 If this option is set true, Exim violates the RFCs by remembering that it is in
17485 &"esmtp"& state after successfully negotiating a TLS session. This provides
17486 support for broken clients that fail to send a new EHLO after starting a
17487 TLS session.
17488
17489
17490 .option tls_require_ciphers main string&!! unset
17491 .cindex "TLS" "requiring specific ciphers"
17492 .cindex "cipher" "requiring specific"
17493 This option controls which ciphers can be used for incoming TLS connections.
17494 The &(smtp)& transport has an option of the same name for controlling outgoing
17495 connections. This option is expanded for each connection, so can be varied for
17496 different clients if required. The value of this option must be a list of
17497 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
17498 in somewhat different ways. If GnuTLS is being used, the client controls the
17499 preference order of the available ciphers. Details are given in sections
17500 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
17501
17502
17503 .option tls_try_verify_hosts main "host list&!!" unset
17504 .cindex "TLS" "client certificate verification"
17505 .cindex "certificate" "verification of client"
17506 See &%tls_verify_hosts%& below.
17507
17508
17509 .option tls_verify_certificates main string&!! system
17510 .cindex "TLS" "client certificate verification"
17511 .cindex "certificate" "verification of client"
17512 The value of this option is expanded, and must then be either the
17513 word "system"
17514 or the absolute path to
17515 a file or directory containing permitted certificates for clients that
17516 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
17517
17518 The "system" value for the option will use a
17519 system default location compiled into the SSL library.
17520 This is not available for GnuTLS versions preceding 3.0.20,
17521 and will be taken as empty; an explicit location
17522 must be specified.
17523
17524 The use of a directory for the option value is not available for GnuTLS versions
17525 preceding 3.3.6 and a single file must be used.
17526
17527 With OpenSSL the certificates specified
17528 explicitly
17529 either by file or directory
17530 are added to those given by the system default location.
17531
17532 These certificates should be for the certificate authorities trusted, rather
17533 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
17534 the value is a file then the certificates are sent by Exim as a server to
17535 connecting clients, defining the list of accepted certificate authorities.
17536 Thus the values defined should be considered public data. To avoid this,
17537 use the explicit directory version.
17538
17539 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
17540
17541 A forced expansion failure or setting to an empty string is equivalent to
17542 being unset.
17543
17544
17545 .option tls_verify_hosts main "host list&!!" unset
17546 .cindex "TLS" "client certificate verification"
17547 .cindex "certificate" "verification of client"
17548 This option, along with &%tls_try_verify_hosts%&, controls the checking of
17549 certificates from clients. The expected certificates are defined by
17550 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
17551 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
17552 &%tls_verify_certificates%& is not set.
17553
17554 Any client that matches &%tls_verify_hosts%& is constrained by
17555 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
17556 present one of the listed certificates. If it does not, the connection is
17557 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
17558 the host to use TLS. It can still send SMTP commands through unencrypted
17559 connections. Forcing a client to use TLS has to be done separately using an
17560 ACL to reject inappropriate commands when the connection is not encrypted.
17561
17562 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
17563 matches this option (but not &%tls_verify_hosts%&), Exim requests a
17564 certificate and checks it against &%tls_verify_certificates%&, but does not
17565 abort the connection if there is no certificate or if it does not match. This
17566 state can be detected in an ACL, which makes it possible to implement policies
17567 such as &"accept for relay only if a verified certificate has been received,
17568 but accept for local delivery if encrypted, even without a verified
17569 certificate"&.
17570
17571 Client hosts that match neither of these lists are not asked to present
17572 certificates.
17573
17574
17575 .option trusted_groups main "string list&!!" unset
17576 .cindex "trusted groups"
17577 .cindex "groups" "trusted"
17578 This option is expanded just once, at the start of Exim's processing. If this
17579 option is set, any process that is running in one of the listed groups, or
17580 which has one of them as a supplementary group, is trusted. The groups can be
17581 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
17582 details of what trusted callers are permitted to do. If neither
17583 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
17584 are trusted.
17585
17586 .option trusted_users main "string list&!!" unset
17587 .cindex "trusted users"
17588 .cindex "user" "trusted"
17589 This option is expanded just once, at the start of Exim's processing. If this
17590 option is set, any process that is running as one of the listed users is
17591 trusted. The users can be specified numerically or by name. See section
17592 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
17593 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
17594 Exim user are trusted.
17595
17596 .option unknown_login main string&!! unset
17597 .cindex "uid (user id)" "unknown caller"
17598 .vindex "&$caller_uid$&"
17599 This is a specialized feature for use in unusual configurations. By default, if
17600 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
17601 gives up. The &%unknown_login%& option can be used to set a login name to be
17602 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
17603 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
17604 is used for the user's real name (gecos field), unless this has been set by the
17605 &%-F%& option.
17606
17607 .option unknown_username main string unset
17608 See &%unknown_login%&.
17609
17610 .option untrusted_set_sender main "address list&!!" unset
17611 .cindex "trusted users"
17612 .cindex "sender" "setting by untrusted user"
17613 .cindex "untrusted user setting sender"
17614 .cindex "user" "untrusted setting sender"
17615 .cindex "envelope sender"
17616 When an untrusted user submits a message to Exim using the standard input, Exim
17617 normally creates an envelope sender address from the user's login and the
17618 default qualification domain. Data from the &%-f%& option (for setting envelope
17619 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
17620 is used) is ignored.
17621
17622 However, untrusted users are permitted to set an empty envelope sender address,
17623 to declare that a message should never generate any bounces. For example:
17624 .code
17625 exim -f '<>' user@domain.example
17626 .endd
17627 .vindex "&$sender_ident$&"
17628 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
17629 other envelope sender addresses in a controlled way. When it is set, untrusted
17630 users are allowed to set envelope sender addresses that match any of the
17631 patterns in the list. Like all address lists, the string is expanded. The
17632 identity of the user is in &$sender_ident$&, so you can, for example, restrict
17633 users to setting senders that start with their login ids
17634 followed by a hyphen
17635 by a setting like this:
17636 .code
17637 untrusted_set_sender = ^$sender_ident-
17638 .endd
17639 If you want to allow untrusted users to set envelope sender addresses without
17640 restriction, you can use
17641 .code
17642 untrusted_set_sender = *
17643 .endd
17644 The &%untrusted_set_sender%& option applies to all forms of local input, but
17645 only to the setting of the envelope sender. It does not permit untrusted users
17646 to use the other options which trusted user can use to override message
17647 parameters. Furthermore, it does not stop Exim from removing an existing
17648 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
17649 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
17650 overriding these actions. The handling of the &'Sender:'& header is also
17651 described in section &<<SECTthesenhea>>&.
17652
17653 The log line for a message's arrival shows the envelope sender following
17654 &"<="&. For local messages, the user's login always follows, after &"U="&. In
17655 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
17656 envelope sender address, the user's login is shown in parentheses after the
17657 sender address.
17658
17659
17660 .option uucp_from_pattern main string "see below"
17661 .cindex "&""From""& line"
17662 .cindex "UUCP" "&""From""& line"
17663 Some applications that pass messages to an MTA via a command line interface use
17664 an initial line starting with &"From&~"& to pass the envelope sender. In
17665 particular, this is used by UUCP software. Exim recognizes such a line by means
17666 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
17667 matches, the sender address is constructed by expanding the contents of
17668 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
17669 default pattern recognizes lines in the following two forms:
17670 .code
17671 From ph10 Fri Jan 5 12:35 GMT 1996
17672 From ph10 Fri, 7 Jan 97 14:00:00 GMT
17673 .endd
17674 The pattern can be seen by running
17675 .code
17676 exim -bP uucp_from_pattern
17677 .endd
17678 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
17679 year in the second case. The first word after &"From&~"& is matched in the
17680 regular expression by a parenthesized subpattern. The default value for
17681 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
17682 (&"ph10"& in the example above) as the message's sender. See also
17683 &%ignore_fromline_hosts%&.
17684
17685
17686 .option uucp_from_sender main string&!! &`$1`&
17687 See &%uucp_from_pattern%& above.
17688
17689
17690 .option warn_message_file main string unset
17691 .cindex "warning of delay" "customizing the message"
17692 .cindex "customizing" "warning message"
17693 This option defines a template file containing paragraphs of text to be used
17694 for constructing the warning message which is sent by Exim when a message has
17695 been on the queue for a specified amount of time, as specified by
17696 &%delay_warning%&. Details of the file's contents are given in chapter
17697 &<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
17698
17699
17700 .option write_rejectlog main boolean true
17701 .cindex "reject log" "disabling"
17702 If this option is set false, Exim no longer writes anything to the reject log.
17703 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
17704 .ecindex IIDconfima
17705 .ecindex IIDmaiconf
17706
17707
17708
17709
17710 . ////////////////////////////////////////////////////////////////////////////
17711 . ////////////////////////////////////////////////////////////////////////////
17712
17713 .chapter "Generic options for routers" "CHAProutergeneric"
17714 .scindex IIDgenoprou1 "options" "generic; for routers"
17715 .scindex IIDgenoprou2 "generic options" "router"
17716 This chapter describes the generic options that apply to all routers.
17717 Those that are preconditions are marked with &Dagger; in the &"use"& field.
17718
17719 For a general description of how a router operates, see sections
17720 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
17721 which the preconditions are tested. The order of expansion of the options that
17722 provide data for a transport is: &%errors_to%&, &%headers_add%&,
17723 &%headers_remove%&, &%transport%&.
17724
17725
17726
17727 .option address_data routers string&!! unset
17728 .cindex "router" "data attached to address"
17729 The string is expanded just before the router is run, that is, after all the
17730 precondition tests have succeeded. If the expansion is forced to fail, the
17731 router declines, the value of &%address_data%& remains unchanged, and the
17732 &%more%& option controls what happens next. Other expansion failures cause
17733 delivery of the address to be deferred.
17734
17735 .vindex "&$address_data$&"
17736 When the expansion succeeds, the value is retained with the address, and can be
17737 accessed using the variable &$address_data$& in the current router, subsequent
17738 routers, and the eventual transport.
17739
17740 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
17741 that runs a user's filter file, the contents of &$address_data$& are accessible
17742 in the filter. This is not normally a problem, because such data is usually
17743 either not confidential or it &"belongs"& to the current user, but if you do
17744 put confidential data into &$address_data$& you need to remember this point.
17745
17746 Even if the router declines or passes, the value of &$address_data$& remains
17747 with the address, though it can be changed by another &%address_data%& setting
17748 on a subsequent router. If a router generates child addresses, the value of
17749 &$address_data$& propagates to them. This also applies to the special kind of
17750 &"child"& that is generated by a router with the &%unseen%& option.
17751
17752 The idea of &%address_data%& is that you can use it to look up a lot of data
17753 for the address once, and then pick out parts of the data later. For example,
17754 you could use a single LDAP lookup to return a string of the form
17755 .code
17756 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
17757 .endd
17758 In the transport you could pick out the mailbox by a setting such as
17759 .code
17760 file = ${extract{mailbox}{$address_data}}
17761 .endd
17762 This makes the configuration file less messy, and also reduces the number of
17763 lookups (though Exim does cache lookups).
17764
17765 .vindex "&$sender_address_data$&"
17766 .vindex "&$address_data$&"
17767 The &%address_data%& facility is also useful as a means of passing information
17768 from one router to another, and from a router to a transport. In addition, if
17769 &$address_data$& is set by a router when verifying a recipient address from an
17770 ACL, it remains available for use in the rest of the ACL statement. After
17771 verifying a sender, the value is transferred to &$sender_address_data$&.
17772
17773
17774
17775 .option address_test routers&!? boolean true
17776 .oindex "&%-bt%&"
17777 .cindex "router" "skipping when address testing"
17778 If this option is set false, the router is skipped when routing is being tested
17779 by means of the &%-bt%& command line option. This can be a convenience when
17780 your first router sends messages to an external scanner, because it saves you
17781 having to set the &"already scanned"& indicator when testing real address
17782 routing.
17783
17784
17785
17786 .option cannot_route_message routers string&!! unset
17787 .cindex "router" "customizing &""cannot route""& message"
17788 .cindex "customizing" "&""cannot route""& message"
17789 This option specifies a text message that is used when an address cannot be
17790 routed because Exim has run out of routers. The default message is
17791 &"Unrouteable address"&. This option is useful only on routers that have
17792 &%more%& set false, or on the very last router in a configuration, because the
17793 value that is used is taken from the last router that is considered. This
17794 includes a router that is skipped because its preconditions are not met, as
17795 well as a router that declines. For example, using the default configuration,
17796 you could put:
17797 .code
17798 cannot_route_message = Remote domain not found in DNS
17799 .endd
17800 on the first router, which is a &(dnslookup)& router with &%more%& set false,
17801 and
17802 .code
17803 cannot_route_message = Unknown local user
17804 .endd
17805 on the final router that checks for local users. If string expansion fails for
17806 this option, the default message is used. Unless the expansion failure was
17807 explicitly forced, a message about the failure is written to the main and panic
17808 logs, in addition to the normal message about the routing failure.
17809
17810
17811 .option caseful_local_part routers boolean false
17812 .cindex "case of local parts"
17813 .cindex "router" "case of local parts"
17814 By default, routers handle the local parts of addresses in a case-insensitive
17815 manner, though the actual case is preserved for transmission with the message.
17816 If you want the case of letters to be significant in a router, you must set
17817 this option true. For individual router options that contain address or local
17818 part lists (for example, &%local_parts%&), case-sensitive matching can be
17819 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
17820 more details.
17821
17822 .vindex "&$local_part$&"
17823 .vindex "&$original_local_part$&"
17824 .vindex "&$parent_local_part$&"
17825 The value of the &$local_part$& variable is forced to lower case while a
17826 router is running unless &%caseful_local_part%& is set. When a router assigns
17827 an address to a transport, the value of &$local_part$& when the transport runs
17828 is the same as it was in the router. Similarly, when a router generates child
17829 addresses by aliasing or forwarding, the values of &$original_local_part$&
17830 and &$parent_local_part$& are those that were used by the redirecting router.
17831
17832 This option applies to the processing of an address by a router. When a
17833 recipient address is being processed in an ACL, there is a separate &%control%&
17834 modifier that can be used to specify case-sensitive processing within the ACL
17835 (see section &<<SECTcontrols>>&).
17836
17837
17838
17839 .option check_local_user routers&!? boolean false
17840 .cindex "local user, checking in router"
17841 .cindex "router" "checking for local user"
17842 .cindex "&_/etc/passwd_&"
17843 .vindex "&$home$&"
17844 When this option is true, Exim checks that the local part of the recipient
17845 address (with affixes removed if relevant) is the name of an account on the
17846 local system. The check is done by calling the &[getpwnam()]& function rather
17847 than trying to read &_/etc/passwd_& directly. This means that other methods of
17848 holding password data (such as NIS) are supported. If the local part is a local
17849 user, &$home$& is set from the password data, and can be tested in other
17850 preconditions that are evaluated after this one (the order of evaluation is
17851 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
17852 overridden by &%router_home_directory%&. If the local part is not a local user,
17853 the router is skipped.
17854
17855 If you want to check that the local part is either the name of a local user
17856 or matches something else, you cannot combine &%check_local_user%& with a
17857 setting of &%local_parts%&, because that specifies the logical &'and'& of the
17858 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
17859 setting to achieve this. For example:
17860 .code
17861 local_parts = passwd;$local_part : lsearch;/etc/other/users
17862 .endd
17863 Note, however, that the side effects of &%check_local_user%& (such as setting
17864 up a home directory) do not occur when a &(passwd)& lookup is used in a
17865 &%local_parts%& (or any other) precondition.
17866
17867
17868
17869 .option condition routers&!? string&!! unset
17870 .cindex "router" "customized precondition"
17871 This option specifies a general precondition test that has to succeed for the
17872 router to be called. The &%condition%& option is the last precondition to be
17873 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
17874 result is a forced failure, or an empty string, or one of the strings &"0"& or
17875 &"no"& or &"false"& (checked without regard to the case of the letters), the
17876 router is skipped, and the address is offered to the next one.
17877
17878 If the result is any other value, the router is run (as this is the last
17879 precondition to be evaluated, all the other preconditions must be true).
17880
17881 This option is unusual in that multiple &%condition%& options may be present.
17882 All &%condition%& options must succeed.
17883
17884 The &%condition%& option provides a means of applying custom conditions to the
17885 running of routers. Note that in the case of a simple conditional expansion,
17886 the default expansion values are exactly what is wanted. For example:
17887 .code
17888 condition = ${if >{$message_age}{600}}
17889 .endd
17890 Because of the default behaviour of the string expansion, this is equivalent to
17891 .code
17892 condition = ${if >{$message_age}{600}{true}{}}
17893 .endd
17894
17895 A multiple condition example, which succeeds:
17896 .code
17897 condition = ${if >{$message_age}{600}}
17898 condition = ${if !eq{${lc:$local_part}}{postmaster}}
17899 condition = foobar
17900 .endd
17901
17902 If the expansion fails (other than forced failure) delivery is deferred. Some
17903 of the other precondition options are common special cases that could in fact
17904 be specified using &%condition%&.
17905
17906 Historical note: We have &%condition%& on ACLs and on Routers. Routers
17907 are far older, and use one set of semantics. ACLs are newer and when
17908 they were created, the ACL &%condition%& process was given far stricter
17909 parse semantics. The &%bool{}%& expansion condition uses the same rules as
17910 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
17911 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
17912 Router rules processing behavior.
17913
17914 This is best illustrated in an example:
17915 .code
17916 # If used in an ACL condition will fail with a syntax error, but
17917 # in a router condition any extra characters are treated as a string
17918
17919 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
17920 true {yes} {no}}
17921
17922 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
17923 {yes} {no}}
17924 .endd
17925 In each example above, the &%if%& statement actually ends after
17926 &"{google.com}}"&. Since no true or false braces were defined, the
17927 default &%if%& behavior is to return a boolean true or a null answer
17928 (which evaluates to false). The rest of the line is then treated as a
17929 string. So the first example resulted in the boolean answer &"true"&
17930 with the string &" {yes} {no}}"& appended to it. The second example
17931 resulted in the null output (indicating false) with the string
17932 &" {yes} {no}}"& appended to it.
17933
17934 In fact you can put excess forward braces in too. In the router
17935 &%condition%&, Exim's parser only looks for &"{"& symbols when they
17936 mean something, like after a &"$"& or when required as part of a
17937 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
17938 string characters.
17939
17940 Thus, in a Router, the above expansion strings will both always evaluate
17941 true, as the result of expansion is a non-empty string which doesn't
17942 match an explicit false value. This can be tricky to debug. By
17943 contrast, in an ACL either of those strings will always result in an
17944 expansion error because the result doesn't look sufficiently boolean.
17945
17946
17947 .option debug_print routers string&!! unset
17948 .cindex "testing" "variables in drivers"
17949 If this option is set and debugging is enabled (see the &%-d%& command line
17950 option) or in address-testing mode (see the &%-bt%& command line option),
17951 the string is expanded and included in the debugging output.
17952 If expansion of the string fails, the error message is written to the debugging
17953 output, and Exim carries on processing.
17954 This option is provided to help with checking out the values of variables and
17955 so on when debugging router configurations. For example, if a &%condition%&
17956 option appears not to be working, &%debug_print%& can be used to output the
17957 variables it references. The output happens after checks for &%domains%&,
17958 &%local_parts%&, and &%check_local_user%& but before any other preconditions
17959 are tested. A newline is added to the text if it does not end with one.
17960 The variable &$router_name$& contains the name of the router.
17961
17962
17963
17964 .option disable_logging routers boolean false
17965 If this option is set true, nothing is logged for any routing errors
17966 or for any deliveries caused by this router. You should not set this option
17967 unless you really, really know what you are doing. See also the generic
17968 transport option of the same name.
17969
17970 .option dnssec_request_domains routers "domain list&!!" unset
17971 .cindex "MX record" "security"
17972 .cindex "DNSSEC" "MX lookup"
17973 .cindex "security" "MX lookup"
17974 .cindex "DNS" "DNSSEC"
17975 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
17976 the dnssec request bit set.
17977 This applies to all of the SRV, MX, AAAA, A lookup sequence.
17978
17979 .option dnssec_require_domains routers "domain list&!!" unset
17980 .cindex "MX record" "security"
17981 .cindex "DNSSEC" "MX lookup"
17982 .cindex "security" "MX lookup"
17983 .cindex "DNS" "DNSSEC"
17984 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
17985 the dnssec request bit set. Any returns not having the Authenticated Data bit
17986 (AD bit) set will be ignored and logged as a host-lookup failure.
17987 This applies to all of the SRV, MX, AAAA, A lookup sequence.
17988
17989
17990 .option domains routers&!? "domain list&!!" unset
17991 .cindex "router" "restricting to specific domains"
17992 .vindex "&$domain_data$&"
17993 If this option is set, the router is skipped unless the current domain matches
17994 the list. If the match is achieved by means of a file lookup, the data that the
17995 lookup returned for the domain is placed in &$domain_data$& for use in string
17996 expansions of the driver's private options. See section &<<SECTrouprecon>>& for
17997 a list of the order in which preconditions are evaluated.
17998
17999
18000
18001 .option driver routers string unset
18002 This option must always be set. It specifies which of the available routers is
18003 to be used.
18004
18005
18006 .option dsn_lasthop routers boolean false
18007 .cindex "DSN" "success"
18008 .cindex "Delivery Status Notification" "success"
18009 If this option is set true, and extended DSN (RFC3461) processing is in effect,
18010 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
18011 instead send a success DSN as if the next hop does not support DSN.
18012 Not effective on redirect routers.
18013
18014
18015
18016 .option errors_to routers string&!! unset
18017 .cindex "envelope sender"
18018 .cindex "router" "changing address for errors"
18019 If a router successfully handles an address, it may assign the address to a
18020 transport for delivery or it may generate child addresses. In both cases, if
18021 there is a delivery problem during later processing, the resulting bounce
18022 message is sent to the address that results from expanding this string,
18023 provided that the address verifies successfully. The &%errors_to%& option is
18024 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
18025
18026 The &%errors_to%& setting associated with an address can be overridden if it
18027 subsequently passes through other routers that have their own &%errors_to%&
18028 settings, or if the message is delivered by a transport with a &%return_path%&
18029 setting.
18030
18031 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
18032 the expansion fails to verify, the errors address associated with the incoming
18033 address is used. At top level, this is the envelope sender. A non-forced
18034 expansion failure causes delivery to be deferred.
18035
18036 If an address for which &%errors_to%& has been set ends up being delivered over
18037 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
18038 any bounces that are generated by other MTAs on the delivery route are also
18039 sent there. You can set &%errors_to%& to the empty string by either of these
18040 settings:
18041 .code
18042 errors_to =
18043 errors_to = ""
18044 .endd
18045 An expansion item that yields an empty string has the same effect. If you do
18046 this, a locally detected delivery error for addresses processed by this router
18047 no longer gives rise to a bounce message; the error is discarded. If the
18048 address is delivered to a remote host, the return path is set to &`<>`&, unless
18049 overridden by the &%return_path%& option on the transport.
18050
18051 .vindex "&$address_data$&"
18052 If for some reason you want to discard local errors, but use a non-empty
18053 MAIL command for remote delivery, you can preserve the original return
18054 path in &$address_data$& in the router, and reinstate it in the transport by
18055 setting &%return_path%&.
18056
18057 The most common use of &%errors_to%& is to direct mailing list bounces to the
18058 manager of the list, as described in section &<<SECTmailinglists>>&, or to
18059 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
18060
18061
18062
18063 .option expn routers&!? boolean true
18064 .cindex "address" "testing"
18065 .cindex "testing" "addresses"
18066 .cindex "EXPN" "router skipping"
18067 .cindex "router" "skipping for EXPN"
18068 If this option is turned off, the router is skipped when testing an address
18069 as a result of processing an SMTP EXPN command. You might, for example,
18070 want to turn it off on a router for users' &_.forward_& files, while leaving it
18071 on for the system alias file.
18072 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18073 are evaluated.
18074
18075 The use of the SMTP EXPN command is controlled by an ACL (see chapter
18076 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
18077 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
18078
18079
18080
18081 .option fail_verify routers boolean false
18082 .cindex "router" "forcing verification failure"
18083 Setting this option has the effect of setting both &%fail_verify_sender%& and
18084 &%fail_verify_recipient%& to the same value.
18085
18086
18087
18088 .option fail_verify_recipient routers boolean false
18089 If this option is true and an address is accepted by this router when
18090 verifying a recipient, verification fails.
18091
18092
18093
18094 .option fail_verify_sender routers boolean false
18095 If this option is true and an address is accepted by this router when
18096 verifying a sender, verification fails.
18097
18098
18099
18100 .option fallback_hosts routers "string list" unset
18101 .cindex "router" "fallback hosts"
18102 .cindex "fallback" "hosts specified on router"
18103 String expansion is not applied to this option. The argument must be a
18104 colon-separated list of host names or IP addresses. The list separator can be
18105 changed (see section &<<SECTlistconstruct>>&), and a port can be specified with
18106 each name or address. In fact, the format of each item is exactly the same as
18107 defined for the list of hosts in a &(manualroute)& router (see section
18108 &<<SECTformatonehostitem>>&).
18109
18110 If a router queues an address for a remote transport, this host list is
18111 associated with the address, and used instead of the transport's fallback host
18112 list. If &%hosts_randomize%& is set on the transport, the order of the list is
18113 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
18114 transport for further details.
18115
18116
18117 .option group routers string&!! "see below"
18118 .cindex "gid (group id)" "local delivery"
18119 .cindex "local transports" "uid and gid"
18120 .cindex "transport" "local"
18121 .cindex "router" "setting group"
18122 When a router queues an address for a transport, and the transport does not
18123 specify a group, the group given here is used when running the delivery
18124 process.
18125 The group may be specified numerically or by name. If expansion fails, the
18126 error is logged and delivery is deferred.
18127 The default is unset, unless &%check_local_user%& is set, when the default
18128 is taken from the password information. See also &%initgroups%& and &%user%&
18129 and the discussion in chapter &<<CHAPenvironment>>&.
18130
18131
18132
18133 .option headers_add routers list&!! unset
18134 .cindex "header lines" "adding"
18135 .cindex "router" "adding header lines"
18136 This option specifies a list of text headers,
18137 newline-separated (by default, changeable in the usual way),
18138 that is associated with any addresses that are accepted by the router.
18139 Each item is separately expanded, at routing time. However, this
18140 option has no effect when an address is just being verified. The way in which
18141 the text is used to add header lines at transport time is described in section
18142 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
18143 message is in the process of being transported. This means that references to
18144 header lines in string expansions in the transport's configuration do not
18145 &"see"& the added header lines.
18146
18147 The &%headers_add%& option is expanded after &%errors_to%&, but before
18148 &%headers_remove%& and &%transport%&. If an item is empty, or if
18149 an item expansion is forced to fail, the item has no effect. Other expansion
18150 failures are treated as configuration errors.
18151
18152 Unlike most options, &%headers_add%& can be specified multiple times
18153 for a router; all listed headers are added.
18154
18155 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
18156 router that has the &%one_time%& option set.
18157
18158 .cindex "duplicate addresses"
18159 .oindex "&%unseen%&"
18160 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
18161 additions are deleted when the address is passed on to subsequent routers.
18162 For a &%redirect%& router, if a generated address is the same as the incoming
18163 address, this can lead to duplicate addresses with different header
18164 modifications. Exim does not do duplicate deliveries (except, in certain
18165 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
18166 which of the duplicates is discarded, so this ambiguous situation should be
18167 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
18168
18169
18170
18171 .option headers_remove routers list&!! unset
18172 .cindex "header lines" "removing"
18173 .cindex "router" "removing header lines"
18174 This option specifies a list of text headers,
18175 colon-separated (by default, changeable in the usual way),
18176 that is associated with any addresses that are accepted by the router.
18177 Each item is separately expanded, at routing time. However, this
18178 option has no effect when an address is just being verified. The way in which
18179 the text is used to remove header lines at transport time is described in
18180 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
18181 the message is in the process of being transported. This means that references
18182 to header lines in string expansions in the transport's configuration still
18183 &"see"& the original header lines.
18184
18185 The &%headers_remove%& option is expanded after &%errors_to%& and
18186 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
18187 the item has no effect. Other expansion failures are treated as configuration
18188 errors.
18189
18190 Unlike most options, &%headers_remove%& can be specified multiple times
18191 for a router; all listed headers are removed.
18192
18193 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
18194 router that has the &%one_time%& option set.
18195
18196 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
18197 removal requests are deleted when the address is passed on to subsequent
18198 routers, and this can lead to problems with duplicates -- see the similar
18199 warning for &%headers_add%& above.
18200
18201 &*Warning 3*&: Because of the separate expansion of the list items,
18202 items that contain a list separator must have it doubled.
18203 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
18204
18205
18206
18207 .option ignore_target_hosts routers "host list&!!" unset
18208 .cindex "IP address" "discarding"
18209 .cindex "router" "discarding IP addresses"
18210 Although this option is a host list, it should normally contain IP address
18211 entries rather than names. If any host that is looked up by the router has an
18212 IP address that matches an item in this list, Exim behaves as if that IP
18213 address did not exist. This option allows you to cope with rogue DNS entries
18214 like
18215 .code
18216 remote.domain.example. A 127.0.0.1
18217 .endd
18218 by setting
18219 .code
18220 ignore_target_hosts = 127.0.0.1
18221 .endd
18222 on the relevant router. If all the hosts found by a &(dnslookup)& router are
18223 discarded in this way, the router declines. In a conventional configuration, an
18224 attempt to mail to such a domain would normally provoke the &"unrouteable
18225 domain"& error, and an attempt to verify an address in the domain would fail.
18226 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
18227 router declines if presented with one of the listed addresses.
18228
18229 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
18230 means of the first or the second of the following settings, respectively:
18231 .code
18232 ignore_target_hosts = 0.0.0.0/0
18233 ignore_target_hosts = <; 0::0/0
18234 .endd
18235 The pattern in the first line matches all IPv4 addresses, whereas the pattern
18236 in the second line matches all IPv6 addresses.
18237
18238 This option may also be useful for ignoring link-local and site-local IPv6
18239 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
18240 is expanded before use as a list, it is possible to make it dependent on the
18241 domain that is being routed.
18242
18243 .vindex "&$host_address$&"
18244 During its expansion, &$host_address$& is set to the IP address that is being
18245 checked.
18246
18247 .option initgroups routers boolean false
18248 .cindex "additional groups"
18249 .cindex "groups" "additional"
18250 .cindex "local transports" "uid and gid"
18251 .cindex "transport" "local"
18252 If the router queues an address for a transport, and this option is true, and
18253 the uid supplied by the router is not overridden by the transport, the
18254 &[initgroups()]& function is called when running the transport to ensure that
18255 any additional groups associated with the uid are set up. See also &%group%&
18256 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
18257
18258
18259
18260 .option local_part_prefix routers&!? "string list" unset
18261 .cindex "router" "prefix for local part"
18262 .cindex "prefix" "for local part, used in router"
18263 If this option is set, the router is skipped unless the local part starts with
18264 one of the given strings, or &%local_part_prefix_optional%& is true. See
18265 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
18266 evaluated.
18267
18268 The list is scanned from left to right, and the first prefix that matches is
18269 used. A limited form of wildcard is available; if the prefix begins with an
18270 asterisk, it matches the longest possible sequence of arbitrary characters at
18271 the start of the local part. An asterisk should therefore always be followed by
18272 some character that does not occur in normal local parts.
18273 .cindex "multiple mailboxes"
18274 .cindex "mailbox" "multiple"
18275 Wildcarding can be used to set up multiple user mailboxes, as described in
18276 section &<<SECTmulbox>>&.
18277
18278 .vindex "&$local_part$&"
18279 .vindex "&$local_part_prefix$&"
18280 During the testing of the &%local_parts%& option, and while the router is
18281 running, the prefix is removed from the local part, and is available in the
18282 expansion variable &$local_part_prefix$&. When a message is being delivered, if
18283 the router accepts the address, this remains true during subsequent delivery by
18284 a transport. In particular, the local part that is transmitted in the RCPT
18285 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
18286 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
18287 the relevant transport.
18288
18289 When an address is being verified, &%local_part_prefix%& affects only the
18290 behaviour of the router. If the callout feature of verification is in use, this
18291 means that the full address, including the prefix, will be used during the
18292 callout.
18293
18294 The prefix facility is commonly used to handle local parts of the form
18295 &%owner-something%&. Another common use is to support local parts of the form
18296 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
18297 to tell a user their forwarding is broken &-- by placing a router like this one
18298 immediately before the router that handles &_.forward_& files:
18299 .code
18300 real_localuser:
18301 driver = accept
18302 local_part_prefix = real-
18303 check_local_user
18304 transport = local_delivery
18305 .endd
18306 For security, it would probably be a good idea to restrict the use of this
18307 router to locally-generated messages, using a condition such as this:
18308 .code
18309 condition = ${if match {$sender_host_address}\
18310 {\N^(|127\.0\.0\.1)$\N}}
18311 .endd
18312
18313 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
18314 both conditions must be met if not optional. Care must be taken if wildcards
18315 are used in both a prefix and a suffix on the same router. Different
18316 separator characters must be used to avoid ambiguity.
18317
18318
18319 .option local_part_prefix_optional routers boolean false
18320 See &%local_part_prefix%& above.
18321
18322
18323
18324 .option local_part_suffix routers&!? "string list" unset
18325 .cindex "router" "suffix for local part"
18326 .cindex "suffix for local part" "used in router"
18327 This option operates in the same way as &%local_part_prefix%&, except that the
18328 local part must end (rather than start) with the given string, the
18329 &%local_part_suffix_optional%& option determines whether the suffix is
18330 mandatory, and the wildcard * character, if present, must be the last
18331 character of the suffix. This option facility is commonly used to handle local
18332 parts of the form &%something-request%& and multiple user mailboxes of the form
18333 &%username-foo%&.
18334
18335
18336 .option local_part_suffix_optional routers boolean false
18337 See &%local_part_suffix%& above.
18338
18339
18340
18341 .option local_parts routers&!? "local part list&!!" unset
18342 .cindex "router" "restricting to specific local parts"
18343 .cindex "local part" "checking in router"
18344 The router is run only if the local part of the address matches the list.
18345 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18346 are evaluated, and
18347 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
18348 string is expanded, it is possible to make it depend on the domain, for
18349 example:
18350 .code
18351 local_parts = dbm;/usr/local/specials/$domain
18352 .endd
18353 .vindex "&$local_part_data$&"
18354 If the match is achieved by a lookup, the data that the lookup returned
18355 for the local part is placed in the variable &$local_part_data$& for use in
18356 expansions of the router's private options. You might use this option, for
18357 example, if you have a large number of local virtual domains, and you want to
18358 send all postmaster mail to the same place without having to set up an alias in
18359 each virtual domain:
18360 .code
18361 postmaster:
18362 driver = redirect
18363 local_parts = postmaster
18364 data = postmaster@real.domain.example
18365 .endd
18366
18367
18368 .option log_as_local routers boolean "see below"
18369 .cindex "log" "delivery line"
18370 .cindex "delivery" "log line format"
18371 Exim has two logging styles for delivery, the idea being to make local
18372 deliveries stand out more visibly from remote ones. In the &"local"& style, the
18373 recipient address is given just as the local part, without a domain. The use of
18374 this style is controlled by this option. It defaults to true for the &(accept)&
18375 router, and false for all the others. This option applies only when a
18376 router assigns an address to a transport. It has no effect on routers that
18377 redirect addresses.
18378
18379
18380
18381 .option more routers boolean&!! true
18382 The result of string expansion for this option must be a valid boolean value,
18383 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
18384 result causes an error, and delivery is deferred. If the expansion is forced to
18385 fail, the default value for the option (true) is used. Other failures cause
18386 delivery to be deferred.
18387
18388 If this option is set false, and the router declines to handle the address, no
18389 further routers are tried, routing fails, and the address is bounced.
18390 .oindex "&%self%&"
18391 However, if the router explicitly passes an address to the following router by
18392 means of the setting
18393 .code
18394 self = pass
18395 .endd
18396 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
18397 does not affect the behaviour if one of the precondition tests fails. In that
18398 case, the address is always passed to the next router.
18399
18400 Note that &%address_data%& is not considered to be a precondition. If its
18401 expansion is forced to fail, the router declines, and the value of &%more%&
18402 controls what happens next.
18403
18404
18405 .option pass_on_timeout routers boolean false
18406 .cindex "timeout" "of router"
18407 .cindex "router" "timeout"
18408 If a router times out during a host lookup, it normally causes deferral of the
18409 address. If &%pass_on_timeout%& is set, the address is passed on to the next
18410 router, overriding &%no_more%&. This may be helpful for systems that are
18411 intermittently connected to the Internet, or those that want to pass to a smart
18412 host any messages that cannot immediately be delivered.
18413
18414 There are occasional other temporary errors that can occur while doing DNS
18415 lookups. They are treated in the same way as a timeout, and this option
18416 applies to all of them.
18417
18418
18419
18420 .option pass_router routers string unset
18421 .cindex "router" "go to after &""pass""&"
18422 Routers that recognize the generic &%self%& option (&(dnslookup)&,
18423 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
18424 routing to continue, and overriding a false setting of &%more%&. When one of
18425 these routers returns &"pass"&, the address is normally handed on to the next
18426 router in sequence. This can be changed by setting &%pass_router%& to the name
18427 of another router. However (unlike &%redirect_router%&) the named router must
18428 be below the current router, to avoid loops. Note that this option applies only
18429 to the special case of &"pass"&. It does not apply when a router returns
18430 &"decline"& because it cannot handle an address.
18431
18432
18433
18434 .option redirect_router routers string unset
18435 .cindex "router" "start at after redirection"
18436 Sometimes an administrator knows that it is pointless to reprocess addresses
18437 generated from alias or forward files with the same router again. For
18438 example, if an alias file translates real names into login ids there is no
18439 point searching the alias file a second time, especially if it is a large file.
18440
18441 The &%redirect_router%& option can be set to the name of any router instance.
18442 It causes the routing of any generated addresses to start at the named router
18443 instead of at the first router. This option has no effect if the router in
18444 which it is set does not generate new addresses.
18445
18446
18447
18448 .option require_files routers&!? "string list&!!" unset
18449 .cindex "file" "requiring for router"
18450 .cindex "router" "requiring file existence"
18451 This option provides a general mechanism for predicating the running of a
18452 router on the existence or non-existence of certain files or directories.
18453 Before running a router, as one of its precondition tests, Exim works its way
18454 through the &%require_files%& list, expanding each item separately.
18455
18456 Because the list is split before expansion, any colons in expansion items must
18457 be doubled, or the facility for using a different list separator must be used.
18458 If any expansion is forced to fail, the item is ignored. Other expansion
18459 failures cause routing of the address to be deferred.
18460
18461 If any expanded string is empty, it is ignored. Otherwise, except as described
18462 below, each string must be a fully qualified file path, optionally preceded by
18463 &"!"&. The paths are passed to the &[stat()]& function to test for the
18464 existence of the files or directories. The router is skipped if any paths not
18465 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
18466
18467 .cindex "NFS"
18468 If &[stat()]& cannot determine whether a file exists or not, delivery of
18469 the message is deferred. This can happen when NFS-mounted filesystems are
18470 unavailable.
18471
18472 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
18473 options, so you cannot use it to check for the existence of a file in which to
18474 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
18475 full list of the order in which preconditions are evaluated.) However, as
18476 these options are all expanded, you can use the &%exists%& expansion condition
18477 to make such tests. The &%require_files%& option is intended for checking files
18478 that the router may be going to use internally, or which are needed by a
18479 transport (for example &_.procmailrc_&).
18480
18481 During delivery, the &[stat()]& function is run as root, but there is a
18482 facility for some checking of the accessibility of a file by another user.
18483 This is not a proper permissions check, but just a &"rough"& check that
18484 operates as follows:
18485
18486 If an item in a &%require_files%& list does not contain any forward slash
18487 characters, it is taken to be the user (and optional group, separated by a
18488 comma) to be checked for subsequent files in the list. If no group is specified
18489 but the user is specified symbolically, the gid associated with the uid is
18490 used. For example:
18491 .code
18492 require_files = mail:/some/file
18493 require_files = $local_part:$home/.procmailrc
18494 .endd
18495 If a user or group name in a &%require_files%& list does not exist, the
18496 &%require_files%& condition fails.
18497
18498 Exim performs the check by scanning along the components of the file path, and
18499 checking the access for the given uid and gid. It checks for &"x"& access on
18500 directories, and &"r"& access on the final file. Note that this means that file
18501 access control lists, if the operating system has them, are ignored.
18502
18503 &*Warning 1*&: When the router is being run to verify addresses for an
18504 incoming SMTP message, Exim is not running as root, but under its own uid. This
18505 may affect the result of a &%require_files%& check. In particular, &[stat()]&
18506 may yield the error EACCES (&"Permission denied"&). This means that the Exim
18507 user is not permitted to read one of the directories on the file's path.
18508
18509 &*Warning 2*&: Even when Exim is running as root while delivering a message,
18510 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
18511 without root access. In this case, if a check for access by a particular user
18512 is requested, Exim creates a subprocess that runs as that user, and tries the
18513 check again in that process.
18514
18515 The default action for handling an unresolved EACCES is to consider it to
18516 be caused by a configuration error, and routing is deferred because the
18517 existence or non-existence of the file cannot be determined. However, in some
18518 circumstances it may be desirable to treat this condition as if the file did
18519 not exist. If the file name (or the exclamation mark that precedes the file
18520 name for non-existence) is preceded by a plus sign, the EACCES error is treated
18521 as if the file did not exist. For example:
18522 .code
18523 require_files = +/some/file
18524 .endd
18525 If the router is not an essential part of verification (for example, it
18526 handles users' &_.forward_& files), another solution is to set the &%verify%&
18527 option false so that the router is skipped when verifying.
18528
18529
18530
18531 .option retry_use_local_part routers boolean "see below"
18532 .cindex "hints database" "retry keys"
18533 .cindex "local part" "in retry keys"
18534 When a delivery suffers a temporary routing failure, a retry record is created
18535 in Exim's hints database. For addresses whose routing depends only on the
18536 domain, the key for the retry record should not involve the local part, but for
18537 other addresses, both the domain and the local part should be included.
18538 Usually, remote routing is of the former kind, and local routing is of the
18539 latter kind.
18540
18541 This option controls whether the local part is used to form the key for retry
18542 hints for addresses that suffer temporary errors while being handled by this
18543 router. The default value is true for any router that has &%check_local_user%&
18544 set, and false otherwise. Note that this option does not apply to hints keys
18545 for transport delays; they are controlled by a generic transport option of the
18546 same name.
18547
18548 The setting of &%retry_use_local_part%& applies only to the router on which it
18549 appears. If the router generates child addresses, they are routed
18550 independently; this setting does not become attached to them.
18551
18552
18553
18554 .option router_home_directory routers string&!! unset
18555 .cindex "router" "home directory for"
18556 .cindex "home directory" "for router"
18557 .vindex "&$home$&"
18558 This option sets a home directory for use while the router is running. (Compare
18559 &%transport_home_directory%&, which sets a home directory for later
18560 transporting.) In particular, if used on a &(redirect)& router, this option
18561 sets a value for &$home$& while a filter is running. The value is expanded;
18562 forced expansion failure causes the option to be ignored &-- other failures
18563 cause the router to defer.
18564
18565 Expansion of &%router_home_directory%& happens immediately after the
18566 &%check_local_user%& test (if configured), before any further expansions take
18567 place.
18568 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18569 are evaluated.)
18570 While the router is running, &%router_home_directory%& overrides the value of
18571 &$home$& that came from &%check_local_user%&.
18572
18573 When a router accepts an address and assigns it to a local transport (including
18574 the cases when a &(redirect)& router generates a pipe, file, or autoreply
18575 delivery), the home directory setting for the transport is taken from the first
18576 of these values that is set:
18577
18578 .ilist
18579 The &%home_directory%& option on the transport;
18580 .next
18581 The &%transport_home_directory%& option on the router;
18582 .next
18583 The password data if &%check_local_user%& is set on the router;
18584 .next
18585 The &%router_home_directory%& option on the router.
18586 .endlist
18587
18588 In other words, &%router_home_directory%& overrides the password data for the
18589 router, but not for the transport.
18590
18591
18592
18593 .option self routers string freeze
18594 .cindex "MX record" "pointing to local host"
18595 .cindex "local host" "MX pointing to"
18596 This option applies to those routers that use a recipient address to find a
18597 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
18598 and &(manualroute)& routers.
18599 Certain configurations of the &(queryprogram)& router can also specify a list
18600 of remote hosts.
18601 Usually such routers are configured to send the message to a remote host via an
18602 &(smtp)& transport. The &%self%& option specifies what happens when the first
18603 host on the list turns out to be the local host.
18604 The way in which Exim checks for the local host is described in section
18605 &<<SECTreclocipadd>>&.
18606
18607 Normally this situation indicates either an error in Exim's configuration (for
18608 example, the router should be configured not to process this domain), or an
18609 error in the DNS (for example, the MX should not point to this host). For this
18610 reason, the default action is to log the incident, defer the address, and
18611 freeze the message. The following alternatives are provided for use in special
18612 cases:
18613
18614 .vlist
18615 .vitem &%defer%&
18616 Delivery of the message is tried again later, but the message is not frozen.
18617
18618 .vitem "&%reroute%&: <&'domain'&>"
18619 The domain is changed to the given domain, and the address is passed back to
18620 be reprocessed by the routers. No rewriting of headers takes place. This
18621 behaviour is essentially a redirection.
18622
18623 .vitem "&%reroute: rewrite:%& <&'domain'&>"
18624 The domain is changed to the given domain, and the address is passed back to be
18625 reprocessed by the routers. Any headers that contain the original domain are
18626 rewritten.
18627
18628 .vitem &%pass%&
18629 .oindex "&%more%&"
18630 .vindex "&$self_hostname$&"
18631 The router passes the address to the next router, or to the router named in the
18632 &%pass_router%& option if it is set. This overrides &%no_more%&. During
18633 subsequent routing and delivery, the variable &$self_hostname$& contains the
18634 name of the local host that the router encountered. This can be used to
18635 distinguish between different cases for hosts with multiple names. The
18636 combination
18637 .code
18638 self = pass
18639 no_more
18640 .endd
18641 ensures that only those addresses that routed to the local host are passed on.
18642 Without &%no_more%&, addresses that were declined for other reasons would also
18643 be passed to the next router.
18644
18645 .vitem &%fail%&
18646 Delivery fails and an error report is generated.
18647
18648 .vitem &%send%&
18649 .cindex "local host" "sending to"
18650 The anomaly is ignored and the address is queued for the transport. This
18651 setting should be used with extreme caution. For an &(smtp)& transport, it
18652 makes sense only in cases where the program that is listening on the SMTP port
18653 is not this version of Exim. That is, it must be some other MTA, or Exim with a
18654 different configuration file that handles the domain in another way.
18655 .endlist
18656
18657
18658
18659 .option senders routers&!? "address list&!!" unset
18660 .cindex "router" "checking senders"
18661 If this option is set, the router is skipped unless the message's sender
18662 address matches something on the list.
18663 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18664 are evaluated.
18665
18666 There are issues concerning verification when the running of routers is
18667 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
18668 setting, it sets the sender to the null string. When using the &%-bt%& option
18669 to check a configuration file, it is necessary also to use the &%-f%& option to
18670 set an appropriate sender. For incoming mail, the sender is unset when
18671 verifying the sender, but is available when verifying any recipients. If the
18672 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
18673 matters.
18674
18675
18676 .option translate_ip_address routers string&!! unset
18677 .cindex "IP address" "translating"
18678 .cindex "packet radio"
18679 .cindex "router" "IP address translation"
18680 There exist some rare networking situations (for example, packet radio) where
18681 it is helpful to be able to translate IP addresses generated by normal routing
18682 mechanisms into other IP addresses, thus performing a kind of manual IP
18683 routing. This should be done only if the normal IP routing of the TCP/IP stack
18684 is inadequate or broken. Because this is an extremely uncommon requirement, the
18685 code to support this option is not included in the Exim binary unless
18686 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
18687
18688 .vindex "&$host_address$&"
18689 The &%translate_ip_address%& string is expanded for every IP address generated
18690 by the router, with the generated address set in &$host_address$&. If the
18691 expansion is forced to fail, no action is taken.
18692 For any other expansion error, delivery of the message is deferred.
18693 If the result of the expansion is an IP address, that replaces the original
18694 address; otherwise the result is assumed to be a host name &-- this is looked
18695 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
18696 produce one or more replacement IP addresses. For example, to subvert all IP
18697 addresses in some specific networks, this could be added to a router:
18698 .code
18699 translate_ip_address = \
18700 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
18701 {$value}fail}}
18702 .endd
18703 The file would contain lines like
18704 .code
18705 10.2.3.128/26 some.host
18706 10.8.4.34/26 10.44.8.15
18707 .endd
18708 You should not make use of this facility unless you really understand what you
18709 are doing.
18710
18711
18712
18713 .option transport routers string&!! unset
18714 This option specifies the transport to be used when a router accepts an address
18715 and sets it up for delivery. A transport is never needed if a router is used
18716 only for verification. The value of the option is expanded at routing time,
18717 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
18718 and result must be the name of one of the configured transports. If it is not,
18719 delivery is deferred.
18720
18721 The &%transport%& option is not used by the &(redirect)& router, but it does
18722 have some private options that set up transports for pipe and file deliveries
18723 (see chapter &<<CHAPredirect>>&).
18724
18725
18726
18727 .option transport_current_directory routers string&!! unset
18728 .cindex "current directory for local transport"
18729 This option associates a current directory with any address that is routed
18730 to a local transport. This can happen either because a transport is
18731 explicitly configured for the router, or because it generates a delivery to a
18732 file or a pipe. During the delivery process (that is, at transport time), this
18733 option string is expanded and is set as the current directory, unless
18734 overridden by a setting on the transport.
18735 If the expansion fails for any reason, including forced failure, an error is
18736 logged, and delivery is deferred.
18737 See chapter &<<CHAPenvironment>>& for details of the local delivery
18738 environment.
18739
18740
18741
18742
18743 .option transport_home_directory routers string&!! "see below"
18744 .cindex "home directory" "for local transport"
18745 This option associates a home directory with any address that is routed to a
18746 local transport. This can happen either because a transport is explicitly
18747 configured for the router, or because it generates a delivery to a file or a
18748 pipe. During the delivery process (that is, at transport time), the option
18749 string is expanded and is set as the home directory, unless overridden by a
18750 setting of &%home_directory%& on the transport.
18751 If the expansion fails for any reason, including forced failure, an error is
18752 logged, and delivery is deferred.
18753
18754 If the transport does not specify a home directory, and
18755 &%transport_home_directory%& is not set for the router, the home directory for
18756 the transport is taken from the password data if &%check_local_user%& is set for
18757 the router. Otherwise it is taken from &%router_home_directory%& if that option
18758 is set; if not, no home directory is set for the transport.
18759
18760 See chapter &<<CHAPenvironment>>& for further details of the local delivery
18761 environment.
18762
18763
18764
18765
18766 .option unseen routers boolean&!! false
18767 .cindex "router" "carrying on after success"
18768 The result of string expansion for this option must be a valid boolean value,
18769 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
18770 result causes an error, and delivery is deferred. If the expansion is forced to
18771 fail, the default value for the option (false) is used. Other failures cause
18772 delivery to be deferred.
18773
18774 When this option is set true, routing does not cease if the router accepts the
18775 address. Instead, a copy of the incoming address is passed to the next router,
18776 overriding a false setting of &%more%&. There is little point in setting
18777 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
18778 the value of &%unseen%& contains expansion items (and therefore, presumably, is
18779 sometimes true and sometimes false).
18780
18781 .cindex "copy of message (&%unseen%& option)"
18782 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
18783 qualifier in filter files. It can be used to cause copies of messages to be
18784 delivered to some other destination, while also carrying out a normal delivery.
18785 In effect, the current address is made into a &"parent"& that has two children
18786 &-- one that is delivered as specified by this router, and a clone that goes on
18787 to be routed further. For this reason, &%unseen%& may not be combined with the
18788 &%one_time%& option in a &(redirect)& router.
18789
18790 &*Warning*&: Header lines added to the address (or specified for removal) by
18791 this router or by previous routers affect the &"unseen"& copy of the message
18792 only. The clone that continues to be processed by further routers starts with
18793 no added headers and none specified for removal. For a &%redirect%& router, if
18794 a generated address is the same as the incoming address, this can lead to
18795 duplicate addresses with different header modifications. Exim does not do
18796 duplicate deliveries (except, in certain circumstances, to pipes -- see section
18797 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
18798 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
18799 &%redirect%& router may be of help.
18800
18801 Unlike the handling of header modifications, any data that was set by the
18802 &%address_data%& option in the current or previous routers &'is'& passed on to
18803 subsequent routers.
18804
18805
18806 .option user routers string&!! "see below"
18807 .cindex "uid (user id)" "local delivery"
18808 .cindex "local transports" "uid and gid"
18809 .cindex "transport" "local"
18810 .cindex "router" "user for filter processing"
18811 .cindex "filter" "user for processing"
18812 When a router queues an address for a transport, and the transport does not
18813 specify a user, the user given here is used when running the delivery process.
18814 The user may be specified numerically or by name. If expansion fails, the
18815 error is logged and delivery is deferred.
18816 This user is also used by the &(redirect)& router when running a filter file.
18817 The default is unset, except when &%check_local_user%& is set. In this case,
18818 the default is taken from the password information. If the user is specified as
18819 a name, and &%group%& is not set, the group associated with the user is used.
18820 See also &%initgroups%& and &%group%& and the discussion in chapter
18821 &<<CHAPenvironment>>&.
18822
18823
18824
18825 .option verify routers&!? boolean true
18826 Setting this option has the effect of setting &%verify_sender%& and
18827 &%verify_recipient%& to the same value.
18828
18829
18830 .option verify_only routers&!? boolean false
18831 .cindex "EXPN" "with &%verify_only%&"
18832 .oindex "&%-bv%&"
18833 .cindex "router" "used only when verifying"
18834 If this option is set, the router is used only when verifying an address,
18835 delivering in cutthrough mode or
18836 testing with the &%-bv%& option, not when actually doing a delivery, testing
18837 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
18838 restricted to verifying only senders or recipients by means of
18839 &%verify_sender%& and &%verify_recipient%&.
18840
18841 &*Warning*&: When the router is being run to verify addresses for an incoming
18842 SMTP message, Exim is not running as root, but under its own uid. If the router
18843 accesses any files, you need to make sure that they are accessible to the Exim
18844 user or group.
18845
18846
18847 .option verify_recipient routers&!? boolean true
18848 If this option is false, the router is skipped when verifying recipient
18849 addresses,
18850 delivering in cutthrough mode
18851 or testing recipient verification using &%-bv%&.
18852 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18853 are evaluated.
18854 See also the &$verify_mode$& variable.
18855
18856
18857 .option verify_sender routers&!? boolean true
18858 If this option is false, the router is skipped when verifying sender addresses
18859 or testing sender verification using &%-bvs%&.
18860 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18861 are evaluated.
18862 See also the &$verify_mode$& variable.
18863 .ecindex IIDgenoprou1
18864 .ecindex IIDgenoprou2
18865
18866
18867
18868
18869
18870
18871 . ////////////////////////////////////////////////////////////////////////////
18872 . ////////////////////////////////////////////////////////////////////////////
18873
18874 .chapter "The accept router" "CHID4"
18875 .cindex "&(accept)& router"
18876 .cindex "routers" "&(accept)&"
18877 The &(accept)& router has no private options of its own. Unless it is being
18878 used purely for verification (see &%verify_only%&) a transport is required to
18879 be defined by the generic &%transport%& option. If the preconditions that are
18880 specified by generic options are met, the router accepts the address and queues
18881 it for the given transport. The most common use of this router is for setting
18882 up deliveries to local mailboxes. For example:
18883 .code
18884 localusers:
18885 driver = accept
18886 domains = mydomain.example
18887 check_local_user
18888 transport = local_delivery
18889 .endd
18890 The &%domains%& condition in this example checks the domain of the address, and
18891 &%check_local_user%& checks that the local part is the login of a local user.
18892 When both preconditions are met, the &(accept)& router runs, and queues the
18893 address for the &(local_delivery)& transport.
18894
18895
18896
18897
18898
18899
18900 . ////////////////////////////////////////////////////////////////////////////
18901 . ////////////////////////////////////////////////////////////////////////////
18902
18903 .chapter "The dnslookup router" "CHAPdnslookup"
18904 .scindex IIDdnsrou1 "&(dnslookup)& router"
18905 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
18906 The &(dnslookup)& router looks up the hosts that handle mail for the
18907 recipient's domain in the DNS. A transport must always be set for this router,
18908 unless &%verify_only%& is set.
18909
18910 If SRV support is configured (see &%check_srv%& below), Exim first searches for
18911 SRV records. If none are found, or if SRV support is not configured,
18912 MX records are looked up. If no MX records exist, address records are sought.
18913 However, &%mx_domains%& can be set to disable the direct use of address
18914 records.
18915
18916 MX records of equal priority are sorted by Exim into a random order. Exim then
18917 looks for address records for the host names obtained from MX or SRV records.
18918 When a host has more than one IP address, they are sorted into a random order,
18919 except that IPv6 addresses are sorted before IPv4 addresses. If all the
18920 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
18921 generic option, the router declines.
18922
18923 Unless they have the highest priority (lowest MX value), MX records that point
18924 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
18925 are discarded, together with any other MX records of equal or lower priority.
18926
18927 .cindex "MX record" "pointing to local host"
18928 .cindex "local host" "MX pointing to"
18929 .oindex "&%self%&" "in &(dnslookup)& router"
18930 If the host pointed to by the highest priority MX record, or looked up as an
18931 address record, is the local host, or matches &%hosts_treat_as_local%&, what
18932 happens is controlled by the generic &%self%& option.
18933
18934
18935 .section "Problems with DNS lookups" "SECTprowitdnsloo"
18936 There have been problems with DNS servers when SRV records are looked up.
18937 Some misbehaving servers return a DNS error or timeout when a non-existent
18938 SRV record is sought. Similar problems have in the past been reported for
18939 MX records. The global &%dns_again_means_nonexist%& option can help with this
18940 problem, but it is heavy-handed because it is a global option.
18941
18942 For this reason, there are two options, &%srv_fail_domains%& and
18943 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
18944 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
18945 an attempt to look up an SRV or MX record causes one of these results, and the
18946 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
18947 such record"&. In the case of an SRV lookup, this means that the router
18948 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
18949 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
18950 case routing fails.
18951
18952
18953 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
18954 .cindex "&(dnslookup)& router" "declines"
18955 There are a few cases where a &(dnslookup)& router will decline to accept
18956 an address; if such a router is expected to handle "all remaining non-local
18957 domains", then it is important to set &%no_more%&.
18958
18959 The router will defer rather than decline if the domain
18960 is found in the &%fail_defer_domains%& router option.
18961
18962 Reasons for a &(dnslookup)& router to decline currently include:
18963 .ilist
18964 The domain does not exist in DNS
18965 .next
18966 The domain exists but the MX record's host part is just "."; this is a common
18967 convention (borrowed from SRV) used to indicate that there is no such service
18968 for this domain and to not fall back to trying A/AAAA records.
18969 .next
18970 Ditto, but for SRV records, when &%check_srv%& is set on this router.
18971 .next
18972 MX record points to a non-existent host.
18973 .next
18974 MX record points to an IP address and the main section option
18975 &%allow_mx_to_ip%& is not set.
18976 .next
18977 MX records exist and point to valid hosts, but all hosts resolve only to
18978 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
18979 .next
18980 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
18981 &%dns_check_names_pattern%& for handling one variant of this)
18982 .next
18983 &%check_secondary_mx%& is set on this router but the local host can
18984 not be found in the MX records (see below)
18985 .endlist
18986
18987
18988
18989
18990 .section "Private options for dnslookup" "SECID118"
18991 .cindex "options" "&(dnslookup)& router"
18992 The private options for the &(dnslookup)& router are as follows:
18993
18994 .option check_secondary_mx dnslookup boolean false
18995 .cindex "MX record" "checking for secondary"
18996 If this option is set, the router declines unless the local host is found in
18997 (and removed from) the list of hosts obtained by MX lookup. This can be used to
18998 process domains for which the local host is a secondary mail exchanger
18999 differently to other domains. The way in which Exim decides whether a host is
19000 the local host is described in section &<<SECTreclocipadd>>&.
19001
19002
19003 .option check_srv dnslookup string&!! unset
19004 .cindex "SRV record" "enabling use of"
19005 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
19006 addition to MX and address records. The support is disabled by default. To
19007 enable SRV support, set the &%check_srv%& option to the name of the service
19008 required. For example,
19009 .code
19010 check_srv = smtp
19011 .endd
19012 looks for SRV records that refer to the normal smtp service. The option is
19013 expanded, so the service name can vary from message to message or address
19014 to address. This might be helpful if SRV records are being used for a
19015 submission service. If the expansion is forced to fail, the &%check_srv%&
19016 option is ignored, and the router proceeds to look for MX records in the
19017 normal way.
19018
19019 When the expansion succeeds, the router searches first for SRV records for
19020 the given service (it assumes TCP protocol). A single SRV record with a
19021 host name that consists of just a single dot indicates &"no such service for
19022 this domain"&; if this is encountered, the router declines. If other kinds of
19023 SRV record are found, they are used to construct a host list for delivery
19024 according to the rules of RFC 2782. MX records are not sought in this case.
19025
19026 When no SRV records are found, MX records (and address records) are sought in
19027 the traditional way. In other words, SRV records take precedence over MX
19028 records, just as MX records take precedence over address records. Note that
19029 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
19030 defined it. It is apparently believed that MX records are sufficient for email
19031 and that SRV records should not be used for this purpose. However, SRV records
19032 have an additional &"weight"& feature which some people might find useful when
19033 trying to split an SMTP load between hosts of different power.
19034
19035 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
19036 when there is a DNS lookup error.
19037
19038
19039
19040
19041 .option fail_defer_domains dnslookup "domain list&!!" unset
19042 .cindex "MX record" "not found"
19043 DNS lookups for domains matching &%fail_defer_domains%&
19044 which find no matching record will cause the router to defer
19045 rather than the default behaviour of decline.
19046 This maybe be useful for queueing messages for a newly created
19047 domain while the DNS configuration is not ready.
19048 However, it will result in any message with mistyped domains
19049 also being queued.
19050
19051
19052 .option ipv4_only "string&!!" unset
19053 .cindex IPv6 disabling
19054 .cindex DNS "IPv6 disabling"
19055 The string is expanded, and if the result is anything but a forced failure,
19056 or an empty string, or one of the strings “0” or “no” or “false”
19057 (checked without regard to the case of the letters),
19058 only A records are used.
19059
19060 .option ipv4_prefer "string&!!" unset
19061 .cindex IPv4 preference
19062 .cindex DNS "IPv4 preference"
19063 The string is expanded, and if the result is anything but a forced failure,
19064 or an empty string, or one of the strings “0” or “no” or “false”
19065 (checked without regard to the case of the letters),
19066 A records are sorted before AAAA records (inverting the default).
19067
19068 .option mx_domains dnslookup "domain list&!!" unset
19069 .cindex "MX record" "required to exist"
19070 .cindex "SRV record" "required to exist"
19071 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
19072 record in order to be recognized. (The name of this option could be improved.)
19073 For example, if all the mail hosts in &'fict.example'& are known to have MX
19074 records, except for those in &'discworld.fict.example'&, you could use this
19075 setting:
19076 .code
19077 mx_domains = ! *.discworld.fict.example : *.fict.example
19078 .endd
19079 This specifies that messages addressed to a domain that matches the list but
19080 has no MX record should be bounced immediately instead of being routed using
19081 the address record.
19082
19083
19084 .option mx_fail_domains dnslookup "domain list&!!" unset
19085 If the DNS lookup for MX records for one of the domains in this list causes a
19086 DNS lookup error, Exim behaves as if no MX records were found. See section
19087 &<<SECTprowitdnsloo>>& for more discussion.
19088
19089
19090
19091
19092 .option qualify_single dnslookup boolean true
19093 .cindex "DNS" "resolver options"
19094 .cindex "DNS" "qualifying single-component names"
19095 When this option is true, the resolver option RES_DEFNAMES is set for DNS
19096 lookups. Typically, but not standardly, this causes the resolver to qualify
19097 single-component names with the default domain. For example, on a machine
19098 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
19099 &'thesaurus.ref.example'& inside the resolver. For details of what your
19100 resolver actually does, consult your man pages for &'resolver'& and
19101 &'resolv.conf'&.
19102
19103
19104
19105 .option rewrite_headers dnslookup boolean true
19106 .cindex "rewriting" "header lines"
19107 .cindex "header lines" "rewriting"
19108 If the domain name in the address that is being processed is not fully
19109 qualified, it may be expanded to its full form by a DNS lookup. For example, if
19110 an address is specified as &'dormouse@teaparty'&, the domain might be
19111 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
19112 occur as a result of setting the &%widen_domains%& option. If
19113 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
19114 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
19115 header lines of the message are rewritten with the full domain name.
19116
19117 This option should be turned off only when it is known that no message is
19118 ever going to be sent outside an environment where the abbreviation makes
19119 sense.
19120
19121 When an MX record is looked up in the DNS and matches a wildcard record, name
19122 servers normally return a record containing the name that has been looked up,
19123 making it impossible to detect whether a wildcard was present or not. However,
19124 some name servers have recently been seen to return the wildcard entry. If the
19125 name returned by a DNS lookup begins with an asterisk, it is not used for
19126 header rewriting.
19127
19128
19129 .option same_domain_copy_routing dnslookup boolean false
19130 .cindex "address" "copying routing"
19131 Addresses with the same domain are normally routed by the &(dnslookup)& router
19132 to the same list of hosts. However, this cannot be presumed, because the router
19133 options and preconditions may refer to the local part of the address. By
19134 default, therefore, Exim routes each address in a message independently. DNS
19135 servers run caches, so repeated DNS lookups are not normally expensive, and in
19136 any case, personal messages rarely have more than a few recipients.
19137
19138 If you are running mailing lists with large numbers of subscribers at the same
19139 domain, and you are using a &(dnslookup)& router which is independent of the
19140 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
19141 lookups for identical domains in one message. In this case, when &(dnslookup)&
19142 routes an address to a remote transport, any other unrouted addresses in the
19143 message that have the same domain are automatically given the same routing
19144 without processing them independently,
19145 provided the following conditions are met:
19146
19147 .ilist
19148 No router that processed the address specified &%headers_add%& or
19149 &%headers_remove%&.
19150 .next
19151 The router did not change the address in any way, for example, by &"widening"&
19152 the domain.
19153 .endlist
19154
19155
19156
19157
19158 .option search_parents dnslookup boolean false
19159 .cindex "DNS" "resolver options"
19160 When this option is true, the resolver option RES_DNSRCH is set for DNS
19161 lookups. This is different from the &%qualify_single%& option in that it
19162 applies to domains containing dots. Typically, but not standardly, it causes
19163 the resolver to search for the name in the current domain and in parent
19164 domains. For example, on a machine in the &'fict.example'& domain, if looking
19165 up &'teaparty.wonderland'& failed, the resolver would try
19166 &'teaparty.wonderland.fict.example'&. For details of what your resolver
19167 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
19168
19169 Setting this option true can cause problems in domains that have a wildcard MX
19170 record, because any domain that does not have its own MX record matches the
19171 local wildcard.
19172
19173
19174
19175 .option srv_fail_domains dnslookup "domain list&!!" unset
19176 If the DNS lookup for SRV records for one of the domains in this list causes a
19177 DNS lookup error, Exim behaves as if no SRV records were found. See section
19178 &<<SECTprowitdnsloo>>& for more discussion.
19179
19180
19181
19182
19183 .option widen_domains dnslookup "string list" unset
19184 .cindex "domain" "partial; widening"
19185 If a DNS lookup fails and this option is set, each of its strings in turn is
19186 added onto the end of the domain, and the lookup is tried again. For example,
19187 if
19188 .code
19189 widen_domains = fict.example:ref.example
19190 .endd
19191 is set and a lookup of &'klingon.dictionary'& fails,
19192 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
19193 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
19194 and &%search_parents%& options can cause some widening to be undertaken inside
19195 the DNS resolver. &%widen_domains%& is not applied to sender addresses
19196 when verifying, unless &%rewrite_headers%& is false (not the default).
19197
19198
19199 .section "Effect of qualify_single and search_parents" "SECID119"
19200 When a domain from an envelope recipient is changed by the resolver as a result
19201 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
19202 corresponding address in the message's header lines unless &%rewrite_headers%&
19203 is set false. Exim then re-routes the address, using the full domain.
19204
19205 These two options affect only the DNS lookup that takes place inside the router
19206 for the domain of the address that is being routed. They do not affect lookups
19207 such as that implied by
19208 .code
19209 domains = @mx_any
19210 .endd
19211 that may happen while processing a router precondition before the router is
19212 entered. No widening ever takes place for these lookups.
19213 .ecindex IIDdnsrou1
19214 .ecindex IIDdnsrou2
19215
19216
19217
19218
19219
19220
19221
19222
19223
19224 . ////////////////////////////////////////////////////////////////////////////
19225 . ////////////////////////////////////////////////////////////////////////////
19226
19227 .chapter "The ipliteral router" "CHID5"
19228 .cindex "&(ipliteral)& router"
19229 .cindex "domain literal" "routing"
19230 .cindex "routers" "&(ipliteral)&"
19231 This router has no private options. Unless it is being used purely for
19232 verification (see &%verify_only%&) a transport is required to be defined by the
19233 generic &%transport%& option. The router accepts the address if its domain part
19234 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
19235 router handles the address
19236 .code
19237 root@[192.168.1.1]
19238 .endd
19239 by setting up delivery to the host with that IP address. IPv4 domain literals
19240 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
19241 are similar, but the address is preceded by &`ipv6:`&. For example:
19242 .code
19243 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
19244 .endd
19245 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
19246 grounds that sooner or later somebody will try it.
19247
19248 .oindex "&%self%&" "in &(ipliteral)& router"
19249 If the IP address matches something in &%ignore_target_hosts%&, the router
19250 declines. If an IP literal turns out to refer to the local host, the generic
19251 &%self%& option determines what happens.
19252
19253 The RFCs require support for domain literals; however, their use is
19254 controversial in today's Internet. If you want to use this router, you must
19255 also set the main configuration option &%allow_domain_literals%&. Otherwise,
19256 Exim will not recognize the domain literal syntax in addresses.
19257
19258
19259
19260 . ////////////////////////////////////////////////////////////////////////////
19261 . ////////////////////////////////////////////////////////////////////////////
19262
19263 .chapter "The iplookup router" "CHID6"
19264 .cindex "&(iplookup)& router"
19265 .cindex "routers" "&(iplookup)&"
19266 The &(iplookup)& router was written to fulfil a specific requirement in
19267 Cambridge University (which in fact no longer exists). For this reason, it is
19268 not included in the binary of Exim by default. If you want to include it, you
19269 must set
19270 .code
19271 ROUTER_IPLOOKUP=yes
19272 .endd
19273 in your &_Local/Makefile_& configuration file.
19274
19275 The &(iplookup)& router routes an address by sending it over a TCP or UDP
19276 connection to one or more specific hosts. The host can then return the same or
19277 a different address &-- in effect rewriting the recipient address in the
19278 message's envelope. The new address is then passed on to subsequent routers. If
19279 this process fails, the address can be passed on to other routers, or delivery
19280 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
19281 must not be specified for it.
19282
19283 .cindex "options" "&(iplookup)& router"
19284 .option hosts iplookup string unset
19285 This option must be supplied. Its value is a colon-separated list of host
19286 names. The hosts are looked up using &[gethostbyname()]&
19287 (or &[getipnodebyname()]& when available)
19288 and are tried in order until one responds to the query. If none respond, what
19289 happens is controlled by &%optional%&.
19290
19291
19292 .option optional iplookup boolean false
19293 If &%optional%& is true, if no response is obtained from any host, the address
19294 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
19295 delivery to the address is deferred.
19296
19297
19298 .option port iplookup integer 0
19299 .cindex "port" "&(iplookup)& router"
19300 This option must be supplied. It specifies the port number for the TCP or UDP
19301 call.
19302
19303
19304 .option protocol iplookup string udp
19305 This option can be set to &"udp"& or &"tcp"& to specify which of the two
19306 protocols is to be used.
19307
19308
19309 .option query iplookup string&!! "see below"
19310 This defines the content of the query that is sent to the remote hosts. The
19311 default value is:
19312 .code
19313 $local_part@$domain $local_part@$domain
19314 .endd
19315 The repetition serves as a way of checking that a response is to the correct
19316 query in the default case (see &%response_pattern%& below).
19317
19318
19319 .option reroute iplookup string&!! unset
19320 If this option is not set, the rerouted address is precisely the byte string
19321 returned by the remote host, up to the first white space, if any. If set, the
19322 string is expanded to form the rerouted address. It can include parts matched
19323 in the response by &%response_pattern%& by means of numeric variables such as
19324 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
19325 whether or not a pattern is in use. In all cases, the rerouted address must end
19326 up in the form &'local_part@domain'&.
19327
19328
19329 .option response_pattern iplookup string unset
19330 This option can be set to a regular expression that is applied to the string
19331 returned from the remote host. If the pattern does not match the response, the
19332 router declines. If &%response_pattern%& is not set, no checking of the
19333 response is done, unless the query was defaulted, in which case there is a
19334 check that the text returned after the first white space is the original
19335 address. This checks that the answer that has been received is in response to
19336 the correct question. For example, if the response is just a new domain, the
19337 following could be used:
19338 .code
19339 response_pattern = ^([^@]+)$
19340 reroute = $local_part@$1
19341 .endd
19342
19343 .option timeout iplookup time 5s
19344 This specifies the amount of time to wait for a response from the remote
19345 machine. The same timeout is used for the &[connect()]& function for a TCP
19346 call. It does not apply to UDP.
19347
19348
19349
19350
19351 . ////////////////////////////////////////////////////////////////////////////
19352 . ////////////////////////////////////////////////////////////////////////////
19353
19354 .chapter "The manualroute router" "CHID7"
19355 .scindex IIDmanrou1 "&(manualroute)& router"
19356 .scindex IIDmanrou2 "routers" "&(manualroute)&"
19357 .cindex "domain" "manually routing"
19358 The &(manualroute)& router is so-called because it provides a way of manually
19359 routing an address according to its domain. It is mainly used when you want to
19360 route addresses to remote hosts according to your own rules, bypassing the
19361 normal DNS routing that looks up MX records. However, &(manualroute)& can also
19362 route to local transports, a facility that may be useful if you want to save
19363 messages for dial-in hosts in local files.
19364
19365 The &(manualroute)& router compares a list of domain patterns with the domain
19366 it is trying to route. If there is no match, the router declines. Each pattern
19367 has associated with it a list of hosts and some other optional data, which may
19368 include a transport. The combination of a pattern and its data is called a
19369 &"routing rule"&. For patterns that do not have an associated transport, the
19370 generic &%transport%& option must specify a transport, unless the router is
19371 being used purely for verification (see &%verify_only%&).
19372
19373 .vindex "&$host$&"
19374 In the case of verification, matching the domain pattern is sufficient for the
19375 router to accept the address. When actually routing an address for delivery,
19376 an address that matches a domain pattern is queued for the associated
19377 transport. If the transport is not a local one, a host list must be associated
19378 with the pattern; IP addresses are looked up for the hosts, and these are
19379 passed to the transport along with the mail address. For local transports, a
19380 host list is optional. If it is present, it is passed in &$host$& as a single
19381 text string.
19382
19383 The list of routing rules can be provided as an inline string in
19384 &%route_list%&, or the data can be obtained by looking up the domain in a file
19385 or database by setting &%route_data%&. Only one of these settings may appear in
19386 any one instance of &(manualroute)&. The format of routing rules is described
19387 below, following the list of private options.
19388
19389
19390 .section "Private options for manualroute" "SECTprioptman"
19391
19392 .cindex "options" "&(manualroute)& router"
19393 The private options for the &(manualroute)& router are as follows:
19394
19395 .option host_all_ignored manualroute string defer
19396 See &%host_find_failed%&.
19397
19398 .option host_find_failed manualroute string freeze
19399 This option controls what happens when &(manualroute)& tries to find an IP
19400 address for a host, and the host does not exist. The option can be set to one
19401 of the following values:
19402 .code
19403 decline
19404 defer
19405 fail
19406 freeze
19407 ignore
19408 pass
19409 .endd
19410 The default (&"freeze"&) assumes that this state is a serious configuration
19411 error. The difference between &"pass"& and &"decline"& is that the former
19412 forces the address to be passed to the next router (or the router defined by
19413 &%pass_router%&),
19414 .oindex "&%more%&"
19415 overriding &%no_more%&, whereas the latter passes the address to the next
19416 router only if &%more%& is true.
19417
19418 The value &"ignore"& causes Exim to completely ignore a host whose IP address
19419 cannot be found. If all the hosts in the list are ignored, the behaviour is
19420 controlled by the &%host_all_ignored%& option. This takes the same values
19421 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
19422
19423 The &%host_find_failed%& option applies only to a definite &"does not exist"&
19424 state; if a host lookup gets a temporary error, delivery is deferred unless the
19425 generic &%pass_on_timeout%& option is set.
19426
19427
19428 .option hosts_randomize manualroute boolean false
19429 .cindex "randomized host list"
19430 .cindex "host" "list of; randomized"
19431 If this option is set, the order of the items in a host list in a routing rule
19432 is randomized each time the list is used, unless an option in the routing rule
19433 overrides (see below). Randomizing the order of a host list can be used to do
19434 crude load sharing. However, if more than one mail address is routed by the
19435 same router to the same host list, the host lists are considered to be the same
19436 (even though they may be randomized into different orders) for the purpose of
19437 deciding whether to batch the deliveries into a single SMTP transaction.
19438
19439 When &%hosts_randomize%& is true, a host list may be split
19440 into groups whose order is separately randomized. This makes it possible to
19441 set up MX-like behaviour. The boundaries between groups are indicated by an
19442 item that is just &`+`& in the host list. For example:
19443 .code
19444 route_list = * host1:host2:host3:+:host4:host5
19445 .endd
19446 The order of the first three hosts and the order of the last two hosts is
19447 randomized for each use, but the first three always end up before the last two.
19448 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
19449 randomized host list is passed to an &(smtp)& transport that also has
19450 &%hosts_randomize set%&, the list is not re-randomized.
19451
19452
19453 .option route_data manualroute string&!! unset
19454 If this option is set, it must expand to yield the data part of a routing rule.
19455 Typically, the expansion string includes a lookup based on the domain. For
19456 example:
19457 .code
19458 route_data = ${lookup{$domain}dbm{/etc/routes}}
19459 .endd
19460 If the expansion is forced to fail, or the result is an empty string, the
19461 router declines. Other kinds of expansion failure cause delivery to be
19462 deferred.
19463
19464
19465 .option route_list manualroute "string list" unset
19466 This string is a list of routing rules, in the form defined below. Note that,
19467 unlike most string lists, the items are separated by semicolons. This is so
19468 that they may contain colon-separated host lists.
19469
19470
19471 .option same_domain_copy_routing manualroute boolean false
19472 .cindex "address" "copying routing"
19473 Addresses with the same domain are normally routed by the &(manualroute)&
19474 router to the same list of hosts. However, this cannot be presumed, because the
19475 router options and preconditions may refer to the local part of the address. By
19476 default, therefore, Exim routes each address in a message independently. DNS
19477 servers run caches, so repeated DNS lookups are not normally expensive, and in
19478 any case, personal messages rarely have more than a few recipients.
19479
19480 If you are running mailing lists with large numbers of subscribers at the same
19481 domain, and you are using a &(manualroute)& router which is independent of the
19482 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
19483 lookups for identical domains in one message. In this case, when
19484 &(manualroute)& routes an address to a remote transport, any other unrouted
19485 addresses in the message that have the same domain are automatically given the
19486 same routing without processing them independently. However, this is only done
19487 if &%headers_add%& and &%headers_remove%& are unset.
19488
19489
19490
19491
19492 .section "Routing rules in route_list" "SECID120"
19493 The value of &%route_list%& is a string consisting of a sequence of routing
19494 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
19495 entered as two semicolons. Alternatively, the list separator can be changed as
19496 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
19497 Empty rules are ignored. The format of each rule is
19498 .display
19499 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
19500 .endd
19501 The following example contains two rules, each with a simple domain pattern and
19502 no options:
19503 .code
19504 route_list = \
19505 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
19506 thes.ref.example mail-3.ref.example:mail-4.ref.example
19507 .endd
19508 The three parts of a rule are separated by white space. The pattern and the
19509 list of hosts can be enclosed in quotes if necessary, and if they are, the
19510 usual quoting rules apply. Each rule in a &%route_list%& must start with a
19511 single domain pattern, which is the only mandatory item in the rule. The
19512 pattern is in the same format as one item in a domain list (see section
19513 &<<SECTdomainlist>>&),
19514 except that it may not be the name of an interpolated file.
19515 That is, it may be wildcarded, or a regular expression, or a file or database
19516 lookup (with semicolons doubled, because of the use of semicolon as a separator
19517 in a &%route_list%&).
19518
19519 The rules in &%route_list%& are searched in order until one of the patterns
19520 matches the domain that is being routed. The list of hosts and then options are
19521 then used as described below. If there is no match, the router declines. When
19522 &%route_list%& is set, &%route_data%& must not be set.
19523
19524
19525
19526 .section "Routing rules in route_data" "SECID121"
19527 The use of &%route_list%& is convenient when there are only a small number of
19528 routing rules. For larger numbers, it is easier to use a file or database to
19529 hold the routing information, and use the &%route_data%& option instead.
19530 The value of &%route_data%& is a list of hosts, followed by (optional) options.
19531 Most commonly, &%route_data%& is set as a string that contains an
19532 expansion lookup. For example, suppose we place two routing rules in a file
19533 like this:
19534 .code
19535 dict.ref.example: mail-1.ref.example:mail-2.ref.example
19536 thes.ref.example: mail-3.ref.example:mail-4.ref.example
19537 .endd
19538 This data can be accessed by setting
19539 .code
19540 route_data = ${lookup{$domain}lsearch{/the/file/name}}
19541 .endd
19542 Failure of the lookup results in an empty string, causing the router to
19543 decline. However, you do not have to use a lookup in &%route_data%&. The only
19544 requirement is that the result of expanding the string is a list of hosts,
19545 possibly followed by options, separated by white space. The list of hosts must
19546 be enclosed in quotes if it contains white space.
19547
19548
19549
19550
19551 .section "Format of the list of hosts" "SECID122"
19552 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
19553 always separately expanded before use. If the expansion fails, the router
19554 declines. The result of the expansion must be a colon-separated list of names
19555 and/or IP addresses, optionally also including ports. The format of each item
19556 in the list is described in the next section. The list separator can be changed
19557 as described in section &<<SECTlistconstruct>>&.
19558
19559 If the list of hosts was obtained from a &%route_list%& item, the following
19560 variables are set during its expansion:
19561
19562 .ilist
19563 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
19564 If the domain was matched against a regular expression, the numeric variables
19565 &$1$&, &$2$&, etc. may be set. For example:
19566 .code
19567 route_list = ^domain(\d+) host-$1.text.example
19568 .endd
19569 .next
19570 &$0$& is always set to the entire domain.
19571 .next
19572 &$1$& is also set when partial matching is done in a file lookup.
19573
19574 .next
19575 .vindex "&$value$&"
19576 If the pattern that matched the domain was a lookup item, the data that was
19577 looked up is available in the expansion variable &$value$&. For example:
19578 .code
19579 route_list = lsearch;;/some/file.routes $value
19580 .endd
19581 .endlist
19582
19583 Note the doubling of the semicolon in the pattern that is necessary because
19584 semicolon is the default route list separator.
19585
19586
19587
19588 .section "Format of one host item" "SECTformatonehostitem"
19589 Each item in the list of hosts is either a host name or an IP address,
19590 optionally with an attached port number. When no port is given, an IP address
19591 is not enclosed in brackets. When a port is specified, it overrides the port
19592 specification on the transport. The port is separated from the name or address
19593 by a colon. This leads to some complications:
19594
19595 .ilist
19596 Because colon is the default separator for the list of hosts, either
19597 the colon that specifies a port must be doubled, or the list separator must
19598 be changed. The following two examples have the same effect:
19599 .code
19600 route_list = * "host1.tld::1225 : host2.tld::1226"
19601 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
19602 .endd
19603 .next
19604 When IPv6 addresses are involved, it gets worse, because they contain
19605 colons of their own. To make this case easier, it is permitted to
19606 enclose an IP address (either v4 or v6) in square brackets if a port
19607 number follows. For example:
19608 .code
19609 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
19610 .endd
19611 .endlist
19612
19613 .section "How the list of hosts is used" "SECThostshowused"
19614 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
19615 the hosts is tried, in the order specified, when carrying out the SMTP
19616 delivery. However, the order can be changed by setting the &%hosts_randomize%&
19617 option, either on the router (see section &<<SECTprioptman>>& above), or on the
19618 transport.
19619
19620 Hosts may be listed by name or by IP address. An unadorned name in the list of
19621 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
19622 interpreted as an indirection to a sublist of hosts obtained by looking up MX
19623 records in the DNS. For example:
19624 .code
19625 route_list = * x.y.z:p.q.r/MX:e.f.g
19626 .endd
19627 If this feature is used with a port specifier, the port must come last. For
19628 example:
19629 .code
19630 route_list = * dom1.tld/mx::1225
19631 .endd
19632 If the &%hosts_randomize%& option is set, the order of the items in the list is
19633 randomized before any lookups are done. Exim then scans the list; for any name
19634 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
19635 be an interface on the local host and the item is not the first in the list,
19636 Exim discards it and any subsequent items. If it is the first item, what
19637 happens is controlled by the
19638 .oindex "&%self%&" "in &(manualroute)& router"
19639 &%self%& option of the router.
19640
19641 A name on the list that is followed by &`/MX`& is replaced with the list of
19642 hosts obtained by looking up MX records for the name. This is always a DNS
19643 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
19644 below) are not relevant here. The order of these hosts is determined by the
19645 preference values in the MX records, according to the usual rules. Because
19646 randomizing happens before the MX lookup, it does not affect the order that is
19647 defined by MX preferences.
19648
19649 If the local host is present in the sublist obtained from MX records, but is
19650 not the most preferred host in that list, it and any equally or less
19651 preferred hosts are removed before the sublist is inserted into the main list.
19652
19653 If the local host is the most preferred host in the MX list, what happens
19654 depends on where in the original list of hosts the &`/MX`& item appears. If it
19655 is not the first item (that is, there are previous hosts in the main list),
19656 Exim discards this name and any subsequent items in the main list.
19657
19658 If the MX item is first in the list of hosts, and the local host is the
19659 most preferred host, what happens is controlled by the &%self%& option of the
19660 router.
19661
19662 DNS failures when lookup up the MX records are treated in the same way as DNS
19663 failures when looking up IP addresses: &%pass_on_timeout%& and
19664 &%host_find_failed%& are used when relevant.
19665
19666 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
19667 whether obtained from an MX lookup or not.
19668
19669
19670
19671 .section "How the options are used" "SECThowoptused"
19672 The options are a sequence of words, space-separated.
19673 One of the words can be the name of a transport; this overrides the
19674 &%transport%& option on the router for this particular routing rule only. The
19675 other words (if present) control randomization of the list of hosts on a
19676 per-rule basis, and how the IP addresses of the hosts are to be found when
19677 routing to a remote transport. These options are as follows:
19678
19679 .ilist
19680 &%randomize%&: randomize the order of the hosts in this list, overriding the
19681 setting of &%hosts_randomize%& for this routing rule only.
19682 .next
19683 &%no_randomize%&: do not randomize the order of the hosts in this list,
19684 overriding the setting of &%hosts_randomize%& for this routing rule only.
19685 .next
19686 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
19687 find IP addresses. This function may ultimately cause a DNS lookup, but it may
19688 also look in &_/etc/hosts_& or other sources of information.
19689 .next
19690 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
19691 no address records are found. If there is a temporary DNS error (such as a
19692 timeout), delivery is deferred.
19693 .next
19694 &%ipv4_only%&: in direct DNS lookups, look up only A records.
19695 .next
19696 &%ipv4_prefer%&: in direct DNS lookups, sort A records before AAAA records.
19697 .endlist
19698
19699 For example:
19700 .code
19701 route_list = domain1 host1:host2:host3 randomize bydns;\
19702 domain2 host4:host5
19703 .endd
19704 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
19705 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
19706 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
19707 or &[gethostbyname()]&, and the result of the lookup is the result of that
19708 call.
19709
19710 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
19711 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
19712 instead of TRY_AGAIN. That is why the default action is to try a DNS
19713 lookup first. Only if that gives a definite &"no such host"& is the local
19714 function called.
19715
19716 &*Compatibility*&: From Exim 4.85 until fixed for 4.90, there was an
19717 inadvertent constraint that a transport name as an option had to be the last
19718 option specified.
19719
19720
19721
19722 If no IP address for a host can be found, what happens is controlled by the
19723 &%host_find_failed%& option.
19724
19725 .vindex "&$host$&"
19726 When an address is routed to a local transport, IP addresses are not looked up.
19727 The host list is passed to the transport in the &$host$& variable.
19728
19729
19730
19731 .section "Manualroute examples" "SECID123"
19732 In some of the examples that follow, the presence of the &%remote_smtp%&
19733 transport, as defined in the default configuration file, is assumed:
19734
19735 .ilist
19736 .cindex "smart host" "example router"
19737 The &(manualroute)& router can be used to forward all external mail to a
19738 &'smart host'&. If you have set up, in the main part of the configuration, a
19739 named domain list that contains your local domains, for example:
19740 .code
19741 domainlist local_domains = my.domain.example
19742 .endd
19743 You can arrange for all other domains to be routed to a smart host by making
19744 your first router something like this:
19745 .code
19746 smart_route:
19747 driver = manualroute
19748 domains = !+local_domains
19749 transport = remote_smtp
19750 route_list = * smarthost.ref.example
19751 .endd
19752 This causes all non-local addresses to be sent to the single host
19753 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
19754 they are tried in order
19755 (but you can use &%hosts_randomize%& to vary the order each time).
19756 Another way of configuring the same thing is this:
19757 .code
19758 smart_route:
19759 driver = manualroute
19760 transport = remote_smtp
19761 route_list = !+local_domains smarthost.ref.example
19762 .endd
19763 There is no difference in behaviour between these two routers as they stand.
19764 However, they behave differently if &%no_more%& is added to them. In the first
19765 example, the router is skipped if the domain does not match the &%domains%&
19766 precondition; the following router is always tried. If the router runs, it
19767 always matches the domain and so can never decline. Therefore, &%no_more%&
19768 would have no effect. In the second case, the router is never skipped; it
19769 always runs. However, if it doesn't match the domain, it declines. In this case
19770 &%no_more%& would prevent subsequent routers from running.
19771
19772 .next
19773 .cindex "mail hub example"
19774 A &'mail hub'& is a host which receives mail for a number of domains via MX
19775 records in the DNS and delivers it via its own private routing mechanism. Often
19776 the final destinations are behind a firewall, with the mail hub being the one
19777 machine that can connect to machines both inside and outside the firewall. The
19778 &(manualroute)& router is usually used on a mail hub to route incoming messages
19779 to the correct hosts. For a small number of domains, the routing can be inline,
19780 using the &%route_list%& option, but for a larger number a file or database
19781 lookup is easier to manage.
19782
19783 If the domain names are in fact the names of the machines to which the mail is
19784 to be sent by the mail hub, the configuration can be quite simple. For
19785 example:
19786 .code
19787 hub_route:
19788 driver = manualroute
19789 transport = remote_smtp
19790 route_list = *.rhodes.tvs.example $domain
19791 .endd
19792 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
19793 whose names are the same as the mail domains. A similar approach can be taken
19794 if the host name can be obtained from the domain name by a string manipulation
19795 that the expansion facilities can handle. Otherwise, a lookup based on the
19796 domain can be used to find the host:
19797 .code
19798 through_firewall:
19799 driver = manualroute
19800 transport = remote_smtp
19801 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
19802 .endd
19803 The result of the lookup must be the name or IP address of the host (or
19804 hosts) to which the address is to be routed. If the lookup fails, the route
19805 data is empty, causing the router to decline. The address then passes to the
19806 next router.
19807
19808 .next
19809 .cindex "batched SMTP output example"
19810 .cindex "SMTP" "batched outgoing; example"
19811 You can use &(manualroute)& to deliver messages to pipes or files in batched
19812 SMTP format for onward transportation by some other means. This is one way of
19813 storing mail for a dial-up host when it is not connected. The route list entry
19814 can be as simple as a single domain name in a configuration like this:
19815 .code
19816 save_in_file:
19817 driver = manualroute
19818 transport = batchsmtp_appendfile
19819 route_list = saved.domain.example
19820 .endd
19821 though often a pattern is used to pick up more than one domain. If there are
19822 several domains or groups of domains with different transport requirements,
19823 different transports can be listed in the routing information:
19824 .code
19825 save_in_file:
19826 driver = manualroute
19827 route_list = \
19828 *.saved.domain1.example $domain batch_appendfile; \
19829 *.saved.domain2.example \
19830 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
19831 batch_pipe
19832 .endd
19833 .vindex "&$domain$&"
19834 .vindex "&$host$&"
19835 The first of these just passes the domain in the &$host$& variable, which
19836 doesn't achieve much (since it is also in &$domain$&), but the second does a
19837 file lookup to find a value to pass, causing the router to decline to handle
19838 the address if the lookup fails.
19839
19840 .next
19841 .cindex "UUCP" "example of router for"
19842 Routing mail directly to UUCP software is a specific case of the use of
19843 &(manualroute)& in a gateway to another mail environment. This is an example of
19844 one way it can be done:
19845 .code
19846 # Transport
19847 uucp:
19848 driver = pipe
19849 user = nobody
19850 command = /usr/local/bin/uux -r - \
19851 ${substr_-5:$host}!rmail ${local_part}
19852 return_fail_output = true
19853
19854 # Router
19855 uucphost:
19856 transport = uucp
19857 driver = manualroute
19858 route_data = \
19859 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
19860 .endd
19861 The file &_/usr/local/exim/uucphosts_& contains entries like
19862 .code
19863 darksite.ethereal.example: darksite.UUCP
19864 .endd
19865 It can be set up more simply without adding and removing &".UUCP"& but this way
19866 makes clear the distinction between the domain name
19867 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
19868 .endlist
19869 .ecindex IIDmanrou1
19870 .ecindex IIDmanrou2
19871
19872
19873
19874
19875
19876
19877
19878
19879 . ////////////////////////////////////////////////////////////////////////////
19880 . ////////////////////////////////////////////////////////////////////////////
19881
19882 .chapter "The queryprogram router" "CHAPdriverlast"
19883 .scindex IIDquerou1 "&(queryprogram)& router"
19884 .scindex IIDquerou2 "routers" "&(queryprogram)&"
19885 .cindex "routing" "by external program"
19886 The &(queryprogram)& router routes an address by running an external command
19887 and acting on its output. This is an expensive way to route, and is intended
19888 mainly for use in lightly-loaded systems, or for performing experiments.
19889 However, if it is possible to use the precondition options (&%domains%&,
19890 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
19891 be used in special cases, even on a busy host. There are the following private
19892 options:
19893 .cindex "options" "&(queryprogram)& router"
19894
19895 .option command queryprogram string&!! unset
19896 This option must be set. It specifies the command that is to be run. The
19897 command is split up into a command name and arguments, and then each is
19898 expanded separately (exactly as for a &(pipe)& transport, described in chapter
19899 &<<CHAPpipetransport>>&).
19900
19901
19902 .option command_group queryprogram string unset
19903 .cindex "gid (group id)" "in &(queryprogram)& router"
19904 This option specifies a gid to be set when running the command while routing an
19905 address for deliver. It must be set if &%command_user%& specifies a numerical
19906 uid. If it begins with a digit, it is interpreted as the numerical value of the
19907 gid. Otherwise it is looked up using &[getgrnam()]&.
19908
19909
19910 .option command_user queryprogram string unset
19911 .cindex "uid (user id)" "for &(queryprogram)&"
19912 This option must be set. It specifies the uid which is set when running the
19913 command while routing an address for delivery. If the value begins with a digit,
19914 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
19915 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
19916 not set, a value for the gid also.
19917
19918 &*Warning:*& Changing uid and gid is possible only when Exim is running as
19919 root, which it does during a normal delivery in a conventional configuration.
19920 However, when an address is being verified during message reception, Exim is
19921 usually running as the Exim user, not as root. If the &(queryprogram)& router
19922 is called from a non-root process, Exim cannot change uid or gid before running
19923 the command. In this circumstance the command runs under the current uid and
19924 gid.
19925
19926
19927 .option current_directory queryprogram string /
19928 This option specifies an absolute path which is made the current directory
19929 before running the command.
19930
19931
19932 .option timeout queryprogram time 1h
19933 If the command does not complete within the timeout period, its process group
19934 is killed and the message is frozen. A value of zero time specifies no
19935 timeout.
19936
19937
19938 The standard output of the command is connected to a pipe, which is read when
19939 the command terminates. It should consist of a single line of output,
19940 containing up to five fields, separated by white space. The maximum length of
19941 the line is 1023 characters. Longer lines are silently truncated. The first
19942 field is one of the following words (case-insensitive):
19943
19944 .ilist
19945 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
19946 below).
19947 .next
19948 &'Decline'&: the router declines; pass the address to the next router, unless
19949 &%no_more%& is set.
19950 .next
19951 &'Fail'&: routing failed; do not pass the address to any more routers. Any
19952 subsequent text on the line is an error message. If the router is run as part
19953 of address verification during an incoming SMTP message, the message is
19954 included in the SMTP response.
19955 .next
19956 &'Defer'&: routing could not be completed at this time; try again later. Any
19957 subsequent text on the line is an error message which is logged. It is not
19958 included in any SMTP response.
19959 .next
19960 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
19961 .next
19962 &'Pass'&: pass the address to the next router (or the router specified by
19963 &%pass_router%&), overriding &%no_more%&.
19964 .next
19965 &'Redirect'&: the message is redirected. The remainder of the line is a list of
19966 new addresses, which are routed independently, starting with the first router,
19967 or the router specified by &%redirect_router%&, if set.
19968 .endlist
19969
19970 When the first word is &'accept'&, the remainder of the line consists of a
19971 number of keyed data values, as follows (split into two lines here, to fit on
19972 the page):
19973 .code
19974 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
19975 LOOKUP=byname|bydns DATA=<text>
19976 .endd
19977 The data items can be given in any order, and all are optional. If no transport
19978 is included, the transport specified by the generic &%transport%& option is
19979 used. The list of hosts and the lookup type are needed only if the transport is
19980 an &(smtp)& transport that does not itself supply a list of hosts.
19981
19982 The format of the list of hosts is the same as for the &(manualroute)& router.
19983 As well as host names and IP addresses with optional port numbers, as described
19984 in section &<<SECTformatonehostitem>>&, it may contain names followed by
19985 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
19986 (see section &<<SECThostshowused>>&).
19987
19988 If the lookup type is not specified, Exim behaves as follows when trying to
19989 find an IP address for each host: First, a DNS lookup is done. If this yields
19990 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
19991 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
19992 result of the lookup is the result of that call.
19993
19994 .vindex "&$address_data$&"
19995 If the DATA field is set, its value is placed in the &$address_data$&
19996 variable. For example, this return line
19997 .code
19998 accept hosts=x1.y.example:x2.y.example data="rule1"
19999 .endd
20000 routes the address to the default transport, passing a list of two hosts. When
20001 the transport runs, the string &"rule1"& is in &$address_data$&.
20002 .ecindex IIDquerou1
20003 .ecindex IIDquerou2
20004
20005
20006
20007
20008 . ////////////////////////////////////////////////////////////////////////////
20009 . ////////////////////////////////////////////////////////////////////////////
20010
20011 .chapter "The redirect router" "CHAPredirect"
20012 .scindex IIDredrou1 "&(redirect)& router"
20013 .scindex IIDredrou2 "routers" "&(redirect)&"
20014 .cindex "alias file" "in a &(redirect)& router"
20015 .cindex "address redirection" "&(redirect)& router"
20016 The &(redirect)& router handles several kinds of address redirection. Its most
20017 common uses are for resolving local part aliases from a central alias file
20018 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
20019 files, but it has many other potential uses. The incoming address can be
20020 redirected in several different ways:
20021
20022 .ilist
20023 It can be replaced by one or more new addresses which are themselves routed
20024 independently.
20025 .next
20026 It can be routed to be delivered to a given file or directory.
20027 .next
20028 It can be routed to be delivered to a specified pipe command.
20029 .next
20030 It can cause an automatic reply to be generated.
20031 .next
20032 It can be forced to fail, optionally with a custom error message.
20033 .next
20034 It can be temporarily deferred, optionally with a custom message.
20035 .next
20036 It can be discarded.
20037 .endlist
20038
20039 The generic &%transport%& option must not be set for &(redirect)& routers.
20040 However, there are some private options which define transports for delivery to
20041 files and pipes, and for generating autoreplies. See the &%file_transport%&,
20042 &%pipe_transport%& and &%reply_transport%& descriptions below.
20043
20044 If success DSNs have been requested
20045 .cindex "DSN" "success"
20046 .cindex "Delivery Status Notification" "success"
20047 redirection triggers one and the DSN options are not passed any further.
20048
20049
20050
20051 .section "Redirection data" "SECID124"
20052 The router operates by interpreting a text string which it obtains either by
20053 expanding the contents of the &%data%& option, or by reading the entire
20054 contents of a file whose name is given in the &%file%& option. These two
20055 options are mutually exclusive. The first is commonly used for handling system
20056 aliases, in a configuration like this:
20057 .code
20058 system_aliases:
20059 driver = redirect
20060 data = ${lookup{$local_part}lsearch{/etc/aliases}}
20061 .endd
20062 If the lookup fails, the expanded string in this example is empty. When the
20063 expansion of &%data%& results in an empty string, the router declines. A forced
20064 expansion failure also causes the router to decline; other expansion failures
20065 cause delivery to be deferred.
20066
20067 A configuration using &%file%& is commonly used for handling users'
20068 &_.forward_& files, like this:
20069 .code
20070 userforward:
20071 driver = redirect
20072 check_local_user
20073 file = $home/.forward
20074 no_verify
20075 .endd
20076 If the file does not exist, or causes no action to be taken (for example, it is
20077 empty or consists only of comments), the router declines. &*Warning*&: This
20078 is not the case when the file contains syntactically valid items that happen to
20079 yield empty addresses, for example, items containing only RFC 2822 address
20080 comments.
20081
20082
20083
20084 .section "Forward files and address verification" "SECID125"
20085 .cindex "address redirection" "while verifying"
20086 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
20087 &_.forward_& files, as in the example above. There are two reasons for this:
20088
20089 .ilist
20090 When Exim is receiving an incoming SMTP message from a remote host, it is
20091 running under the Exim uid, not as root. Exim is unable to change uid to read
20092 the file as the user, and it may not be able to read it as the Exim user. So in
20093 practice the router may not be able to operate.
20094 .next
20095 However, even when the router can operate, the existence of a &_.forward_& file
20096 is unimportant when verifying an address. What should be checked is whether the
20097 local part is a valid user name or not. Cutting out the redirection processing
20098 saves some resources.
20099 .endlist
20100
20101
20102
20103
20104
20105
20106 .section "Interpreting redirection data" "SECID126"
20107 .cindex "Sieve filter" "specifying in redirection data"
20108 .cindex "filter" "specifying in redirection data"
20109 The contents of the data string, whether obtained from &%data%& or &%file%&,
20110 can be interpreted in two different ways:
20111
20112 .ilist
20113 If the &%allow_filter%& option is set true, and the data begins with the text
20114 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
20115 &'filtering'& instructions in the form of an Exim or Sieve filter file,
20116 respectively. Details of the syntax and semantics of filter files are described
20117 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
20118 document is intended for use by end users.
20119 .next
20120 Otherwise, the data must be a comma-separated list of redirection items, as
20121 described in the next section.
20122 .endlist
20123
20124 When a message is redirected to a file (a &"mail folder"&), the file name given
20125 in a non-filter redirection list must always be an absolute path. A filter may
20126 generate a relative path &-- how this is handled depends on the transport's
20127 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
20128 for the &(appendfile)& transport.
20129
20130
20131
20132 .section "Items in a non-filter redirection list" "SECTitenonfilred"
20133 .cindex "address redirection" "non-filter list items"
20134 When the redirection data is not an Exim or Sieve filter, for example, if it
20135 comes from a conventional alias or forward file, it consists of a list of
20136 addresses, file names, pipe commands, or certain special items (see section
20137 &<<SECTspecitredli>>& below). The special items can be individually enabled or
20138 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
20139 depending on their default values. The items in the list are separated by
20140 commas or newlines.
20141 If a comma is required in an item, the entire item must be enclosed in double
20142 quotes.
20143
20144 Lines starting with a # character are comments, and are ignored, and # may
20145 also appear following a comma, in which case everything between the # and the
20146 next newline character is ignored.
20147
20148 If an item is entirely enclosed in double quotes, these are removed. Otherwise
20149 double quotes are retained because some forms of mail address require their use
20150 (but never to enclose the entire address). In the following description,
20151 &"item"& refers to what remains after any surrounding double quotes have been
20152 removed.
20153
20154 .vindex "&$local_part$&"
20155 &*Warning*&: If you use an Exim expansion to construct a redirection address,
20156 and the expansion contains a reference to &$local_part$&, you should make use
20157 of the &%quote_local_part%& expansion operator, in case the local part contains
20158 special characters. For example, to redirect all mail for the domain
20159 &'obsolete.example'&, retaining the existing local part, you could use this
20160 setting:
20161 .code
20162 data = ${quote_local_part:$local_part}@newdomain.example
20163 .endd
20164
20165
20166 .section "Redirecting to a local mailbox" "SECTredlocmai"
20167 .cindex "routing" "loops in"
20168 .cindex "loop" "while routing, avoidance of"
20169 .cindex "address redirection" "to local mailbox"
20170 A redirection item may safely be the same as the address currently under
20171 consideration. This does not cause a routing loop, because a router is
20172 automatically skipped if any ancestor of the address that is being processed
20173 is the same as the current address and was processed by the current router.
20174 Such an address is therefore passed to the following routers, so it is handled
20175 as if there were no redirection. When making this loop-avoidance test, the
20176 complete local part, including any prefix or suffix, is used.
20177
20178 .cindex "address redirection" "local part without domain"
20179 Specifying the same local part without a domain is a common usage in personal
20180 filter files when the user wants to have messages delivered to the local
20181 mailbox and also forwarded elsewhere. For example, the user whose login is
20182 &'cleo'& might have a &_.forward_& file containing this:
20183 .code
20184 cleo, cleopatra@egypt.example
20185 .endd
20186 .cindex "backslash in alias file"
20187 .cindex "alias file" "backslash in"
20188 For compatibility with other MTAs, such unqualified local parts may be
20189 preceded by &"\"&, but this is not a requirement for loop prevention. However,
20190 it does make a difference if more than one domain is being handled
20191 synonymously.
20192
20193 If an item begins with &"\"& and the rest of the item parses as a valid RFC
20194 2822 address that does not include a domain, the item is qualified using the
20195 domain of the incoming address. In the absence of a leading &"\"&, unqualified
20196 addresses are qualified using the value in &%qualify_recipient%&, but you can
20197 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
20198
20199 Care must be taken if there are alias names for local users.
20200 Consider an MTA handling a single local domain where the system alias file
20201 contains:
20202 .code
20203 Sam.Reman: spqr
20204 .endd
20205 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
20206 messages in the local mailbox, and also forward copies elsewhere. He creates
20207 this forward file:
20208 .code
20209 Sam.Reman, spqr@reme.elsewhere.example
20210 .endd
20211 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
20212 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
20213 second time round, because it has previously routed it,
20214 and the following routers presumably cannot handle the alias. The forward file
20215 should really contain
20216 .code
20217 spqr, spqr@reme.elsewhere.example
20218 .endd
20219 but because this is such a common error, the &%check_ancestor%& option (see
20220 below) exists to provide a way to get round it. This is normally set on a
20221 &(redirect)& router that is handling users' &_.forward_& files.
20222
20223
20224
20225 .section "Special items in redirection lists" "SECTspecitredli"
20226 In addition to addresses, the following types of item may appear in redirection
20227 lists (that is, in non-filter redirection data):
20228
20229 .ilist
20230 .cindex "pipe" "in redirection list"
20231 .cindex "address redirection" "to pipe"
20232 An item is treated as a pipe command if it begins with &"|"& and does not parse
20233 as a valid RFC 2822 address that includes a domain. A transport for running the
20234 command must be specified by the &%pipe_transport%& option.
20235 Normally, either the router or the transport specifies a user and a group under
20236 which to run the delivery. The default is to use the Exim user and group.
20237
20238 Single or double quotes can be used for enclosing the individual arguments of
20239 the pipe command; no interpretation of escapes is done for single quotes. If
20240 the command contains a comma character, it is necessary to put the whole item
20241 in double quotes, for example:
20242 .code
20243 "|/some/command ready,steady,go"
20244 .endd
20245 since items in redirection lists are terminated by commas. Do not, however,
20246 quote just the command. An item such as
20247 .code
20248 |"/some/command ready,steady,go"
20249 .endd
20250 is interpreted as a pipe with a rather strange command name, and no arguments.
20251
20252 Note that the above example assumes that the text comes from a lookup source
20253 of some sort, so that the quotes are part of the data. If composing a
20254 redirect router with a &%data%& option directly specifying this command, the
20255 quotes will be used by the configuration parser to define the extent of one
20256 string, but will not be passed down into the redirect router itself. There
20257 are two main approaches to get around this: escape quotes to be part of the
20258 data itself, or avoid using this mechanism and instead create a custom
20259 transport with the &%command%& option set and reference that transport from
20260 an &%accept%& router.
20261
20262 .next
20263 .cindex "file" "in redirection list"
20264 .cindex "address redirection" "to file"
20265 An item is interpreted as a path name if it begins with &"/"& and does not
20266 parse as a valid RFC 2822 address that includes a domain. For example,
20267 .code
20268 /home/world/minbari
20269 .endd
20270 is treated as a file name, but
20271 .code
20272 /s=molari/o=babylon/@x400gate.way
20273 .endd
20274 is treated as an address. For a file name, a transport must be specified using
20275 the &%file_transport%& option. However, if the generated path name ends with a
20276 forward slash character, it is interpreted as a directory name rather than a
20277 file name, and &%directory_transport%& is used instead.
20278
20279 Normally, either the router or the transport specifies a user and a group under
20280 which to run the delivery. The default is to use the Exim user and group.
20281
20282 .cindex "&_/dev/null_&"
20283 However, if a redirection item is the path &_/dev/null_&, delivery to it is
20284 bypassed at a high level, and the log entry shows &"**bypassed**"&
20285 instead of a transport name. In this case the user and group are not used.
20286
20287 .next
20288 .cindex "included address list"
20289 .cindex "address redirection" "included external list"
20290 If an item is of the form
20291 .code
20292 :include:<path name>
20293 .endd
20294 a list of further items is taken from the given file and included at that
20295 point. &*Note*&: Such a file can not be a filter file; it is just an
20296 out-of-line addition to the list. The items in the included list are separated
20297 by commas or newlines and are not subject to expansion. If this is the first
20298 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
20299 the alias name. This example is incorrect:
20300 .code
20301 list1 :include:/opt/lists/list1
20302 .endd
20303 It must be given as
20304 .code
20305 list1: :include:/opt/lists/list1
20306 .endd
20307 .next
20308 .cindex "address redirection" "to black hole"
20309 .cindex "delivery" "discard"
20310 .cindex "delivery" "blackhole"
20311 .cindex "black hole"
20312 .cindex "abandoning mail"
20313 Sometimes you want to throw away mail to a particular local part. Making the
20314 &%data%& option expand to an empty string does not work, because that causes
20315 the router to decline. Instead, the alias item
20316 .code
20317 :blackhole:
20318 .endd
20319 can be used. It does what its name implies. No delivery is
20320 done, and no error message is generated. This has the same effect as specifying
20321 &_/dev/null_& as a destination, but it can be independently disabled.
20322
20323 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
20324 delivery is done for the original local part, even if other redirection items
20325 are present. If you are generating a multi-item list (for example, by reading a
20326 database) and need the ability to provide a no-op item, you must use
20327 &_/dev/null_&.
20328
20329 .next
20330 .cindex "delivery" "forcing failure"
20331 .cindex "delivery" "forcing deferral"
20332 .cindex "failing delivery" "forcing"
20333 .cindex "deferred delivery, forcing"
20334 .cindex "customizing" "failure message"
20335 An attempt to deliver a particular address can be deferred or forced to fail by
20336 redirection items of the form
20337 .code
20338 :defer:
20339 :fail:
20340 .endd
20341 respectively. When a redirection list contains such an item, it applies
20342 to the entire redirection; any other items in the list are ignored. Any
20343 text following &':fail:'& or &':defer:'& is placed in the error text
20344 associated with the failure. For example, an alias file might contain:
20345 .code
20346 X.Employee: :fail: Gone away, no forwarding address
20347 .endd
20348 In the case of an address that is being verified from an ACL or as the subject
20349 of a
20350 .cindex "VRFY" "error text, display of"
20351 VRFY command, the text is included in the SMTP error response by
20352 default.
20353 .cindex "EXPN" "error text, display of"
20354 The text is not included in the response to an EXPN command. In non-SMTP cases
20355 the text is included in the error message that Exim generates.
20356
20357 .cindex "SMTP" "error codes"
20358 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
20359 &':fail:'&. However, if the message starts with three digits followed by a
20360 space, optionally followed by an extended code of the form &'n.n.n'&, also
20361 followed by a space, and the very first digit is the same as the default error
20362 code, the code from the message is used instead. If the very first digit is
20363 incorrect, a panic error is logged, and the default code is used. You can
20364 suppress the use of the supplied code in a redirect router by setting the
20365 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
20366 ignored.
20367
20368 .vindex "&$acl_verify_message$&"
20369 In an ACL, an explicitly provided message overrides the default, but the
20370 default message is available in the variable &$acl_verify_message$& and can
20371 therefore be included in a custom message if this is desired.
20372
20373 Normally the error text is the rest of the redirection list &-- a comma does
20374 not terminate it &-- but a newline does act as a terminator. Newlines are not
20375 normally present in alias expansions. In &(lsearch)& lookups they are removed
20376 as part of the continuation process, but they may exist in other kinds of
20377 lookup and in &':include:'& files.
20378
20379 During routing for message delivery (as opposed to verification), a redirection
20380 containing &':fail:'& causes an immediate failure of the incoming address,
20381 whereas &':defer:'& causes the message to remain on the queue so that a
20382 subsequent delivery attempt can happen at a later time. If an address is
20383 deferred for too long, it will ultimately fail, because the normal retry
20384 rules still apply.
20385
20386 .next
20387 .cindex "alias file" "exception to default"
20388 Sometimes it is useful to use a single-key search type with a default (see
20389 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
20390 for exceptions to the default. These can be handled by aliasing them to
20391 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
20392 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
20393 results in an empty redirection list has the same effect.
20394 .endlist
20395
20396
20397 .section "Duplicate addresses" "SECTdupaddr"
20398 .cindex "duplicate addresses"
20399 .cindex "address duplicate, discarding"
20400 .cindex "pipe" "duplicated"
20401 Exim removes duplicate addresses from the list to which it is delivering, so as
20402 to deliver just one copy to each address. This does not apply to deliveries
20403 routed to pipes by different immediate parent addresses, but an indirect
20404 aliasing scheme of the type
20405 .code
20406 pipe: |/some/command $local_part
20407 localpart1: pipe
20408 localpart2: pipe
20409 .endd
20410 does not work with a message that is addressed to both local parts, because
20411 when the second is aliased to the intermediate local part &"pipe"& it gets
20412 discarded as being the same as a previously handled address. However, a scheme
20413 such as
20414 .code
20415 localpart1: |/some/command $local_part
20416 localpart2: |/some/command $local_part
20417 .endd
20418 does result in two different pipe deliveries, because the immediate parents of
20419 the pipes are distinct.
20420
20421
20422
20423 .section "Repeated redirection expansion" "SECID128"
20424 .cindex "repeated redirection expansion"
20425 .cindex "address redirection" "repeated for each delivery attempt"
20426 When a message cannot be delivered to all of its recipients immediately,
20427 leading to two or more delivery attempts, redirection expansion is carried out
20428 afresh each time for those addresses whose children were not all previously
20429 delivered. If redirection is being used as a mailing list, this can lead to new
20430 members of the list receiving copies of old messages. The &%one_time%& option
20431 can be used to avoid this.
20432
20433
20434 .section "Errors in redirection lists" "SECID129"
20435 .cindex "address redirection" "errors"
20436 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
20437 error is skipped, and an entry is written to the main log. This may be useful
20438 for mailing lists that are automatically managed. Otherwise, if an error is
20439 detected while generating the list of new addresses, the original address is
20440 deferred. See also &%syntax_errors_to%&.
20441
20442
20443
20444 .section "Private options for the redirect router" "SECID130"
20445
20446 .cindex "options" "&(redirect)& router"
20447 The private options for the &(redirect)& router are as follows:
20448
20449
20450 .option allow_defer redirect boolean false
20451 Setting this option allows the use of &':defer:'& in non-filter redirection
20452 data, or the &%defer%& command in an Exim filter file.
20453
20454
20455 .option allow_fail redirect boolean false
20456 .cindex "failing delivery" "from filter"
20457 If this option is true, the &':fail:'& item can be used in a redirection list,
20458 and the &%fail%& command may be used in an Exim filter file.
20459
20460
20461 .option allow_filter redirect boolean false
20462 .cindex "filter" "enabling use of"
20463 .cindex "Sieve filter" "enabling use of"
20464 Setting this option allows Exim to interpret redirection data that starts with
20465 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
20466 are some features of Exim filter files that some administrators may wish to
20467 lock out; see the &%forbid_filter_%&&'xxx'& options below.
20468
20469 It is also possible to lock out Exim filters or Sieve filters while allowing
20470 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
20471
20472
20473 The filter is run using the uid and gid set by the generic &%user%& and
20474 &%group%& options. These take their defaults from the password data if
20475 &%check_local_user%& is set, so in the normal case of users' personal filter
20476 files, the filter is run as the relevant user. When &%allow_filter%& is set
20477 true, Exim insists that either &%check_local_user%& or &%user%& is set.
20478
20479
20480
20481 .option allow_freeze redirect boolean false
20482 .cindex "freezing messages" "allowing in filter"
20483 Setting this option allows the use of the &%freeze%& command in an Exim filter.
20484 This command is more normally encountered in system filters, and is disabled by
20485 default for redirection filters because it isn't something you usually want to
20486 let ordinary users do.
20487
20488
20489
20490 .option check_ancestor redirect boolean false
20491 This option is concerned with handling generated addresses that are the same
20492 as some address in the list of redirection ancestors of the current address.
20493 Although it is turned off by default in the code, it is set in the default
20494 configuration file for handling users' &_.forward_& files. It is recommended
20495 for this use of the &(redirect)& router.
20496
20497 When &%check_ancestor%& is set, if a generated address (including the domain)
20498 is the same as any ancestor of the current address, it is replaced by a copy of
20499 the current address. This helps in the case where local part A is aliased to B,
20500 and B has a &_.forward_& file pointing back to A. For example, within a single
20501 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
20502 &_&~jb/.forward_& contains:
20503 .code
20504 \Joe.Bloggs, <other item(s)>
20505 .endd
20506 Without the &%check_ancestor%& setting, either local part (&"jb"& or
20507 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
20508 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
20509 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
20510 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
20511 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
20512 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
20513 original address. See also the &%repeat_use%& option below.
20514
20515
20516 .option check_group redirect boolean "see below"
20517 When the &%file%& option is used, the group owner of the file is checked only
20518 when this option is set. The permitted groups are those listed in the
20519 &%owngroups%& option, together with the user's default group if
20520 &%check_local_user%& is set. If the file has the wrong group, routing is
20521 deferred. The default setting for this option is true if &%check_local_user%&
20522 is set and the &%modemask%& option permits the group write bit, or if the
20523 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
20524
20525
20526
20527 .option check_owner redirect boolean "see below"
20528 When the &%file%& option is used, the owner of the file is checked only when
20529 this option is set. If &%check_local_user%& is set, the local user is
20530 permitted; otherwise the owner must be one of those listed in the &%owners%&
20531 option. The default value for this option is true if &%check_local_user%& or
20532 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
20533
20534
20535 .option data redirect string&!! unset
20536 This option is mutually exclusive with &%file%&. One or other of them must be
20537 set, but not both. The contents of &%data%& are expanded, and then used as the
20538 list of forwarding items, or as a set of filtering instructions. If the
20539 expansion is forced to fail, or the result is an empty string or a string that
20540 has no effect (consists entirely of comments), the router declines.
20541
20542 When filtering instructions are used, the string must begin with &"#Exim
20543 filter"&, and all comments in the string, including this initial one, must be
20544 terminated with newline characters. For example:
20545 .code
20546 data = #Exim filter\n\
20547 if $h_to: contains Exim then save $home/mail/exim endif
20548 .endd
20549 If you are reading the data from a database where newlines cannot be included,
20550 you can use the &${sg}$& expansion item to turn the escape string of your
20551 choice into a newline.
20552
20553
20554 .option directory_transport redirect string&!! unset
20555 A &(redirect)& router sets up a direct delivery to a directory when a path name
20556 ending with a slash is specified as a new &"address"&. The transport used is
20557 specified by this option, which, after expansion, must be the name of a
20558 configured transport. This should normally be an &(appendfile)& transport.
20559
20560
20561 .option file redirect string&!! unset
20562 This option specifies the name of a file that contains the redirection data. It
20563 is mutually exclusive with the &%data%& option. The string is expanded before
20564 use; if the expansion is forced to fail, the router declines. Other expansion
20565 failures cause delivery to be deferred. The result of a successful expansion
20566 must be an absolute path. The entire file is read and used as the redirection
20567 data. If the data is an empty string or a string that has no effect (consists
20568 entirely of comments), the router declines.
20569
20570 .cindex "NFS" "checking for file existence"
20571 If the attempt to open the file fails with a &"does not exist"& error, Exim
20572 runs a check on the containing directory,
20573 unless &%ignore_enotdir%& is true (see below).
20574 If the directory does not appear to exist, delivery is deferred. This can
20575 happen when users' &_.forward_& files are in NFS-mounted directories, and there
20576 is a mount problem. If the containing directory does exist, but the file does
20577 not, the router declines.
20578
20579
20580 .option file_transport redirect string&!! unset
20581 .vindex "&$address_file$&"
20582 A &(redirect)& router sets up a direct delivery to a file when a path name not
20583 ending in a slash is specified as a new &"address"&. The transport used is
20584 specified by this option, which, after expansion, must be the name of a
20585 configured transport. This should normally be an &(appendfile)& transport. When
20586 it is running, the file name is in &$address_file$&.
20587
20588
20589 .option filter_prepend_home redirect boolean true
20590 When this option is true, if a &(save)& command in an Exim filter specifies a
20591 relative path, and &$home$& is defined, it is automatically prepended to the
20592 relative path. If this option is set false, this action does not happen. The
20593 relative path is then passed to the transport unmodified.
20594
20595
20596 .option forbid_blackhole redirect boolean false
20597 .cindex "restricting access to features"
20598 .cindex "filter" "locking out certain features"
20599 If this option is true, the &':blackhole:'& item may not appear in a
20600 redirection list.
20601
20602
20603 .option forbid_exim_filter redirect boolean false
20604 .cindex "restricting access to features"
20605 .cindex "filter" "locking out certain features"
20606 If this option is set true, only Sieve filters are permitted when
20607 &%allow_filter%& is true.
20608
20609
20610
20611
20612 .option forbid_file redirect boolean false
20613 .cindex "restricting access to features"
20614 .cindex "delivery" "to file; forbidding"
20615 .cindex "filter" "locking out certain features"
20616 .cindex "Sieve filter" "forbidding delivery to a file"
20617 .cindex "Sieve filter" "&""keep""& facility; disabling"
20618 If this option is true, this router may not generate a new address that
20619 specifies delivery to a local file or directory, either from a filter or from a
20620 conventional forward file. This option is forced to be true if &%one_time%& is
20621 set. It applies to Sieve filters as well as to Exim filters, but if true, it
20622 locks out the Sieve's &"keep"& facility.
20623
20624
20625 .option forbid_filter_dlfunc redirect boolean false
20626 .cindex "restricting access to features"
20627 .cindex "filter" "locking out certain features"
20628 If this option is true, string expansions in Exim filters are not allowed to
20629 make use of the &%dlfunc%& expansion facility to run dynamically loaded
20630 functions.
20631
20632 .option forbid_filter_existstest redirect boolean false
20633 .cindex "restricting access to features"
20634 .cindex "filter" "locking out certain features"
20635 .cindex "expansion" "statting a file"
20636 If this option is true, string expansions in Exim filters are not allowed to
20637 make use of the &%exists%& condition or the &%stat%& expansion item.
20638
20639 .option forbid_filter_logwrite redirect boolean false
20640 .cindex "restricting access to features"
20641 .cindex "filter" "locking out certain features"
20642 If this option is true, use of the logging facility in Exim filters is not
20643 permitted. Logging is in any case available only if the filter is being run
20644 under some unprivileged uid (which is normally the case for ordinary users'
20645 &_.forward_& files).
20646
20647
20648 .option forbid_filter_lookup redirect boolean false
20649 .cindex "restricting access to features"
20650 .cindex "filter" "locking out certain features"
20651 If this option is true, string expansions in Exim filter files are not allowed
20652 to make use of &%lookup%& items.
20653
20654
20655 .option forbid_filter_perl redirect boolean false
20656 .cindex "restricting access to features"
20657 .cindex "filter" "locking out certain features"
20658 This option has an effect only if Exim is built with embedded Perl support. If
20659 it is true, string expansions in Exim filter files are not allowed to make use
20660 of the embedded Perl support.
20661
20662
20663 .option forbid_filter_readfile redirect boolean false
20664 .cindex "restricting access to features"
20665 .cindex "filter" "locking out certain features"
20666 If this option is true, string expansions in Exim filter files are not allowed
20667 to make use of &%readfile%& items.
20668
20669
20670 .option forbid_filter_readsocket redirect boolean false
20671 .cindex "restricting access to features"
20672 .cindex "filter" "locking out certain features"
20673 If this option is true, string expansions in Exim filter files are not allowed
20674 to make use of &%readsocket%& items.
20675
20676
20677 .option forbid_filter_reply redirect boolean false
20678 .cindex "restricting access to features"
20679 .cindex "filter" "locking out certain features"
20680 If this option is true, this router may not generate an automatic reply
20681 message. Automatic replies can be generated only from Exim or Sieve filter
20682 files, not from traditional forward files. This option is forced to be true if
20683 &%one_time%& is set.
20684
20685
20686 .option forbid_filter_run redirect boolean false
20687 .cindex "restricting access to features"
20688 .cindex "filter" "locking out certain features"
20689 If this option is true, string expansions in Exim filter files are not allowed
20690 to make use of &%run%& items.
20691
20692
20693 .option forbid_include redirect boolean false
20694 .cindex "restricting access to features"
20695 .cindex "filter" "locking out certain features"
20696 If this option is true, items of the form
20697 .code
20698 :include:<path name>
20699 .endd
20700 are not permitted in non-filter redirection lists.
20701
20702
20703 .option forbid_pipe redirect boolean false
20704 .cindex "restricting access to features"
20705 .cindex "filter" "locking out certain features"
20706 .cindex "delivery" "to pipe; forbidding"
20707 If this option is true, this router may not generate a new address which
20708 specifies delivery to a pipe, either from an Exim filter or from a conventional
20709 forward file. This option is forced to be true if &%one_time%& is set.
20710
20711
20712 .option forbid_sieve_filter redirect boolean false
20713 .cindex "restricting access to features"
20714 .cindex "filter" "locking out certain features"
20715 If this option is set true, only Exim filters are permitted when
20716 &%allow_filter%& is true.
20717
20718
20719 .cindex "SMTP" "error codes"
20720 .option forbid_smtp_code redirect boolean false
20721 If this option is set true, any SMTP error codes that are present at the start
20722 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
20723 the default codes (451 and 550, respectively) are always used.
20724
20725
20726
20727
20728 .option hide_child_in_errmsg redirect boolean false
20729 .cindex "bounce message" "redirection details; suppressing"
20730 If this option is true, it prevents Exim from quoting a child address if it
20731 generates a bounce or delay message for it. Instead it says &"an address
20732 generated from <&'the top level address'&>"&. Of course, this applies only to
20733 bounces generated locally. If a message is forwarded to another host, &'its'&
20734 bounce may well quote the generated address.
20735
20736
20737 .option ignore_eacces redirect boolean false
20738 .cindex "EACCES"
20739 If this option is set and an attempt to open a redirection file yields the
20740 EACCES error (permission denied), the &(redirect)& router behaves as if the
20741 file did not exist.
20742
20743
20744 .option ignore_enotdir redirect boolean false
20745 .cindex "ENOTDIR"
20746 If this option is set and an attempt to open a redirection file yields the
20747 ENOTDIR error (something on the path is not a directory), the &(redirect)&
20748 router behaves as if the file did not exist.
20749
20750 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
20751 router that has the &%file%& option set discovers that the file does not exist
20752 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
20753 against unmounted NFS directories. If the parent can not be statted, delivery
20754 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
20755 is set, because that option tells Exim to ignore &"something on the path is not
20756 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
20757 that some operating systems give ENOENT where others give ENOTDIR.
20758
20759
20760
20761 .option include_directory redirect string unset
20762 If this option is set, the path names of any &':include:'& items in a
20763 redirection list must start with this directory.
20764
20765
20766 .option modemask redirect "octal integer" 022
20767 This specifies mode bits which must not be set for a file specified by the
20768 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
20769
20770
20771 .option one_time redirect boolean false
20772 .cindex "one-time aliasing/forwarding expansion"
20773 .cindex "alias file" "one-time expansion"
20774 .cindex "forward file" "one-time expansion"
20775 .cindex "mailing lists" "one-time expansion"
20776 .cindex "address redirection" "one-time expansion"
20777 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
20778 files each time it tries to deliver a message causes a problem when one or more
20779 of the generated addresses fails be delivered at the first attempt. The problem
20780 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
20781 but of what happens when the redirection list changes during the time that the
20782 message is on Exim's queue. This is particularly true in the case of mailing
20783 lists, where new subscribers might receive copies of messages that were posted
20784 before they subscribed.
20785
20786 If &%one_time%& is set and any addresses generated by the router fail to
20787 deliver at the first attempt, the failing addresses are added to the message as
20788 &"top level"& addresses, and the parent address that generated them is marked
20789 &"delivered"&. Thus, redirection does not happen again at the next delivery
20790 attempt.
20791
20792 &*Warning 1*&: Any header line addition or removal that is specified by this
20793 router would be lost if delivery did not succeed at the first attempt. For this
20794 reason, the &%headers_add%& and &%headers_remove%& generic options are not
20795 permitted when &%one_time%& is set.
20796
20797 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
20798 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
20799 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
20800
20801 &*Warning 3*&: The &%unseen%& generic router option may not be set with
20802 &%one_time%&.
20803
20804 The original top-level address is remembered with each of the generated
20805 addresses, and is output in any log messages. However, any intermediate parent
20806 addresses are not recorded. This makes a difference to the log only if
20807 &%all_parents%& log selector is set. It is expected that &%one_time%& will
20808 typically be used for mailing lists, where there is normally just one level of
20809 expansion.
20810
20811
20812 .option owners redirect "string list" unset
20813 .cindex "ownership" "alias file"
20814 .cindex "ownership" "forward file"
20815 .cindex "alias file" "ownership"
20816 .cindex "forward file" "ownership"
20817 This specifies a list of permitted owners for the file specified by &%file%&.
20818 This list is in addition to the local user when &%check_local_user%& is set.
20819 See &%check_owner%& above.
20820
20821
20822 .option owngroups redirect "string list" unset
20823 This specifies a list of permitted groups for the file specified by &%file%&.
20824 The list is in addition to the local user's primary group when
20825 &%check_local_user%& is set. See &%check_group%& above.
20826
20827
20828 .option pipe_transport redirect string&!! unset
20829 .vindex "&$address_pipe$&"
20830 A &(redirect)& router sets up a direct delivery to a pipe when a string
20831 starting with a vertical bar character is specified as a new &"address"&. The
20832 transport used is specified by this option, which, after expansion, must be the
20833 name of a configured transport. This should normally be a &(pipe)& transport.
20834 When the transport is run, the pipe command is in &$address_pipe$&.
20835
20836
20837 .option qualify_domain redirect string&!! unset
20838 .vindex "&$qualify_recipient$&"
20839 If this option is set, and an unqualified address (one without a domain) is
20840 generated, and that address would normally be qualified by the global setting
20841 in &%qualify_recipient%&, it is instead qualified with the domain specified by
20842 expanding this string. If the expansion fails, the router declines. If you want
20843 to revert to the default, you can have the expansion generate
20844 &$qualify_recipient$&.
20845
20846 This option applies to all unqualified addresses generated by Exim filters,
20847 but for traditional &_.forward_& files, it applies only to addresses that are
20848 not preceded by a backslash. Sieve filters cannot generate unqualified
20849 addresses.
20850
20851 .option qualify_preserve_domain redirect boolean false
20852 .cindex "domain" "in redirection; preserving"
20853 .cindex "preserving domain in redirection"
20854 .cindex "address redirection" "domain; preserving"
20855 If this option is set, the router's local &%qualify_domain%& option must not be
20856 set (a configuration error occurs if it is). If an unqualified address (one
20857 without a domain) is generated, it is qualified with the domain of the parent
20858 address (the immediately preceding ancestor) instead of the global
20859 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
20860 this applies whether or not the address is preceded by a backslash.
20861
20862
20863 .option repeat_use redirect boolean true
20864 If this option is set false, the router is skipped for a child address that has
20865 any ancestor that was routed by this router. This test happens before any of
20866 the other preconditions are tested. Exim's default anti-looping rules skip
20867 only when the ancestor is the same as the current address. See also
20868 &%check_ancestor%& above and the generic &%redirect_router%& option.
20869
20870
20871 .option reply_transport redirect string&!! unset
20872 A &(redirect)& router sets up an automatic reply when a &%mail%& or
20873 &%vacation%& command is used in a filter file. The transport used is specified
20874 by this option, which, after expansion, must be the name of a configured
20875 transport. This should normally be an &(autoreply)& transport. Other transports
20876 are unlikely to do anything sensible or useful.
20877
20878
20879 .option rewrite redirect boolean true
20880 .cindex "address redirection" "disabling rewriting"
20881 If this option is set false, addresses generated by the router are not
20882 subject to address rewriting. Otherwise, they are treated like new addresses
20883 and are rewritten according to the global rewriting rules.
20884
20885
20886 .option sieve_subaddress redirect string&!! unset
20887 The value of this option is passed to a Sieve filter to specify the
20888 :subaddress part of an address.
20889
20890 .option sieve_useraddress redirect string&!! unset
20891 The value of this option is passed to a Sieve filter to specify the :user part
20892 of an address. However, if it is unset, the entire original local part
20893 (including any prefix or suffix) is used for :user.
20894
20895
20896 .option sieve_vacation_directory redirect string&!! unset
20897 .cindex "Sieve filter" "vacation directory"
20898 To enable the &"vacation"& extension for Sieve filters, you must set
20899 &%sieve_vacation_directory%& to the directory where vacation databases are held
20900 (do not put anything else in that directory), and ensure that the
20901 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
20902 needs their own directory; Exim will create it if necessary.
20903
20904
20905
20906 .option skip_syntax_errors redirect boolean false
20907 .cindex "forward file" "broken"
20908 .cindex "address redirection" "broken files"
20909 .cindex "alias file" "broken"
20910 .cindex "broken alias or forward files"
20911 .cindex "ignoring faulty addresses"
20912 .cindex "skipping faulty addresses"
20913 .cindex "error" "skipping bad syntax"
20914 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
20915 non-filter redirection data are skipped, and each failing address is logged. If
20916 &%syntax_errors_to%& is set, a message is sent to the address it defines,
20917 giving details of the failures. If &%syntax_errors_text%& is set, its contents
20918 are expanded and placed at the head of the error message generated by
20919 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
20920 be the same address as the generic &%errors_to%& option. The
20921 &%skip_syntax_errors%& option is often used when handling mailing lists.
20922
20923 If all the addresses in a redirection list are skipped because of syntax
20924 errors, the router declines to handle the original address, and it is passed to
20925 the following routers.
20926
20927 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
20928 error in the filter causes filtering to be abandoned without any action being
20929 taken. The incident is logged, and the router declines to handle the address,
20930 so it is passed to the following routers.
20931
20932 .cindex "Sieve filter" "syntax errors in"
20933 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
20934 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
20935 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
20936
20937 &%skip_syntax_errors%& can be used to specify that errors in users' forward
20938 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
20939 option, used with an address that does not get redirected, can be used to
20940 notify users of these errors, by means of a router like this:
20941 .code
20942 userforward:
20943 driver = redirect
20944 allow_filter
20945 check_local_user
20946 file = $home/.forward
20947 file_transport = address_file
20948 pipe_transport = address_pipe
20949 reply_transport = address_reply
20950 no_verify
20951 skip_syntax_errors
20952 syntax_errors_to = real-$local_part@$domain
20953 syntax_errors_text = \
20954 This is an automatically generated message. An error has\n\
20955 been found in your .forward file. Details of the error are\n\
20956 reported below. While this error persists, you will receive\n\
20957 a copy of this message for every message that is addressed\n\
20958 to you. If your .forward file is a filter file, or if it is\n\
20959 a non-filter file containing no valid forwarding addresses,\n\
20960 a copy of each incoming message will be put in your normal\n\
20961 mailbox. If a non-filter file contains at least one valid\n\
20962 forwarding address, forwarding to the valid addresses will\n\
20963 happen, and those will be the only deliveries that occur.
20964 .endd
20965 You also need a router to ensure that local addresses that are prefixed by
20966 &`real-`& are recognized, but not forwarded or filtered. For example, you could
20967 put this immediately before the &(userforward)& router:
20968 .code
20969 real_localuser:
20970 driver = accept
20971 check_local_user
20972 local_part_prefix = real-
20973 transport = local_delivery
20974 .endd
20975 For security, it would probably be a good idea to restrict the use of this
20976 router to locally-generated messages, using a condition such as this:
20977 .code
20978 condition = ${if match {$sender_host_address}\
20979 {\N^(|127\.0\.0\.1)$\N}}
20980 .endd
20981
20982
20983 .option syntax_errors_text redirect string&!! unset
20984 See &%skip_syntax_errors%& above.
20985
20986
20987 .option syntax_errors_to redirect string unset
20988 See &%skip_syntax_errors%& above.
20989 .ecindex IIDredrou1
20990 .ecindex IIDredrou2
20991
20992
20993
20994
20995
20996
20997 . ////////////////////////////////////////////////////////////////////////////
20998 . ////////////////////////////////////////////////////////////////////////////
20999
21000 .chapter "Environment for running local transports" "CHAPenvironment" &&&
21001 "Environment for local transports"
21002 .scindex IIDenvlotra1 "local transports" "environment for"
21003 .scindex IIDenvlotra2 "environment" "local transports"
21004 .scindex IIDenvlotra3 "transport" "local; environment for"
21005 Local transports handle deliveries to files and pipes. (The &(autoreply)&
21006 transport can be thought of as similar to a pipe.) Exim always runs transports
21007 in subprocesses, under specified uids and gids. Typical deliveries to local
21008 mailboxes run under the uid and gid of the local user.
21009
21010 Exim also sets a specific current directory while running the transport; for
21011 some transports a home directory setting is also relevant. The &(pipe)&
21012 transport is the only one that sets up environment variables; see section
21013 &<<SECTpipeenv>>& for details.
21014
21015 The values used for the uid, gid, and the directories may come from several
21016 different places. In many cases, the router that handles the address associates
21017 settings with that address as a result of its &%check_local_user%&, &%group%&,
21018 or &%user%& options. However, values may also be given in the transport's own
21019 configuration, and these override anything that comes from the router.
21020
21021
21022
21023 .section "Concurrent deliveries" "SECID131"
21024 .cindex "concurrent deliveries"
21025 .cindex "simultaneous deliveries"
21026 If two different messages for the same local recipient arrive more or less
21027 simultaneously, the two delivery processes are likely to run concurrently. When
21028 the &(appendfile)& transport is used to write to a file, Exim applies locking
21029 rules to stop concurrent processes from writing to the same file at the same
21030 time.
21031
21032 However, when you use a &(pipe)& transport, it is up to you to arrange any
21033 locking that is needed. Here is a silly example:
21034 .code
21035 my_transport:
21036 driver = pipe
21037 command = /bin/sh -c 'cat >>/some/file'
21038 .endd
21039 This is supposed to write the message at the end of the file. However, if two
21040 messages arrive at the same time, the file will be scrambled. You can use the
21041 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
21042 file using the same algorithm that Exim itself uses.
21043
21044
21045
21046
21047 .section "Uids and gids" "SECTenvuidgid"
21048 .cindex "local transports" "uid and gid"
21049 .cindex "transport" "local; uid and gid"
21050 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
21051 overrides any group that the router set in the address, even if &%user%& is not
21052 set for the transport. This makes it possible, for example, to run local mail
21053 delivery under the uid of the recipient (set by the router), but in a special
21054 group (set by the transport). For example:
21055 .code
21056 # Routers ...
21057 # User/group are set by check_local_user in this router
21058 local_users:
21059 driver = accept
21060 check_local_user
21061 transport = group_delivery
21062
21063 # Transports ...
21064 # This transport overrides the group
21065 group_delivery:
21066 driver = appendfile
21067 file = /var/spool/mail/$local_part
21068 group = mail
21069 .endd
21070 If &%user%& is set for a transport, its value overrides what is set in the
21071 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
21072 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
21073 set.
21074
21075 .oindex "&%initgroups%&"
21076 When the uid is taken from the transport's configuration, the &[initgroups()]&
21077 function is called for the groups associated with that uid if the
21078 &%initgroups%& option is set for the transport. When the uid is not specified
21079 by the transport, but is associated with the address by a router, the option
21080 for calling &[initgroups()]& is taken from the router configuration.
21081
21082 .cindex "&(pipe)& transport" "uid for"
21083 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
21084 is set and &%user%& is not set, the uid of the process that called Exim to
21085 receive the message is used, and if &%group%& is not set, the corresponding
21086 original gid is also used.
21087
21088 This is the detailed preference order for obtaining a gid; the first of the
21089 following that is set is used:
21090
21091 .ilist
21092 A &%group%& setting of the transport;
21093 .next
21094 A &%group%& setting of the router;
21095 .next
21096 A gid associated with a user setting of the router, either as a result of
21097 &%check_local_user%& or an explicit non-numeric &%user%& setting;
21098 .next
21099 The group associated with a non-numeric &%user%& setting of the transport;
21100 .next
21101 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
21102 the uid is the creator's uid;
21103 .next
21104 The Exim gid if the Exim uid is being used as a default.
21105 .endlist
21106
21107 If, for example, the user is specified numerically on the router and there are
21108 no group settings, no gid is available. In this situation, an error occurs.
21109 This is different for the uid, for which there always is an ultimate default.
21110 The first of the following that is set is used:
21111
21112 .ilist
21113 A &%user%& setting of the transport;
21114 .next
21115 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
21116 .next
21117 A &%user%& setting of the router;
21118 .next
21119 A &%check_local_user%& setting of the router;
21120 .next
21121 The Exim uid.
21122 .endlist
21123
21124 Of course, an error will still occur if the uid that is chosen is on the
21125 &%never_users%& list.
21126
21127
21128
21129
21130
21131 .section "Current and home directories" "SECID132"
21132 .cindex "current directory for local transport"
21133 .cindex "home directory" "for local transport"
21134 .cindex "transport" "local; home directory for"
21135 .cindex "transport" "local; current directory for"
21136 Routers may set current and home directories for local transports by means of
21137 the &%transport_current_directory%& and &%transport_home_directory%& options.
21138 However, if the transport's &%current_directory%& or &%home_directory%& options
21139 are set, they override the router's values. In detail, the home directory
21140 for a local transport is taken from the first of these values that is set:
21141
21142 .ilist
21143 The &%home_directory%& option on the transport;
21144 .next
21145 The &%transport_home_directory%& option on the router;
21146 .next
21147 The password data if &%check_local_user%& is set on the router;
21148 .next
21149 The &%router_home_directory%& option on the router.
21150 .endlist
21151
21152 The current directory is taken from the first of these values that is set:
21153
21154 .ilist
21155 The &%current_directory%& option on the transport;
21156 .next
21157 The &%transport_current_directory%& option on the router.
21158 .endlist
21159
21160
21161 If neither the router nor the transport sets a current directory, Exim uses the
21162 value of the home directory, if it is set. Otherwise it sets the current
21163 directory to &_/_& before running a local transport.
21164
21165
21166
21167 .section "Expansion variables derived from the address" "SECID133"
21168 .vindex "&$domain$&"
21169 .vindex "&$local_part$&"
21170 .vindex "&$original_domain$&"
21171 Normally a local delivery is handling a single address, and in that case the
21172 variables such as &$domain$& and &$local_part$& are set during local
21173 deliveries. However, in some circumstances more than one address may be handled
21174 at once (for example, while writing batch SMTP for onward transmission by some
21175 other means). In this case, the variables associated with the local part are
21176 never set, &$domain$& is set only if all the addresses have the same domain,
21177 and &$original_domain$& is never set.
21178 .ecindex IIDenvlotra1
21179 .ecindex IIDenvlotra2
21180 .ecindex IIDenvlotra3
21181
21182
21183
21184
21185
21186
21187
21188 . ////////////////////////////////////////////////////////////////////////////
21189 . ////////////////////////////////////////////////////////////////////////////
21190
21191 .chapter "Generic options for transports" "CHAPtransportgeneric"
21192 .scindex IIDgenoptra1 "generic options" "transport"
21193 .scindex IIDgenoptra2 "options" "generic; for transports"
21194 .scindex IIDgenoptra3 "transport" "generic options for"
21195 The following generic options apply to all transports:
21196
21197
21198 .option body_only transports boolean false
21199 .cindex "transport" "body only"
21200 .cindex "message" "transporting body only"
21201 .cindex "body of message" "transporting"
21202 If this option is set, the message's headers are not transported. It is
21203 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
21204 or &(pipe)& transports, the settings of &%message_prefix%& and
21205 &%message_suffix%& should be checked, because this option does not
21206 automatically suppress them.
21207
21208
21209 .option current_directory transports string&!! unset
21210 .cindex "transport" "current directory for"
21211 This specifies the current directory that is to be set while running the
21212 transport, overriding any value that may have been set by the router.
21213 If the expansion fails for any reason, including forced failure, an error is
21214 logged, and delivery is deferred.
21215
21216
21217 .option disable_logging transports boolean false
21218 If this option is set true, nothing is logged for any
21219 deliveries by the transport or for any
21220 transport errors. You should not set this option unless you really, really know
21221 what you are doing.
21222
21223
21224 .option debug_print transports string&!! unset
21225 .cindex "testing" "variables in drivers"
21226 If this option is set and debugging is enabled (see the &%-d%& command line
21227 option), the string is expanded and included in the debugging output when the
21228 transport is run.
21229 If expansion of the string fails, the error message is written to the debugging
21230 output, and Exim carries on processing.
21231 This facility is provided to help with checking out the values of variables and
21232 so on when debugging driver configurations. For example, if a &%headers_add%&
21233 option is not working properly, &%debug_print%& could be used to output the
21234 variables it references. A newline is added to the text if it does not end with
21235 one.
21236 The variables &$transport_name$& and &$router_name$& contain the name of the
21237 transport and the router that called it.
21238
21239 .option delivery_date_add transports boolean false
21240 .cindex "&'Delivery-date:'& header line"
21241 If this option is true, a &'Delivery-date:'& header is added to the message.
21242 This gives the actual time the delivery was made. As this is not a standard
21243 header, Exim has a configuration option (&%delivery_date_remove%&) which
21244 requests its removal from incoming messages, so that delivered messages can
21245 safely be resent to other recipients.
21246
21247
21248 .option driver transports string unset
21249 This specifies which of the available transport drivers is to be used.
21250 There is no default, and this option must be set for every transport.
21251
21252
21253 .option envelope_to_add transports boolean false
21254 .cindex "&'Envelope-to:'& header line"
21255 If this option is true, an &'Envelope-to:'& header is added to the message.
21256 This gives the original address(es) in the incoming envelope that caused this
21257 delivery to happen. More than one address may be present if the transport is
21258 configured to handle several addresses at once, or if more than one original
21259 address was redirected to the same final address. As this is not a standard
21260 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
21261 its removal from incoming messages, so that delivered messages can safely be
21262 resent to other recipients.
21263
21264
21265 .option event_action transports string&!! unset
21266 .cindex events
21267 This option declares a string to be expanded for Exim's events mechanism.
21268 For details see chapter &<<CHAPevents>>&.
21269
21270
21271 .option group transports string&!! "Exim group"
21272 .cindex "transport" "group; specifying"
21273 This option specifies a gid for running the transport process, overriding any
21274 value that the router supplies, and also overriding any value associated with
21275 &%user%& (see below).
21276
21277
21278 .option headers_add transports list&!! unset
21279 .cindex "header lines" "adding in transport"
21280 .cindex "transport" "header lines; adding"
21281 This option specifies a list of text headers,
21282 newline-separated (by default, changeable in the usual way),
21283 which are (separately) expanded and added to the header
21284 portion of a message as it is transported, as described in section
21285 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
21286 routers. If the result of the expansion is an empty string, or if the expansion
21287 is forced to fail, no action is taken. Other expansion failures are treated as
21288 errors and cause the delivery to be deferred.
21289
21290 Unlike most options, &%headers_add%& can be specified multiple times
21291 for a transport; all listed headers are added.
21292
21293
21294 .option headers_only transports boolean false
21295 .cindex "transport" "header lines only"
21296 .cindex "message" "transporting headers only"
21297 .cindex "header lines" "transporting"
21298 If this option is set, the message's body is not transported. It is mutually
21299 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
21300 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
21301 checked, since this option does not automatically suppress them.
21302
21303
21304 .option headers_remove transports list&!! unset
21305 .cindex "header lines" "removing"
21306 .cindex "transport" "header lines; removing"
21307 This option specifies a list of header names,
21308 colon-separated (by default, changeable in the usual way);
21309 these headers are omitted from the message as it is transported, as described
21310 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
21311 routers.
21312 Each list item is separately expanded.
21313 If the result of the expansion is an empty string, or if the expansion
21314 is forced to fail, no action is taken. Other expansion failures are treated as
21315 errors and cause the delivery to be deferred.
21316
21317 Unlike most options, &%headers_remove%& can be specified multiple times
21318 for a transport; all listed headers are removed.
21319
21320 &*Warning*&: Because of the separate expansion of the list items,
21321 items that contain a list separator must have it doubled.
21322 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
21323
21324
21325
21326 .option headers_rewrite transports string unset
21327 .cindex "transport" "header lines; rewriting"
21328 .cindex "rewriting" "at transport time"
21329 This option allows addresses in header lines to be rewritten at transport time,
21330 that is, as the message is being copied to its destination. The contents of the
21331 option are a colon-separated list of rewriting rules. Each rule is in exactly
21332 the same form as one of the general rewriting rules that are applied when a
21333 message is received. These are described in chapter &<<CHAPrewrite>>&. For
21334 example,
21335 .code
21336 headers_rewrite = a@b c@d f : \
21337 x@y w@z
21338 .endd
21339 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
21340 &'w@z'& in all address-bearing header lines. The rules are applied to the
21341 header lines just before they are written out at transport time, so they affect
21342 only those copies of the message that pass through the transport. However, only
21343 the message's original header lines, and any that were added by a system
21344 filter, are rewritten. If a router or transport adds header lines, they are not
21345 affected by this option. These rewriting rules are &'not'& applied to the
21346 envelope. You can change the return path using &%return_path%&, but you cannot
21347 change envelope recipients at this time.
21348
21349
21350 .option home_directory transports string&!! unset
21351 .cindex "transport" "home directory for"
21352 .vindex "&$home$&"
21353 This option specifies a home directory setting for a local transport,
21354 overriding any value that may be set by the router. The home directory is
21355 placed in &$home$& while expanding the transport's private options. It is also
21356 used as the current directory if no current directory is set by the
21357 &%current_directory%& option on the transport or the
21358 &%transport_current_directory%& option on the router. If the expansion fails
21359 for any reason, including forced failure, an error is logged, and delivery is
21360 deferred.
21361
21362
21363 .option initgroups transports boolean false
21364 .cindex "additional groups"
21365 .cindex "groups" "additional"
21366 .cindex "transport" "group; additional"
21367 If this option is true and the uid for the delivery process is provided by the
21368 transport, the &[initgroups()]& function is called when running the transport
21369 to ensure that any additional groups associated with the uid are set up.
21370
21371
21372 .option max_parallel transports integer&!! unset
21373 .cindex limit "transport parallelism"
21374 .cindex transport "parallel processes"
21375 .cindex transport "concurrency limit"
21376 .cindex "delivery" "parallelism for transport"
21377 If this option is set and expands to an integer greater than zero
21378 it limits the number of concurrent runs of the transport.
21379 The control does not apply to shadow transports.
21380
21381 .cindex "hints database" "transport concurrency control"
21382 Exim implements this control by means of a hints database in which a record is
21383 incremented whenever a transport process is being created. The record
21384 is decremented and possibly removed when the process terminates.
21385 Obviously there is scope for
21386 records to get left lying around if there is a system or program crash. To
21387 guard against this, Exim ignores any records that are more than six hours old.
21388
21389 If you use this option, you should also arrange to delete the
21390 relevant hints database whenever your system reboots. The names of the files
21391 start with &_misc_& and they are kept in the &_spool/db_& directory. There
21392 may be one or two files, depending on the type of DBM in use. The same files
21393 are used for ETRN and smtp transport serialization.
21394
21395
21396 .option message_size_limit transports string&!! 0
21397 .cindex "limit" "message size per transport"
21398 .cindex "size" "of message, limit"
21399 .cindex "transport" "message size; limiting"
21400 This option controls the size of messages passed through the transport. It is
21401 expanded before use; the result of the expansion must be a sequence of decimal
21402 digits, optionally followed by K or M. If the expansion fails for any reason,
21403 including forced failure, or if the result is not of the required form,
21404 delivery is deferred. If the value is greater than zero and the size of a
21405 message exceeds this limit, the address is failed. If there is any chance that
21406 the resulting bounce message could be routed to the same transport, you should
21407 ensure that &%return_size_limit%& is less than the transport's
21408 &%message_size_limit%&, as otherwise the bounce message will fail to get
21409 delivered.
21410
21411
21412
21413 .option rcpt_include_affixes transports boolean false
21414 .cindex "prefix" "for local part, including in envelope"
21415 .cindex "suffix for local part" "including in envelope"
21416 .cindex "local part" "prefix"
21417 .cindex "local part" "suffix"
21418 When this option is false (the default), and an address that has had any
21419 affixes (prefixes or suffixes) removed from the local part is delivered by any
21420 form of SMTP or LMTP, the affixes are not included. For example, if a router
21421 that contains
21422 .code
21423 local_part_prefix = *-
21424 .endd
21425 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
21426 is delivered with
21427 .code
21428 RCPT TO:<xyz@some.domain>
21429 .endd
21430 This is also the case when an ACL-time callout is being used to verify a
21431 recipient address. However, if &%rcpt_include_affixes%& is set true, the
21432 whole local part is included in the RCPT command. This option applies to BSMTP
21433 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
21434 &(lmtp)& and &(smtp)& transports.
21435
21436
21437 .option retry_use_local_part transports boolean "see below"
21438 .cindex "hints database" "retry keys"
21439 When a delivery suffers a temporary failure, a retry record is created
21440 in Exim's hints database. For remote deliveries, the key for the retry record
21441 is based on the name and/or IP address of the failing remote host. For local
21442 deliveries, the key is normally the entire address, including both the local
21443 part and the domain. This is suitable for most common cases of local delivery
21444 temporary failure &-- for example, exceeding a mailbox quota should delay only
21445 deliveries to that mailbox, not to the whole domain.
21446
21447 However, in some special cases you may want to treat a temporary local delivery
21448 as a failure associated with the domain, and not with a particular local part.
21449 (For example, if you are storing all mail for some domain in files.) You can do
21450 this by setting &%retry_use_local_part%& false.
21451
21452 For all the local transports, its default value is true. For remote transports,
21453 the default value is false for tidiness, but changing the value has no effect
21454 on a remote transport in the current implementation.
21455
21456
21457 .option return_path transports string&!! unset
21458 .cindex "envelope sender"
21459 .cindex "transport" "return path; changing"
21460 .cindex "return path" "changing in transport"
21461 If this option is set, the string is expanded at transport time and replaces
21462 the existing return path (envelope sender) value in the copy of the message
21463 that is being delivered. An empty return path is permitted. This feature is
21464 designed for remote deliveries, where the value of this option is used in the
21465 SMTP MAIL command. If you set &%return_path%& for a local transport, the
21466 only effect is to change the address that is placed in the &'Return-path:'&
21467 header line, if one is added to the message (see the next option).
21468
21469 &*Note:*& A changed return path is not logged unless you add
21470 &%return_path_on_delivery%& to the log selector.
21471
21472 .vindex "&$return_path$&"
21473 The expansion can refer to the existing value via &$return_path$&. This is
21474 either the message's envelope sender, or an address set by the
21475 &%errors_to%& option on a router. If the expansion is forced to fail, no
21476 replacement occurs; if it fails for another reason, delivery is deferred. This
21477 option can be used to support VERP (Variable Envelope Return Paths) &-- see
21478 section &<<SECTverp>>&.
21479
21480 &*Note*&: If a delivery error is detected locally, including the case when a
21481 remote server rejects a message at SMTP time, the bounce message is not sent to
21482 the value of this option. It is sent to the previously set errors address.
21483 This defaults to the incoming sender address, but can be changed by setting
21484 &%errors_to%& in a router.
21485
21486
21487
21488 .option return_path_add transports boolean false
21489 .cindex "&'Return-path:'& header line"
21490 If this option is true, a &'Return-path:'& header is added to the message.
21491 Although the return path is normally available in the prefix line of BSD
21492 mailboxes, this is commonly not displayed by MUAs, and so the user does not
21493 have easy access to it.
21494
21495 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
21496 the delivery SMTP server makes the final delivery"&. This implies that this
21497 header should not be present in incoming messages. Exim has a configuration
21498 option, &%return_path_remove%&, which requests removal of this header from
21499 incoming messages, so that delivered messages can safely be resent to other
21500 recipients.
21501
21502
21503 .option shadow_condition transports string&!! unset
21504 See &%shadow_transport%& below.
21505
21506
21507 .option shadow_transport transports string unset
21508 .cindex "shadow transport"
21509 .cindex "transport" "shadow"
21510 A local transport may set the &%shadow_transport%& option to the name of
21511 another local transport. Shadow remote transports are not supported.
21512
21513 Whenever a delivery to the main transport succeeds, and either
21514 &%shadow_condition%& is unset, or its expansion does not result in the empty
21515 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
21516 passed to the shadow transport, with the same delivery address or addresses. If
21517 expansion fails, no action is taken except that non-forced expansion failures
21518 cause a log line to be written.
21519
21520 The result of the shadow transport is discarded and does not affect the
21521 subsequent processing of the message. Only a single level of shadowing is
21522 provided; the &%shadow_transport%& option is ignored on any transport when it
21523 is running as a shadow. Options concerned with output from pipes are also
21524 ignored. The log line for the successful delivery has an item added on the end,
21525 of the form
21526 .code
21527 ST=<shadow transport name>
21528 .endd
21529 If the shadow transport did not succeed, the error message is put in
21530 parentheses afterwards. Shadow transports can be used for a number of different
21531 purposes, including keeping more detailed log information than Exim normally
21532 provides, and implementing automatic acknowledgment policies based on message
21533 headers that some sites insist on.
21534
21535
21536 .option transport_filter transports string&!! unset
21537 .cindex "transport" "filter"
21538 .cindex "filter" "transport filter"
21539 This option sets up a filtering (in the Unix shell sense) process for messages
21540 at transport time. It should not be confused with mail filtering as set up by
21541 individual users or via a system filter.
21542 If unset, or expanding to an empty string, no filtering is done.
21543
21544 When the message is about to be written out, the command specified by
21545 &%transport_filter%& is started up in a separate, parallel process, and
21546 the entire message, including the header lines, is passed to it on its standard
21547 input (this in fact is done from a third process, to avoid deadlock). The
21548 command must be specified as an absolute path.
21549
21550 The lines of the message that are written to the transport filter are
21551 terminated by newline (&"\n"&). The message is passed to the filter before any
21552 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
21553 lines beginning with a dot, and also before any processing implied by the
21554 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
21555 &(pipe)& transports.
21556
21557 The standard error for the filter process is set to the same destination as its
21558 standard output; this is read and written to the message's ultimate
21559 destination. The process that writes the message to the filter, the
21560 filter itself, and the original process that reads the result and delivers it
21561 are all run in parallel, like a shell pipeline.
21562
21563 The filter can perform any transformations it likes, but of course should take
21564 care not to break RFC 2822 syntax. Exim does not check the result, except to
21565 test for a final newline when SMTP is in use. All messages transmitted over
21566 SMTP must end with a newline, so Exim supplies one if it is missing.
21567
21568 .cindex "content scanning" "per user"
21569 A transport filter can be used to provide content-scanning on a per-user basis
21570 at delivery time if the only required effect of the scan is to modify the
21571 message. For example, a content scan could insert a new header line containing
21572 a spam score. This could be interpreted by a filter in the user's MUA. It is
21573 not possible to discard a message at this stage.
21574
21575 .cindex "SMTP" "SIZE"
21576 A problem might arise if the filter increases the size of a message that is
21577 being sent down an SMTP connection. If the receiving SMTP server has indicated
21578 support for the SIZE parameter, Exim will have sent the size of the message
21579 at the start of the SMTP session. If what is actually sent is substantially
21580 more, the server might reject the message. This can be worked round by setting
21581 the &%size_addition%& option on the &(smtp)& transport, either to allow for
21582 additions to the message, or to disable the use of SIZE altogether.
21583
21584 .vindex "&$pipe_addresses$&"
21585 The value of the &%transport_filter%& option is the command string for starting
21586 the filter, which is run directly from Exim, not under a shell. The string is
21587 parsed by Exim in the same way as a command string for the &(pipe)& transport:
21588 Exim breaks it up into arguments and then expands each argument separately (see
21589 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
21590 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
21591 of arguments, one for each address that applies to this delivery. (This isn't
21592 an ideal name for this feature here, but as it was already implemented for the
21593 &(pipe)& transport, it seemed sensible not to change it.)
21594
21595 .vindex "&$host$&"
21596 .vindex "&$host_address$&"
21597 The expansion variables &$host$& and &$host_address$& are available when the
21598 transport is a remote one. They contain the name and IP address of the host to
21599 which the message is being sent. For example:
21600 .code
21601 transport_filter = /some/directory/transport-filter.pl \
21602 $host $host_address $sender_address $pipe_addresses
21603 .endd
21604
21605 Two problems arise if you want to use more complicated expansion items to
21606 generate transport filter commands, both of which due to the fact that the
21607 command is split up &'before'& expansion.
21608 .ilist
21609 If an expansion item contains white space, you must quote it, so that it is all
21610 part of the same command item. If the entire option setting is one such
21611 expansion item, you have to take care what kind of quoting you use. For
21612 example:
21613 .code
21614 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
21615 .endd
21616 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
21617 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
21618 stripped by Exim when it read the option's value. When the value is used, if
21619 the single quotes were missing, the line would be split into two items,
21620 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
21621 Exim tried to expand the first one.
21622 .next
21623 Except for the special case of &$pipe_addresses$& that is mentioned above, an
21624 expansion cannot generate multiple arguments, or a command name followed by
21625 arguments. Consider this example:
21626 .code
21627 transport_filter = ${lookup{$host}lsearch{/a/file}\
21628 {$value}{/bin/cat}}
21629 .endd
21630 The result of the lookup is interpreted as the name of the command, even
21631 if it contains white space. The simplest way round this is to use a shell:
21632 .code
21633 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
21634 {$value}{/bin/cat}}
21635 .endd
21636 .endlist
21637
21638 The filter process is run under the same uid and gid as the normal delivery.
21639 For remote deliveries this is the Exim uid/gid by default. The command should
21640 normally yield a zero return code. Transport filters are not supposed to fail.
21641 A non-zero code is taken to mean that the transport filter encountered some
21642 serious problem. Delivery of the message is deferred; the message remains on
21643 the queue and is tried again later. It is not possible to cause a message to be
21644 bounced from a transport filter.
21645
21646 If a transport filter is set on an autoreply transport, the original message is
21647 passed through the filter as it is being copied into the newly generated
21648 message, which happens if the &%return_message%& option is set.
21649
21650
21651 .option transport_filter_timeout transports time 5m
21652 .cindex "transport" "filter, timeout"
21653 When Exim is reading the output of a transport filter, it applies a timeout
21654 that can be set by this option. Exceeding the timeout is normally treated as a
21655 temporary delivery failure. However, if a transport filter is used with a
21656 &(pipe)& transport, a timeout in the transport filter is treated in the same
21657 way as a timeout in the pipe command itself. By default, a timeout is a hard
21658 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
21659 becomes a temporary error.
21660
21661
21662 .option user transports string&!! "Exim user"
21663 .cindex "uid (user id)" "local delivery"
21664 .cindex "transport" "user, specifying"
21665 This option specifies the user under whose uid the delivery process is to be
21666 run, overriding any uid that may have been set by the router. If the user is
21667 given as a name, the uid is looked up from the password data, and the
21668 associated group is taken as the value of the gid to be used if the &%group%&
21669 option is not set.
21670
21671 For deliveries that use local transports, a user and group are normally
21672 specified explicitly or implicitly (for example, as a result of
21673 &%check_local_user%&) by the router or transport.
21674
21675 .cindex "hints database" "access by remote transport"
21676 For remote transports, you should leave this option unset unless you really are
21677 sure you know what you are doing. When a remote transport is running, it needs
21678 to be able to access Exim's hints databases, because each host may have its own
21679 retry data.
21680 .ecindex IIDgenoptra1
21681 .ecindex IIDgenoptra2
21682 .ecindex IIDgenoptra3
21683
21684
21685
21686
21687
21688
21689 . ////////////////////////////////////////////////////////////////////////////
21690 . ////////////////////////////////////////////////////////////////////////////
21691
21692 .chapter "Address batching in local transports" "CHAPbatching" &&&
21693 "Address batching"
21694 .cindex "transport" "local; address batching in"
21695 The only remote transport (&(smtp)&) is normally configured to handle more than
21696 one address at a time, so that when several addresses are routed to the same
21697 remote host, just one copy of the message is sent. Local transports, however,
21698 normally handle one address at a time. That is, a separate instance of the
21699 transport is run for each address that is routed to the transport. A separate
21700 copy of the message is delivered each time.
21701
21702 .cindex "batched local delivery"
21703 .oindex "&%batch_max%&"
21704 .oindex "&%batch_id%&"
21705 In special cases, it may be desirable to handle several addresses at once in a
21706 local transport, for example:
21707
21708 .ilist
21709 In an &(appendfile)& transport, when storing messages in files for later
21710 delivery by some other means, a single copy of the message with multiple
21711 recipients saves space.
21712 .next
21713 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
21714 a single copy saves time, and is the normal way LMTP is expected to work.
21715 .next
21716 In a &(pipe)& transport, when passing the message
21717 to a scanner program or
21718 to some other delivery mechanism such as UUCP, multiple recipients may be
21719 acceptable.
21720 .endlist
21721
21722 These three local transports all have the same options for controlling multiple
21723 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
21724 repeating the information for each transport, these options are described here.
21725
21726 The &%batch_max%& option specifies the maximum number of addresses that can be
21727 delivered together in a single run of the transport. Its default value is one
21728 (no batching). When more than one address is routed to a transport that has a
21729 &%batch_max%& value greater than one, the addresses are delivered in a batch
21730 (that is, in a single run of the transport with multiple recipients), subject
21731 to certain conditions:
21732
21733 .ilist
21734 .vindex "&$local_part$&"
21735 If any of the transport's options contain a reference to &$local_part$&, no
21736 batching is possible.
21737 .next
21738 .vindex "&$domain$&"
21739 If any of the transport's options contain a reference to &$domain$&, only
21740 addresses with the same domain are batched.
21741 .next
21742 .cindex "customizing" "batching condition"
21743 If &%batch_id%& is set, it is expanded for each address, and only those
21744 addresses with the same expanded value are batched. This allows you to specify
21745 customized batching conditions. Failure of the expansion for any reason,
21746 including forced failure, disables batching, but it does not stop the delivery
21747 from taking place.
21748 .next
21749 Batched addresses must also have the same errors address (where to send
21750 delivery errors), the same header additions and removals, the same user and
21751 group for the transport, and if a host list is present, the first host must
21752 be the same.
21753 .endlist
21754
21755 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
21756 both when the file or pipe command is specified in the transport, and when it
21757 is specified by a &(redirect)& router, but all the batched addresses must of
21758 course be routed to the same file or pipe command. These two transports have an
21759 option called &%use_bsmtp%&, which causes them to deliver the message in
21760 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
21761 &%check_string%& and &%escape_string%& options are forced to the values
21762 .code
21763 check_string = "."
21764 escape_string = ".."
21765 .endd
21766 when batched SMTP is in use. A full description of the batch SMTP mechanism is
21767 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
21768 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
21769
21770 .cindex "&'Envelope-to:'& header line"
21771 If the generic &%envelope_to_add%& option is set for a batching transport, the
21772 &'Envelope-to:'& header that is added to the message contains all the addresses
21773 that are being processed together. If you are using a batching &(appendfile)&
21774 transport without &%use_bsmtp%&, the only way to preserve the recipient
21775 addresses is to set the &%envelope_to_add%& option.
21776
21777 .cindex "&(pipe)& transport" "with multiple addresses"
21778 .vindex "&$pipe_addresses$&"
21779 If you are using a &(pipe)& transport without BSMTP, and setting the
21780 transport's &%command%& option, you can include &$pipe_addresses$& as part of
21781 the command. This is not a true variable; it is a bit of magic that causes each
21782 of the recipient addresses to be inserted into the command as a separate
21783 argument. This provides a way of accessing all the addresses that are being
21784 delivered in the batch. &*Note:*& This is not possible for pipe commands that
21785 are specified by a &(redirect)& router.
21786
21787
21788
21789
21790 . ////////////////////////////////////////////////////////////////////////////
21791 . ////////////////////////////////////////////////////////////////////////////
21792
21793 .chapter "The appendfile transport" "CHAPappendfile"
21794 .scindex IIDapptra1 "&(appendfile)& transport"
21795 .scindex IIDapptra2 "transports" "&(appendfile)&"
21796 .cindex "directory creation"
21797 .cindex "creating directories"
21798 The &(appendfile)& transport delivers a message by appending it to an existing
21799 file, or by creating an entirely new file in a specified directory. Single
21800 files to which messages are appended can be in the traditional Unix mailbox
21801 format, or optionally in the MBX format supported by the Pine MUA and
21802 University of Washington IMAP daemon, &'inter alia'&. When each message is
21803 being delivered as a separate file, &"maildir"& format can optionally be used
21804 to give added protection against failures that happen part-way through the
21805 delivery. A third form of separate-file delivery known as &"mailstore"& is also
21806 supported. For all file formats, Exim attempts to create as many levels of
21807 directory as necessary, provided that &%create_directory%& is set.
21808
21809 The code for the optional formats is not included in the Exim binary by
21810 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
21811 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
21812 included.
21813
21814 .cindex "quota" "system"
21815 Exim recognizes system quota errors, and generates an appropriate message. Exim
21816 also supports its own quota control within the transport, for use when the
21817 system facility is unavailable or cannot be used for some reason.
21818
21819 If there is an error while appending to a file (for example, quota exceeded or
21820 partition filled), Exim attempts to reset the file's length and last
21821 modification time back to what they were before. If there is an error while
21822 creating an entirely new file, the new file is removed.
21823
21824 Before appending to a file, a number of security checks are made, and the
21825 file is locked. A detailed description is given below, after the list of
21826 private options.
21827
21828 The &(appendfile)& transport is most commonly used for local deliveries to
21829 users' mailboxes. However, it can also be used as a pseudo-remote transport for
21830 putting messages into files for remote delivery by some means other than Exim.
21831 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
21832 option).
21833
21834
21835
21836 .section "The file and directory options" "SECTfildiropt"
21837 The &%file%& option specifies a single file, to which the message is appended;
21838 the &%directory%& option specifies a directory, in which a new file containing
21839 the message is created. Only one of these two options can be set, and for
21840 normal deliveries to mailboxes, one of them &'must'& be set.
21841
21842 .vindex "&$address_file$&"
21843 .vindex "&$local_part$&"
21844 However, &(appendfile)& is also used for delivering messages to files or
21845 directories whose names (or parts of names) are obtained from alias,
21846 forwarding, or filtering operations (for example, a &%save%& command in a
21847 user's Exim filter). When such a transport is running, &$local_part$& contains
21848 the local part that was aliased or forwarded, and &$address_file$& contains the
21849 name (or partial name) of the file or directory generated by the redirection
21850 operation. There are two cases:
21851
21852 .ilist
21853 If neither &%file%& nor &%directory%& is set, the redirection operation
21854 must specify an absolute path (one that begins with &`/`&). This is the most
21855 common case when users with local accounts use filtering to sort mail into
21856 different folders. See for example, the &(address_file)& transport in the
21857 default configuration. If the path ends with a slash, it is assumed to be the
21858 name of a directory. A delivery to a directory can also be forced by setting
21859 &%maildir_format%& or &%mailstore_format%&.
21860 .next
21861 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
21862 used to determine the file or directory name for the delivery. Normally, the
21863 contents of &$address_file$& are used in some way in the string expansion.
21864 .endlist
21865
21866
21867 .cindex "Sieve filter" "configuring &(appendfile)&"
21868 .cindex "Sieve filter" "relative mailbox path handling"
21869 As an example of the second case, consider an environment where users do not
21870 have home directories. They may be permitted to use Exim filter commands of the
21871 form:
21872 .code
21873 save folder23
21874 .endd
21875 or Sieve filter commands of the form:
21876 .code
21877 require "fileinto";
21878 fileinto "folder23";
21879 .endd
21880 In this situation, the expansion of &%file%& or &%directory%& in the transport
21881 must transform the relative path into an appropriate absolute file name. In the
21882 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
21883 is used as a result of a &"keep"& action in the filter. This example shows one
21884 way of handling this requirement:
21885 .code
21886 file = ${if eq{$address_file}{inbox} \
21887 {/var/mail/$local_part} \
21888 {${if eq{${substr_0_1:$address_file}}{/} \
21889 {$address_file} \
21890 {$home/mail/$address_file} \
21891 }} \
21892 }
21893 .endd
21894 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
21895 location, absolute paths are used without change, and other folders are in the
21896 &_mail_& directory within the home directory.
21897
21898 &*Note 1*&: While processing an Exim filter, a relative path such as
21899 &_folder23_& is turned into an absolute path if a home directory is known to
21900 the router. In particular, this is the case if &%check_local_user%& is set. If
21901 you want to prevent this happening at routing time, you can set
21902 &%router_home_directory%& empty. This forces the router to pass the relative
21903 path to the transport.
21904
21905 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
21906 the &%file%& or &%directory%& option is still used if it is set.
21907
21908
21909
21910
21911 .section "Private options for appendfile" "SECID134"
21912 .cindex "options" "&(appendfile)& transport"
21913
21914
21915
21916 .option allow_fifo appendfile boolean false
21917 .cindex "fifo (named pipe)"
21918 .cindex "named pipe (fifo)"
21919 .cindex "pipe" "named (fifo)"
21920 Setting this option permits delivery to named pipes (FIFOs) as well as to
21921 regular files. If no process is reading the named pipe at delivery time, the
21922 delivery is deferred.
21923
21924
21925 .option allow_symlink appendfile boolean false
21926 .cindex "symbolic link" "to mailbox"
21927 .cindex "mailbox" "symbolic link"
21928 By default, &(appendfile)& will not deliver if the path name for the file is
21929 that of a symbolic link. Setting this option relaxes that constraint, but there
21930 are security issues involved in the use of symbolic links. Be sure you know
21931 what you are doing if you set this. Details of exactly what this option affects
21932 are included in the discussion which follows this list of options.
21933
21934
21935 .option batch_id appendfile string&!! unset
21936 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21937 However, batching is automatically disabled for &(appendfile)& deliveries that
21938 happen as a result of forwarding or aliasing or other redirection directly to a
21939 file.
21940
21941
21942 .option batch_max appendfile integer 1
21943 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21944
21945
21946 .option check_group appendfile boolean false
21947 When this option is set, the group owner of the file defined by the &%file%&
21948 option is checked to see that it is the same as the group under which the
21949 delivery process is running. The default setting is false because the default
21950 file mode is 0600, which means that the group is irrelevant.
21951
21952
21953 .option check_owner appendfile boolean true
21954 When this option is set, the owner of the file defined by the &%file%& option
21955 is checked to ensure that it is the same as the user under which the delivery
21956 process is running.
21957
21958
21959 .option check_string appendfile string "see below"
21960 .cindex "&""From""& line"
21961 As &(appendfile)& writes the message, the start of each line is tested for
21962 matching &%check_string%&, and if it does, the initial matching characters are
21963 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
21964 a literal string, not a regular expression, and the case of any letters it
21965 contains is significant.
21966
21967 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
21968 are forced to &"."& and &".."& respectively, and any settings in the
21969 configuration are ignored. Otherwise, they default to &"From&~"& and
21970 &">From&~"& when the &%file%& option is set, and unset when any of the
21971 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
21972
21973 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
21974 suitable for traditional &"BSD"& mailboxes, where a line beginning with
21975 &"From&~"& indicates the start of a new message. All four options need changing
21976 if another format is used. For example, to deliver to mailboxes in MMDF format:
21977 .cindex "MMDF format mailbox"
21978 .cindex "mailbox" "MMDF format"
21979 .code
21980 check_string = "\1\1\1\1\n"
21981 escape_string = "\1\1\1\1 \n"
21982 message_prefix = "\1\1\1\1\n"
21983 message_suffix = "\1\1\1\1\n"
21984 .endd
21985 .option create_directory appendfile boolean true
21986 .cindex "directory creation"
21987 When this option is true, Exim attempts to create any missing superior
21988 directories for the file that it is about to write. A created directory's mode
21989 is given by the &%directory_mode%& option.
21990
21991 The group ownership of a newly created directory is highly dependent on the
21992 operating system (and possibly the file system) that is being used. For
21993 example, in Solaris, if the parent directory has the setgid bit set, its group
21994 is propagated to the child; if not, the currently set group is used. However,
21995 in FreeBSD, the parent's group is always used.
21996
21997
21998
21999 .option create_file appendfile string anywhere
22000 This option constrains the location of files and directories that are created
22001 by this transport. It applies to files defined by the &%file%& option and
22002 directories defined by the &%directory%& option. In the case of maildir
22003 delivery, it applies to the top level directory, not the maildir directories
22004 beneath.
22005
22006 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
22007 &"belowhome"&. In the second and third cases, a home directory must have been
22008 set for the transport. This option is not useful when an explicit file name is
22009 given for normal mailbox deliveries. It is intended for the case when file
22010 names are generated from users' &_.forward_& files. These are usually handled
22011 by an &(appendfile)& transport called &%address_file%&. See also
22012 &%file_must_exist%&.
22013
22014
22015 .option directory appendfile string&!! unset
22016 This option is mutually exclusive with the &%file%& option, but one of &%file%&
22017 or &%directory%& must be set, unless the delivery is the direct result of a
22018 redirection (see section &<<SECTfildiropt>>&).
22019
22020 When &%directory%& is set, the string is expanded, and the message is delivered
22021 into a new file or files in or below the given directory, instead of being
22022 appended to a single mailbox file. A number of different formats are provided
22023 (see &%maildir_format%& and &%mailstore_format%&), and see section
22024 &<<SECTopdir>>& for further details of this form of delivery.
22025
22026
22027 .option directory_file appendfile string&!! "see below"
22028 .cindex "base62"
22029 .vindex "&$inode$&"
22030 When &%directory%& is set, but neither &%maildir_format%& nor
22031 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
22032 whose name is obtained by expanding this string. The default value is:
22033 .code
22034 q${base62:$tod_epoch}-$inode
22035 .endd
22036 This generates a unique name from the current time, in base 62 form, and the
22037 inode of the file. The variable &$inode$& is available only when expanding this
22038 option.
22039
22040
22041 .option directory_mode appendfile "octal integer" 0700
22042 If &(appendfile)& creates any directories as a result of the
22043 &%create_directory%& option, their mode is specified by this option.
22044
22045
22046 .option escape_string appendfile string "see description"
22047 See &%check_string%& above.
22048
22049
22050 .option file appendfile string&!! unset
22051 This option is mutually exclusive with the &%directory%& option, but one of
22052 &%file%& or &%directory%& must be set, unless the delivery is the direct result
22053 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
22054 specifies a single file, to which the message is appended. One or more of
22055 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
22056 &%file%&.
22057
22058 .cindex "NFS" "lock file"
22059 .cindex "locking files"
22060 .cindex "lock files"
22061 If you are using more than one host to deliver over NFS into the same
22062 mailboxes, you should always use lock files.
22063
22064 The string value is expanded for each delivery, and must yield an absolute
22065 path. The most common settings of this option are variations on one of these
22066 examples:
22067 .code
22068 file = /var/spool/mail/$local_part
22069 file = /home/$local_part/inbox
22070 file = $home/inbox
22071 .endd
22072 .cindex "&""sticky""& bit"
22073 In the first example, all deliveries are done into the same directory. If Exim
22074 is configured to use lock files (see &%use_lockfile%& below) it must be able to
22075 create a file in the directory, so the &"sticky"& bit must be turned on for
22076 deliveries to be possible, or alternatively the &%group%& option can be used to
22077 run the delivery under a group id which has write access to the directory.
22078
22079
22080
22081 .option file_format appendfile string unset
22082 .cindex "file" "mailbox; checking existing format"
22083 This option requests the transport to check the format of an existing file
22084 before adding to it. The check consists of matching a specific string at the
22085 start of the file. The value of the option consists of an even number of
22086 colon-separated strings. The first of each pair is the test string, and the
22087 second is the name of a transport. If the transport associated with a matched
22088 string is not the current transport, control is passed over to the other
22089 transport. For example, suppose the standard &(local_delivery)& transport has
22090 this added to it:
22091 .code
22092 file_format = "From : local_delivery :\
22093 \1\1\1\1\n : local_mmdf_delivery"
22094 .endd
22095 Mailboxes that begin with &"From"& are still handled by this transport, but if
22096 a mailbox begins with four binary ones followed by a newline, control is passed
22097 to a transport called &%local_mmdf_delivery%&, which presumably is configured
22098 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
22099 is assumed to match the current transport. If the start of a mailbox doesn't
22100 match any string, or if the transport named for a given string is not defined,
22101 delivery is deferred.
22102
22103
22104 .option file_must_exist appendfile boolean false
22105 If this option is true, the file specified by the &%file%& option must exist.
22106 A temporary error occurs if it does not, causing delivery to be deferred.
22107 If this option is false, the file is created if it does not exist.
22108
22109
22110 .option lock_fcntl_timeout appendfile time 0s
22111 .cindex "timeout" "mailbox locking"
22112 .cindex "mailbox" "locking, blocking and non-blocking"
22113 .cindex "locking files"
22114 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
22115 when locking an open mailbox file. If the call fails, the delivery process
22116 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
22117 Non-blocking calls are used so that the file is not kept open during the wait
22118 for the lock; the reason for this is to make it as safe as possible for
22119 deliveries over NFS in the case when processes might be accessing an NFS
22120 mailbox without using a lock file. This should not be done, but
22121 misunderstandings and hence misconfigurations are not unknown.
22122
22123 On a busy system, however, the performance of a non-blocking lock approach is
22124 not as good as using a blocking lock with a timeout. In this case, the waiting
22125 is done inside the system call, and Exim's delivery process acquires the lock
22126 and can proceed as soon as the previous lock holder releases it.
22127
22128 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
22129 timeout, are used. There may still be some retrying: the maximum number of
22130 retries is
22131 .code
22132 (lock_retries * lock_interval) / lock_fcntl_timeout
22133 .endd
22134 rounded up to the next whole number. In other words, the total time during
22135 which &(appendfile)& is trying to get a lock is roughly the same, unless
22136 &%lock_fcntl_timeout%& is set very large.
22137
22138 You should consider setting this option if you are getting a lot of delayed
22139 local deliveries because of errors of the form
22140 .code
22141 failed to lock mailbox /some/file (fcntl)
22142 .endd
22143
22144 .option lock_flock_timeout appendfile time 0s
22145 This timeout applies to file locking when using &[flock()]& (see
22146 &%use_flock%&); the timeout operates in a similar manner to
22147 &%lock_fcntl_timeout%&.
22148
22149
22150 .option lock_interval appendfile time 3s
22151 This specifies the time to wait between attempts to lock the file. See below
22152 for details of locking.
22153
22154
22155 .option lock_retries appendfile integer 10
22156 This specifies the maximum number of attempts to lock the file. A value of zero
22157 is treated as 1. See below for details of locking.
22158
22159
22160 .option lockfile_mode appendfile "octal integer" 0600
22161 This specifies the mode of the created lock file, when a lock file is being
22162 used (see &%use_lockfile%& and &%use_mbx_lock%&).
22163
22164
22165 .option lockfile_timeout appendfile time 30m
22166 .cindex "timeout" "mailbox locking"
22167 When a lock file is being used (see &%use_lockfile%&), if a lock file already
22168 exists and is older than this value, it is assumed to have been left behind by
22169 accident, and Exim attempts to remove it.
22170
22171
22172 .option mailbox_filecount appendfile string&!! unset
22173 .cindex "mailbox" "specifying size of"
22174 .cindex "size" "of mailbox"
22175 If this option is set, it is expanded, and the result is taken as the current
22176 number of files in the mailbox. It must be a decimal number, optionally
22177 followed by K or M. This provides a way of obtaining this information from an
22178 external source that maintains the data.
22179
22180
22181 .option mailbox_size appendfile string&!! unset
22182 .cindex "mailbox" "specifying size of"
22183 .cindex "size" "of mailbox"
22184 If this option is set, it is expanded, and the result is taken as the current
22185 size the mailbox. It must be a decimal number, optionally followed by K or M.
22186 This provides a way of obtaining this information from an external source that
22187 maintains the data. This is likely to be helpful for maildir deliveries where
22188 it is computationally expensive to compute the size of a mailbox.
22189
22190
22191
22192 .option maildir_format appendfile boolean false
22193 .cindex "maildir format" "specifying"
22194 If this option is set with the &%directory%& option, the delivery is into a new
22195 file, in the &"maildir"& format that is used by other mail software. When the
22196 transport is activated directly from a &(redirect)& router (for example, the
22197 &(address_file)& transport in the default configuration), setting
22198 &%maildir_format%& causes the path received from the router to be treated as a
22199 directory, whether or not it ends with &`/`&. This option is available only if
22200 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
22201 &<<SECTmaildirdelivery>>& below for further details.
22202
22203
22204 .option maildir_quota_directory_regex appendfile string "See below"
22205 .cindex "maildir format" "quota; directories included in"
22206 .cindex "quota" "maildir; directories included in"
22207 This option is relevant only when &%maildir_use_size_file%& is set. It defines
22208 a regular expression for specifying directories, relative to the quota
22209 directory (see &%quota_directory%&), that should be included in the quota
22210 calculation. The default value is:
22211 .code
22212 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
22213 .endd
22214 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
22215 (directories whose names begin with a dot). If you want to exclude the
22216 &_Trash_&
22217 folder from the count (as some sites do), you need to change this setting to
22218 .code
22219 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
22220 .endd
22221 This uses a negative lookahead in the regular expression to exclude the
22222 directory whose name is &_.Trash_&. When a directory is excluded from quota
22223 calculations, quota processing is bypassed for any messages that are delivered
22224 directly into that directory.
22225
22226
22227 .option maildir_retries appendfile integer 10
22228 This option specifies the number of times to retry when writing a file in
22229 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
22230
22231
22232 .option maildir_tag appendfile string&!! unset
22233 This option applies only to deliveries in maildir format, and is described in
22234 section &<<SECTmaildirdelivery>>& below.
22235
22236
22237 .option maildir_use_size_file appendfile&!! boolean false
22238 .cindex "maildir format" "&_maildirsize_& file"
22239 The result of string expansion for this option must be a valid boolean value.
22240 If it is true, it enables support for &_maildirsize_& files. Exim
22241 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
22242 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
22243 value is zero. See &%maildir_quota_directory_regex%& above and section
22244 &<<SECTmaildirdelivery>>& below for further details.
22245
22246 .option maildirfolder_create_regex appendfile string unset
22247 .cindex "maildir format" "&_maildirfolder_& file"
22248 .cindex "&_maildirfolder_&, creating"
22249 The value of this option is a regular expression. If it is unset, it has no
22250 effect. Otherwise, before a maildir delivery takes place, the pattern is
22251 matched against the name of the maildir directory, that is, the directory
22252 containing the &_new_& and &_tmp_& subdirectories that will be used for the
22253 delivery. If there is a match, Exim checks for the existence of a file called
22254 &_maildirfolder_& in the directory, and creates it if it does not exist.
22255 See section &<<SECTmaildirdelivery>>& for more details.
22256
22257
22258 .option mailstore_format appendfile boolean false
22259 .cindex "mailstore format" "specifying"
22260 If this option is set with the &%directory%& option, the delivery is into two
22261 new files in &"mailstore"& format. The option is available only if
22262 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
22263 below for further details.
22264
22265
22266 .option mailstore_prefix appendfile string&!! unset
22267 This option applies only to deliveries in mailstore format, and is described in
22268 section &<<SECTopdir>>& below.
22269
22270
22271 .option mailstore_suffix appendfile string&!! unset
22272 This option applies only to deliveries in mailstore format, and is described in
22273 section &<<SECTopdir>>& below.
22274
22275
22276 .option mbx_format appendfile boolean false
22277 .cindex "locking files"
22278 .cindex "file" "locking"
22279 .cindex "file" "MBX format"
22280 .cindex "MBX format, specifying"
22281 This option is available only if Exim has been compiled with SUPPORT_MBX
22282 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
22283 the message is appended to the mailbox file in MBX format instead of
22284 traditional Unix format. This format is supported by Pine4 and its associated
22285 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
22286
22287 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
22288 automatically changed by the use of &%mbx_format%&. They should normally be set
22289 empty when using MBX format, so this option almost always appears in this
22290 combination:
22291 .code
22292 mbx_format = true
22293 message_prefix =
22294 message_suffix =
22295 .endd
22296 If none of the locking options are mentioned in the configuration,
22297 &%use_mbx_lock%& is assumed and the other locking options default to false. It
22298 is possible to specify the other kinds of locking with &%mbx_format%&, but
22299 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
22300 interworks with &'c-client'&, providing for shared access to the mailbox. It
22301 should not be used if any program that does not use this form of locking is
22302 going to access the mailbox, nor should it be used if the mailbox file is NFS
22303 mounted, because it works only when the mailbox is accessed from a single host.
22304
22305 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
22306 the standard version of &'c-client'&, because as long as it has a mailbox open
22307 (this means for the whole of a Pine or IMAP session), Exim will not be able to
22308 append messages to it.
22309
22310
22311 .option message_prefix appendfile string&!! "see below"
22312 .cindex "&""From""& line"
22313 The string specified here is expanded and output at the start of every message.
22314 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
22315 in which case it is:
22316 .code
22317 message_prefix = "From ${if def:return_path{$return_path}\
22318 {MAILER-DAEMON}} $tod_bsdinbox\n"
22319 .endd
22320 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
22321 &`\n`& to &`\r\n`& in &%message_prefix%&.
22322
22323 .option message_suffix appendfile string&!! "see below"
22324 The string specified here is expanded and output at the end of every message.
22325 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
22326 in which case it is a single newline character. The suffix can be suppressed by
22327 setting
22328 .code
22329 message_suffix =
22330 .endd
22331 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
22332 &`\n`& to &`\r\n`& in &%message_suffix%&.
22333
22334 .option mode appendfile "octal integer" 0600
22335 If the output file is created, it is given this mode. If it already exists and
22336 has wider permissions, they are reduced to this mode. If it has narrower
22337 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
22338 if the delivery is the result of a &%save%& command in a filter file specifying
22339 a particular mode, the mode of the output file is always forced to take that
22340 value, and this option is ignored.
22341
22342
22343 .option mode_fail_narrower appendfile boolean true
22344 This option applies in the case when an existing mailbox file has a narrower
22345 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
22346 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
22347 continues with the delivery attempt, using the existing mode of the file.
22348
22349
22350 .option notify_comsat appendfile boolean false
22351 If this option is true, the &'comsat'& daemon is notified after every
22352 successful delivery to a user mailbox. This is the daemon that notifies logged
22353 on users about incoming mail.
22354
22355
22356 .option quota appendfile string&!! unset
22357 .cindex "quota" "imposed by Exim"
22358 This option imposes a limit on the size of the file to which Exim is appending,
22359 or to the total space used in the directory tree when the &%directory%& option
22360 is set. In the latter case, computation of the space used is expensive, because
22361 all the files in the directory (and any sub-directories) have to be
22362 individually inspected and their sizes summed. (See &%quota_size_regex%& and
22363 &%maildir_use_size_file%& for ways to avoid this in environments where users
22364 have no shell access to their mailboxes).
22365
22366 As there is no interlock against two simultaneous deliveries into a
22367 multi-file mailbox, it is possible for the quota to be overrun in this case.
22368 For single-file mailboxes, of course, an interlock is a necessity.
22369
22370 A file's size is taken as its &'used'& value. Because of blocking effects, this
22371 may be a lot less than the actual amount of disk space allocated to the file.
22372 If the sizes of a number of files are being added up, the rounding effect can
22373 become quite noticeable, especially on systems that have large block sizes.
22374 Nevertheless, it seems best to stick to the &'used'& figure, because this is
22375 the obvious value which users understand most easily.
22376
22377 The value of the option is expanded, and must then be a numerical value
22378 (decimal point allowed), optionally followed by one of the letters K, M, or G,
22379 for kilobytes, megabytes, or gigabytes, optionally followed by a slash
22380 and further option modifiers. If Exim is running on a system with
22381 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
22382 be handled.
22383
22384 The option modifier &%no_check%& can be used to force delivery even if the over
22385 quota condition is met. The quota gets updated as usual.
22386
22387 &*Note*&: A value of zero is interpreted as &"no quota"&.
22388
22389 The expansion happens while Exim is running as root, before it changes uid for
22390 the delivery. This means that files that are inaccessible to the end user can
22391 be used to hold quota values that are looked up in the expansion. When delivery
22392 fails because this quota is exceeded, the handling of the error is as for
22393 system quota failures.
22394
22395 By default, Exim's quota checking mimics system quotas, and restricts the
22396 mailbox to the specified maximum size, though the value is not accurate to the
22397 last byte, owing to separator lines and additional headers that may get added
22398 during message delivery. When a mailbox is nearly full, large messages may get
22399 refused even though small ones are accepted, because the size of the current
22400 message is added to the quota when the check is made. This behaviour can be
22401 changed by setting &%quota_is_inclusive%& false. When this is done, the check
22402 for exceeding the quota does not include the current message. Thus, deliveries
22403 continue until the quota has been exceeded; thereafter, no further messages are
22404 delivered. See also &%quota_warn_threshold%&.
22405
22406
22407 .option quota_directory appendfile string&!! unset
22408 This option defines the directory to check for quota purposes when delivering
22409 into individual files. The default is the delivery directory, or, if a file
22410 called &_maildirfolder_& exists in a maildir directory, the parent of the
22411 delivery directory.
22412
22413
22414 .option quota_filecount appendfile string&!! 0
22415 This option applies when the &%directory%& option is set. It limits the total
22416 number of files in the directory (compare the inode limit in system quotas). It
22417 can only be used if &%quota%& is also set. The value is expanded; an expansion
22418 failure causes delivery to be deferred. A value of zero is interpreted as
22419 &"no quota"&.
22420
22421 The option modifier &%no_check%& can be used to force delivery even if the over
22422 quota condition is met. The quota gets updated as usual.
22423
22424 .option quota_is_inclusive appendfile boolean true
22425 See &%quota%& above.
22426
22427
22428 .option quota_size_regex appendfile string unset
22429 This option applies when one of the delivery modes that writes a separate file
22430 for each message is being used. When Exim wants to find the size of one of
22431 these files in order to test the quota, it first checks &%quota_size_regex%&.
22432 If this is set to a regular expression that matches the file name, and it
22433 captures one string, that string is interpreted as a representation of the
22434 file's size. The value of &%quota_size_regex%& is not expanded.
22435
22436 This feature is useful only when users have no shell access to their mailboxes
22437 &-- otherwise they could defeat the quota simply by renaming the files. This
22438 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
22439 the file length to the file name. For example:
22440 .code
22441 maildir_tag = ,S=$message_size
22442 quota_size_regex = ,S=(\d+)
22443 .endd
22444 An alternative to &$message_size$& is &$message_linecount$&, which contains the
22445 number of lines in the message.
22446
22447 The regular expression should not assume that the length is at the end of the
22448 file name (even though &%maildir_tag%& puts it there) because maildir MUAs
22449 sometimes add other information onto the ends of message file names.
22450
22451 Section &<<SECID136>>& contains further information.
22452
22453
22454 .option quota_warn_message appendfile string&!! "see below"
22455 See below for the use of this option. If it is not set when
22456 &%quota_warn_threshold%& is set, it defaults to
22457 .code
22458 quota_warn_message = "\
22459 To: $local_part@$domain\n\
22460 Subject: Your mailbox\n\n\
22461 This message is automatically created \
22462 by mail delivery software.\n\n\
22463 The size of your mailbox has exceeded \
22464 a warning threshold that is\n\
22465 set by the system administrator.\n"
22466 .endd
22467
22468
22469 .option quota_warn_threshold appendfile string&!! 0
22470 .cindex "quota" "warning threshold"
22471 .cindex "mailbox" "size warning"
22472 .cindex "size" "of mailbox"
22473 This option is expanded in the same way as &%quota%& (see above). If the
22474 resulting value is greater than zero, and delivery of the message causes the
22475 size of the file or total space in the directory tree to cross the given
22476 threshold, a warning message is sent. If &%quota%& is also set, the threshold
22477 may be specified as a percentage of it by following the value with a percent
22478 sign. For example:
22479 .code
22480 quota = 10M
22481 quota_warn_threshold = 75%
22482 .endd
22483 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
22484 percent sign is ignored.
22485
22486 The warning message itself is specified by the &%quota_warn_message%& option,
22487 and it must start with a &'To:'& header line containing the recipient(s) of the
22488 warning message. These do not necessarily have to include the recipient(s) of
22489 the original message. A &'Subject:'& line should also normally be supplied. You
22490 can include any other header lines that you want. If you do not include a
22491 &'From:'& line, the default is:
22492 .code
22493 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
22494 .endd
22495 .oindex &%errors_reply_to%&
22496 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
22497 option.
22498
22499 The &%quota%& option does not have to be set in order to use this option; they
22500 are independent of one another except when the threshold is specified as a
22501 percentage.
22502
22503
22504 .option use_bsmtp appendfile boolean false
22505 .cindex "envelope sender"
22506 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
22507 format, with the envelope sender and recipient(s) included as SMTP commands. If
22508 you want to include a leading HELO command with such messages, you can do
22509 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
22510 for details of batch SMTP.
22511
22512
22513 .option use_crlf appendfile boolean false
22514 .cindex "carriage return"
22515 .cindex "linefeed"
22516 This option causes lines to be terminated with the two-character CRLF sequence
22517 (carriage return, linefeed) instead of just a linefeed character. In the case
22518 of batched SMTP, the byte sequence written to the file is then an exact image
22519 of what would be sent down a real SMTP connection.
22520
22521 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
22522 (which are used to supply the traditional &"From&~"& and blank line separators
22523 in Berkeley-style mailboxes) are written verbatim, so must contain their own
22524 carriage return characters if these are needed. In cases where these options
22525 have non-empty defaults, the values end with a single linefeed, so they must be
22526 changed to end with &`\r\n`& if &%use_crlf%& is set.
22527
22528
22529 .option use_fcntl_lock appendfile boolean "see below"
22530 This option controls the use of the &[fcntl()]& function to lock a file for
22531 exclusive use when a message is being appended. It is set by default unless
22532 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
22533 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
22534 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
22535
22536
22537 .option use_flock_lock appendfile boolean false
22538 This option is provided to support the use of &[flock()]& for file locking, for
22539 the few situations where it is needed. Most modern operating systems support
22540 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
22541 each other. Exim uses &[fcntl()]& locking by default.
22542
22543 This option is required only if you are using an operating system where
22544 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
22545 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
22546 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
22547
22548 .cindex "Solaris" "&[flock()]& support"
22549 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
22550 have it (and some, I think, provide a not quite right version built on top of
22551 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
22552 the ability to use it, and any attempt to do so will cause a configuration
22553 error.
22554
22555 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
22556 is just being mapped onto &[fcntl()]& by the OS).
22557
22558
22559 .option use_lockfile appendfile boolean "see below"
22560 If this option is turned off, Exim does not attempt to create a lock file when
22561 appending to a mailbox file. In this situation, the only locking is by
22562 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
22563 sure that every MUA that is ever going to look at your users' mailboxes uses
22564 &[fcntl()]& rather than a lock file, and even then only when you are not
22565 delivering over NFS from more than one host.
22566
22567 .cindex "NFS" "lock file"
22568 In order to append to an NFS file safely from more than one host, it is
22569 necessary to take out a lock &'before'& opening the file, and the lock file
22570 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
22571 file corruption.
22572
22573 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
22574 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
22575 except when &%mbx_format%& is set.
22576
22577
22578 .option use_mbx_lock appendfile boolean "see below"
22579 This option is available only if Exim has been compiled with SUPPORT_MBX
22580 set in &_Local/Makefile_&. Setting the option specifies that special MBX
22581 locking rules be used. It is set by default if &%mbx_format%& is set and none
22582 of the locking options are mentioned in the configuration. The locking rules
22583 are the same as are used by the &'c-client'& library that underlies Pine and
22584 the IMAP4 and POP daemons that come with it (see the discussion below). The
22585 rules allow for shared access to the mailbox. However, this kind of locking
22586 does not work when the mailbox is NFS mounted.
22587
22588 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
22589 &%use_flock_lock%& to control what kind of locking is used in implementing the
22590 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
22591 without &%use_fcntl_lock%& or &%use_flock_lock%&.
22592
22593
22594
22595
22596 .section "Operational details for appending" "SECTopappend"
22597 .cindex "appending to a file"
22598 .cindex "file" "appending"
22599 Before appending to a file, the following preparations are made:
22600
22601 .ilist
22602 If the name of the file is &_/dev/null_&, no action is taken, and a success
22603 return is given.
22604
22605 .next
22606 .cindex "directory creation"
22607 If any directories on the file's path are missing, Exim creates them if the
22608 &%create_directory%& option is set. A created directory's mode is given by the
22609 &%directory_mode%& option.
22610
22611 .next
22612 If &%file_format%& is set, the format of an existing file is checked. If this
22613 indicates that a different transport should be used, control is passed to that
22614 transport.
22615
22616 .next
22617 .cindex "file" "locking"
22618 .cindex "locking files"
22619 .cindex "NFS" "lock file"
22620 If &%use_lockfile%& is set, a lock file is built in a way that will work
22621 reliably over NFS, as follows:
22622
22623 .olist
22624 Create a &"hitching post"& file whose name is that of the lock file with the
22625 current time, primary host name, and process id added, by opening for writing
22626 as a new file. If this fails with an access error, delivery is deferred.
22627 .next
22628 Close the hitching post file, and hard link it to the lock file name.
22629 .next
22630 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
22631 Unlink the hitching post name.
22632 .next
22633 Otherwise, use &[stat()]& to get information about the hitching post file, and
22634 then unlink hitching post name. If the number of links is exactly two, creation
22635 of the lock file succeeded but something (for example, an NFS server crash and
22636 restart) caused this fact not to be communicated to the &[link()]& call.
22637 .next
22638 If creation of the lock file failed, wait for &%lock_interval%& and try again,
22639 up to &%lock_retries%& times. However, since any program that writes to a
22640 mailbox should complete its task very quickly, it is reasonable to time out old
22641 lock files that are normally the result of user agent and system crashes. If an
22642 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
22643 it before trying again.
22644 .endlist olist
22645
22646 .next
22647 A call is made to &[lstat()]& to discover whether the main file exists, and if
22648 so, what its characteristics are. If &[lstat()]& fails for any reason other
22649 than non-existence, delivery is deferred.
22650
22651 .next
22652 .cindex "symbolic link" "to mailbox"
22653 .cindex "mailbox" "symbolic link"
22654 If the file does exist and is a symbolic link, delivery is deferred, unless the
22655 &%allow_symlink%& option is set, in which case the ownership of the link is
22656 checked, and then &[stat()]& is called to find out about the real file, which
22657 is then subjected to the checks below. The check on the top-level link
22658 ownership prevents one user creating a link for another's mailbox in a sticky
22659 directory, though allowing symbolic links in this case is definitely not a good
22660 idea. If there is a chain of symbolic links, the intermediate ones are not
22661 checked.
22662
22663 .next
22664 If the file already exists but is not a regular file, or if the file's owner
22665 and group (if the group is being checked &-- see &%check_group%& above) are
22666 different from the user and group under which the delivery is running,
22667 delivery is deferred.
22668
22669 .next
22670 If the file's permissions are more generous than specified, they are reduced.
22671 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
22672 is set false, in which case the delivery is tried using the existing
22673 permissions.
22674
22675 .next
22676 The file's inode number is saved, and the file is then opened for appending.
22677 If this fails because the file has vanished, &(appendfile)& behaves as if it
22678 hadn't existed (see below). For any other failures, delivery is deferred.
22679
22680 .next
22681 If the file is opened successfully, check that the inode number hasn't
22682 changed, that it is still a regular file, and that the owner and permissions
22683 have not changed. If anything is wrong, defer delivery and freeze the message.
22684
22685 .next
22686 If the file did not exist originally, defer delivery if the &%file_must_exist%&
22687 option is set. Otherwise, check that the file is being created in a permitted
22688 directory if the &%create_file%& option is set (deferring on failure), and then
22689 open for writing as a new file, with the O_EXCL and O_CREAT options,
22690 except when dealing with a symbolic link (the &%allow_symlink%& option must be
22691 set). In this case, which can happen if the link points to a non-existent file,
22692 the file is opened for writing using O_CREAT but not O_EXCL, because
22693 that prevents link following.
22694
22695 .next
22696 .cindex "loop" "while file testing"
22697 If opening fails because the file exists, obey the tests given above for
22698 existing files. However, to avoid looping in a situation where the file is
22699 being continuously created and destroyed, the exists/not-exists loop is broken
22700 after 10 repetitions, and the message is then frozen.
22701
22702 .next
22703 If opening fails with any other error, defer delivery.
22704
22705 .next
22706 .cindex "file" "locking"
22707 .cindex "locking files"
22708 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
22709 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
22710 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
22711 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
22712 file, and an exclusive lock on the file whose name is
22713 .code
22714 /tmp/.<device-number>.<inode-number>
22715 .endd
22716 using the device and inode numbers of the open mailbox file, in accordance with
22717 the MBX locking rules. This file is created with a mode that is specified by
22718 the &%lockfile_mode%& option.
22719
22720 If Exim fails to lock the file, there are two possible courses of action,
22721 depending on the value of the locking timeout. This is obtained from
22722 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
22723
22724 If the timeout value is zero, the file is closed, Exim waits for
22725 &%lock_interval%&, and then goes back and re-opens the file as above and tries
22726 to lock it again. This happens up to &%lock_retries%& times, after which the
22727 delivery is deferred.
22728
22729 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
22730 &[flock()]& are used (with the given timeout), so there has already been some
22731 waiting involved by the time locking fails. Nevertheless, Exim does not give up
22732 immediately. It retries up to
22733 .code
22734 (lock_retries * lock_interval) / <timeout>
22735 .endd
22736 times (rounded up).
22737 .endlist
22738
22739 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
22740 and/or &[flock()]& locks) and then deletes the lock file if one was created.
22741
22742
22743 .section "Operational details for delivery to a new file" "SECTopdir"
22744 .cindex "delivery" "to single file"
22745 .cindex "&""From""& line"
22746 When the &%directory%& option is set instead of &%file%&, each message is
22747 delivered into a newly-created file or set of files. When &(appendfile)& is
22748 activated directly from a &(redirect)& router, neither &%file%& nor
22749 &%directory%& is normally set, because the path for delivery is supplied by the
22750 router. (See for example, the &(address_file)& transport in the default
22751 configuration.) In this case, delivery is to a new file if either the path name
22752 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
22753
22754 No locking is required while writing the message to a new file, so the various
22755 locking options of the transport are ignored. The &"From"& line that by default
22756 separates messages in a single file is not normally needed, nor is the escaping
22757 of message lines that start with &"From"&, and there is no need to ensure a
22758 newline at the end of each message. Consequently, the default values for
22759 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
22760 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
22761
22762 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
22763 the files in the delivery directory by default. However, you can specify a
22764 different directory by setting &%quota_directory%&. Also, for maildir
22765 deliveries (see below) the &_maildirfolder_& convention is honoured.
22766
22767
22768 .cindex "maildir format"
22769 .cindex "mailstore format"
22770 There are three different ways in which delivery to individual files can be
22771 done, controlled by the settings of the &%maildir_format%& and
22772 &%mailstore_format%& options. Note that code to support maildir or mailstore
22773 formats is not included in the binary unless SUPPORT_MAILDIR or
22774 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
22775
22776 .cindex "directory creation"
22777 In all three cases an attempt is made to create the directory and any necessary
22778 sub-directories if they do not exist, provided that the &%create_directory%&
22779 option is set (the default). The location of a created directory can be
22780 constrained by setting &%create_file%&. A created directory's mode is given by
22781 the &%directory_mode%& option. If creation fails, or if the
22782 &%create_directory%& option is not set when creation is required, delivery is
22783 deferred.
22784
22785
22786
22787 .section "Maildir delivery" "SECTmaildirdelivery"
22788 .cindex "maildir format" "description of"
22789 If the &%maildir_format%& option is true, Exim delivers each message by writing
22790 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
22791 directory that is defined by the &%directory%& option (the &"delivery
22792 directory"&). If the delivery is successful, the file is renamed into the
22793 &_new_& subdirectory.
22794
22795 In the file name, <&'stime'&> is the current time of day in seconds, and
22796 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
22797 Exim checks that the time-of-day clock has moved on by at least one microsecond
22798 before terminating the delivery process. This guarantees uniqueness for the
22799 file name. However, as a precaution, Exim calls &[stat()]& for the file before
22800 opening it. If any response other than ENOENT (does not exist) is given,
22801 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
22802
22803 Before Exim carries out a maildir delivery, it ensures that subdirectories
22804 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
22805 do not exist, Exim tries to create them and any superior directories in their
22806 path, subject to the &%create_directory%& and &%create_file%& options. If the
22807 &%maildirfolder_create_regex%& option is set, and the regular expression it
22808 contains matches the delivery directory, Exim also ensures that a file called
22809 &_maildirfolder_& exists in the delivery directory. If a missing directory or
22810 &_maildirfolder_& file cannot be created, delivery is deferred.
22811
22812 These features make it possible to use Exim to create all the necessary files
22813 and directories in a maildir mailbox, including subdirectories for maildir++
22814 folders. Consider this example:
22815 .code
22816 maildir_format = true
22817 directory = /var/mail/$local_part\
22818 ${if eq{$local_part_suffix}{}{}\
22819 {/.${substr_1:$local_part_suffix}}}
22820 maildirfolder_create_regex = /\.[^/]+$
22821 .endd
22822 If &$local_part_suffix$& is empty (there was no suffix for the local part),
22823 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
22824 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
22825 not match this name, so Exim will not look for or create the file
22826 &_/var/mail/pimbo/maildirfolder_&, though it will create
22827 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
22828
22829 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
22830 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
22831 does match &%maildirfolder_create_regex%&. In this case, Exim will create
22832 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
22833 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
22834
22835 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
22836 not inadvertently match the toplevel maildir directory, because a
22837 &_maildirfolder_& file at top level would completely break quota calculations.
22838
22839 .cindex "quota" "in maildir delivery"
22840 .cindex "maildir++"
22841 If Exim is required to check a &%quota%& setting before a maildir delivery, and
22842 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
22843 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
22844 Exim assumes the directory is a maildir++ folder directory, which is one level
22845 down from the user's top level mailbox directory. This causes it to start at
22846 the parent directory instead of the current directory when calculating the
22847 amount of space used.
22848
22849 One problem with delivering into a multi-file mailbox is that it is
22850 computationally expensive to compute the size of the mailbox for quota
22851 checking. Various approaches have been taken to reduce the amount of work
22852 needed. The next two sections describe two of them. A third alternative is to
22853 use some external process for maintaining the size data, and use the expansion
22854 of the &%mailbox_size%& option as a way of importing it into Exim.
22855
22856
22857
22858
22859 .section "Using tags to record message sizes" "SECID135"
22860 If &%maildir_tag%& is set, the string is expanded for each delivery.
22861 When the maildir file is renamed into the &_new_& sub-directory, the
22862 tag is added to its name. However, if adding the tag takes the length of the
22863 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
22864 the tag is dropped and the maildir file is created with no tag.
22865
22866
22867 .vindex "&$message_size$&"
22868 Tags can be used to encode the size of files in their names; see
22869 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
22870 happens after the message has been written. The value of the &$message_size$&
22871 variable is set to the number of bytes actually written. If the expansion is
22872 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
22873 be deferred. The expanded tag may contain any printing characters except &"/"&.
22874 Non-printing characters in the string are ignored; if the resulting string is
22875 empty, it is ignored. If it starts with an alphanumeric character, a leading
22876 colon is inserted; this default has not proven to be the path that popular
22877 maildir implementations have chosen (but changing it in Exim would break
22878 backwards compatibility).
22879
22880 For one common implementation, you might set:
22881 .code
22882 maildir_tag = ,S=${message_size}
22883 .endd
22884 but you should check the documentation of the other software to be sure.
22885
22886 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
22887 as this allows Exim to extract the size from your tag, instead of having to
22888 &[stat()]& each message file.
22889
22890
22891 .section "Using a maildirsize file" "SECID136"
22892 .cindex "quota" "in maildir delivery"
22893 .cindex "maildir format" "&_maildirsize_& file"
22894 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
22895 storing quota and message size information in a file called &_maildirsize_&
22896 within the toplevel maildir directory. If this file does not exist, Exim
22897 creates it, setting the quota from the &%quota%& option of the transport. If
22898 the maildir directory itself does not exist, it is created before any attempt
22899 to write a &_maildirsize_& file.
22900
22901 The &_maildirsize_& file is used to hold information about the sizes of
22902 messages in the maildir, thus speeding up quota calculations. The quota value
22903 in the file is just a cache; if the quota is changed in the transport, the new
22904 value overrides the cached value when the next message is delivered. The cache
22905 is maintained for the benefit of other programs that access the maildir and
22906 need to know the quota.
22907
22908 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
22909 file is maintained (with a zero quota setting), but no quota is imposed.
22910
22911 A regular expression is available for controlling which directories in the
22912 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
22913 See the description of the &%maildir_quota_directory_regex%& option above for
22914 details.
22915
22916
22917 .section "Mailstore delivery" "SECID137"
22918 .cindex "mailstore format" "description of"
22919 If the &%mailstore_format%& option is true, each message is written as two
22920 files in the given directory. A unique base name is constructed from the
22921 message id and the current delivery process, and the files that are written use
22922 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
22923 contains the message's envelope, and the &_.msg_& file contains the message
22924 itself. The base name is placed in the variable &$mailstore_basename$&.
22925
22926 During delivery, the envelope is first written to a file with the suffix
22927 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
22928 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
22929 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
22930 file before accessing either of them. An alternative approach is to wait for
22931 the absence of a &_.tmp_& file.
22932
22933 The envelope file starts with any text defined by the &%mailstore_prefix%&
22934 option, expanded and terminated by a newline if there isn't one. Then follows
22935 the sender address on one line, then all the recipient addresses, one per line.
22936 There can be more than one recipient only if the &%batch_max%& option is set
22937 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
22938 appended to the file, followed by a newline if it does not end with one.
22939
22940 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
22941 failure, it is ignored. Other expansion errors are treated as serious
22942 configuration errors, and delivery is deferred. The variable
22943 &$mailstore_basename$& is available for use during these expansions.
22944
22945
22946 .section "Non-special new file delivery" "SECID138"
22947 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
22948 file is created directly in the named directory. For example, when delivering
22949 messages into files in batched SMTP format for later delivery to some host (see
22950 section &<<SECTbatchSMTP>>&), a setting such as
22951 .code
22952 directory = /var/bsmtp/$host
22953 .endd
22954 might be used. A message is written to a file with a temporary name, which is
22955 then renamed when the delivery is complete. The final name is obtained by
22956 expanding the contents of the &%directory_file%& option.
22957 .ecindex IIDapptra1
22958 .ecindex IIDapptra2
22959
22960
22961
22962
22963
22964
22965 . ////////////////////////////////////////////////////////////////////////////
22966 . ////////////////////////////////////////////////////////////////////////////
22967
22968 .chapter "The autoreply transport" "CHID8"
22969 .scindex IIDauttra1 "transports" "&(autoreply)&"
22970 .scindex IIDauttra2 "&(autoreply)& transport"
22971 The &(autoreply)& transport is not a true transport in that it does not cause
22972 the message to be transmitted. Instead, it generates a new mail message as an
22973 automatic reply to the incoming message. &'References:'& and
22974 &'Auto-Submitted:'& header lines are included. These are constructed according
22975 to the rules in RFCs 2822 and 3834, respectively.
22976
22977 If the router that passes the message to this transport does not have the
22978 &%unseen%& option set, the original message (for the current recipient) is not
22979 delivered anywhere. However, when the &%unseen%& option is set on the router
22980 that passes the message to this transport, routing of the address continues, so
22981 another router can set up a normal message delivery.
22982
22983
22984 The &(autoreply)& transport is usually run as the result of mail filtering, a
22985 &"vacation"& message being the standard example. However, it can also be run
22986 directly from a router like any other transport. To reduce the possibility of
22987 message cascades, messages created by the &(autoreply)& transport always have
22988 empty envelope sender addresses, like bounce messages.
22989
22990 The parameters of the message to be sent can be specified in the configuration
22991 by options described below. However, these are used only when the address
22992 passed to the transport does not contain its own reply information. When the
22993 transport is run as a consequence of a
22994 &%mail%&
22995 or &%vacation%& command in a filter file, the parameters of the message are
22996 supplied by the filter, and passed with the address. The transport's options
22997 that define the message are then ignored (so they are not usually set in this
22998 case). The message is specified entirely by the filter or by the transport; it
22999 is never built from a mixture of options. However, the &%file_optional%&,
23000 &%mode%&, and &%return_message%& options apply in all cases.
23001
23002 &(Autoreply)& is implemented as a local transport. When used as a result of a
23003 command in a user's filter file, &(autoreply)& normally runs under the uid and
23004 gid of the user, and with appropriate current and home directories (see chapter
23005 &<<CHAPenvironment>>&).
23006
23007 There is a subtle difference between routing a message to a &(pipe)& transport
23008 that generates some text to be returned to the sender, and routing it to an
23009 &(autoreply)& transport. This difference is noticeable only if more than one
23010 address from the same message is so handled. In the case of a pipe, the
23011 separate outputs from the different addresses are gathered up and returned to
23012 the sender in a single message, whereas if &(autoreply)& is used, a separate
23013 message is generated for each address that is passed to it.
23014
23015 Non-printing characters are not permitted in the header lines generated for the
23016 message that &(autoreply)& creates, with the exception of newlines that are
23017 immediately followed by white space. If any non-printing characters are found,
23018 the transport defers.
23019 Whether characters with the top bit set count as printing characters or not is
23020 controlled by the &%print_topbitchars%& global option.
23021
23022 If any of the generic options for manipulating headers (for example,
23023 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
23024 of the original message that is included in the generated message when
23025 &%return_message%& is set. They do not apply to the generated message itself.
23026
23027 .vindex "&$sender_address$&"
23028 If the &(autoreply)& transport receives return code 2 from Exim when it submits
23029 the message, indicating that there were no recipients, it does not treat this
23030 as an error. This means that autoreplies sent to &$sender_address$& when this
23031 is empty (because the incoming message is a bounce message) do not cause
23032 problems. They are just discarded.
23033
23034
23035
23036 .section "Private options for autoreply" "SECID139"
23037 .cindex "options" "&(autoreply)& transport"
23038
23039 .option bcc autoreply string&!! unset
23040 This specifies the addresses that are to receive &"blind carbon copies"& of the
23041 message when the message is specified by the transport.
23042
23043
23044 .option cc autoreply string&!! unset
23045 This specifies recipients of the message and the contents of the &'Cc:'& header
23046 when the message is specified by the transport.
23047
23048
23049 .option file autoreply string&!! unset
23050 The contents of the file are sent as the body of the message when the message
23051 is specified by the transport. If both &%file%& and &%text%& are set, the text
23052 string comes first.
23053
23054
23055 .option file_expand autoreply boolean false
23056 If this is set, the contents of the file named by the &%file%& option are
23057 subjected to string expansion as they are added to the message.
23058
23059
23060 .option file_optional autoreply boolean false
23061 If this option is true, no error is generated if the file named by the &%file%&
23062 option or passed with the address does not exist or cannot be read.
23063
23064
23065 .option from autoreply string&!! unset
23066 This specifies the contents of the &'From:'& header when the message is
23067 specified by the transport.
23068
23069
23070 .option headers autoreply string&!! unset
23071 This specifies additional RFC 2822 headers that are to be added to the message
23072 when the message is specified by the transport. Several can be given by using
23073 &"\n"& to separate them. There is no check on the format.
23074
23075
23076 .option log autoreply string&!! unset
23077 This option names a file in which a record of every message sent is logged when
23078 the message is specified by the transport.
23079
23080
23081 .option mode autoreply "octal integer" 0600
23082 If either the log file or the &"once"& file has to be created, this mode is
23083 used.
23084
23085
23086 .option never_mail autoreply "address list&!!" unset
23087 If any run of the transport creates a message with a recipient that matches any
23088 item in the list, that recipient is quietly discarded. If all recipients are
23089 discarded, no message is created. This applies both when the recipients are
23090 generated by a filter and when they are specified in the transport.
23091
23092
23093
23094 .option once autoreply string&!! unset
23095 This option names a file or DBM database in which a record of each &'To:'&
23096 recipient is kept when the message is specified by the transport. &*Note*&:
23097 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
23098
23099 If &%once%& is unset, or is set to an empty string, the message is always sent.
23100 By default, if &%once%& is set to a non-empty file name, the message
23101 is not sent if a potential recipient is already listed in the database.
23102 However, if the &%once_repeat%& option specifies a time greater than zero, the
23103 message is sent if that much time has elapsed since a message was last sent to
23104 this recipient. A setting of zero time for &%once_repeat%& (the default)
23105 prevents a message from being sent a second time &-- in this case, zero means
23106 infinity.
23107
23108 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
23109 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
23110 greater than zero, it changes the way Exim implements the &%once%& option.
23111 Instead of using a DBM file to record every recipient it sends to, it uses a
23112 regular file, whose size will never get larger than the given value.
23113
23114 In the file, Exim keeps a linear list of recipient addresses and the times at
23115 which they were sent messages. If the file is full when a new address needs to
23116 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
23117 means that a given recipient may receive multiple messages, but at
23118 unpredictable intervals that depend on the rate of turnover of addresses in the
23119 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
23120
23121
23122 .option once_file_size autoreply integer 0
23123 See &%once%& above.
23124
23125
23126 .option once_repeat autoreply time&!! 0s
23127 See &%once%& above.
23128 After expansion, the value of this option must be a valid time value.
23129
23130
23131 .option reply_to autoreply string&!! unset
23132 This specifies the contents of the &'Reply-To:'& header when the message is
23133 specified by the transport.
23134
23135
23136 .option return_message autoreply boolean false
23137 If this is set, a copy of the original message is returned with the new
23138 message, subject to the maximum size set in the &%return_size_limit%& global
23139 configuration option.
23140
23141
23142 .option subject autoreply string&!! unset
23143 This specifies the contents of the &'Subject:'& header when the message is
23144 specified by the transport. It is tempting to quote the original subject in
23145 automatic responses. For example:
23146 .code
23147 subject = Re: $h_subject:
23148 .endd
23149 There is a danger in doing this, however. It may allow a third party to
23150 subscribe your users to an opt-in mailing list, provided that the list accepts
23151 bounce messages as subscription confirmations. Well-managed lists require a
23152 non-bounce message to confirm a subscription, so the danger is relatively
23153 small.
23154
23155
23156
23157 .option text autoreply string&!! unset
23158 This specifies a single string to be used as the body of the message when the
23159 message is specified by the transport. If both &%text%& and &%file%& are set,
23160 the text comes first.
23161
23162
23163 .option to autoreply string&!! unset
23164 This specifies recipients of the message and the contents of the &'To:'& header
23165 when the message is specified by the transport.
23166 .ecindex IIDauttra1
23167 .ecindex IIDauttra2
23168
23169
23170
23171
23172 . ////////////////////////////////////////////////////////////////////////////
23173 . ////////////////////////////////////////////////////////////////////////////
23174
23175 .chapter "The lmtp transport" "CHAPLMTP"
23176 .cindex "transports" "&(lmtp)&"
23177 .cindex "&(lmtp)& transport"
23178 .cindex "LMTP" "over a pipe"
23179 .cindex "LMTP" "over a socket"
23180 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
23181 specified command
23182 or by interacting with a Unix domain socket.
23183 This transport is something of a cross between the &(pipe)& and &(smtp)&
23184 transports. Exim also has support for using LMTP over TCP/IP; this is
23185 implemented as an option for the &(smtp)& transport. Because LMTP is expected
23186 to be of minority interest, the default build-time configure in &_src/EDITME_&
23187 has it commented out. You need to ensure that
23188 .code
23189 TRANSPORT_LMTP=yes
23190 .endd
23191 .cindex "options" "&(lmtp)& transport"
23192 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
23193 included in the Exim binary. The private options of the &(lmtp)& transport are
23194 as follows:
23195
23196 .option batch_id lmtp string&!! unset
23197 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23198
23199
23200 .option batch_max lmtp integer 1
23201 This limits the number of addresses that can be handled in a single delivery.
23202 Most LMTP servers can handle several addresses at once, so it is normally a
23203 good idea to increase this value. See the description of local delivery
23204 batching in chapter &<<CHAPbatching>>&.
23205
23206
23207 .option command lmtp string&!! unset
23208 This option must be set if &%socket%& is not set. The string is a command which
23209 is run in a separate process. It is split up into a command name and list of
23210 arguments, each of which is separately expanded (so expansion cannot change the
23211 number of arguments). The command is run directly, not via a shell. The message
23212 is passed to the new process using the standard input and output to operate the
23213 LMTP protocol.
23214
23215 .option ignore_quota lmtp boolean false
23216 .cindex "LMTP" "ignoring quota errors"
23217 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
23218 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
23219 in its response to the LHLO command.
23220
23221 .option socket lmtp string&!! unset
23222 This option must be set if &%command%& is not set. The result of expansion must
23223 be the name of a Unix domain socket. The transport connects to the socket and
23224 delivers the message to it using the LMTP protocol.
23225
23226
23227 .option timeout lmtp time 5m
23228 The transport is aborted if the created process or Unix domain socket does not
23229 respond to LMTP commands or message input within this timeout. Delivery
23230 is deferred, and will be tried again later. Here is an example of a typical
23231 LMTP transport:
23232 .code
23233 lmtp:
23234 driver = lmtp
23235 command = /some/local/lmtp/delivery/program
23236 batch_max = 20
23237 user = exim
23238 .endd
23239 This delivers up to 20 addresses at a time, in a mixture of domains if
23240 necessary, running as the user &'exim'&.
23241
23242
23243
23244 . ////////////////////////////////////////////////////////////////////////////
23245 . ////////////////////////////////////////////////////////////////////////////
23246
23247 .chapter "The pipe transport" "CHAPpipetransport"
23248 .scindex IIDpiptra1 "transports" "&(pipe)&"
23249 .scindex IIDpiptra2 "&(pipe)& transport"
23250 The &(pipe)& transport is used to deliver messages via a pipe to a command
23251 running in another process. One example is the use of &(pipe)& as a
23252 pseudo-remote transport for passing messages to some other delivery mechanism
23253 (such as UUCP). Another is the use by individual users to automatically process
23254 their incoming messages. The &(pipe)& transport can be used in one of the
23255 following ways:
23256
23257 .ilist
23258 .vindex "&$local_part$&"
23259 A router routes one address to a transport in the normal way, and the
23260 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
23261 contains the local part of the address (as usual), and the command that is run
23262 is specified by the &%command%& option on the transport.
23263 .next
23264 .vindex "&$pipe_addresses$&"
23265 If the &%batch_max%& option is set greater than 1 (the default is 1), the
23266 transport can handle more than one address in a single run. In this case, when
23267 more than one address is routed to the transport, &$local_part$& is not set
23268 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
23269 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
23270 that are routed to the transport.
23271 .next
23272 .vindex "&$address_pipe$&"
23273 A router redirects an address directly to a pipe command (for example, from an
23274 alias or forward file). In this case, &$address_pipe$& contains the text of the
23275 pipe command, and the &%command%& option on the transport is ignored unless
23276 &%force_command%& is set. If only one address is being transported
23277 (&%batch_max%& is not greater than one, or only one address was redirected to
23278 this pipe command), &$local_part$& contains the local part that was redirected.
23279 .endlist
23280
23281
23282 The &(pipe)& transport is a non-interactive delivery method. Exim can also
23283 deliver messages over pipes using the LMTP interactive protocol. This is
23284 implemented by the &(lmtp)& transport.
23285
23286 In the case when &(pipe)& is run as a consequence of an entry in a local user's
23287 &_.forward_& file, the command runs under the uid and gid of that user. In
23288 other cases, the uid and gid have to be specified explicitly, either on the
23289 transport or on the router that handles the address. Current and &"home"&
23290 directories are also controllable. See chapter &<<CHAPenvironment>>& for
23291 details of the local delivery environment and chapter &<<CHAPbatching>>&
23292 for a discussion of local delivery batching.
23293
23294
23295 .section "Concurrent delivery" "SECID140"
23296 If two messages arrive at almost the same time, and both are routed to a pipe
23297 delivery, the two pipe transports may be run concurrently. You must ensure that
23298 any pipe commands you set up are robust against this happening. If the commands
23299 write to a file, the &%exim_lock%& utility might be of use.
23300 Alternatively the &%max_parallel%& option could be used with a value
23301 of "1" to enforce serialization.
23302
23303
23304
23305
23306 .section "Returned status and data" "SECID141"
23307 .cindex "&(pipe)& transport" "returned data"
23308 If the command exits with a non-zero return code, the delivery is deemed to
23309 have failed, unless either the &%ignore_status%& option is set (in which case
23310 the return code is treated as zero), or the return code is one of those listed
23311 in the &%temp_errors%& option, which are interpreted as meaning &"try again
23312 later"&. In this case, delivery is deferred. Details of a permanent failure are
23313 logged, but are not included in the bounce message, which merely contains
23314 &"local delivery failed"&.
23315
23316 If the command exits on a signal and the &%freeze_signal%& option is set then
23317 the message will be frozen in the queue. If that option is not set, a bounce
23318 will be sent as normal.
23319
23320 If the return code is greater than 128 and the command being run is a shell
23321 script, it normally means that the script was terminated by a signal whose
23322 value is the return code minus 128. The &%freeze_signal%& option does not
23323 apply in this case.
23324
23325 If Exim is unable to run the command (that is, if &[execve()]& fails), the
23326 return code is set to 127. This is the value that a shell returns if it is
23327 asked to run a non-existent command. The wording for the log line suggests that
23328 a non-existent command may be the problem.
23329
23330 The &%return_output%& option can affect the result of a pipe delivery. If it is
23331 set and the command produces any output on its standard output or standard
23332 error streams, the command is considered to have failed, even if it gave a zero
23333 return code or if &%ignore_status%& is set. The output from the command is
23334 included as part of the bounce message. The &%return_fail_output%& option is
23335 similar, except that output is returned only when the command exits with a
23336 failure return code, that is, a value other than zero or a code that matches
23337 &%temp_errors%&.
23338
23339
23340
23341 .section "How the command is run" "SECThowcommandrun"
23342 .cindex "&(pipe)& transport" "path for command"
23343 The command line is (by default) broken down into a command name and arguments
23344 by the &(pipe)& transport itself. The &%allow_commands%& and
23345 &%restrict_to_path%& options can be used to restrict the commands that may be
23346 run.
23347
23348 .cindex "quoting" "in pipe command"
23349 Unquoted arguments are delimited by white space. If an argument appears in
23350 double quotes, backslash is interpreted as an escape character in the usual
23351 way. If an argument appears in single quotes, no escaping is done.
23352
23353 String expansion is applied to the command line except when it comes from a
23354 traditional &_.forward_& file (commands from a filter file are expanded). The
23355 expansion is applied to each argument in turn rather than to the whole line.
23356 For this reason, any string expansion item that contains white space must be
23357 quoted so as to be contained within a single argument. A setting such as
23358 .code
23359 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
23360 .endd
23361 will not work, because the expansion item gets split between several
23362 arguments. You have to write
23363 .code
23364 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
23365 .endd
23366 to ensure that it is all in one argument. The expansion is done in this way,
23367 argument by argument, so that the number of arguments cannot be changed as a
23368 result of expansion, and quotes or backslashes in inserted variables do not
23369 interact with external quoting. However, this leads to problems if you want to
23370 generate multiple arguments (or the command name plus arguments) from a single
23371 expansion. In this situation, the simplest solution is to use a shell. For
23372 example:
23373 .code
23374 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
23375 .endd
23376
23377 .cindex "transport" "filter"
23378 .cindex "filter" "transport filter"
23379 .vindex "&$pipe_addresses$&"
23380 Special handling takes place when an argument consists of precisely the text
23381 &`$pipe_addresses`&. This is not a general expansion variable; the only
23382 place this string is recognized is when it appears as an argument for a pipe or
23383 transport filter command. It causes each address that is being handled to be
23384 inserted in the argument list at that point &'as a separate argument'&. This
23385 avoids any problems with spaces or shell metacharacters, and is of use when a
23386 &(pipe)& transport is handling groups of addresses in a batch.
23387
23388 If &%force_command%& is enabled on the transport, Special handling takes place
23389 for an argument that consists of precisely the text &`$address_pipe`&. It
23390 is handled similarly to &$pipe_addresses$& above. It is expanded and each
23391 argument is inserted in the argument list at that point
23392 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
23393 the only item in the argument; in fact, if it were then &%force_command%&
23394 should behave as a no-op. Rather, it should be used to adjust the command
23395 run while preserving the argument vector separation.
23396
23397 After splitting up into arguments and expansion, the resulting command is run
23398 in a subprocess directly from the transport, &'not'& under a shell. The
23399 message that is being delivered is supplied on the standard input, and the
23400 standard output and standard error are both connected to a single pipe that is
23401 read by Exim. The &%max_output%& option controls how much output the command
23402 may produce, and the &%return_output%& and &%return_fail_output%& options
23403 control what is done with it.
23404
23405 Not running the command under a shell (by default) lessens the security risks
23406 in cases when a command from a user's filter file is built out of data that was
23407 taken from an incoming message. If a shell is required, it can of course be
23408 explicitly specified as the command to be run. However, there are circumstances
23409 where existing commands (for example, in &_.forward_& files) expect to be run
23410 under a shell and cannot easily be modified. To allow for these cases, there is
23411 an option called &%use_shell%&, which changes the way the &(pipe)& transport
23412 works. Instead of breaking up the command line as just described, it expands it
23413 as a single string and passes the result to &_/bin/sh_&. The
23414 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
23415 with &%use_shell%&, and the whole mechanism is inherently less secure.
23416
23417
23418
23419 .section "Environment variables" "SECTpipeenv"
23420 .cindex "&(pipe)& transport" "environment for command"
23421 .cindex "environment" "&(pipe)& transport"
23422 The environment variables listed below are set up when the command is invoked.
23423 This list is a compromise for maximum compatibility with other MTAs. Note that
23424 the &%environment%& option can be used to add additional variables to this
23425 environment. The environment for the &(pipe)& transport is not subject
23426 to the &%add_environment%& and &%keep_environment%& main config options.
23427 .display
23428 &`DOMAIN `& the domain of the address
23429 &`HOME `& the home directory, if set
23430 &`HOST `& the host name when called from a router (see below)
23431 &`LOCAL_PART `& see below
23432 &`LOCAL_PART_PREFIX `& see below
23433 &`LOCAL_PART_SUFFIX `& see below
23434 &`LOGNAME `& see below
23435 &`MESSAGE_ID `& Exim's local ID for the message
23436 &`PATH `& as specified by the &%path%& option below
23437 &`QUALIFY_DOMAIN `& the sender qualification domain
23438 &`RECIPIENT `& the complete recipient address
23439 &`SENDER `& the sender of the message (empty if a bounce)
23440 &`SHELL `& &`/bin/sh`&
23441 &`TZ `& the value of the &%timezone%& option, if set
23442 &`USER `& see below
23443 .endd
23444 When a &(pipe)& transport is called directly from (for example) an &(accept)&
23445 router, LOCAL_PART is set to the local part of the address. When it is
23446 called as a result of a forward or alias expansion, LOCAL_PART is set to
23447 the local part of the address that was expanded. In both cases, any affixes are
23448 removed from the local part, and made available in LOCAL_PART_PREFIX and
23449 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
23450 same value as LOCAL_PART for compatibility with other MTAs.
23451
23452 .cindex "HOST"
23453 HOST is set only when a &(pipe)& transport is called from a router that
23454 associates hosts with an address, typically when using &(pipe)& as a
23455 pseudo-remote transport. HOST is set to the first host name specified by
23456 the router.
23457
23458 .cindex "HOME"
23459 If the transport's generic &%home_directory%& option is set, its value is used
23460 for the HOME environment variable. Otherwise, a home directory may be set
23461 by the router's &%transport_home_directory%& option, which defaults to the
23462 user's home directory if &%check_local_user%& is set.
23463
23464
23465 .section "Private options for pipe" "SECID142"
23466 .cindex "options" "&(pipe)& transport"
23467
23468
23469
23470 .option allow_commands pipe "string list&!!" unset
23471 .cindex "&(pipe)& transport" "permitted commands"
23472 The string is expanded, and is then interpreted as a colon-separated list of
23473 permitted commands. If &%restrict_to_path%& is not set, the only commands
23474 permitted are those in the &%allow_commands%& list. They need not be absolute
23475 paths; the &%path%& option is still used for relative paths. If
23476 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
23477 in the &%allow_commands%& list, or a name without any slashes that is found on
23478 the path. In other words, if neither &%allow_commands%& nor
23479 &%restrict_to_path%& is set, there is no restriction on the command, but
23480 otherwise only commands that are permitted by one or the other are allowed. For
23481 example, if
23482 .code
23483 allow_commands = /usr/bin/vacation
23484 .endd
23485 and &%restrict_to_path%& is not set, the only permitted command is
23486 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
23487 &%use_shell%& is set.
23488
23489
23490 .option batch_id pipe string&!! unset
23491 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23492
23493
23494 .option batch_max pipe integer 1
23495 This limits the number of addresses that can be handled in a single delivery.
23496 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23497
23498
23499 .option check_string pipe string unset
23500 As &(pipe)& writes the message, the start of each line is tested for matching
23501 &%check_string%&, and if it does, the initial matching characters are replaced
23502 by the contents of &%escape_string%&, provided both are set. The value of
23503 &%check_string%& is a literal string, not a regular expression, and the case of
23504 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
23505 of &%check_string%& and &%escape_string%& are forced to values that implement
23506 the SMTP escaping protocol. Any settings made in the configuration file are
23507 ignored.
23508
23509
23510 .option command pipe string&!! unset
23511 This option need not be set when &(pipe)& is being used to deliver to pipes
23512 obtained directly from address redirections. In other cases, the option must be
23513 set, to provide a command to be run. It need not yield an absolute path (see
23514 the &%path%& option below). The command is split up into separate arguments by
23515 Exim, and each argument is separately expanded, as described in section
23516 &<<SECThowcommandrun>>& above.
23517
23518
23519 .option environment pipe string&!! unset
23520 .cindex "&(pipe)& transport" "environment for command"
23521 .cindex "environment" "&(pipe)& transport"
23522 This option is used to add additional variables to the environment in which the
23523 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
23524 a string which is expanded, and then interpreted as a colon-separated list of
23525 environment settings of the form <&'name'&>=<&'value'&>.
23526
23527
23528 .option escape_string pipe string unset
23529 See &%check_string%& above.
23530
23531
23532 .option freeze_exec_fail pipe boolean false
23533 .cindex "exec failure"
23534 .cindex "failure of exec"
23535 .cindex "&(pipe)& transport" "failure of exec"
23536 Failure to exec the command in a pipe transport is by default treated like
23537 any other failure while running the command. However, if &%freeze_exec_fail%&
23538 is set, failure to exec is treated specially, and causes the message to be
23539 frozen, whatever the setting of &%ignore_status%&.
23540
23541
23542 .option freeze_signal pipe boolean false
23543 .cindex "signal exit"
23544 .cindex "&(pipe)& transport", "signal exit"
23545 Normally if the process run by a command in a pipe transport exits on a signal,
23546 a bounce message is sent. If &%freeze_signal%& is set, the message will be
23547 frozen in Exim's queue instead.
23548
23549
23550 .option force_command pipe boolean false
23551 .cindex "force command"
23552 .cindex "&(pipe)& transport", "force command"
23553 Normally when a router redirects an address directly to a pipe command
23554 the &%command%& option on the transport is ignored. If &%force_command%&
23555 is set, the &%command%& option will used. This is especially
23556 useful for forcing a wrapper or additional argument to be added to the
23557 command. For example:
23558 .code
23559 command = /usr/bin/remote_exec myhost -- $address_pipe
23560 force_command
23561 .endd
23562
23563 Note that &$address_pipe$& is handled specially in &%command%& when
23564 &%force_command%& is set, expanding out to the original argument vector as
23565 separate items, similarly to a Unix shell &`"$@"`& construct.
23566
23567
23568 .option ignore_status pipe boolean false
23569 If this option is true, the status returned by the subprocess that is set up to
23570 run the command is ignored, and Exim behaves as if zero had been returned.
23571 Otherwise, a non-zero status or termination by signal causes an error return
23572 from the transport unless the status value is one of those listed in
23573 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
23574
23575 &*Note*&: This option does not apply to timeouts, which do not return a status.
23576 See the &%timeout_defer%& option for how timeouts are handled.
23577
23578
23579 .option log_defer_output pipe boolean false
23580 .cindex "&(pipe)& transport" "logging output"
23581 If this option is set, and the status returned by the command is
23582 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
23583 and any output was produced on stdout or stderr, the first line of it is
23584 written to the main log.
23585
23586
23587 .option log_fail_output pipe boolean false
23588 If this option is set, and the command returns any output on stdout or
23589 stderr, and also ends with a return code that is neither zero nor one of
23590 the return codes listed in &%temp_errors%& (that is, the delivery
23591 failed), the first line of output is written to the main log. This
23592 option and &%log_output%& are mutually exclusive. Only one of them may
23593 be set.
23594
23595
23596 .option log_output pipe boolean false
23597 If this option is set and the command returns any output on stdout or
23598 stderr, the first line of output is written to the main log, whatever
23599 the return code. This option and &%log_fail_output%& are mutually
23600 exclusive. Only one of them may be set.
23601
23602
23603 .option max_output pipe integer 20K
23604 This specifies the maximum amount of output that the command may produce on its
23605 standard output and standard error file combined. If the limit is exceeded, the
23606 process running the command is killed. This is intended as a safety measure to
23607 catch runaway processes. The limit is applied independently of the settings of
23608 the options that control what is done with such output (for example,
23609 &%return_output%&). Because of buffering effects, the amount of output may
23610 exceed the limit by a small amount before Exim notices.
23611
23612
23613 .option message_prefix pipe string&!! "see below"
23614 The string specified here is expanded and output at the start of every message.
23615 The default is unset if &%use_bsmtp%& is set. Otherwise it is
23616 .code
23617 message_prefix = \
23618 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
23619 ${tod_bsdinbox}\n
23620 .endd
23621 .cindex "Cyrus"
23622 .cindex "&%tmail%&"
23623 .cindex "&""From""& line"
23624 This is required by the commonly used &_/usr/bin/vacation_& program.
23625 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
23626 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
23627 setting
23628 .code
23629 message_prefix =
23630 .endd
23631 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23632 &`\n`& to &`\r\n`& in &%message_prefix%&.
23633
23634
23635 .option message_suffix pipe string&!! "see below"
23636 The string specified here is expanded and output at the end of every message.
23637 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
23638 The suffix can be suppressed by setting
23639 .code
23640 message_suffix =
23641 .endd
23642 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23643 &`\n`& to &`\r\n`& in &%message_suffix%&.
23644
23645
23646 .option path pipe string&!! "/bin:/usr/bin"
23647 This option is expanded and
23648 specifies the string that is set up in the PATH environment
23649 variable of the subprocess.
23650 If the &%command%& option does not yield an absolute path name, the command is
23651 sought in the PATH directories, in the usual way. &*Warning*&: This does not
23652 apply to a command specified as a transport filter.
23653
23654
23655 .option permit_coredump pipe boolean false
23656 Normally Exim inhibits core-dumps during delivery. If you have a need to get
23657 a core-dump of a pipe command, enable this command. This enables core-dumps
23658 during delivery and affects both the Exim binary and the pipe command run.
23659 It is recommended that this option remain off unless and until you have a need
23660 for it and that this only be enabled when needed, as the risk of excessive
23661 resource consumption can be quite high. Note also that Exim is typically
23662 installed as a setuid binary and most operating systems will inhibit coredumps
23663 of these by default, so further OS-specific action may be required.
23664
23665
23666 .option pipe_as_creator pipe boolean false
23667 .cindex "uid (user id)" "local delivery"
23668 If the generic &%user%& option is not set and this option is true, the delivery
23669 process is run under the uid that was in force when Exim was originally called
23670 to accept the message. If the group id is not otherwise set (via the generic
23671 &%group%& option), the gid that was in force when Exim was originally called to
23672 accept the message is used.
23673
23674
23675 .option restrict_to_path pipe boolean false
23676 When this option is set, any command name not listed in &%allow_commands%& must
23677 contain no slashes. The command is searched for only in the directories listed
23678 in the &%path%& option. This option is intended for use in the case when a pipe
23679 command has been generated from a user's &_.forward_& file. This is usually
23680 handled by a &(pipe)& transport called &%address_pipe%&.
23681
23682
23683 .option return_fail_output pipe boolean false
23684 If this option is true, and the command produced any output and ended with a
23685 return code other than zero or one of the codes listed in &%temp_errors%& (that
23686 is, the delivery failed), the output is returned in the bounce message.
23687 However, if the message has a null sender (that is, it is itself a bounce
23688 message), output from the command is discarded. This option and
23689 &%return_output%& are mutually exclusive. Only one of them may be set.
23690
23691
23692
23693 .option return_output pipe boolean false
23694 If this option is true, and the command produced any output, the delivery is
23695 deemed to have failed whatever the return code from the command, and the output
23696 is returned in the bounce message. Otherwise, the output is just discarded.
23697 However, if the message has a null sender (that is, it is a bounce message),
23698 output from the command is always discarded, whatever the setting of this
23699 option. This option and &%return_fail_output%& are mutually exclusive. Only one
23700 of them may be set.
23701
23702
23703
23704 .option temp_errors pipe "string list" "see below"
23705 .cindex "&(pipe)& transport" "temporary failure"
23706 This option contains either a colon-separated list of numbers, or a single
23707 asterisk. If &%ignore_status%& is false
23708 and &%return_output%& is not set,
23709 and the command exits with a non-zero return code, the failure is treated as
23710 temporary and the delivery is deferred if the return code matches one of the
23711 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
23712 codes are treated as permanent errors. The default setting contains the codes
23713 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
23714 compiled on a system that does not define these macros, it assumes values of 75
23715 and 73, respectively.
23716
23717
23718 .option timeout pipe time 1h
23719 If the command fails to complete within this time, it is killed. This normally
23720 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
23721 specifies no timeout. In order to ensure that any subprocesses created by the
23722 command are also killed, Exim makes the initial process a process group leader,
23723 and kills the whole process group on a timeout. However, this can be defeated
23724 if one of the processes starts a new process group.
23725
23726 .option timeout_defer pipe boolean false
23727 A timeout in a &(pipe)& transport, either in the command that the transport
23728 runs, or in a transport filter that is associated with it, is by default
23729 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
23730 is set true, both kinds of timeout become temporary errors, causing the
23731 delivery to be deferred.
23732
23733 .option umask pipe "octal integer" 022
23734 This specifies the umask setting for the subprocess that runs the command.
23735
23736
23737 .option use_bsmtp pipe boolean false
23738 .cindex "envelope sender"
23739 If this option is set true, the &(pipe)& transport writes messages in &"batch
23740 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
23741 commands. If you want to include a leading HELO command with such messages,
23742 you can do so by setting the &%message_prefix%& option. See section
23743 &<<SECTbatchSMTP>>& for details of batch SMTP.
23744
23745 .option use_classresources pipe boolean false
23746 .cindex "class resources (BSD)"
23747 This option is available only when Exim is running on FreeBSD, NetBSD, or
23748 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
23749 resource limits when a &(pipe)& transport is run to perform a delivery. The
23750 limits for the uid under which the pipe is to run are obtained from the login
23751 class database.
23752
23753
23754 .option use_crlf pipe boolean false
23755 .cindex "carriage return"
23756 .cindex "linefeed"
23757 This option causes lines to be terminated with the two-character CRLF sequence
23758 (carriage return, linefeed) instead of just a linefeed character. In the case
23759 of batched SMTP, the byte sequence written to the pipe is then an exact image
23760 of what would be sent down a real SMTP connection.
23761
23762 The contents of the &%message_prefix%& and &%message_suffix%& options are
23763 written verbatim, so must contain their own carriage return characters if these
23764 are needed. When &%use_bsmtp%& is not set, the default values for both
23765 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
23766 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
23767
23768
23769 .option use_shell pipe boolean false
23770 .vindex "&$pipe_addresses$&"
23771 If this option is set, it causes the command to be passed to &_/bin/sh_&
23772 instead of being run directly from the transport, as described in section
23773 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
23774 where the command is expected to be run under a shell and cannot easily be
23775 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
23776 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
23777 command is expanded as a single string, and handed to &_/bin/sh_& as data for
23778 its &%-c%& option.
23779
23780
23781
23782 .section "Using an external local delivery agent" "SECID143"
23783 .cindex "local delivery" "using an external agent"
23784 .cindex "&'procmail'&"
23785 .cindex "external local delivery"
23786 .cindex "delivery" "&'procmail'&"
23787 .cindex "delivery" "by external agent"
23788 The &(pipe)& transport can be used to pass all messages that require local
23789 delivery to a separate local delivery agent such as &%procmail%&. When doing
23790 this, care must be taken to ensure that the pipe is run under an appropriate
23791 uid and gid. In some configurations one wants this to be a uid that is trusted
23792 by the delivery agent to supply the correct sender of the message. It may be
23793 necessary to recompile or reconfigure the delivery agent so that it trusts an
23794 appropriate user. The following is an example transport and router
23795 configuration for &%procmail%&:
23796 .code
23797 # transport
23798 procmail_pipe:
23799 driver = pipe
23800 command = /usr/local/bin/procmail -d $local_part
23801 return_path_add
23802 delivery_date_add
23803 envelope_to_add
23804 check_string = "From "
23805 escape_string = ">From "
23806 umask = 077
23807 user = $local_part
23808 group = mail
23809
23810 # router
23811 procmail:
23812 driver = accept
23813 check_local_user
23814 transport = procmail_pipe
23815 .endd
23816 In this example, the pipe is run as the local user, but with the group set to
23817 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
23818 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
23819 user to supply a correct sender address. If you do not specify either a
23820 &%group%& or a &%user%& option, the pipe command is run as the local user. The
23821 home directory is the user's home directory by default.
23822
23823 &*Note*&: The command that the pipe transport runs does &'not'& begin with
23824 .code
23825 IFS=" "
23826 .endd
23827 as shown in some &%procmail%& documentation, because Exim does not by default
23828 use a shell to run pipe commands.
23829
23830 .cindex "Cyrus"
23831 The next example shows a transport and a router for a system where local
23832 deliveries are handled by the Cyrus IMAP server.
23833 .code
23834 # transport
23835 local_delivery_cyrus:
23836 driver = pipe
23837 command = /usr/cyrus/bin/deliver \
23838 -m ${substr_1:$local_part_suffix} -- $local_part
23839 user = cyrus
23840 group = mail
23841 return_output
23842 log_output
23843 message_prefix =
23844 message_suffix =
23845
23846 # router
23847 local_user_cyrus:
23848 driver = accept
23849 check_local_user
23850 local_part_suffix = .*
23851 transport = local_delivery_cyrus
23852 .endd
23853 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
23854 &%return_output%& to cause any text written by Cyrus to be returned to the
23855 sender.
23856 .ecindex IIDpiptra1
23857 .ecindex IIDpiptra2
23858
23859
23860 . ////////////////////////////////////////////////////////////////////////////
23861 . ////////////////////////////////////////////////////////////////////////////
23862
23863 .chapter "The smtp transport" "CHAPsmtptrans"
23864 .scindex IIDsmttra1 "transports" "&(smtp)&"
23865 .scindex IIDsmttra2 "&(smtp)& transport"
23866 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
23867 or LMTP protocol. The list of hosts to try can either be taken from the address
23868 that is being processed (having been set up by the router), or specified
23869 explicitly for the transport. Timeout and retry processing (see chapter
23870 &<<CHAPretry>>&) is applied to each IP address independently.
23871
23872
23873 .section "Multiple messages on a single connection" "SECID144"
23874 The sending of multiple messages over a single TCP/IP connection can arise in
23875 two ways:
23876
23877 .ilist
23878 If a message contains more than &%max_rcpt%& (see below) addresses that are
23879 routed to the same host, more than one copy of the message has to be sent to
23880 that host. In this situation, multiple copies may be sent in a single run of
23881 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
23882 does when it has too many addresses to send in one message also depends on the
23883 value of the global &%remote_max_parallel%& option. Details are given in
23884 section &<<SECToutSMTPTCP>>&.)
23885 .next
23886 .cindex "hints database" "remembering routing"
23887 When a message has been successfully delivered over a TCP/IP connection, Exim
23888 looks in its hints database to see if there are any other messages awaiting a
23889 connection to the same host. If there are, a new delivery process is started
23890 for one of them, and the current TCP/IP connection is passed on to it. The new
23891 process may in turn send multiple copies and possibly create yet another
23892 process.
23893 .endlist
23894
23895
23896 For each copy sent over the same TCP/IP connection, a sequence counter is
23897 incremented, and if it ever gets to the value of &%connection_max_messages%&,
23898 no further messages are sent over that connection.
23899
23900
23901
23902 .section "Use of the $host and $host_address variables" "SECID145"
23903 .vindex "&$host$&"
23904 .vindex "&$host_address$&"
23905 At the start of a run of the &(smtp)& transport, the values of &$host$& and
23906 &$host_address$& are the name and IP address of the first host on the host list
23907 passed by the router. However, when the transport is about to connect to a
23908 specific host, and while it is connected to that host, &$host$& and
23909 &$host_address$& are set to the values for that host. These are the values
23910 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
23911 &%serialize_hosts%&, and the various TLS options are expanded.
23912
23913
23914 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
23915 .vindex &$tls_bits$&
23916 .vindex &$tls_cipher$&
23917 .vindex &$tls_peerdn$&
23918 .vindex &$tls_sni$&
23919 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
23920 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
23921 are the values that were set when the message was received.
23922 These are the values that are used for options that are expanded before any
23923 SMTP connections are made. Just before each connection is made, these four
23924 variables are emptied. If TLS is subsequently started, they are set to the
23925 appropriate values for the outgoing connection, and these are the values that
23926 are in force when any authenticators are run and when the
23927 &%authenticated_sender%& option is expanded.
23928
23929 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
23930 and will be removed in a future release.
23931
23932
23933 .section "Private options for smtp" "SECID146"
23934 .cindex "options" "&(smtp)& transport"
23935 The private options of the &(smtp)& transport are as follows:
23936
23937
23938 .option address_retry_include_sender smtp boolean true
23939 .cindex "4&'xx'& responses" "retrying after"
23940 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
23941 is the combination of sender and recipient that is delayed in subsequent queue
23942 runs until the retry time is reached. You can delay the recipient without
23943 reference to the sender (which is what earlier versions of Exim did), by
23944 setting &%address_retry_include_sender%& false. However, this can lead to
23945 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
23946
23947 .option allow_localhost smtp boolean false
23948 .cindex "local host" "sending to"
23949 .cindex "fallback" "hosts specified on transport"
23950 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
23951 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
23952 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
23953 the delivery anyway. This should be used only in special cases when the
23954 configuration ensures that no looping will result (for example, a differently
23955 configured Exim is listening on the port to which the message is sent).
23956
23957
23958 .option authenticated_sender smtp string&!! unset
23959 .cindex "Cyrus"
23960 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
23961 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
23962 overriding any existing authenticated sender value. If the string expansion is
23963 forced to fail, the option is ignored. Other expansion failures cause delivery
23964 to be deferred. If the result of expansion is an empty string, that is also
23965 ignored.
23966
23967 The expansion happens after the outgoing connection has been made and TLS
23968 started, if required. This means that the &$host$&, &$host_address$&,
23969 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
23970 particular connection.
23971
23972 If the SMTP session is not authenticated, the expansion of
23973 &%authenticated_sender%& still happens (and can cause the delivery to be
23974 deferred if it fails), but no AUTH= item is added to MAIL commands
23975 unless &%authenticated_sender_force%& is true.
23976
23977 This option allows you to use the &(smtp)& transport in LMTP mode to
23978 deliver mail to Cyrus IMAP and provide the proper local part as the
23979 &"authenticated sender"&, via a setting such as:
23980 .code
23981 authenticated_sender = $local_part
23982 .endd
23983 This removes the need for IMAP subfolders to be assigned special ACLs to
23984 allow direct delivery to those subfolders.
23985
23986 Because of expected uses such as that just described for Cyrus (when no
23987 domain is involved), there is no checking on the syntax of the provided
23988 value.
23989
23990
23991 .option authenticated_sender_force smtp boolean false
23992 If this option is set true, the &%authenticated_sender%& option's value
23993 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
23994 authenticated as a client.
23995
23996
23997 .option command_timeout smtp time 5m
23998 This sets a timeout for receiving a response to an SMTP command that has been
23999 sent out. It is also used when waiting for the initial banner line from the
24000 remote host. Its value must not be zero.
24001
24002
24003 .option connect_timeout smtp time 5m
24004 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
24005 to a remote host. A setting of zero allows the system timeout (typically
24006 several minutes) to act. To have any effect, the value of this option must be
24007 less than the system timeout. However, it has been observed that on some
24008 systems there is no system timeout, which is why the default value for this
24009 option is 5 minutes, a value recommended by RFC 1123.
24010
24011
24012 .option connection_max_messages smtp integer 500
24013 .cindex "SMTP" "passed connection"
24014 .cindex "SMTP" "multiple deliveries"
24015 .cindex "multiple SMTP deliveries"
24016 This controls the maximum number of separate message deliveries that are sent
24017 over a single TCP/IP connection. If the value is zero, there is no limit.
24018 For testing purposes, this value can be overridden by the &%-oB%& command line
24019 option.
24020
24021
24022 .option dane_require_tls_ciphers smtp string&!! unset
24023 .cindex "TLS" "requiring specific ciphers for DANE"
24024 .cindex "cipher" "requiring specific"
24025 .cindex DANE "TLS ciphers"
24026 This option may be used to override &%tls_require_ciphers%& for connections
24027 where DANE has been determined to be in effect.
24028 If not set, then &%tls_require_ciphers%& will be used.
24029 Normal SMTP delivery is not able to make strong demands of TLS cipher
24030 configuration, because delivery will fall back to plaintext. Once DANE has
24031 been determined to be in effect, there is no plaintext fallback and making the
24032 TLS cipherlist configuration stronger will increase security, rather than
24033 counter-intuitively decreasing it.
24034 If the option expands to be empty or is forced to fail, then it will
24035 be treated as unset and &%tls_require_ciphers%& will be used instead.
24036
24037
24038 .option data_timeout smtp time 5m
24039 This sets a timeout for the transmission of each block in the data portion of
24040 the message. As a result, the overall timeout for a message depends on the size
24041 of the message. Its value must not be zero. See also &%final_timeout%&.
24042
24043
24044 .option dkim_canon smtp string&!! unset
24045 .option dkim_domain smtp string list&!! unset
24046 .option dkim_hash smtp string&!! sha256
24047 .option dkim_identity smtp string&!! unset
24048 .option dkim_private_key smtp string&!! unset
24049 .option dkim_selector smtp string&!! unset
24050 .option dkim_strict smtp string&!! unset
24051 .option dkim_sign_headers smtp string&!! "per RFC"
24052 .option dkim_timestamps smtp string&!! unset
24053 DKIM signing options. For details see section &<<SECDKIMSIGN>>&.
24054
24055
24056 .option delay_after_cutoff smtp boolean true
24057 This option controls what happens when all remote IP addresses for a given
24058 domain have been inaccessible for so long that they have passed their retry
24059 cutoff times.
24060
24061 In the default state, if the next retry time has not been reached for any of
24062 them, the address is bounced without trying any deliveries. In other words,
24063 Exim delays retrying an IP address after the final cutoff time until a new
24064 retry time is reached, and can therefore bounce an address without ever trying
24065 a delivery, when machines have been down for a long time. Some people are
24066 unhappy at this prospect, so...
24067
24068 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
24069 addresses are past their final cutoff time, Exim tries to deliver to those
24070 IP addresses that have not been tried since the message arrived. If there are
24071 none, of if they all fail, the address is bounced. In other words, it does not
24072 delay when a new message arrives, but immediately tries those expired IP
24073 addresses that haven't been tried since the message arrived. If there is a
24074 continuous stream of messages for the dead hosts, unsetting
24075 &%delay_after_cutoff%& means that there will be many more attempts to deliver
24076 to them.
24077
24078
24079 .option dns_qualify_single smtp boolean true
24080 If the &%hosts%& or &%fallback_hosts%& option is being used,
24081 and the &%gethostbyname%& option is false,
24082 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
24083 in chapter &<<CHAPdnslookup>>& for more details.
24084
24085
24086 .option dns_search_parents smtp boolean false
24087 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
24088 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
24089 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
24090 details.
24091
24092
24093 .option dnssec_request_domains smtp "domain list&!!" unset
24094 .cindex "MX record" "security"
24095 .cindex "DNSSEC" "MX lookup"
24096 .cindex "security" "MX lookup"
24097 .cindex "DNS" "DNSSEC"
24098 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
24099 the dnssec request bit set.
24100 This applies to all of the SRV, MX, AAAA, A lookup sequence.
24101
24102
24103
24104 .option dnssec_require_domains smtp "domain list&!!" unset
24105 .cindex "MX record" "security"
24106 .cindex "DNSSEC" "MX lookup"
24107 .cindex "security" "MX lookup"
24108 .cindex "DNS" "DNSSEC"
24109 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
24110 the dnssec request bit set. Any returns not having the Authenticated Data bit
24111 (AD bit) set will be ignored and logged as a host-lookup failure.
24112 This applies to all of the SRV, MX, AAAA, A lookup sequence.
24113
24114
24115
24116 .option dscp smtp string&!! unset
24117 .cindex "DCSP" "outbound"
24118 This option causes the DSCP value associated with a socket to be set to one
24119 of a number of fixed strings or to numeric value.
24120 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
24121 Common values include &`throughput`&, &`mincost`&, and on newer systems
24122 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
24123
24124 The outbound packets from Exim will be marked with this value in the header
24125 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
24126 that these values will have any effect, not be stripped by networking
24127 equipment, or do much of anything without cooperation with your Network
24128 Engineer and those of all network operators between the source and destination.
24129
24130
24131 .option fallback_hosts smtp "string list" unset
24132 .cindex "fallback" "hosts specified on transport"
24133 String expansion is not applied to this option. The argument must be a
24134 colon-separated list of host names or IP addresses, optionally also including
24135 port numbers, though the separator can be changed, as described in section
24136 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
24137 item in a &%route_list%& setting for the &(manualroute)& router, as described
24138 in section &<<SECTformatonehostitem>>&.
24139
24140 Fallback hosts can also be specified on routers, which associate them with the
24141 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
24142 &%fallback_hosts%& specified on the transport is used only if the address does
24143 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
24144 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
24145 However, &%hosts_randomize%& does apply to fallback host lists.
24146
24147 If Exim is unable to deliver to any of the hosts for a particular address, and
24148 the errors are not permanent rejections, the address is put on a separate
24149 transport queue with its host list replaced by the fallback hosts, unless the
24150 address was routed via MX records and the current host was in the original MX
24151 list. In that situation, the fallback host list is not used.
24152
24153 Once normal deliveries are complete, the fallback queue is delivered by
24154 re-running the same transports with the new host lists. If several failing
24155 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
24156 copy of the message is sent.
24157
24158 The resolution of the host names on the fallback list is controlled by the
24159 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
24160 both to cases when the host list comes with the address and when it is taken
24161 from &%hosts%&. This option provides a &"use a smart host only if delivery
24162 fails"& facility.
24163
24164
24165 .option final_timeout smtp time 10m
24166 This is the timeout that applies while waiting for the response to the final
24167 line containing just &"."& that terminates a message. Its value must not be
24168 zero.
24169
24170 .option gethostbyname smtp boolean false
24171 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
24172 being used, names are looked up using &[gethostbyname()]&
24173 (or &[getipnodebyname()]& when available)
24174 instead of using the DNS. Of course, that function may in fact use the DNS, but
24175 it may also consult other sources of information such as &_/etc/hosts_&.
24176
24177 .option gnutls_compat_mode smtp boolean unset
24178 This option controls whether GnuTLS is used in compatibility mode in an Exim
24179 server. This reduces security slightly, but improves interworking with older
24180 implementations of TLS.
24181
24182 .option helo_data smtp string&!! "see below"
24183 .cindex "HELO" "argument, setting"
24184 .cindex "EHLO" "argument, setting"
24185 .cindex "LHLO argument setting"
24186 The value of this option is expanded after a connection to a another host has
24187 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
24188 command that starts the outgoing SMTP or LMTP session. The default value of the
24189 option is:
24190 .code
24191 $primary_hostname
24192 .endd
24193 During the expansion, the variables &$host$& and &$host_address$& are set to
24194 the identity of the remote host, and the variables &$sending_ip_address$& and
24195 &$sending_port$& are set to the local IP address and port number that are being
24196 used. These variables can be used to generate different values for different
24197 servers or different local IP addresses. For example, if you want the string
24198 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
24199 interface address, you could use this:
24200 .code
24201 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
24202 {$primary_hostname}}
24203 .endd
24204 The use of &%helo_data%& applies both to sending messages and when doing
24205 callouts.
24206
24207 .option hosts smtp "string list&!!" unset
24208 Hosts are associated with an address by a router such as &(dnslookup)&, which
24209 finds the hosts by looking up the address domain in the DNS, or by
24210 &(manualroute)&, which has lists of hosts in its configuration. However,
24211 email addresses can be passed to the &(smtp)& transport by any router, and not
24212 all of them can provide an associated list of hosts.
24213
24214 The &%hosts%& option specifies a list of hosts to be used if the address being
24215 processed does not have any hosts associated with it. The hosts specified by
24216 &%hosts%& are also used, whether or not the address has its own hosts, if
24217 &%hosts_override%& is set.
24218
24219 The string is first expanded, before being interpreted as a colon-separated
24220 list of host names or IP addresses, possibly including port numbers. The
24221 separator may be changed to something other than colon, as described in section
24222 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
24223 item in a &%route_list%& setting for the &(manualroute)& router, as described
24224 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
24225 of the &(manualroute)& router is not available here.
24226
24227 If the expansion fails, delivery is deferred. Unless the failure was caused by
24228 the inability to complete a lookup, the error is logged to the panic log as
24229 well as the main log. Host names are looked up either by searching directly for
24230 address records in the DNS or by calling &[gethostbyname()]& (or
24231 &[getipnodebyname()]& when available), depending on the setting of the
24232 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
24233 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
24234 address are used.
24235
24236 During delivery, the hosts are tried in order, subject to their retry status,
24237 unless &%hosts_randomize%& is set.
24238
24239
24240 .option hosts_avoid_esmtp smtp "host list&!!" unset
24241 .cindex "ESMTP, avoiding use of"
24242 .cindex "HELO" "forcing use of"
24243 .cindex "EHLO" "avoiding use of"
24244 .cindex "PIPELINING" "avoiding the use of"
24245 This option is for use with broken hosts that announce ESMTP facilities (for
24246 example, PIPELINING) and then fail to implement them properly. When a host
24247 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
24248 start of the SMTP session. This means that it cannot use any of the ESMTP
24249 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
24250
24251
24252 .option hosts_avoid_pipelining smtp "host list&!!" unset
24253 .cindex "PIPELINING" "avoiding the use of"
24254 Exim will not use the SMTP PIPELINING extension when delivering to any host
24255 that matches this list, even if the server host advertises PIPELINING support.
24256
24257
24258 .option hosts_avoid_tls smtp "host list&!!" unset
24259 .cindex "TLS" "avoiding for certain hosts"
24260 Exim will not try to start a TLS session when delivering to any host that
24261 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
24262
24263 .option hosts_verify_avoid_tls smtp "host list&!!" unset
24264 .cindex "TLS" "avoiding for certain hosts"
24265 Exim will not try to start a TLS session for a verify callout,
24266 or when delivering in cutthrough mode,
24267 to any host that matches this list.
24268
24269
24270 .option hosts_max_try smtp integer 5
24271 .cindex "host" "maximum number to try"
24272 .cindex "limit" "number of hosts tried"
24273 .cindex "limit" "number of MX tried"
24274 .cindex "MX record" "maximum tried"
24275 This option limits the number of IP addresses that are tried for any one
24276 delivery in cases where there are temporary delivery errors. Section
24277 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
24278
24279
24280 .option hosts_max_try_hardlimit smtp integer 50
24281 This is an additional check on the maximum number of IP addresses that Exim
24282 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
24283 why it exists.
24284
24285
24286
24287 .option hosts_nopass_tls smtp "host list&!!" unset
24288 .cindex "TLS" "passing connection"
24289 .cindex "multiple SMTP deliveries"
24290 .cindex "TLS" "multiple message deliveries"
24291 For any host that matches this list, a connection on which a TLS session has
24292 been started will not be passed to a new delivery process for sending another
24293 message on the same connection. See section &<<SECTmulmessam>>& for an
24294 explanation of when this might be needed.
24295
24296 .option hosts_noproxy_tls smtp "host list&!!" *
24297 .cindex "TLS" "passing connection"
24298 .cindex "multiple SMTP deliveries"
24299 .cindex "TLS" "multiple message deliveries"
24300 For any host that matches this list, a TLS session which has
24301 been started will not be passed to a new delivery process for sending another
24302 message on the same session.
24303
24304 The traditional implementation closes down TLS and re-starts it in the new
24305 process, on the same open TCP connection, for each successive message
24306 sent. If permitted by this option a pipe to to the new process is set up
24307 instead, and the original process maintains the TLS connection and proxies
24308 the SMTP connection from and to the new process and any subsequents.
24309 The new process has no access to TLS information, so cannot include it in
24310 logging.
24311
24312
24313
24314 .option hosts_override smtp boolean false
24315 If this option is set and the &%hosts%& option is also set, any hosts that are
24316 attached to the address are ignored, and instead the hosts specified by the
24317 &%hosts%& option are always used. This option does not apply to
24318 &%fallback_hosts%&.
24319
24320
24321 .option hosts_randomize smtp boolean false
24322 .cindex "randomized host list"
24323 .cindex "host" "list of; randomized"
24324 .cindex "fallback" "randomized hosts"
24325 If this option is set, and either the list of hosts is taken from the
24326 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
24327 were not obtained from MX records (this includes fallback hosts from the
24328 router), and were not randomized by the router, the order of trying the hosts
24329 is randomized each time the transport runs. Randomizing the order of a host
24330 list can be used to do crude load sharing.
24331
24332 When &%hosts_randomize%& is true, a host list may be split into groups whose
24333 order is separately randomized. This makes it possible to set up MX-like
24334 behaviour. The boundaries between groups are indicated by an item that is just
24335 &`+`& in the host list. For example:
24336 .code
24337 hosts = host1:host2:host3:+:host4:host5
24338 .endd
24339 The order of the first three hosts and the order of the last two hosts is
24340 randomized for each use, but the first three always end up before the last two.
24341 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
24342
24343 .option hosts_require_auth smtp "host list&!!" unset
24344 .cindex "authentication" "required by client"
24345 This option provides a list of servers for which authentication must succeed
24346 before Exim will try to transfer a message. If authentication fails for
24347 servers which are not in this list, Exim tries to send unauthenticated. If
24348 authentication fails for one of these servers, delivery is deferred. This
24349 temporary error is detectable in the retry rules, so it can be turned into a
24350 hard failure if required. See also &%hosts_try_auth%&, and chapter
24351 &<<CHAPSMTPAUTH>>& for details of authentication.
24352
24353
24354 .option hosts_request_ocsp smtp "host list&!!" *
24355 .cindex "TLS" "requiring for certain servers"
24356 Exim will request a Certificate Status on a
24357 TLS session for any host that matches this list.
24358 &%tls_verify_certificates%& should also be set for the transport.
24359
24360 .option hosts_require_dane smtp "host list&!!" unset
24361 .cindex DANE "transport options"
24362 .cindex DANE "requiring for certain servers"
24363 If built with DANE support, Exim will require that a DNSSEC-validated
24364 TLSA record is present for any host matching the list,
24365 and that a DANE-verified TLS connection is made.
24366 There will be no fallback to in-clear communication.
24367 See section &<<SECDANE>>&.
24368
24369 .option hosts_require_ocsp smtp "host list&!!" unset
24370 .cindex "TLS" "requiring for certain servers"
24371 Exim will request, and check for a valid Certificate Status being given, on a
24372 TLS session for any host that matches this list.
24373 &%tls_verify_certificates%& should also be set for the transport.
24374
24375 .option hosts_require_tls smtp "host list&!!" unset
24376 .cindex "TLS" "requiring for certain servers"
24377 Exim will insist on using a TLS session when delivering to any host that
24378 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
24379 &*Note*&: This option affects outgoing mail only. To insist on TLS for
24380 incoming messages, use an appropriate ACL.
24381
24382 .option hosts_try_auth smtp "host list&!!" unset
24383 .cindex "authentication" "optional in client"
24384 This option provides a list of servers to which, provided they announce
24385 authentication support, Exim will attempt to authenticate as a client when it
24386 connects. If authentication fails, Exim will try to transfer the message
24387 unauthenticated. See also &%hosts_require_auth%&, and chapter
24388 &<<CHAPSMTPAUTH>>& for details of authentication.
24389
24390 .option hosts_try_chunking smtp "host list&!!" *
24391 .cindex CHUNKING "enabling, in client"
24392 .cindex BDAT "SMTP command"
24393 .cindex "RFC 3030" "CHUNKING"
24394 This option provides a list of servers to which, provided they announce
24395 CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
24396 BDAT will not be used in conjunction with a transport filter.
24397
24398 .option hosts_try_dane smtp "host list&!!" unset
24399 .cindex DANE "transport options"
24400 .cindex DANE "attempting for certain servers"
24401 If built with DANE support, Exim will lookup a
24402 TLSA record for any host matching the list.
24403 If found and verified by DNSSEC,
24404 a DANE-verified TLS connection is made to that host;
24405 there will be no fallback to in-clear communication.
24406 See section &<<SECDANE>>&.
24407
24408 .option hosts_try_fastopen smtp "host list&!!" unset
24409 .cindex "fast open, TCP" "enabling, in client"
24410 .cindex "TCP Fast Open" "enabling, in client"
24411 .cindex "RFC 7413" "TCP Fast Open"
24412 This option provides a list of servers to which, provided
24413 the facility is supported by this system, Exim will attempt to
24414 perform a TCP Fast Open.
24415 No data is sent on the SYN segment but, if the remote server also
24416 supports the facility, it can send its SMTP banner immediately after
24417 the SYN,ACK segment. This can save up to one round-trip time.
24418
24419 The facility is only active for previously-contacted servers,
24420 as the initiator must present a cookie in the SYN segment.
24421
24422 On (at least some) current Linux distributions the facility must be enabled
24423 in the kernel by the sysadmin before the support is usable.
24424 There is no option for control of the server side; if the system supports
24425 it it is always enabled. Note that lengthy operations in the connect ACL,
24426 such as DNSBL lookups, will still delay the emission of the SMTP banner.
24427
24428 .option hosts_try_prdr smtp "host list&!!" *
24429 .cindex "PRDR" "enabling, optional in client"
24430 This option provides a list of servers to which, provided they announce
24431 PRDR support, Exim will attempt to negotiate PRDR
24432 for multi-recipient messages.
24433 The option can usually be left as default.
24434
24435 .option interface smtp "string list&!!" unset
24436 .cindex "bind IP address"
24437 .cindex "IP address" "binding"
24438 .vindex "&$host$&"
24439 .vindex "&$host_address$&"
24440 This option specifies which interface to bind to when making an outgoing SMTP
24441 call. The value is an IP address, not an interface name such as
24442 &`eth0`&. Do not confuse this with the interface address that was used when a
24443 message was received, which is in &$received_ip_address$&, formerly known as
24444 &$interface_address$&. The name was changed to minimize confusion with the
24445 outgoing interface address. There is no variable that contains an outgoing
24446 interface address because, unless it is set by this option, its value is
24447 unknown.
24448
24449 During the expansion of the &%interface%& option the variables &$host$& and
24450 &$host_address$& refer to the host to which a connection is about to be made
24451 during the expansion of the string. Forced expansion failure, or an empty
24452 string result causes the option to be ignored. Otherwise, after expansion, the
24453 string must be a list of IP addresses, colon-separated by default, but the
24454 separator can be changed in the usual way. For example:
24455 .code
24456 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
24457 .endd
24458 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
24459 connection. If none of them are the correct type, the option is ignored. If
24460 &%interface%& is not set, or is ignored, the system's IP functions choose which
24461 interface to use if the host has more than one.
24462
24463
24464 .option keepalive smtp boolean true
24465 .cindex "keepalive" "on outgoing connection"
24466 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
24467 connections. When set, it causes the kernel to probe idle connections
24468 periodically, by sending packets with &"old"& sequence numbers. The other end
24469 of the connection should send a acknowledgment if the connection is still okay
24470 or a reset if the connection has been aborted. The reason for doing this is
24471 that it has the beneficial effect of freeing up certain types of connection
24472 that can get stuck when the remote host is disconnected without tidying up the
24473 TCP/IP call properly. The keepalive mechanism takes several hours to detect
24474 unreachable hosts.
24475
24476
24477 .option lmtp_ignore_quota smtp boolean false
24478 .cindex "LMTP" "ignoring quota errors"
24479 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
24480 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
24481 has advertised support for IGNOREQUOTA in its response to the LHLO command.
24482
24483 .option max_rcpt smtp integer 100
24484 .cindex "RCPT" "maximum number of outgoing"
24485 This option limits the number of RCPT commands that are sent in a single
24486 SMTP message transaction. Each set of addresses is treated independently, and
24487 so can cause parallel connections to the same host if &%remote_max_parallel%&
24488 permits this.
24489
24490
24491 .option multi_domain smtp boolean&!! true
24492 .vindex "&$domain$&"
24493 When this option is set, the &(smtp)& transport can handle a number of
24494 addresses containing a mixture of different domains provided they all resolve
24495 to the same list of hosts. Turning the option off restricts the transport to
24496 handling only one domain at a time. This is useful if you want to use
24497 &$domain$& in an expansion for the transport, because it is set only when there
24498 is a single domain involved in a remote delivery.
24499
24500 It is expanded per-address and can depend on any of
24501 &$address_data$&, &$domain_data$&, &$local_part_data$&,
24502 &$host$&, &$host_address$& and &$host_port$&.
24503
24504 .option port smtp string&!! "see below"
24505 .cindex "port" "sending TCP/IP"
24506 .cindex "TCP/IP" "setting outgoing port"
24507 This option specifies the TCP/IP port on the server to which Exim connects.
24508 &*Note:*& Do not confuse this with the port that was used when a message was
24509 received, which is in &$received_port$&, formerly known as &$interface_port$&.
24510 The name was changed to minimize confusion with the outgoing port. There is no
24511 variable that contains an outgoing port.
24512
24513 If the value of this option begins with a digit it is taken as a port number;
24514 otherwise it is looked up using &[getservbyname()]&. The default value is
24515 normally &"smtp"&, but if &%protocol%& is set to &"lmtp"&, the default is
24516 &"lmtp"&. If the expansion fails, or if a port number cannot be found, delivery
24517 is deferred.
24518
24519
24520
24521 .option protocol smtp string smtp
24522 .cindex "LMTP" "over TCP/IP"
24523 .cindex "ssmtp protocol" "outbound"
24524 .cindex "TLS" "SSL-on-connect outbound"
24525 .vindex "&$port$&"
24526 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
24527 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
24528 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
24529 deliveries into closed message stores. Exim also has support for running LMTP
24530 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
24531
24532 If this option is set to &"smtps"&, the default value for the &%port%& option
24533 changes to &"smtps"&, and the transport initiates TLS immediately after
24534 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
24535 The Internet standards bodies strongly discourage use of this mode.
24536
24537
24538 .option retry_include_ip_address smtp boolean&!! true
24539 Exim normally includes both the host name and the IP address in the key it
24540 constructs for indexing retry data after a temporary delivery failure. This
24541 means that when one of several IP addresses for a host is failing, it gets
24542 tried periodically (controlled by the retry rules), but use of the other IP
24543 addresses is not affected.
24544
24545 However, in some dialup environments hosts are assigned a different IP address
24546 each time they connect. In this situation the use of the IP address as part of
24547 the retry key leads to undesirable behaviour. Setting this option false causes
24548 Exim to use only the host name.
24549 Since it is expanded it can be made to depend on the host or domain.
24550
24551
24552 .option serialize_hosts smtp "host list&!!" unset
24553 .cindex "serializing connections"
24554 .cindex "host" "serializing connections"
24555 Because Exim operates in a distributed manner, if several messages for the same
24556 host arrive at around the same time, more than one simultaneous connection to
24557 the remote host can occur. This is not usually a problem except when there is a
24558 slow link between the hosts. In that situation it may be helpful to restrict
24559 Exim to one connection at a time. This can be done by setting
24560 &%serialize_hosts%& to match the relevant hosts.
24561
24562 .cindex "hints database" "serializing deliveries to a host"
24563 Exim implements serialization by means of a hints database in which a record is
24564 written whenever a process connects to one of the restricted hosts. The record
24565 is deleted when the connection is completed. Obviously there is scope for
24566 records to get left lying around if there is a system or program crash. To
24567 guard against this, Exim ignores any records that are more than six hours old.
24568
24569 If you set up this kind of serialization, you should also arrange to delete the
24570 relevant hints database whenever your system reboots. The names of the files
24571 start with &_misc_& and they are kept in the &_spool/db_& directory. There
24572 may be one or two files, depending on the type of DBM in use. The same files
24573 are used for ETRN serialization.
24574
24575 See also the &%max_parallel%& generic transport option.
24576
24577
24578 .option size_addition smtp integer 1024
24579 .cindex "SMTP" "SIZE"
24580 .cindex "message" "size issue for transport filter"
24581 .cindex "size" "of message"
24582 .cindex "transport" "filter"
24583 .cindex "filter" "transport filter"
24584 If a remote SMTP server indicates that it supports the SIZE option of the
24585 MAIL command, Exim uses this to pass over the message size at the start of
24586 an SMTP transaction. It adds the value of &%size_addition%& to the value it
24587 sends, to allow for headers and other text that may be added during delivery by
24588 configuration options or in a transport filter. It may be necessary to increase
24589 this if a lot of text is added to messages.
24590
24591 Alternatively, if the value of &%size_addition%& is set negative, it disables
24592 the use of the SIZE option altogether.
24593
24594
24595 .option socks_proxy smtp string&!! unset
24596 .cindex proxy SOCKS
24597 This option enables use of SOCKS proxies for connections made by the
24598 transport. For details see section &<<SECTproxySOCKS>>&.
24599
24600
24601 .option tls_certificate smtp string&!! unset
24602 .cindex "TLS" "client certificate, location of"
24603 .cindex "certificate" "client, location of"
24604 .vindex "&$host$&"
24605 .vindex "&$host_address$&"
24606 The value of this option must be the absolute path to a file which contains the
24607 client's certificate, for possible use when sending a message over an encrypted
24608 connection. The values of &$host$& and &$host_address$& are set to the name and
24609 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
24610 details of TLS.
24611
24612 &*Note*&: This option must be set if you want Exim to be able to use a TLS
24613 certificate when sending messages as a client. The global option of the same
24614 name specifies the certificate for Exim as a server; it is not automatically
24615 assumed that the same certificate should be used when Exim is operating as a
24616 client.
24617
24618
24619 .option tls_crl smtp string&!! unset
24620 .cindex "TLS" "client certificate revocation list"
24621 .cindex "certificate" "revocation list for client"
24622 This option specifies a certificate revocation list. The expanded value must
24623 be the name of a file that contains a CRL in PEM format.
24624
24625
24626 .option tls_dh_min_bits smtp integer 1024
24627 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
24628 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
24629 key agreement is negotiated, the server will provide a large prime number
24630 for use. This option establishes the minimum acceptable size of that number.
24631 If the parameter offered by the server is too small, then the TLS handshake
24632 will fail.
24633
24634 Only supported when using GnuTLS.
24635
24636
24637 .option tls_privatekey smtp string&!! unset
24638 .cindex "TLS" "client private key, location of"
24639 .vindex "&$host$&"
24640 .vindex "&$host_address$&"
24641 The value of this option must be the absolute path to a file which contains the
24642 client's private key. This is used when sending a message over an encrypted
24643 connection using a client certificate. The values of &$host$& and
24644 &$host_address$& are set to the name and address of the server during the
24645 expansion. If this option is unset, or the expansion is forced to fail, or the
24646 result is an empty string, the private key is assumed to be in the same file as
24647 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
24648
24649
24650 .option tls_require_ciphers smtp string&!! unset
24651 .cindex "TLS" "requiring specific ciphers"
24652 .cindex "cipher" "requiring specific"
24653 .vindex "&$host$&"
24654 .vindex "&$host_address$&"
24655 The value of this option must be a list of permitted cipher suites, for use
24656 when setting up an outgoing encrypted connection. (There is a global option of
24657 the same name for controlling incoming connections.) The values of &$host$& and
24658 &$host_address$& are set to the name and address of the server during the
24659 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
24660 is used in different ways by OpenSSL and GnuTLS (see sections
24661 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
24662 ciphers is a preference order.
24663
24664
24665
24666 .option tls_sni smtp string&!! unset
24667 .cindex "TLS" "Server Name Indication"
24668 .vindex "&$tls_sni$&"
24669 If this option is set then it sets the $tls_out_sni variable and causes any
24670 TLS session to pass this value as the Server Name Indication extension to
24671 the remote side, which can be used by the remote side to select an appropriate
24672 certificate and private key for the session.
24673
24674 See &<<SECTtlssni>>& for more information.
24675
24676 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
24677 TLS extensions.
24678
24679
24680
24681
24682 .option tls_tempfail_tryclear smtp boolean true
24683 .cindex "4&'xx'& responses" "to STARTTLS"
24684 When the server host is not in &%hosts_require_tls%&, and there is a problem in
24685 setting up a TLS session, this option determines whether or not Exim should try
24686 to deliver the message unencrypted. If it is set false, delivery to the
24687 current host is deferred; if there are other hosts, they are tried. If this
24688 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
24689 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
24690 TLS negotiation fails, Exim closes the current connection (because it is in an
24691 unknown state), opens a new one to the same host, and then tries the delivery
24692 in clear.
24693
24694
24695 .option tls_try_verify_hosts smtp "host list&!!" *
24696 .cindex "TLS" "server certificate verification"
24697 .cindex "certificate" "verification of server"
24698 This option gives a list of hosts for which, on encrypted connections,
24699 certificate verification will be tried but need not succeed.
24700 The &%tls_verify_certificates%& option must also be set.
24701 Note that unless the host is in this list
24702 TLS connections will be denied to hosts using self-signed certificates
24703 when &%tls_verify_certificates%& is matched.
24704 The &$tls_out_certificate_verified$& variable is set when
24705 certificate verification succeeds.
24706
24707
24708 .option tls_verify_cert_hostnames smtp "host list&!!" *
24709 .cindex "TLS" "server certificate hostname verification"
24710 .cindex "certificate" "verification of server"
24711 This option give a list of hosts for which,
24712 while verifying the server certificate,
24713 checks will be included on the host name
24714 (note that this will generally be the result of a DNS MX lookup)
24715 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
24716 limited to being the initial component of a 3-or-more component FQDN.
24717
24718 There is no equivalent checking on client certificates.
24719
24720
24721 .option tls_verify_certificates smtp string&!! system
24722 .cindex "TLS" "server certificate verification"
24723 .cindex "certificate" "verification of server"
24724 .vindex "&$host$&"
24725 .vindex "&$host_address$&"
24726 The value of this option must be either the
24727 word "system"
24728 or the absolute path to
24729 a file or directory containing permitted certificates for servers,
24730 for use when setting up an encrypted connection.
24731
24732 The "system" value for the option will use a location compiled into the SSL library.
24733 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
24734 is taken as empty and an explicit location
24735 must be specified.
24736
24737 The use of a directory for the option value is not available for GnuTLS versions
24738 preceding 3.3.6 and a single file must be used.
24739
24740 With OpenSSL the certificates specified
24741 explicitly
24742 either by file or directory
24743 are added to those given by the system default location.
24744
24745 The values of &$host$& and
24746 &$host_address$& are set to the name and address of the server during the
24747 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
24748
24749 For back-compatibility,
24750 if neither tls_verify_hosts nor tls_try_verify_hosts are set
24751 (a single-colon empty list counts as being set)
24752 and certificate verification fails the TLS connection is closed.
24753
24754
24755 .option tls_verify_hosts smtp "host list&!!" unset
24756 .cindex "TLS" "server certificate verification"
24757 .cindex "certificate" "verification of server"
24758 This option gives a list of hosts for which, on encrypted connections,
24759 certificate verification must succeed.
24760 The &%tls_verify_certificates%& option must also be set.
24761 If both this option and &%tls_try_verify_hosts%& are unset
24762 operation is as if this option selected all hosts.
24763
24764 .new
24765 .option utf8_downconvert smtp integer!! unset
24766 .cindex utf8 "address downconversion"
24767 .cindex i18n "utf8 address downconversion"
24768 If built with internationalization support,
24769 this option controls conversion of UTF-8 in message addresses
24770 to a-label form.
24771 For details see section &<<SECTi18nMTA>>&.
24772 .wen
24773
24774
24775
24776
24777 .section "How the limits for the number of hosts to try are used" &&&
24778 "SECTvalhosmax"
24779 .cindex "host" "maximum number to try"
24780 .cindex "limit" "hosts; maximum number tried"
24781 There are two options that are concerned with the number of hosts that are
24782 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
24783 &%hosts_max_try_hardlimit%&.
24784
24785
24786 The &%hosts_max_try%& option limits the number of hosts that are tried
24787 for a single delivery. However, despite the term &"host"& in its name, the
24788 option actually applies to each IP address independently. In other words, a
24789 multihomed host is treated as several independent hosts, just as it is for
24790 retrying.
24791
24792 Many of the larger ISPs have multiple MX records which often point to
24793 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
24794 created as a result of routing one of these domains.
24795
24796 Trying every single IP address on such a long list does not seem sensible; if
24797 several at the top of the list fail, it is reasonable to assume there is some
24798 problem that is likely to affect all of them. Roughly speaking, the value of
24799 &%hosts_max_try%& is the maximum number that are tried before deferring the
24800 delivery. However, the logic cannot be quite that simple.
24801
24802 Firstly, IP addresses that are skipped because their retry times have not
24803 arrived do not count, and in addition, addresses that are past their retry
24804 limits are also not counted, even when they are tried. This means that when
24805 some IP addresses are past their retry limits, more than the value of
24806 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
24807 that all IP addresses are considered before timing out an email address (but
24808 see below for an exception).
24809
24810 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
24811 list to see if there is a subsequent host with a different (higher valued) MX.
24812 If there is, that host is considered next, and the current IP address is used
24813 but not counted. This behaviour helps in the case of a domain with a retry rule
24814 that hardly ever delays any hosts, as is now explained:
24815
24816 Consider the case of a long list of hosts with one MX value, and a few with a
24817 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
24818 hosts at the top of the list are tried at first. With the default retry rule,
24819 which specifies increasing retry times, the higher MX hosts are eventually
24820 tried when those at the top of the list are skipped because they have not
24821 reached their retry times.
24822
24823 However, it is common practice to put a fixed short retry time on domains for
24824 large ISPs, on the grounds that their servers are rarely down for very long.
24825 Unfortunately, these are exactly the domains that tend to resolve to long lists
24826 of hosts. The short retry time means that the lowest MX hosts are tried every
24827 time. The attempts may be in a different order because of random sorting, but
24828 without the special MX check, the higher MX hosts would never be tried until
24829 all the lower MX hosts had timed out (which might be several days), because
24830 there are always some lower MX hosts that have reached their retry times. With
24831 the special check, Exim considers at least one IP address from each MX value at
24832 every delivery attempt, even if the &%hosts_max_try%& limit has already been
24833 reached.
24834
24835 The above logic means that &%hosts_max_try%& is not a hard limit, and in
24836 particular, Exim normally eventually tries all the IP addresses before timing
24837 out an email address. When &%hosts_max_try%& was implemented, this seemed a
24838 reasonable thing to do. Recently, however, some lunatic DNS configurations have
24839 been set up with hundreds of IP addresses for some domains. It can
24840 take a very long time indeed for an address to time out in these cases.
24841
24842 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
24843 Exim never tries more than this number of IP addresses; if it hits this limit
24844 and they are all timed out, the email address is bounced, even though not all
24845 possible IP addresses have been tried.
24846 .ecindex IIDsmttra1
24847 .ecindex IIDsmttra2
24848
24849
24850
24851
24852
24853 . ////////////////////////////////////////////////////////////////////////////
24854 . ////////////////////////////////////////////////////////////////////////////
24855
24856 .chapter "Address rewriting" "CHAPrewrite"
24857 .scindex IIDaddrew "rewriting" "addresses"
24858 There are some circumstances in which Exim automatically rewrites domains in
24859 addresses. The two most common are when an address is given without a domain
24860 (referred to as an &"unqualified address"&) or when an address contains an
24861 abbreviated domain that is expanded by DNS lookup.
24862
24863 Unqualified envelope addresses are accepted only for locally submitted
24864 messages, or for messages that are received from hosts matching
24865 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
24866 appropriate. Unqualified addresses in header lines are qualified if they are in
24867 locally submitted messages, or messages from hosts that are permitted to send
24868 unqualified envelope addresses. Otherwise, unqualified addresses in header
24869 lines are neither qualified nor rewritten.
24870
24871 One situation in which Exim does &'not'& automatically rewrite a domain is
24872 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
24873 such a domain should be rewritten using the &"canonical"& name, and some MTAs
24874 do this. The new RFCs do not contain this suggestion.
24875
24876
24877 .section "Explicitly configured address rewriting" "SECID147"
24878 This chapter describes the rewriting rules that can be used in the
24879 main rewrite section of the configuration file, and also in the generic
24880 &%headers_rewrite%& option that can be set on any transport.
24881
24882 Some people believe that configured address rewriting is a Mortal Sin.
24883 Others believe that life is not possible without it. Exim provides the
24884 facility; you do not have to use it.
24885
24886 The main rewriting rules that appear in the &"rewrite"& section of the
24887 configuration file are applied to addresses in incoming messages, both envelope
24888 addresses and addresses in header lines. Each rule specifies the types of
24889 address to which it applies.
24890
24891 Whether or not addresses in header lines are rewritten depends on the origin of
24892 the headers and the type of rewriting. Global rewriting, that is, rewriting
24893 rules from the rewrite section of the configuration file, is applied only to
24894 those headers that were received with the message. Header lines that are added
24895 by ACLs or by a system filter or by individual routers or transports (which
24896 are specific to individual recipient addresses) are not rewritten by the global
24897 rules.
24898
24899 Rewriting at transport time, by means of the &%headers_rewrite%& option,
24900 applies all headers except those added by routers and transports. That is, as
24901 well as the headers that were received with the message, it also applies to
24902 headers that were added by an ACL or a system filter.
24903
24904
24905 In general, rewriting addresses from your own system or domain has some
24906 legitimacy. Rewriting other addresses should be done only with great care and
24907 in special circumstances. The author of Exim believes that rewriting should be
24908 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
24909 Although it can sometimes be used as a routing tool, this is very strongly
24910 discouraged.
24911
24912 There are two commonly encountered circumstances where rewriting is used, as
24913 illustrated by these examples:
24914
24915 .ilist
24916 The company whose domain is &'hitch.fict.example'& has a number of hosts that
24917 exchange mail with each other behind a firewall, but there is only a single
24918 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
24919 &'hitch.fict.example'& when sending mail off-site.
24920 .next
24921 A host rewrites the local parts of its own users so that, for example,
24922 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
24923 .endlist
24924
24925
24926
24927 .section "When does rewriting happen?" "SECID148"
24928 .cindex "rewriting" "timing of"
24929 .cindex "&ACL;" "rewriting addresses in"
24930 Configured address rewriting can take place at several different stages of a
24931 message's processing.
24932
24933 .vindex "&$sender_address$&"
24934 At the start of an ACL for MAIL, the sender address may have been rewritten
24935 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
24936 ordinary rewrite rules have yet been applied. If, however, the sender address
24937 is verified in the ACL, it is rewritten before verification, and remains
24938 rewritten thereafter. The subsequent value of &$sender_address$& is the
24939 rewritten address. This also applies if sender verification happens in a
24940 RCPT ACL. Otherwise, when the sender address is not verified, it is
24941 rewritten as soon as a message's header lines have been received.
24942
24943 .vindex "&$domain$&"
24944 .vindex "&$local_part$&"
24945 Similarly, at the start of an ACL for RCPT, the current recipient's address
24946 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
24947 rewrite rules have yet been applied to it. However, the behaviour is different
24948 from the sender address when a recipient is verified. The address is rewritten
24949 for the verification, but the rewriting is not remembered at this stage. The
24950 value of &$local_part$& and &$domain$& after verification are always the same
24951 as they were before (that is, they contain the unrewritten &-- except for
24952 SMTP-time rewriting &-- address).
24953
24954 As soon as a message's header lines have been received, all the envelope
24955 recipient addresses are permanently rewritten, and rewriting is also applied to
24956 the addresses in the header lines (if configured). This happens before adding
24957 any header lines that were specified in MAIL or RCPT ACLs, and
24958 .cindex "&[local_scan()]& function" "address rewriting; timing of"
24959 before the DATA ACL and &[local_scan()]& functions are run.
24960
24961 When an address is being routed, either for delivery or for verification,
24962 rewriting is applied immediately to child addresses that are generated by
24963 redirection, unless &%no_rewrite%& is set on the router.
24964
24965 .cindex "envelope sender" "rewriting at transport time"
24966 .cindex "rewriting" "at transport time"
24967 .cindex "header lines" "rewriting at transport time"
24968 At transport time, additional rewriting of addresses in header lines can be
24969 specified by setting the generic &%headers_rewrite%& option on a transport.
24970 This option contains rules that are identical in form to those in the rewrite
24971 section of the configuration file. They are applied to the original message
24972 header lines and any that were added by ACLs or a system filter. They are not
24973 applied to header lines that are added by routers or the transport.
24974
24975 The outgoing envelope sender can be rewritten by means of the &%return_path%&
24976 transport option. However, it is not possible to rewrite envelope recipients at
24977 transport time.
24978
24979
24980
24981
24982 .section "Testing the rewriting rules that apply on input" "SECID149"
24983 .cindex "rewriting" "testing"
24984 .cindex "testing" "rewriting"
24985 Exim's input rewriting configuration appears in a part of the run time
24986 configuration file headed by &"begin rewrite"&. It can be tested by the
24987 &%-brw%& command line option. This takes an address (which can be a full RFC
24988 2822 address) as its argument. The output is a list of how the address would be
24989 transformed by the rewriting rules for each of the different places it might
24990 appear in an incoming message, that is, for each different header and for the
24991 envelope sender and recipient fields. For example,
24992 .code
24993 exim -brw ph10@exim.workshop.example
24994 .endd
24995 might produce the output
24996 .code
24997 sender: Philip.Hazel@exim.workshop.example
24998 from: Philip.Hazel@exim.workshop.example
24999 to: ph10@exim.workshop.example
25000 cc: ph10@exim.workshop.example
25001 bcc: ph10@exim.workshop.example
25002 reply-to: Philip.Hazel@exim.workshop.example
25003 env-from: Philip.Hazel@exim.workshop.example
25004 env-to: ph10@exim.workshop.example
25005 .endd
25006 which shows that rewriting has been set up for that address when used in any of
25007 the source fields, but not when it appears as a recipient address. At the
25008 present time, there is no equivalent way of testing rewriting rules that are
25009 set for a particular transport.
25010
25011
25012 .section "Rewriting rules" "SECID150"
25013 .cindex "rewriting" "rules"
25014 The rewrite section of the configuration file consists of lines of rewriting
25015 rules in the form
25016 .display
25017 <&'source pattern'&> <&'replacement'&> <&'flags'&>
25018 .endd
25019 Rewriting rules that are specified for the &%headers_rewrite%& generic
25020 transport option are given as a colon-separated list. Each item in the list
25021 takes the same form as a line in the main rewriting configuration (except that
25022 any colons must be doubled, of course).
25023
25024 The formats of source patterns and replacement strings are described below.
25025 Each is terminated by white space, unless enclosed in double quotes, in which
25026 case normal quoting conventions apply inside the quotes. The flags are single
25027 characters which may appear in any order. Spaces and tabs between them are
25028 ignored.
25029
25030 For each address that could potentially be rewritten, the rules are scanned in
25031 order, and replacements for the address from earlier rules can themselves be
25032 replaced by later rules (but see the &"q"& and &"R"& flags).
25033
25034 The order in which addresses are rewritten is undefined, may change between
25035 releases, and must not be relied on, with one exception: when a message is
25036 received, the envelope sender is always rewritten first, before any header
25037 lines are rewritten. For example, the replacement string for a rewrite of an
25038 address in &'To:'& must not assume that the message's address in &'From:'& has
25039 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
25040 that the envelope sender has already been rewritten.
25041
25042 .vindex "&$domain$&"
25043 .vindex "&$local_part$&"
25044 The variables &$local_part$& and &$domain$& can be used in the replacement
25045 string to refer to the address that is being rewritten. Note that lookup-driven
25046 rewriting can be done by a rule of the form
25047 .code
25048 *@* ${lookup ...
25049 .endd
25050 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
25051 refer to the address that is being rewritten.
25052
25053
25054 .section "Rewriting patterns" "SECID151"
25055 .cindex "rewriting" "patterns"
25056 .cindex "address list" "in a rewriting pattern"
25057 The source pattern in a rewriting rule is any item which may appear in an
25058 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
25059 single-item address list, which means that it is expanded before being tested
25060 against the address. As always, if you use a regular expression as a pattern,
25061 you must take care to escape dollar and backslash characters, or use the &`\N`&
25062 facility to suppress string expansion within the regular expression.
25063
25064 Domains in patterns should be given in lower case. Local parts in patterns are
25065 case-sensitive. If you want to do case-insensitive matching of local parts, you
25066 can use a regular expression that starts with &`^(?i)`&.
25067
25068 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
25069 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
25070 depending on the type of match which occurred. These can be used in the
25071 replacement string to insert portions of the incoming address. &$0$& always
25072 refers to the complete incoming address. When a regular expression is used, the
25073 numerical variables are set from its capturing subexpressions. For other types
25074 of pattern they are set as follows:
25075
25076 .ilist
25077 If a local part or domain starts with an asterisk, the numerical variables
25078 refer to the character strings matched by asterisks, with &$1$& associated with
25079 the first asterisk, and &$2$& with the second, if present. For example, if the
25080 pattern
25081 .code
25082 *queen@*.fict.example
25083 .endd
25084 is matched against the address &'hearts-queen@wonderland.fict.example'& then
25085 .code
25086 $0 = hearts-queen@wonderland.fict.example
25087 $1 = hearts-
25088 $2 = wonderland
25089 .endd
25090 Note that if the local part does not start with an asterisk, but the domain
25091 does, it is &$1$& that contains the wild part of the domain.
25092
25093 .next
25094 If the domain part of the pattern is a partial lookup, the wild and fixed parts
25095 of the domain are placed in the next available numerical variables. Suppose,
25096 for example, that the address &'foo@bar.baz.example'& is processed by a
25097 rewriting rule of the form
25098 .display
25099 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
25100 .endd
25101 and the key in the file that matches the domain is &`*.baz.example`&. Then
25102 .code
25103 $1 = foo
25104 $2 = bar
25105 $3 = baz.example
25106 .endd
25107 If the address &'foo@baz.example'& is looked up, this matches the same
25108 wildcard file entry, and in this case &$2$& is set to the empty string, but
25109 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
25110 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
25111 whole domain. For non-partial domain lookups, no numerical variables are set.
25112 .endlist
25113
25114
25115 .section "Rewriting replacements" "SECID152"
25116 .cindex "rewriting" "replacements"
25117 If the replacement string for a rule is a single asterisk, addresses that
25118 match the pattern and the flags are &'not'& rewritten, and no subsequent
25119 rewriting rules are scanned. For example,
25120 .code
25121 hatta@lookingglass.fict.example * f
25122 .endd
25123 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
25124 &'From:'& headers.
25125
25126 .vindex "&$domain$&"
25127 .vindex "&$local_part$&"
25128 If the replacement string is not a single asterisk, it is expanded, and must
25129 yield a fully qualified address. Within the expansion, the variables
25130 &$local_part$& and &$domain$& refer to the address that is being rewritten.
25131 Any letters they contain retain their original case &-- they are not lower
25132 cased. The numerical variables are set up according to the type of pattern that
25133 matched the address, as described above. If the expansion is forced to fail by
25134 the presence of &"fail"& in a conditional or lookup item, rewriting by the
25135 current rule is abandoned, but subsequent rules may take effect. Any other
25136 expansion failure causes the entire rewriting operation to be abandoned, and an
25137 entry written to the panic log.
25138
25139
25140
25141 .section "Rewriting flags" "SECID153"
25142 There are three different kinds of flag that may appear on rewriting rules:
25143
25144 .ilist
25145 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
25146 c, f, h, r, s, t.
25147 .next
25148 A flag that specifies rewriting at SMTP time: S.
25149 .next
25150 Flags that control the rewriting process: Q, q, R, w.
25151 .endlist
25152
25153 For rules that are part of the &%headers_rewrite%& generic transport option,
25154 E, F, T, and S are not permitted.
25155
25156
25157
25158 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
25159 "SECID154"
25160 .cindex "rewriting" "flags"
25161 If none of the following flag letters, nor the &"S"& flag (see section
25162 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
25163 and to both the sender and recipient fields of the envelope, whereas a
25164 transport-time rewriting rule just applies to all headers. Otherwise, the
25165 rewriting rule is skipped unless the relevant addresses are being processed.
25166 .display
25167 &`E`& rewrite all envelope fields
25168 &`F`& rewrite the envelope From field
25169 &`T`& rewrite the envelope To field
25170 &`b`& rewrite the &'Bcc:'& header
25171 &`c`& rewrite the &'Cc:'& header
25172 &`f`& rewrite the &'From:'& header
25173 &`h`& rewrite all headers
25174 &`r`& rewrite the &'Reply-To:'& header
25175 &`s`& rewrite the &'Sender:'& header
25176 &`t`& rewrite the &'To:'& header
25177 .endd
25178 "All headers" means all of the headers listed above that can be selected
25179 individually, plus their &'Resent-'& versions. It does not include
25180 other headers such as &'Subject:'& etc.
25181
25182 You should be particularly careful about rewriting &'Sender:'& headers, and
25183 restrict this to special known cases in your own domains.
25184
25185
25186 .section "The SMTP-time rewriting flag" "SECTrewriteS"
25187 .cindex "SMTP" "rewriting malformed addresses"
25188 .cindex "RCPT" "rewriting argument of"
25189 .cindex "MAIL" "rewriting argument of"
25190 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
25191 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
25192 before any other processing; even before syntax checking. The pattern is
25193 required to be a regular expression, and it is matched against the whole of the
25194 data for the command, including any surrounding angle brackets.
25195
25196 .vindex "&$domain$&"
25197 .vindex "&$local_part$&"
25198 This form of rewrite rule allows for the handling of addresses that are not
25199 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
25200 input). Because the input is not required to be a syntactically valid address,
25201 the variables &$local_part$& and &$domain$& are not available during the
25202 expansion of the replacement string. The result of rewriting replaces the
25203 original address in the MAIL or RCPT command.
25204
25205
25206 .section "Flags controlling the rewriting process" "SECID155"
25207 There are four flags which control the way the rewriting process works. These
25208 take effect only when a rule is invoked, that is, when the address is of the
25209 correct type (matches the flags) and matches the pattern:
25210
25211 .ilist
25212 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
25213 unqualified local part. It is qualified with &%qualify_recipient%&. In the
25214 absence of &"Q"& the rewritten address must always include a domain.
25215 .next
25216 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
25217 even if no rewriting actually takes place because of a &"fail"& in the
25218 expansion. The &"q"& flag is not effective if the address is of the wrong type
25219 (does not match the flags) or does not match the pattern.
25220 .next
25221 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
25222 address, up to ten times. It can be combined with the &"q"& flag, to stop
25223 rewriting once it fails to match (after at least one successful rewrite).
25224 .next
25225 .cindex "rewriting" "whole addresses"
25226 When an address in a header is rewritten, the rewriting normally applies only
25227 to the working part of the address, with any comments and RFC 2822 &"phrase"&
25228 left unchanged. For example, rewriting might change
25229 .code
25230 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
25231 .endd
25232 into
25233 .code
25234 From: Ford Prefect <prefectf@hitch.fict.example>
25235 .endd
25236 .cindex "RFC 2047"
25237 Sometimes there is a need to replace the whole address item, and this can be
25238 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
25239 causes an address in a header line to be rewritten, the entire address is
25240 replaced, not just the working part. The replacement must be a complete RFC
25241 2822 address, including the angle brackets if necessary. If text outside angle
25242 brackets contains a character whose value is greater than 126 or less than 32
25243 (except for tab), the text is encoded according to RFC 2047. The character set
25244 is taken from &%headers_charset%&, which gets its default at build time.
25245
25246 When the &"w"& flag is set on a rule that causes an envelope address to be
25247 rewritten, all but the working part of the replacement address is discarded.
25248 .endlist
25249
25250
25251 .section "Rewriting examples" "SECID156"
25252 Here is an example of the two common rewriting paradigms:
25253 .code
25254 *@*.hitch.fict.example $1@hitch.fict.example
25255 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
25256 {$value}fail}@hitch.fict.example bctfrF
25257 .endd
25258 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
25259 the string expansion to fail if the lookup does not succeed. In this context it
25260 has the effect of leaving the original address unchanged, but Exim goes on to
25261 consider subsequent rewriting rules, if any, because the &"q"& flag is not
25262 present in that rule. An alternative to &"fail"& would be to supply &$1$&
25263 explicitly, which would cause the rewritten address to be the same as before,
25264 at the cost of a small bit of processing. Not supplying either of these is an
25265 error, since the rewritten address would then contain no local part.
25266
25267 The first example above replaces the domain with a superior, more general
25268 domain. This may not be desirable for certain local parts. If the rule
25269 .code
25270 root@*.hitch.fict.example *
25271 .endd
25272 were inserted before the first rule, rewriting would be suppressed for the
25273 local part &'root'& at any domain ending in &'hitch.fict.example'&.
25274
25275 Rewriting can be made conditional on a number of tests, by making use of
25276 &${if$& in the expansion item. For example, to apply a rewriting rule only to
25277 messages that originate outside the local host:
25278 .code
25279 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
25280 {$1@hitch.fict.example}fail}"
25281 .endd
25282 The replacement string is quoted in this example because it contains white
25283 space.
25284
25285 .cindex "rewriting" "bang paths"
25286 .cindex "bang paths" "rewriting"
25287 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
25288 an address it treats it as an unqualified local part which it qualifies with
25289 the local qualification domain (if the source of the message is local or if the
25290 remote host is permitted to send unqualified addresses). Rewriting can
25291 sometimes be used to handle simple bang paths with a fixed number of
25292 components. For example, the rule
25293 .code
25294 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
25295 .endd
25296 rewrites a two-component bang path &'host.name!user'& as the domain address
25297 &'user@host.name'&. However, there is a security implication in using this as
25298 a global rewriting rule for envelope addresses. It can provide a backdoor
25299 method for using your system as a relay, because the incoming addresses appear
25300 to be local. If the bang path addresses are received via SMTP, it is safer to
25301 use the &"S"& flag to rewrite them as they are received, so that relay checking
25302 can be done on the rewritten addresses.
25303 .ecindex IIDaddrew
25304
25305
25306
25307
25308
25309 . ////////////////////////////////////////////////////////////////////////////
25310 . ////////////////////////////////////////////////////////////////////////////
25311
25312 .chapter "Retry configuration" "CHAPretry"
25313 .scindex IIDretconf1 "retry" "configuration, description of"
25314 .scindex IIDregconf2 "configuration file" "retry section"
25315 The &"retry"& section of the runtime configuration file contains a list of
25316 retry rules that control how often Exim tries to deliver messages that cannot
25317 be delivered at the first attempt. If there are no retry rules (the section is
25318 empty or not present), there are no retries. In this situation, temporary
25319 errors are treated as permanent. The default configuration contains a single,
25320 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
25321 line option can be used to test which retry rule will be used for a given
25322 address, domain and error.
25323
25324 The most common cause of retries is temporary failure to deliver to a remote
25325 host because the host is down, or inaccessible because of a network problem.
25326 Exim's retry processing in this case is applied on a per-host (strictly, per IP
25327 address) basis, not on a per-message basis. Thus, if one message has recently
25328 been delayed, delivery of a new message to the same host is not immediately
25329 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
25330 log selector is set, the message
25331 .cindex "retry" "time not reached"
25332 &"retry time not reached"& is written to the main log whenever a delivery is
25333 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
25334 the handling of errors during remote deliveries.
25335
25336 Retry processing applies to routing as well as to delivering, except as covered
25337 in the next paragraph. The retry rules do not distinguish between these
25338 actions. It is not possible, for example, to specify different behaviour for
25339 failures to route the domain &'snark.fict.example'& and failures to deliver to
25340 the host &'snark.fict.example'&. I didn't think anyone would ever need this
25341 added complication, so did not implement it. However, although they share the
25342 same retry rule, the actual retry times for routing and transporting a given
25343 domain are maintained independently.
25344
25345 When a delivery is not part of a queue run (typically an immediate delivery on
25346 receipt of a message), the routers are always run, and local deliveries are
25347 always attempted, even if retry times are set for them. This makes for better
25348 behaviour if one particular message is causing problems (for example, causing
25349 quota overflow, or provoking an error in a filter file). If such a delivery
25350 suffers a temporary failure, the retry data is updated as normal, and
25351 subsequent delivery attempts from queue runs occur only when the retry time for
25352 the local address is reached.
25353
25354 .section "Changing retry rules" "SECID157"
25355 If you change the retry rules in your configuration, you should consider
25356 whether or not to delete the retry data that is stored in Exim's spool area in
25357 files with names like &_db/retry_&. Deleting any of Exim's hints files is
25358 always safe; that is why they are called &"hints"&.
25359
25360 The hints retry data contains suggested retry times based on the previous
25361 rules. In the case of a long-running problem with a remote host, it might
25362 record the fact that the host has timed out. If your new rules increase the
25363 timeout time for such a host, you should definitely remove the old retry data
25364 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
25365 messages that it should now be retaining.
25366
25367
25368
25369 .section "Format of retry rules" "SECID158"
25370 .cindex "retry" "rules"
25371 Each retry rule occupies one line and consists of three or four parts,
25372 separated by white space: a pattern, an error name, an optional list of sender
25373 addresses, and a list of retry parameters. The pattern and sender lists must be
25374 enclosed in double quotes if they contain white space. The rules are searched
25375 in order until one is found where the pattern, error name, and sender list (if
25376 present) match the failing host or address, the error that occurred, and the
25377 message's sender, respectively.
25378
25379
25380 The pattern is any single item that may appear in an address list (see section
25381 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
25382 which means that it is expanded before being tested against the address that
25383 has been delayed. A negated address list item is permitted. Address
25384 list processing treats a plain domain name as if it were preceded by &"*@"&,
25385 which makes it possible for many retry rules to start with just a domain. For
25386 example,
25387 .code
25388 lookingglass.fict.example * F,24h,30m;
25389 .endd
25390 provides a rule for any address in the &'lookingglass.fict.example'& domain,
25391 whereas
25392 .code
25393 alice@lookingglass.fict.example * F,24h,30m;
25394 .endd
25395 applies only to temporary failures involving the local part &%alice%&.
25396 In practice, almost all rules start with a domain name pattern without a local
25397 part.
25398
25399 .cindex "regular expressions" "in retry rules"
25400 &*Warning*&: If you use a regular expression in a retry rule pattern, it
25401 must match a complete address, not just a domain, because that is how regular
25402 expressions work in address lists.
25403 .display
25404 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
25405 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
25406 .endd
25407
25408
25409 .section "Choosing which retry rule to use for address errors" "SECID159"
25410 When Exim is looking for a retry rule after a routing attempt has failed (for
25411 example, after a DNS timeout), each line in the retry configuration is tested
25412 against the complete address only if &%retry_use_local_part%& is set for the
25413 router. Otherwise, only the domain is used, except when matching against a
25414 regular expression, when the local part of the address is replaced with &"*"&.
25415 A domain on its own can match a domain pattern, or a pattern that starts with
25416 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
25417 &%check_local_user%& is true, and false for other routers.
25418
25419 Similarly, when Exim is looking for a retry rule after a local delivery has
25420 failed (for example, after a mailbox full error), each line in the retry
25421 configuration is tested against the complete address only if
25422 &%retry_use_local_part%& is set for the transport (it defaults true for all
25423 local transports).
25424
25425 .cindex "4&'xx'& responses" "retry rules for"
25426 However, when Exim is looking for a retry rule after a remote delivery attempt
25427 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
25428 whole address is always used as the key when searching the retry rules. The
25429 rule that is found is used to create a retry time for the combination of the
25430 failing address and the message's sender. It is the combination of sender and
25431 recipient that is delayed in subsequent queue runs until its retry time is
25432 reached. You can delay the recipient without regard to the sender by setting
25433 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
25434 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
25435 commands.
25436
25437
25438
25439 .section "Choosing which retry rule to use for host and message errors" &&&
25440 "SECID160"
25441 For a temporary error that is not related to an individual address (for
25442 example, a connection timeout), each line in the retry configuration is checked
25443 twice. First, the name of the remote host is used as a domain name (preceded by
25444 &"*@"& when matching a regular expression). If this does not match the line,
25445 the domain from the email address is tried in a similar fashion. For example,
25446 suppose the MX records for &'a.b.c.example'& are
25447 .code
25448 a.b.c.example MX 5 x.y.z.example
25449 MX 6 p.q.r.example
25450 MX 7 m.n.o.example
25451 .endd
25452 and the retry rules are
25453 .code
25454 p.q.r.example * F,24h,30m;
25455 a.b.c.example * F,4d,45m;
25456 .endd
25457 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
25458 first rule matches neither the host nor the domain, so Exim looks at the second
25459 rule. This does not match the host, but it does match the domain, so it is used
25460 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
25461 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
25462 first retry rule is used, because it matches the host.
25463
25464 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
25465 first rule to determine retry times, but for all the other hosts for the domain
25466 &'a.b.c.example'&, the second rule is used. The second rule is also used if
25467 routing to &'a.b.c.example'& suffers a temporary failure.
25468
25469 &*Note*&: The host name is used when matching the patterns, not its IP address.
25470 However, if a message is routed directly to an IP address without the use of a
25471 host name, for example, if a &(manualroute)& router contains a setting such as:
25472 .code
25473 route_list = *.a.example 192.168.34.23
25474 .endd
25475 then the &"host name"& that is used when searching for a retry rule is the
25476 textual form of the IP address.
25477
25478 .section "Retry rules for specific errors" "SECID161"
25479 .cindex "retry" "specific errors; specifying"
25480 The second field in a retry rule is the name of a particular error, or an
25481 asterisk, which matches any error. The errors that can be tested for are:
25482
25483 .vlist
25484 .vitem &%auth_failed%&
25485 Authentication failed when trying to send to a host in the
25486 &%hosts_require_auth%& list in an &(smtp)& transport.
25487
25488 .vitem &%data_4xx%&
25489 A 4&'xx'& error was received for an outgoing DATA command, either immediately
25490 after the command, or after sending the message's data.
25491
25492 .vitem &%mail_4xx%&
25493 A 4&'xx'& error was received for an outgoing MAIL command.
25494
25495 .vitem &%rcpt_4xx%&
25496 A 4&'xx'& error was received for an outgoing RCPT command.
25497 .endlist
25498
25499 For the three 4&'xx'& errors, either the first or both of the x's can be given
25500 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
25501 recognize 452 errors given to RCPT commands for addresses in a certain domain,
25502 and have retries every ten minutes with a one-hour timeout, you could set up a
25503 retry rule of this form:
25504 .code
25505 the.domain.name rcpt_452 F,1h,10m
25506 .endd
25507 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
25508 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
25509
25510 .vlist
25511 .vitem &%lost_connection%&
25512 A server unexpectedly closed the SMTP connection. There may, of course,
25513 legitimate reasons for this (host died, network died), but if it repeats a lot
25514 for the same host, it indicates something odd.
25515
25516 .vitem &%lookup%&
25517 A DNS lookup for a host failed.
25518 Note that a &%dnslookup%& router will need to have matched
25519 its &%fail_defer_domains%& option for this retry type to be usable.
25520 Also note that a &%manualroute%& router will probably need
25521 its &%host_find_failed%& option set to &%defer%&.
25522
25523 .vitem &%refused_MX%&
25524 A connection to a host obtained from an MX record was refused.
25525
25526 .vitem &%refused_A%&
25527 A connection to a host not obtained from an MX record was refused.
25528
25529 .vitem &%refused%&
25530 A connection was refused.
25531
25532 .vitem &%timeout_connect_MX%&
25533 A connection attempt to a host obtained from an MX record timed out.
25534
25535 .vitem &%timeout_connect_A%&
25536 A connection attempt to a host not obtained from an MX record timed out.
25537
25538 .vitem &%timeout_connect%&
25539 A connection attempt timed out.
25540
25541 .vitem &%timeout_MX%&
25542 There was a timeout while connecting or during an SMTP session with a host
25543 obtained from an MX record.
25544
25545 .vitem &%timeout_A%&
25546 There was a timeout while connecting or during an SMTP session with a host not
25547 obtained from an MX record.
25548
25549 .vitem &%timeout%&
25550 There was a timeout while connecting or during an SMTP session.
25551
25552 .vitem &%tls_required%&
25553 The server was required to use TLS (it matched &%hosts_require_tls%& in the
25554 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
25555 to STARTTLS, or there was a problem setting up the TLS connection.
25556
25557 .vitem &%quota%&
25558 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
25559 transport.
25560
25561 .vitem &%quota_%&<&'time'&>
25562 .cindex "quota" "error testing in retry rule"
25563 .cindex "retry" "quota error testing"
25564 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
25565 transport, and the mailbox has not been accessed for <&'time'&>. For example,
25566 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
25567 for four days.
25568 .endlist
25569
25570 .cindex "mailbox" "time of last read"
25571 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
25572 timeouts when the mailbox is full and is not being read by its owner. Ideally,
25573 it should be based on the last time that the user accessed the mailbox.
25574 However, it is not always possible to determine this. Exim uses the following
25575 heuristic rules:
25576
25577 .ilist
25578 If the mailbox is a single file, the time of last access (the &"atime"&) is
25579 used. As no new messages are being delivered (because the mailbox is over
25580 quota), Exim does not access the file, so this is the time of last user access.
25581 .next
25582 .cindex "maildir format" "time of last read"
25583 For a maildir delivery, the time of last modification of the &_new_&
25584 subdirectory is used. As the mailbox is over quota, no new files are created in
25585 the &_new_& subdirectory, because no new messages are being delivered. Any
25586 change to the &_new_& subdirectory is therefore assumed to be the result of an
25587 MUA moving a new message to the &_cur_& directory when it is first read. The
25588 time that is used is therefore the last time that the user read a new message.
25589 .next
25590 For other kinds of multi-file mailbox, the time of last access cannot be
25591 obtained, so a retry rule that uses this type of error field is never matched.
25592 .endlist
25593
25594 The quota errors apply both to system-enforced quotas and to Exim's own quota
25595 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
25596 when a local delivery is deferred because a partition is full (the ENOSPC
25597 error).
25598
25599
25600
25601 .section "Retry rules for specified senders" "SECID162"
25602 .cindex "retry" "rules; sender-specific"
25603 You can specify retry rules that apply only when the failing message has a
25604 specific sender. In particular, this can be used to define retry rules that
25605 apply only to bounce messages. The third item in a retry rule can be of this
25606 form:
25607 .display
25608 &`senders=`&<&'address list'&>
25609 .endd
25610 The retry timings themselves are then the fourth item. For example:
25611 .code
25612 * rcpt_4xx senders=: F,1h,30m
25613 .endd
25614 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
25615 host. If the address list contains white space, it must be enclosed in quotes.
25616 For example:
25617 .code
25618 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
25619 .endd
25620 &*Warning*&: This facility can be unhelpful if it is used for host errors
25621 (which do not depend on the recipient). The reason is that the sender is used
25622 only to match the retry rule. Once the rule has been found for a host error,
25623 its contents are used to set a retry time for the host, and this will apply to
25624 all messages, not just those with specific senders.
25625
25626 When testing retry rules using &%-brt%&, you can supply a sender using the
25627 &%-f%& command line option, like this:
25628 .code
25629 exim -f "" -brt user@dom.ain
25630 .endd
25631 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
25632 list is never matched.
25633
25634
25635
25636
25637
25638 .section "Retry parameters" "SECID163"
25639 .cindex "retry" "parameters in rules"
25640 The third (or fourth, if a senders list is present) field in a retry rule is a
25641 sequence of retry parameter sets, separated by semicolons. Each set consists of
25642 .display
25643 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
25644 .endd
25645 The letter identifies the algorithm for computing a new retry time; the cutoff
25646 time is the time beyond which this algorithm no longer applies, and the
25647 arguments vary the algorithm's action. The cutoff time is measured from the
25648 time that the first failure for the domain (combined with the local part if
25649 relevant) was detected, not from the time the message was received.
25650
25651 .cindex "retry" "algorithms"
25652 .cindex "retry" "fixed intervals"
25653 .cindex "retry" "increasing intervals"
25654 .cindex "retry" "random intervals"
25655 The available algorithms are:
25656
25657 .ilist
25658 &'F'&: retry at fixed intervals. There is a single time parameter specifying
25659 the interval.
25660 .next
25661 &'G'&: retry at geometrically increasing intervals. The first argument
25662 specifies a starting value for the interval, and the second a multiplier, which
25663 is used to increase the size of the interval at each retry.
25664 .next
25665 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
25666 retry, the previous interval is multiplied by the factor in order to get a
25667 maximum for the next interval. The minimum interval is the first argument of
25668 the parameter, and an actual interval is chosen randomly between them. Such a
25669 rule has been found to be helpful in cluster configurations when all the
25670 members of the cluster restart at once, and may therefore synchronize their
25671 queue processing times.
25672 .endlist
25673
25674 When computing the next retry time, the algorithm definitions are scanned in
25675 order until one whose cutoff time has not yet passed is reached. This is then
25676 used to compute a new retry time that is later than the current time. In the
25677 case of fixed interval retries, this simply means adding the interval to the
25678 current time. For geometrically increasing intervals, retry intervals are
25679 computed from the rule's parameters until one that is greater than the previous
25680 interval is found. The main configuration variable
25681 .cindex "limit" "retry interval"
25682 .cindex "retry" "interval, maximum"
25683 .oindex "&%retry_interval_max%&"
25684 &%retry_interval_max%& limits the maximum interval between retries. It
25685 cannot be set greater than &`24h`&, which is its default value.
25686
25687 A single remote domain may have a number of hosts associated with it, and each
25688 host may have more than one IP address. Retry algorithms are selected on the
25689 basis of the domain name, but are applied to each IP address independently. If,
25690 for example, a host has two IP addresses and one is unusable, Exim will
25691 generate retry times for it and will not try to use it until its next retry
25692 time comes. Thus the good IP address is likely to be tried first most of the
25693 time.
25694
25695 .cindex "hints database" "use for retrying"
25696 Retry times are hints rather than promises. Exim does not make any attempt to
25697 run deliveries exactly at the computed times. Instead, a queue runner process
25698 starts delivery processes for delayed messages periodically, and these attempt
25699 new deliveries only for those addresses that have passed their next retry time.
25700 If a new message arrives for a deferred address, an immediate delivery attempt
25701 occurs only if the address has passed its retry time. In the absence of new
25702 messages, the minimum time between retries is the interval between queue runner
25703 processes. There is not much point in setting retry times of five minutes if
25704 your queue runners happen only once an hour, unless there are a significant
25705 number of incoming messages (which might be the case on a system that is
25706 sending everything to a smart host, for example).
25707
25708 The data in the retry hints database can be inspected by using the
25709 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
25710 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
25711 &'exinext'& utility script can be used to find out what the next retry times
25712 are for the hosts associated with a particular mail domain, and also for local
25713 deliveries that have been deferred.
25714
25715
25716 .section "Retry rule examples" "SECID164"
25717 Here are some example retry rules:
25718 .code
25719 alice@wonderland.fict.example quota_5d F,7d,3h
25720 wonderland.fict.example quota_5d
25721 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
25722 lookingglass.fict.example * F,24h,30m;
25723 * refused_A F,2h,20m;
25724 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
25725 .endd
25726 The first rule sets up special handling for mail to
25727 &'alice@wonderland.fict.example'& when there is an over-quota error and the
25728 mailbox has not been read for at least 5 days. Retries continue every three
25729 hours for 7 days. The second rule handles over-quota errors for all other local
25730 parts at &'wonderland.fict.example'&; the absence of a local part has the same
25731 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
25732 fail are bounced immediately if the mailbox has not been read for at least 5
25733 days.
25734
25735 The third rule handles all other errors at &'wonderland.fict.example'&; retries
25736 happen every 15 minutes for an hour, then with geometrically increasing
25737 intervals until two days have passed since a delivery first failed. After the
25738 first hour there is a delay of one hour, then two hours, then four hours, and
25739 so on (this is a rather extreme example).
25740
25741 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
25742 They happen every 30 minutes for 24 hours only. The remaining two rules handle
25743 all other domains, with special action for connection refusal from hosts that
25744 were not obtained from an MX record.
25745
25746 The final rule in a retry configuration should always have asterisks in the
25747 first two fields so as to provide a general catch-all for any addresses that do
25748 not have their own special handling. This example tries every 15 minutes for 2
25749 hours, then with intervals starting at one hour and increasing by a factor of
25750 1.5 up to 16 hours, then every 8 hours up to 5 days.
25751
25752
25753
25754 .section "Timeout of retry data" "SECID165"
25755 .cindex "timeout" "of retry data"
25756 .oindex "&%retry_data_expire%&"
25757 .cindex "hints database" "data expiry"
25758 .cindex "retry" "timeout of data"
25759 Exim timestamps the data that it writes to its retry hints database. When it
25760 consults the data during a delivery it ignores any that is older than the value
25761 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
25762 been tried for 7 days, Exim will try to deliver to it immediately a message
25763 arrives, and if that fails, it will calculate a retry time as if it were
25764 failing for the first time.
25765
25766 This improves the behaviour for messages routed to rarely-used hosts such as MX
25767 backups. If such a host was down at one time, and happens to be down again when
25768 Exim tries a month later, using the old retry data would imply that it had been
25769 down all the time, which is not a justified assumption.
25770
25771 If a host really is permanently dead, this behaviour causes a burst of retries
25772 every now and again, but only if messages routed to it are rare. If there is a
25773 message at least once every 7 days the retry data never expires.
25774
25775
25776
25777
25778 .section "Long-term failures" "SECID166"
25779 .cindex "delivery failure, long-term"
25780 .cindex "retry" "after long-term failure"
25781 Special processing happens when an email address has been failing for so long
25782 that the cutoff time for the last algorithm is reached. For example, using the
25783 default retry rule:
25784 .code
25785 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
25786 .endd
25787 the cutoff time is four days. Reaching the retry cutoff is independent of how
25788 long any specific message has been failing; it is the length of continuous
25789 failure for the recipient address that counts.
25790
25791 When the cutoff time is reached for a local delivery, or for all the IP
25792 addresses associated with a remote delivery, a subsequent delivery failure
25793 causes Exim to give up on the address, and a bounce message is generated.
25794 In order to cater for new messages that use the failing address, a next retry
25795 time is still computed from the final algorithm, and is used as follows:
25796
25797 For local deliveries, one delivery attempt is always made for any subsequent
25798 messages. If this delivery fails, the address fails immediately. The
25799 post-cutoff retry time is not used.
25800
25801 If the delivery is remote, there are two possibilities, controlled by the
25802 .oindex "&%delay_after_cutoff%&"
25803 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
25804 default. Until the post-cutoff retry time for one of the IP addresses is
25805 reached, the failing email address is bounced immediately, without a delivery
25806 attempt taking place. After that time, one new delivery attempt is made to
25807 those IP addresses that are past their retry times, and if that still fails,
25808 the address is bounced and new retry times are computed.
25809
25810 In other words, when all the hosts for a given email address have been failing
25811 for a long time, Exim bounces rather then defers until one of the hosts' retry
25812 times is reached. Then it tries once, and bounces if that attempt fails. This
25813 behaviour ensures that few resources are wasted in repeatedly trying to deliver
25814 to a broken destination, but if the host does recover, Exim will eventually
25815 notice.
25816
25817 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
25818 addresses are past their final cutoff time, Exim tries to deliver to those IP
25819 addresses that have not been tried since the message arrived. If there are
25820 no suitable IP addresses, or if they all fail, the address is bounced. In other
25821 words, it does not delay when a new message arrives, but tries the expired
25822 addresses immediately, unless they have been tried since the message arrived.
25823 If there is a continuous stream of messages for the failing domains, setting
25824 &%delay_after_cutoff%& false means that there will be many more attempts to
25825 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
25826 true.
25827
25828 .section "Deliveries that work intermittently" "SECID167"
25829 .cindex "retry" "intermittently working deliveries"
25830 Some additional logic is needed to cope with cases where a host is
25831 intermittently available, or when a message has some attribute that prevents
25832 its delivery when others to the same address get through. In this situation,
25833 because some messages are successfully delivered, the &"retry clock"& for the
25834 host or address keeps getting reset by the successful deliveries, and so
25835 failing messages remain on the queue for ever because the cutoff time is never
25836 reached.
25837
25838 Two exceptional actions are applied to prevent this happening. The first
25839 applies to errors that are related to a message rather than a remote host.
25840 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
25841 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
25842 commands, and quota failures. For this type of error, if a message's arrival
25843 time is earlier than the &"first failed"& time for the error, the earlier time
25844 is used when scanning the retry rules to decide when to try next and when to
25845 time out the address.
25846
25847 The exceptional second action applies in all cases. If a message has been on
25848 the queue for longer than the cutoff time of any applicable retry rule for a
25849 given address, a delivery is attempted for that address, even if it is not yet
25850 time, and if this delivery fails, the address is timed out. A new retry time is
25851 not computed in this case, so that other messages for the same address are
25852 considered immediately.
25853 .ecindex IIDretconf1
25854 .ecindex IIDregconf2
25855
25856
25857
25858
25859
25860
25861 . ////////////////////////////////////////////////////////////////////////////
25862 . ////////////////////////////////////////////////////////////////////////////
25863
25864 .chapter "SMTP authentication" "CHAPSMTPAUTH"
25865 .scindex IIDauthconf1 "SMTP" "authentication configuration"
25866 .scindex IIDauthconf2 "authentication"
25867 The &"authenticators"& section of Exim's run time configuration is concerned
25868 with SMTP authentication. This facility is an extension to the SMTP protocol,
25869 described in RFC 2554, which allows a client SMTP host to authenticate itself
25870 to a server. This is a common way for a server to recognize clients that are
25871 permitted to use it as a relay. SMTP authentication is not of relevance to the
25872 transfer of mail between servers that have no managerial connection with each
25873 other.
25874
25875 .cindex "AUTH" "description of"
25876 Very briefly, the way SMTP authentication works is as follows:
25877
25878 .ilist
25879 The server advertises a number of authentication &'mechanisms'& in response to
25880 the client's EHLO command.
25881 .next
25882 The client issues an AUTH command, naming a specific mechanism. The command
25883 may, optionally, contain some authentication data.
25884 .next
25885 The server may issue one or more &'challenges'&, to which the client must send
25886 appropriate responses. In simple authentication mechanisms, the challenges are
25887 just prompts for user names and passwords. The server does not have to issue
25888 any challenges &-- in some mechanisms the relevant data may all be transmitted
25889 with the AUTH command.
25890 .next
25891 The server either accepts or denies authentication.
25892 .next
25893 If authentication succeeds, the client may optionally make use of the AUTH
25894 option on the MAIL command to pass an authenticated sender in subsequent
25895 mail transactions. Authentication lasts for the remainder of the SMTP
25896 connection.
25897 .next
25898 If authentication fails, the client may give up, or it may try a different
25899 authentication mechanism, or it may try transferring mail over the
25900 unauthenticated connection.
25901 .endlist
25902
25903 If you are setting up a client, and want to know which authentication
25904 mechanisms the server supports, you can use Telnet to connect to port 25 (the
25905 SMTP port) on the server, and issue an EHLO command. The response to this
25906 includes the list of supported mechanisms. For example:
25907 .display
25908 &`$ `&&*&`telnet server.example 25`&*&
25909 &`Trying 192.168.34.25...`&
25910 &`Connected to server.example.`&
25911 &`Escape character is &#x0027;^]&#x0027;.`&
25912 &`220 server.example ESMTP Exim 4.20 ...`&
25913 &*&`ehlo client.example`&*&
25914 &`250-server.example Hello client.example [10.8.4.5]`&
25915 &`250-SIZE 52428800`&
25916 &`250-PIPELINING`&
25917 &`250-AUTH PLAIN`&
25918 &`250 HELP`&
25919 .endd
25920 The second-last line of this example output shows that the server supports
25921 authentication using the PLAIN mechanism. In Exim, the different authentication
25922 mechanisms are configured by specifying &'authenticator'& drivers. Like the
25923 routers and transports, which authenticators are included in the binary is
25924 controlled by build-time definitions. The following are currently available,
25925 included by setting
25926 .code
25927 AUTH_CRAM_MD5=yes
25928 AUTH_CYRUS_SASL=yes
25929 AUTH_DOVECOT=yes
25930 AUTH_GSASL=yes
25931 AUTH_HEIMDAL_GSSAPI=yes
25932 AUTH_PLAINTEXT=yes
25933 AUTH_SPA=yes
25934 AUTH_TLS=yes
25935 .endd
25936 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
25937 authentication mechanism (RFC 2195), and the second provides an interface to
25938 the Cyrus SASL authentication library.
25939 The third is an interface to Dovecot's authentication system, delegating the
25940 work via a socket interface.
25941 The fourth provides an interface to the GNU SASL authentication library, which
25942 provides mechanisms but typically not data sources.
25943 The fifth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
25944 supporting setting a server keytab.
25945 The sixth can be configured to support
25946 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
25947 not formally documented, but used by several MUAs. The seventh authenticator
25948 supports Microsoft's &'Secure Password Authentication'& mechanism.
25949 The eighth is an Exim authenticator but not an SMTP one;
25950 instead it can use information from a TLS negotiation.
25951
25952 The authenticators are configured using the same syntax as other drivers (see
25953 section &<<SECTfordricon>>&). If no authenticators are required, no
25954 authentication section need be present in the configuration file. Each
25955 authenticator can in principle have both server and client functions. When Exim
25956 is receiving SMTP mail, it is acting as a server; when it is sending out
25957 messages over SMTP, it is acting as a client. Authenticator configuration
25958 options are provided for use in both these circumstances.
25959
25960 To make it clear which options apply to which situation, the prefixes
25961 &%server_%& and &%client_%& are used on option names that are specific to
25962 either the server or the client function, respectively. Server and client
25963 functions are disabled if none of their options are set. If an authenticator is
25964 to be used for both server and client functions, a single definition, using
25965 both sets of options, is required. For example:
25966 .code
25967 cram:
25968 driver = cram_md5
25969 public_name = CRAM-MD5
25970 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
25971 client_name = ph10
25972 client_secret = secret2
25973 .endd
25974 The &%server_%& option is used when Exim is acting as a server, and the
25975 &%client_%& options when it is acting as a client.
25976
25977 Descriptions of the individual authenticators are given in subsequent chapters.
25978 The remainder of this chapter covers the generic options for the
25979 authenticators, followed by general discussion of the way authentication works
25980 in Exim.
25981
25982 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
25983 per-mechanism basis. Please read carefully to determine which variables hold
25984 account labels such as usercodes and which hold passwords or other
25985 authenticating data.
25986
25987 Note that some mechanisms support two different identifiers for accounts: the
25988 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
25989 and &'authz'& are commonly encountered. The American spelling is standard here.
25990 Conceptually, authentication data such as passwords are tied to the identifier
25991 used to authenticate; servers may have rules to permit one user to act as a
25992 second user, so that after login the session is treated as though that second
25993 user had logged in. That second user is the &'authorization id'&. A robust
25994 configuration might confirm that the &'authz'& field is empty or matches the
25995 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
25996 as verified data, the &'authz'& as an unverified request which the server might
25997 choose to honour.
25998
25999 A &'realm'& is a text string, typically a domain name, presented by a server
26000 to a client to help it select an account and credentials to use. In some
26001 mechanisms, the client and server provably agree on the realm, but clients
26002 typically can not treat the realm as secure data to be blindly trusted.
26003
26004
26005
26006 .section "Generic options for authenticators" "SECID168"
26007 .cindex "authentication" "generic options"
26008 .cindex "options" "generic; for authenticators"
26009
26010 .option client_condition authenticators string&!! unset
26011 When Exim is authenticating as a client, it skips any authenticator whose
26012 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
26013 used, for example, to skip plain text authenticators when the connection is not
26014 encrypted by a setting such as:
26015 .code
26016 client_condition = ${if !eq{$tls_out_cipher}{}}
26017 .endd
26018
26019
26020 .option client_set_id authenticators string&!! unset
26021 When client authentication succeeds, this condition is expanded; the
26022 result is used in the log lines for outbound messages.
26023 Typically it will be the user name used for authentication.
26024
26025
26026 .option driver authenticators string unset
26027 This option must always be set. It specifies which of the available
26028 authenticators is to be used.
26029
26030
26031 .option public_name authenticators string unset
26032 This option specifies the name of the authentication mechanism that the driver
26033 implements, and by which it is known to the outside world. These names should
26034 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
26035 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
26036 defaults to the driver's instance name.
26037
26038
26039 .option server_advertise_condition authenticators string&!! unset
26040 When a server is about to advertise an authentication mechanism, the condition
26041 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
26042 mechanism is not advertised.
26043 If the expansion fails, the mechanism is not advertised. If the failure was not
26044 forced, and was not caused by a lookup defer, the incident is logged.
26045 See section &<<SECTauthexiser>>& below for further discussion.
26046
26047
26048 .option server_condition authenticators string&!! unset
26049 This option must be set for a &%plaintext%& server authenticator, where it
26050 is used directly to control authentication. See section &<<SECTplainserver>>&
26051 for details.
26052
26053 For the &(gsasl)& authenticator, this option is required for various
26054 mechanisms; see chapter &<<CHAPgsasl>>& for details.
26055
26056 For the other authenticators, &%server_condition%& can be used as an additional
26057 authentication or authorization mechanism that is applied after the other
26058 authenticator conditions succeed. If it is set, it is expanded when the
26059 authenticator would otherwise return a success code. If the expansion is forced
26060 to fail, authentication fails. Any other expansion failure causes a temporary
26061 error code to be returned. If the result of a successful expansion is an empty
26062 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
26063 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
26064 other result, a temporary error code is returned, with the expanded string as
26065 the error text.
26066
26067
26068 .option server_debug_print authenticators string&!! unset
26069 If this option is set and authentication debugging is enabled (see the &%-d%&
26070 command line option), the string is expanded and included in the debugging
26071 output when the authenticator is run as a server. This can help with checking
26072 out the values of variables.
26073 If expansion of the string fails, the error message is written to the debugging
26074 output, and Exim carries on processing.
26075
26076
26077 .option server_set_id authenticators string&!! unset
26078 .vindex "&$authenticated_id$&"
26079 When an Exim server successfully authenticates a client, this string is
26080 expanded using data from the authentication, and preserved for any incoming
26081 messages in the variable &$authenticated_id$&. It is also included in the log
26082 lines for incoming messages. For example, a user/password authenticator
26083 configuration might preserve the user name that was used to authenticate, and
26084 refer to it subsequently during delivery of the message.
26085 If expansion fails, the option is ignored.
26086
26087
26088 .option server_mail_auth_condition authenticators string&!! unset
26089 This option allows a server to discard authenticated sender addresses supplied
26090 as part of MAIL commands in SMTP connections that are authenticated by the
26091 driver on which &%server_mail_auth_condition%& is set. The option is not used
26092 as part of the authentication process; instead its (unexpanded) value is
26093 remembered for later use.
26094 How it is used is described in the following section.
26095
26096
26097
26098
26099
26100 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
26101 .cindex "authentication" "sender; authenticated"
26102 .cindex "AUTH" "on MAIL command"
26103 When a client supplied an AUTH= item on a MAIL command, Exim applies
26104 the following checks before accepting it as the authenticated sender of the
26105 message:
26106
26107 .ilist
26108 If the connection is not using extended SMTP (that is, HELO was used rather
26109 than EHLO), the use of AUTH= is a syntax error.
26110 .next
26111 If the value of the AUTH= parameter is &"<>"&, it is ignored.
26112 .next
26113 .vindex "&$authenticated_sender$&"
26114 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
26115 running, the value of &$authenticated_sender$& is set to the value obtained
26116 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
26117 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
26118 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
26119 given for the MAIL command.
26120 .next
26121 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
26122 is accepted and placed in &$authenticated_sender$& only if the client has
26123 authenticated.
26124 .next
26125 If the AUTH= value was accepted by either of the two previous rules, and
26126 the client has authenticated, and the authenticator has a setting for the
26127 &%server_mail_auth_condition%&, the condition is checked at this point. The
26128 valued that was saved from the authenticator is expanded. If the expansion
26129 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
26130 &$authenticated_sender$& is deleted. If the expansion yields any other value,
26131 the value of &$authenticated_sender$& is retained and passed on with the
26132 message.
26133 .endlist
26134
26135
26136 When &$authenticated_sender$& is set for a message, it is passed on to other
26137 hosts to which Exim authenticates as a client. Do not confuse this value with
26138 &$authenticated_id$&, which is a string obtained from the authentication
26139 process, and which is not usually a complete email address.
26140
26141 .vindex "&$sender_address$&"
26142 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
26143 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
26144 therefore make use of &$authenticated_sender$&. The converse is not true: the
26145 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
26146 ACL is run.
26147
26148
26149
26150 .section "Authentication on an Exim server" "SECTauthexiser"
26151 .cindex "authentication" "on an Exim server"
26152 When Exim receives an EHLO command, it advertises the public names of those
26153 authenticators that are configured as servers, subject to the following
26154 conditions:
26155
26156 .ilist
26157 The client host must match &%auth_advertise_hosts%& (default *).
26158 .next
26159 It the &%server_advertise_condition%& option is set, its expansion must not
26160 yield the empty string, &"0"&, &"no"&, or &"false"&.
26161 .endlist
26162
26163 The order in which the authenticators are defined controls the order in which
26164 the mechanisms are advertised.
26165
26166 Some mail clients (for example, some versions of Netscape) require the user to
26167 provide a name and password for authentication whenever AUTH is advertised,
26168 even though authentication may not in fact be needed (for example, Exim may be
26169 set up to allow unconditional relaying from the client by an IP address check).
26170 You can make such clients more friendly by not advertising AUTH to them.
26171 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
26172 that runs for RCPT) to relay without authentication, you should set
26173 .code
26174 auth_advertise_hosts = ! 10.9.8.0/24
26175 .endd
26176 so that no authentication mechanisms are advertised to them.
26177
26178 The &%server_advertise_condition%& controls the advertisement of individual
26179 authentication mechanisms. For example, it can be used to restrict the
26180 advertisement of a particular mechanism to encrypted connections, by a setting
26181 such as:
26182 .code
26183 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
26184 .endd
26185 .vindex "&$tls_in_cipher$&"
26186 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
26187 yields &"yes"&, which allows the advertisement to happen.
26188
26189 When an Exim server receives an AUTH command from a client, it rejects it
26190 immediately if AUTH was not advertised in response to an earlier EHLO
26191 command. This is the case if
26192
26193 .ilist
26194 The client host does not match &%auth_advertise_hosts%&; or
26195 .next
26196 No authenticators are configured with server options; or
26197 .next
26198 Expansion of &%server_advertise_condition%& blocked the advertising of all the
26199 server authenticators.
26200 .endlist
26201
26202
26203 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
26204 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
26205 AUTH is accepted from any client host.
26206
26207 If AUTH is not rejected by the ACL, Exim searches its configuration for a
26208 server authentication mechanism that was advertised in response to EHLO and
26209 that matches the one named in the AUTH command. If it finds one, it runs
26210 the appropriate authentication protocol, and authentication either succeeds or
26211 fails. If there is no matching advertised mechanism, the AUTH command is
26212 rejected with a 504 error.
26213
26214 .vindex "&$received_protocol$&"
26215 .vindex "&$sender_host_authenticated$&"
26216 When a message is received from an authenticated host, the value of
26217 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
26218 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
26219 public name) of the authenticator driver that successfully authenticated the
26220 client from which the message was received. This variable is empty if there was
26221 no successful authentication.
26222
26223 .cindex authentication "expansion item"
26224 Successful authentication sets up information used by the
26225 &$authresults$& expansion item.
26226
26227
26228
26229
26230 .section "Testing server authentication" "SECID169"
26231 .cindex "authentication" "testing a server"
26232 .cindex "AUTH" "testing a server"
26233 .cindex "base64 encoding" "creating authentication test data"
26234 Exim's &%-bh%& option can be useful for testing server authentication
26235 configurations. The data for the AUTH command has to be sent using base64
26236 encoding. A quick way to produce such data for testing is the following Perl
26237 script:
26238 .code
26239 use MIME::Base64;
26240 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
26241 .endd
26242 .cindex "binary zero" "in authentication data"
26243 This interprets its argument as a Perl string, and then encodes it. The
26244 interpretation as a Perl string allows binary zeros, which are required for
26245 some kinds of authentication, to be included in the data. For example, a
26246 command line to run this script on such data might be
26247 .code
26248 encode '\0user\0password'
26249 .endd
26250 Note the use of single quotes to prevent the shell interpreting the
26251 backslashes, so that they can be interpreted by Perl to specify characters
26252 whose code value is zero.
26253
26254 &*Warning 1*&: If either of the user or password strings starts with an octal
26255 digit, you must use three zeros instead of one after the leading backslash. If
26256 you do not, the octal digit that starts your string will be incorrectly
26257 interpreted as part of the code for the first character.
26258
26259 &*Warning 2*&: If there are characters in the strings that Perl interprets
26260 specially, you must use a Perl escape to prevent them being misinterpreted. For
26261 example, a command such as
26262 .code
26263 encode '\0user@domain.com\0pas$$word'
26264 .endd
26265 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
26266
26267 If you have the &%mimencode%& command installed, another way to do produce
26268 base64-encoded strings is to run the command
26269 .code
26270 echo -e -n `\0user\0password' | mimencode
26271 .endd
26272 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
26273 in the argument, and the &%-n%& option specifies no newline at the end of its
26274 output. However, not all versions of &%echo%& recognize these options, so you
26275 should check your version before relying on this suggestion.
26276
26277
26278
26279 .section "Authentication by an Exim client" "SECID170"
26280 .cindex "authentication" "on an Exim client"
26281 The &(smtp)& transport has two options called &%hosts_require_auth%& and
26282 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
26283 announces support for authentication, and the host matches an entry in either
26284 of these options, Exim (as a client) tries to authenticate as follows:
26285
26286 .ilist
26287 For each authenticator that is configured as a client, in the order in which
26288 they are defined in the configuration, it searches the authentication
26289 mechanisms announced by the server for one whose name matches the public name
26290 of the authenticator.
26291 .next
26292 .vindex "&$host$&"
26293 .vindex "&$host_address$&"
26294 When it finds one that matches, it runs the authenticator's client code. The
26295 variables &$host$& and &$host_address$& are available for any string expansions
26296 that the client might do. They are set to the server's name and IP address. If
26297 any expansion is forced to fail, the authentication attempt is abandoned, and
26298 Exim moves on to the next authenticator. Otherwise an expansion failure causes
26299 delivery to be deferred.
26300 .next
26301 If the result of the authentication attempt is a temporary error or a timeout,
26302 Exim abandons trying to send the message to the host for the moment. It will
26303 try again later. If there are any backup hosts available, they are tried in the
26304 usual way.
26305 .next
26306 If the response to authentication is a permanent error (5&'xx'& code), Exim
26307 carries on searching the list of authenticators and tries another one if
26308 possible. If all authentication attempts give permanent errors, or if there are
26309 no attempts because no mechanisms match (or option expansions force failure),
26310 what happens depends on whether the host matches &%hosts_require_auth%& or
26311 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
26312 delivery is deferred. The error can be detected in the retry rules, and thereby
26313 turned into a permanent error if you wish. In the second case, Exim tries to
26314 deliver the message unauthenticated.
26315 .endlist
26316
26317 Note that the hostlist test for whether to do authentication can be
26318 confused if name-IP lookups change between the time the peer is decided
26319 upon and the time that the transport runs. For example, with a manualroute
26320 router given a host name, and with DNS "round-robin" used by that name: if
26321 the local resolver cache times out between the router and the transport
26322 running, the transport may get an IP for the name for its authentication
26323 check which does not match the connection peer IP.
26324 No authentication will then be done, despite the names being identical.
26325
26326 For such cases use a separate transport which always authenticates.
26327
26328 .cindex "AUTH" "on MAIL command"
26329 When Exim has authenticated itself to a remote server, it adds the AUTH
26330 parameter to the MAIL commands it sends, if it has an authenticated sender for
26331 the message. If the message came from a remote host, the authenticated sender
26332 is the one that was receiving on an incoming MAIL command, provided that the
26333 incoming connection was authenticated and the &%server_mail_auth%& condition
26334 allowed the authenticated sender to be retained. If a local process calls Exim
26335 to send a message, the sender address that is built from the login name and
26336 &%qualify_domain%& is treated as authenticated. However, if the
26337 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
26338 the authenticated sender that was received with the message.
26339 .ecindex IIDauthconf1
26340 .ecindex IIDauthconf2
26341
26342
26343
26344
26345
26346
26347 . ////////////////////////////////////////////////////////////////////////////
26348 . ////////////////////////////////////////////////////////////////////////////
26349
26350 .chapter "The plaintext authenticator" "CHAPplaintext"
26351 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
26352 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
26353 The &(plaintext)& authenticator can be configured to support the PLAIN and
26354 LOGIN authentication mechanisms, both of which transfer authentication data as
26355 plain (unencrypted) text (though base64 encoded). The use of plain text is a
26356 security risk; you are strongly advised to insist on the use of SMTP encryption
26357 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
26358 use unencrypted plain text, you should not use the same passwords for SMTP
26359 connections as you do for login accounts.
26360
26361 .section "Plaintext options" "SECID171"
26362 .cindex "options" "&(plaintext)& authenticator (server)"
26363 When configured as a server, &(plaintext)& uses the following options:
26364
26365 .option server_condition authenticators string&!! unset
26366 This is actually a global authentication option, but it must be set in order to
26367 configure the &(plaintext)& driver as a server. Its use is described below.
26368
26369 .option server_prompts plaintext string&!! unset
26370 The contents of this option, after expansion, must be a colon-separated list of
26371 prompt strings. If expansion fails, a temporary authentication rejection is
26372 given.
26373
26374 .section "Using plaintext in a server" "SECTplainserver"
26375 .cindex "AUTH" "in &(plaintext)& authenticator"
26376 .cindex "binary zero" "in &(plaintext)& authenticator"
26377 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
26378 "in &(plaintext)& authenticator"
26379 .vindex "&$auth1$&, &$auth2$&, etc"
26380 .cindex "base64 encoding" "in &(plaintext)& authenticator"
26381
26382 When running as a server, &(plaintext)& performs the authentication test by
26383 expanding a string. The data sent by the client with the AUTH command, or in
26384 response to subsequent prompts, is base64 encoded, and so may contain any byte
26385 values when decoded. If any data is supplied with the command, it is treated as
26386 a list of strings, separated by NULs (binary zeros), the first three of which
26387 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
26388 (neither LOGIN nor PLAIN uses more than three strings).
26389
26390 For compatibility with previous releases of Exim, the values are also placed in
26391 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
26392 variables for this purpose is now deprecated, as it can lead to confusion in
26393 string expansions that also use them for other things.
26394
26395 If there are more strings in &%server_prompts%& than the number of strings
26396 supplied with the AUTH command, the remaining prompts are used to obtain more
26397 data. Each response from the client may be a list of NUL-separated strings.
26398
26399 .vindex "&$authenticated_id$&"
26400 Once a sufficient number of data strings have been received,
26401 &%server_condition%& is expanded. If the expansion is forced to fail,
26402 authentication fails. Any other expansion failure causes a temporary error code
26403 to be returned. If the result of a successful expansion is an empty string,
26404 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
26405 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
26406 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
26407 For any other result, a temporary error code is returned, with the expanded
26408 string as the error text
26409
26410 &*Warning*&: If you use a lookup in the expansion to find the user's
26411 password, be sure to make the authentication fail if the user is unknown.
26412 There are good and bad examples at the end of the next section.
26413
26414
26415
26416 .section "The PLAIN authentication mechanism" "SECID172"
26417 .cindex "PLAIN authentication mechanism"
26418 .cindex "authentication" "PLAIN mechanism"
26419 .cindex "binary zero" "in &(plaintext)& authenticator"
26420 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
26421 sent as one item of data (that is, one combined string containing two NUL
26422 separators). The data is sent either as part of the AUTH command, or
26423 subsequently in response to an empty prompt from the server.
26424
26425 The second and third strings are a user name and a corresponding password.
26426 Using a single fixed user name and password as an example, this could be
26427 configured as follows:
26428 .code
26429 fixed_plain:
26430 driver = plaintext
26431 public_name = PLAIN
26432 server_prompts = :
26433 server_condition = \
26434 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
26435 server_set_id = $auth2
26436 .endd
26437 Note that the default result strings from &%if%& (&"true"& or an empty string)
26438 are exactly what we want here, so they need not be specified. Obviously, if the
26439 password contains expansion-significant characters such as dollar, backslash,
26440 or closing brace, they have to be escaped.
26441
26442 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
26443 the end of a string list are ignored). If all the data comes as part of the
26444 AUTH command, as is commonly the case, the prompt is not used. This
26445 authenticator is advertised in the response to EHLO as
26446 .code
26447 250-AUTH PLAIN
26448 .endd
26449 and a client host can authenticate itself by sending the command
26450 .code
26451 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
26452 .endd
26453 As this contains three strings (more than the number of prompts), no further
26454 data is required from the client. Alternatively, the client may just send
26455 .code
26456 AUTH PLAIN
26457 .endd
26458 to initiate authentication, in which case the server replies with an empty
26459 prompt. The client must respond with the combined data string.
26460
26461 The data string is base64 encoded, as required by the RFC. This example,
26462 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
26463 represents a zero byte. This is split up into three strings, the first of which
26464 is empty. The &%server_condition%& option in the authenticator checks that the
26465 second two are &`username`& and &`mysecret`& respectively.
26466
26467 Having just one fixed user name and password, as in this example, is not very
26468 realistic, though for a small organization with only a handful of
26469 authenticating clients it could make sense.
26470
26471 A more sophisticated instance of this authenticator could use the user name in
26472 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
26473 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
26474 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
26475 This is an incorrect example:
26476 .code
26477 server_condition = \
26478 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
26479 .endd
26480 The expansion uses the user name (&$auth2$&) as the key to look up a password,
26481 which it then compares to the supplied password (&$auth3$&). Why is this example
26482 incorrect? It works fine for existing users, but consider what happens if a
26483 non-existent user name is given. The lookup fails, but as no success/failure
26484 strings are given for the lookup, it yields an empty string. Thus, to defeat
26485 the authentication, all a client has to do is to supply a non-existent user
26486 name and an empty password. The correct way of writing this test is:
26487 .code
26488 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
26489 {${if eq{$value}{$auth3}}} {false}}
26490 .endd
26491 In this case, if the lookup succeeds, the result is checked; if the lookup
26492 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
26493 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
26494 always fails if its second argument is empty. However, the second way of
26495 writing the test makes the logic clearer.
26496
26497
26498 .section "The LOGIN authentication mechanism" "SECID173"
26499 .cindex "LOGIN authentication mechanism"
26500 .cindex "authentication" "LOGIN mechanism"
26501 The LOGIN authentication mechanism is not documented in any RFC, but is in use
26502 in a number of programs. No data is sent with the AUTH command. Instead, a
26503 user name and password are supplied separately, in response to prompts. The
26504 plaintext authenticator can be configured to support this as in this example:
26505 .code
26506 fixed_login:
26507 driver = plaintext
26508 public_name = LOGIN
26509 server_prompts = User Name : Password
26510 server_condition = \
26511 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
26512 server_set_id = $auth1
26513 .endd
26514 Because of the way plaintext operates, this authenticator accepts data supplied
26515 with the AUTH command (in contravention of the specification of LOGIN), but
26516 if the client does not supply it (as is the case for LOGIN clients), the prompt
26517 strings are used to obtain two data items.
26518
26519 Some clients are very particular about the precise text of the prompts. For
26520 example, Outlook Express is reported to recognize only &"Username:"& and
26521 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
26522 strings. It uses the &%ldapauth%& expansion condition to check the user
26523 name and password by binding to an LDAP server:
26524 .code
26525 login:
26526 driver = plaintext
26527 public_name = LOGIN
26528 server_prompts = Username:: : Password::
26529 server_condition = ${if and{{ \
26530 !eq{}{$auth1} }{ \
26531 ldapauth{\
26532 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
26533 pass=${quote:$auth2} \
26534 ldap://ldap.example.org/} }} }
26535 server_set_id = uid=$auth1,ou=people,o=example.org
26536 .endd
26537 We have to check that the username is not empty before using it, because LDAP
26538 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
26539 operator to correctly quote the DN for authentication. However, the basic
26540 &%quote%& operator, rather than any of the LDAP quoting operators, is the
26541 correct one to use for the password, because quoting is needed only to make
26542 the password conform to the Exim syntax. At the LDAP level, the password is an
26543 uninterpreted string.
26544
26545
26546 .section "Support for different kinds of authentication" "SECID174"
26547 A number of string expansion features are provided for the purpose of
26548 interfacing to different ways of user authentication. These include checking
26549 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
26550 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
26551 &<<SECTexpcond>>&.
26552
26553
26554
26555
26556 .section "Using plaintext in a client" "SECID175"
26557 .cindex "options" "&(plaintext)& authenticator (client)"
26558 The &(plaintext)& authenticator has two client options:
26559
26560 .option client_ignore_invalid_base64 plaintext boolean false
26561 If the client receives a server prompt that is not a valid base64 string,
26562 authentication is abandoned by default. However, if this option is set true,
26563 the error in the challenge is ignored and the client sends the response as
26564 usual.
26565
26566 .option client_send plaintext string&!! unset
26567 The string is a colon-separated list of authentication data strings. Each
26568 string is independently expanded before being sent to the server. The first
26569 string is sent with the AUTH command; any more strings are sent in response
26570 to prompts from the server. Before each string is expanded, the value of the
26571 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
26572 with &$auth1$& for the first prompt. Up to three prompts are stored in this
26573 way. Thus, the prompt that is received in response to sending the first string
26574 (with the AUTH command) can be used in the expansion of the second string, and
26575 so on. If an invalid base64 string is received when
26576 &%client_ignore_invalid_base64%& is set, an empty string is put in the
26577 &$auth$&<&'n'&> variable.
26578
26579 &*Note*&: You cannot use expansion to create multiple strings, because
26580 splitting takes priority and happens first.
26581
26582 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
26583 the data, further processing is applied to each string before it is sent. If
26584 there are any single circumflex characters in the string, they are converted to
26585 NULs. Should an actual circumflex be required as data, it must be doubled in
26586 the string.
26587
26588 This is an example of a client configuration that implements the PLAIN
26589 authentication mechanism with a fixed user name and password:
26590 .code
26591 fixed_plain:
26592 driver = plaintext
26593 public_name = PLAIN
26594 client_send = ^username^mysecret
26595 .endd
26596 The lack of colons means that the entire text is sent with the AUTH
26597 command, with the circumflex characters converted to NULs. A similar example
26598 that uses the LOGIN mechanism is:
26599 .code
26600 fixed_login:
26601 driver = plaintext
26602 public_name = LOGIN
26603 client_send = : username : mysecret
26604 .endd
26605 The initial colon means that the first string is empty, so no data is sent with
26606 the AUTH command itself. The remaining strings are sent in response to
26607 prompts.
26608 .ecindex IIDplaiauth1
26609 .ecindex IIDplaiauth2
26610
26611
26612
26613
26614 . ////////////////////////////////////////////////////////////////////////////
26615 . ////////////////////////////////////////////////////////////////////////////
26616
26617 .chapter "The cram_md5 authenticator" "CHID9"
26618 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
26619 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
26620 .cindex "CRAM-MD5 authentication mechanism"
26621 .cindex "authentication" "CRAM-MD5 mechanism"
26622 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
26623 sends a challenge string to the client, and the response consists of a user
26624 name and the CRAM-MD5 digest of the challenge string combined with a secret
26625 string (password) which is known to both server and client. Thus, the secret
26626 is not sent over the network as plain text, which makes this authenticator more
26627 secure than &(plaintext)&. However, the downside is that the secret has to be
26628 available in plain text at either end.
26629
26630
26631 .section "Using cram_md5 as a server" "SECID176"
26632 .cindex "options" "&(cram_md5)& authenticator (server)"
26633 This authenticator has one server option, which must be set to configure the
26634 authenticator as a server:
26635
26636 .option server_secret cram_md5 string&!! unset
26637 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
26638 When the server receives the client's response, the user name is placed in
26639 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
26640 obtain the password for that user. The server then computes the CRAM-MD5 digest
26641 that the client should have sent, and checks that it received the correct
26642 string. If the expansion of &%server_secret%& is forced to fail, authentication
26643 fails. If the expansion fails for some other reason, a temporary error code is
26644 returned to the client.
26645
26646 For compatibility with previous releases of Exim, the user name is also placed
26647 in &$1$&. However, the use of this variables for this purpose is now
26648 deprecated, as it can lead to confusion in string expansions that also use
26649 numeric variables for other things.
26650
26651 For example, the following authenticator checks that the user name given by the
26652 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
26653 user name, authentication fails.
26654 .code
26655 fixed_cram:
26656 driver = cram_md5
26657 public_name = CRAM-MD5
26658 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
26659 server_set_id = $auth1
26660 .endd
26661 .vindex "&$authenticated_id$&"
26662 If authentication succeeds, the setting of &%server_set_id%& preserves the user
26663 name in &$authenticated_id$&. A more typical configuration might look up the
26664 secret string in a file, using the user name as the key. For example:
26665 .code
26666 lookup_cram:
26667 driver = cram_md5
26668 public_name = CRAM-MD5
26669 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
26670 {$value}fail}
26671 server_set_id = $auth1
26672 .endd
26673 Note that this expansion explicitly forces failure if the lookup fails
26674 because &$auth1$& contains an unknown user name.
26675
26676 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
26677 using the relevant libraries, you need to know the realm to specify in the
26678 lookup and then ask for the &"userPassword"& attribute for that user in that
26679 realm, with:
26680 .code
26681 cyrusless_crammd5:
26682 driver = cram_md5
26683 public_name = CRAM-MD5
26684 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
26685 dbmjz{/etc/sasldb2}{$value}fail}
26686 server_set_id = $auth1
26687 .endd
26688
26689 .section "Using cram_md5 as a client" "SECID177"
26690 .cindex "options" "&(cram_md5)& authenticator (client)"
26691 When used as a client, the &(cram_md5)& authenticator has two options:
26692
26693
26694
26695 .option client_name cram_md5 string&!! "the primary host name"
26696 This string is expanded, and the result used as the user name data when
26697 computing the response to the server's challenge.
26698
26699
26700 .option client_secret cram_md5 string&!! unset
26701 This option must be set for the authenticator to work as a client. Its value is
26702 expanded and the result used as the secret string when computing the response.
26703
26704
26705 .vindex "&$host$&"
26706 .vindex "&$host_address$&"
26707 Different user names and secrets can be used for different servers by referring
26708 to &$host$& or &$host_address$& in the options. Forced failure of either
26709 expansion string is treated as an indication that this authenticator is not
26710 prepared to handle this case. Exim moves on to the next configured client
26711 authenticator. Any other expansion failure causes Exim to give up trying to
26712 send the message to the current server.
26713
26714 A simple example configuration of a &(cram_md5)& authenticator, using fixed
26715 strings, is:
26716 .code
26717 fixed_cram:
26718 driver = cram_md5
26719 public_name = CRAM-MD5
26720 client_name = ph10
26721 client_secret = secret
26722 .endd
26723 .ecindex IIDcramauth1
26724 .ecindex IIDcramauth2
26725
26726
26727
26728 . ////////////////////////////////////////////////////////////////////////////
26729 . ////////////////////////////////////////////////////////////////////////////
26730
26731 .chapter "The cyrus_sasl authenticator" "CHID10"
26732 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
26733 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
26734 .cindex "Cyrus" "SASL library"
26735 .cindex "Kerberos"
26736 The code for this authenticator was provided by Matthew Byng-Maddick of A L
26737 Digital Ltd (&url(http://www.aldigital.co.uk)).
26738
26739 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
26740 library implementation of the RFC 2222 (&"Simple Authentication and Security
26741 Layer"&). This library supports a number of authentication mechanisms,
26742 including PLAIN and LOGIN, but also several others that Exim does not support
26743 directly. In particular, there is support for Kerberos authentication.
26744
26745 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
26746 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
26747 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
26748 name of the driver to determine which mechanism to support.
26749
26750 Where access to some kind of secret file is required, for example in GSSAPI
26751 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
26752 user, and that the Cyrus SASL library has no way of escalating privileges
26753 by default. You may also find you need to set environment variables,
26754 depending on the driver you are using.
26755
26756 The application name provided by Exim is &"exim"&, so various SASL options may
26757 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
26758 Kerberos, note that because of limitations in the GSSAPI interface,
26759 changing the server keytab might need to be communicated down to the Kerberos
26760 layer independently. The mechanism for doing so is dependent upon the Kerberos
26761 implementation.
26762
26763 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
26764 may be set to point to an alternative keytab file. Exim will pass this
26765 variable through from its own inherited environment when started as root or the
26766 Exim user. The keytab file needs to be readable by the Exim user.
26767 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
26768 environment variable. In practice, for those releases, the Cyrus authenticator
26769 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
26770 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
26771
26772
26773 .section "Using cyrus_sasl as a server" "SECID178"
26774 The &(cyrus_sasl)& authenticator has four private options. It puts the username
26775 (on a successful authentication) into &$auth1$&. For compatibility with
26776 previous releases of Exim, the username is also placed in &$1$&. However, the
26777 use of this variable for this purpose is now deprecated, as it can lead to
26778 confusion in string expansions that also use numeric variables for other
26779 things.
26780
26781
26782 .option server_hostname cyrus_sasl string&!! "see below"
26783 This option selects the hostname that is used when communicating with the
26784 library. The default value is &`$primary_hostname`&. It is up to the underlying
26785 SASL plug-in what it does with this data.
26786
26787
26788 .option server_mech cyrus_sasl string "see below"
26789 This option selects the authentication mechanism this driver should use. The
26790 default is the value of the generic &%public_name%& option. This option allows
26791 you to use a different underlying mechanism from the advertised name. For
26792 example:
26793 .code
26794 sasl:
26795 driver = cyrus_sasl
26796 public_name = X-ANYTHING
26797 server_mech = CRAM-MD5
26798 server_set_id = $auth1
26799 .endd
26800
26801 .option server_realm cyrus_sasl string&!! unset
26802 This specifies the SASL realm that the server claims to be in.
26803
26804
26805 .option server_service cyrus_sasl string &`smtp`&
26806 This is the SASL service that the server claims to implement.
26807
26808
26809 For straightforward cases, you do not need to set any of the authenticator's
26810 private options. All you need to do is to specify an appropriate mechanism as
26811 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
26812 PLAIN, you could have two authenticators as follows:
26813 .code
26814 sasl_cram_md5:
26815 driver = cyrus_sasl
26816 public_name = CRAM-MD5
26817 server_set_id = $auth1
26818
26819 sasl_plain:
26820 driver = cyrus_sasl
26821 public_name = PLAIN
26822 server_set_id = $auth2
26823 .endd
26824 Cyrus SASL does implement the LOGIN authentication method, even though it is
26825 not a standard method. It is disabled by default in the source distribution,
26826 but it is present in many binary distributions.
26827 .ecindex IIDcyrauth1
26828 .ecindex IIDcyrauth2
26829
26830
26831
26832
26833 . ////////////////////////////////////////////////////////////////////////////
26834 . ////////////////////////////////////////////////////////////////////////////
26835 .chapter "The dovecot authenticator" "CHAPdovecot"
26836 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
26837 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
26838 This authenticator is an interface to the authentication facility of the
26839 Dovecot POP/IMAP server, which can support a number of authentication methods.
26840 Note that Dovecot must be configured to use auth-client not auth-userdb.
26841 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
26842 to use the same mechanisms for SMTP authentication. This is a server
26843 authenticator only. There is only one option:
26844
26845 .option server_socket dovecot string unset
26846
26847 This option must specify the UNIX socket that is the interface to Dovecot
26848 authentication. The &%public_name%& option must specify an authentication
26849 mechanism that Dovecot is configured to support. You can have several
26850 authenticators for different mechanisms. For example:
26851 .code
26852 dovecot_plain:
26853 driver = dovecot
26854 public_name = PLAIN
26855 server_socket = /var/run/dovecot/auth-client
26856 server_set_id = $auth1
26857
26858 dovecot_ntlm:
26859 driver = dovecot
26860 public_name = NTLM
26861 server_socket = /var/run/dovecot/auth-client
26862 server_set_id = $auth1
26863 .endd
26864 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
26865 &$received_ip_address$& (that is, the connection is local), the &"secured"&
26866 option is passed in the Dovecot authentication command. If, for a TLS
26867 connection, a client certificate has been verified, the &"valid-client-cert"&
26868 option is passed. When authentication succeeds, the identity of the user
26869 who authenticated is placed in &$auth1$&.
26870 .ecindex IIDdcotauth1
26871 .ecindex IIDdcotauth2
26872
26873
26874 . ////////////////////////////////////////////////////////////////////////////
26875 . ////////////////////////////////////////////////////////////////////////////
26876 .chapter "The gsasl authenticator" "CHAPgsasl"
26877 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
26878 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
26879 .cindex "authentication" "GNU SASL"
26880 .cindex "authentication" "SASL"
26881 .cindex "authentication" "EXTERNAL"
26882 .cindex "authentication" "ANONYMOUS"
26883 .cindex "authentication" "PLAIN"
26884 .cindex "authentication" "LOGIN"
26885 .cindex "authentication" "DIGEST-MD5"
26886 .cindex "authentication" "CRAM-MD5"
26887 .cindex "authentication" "SCRAM-SHA-1"
26888 The &(gsasl)& authenticator provides server integration for the GNU SASL
26889 library and the mechanisms it provides. This is new as of the 4.80 release
26890 and there are a few areas where the library does not let Exim smoothly
26891 scale to handle future authentication mechanisms, so no guarantee can be
26892 made that any particular new authentication mechanism will be supported
26893 without code changes in Exim.
26894
26895
26896 .option server_channelbinding gsasl boolean false
26897 Do not set this true without consulting a cryptographic engineer.
26898
26899 Some authentication mechanisms are able to use external context at both ends
26900 of the session to bind the authentication to that context, and fail the
26901 authentication process if that context differs. Specifically, some TLS
26902 ciphersuites can provide identifying information about the cryptographic
26903 context.
26904
26905 This should have meant that certificate identity and verification becomes a
26906 non-issue, as a man-in-the-middle attack will cause the correct client and
26907 server to see different identifiers and authentication will fail.
26908
26909 This is currently only supported when using the GnuTLS library. This is
26910 only usable by mechanisms which support "channel binding"; at time of
26911 writing, that's the SCRAM family.
26912
26913 This defaults off to ensure smooth upgrade across Exim releases, in case
26914 this option causes some clients to start failing. Some future release
26915 of Exim might have switched the default to be true.
26916
26917 However, Channel Binding in TLS has proven to be broken in current versions.
26918 Do not plan to rely upon this feature for security, ever, without consulting
26919 with a subject matter expert (a cryptographic engineer).
26920
26921
26922 .option server_hostname gsasl string&!! "see below"
26923 This option selects the hostname that is used when communicating with the
26924 library. The default value is &`$primary_hostname`&.
26925 Some mechanisms will use this data.
26926
26927
26928 .option server_mech gsasl string "see below"
26929 This option selects the authentication mechanism this driver should use. The
26930 default is the value of the generic &%public_name%& option. This option allows
26931 you to use a different underlying mechanism from the advertised name. For
26932 example:
26933 .code
26934 sasl:
26935 driver = gsasl
26936 public_name = X-ANYTHING
26937 server_mech = CRAM-MD5
26938 server_set_id = $auth1
26939 .endd
26940
26941
26942 .option server_password gsasl string&!! unset
26943 Various mechanisms need access to the cleartext password on the server, so
26944 that proof-of-possession can be demonstrated on the wire, without sending
26945 the password itself.
26946
26947 The data available for lookup varies per mechanism.
26948 In all cases, &$auth1$& is set to the &'authentication id'&.
26949 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
26950 if available, else the empty string.
26951 The &$auth3$& variable will always be the &'realm'& if available,
26952 else the empty string.
26953
26954 A forced failure will cause authentication to defer.
26955
26956 If using this option, it may make sense to set the &%server_condition%&
26957 option to be simply "true".
26958
26959
26960 .option server_realm gsasl string&!! unset
26961 This specifies the SASL realm that the server claims to be in.
26962 Some mechanisms will use this data.
26963
26964
26965 .option server_scram_iter gsasl string&!! unset
26966 This option provides data for the SCRAM family of mechanisms.
26967 &$auth1$& is not available at evaluation time.
26968 (This may change, as we receive feedback on use)
26969
26970
26971 .option server_scram_salt gsasl string&!! unset
26972 This option provides data for the SCRAM family of mechanisms.
26973 &$auth1$& is not available at evaluation time.
26974 (This may change, as we receive feedback on use)
26975
26976
26977 .option server_service gsasl string &`smtp`&
26978 This is the SASL service that the server claims to implement.
26979 Some mechanisms will use this data.
26980
26981
26982 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
26983 .vindex "&$auth1$&, &$auth2$&, etc"
26984 These may be set when evaluating specific options, as detailed above.
26985 They will also be set when evaluating &%server_condition%&.
26986
26987 Unless otherwise stated below, the &(gsasl)& integration will use the following
26988 meanings for these variables:
26989
26990 .ilist
26991 .vindex "&$auth1$&"
26992 &$auth1$&: the &'authentication id'&
26993 .next
26994 .vindex "&$auth2$&"
26995 &$auth2$&: the &'authorization id'&
26996 .next
26997 .vindex "&$auth3$&"
26998 &$auth3$&: the &'realm'&
26999 .endlist
27000
27001 On a per-mechanism basis:
27002
27003 .ilist
27004 .cindex "authentication" "EXTERNAL"
27005 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
27006 the &%server_condition%& option must be present.
27007 .next
27008 .cindex "authentication" "ANONYMOUS"
27009 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
27010 the &%server_condition%& option must be present.
27011 .next
27012 .cindex "authentication" "GSSAPI"
27013 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
27014 &$auth2$& will be set to the &'authorization id'&,
27015 the &%server_condition%& option must be present.
27016 .endlist
27017
27018 An &'anonymous token'& is something passed along as an unauthenticated
27019 identifier; this is analogous to FTP anonymous authentication passing an
27020 email address, or software-identifier@, as the "password".
27021
27022
27023 An example showing the password having the realm specified in the callback
27024 and demonstrating a Cyrus SASL to GSASL migration approach is:
27025 .code
27026 gsasl_cyrusless_crammd5:
27027 driver = gsasl
27028 public_name = CRAM-MD5
27029 server_realm = imap.example.org
27030 server_password = ${lookup{$auth1:$auth3:userPassword}\
27031 dbmjz{/etc/sasldb2}{$value}fail}
27032 server_set_id = ${quote:$auth1}
27033 server_condition = yes
27034 .endd
27035
27036
27037 . ////////////////////////////////////////////////////////////////////////////
27038 . ////////////////////////////////////////////////////////////////////////////
27039
27040 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
27041 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
27042 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
27043 .cindex "authentication" "GSSAPI"
27044 .cindex "authentication" "Kerberos"
27045 The &(heimdal_gssapi)& authenticator provides server integration for the
27046 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
27047 reliably.
27048
27049 .option server_hostname heimdal_gssapi string&!! "see below"
27050 This option selects the hostname that is used, with &%server_service%&,
27051 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
27052 identifier. The default value is &`$primary_hostname`&.
27053
27054 .option server_keytab heimdal_gssapi string&!! unset
27055 If set, then Heimdal will not use the system default keytab (typically
27056 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
27057 The value should be a pathname, with no &"file:"& prefix.
27058
27059 .option server_service heimdal_gssapi string&!! "smtp"
27060 This option specifies the service identifier used, in conjunction with
27061 &%server_hostname%&, for building the identifier for finding credentials
27062 from the keytab.
27063
27064
27065 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
27066 Beware that these variables will typically include a realm, thus will appear
27067 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
27068 not verified, so a malicious client can set it to anything.
27069
27070 The &$auth1$& field should be safely trustable as a value from the Key
27071 Distribution Center. Note that these are not quite email addresses.
27072 Each identifier is for a role, and so the left-hand-side may include a
27073 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
27074
27075 .vindex "&$auth1$&, &$auth2$&, etc"
27076 .ilist
27077 .vindex "&$auth1$&"
27078 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
27079 .next
27080 .vindex "&$auth2$&"
27081 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
27082 authentication. If that was empty, this will also be set to the
27083 GSS Display Name.
27084 .endlist
27085
27086
27087 . ////////////////////////////////////////////////////////////////////////////
27088 . ////////////////////////////////////////////////////////////////////////////
27089
27090 .chapter "The spa authenticator" "CHAPspa"
27091 .scindex IIDspaauth1 "&(spa)& authenticator"
27092 .scindex IIDspaauth2 "authenticators" "&(spa)&"
27093 .cindex "authentication" "Microsoft Secure Password"
27094 .cindex "authentication" "NTLM"
27095 .cindex "Microsoft Secure Password Authentication"
27096 .cindex "NTLM authentication"
27097 The &(spa)& authenticator provides client support for Microsoft's &'Secure
27098 Password Authentication'& mechanism,
27099 which is also sometimes known as NTLM (NT LanMan). The code for client side of
27100 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
27101 taken from the Samba project (&url(http://www.samba.org)). The code for the
27102 server side was subsequently contributed by Tom Kistner. The mechanism works as
27103 follows:
27104
27105 .ilist
27106 After the AUTH command has been accepted, the client sends an SPA
27107 authentication request based on the user name and optional domain.
27108 .next
27109 The server sends back a challenge.
27110 .next
27111 The client builds a challenge response which makes use of the user's password
27112 and sends it to the server, which then accepts or rejects it.
27113 .endlist
27114
27115 Encryption is used to protect the password in transit.
27116
27117
27118
27119 .section "Using spa as a server" "SECID179"
27120 .cindex "options" "&(spa)& authenticator (server)"
27121 The &(spa)& authenticator has just one server option:
27122
27123 .option server_password spa string&!! unset
27124 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
27125 This option is expanded, and the result must be the cleartext password for the
27126 authenticating user, whose name is at this point in &$auth1$&. For
27127 compatibility with previous releases of Exim, the user name is also placed in
27128 &$1$&. However, the use of this variable for this purpose is now deprecated, as
27129 it can lead to confusion in string expansions that also use numeric variables
27130 for other things. For example:
27131 .code
27132 spa:
27133 driver = spa
27134 public_name = NTLM
27135 server_password = \
27136 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
27137 .endd
27138 If the expansion is forced to fail, authentication fails. Any other expansion
27139 failure causes a temporary error code to be returned.
27140
27141
27142
27143
27144
27145 .section "Using spa as a client" "SECID180"
27146 .cindex "options" "&(spa)& authenticator (client)"
27147 The &(spa)& authenticator has the following client options:
27148
27149
27150
27151 .option client_domain spa string&!! unset
27152 This option specifies an optional domain for the authentication.
27153
27154
27155 .option client_password spa string&!! unset
27156 This option specifies the user's password, and must be set.
27157
27158
27159 .option client_username spa string&!! unset
27160 This option specifies the user name, and must be set. Here is an example of a
27161 configuration of this authenticator for use with the mail servers at
27162 &'msn.com'&:
27163 .code
27164 msn:
27165 driver = spa
27166 public_name = MSN
27167 client_username = msn/msn_username
27168 client_password = msn_plaintext_password
27169 client_domain = DOMAIN_OR_UNSET
27170 .endd
27171 .ecindex IIDspaauth1
27172 .ecindex IIDspaauth2
27173
27174
27175
27176
27177
27178 . ////////////////////////////////////////////////////////////////////////////
27179 . ////////////////////////////////////////////////////////////////////////////
27180
27181 .chapter "The tls authenticator" "CHAPtlsauth"
27182 .scindex IIDtlsauth1 "&(tls)& authenticator"
27183 .scindex IIDtlsauth2 "authenticators" "&(tls)&"
27184 .cindex "authentication" "Client Certificate"
27185 .cindex "authentication" "X509"
27186 .cindex "Certificate-based authentication"
27187 The &(tls)& authenticator provides server support for
27188 authentication based on client certificates.
27189
27190 It is not an SMTP authentication mechanism and is not
27191 advertised by the server as part of the SMTP EHLO response.
27192 It is an Exim authenticator in the sense that it affects
27193 the protocol element of the log line, can be tested for
27194 by the &%authenticated%& ACL condition, and can set
27195 the &$authenticated_id$& variable.
27196
27197 The client must present a verifiable certificate,
27198 for which it must have been requested via the
27199 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
27200 (see &<<CHAPTLS>>&).
27201
27202 If an authenticator of this type is configured it is
27203 run before any SMTP-level communication is done,
27204 and can authenticate the connection.
27205 If it does, SMTP authentication is not offered.
27206
27207 A maximum of one authenticator of this type may be present.
27208
27209
27210 .cindex "options" "&(tls)& authenticator (server)"
27211 The &(tls)& authenticator has three server options:
27212
27213 .option server_param1 tls string&!! unset
27214 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
27215 This option is expanded after the TLS negotiation and
27216 the result is placed in &$auth1$&.
27217 If the expansion is forced to fail, authentication fails. Any other expansion
27218 failure causes a temporary error code to be returned.
27219
27220 .option server_param2 tls string&!! unset
27221 .option server_param3 tls string&!! unset
27222 As above, for &$auth2$& and &$auth3$&.
27223
27224 &%server_param1%& may also be spelled &%server_param%&.
27225
27226
27227 Example:
27228 .code
27229 tls:
27230 driver = tls
27231 server_param1 = ${certextract {subj_altname,mail,>:} \
27232 {$tls_in_peercert}}
27233 server_condition = ${if forany {$auth1} \
27234 {!= {0} \
27235 {${lookup ldap{ldap:///\
27236 mailname=${quote_ldap_dn:${lc:$item}},\
27237 ou=users,LDAP_DC?mailid} {$value}{0} \
27238 } } } }
27239 server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
27240 .endd
27241 This accepts a client certificate that is verifiable against any
27242 of your configured trust-anchors
27243 (which usually means the full set of public CAs)
27244 and which has a SAN with a good account name.
27245 Note that the client cert is on the wire in-clear, including the SAN,
27246 whereas a plaintext SMTP AUTH done inside TLS is not.
27247
27248 . An alternative might use
27249 . .code
27250 . server_param1 = ${sha256:$tls_in_peercert}
27251 . .endd
27252 . to require one of a set of specific certs that define a given account
27253 . (the verification is still required, but mostly irrelevant).
27254 . This would help for per-device use.
27255 .
27256 . However, for the future we really need support for checking a
27257 . user cert in LDAP - which probably wants a base-64 DER.
27258
27259 .ecindex IIDtlsauth1
27260 .ecindex IIDtlsauth2
27261
27262
27263 Note that because authentication is traditionally an SMTP operation,
27264 the &%authenticated%& ACL condition cannot be used in
27265 a connect- or helo-ACL.
27266
27267
27268
27269 . ////////////////////////////////////////////////////////////////////////////
27270 . ////////////////////////////////////////////////////////////////////////////
27271
27272 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
27273 "Encrypted SMTP connections"
27274 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
27275 .scindex IIDencsmtp2 "SMTP" "encryption"
27276 .cindex "TLS" "on SMTP connection"
27277 .cindex "OpenSSL"
27278 .cindex "GnuTLS"
27279 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
27280 Sockets Layer), is implemented by making use of the OpenSSL library or the
27281 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
27282 cryptographic code in the Exim distribution itself for implementing TLS. In
27283 order to use this feature you must install OpenSSL or GnuTLS, and then build a
27284 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
27285 You also need to understand the basic concepts of encryption at a managerial
27286 level, and in particular, the way that public keys, private keys, and
27287 certificates are used.
27288
27289 RFC 3207 defines how SMTP connections can make use of encryption. Once a
27290 connection is established, the client issues a STARTTLS command. If the
27291 server accepts this, the client and the server negotiate an encryption
27292 mechanism. If the negotiation succeeds, the data that subsequently passes
27293 between them is encrypted.
27294
27295 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
27296 and if so, what cipher suite is in use, whether the client supplied a
27297 certificate, and whether or not that certificate was verified. This makes it
27298 possible for an Exim server to deny or accept certain commands based on the
27299 encryption state.
27300
27301 &*Warning*&: Certain types of firewall and certain anti-virus products can
27302 disrupt TLS connections. You need to turn off SMTP scanning for these products
27303 in order to get TLS to work.
27304
27305
27306
27307 .section "Support for the &""submissions""& (aka &""ssmtp""& and &""smtps""&) protocol" &&&
27308 "SECID284"
27309 .cindex "submissions protocol"
27310 .cindex "ssmtp protocol"
27311 .cindex "smtps protocol"
27312 .cindex "SMTP" "submissions protocol"
27313 .cindex "SMTP" "ssmtp protocol"
27314 .cindex "SMTP" "smtps protocol"
27315 The history of port numbers for TLS in SMTP is a little messy and has been
27316 contentious. As of RFC 8314, the common practice of using the historically
27317 allocated port 465 for "email submission but with TLS immediately upon connect
27318 instead of using STARTTLS" is officially blessed by the IETF, and recommended
27319 by them in preference to STARTTLS.
27320
27321 The name originally assigned to the port was &"ssmtp"& or &"smtps"&, but as
27322 clarity emerged over the dual roles of SMTP, for MX delivery and Email
27323 Submission, nomenclature has shifted. The modern name is now &"submissions"&.
27324
27325 This approach was, for a while, officially abandoned when encrypted SMTP was
27326 standardized, but many clients kept using it, even as the TCP port number was
27327 reassigned for other use.
27328 Thus you may encounter guidance claiming that you shouldn't enable use of
27329 this port.
27330 In practice, a number of mail-clients have only ever supported submissions,
27331 not submission with STARTTLS upgrade.
27332 Ideally, offer both submission (587) and submissions (465) service.
27333
27334 Exim supports TLS-on-connect by means of the &%tls_on_connect_ports%&
27335 global option. Its value must be a list of port numbers;
27336 the most common use is expected to be:
27337 .code
27338 tls_on_connect_ports = 465
27339 .endd
27340 The port numbers specified by this option apply to all SMTP connections, both
27341 via the daemon and via &'inetd'&. You still need to specify all the ports that
27342 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
27343 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
27344 an extra port &-- rather, it specifies different behaviour on a port that is
27345 defined elsewhere.
27346
27347 There is also a &%-tls-on-connect%& command line option. This overrides
27348 &%tls_on_connect_ports%&; it forces the TLS-only behaviour for all ports.
27349
27350
27351
27352
27353
27354
27355 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
27356 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
27357 The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
27358 followed later, when the first versions of GnuTLS were released. To build Exim
27359 to use GnuTLS, you need to set
27360 .code
27361 USE_GNUTLS=yes
27362 .endd
27363 in Local/Makefile, in addition to
27364 .code
27365 SUPPORT_TLS=yes
27366 .endd
27367 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
27368 include files and libraries for GnuTLS can be found.
27369
27370 There are some differences in usage when using GnuTLS instead of OpenSSL:
27371
27372 .ilist
27373 The &%tls_verify_certificates%& option
27374 cannot be the path of a directory
27375 for GnuTLS versions before 3.3.6
27376 (for later versions, or OpenSSL, it can be either).
27377 .next
27378 The default value for &%tls_dhparam%& differs for historical reasons.
27379 .next
27380 .vindex "&$tls_in_peerdn$&"
27381 .vindex "&$tls_out_peerdn$&"
27382 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
27383 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
27384 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
27385 .next
27386 OpenSSL identifies cipher suites using hyphens as separators, for example:
27387 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
27388 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
27389 in a cipher list. To make life simpler, Exim changes underscores to hyphens
27390 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
27391 to handle its own older variants) when processing lists of cipher suites in the
27392 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
27393 option).
27394 .next
27395 The &%tls_require_ciphers%& options operate differently, as described in the
27396 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
27397 .next
27398 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
27399 When using OpenSSL, this option is ignored.
27400 (If an API is found to let OpenSSL be configured in this way,
27401 let the Exim Maintainers know and we'll likely use it).
27402 .next
27403 With GnuTLS, if an explicit list is used for the &%tls_privatekey%& main option
27404 main option, it must be ordered to match the &%tls_certificate%& list.
27405 .next
27406 Some other recently added features may only be available in one or the other.
27407 This should be documented with the feature. If the documentation does not
27408 explicitly state that the feature is infeasible in the other TLS
27409 implementation, then patches are welcome.
27410 .endlist
27411
27412
27413 .section "GnuTLS parameter computation" "SECTgnutlsparam"
27414 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
27415 an explicit path; if the latter, then the text about generation still applies,
27416 but not the chosen filename.
27417 By default, as of Exim 4.80 a hard-coded D-H prime is used.
27418 See the documentation of &%tls_dhparam%& for more information.
27419
27420 GnuTLS uses D-H parameters that may take a substantial amount of time
27421 to compute. It is unreasonable to re-compute them for every TLS session.
27422 Therefore, Exim keeps this data in a file in its spool directory, called
27423 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
27424 of bits requested.
27425 The file is owned by the Exim user and is readable only by
27426 its owner. Every Exim process that start up GnuTLS reads the D-H
27427 parameters from this file. If the file does not exist, the first Exim process
27428 that needs it computes the data and writes it to a temporary file which is
27429 renamed once it is complete. It does not matter if several Exim processes do
27430 this simultaneously (apart from wasting a few resources). Once a file is in
27431 place, new Exim processes immediately start using it.
27432
27433 For maximum security, the parameters that are stored in this file should be
27434 recalculated periodically, the frequency depending on your paranoia level.
27435 If you are avoiding using the fixed D-H primes published in RFCs, then you
27436 are concerned about some advanced attacks and will wish to do this; if you do
27437 not regenerate then you might as well stick to the standard primes.
27438
27439 Arranging this is easy in principle; just delete the file when you want new
27440 values to be computed. However, there may be a problem. The calculation of new
27441 parameters needs random numbers, and these are obtained from &_/dev/random_&.
27442 If the system is not very active, &_/dev/random_& may delay returning data
27443 until enough randomness (entropy) is available. This may cause Exim to hang for
27444 a substantial amount of time, causing timeouts on incoming connections.
27445
27446 The solution is to generate the parameters externally to Exim. They are stored
27447 in &_gnutls-params-N_& in PEM format, which means that they can be
27448 generated externally using the &(certtool)& command that is part of GnuTLS.
27449
27450 To replace the parameters with new ones, instead of deleting the file
27451 and letting Exim re-create it, you can generate new parameters using
27452 &(certtool)& and, when this has been done, replace Exim's cache file by
27453 renaming. The relevant commands are something like this:
27454 .code
27455 # ls
27456 [ look for file; assume gnutls-params-2236 is the most recent ]
27457 # rm -f new-params
27458 # touch new-params
27459 # chown exim:exim new-params
27460 # chmod 0600 new-params
27461 # certtool --generate-dh-params --bits 2236 >>new-params
27462 # openssl dhparam -noout -text -in new-params | head
27463 [ check the first line, make sure it's not more than 2236;
27464 if it is, then go back to the start ("rm") and repeat
27465 until the size generated is at most the size requested ]
27466 # chmod 0400 new-params
27467 # mv new-params gnutls-params-2236
27468 .endd
27469 If Exim never has to generate the parameters itself, the possibility of
27470 stalling is removed.
27471
27472 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
27473 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
27474 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
27475 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
27476 and Exim does so. This attempt to remove Exim from TLS policy decisions
27477 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
27478 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
27479 which applies to all D-H usage, client or server. If the value returned by
27480 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
27481 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
27482 limit, which is still much higher than Exim historically used.
27483
27484 The filename and bits used will change as the GnuTLS maintainers change the
27485 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
27486 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
27487 2432 bits, while NSS is limited to 2236 bits.
27488
27489 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
27490 increase the chance of the generated prime actually being within acceptable
27491 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
27492 procedure above. There is no sane procedure available to Exim to double-check
27493 the size of the generated prime, so it might still be too large.
27494
27495
27496 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
27497 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
27498 .oindex "&%tls_require_ciphers%&" "OpenSSL"
27499 There is a function in the OpenSSL library that can be passed a list of cipher
27500 suites before the cipher negotiation takes place. This specifies which ciphers
27501 .new
27502 are acceptable for TLS versions prior to 1.3.
27503 .wen
27504 The list is colon separated and may contain names like
27505 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
27506 directly to this function call.
27507 Many systems will install the OpenSSL manual-pages, so you may have
27508 &'ciphers(1)'& available to you.
27509 The following quotation from the OpenSSL
27510 documentation specifies what forms of item are allowed in the cipher string:
27511
27512 .ilist
27513 It can consist of a single cipher suite such as RC4-SHA.
27514 .next
27515 It can represent a list of cipher suites containing a certain algorithm,
27516 or cipher suites of a certain type. For example SHA1 represents all
27517 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
27518 SSL v3 algorithms.
27519 .next
27520 Lists of cipher suites can be combined in a single cipher string using
27521 the + character. This is used as a logical and operation. For example
27522 SHA1+DES represents all cipher suites containing the SHA1 and the DES
27523 algorithms.
27524 .endlist
27525
27526 Each cipher string can be optionally preceded by one of the characters &`!`&,
27527 &`-`& or &`+`&.
27528 .ilist
27529 If &`!`& is used, the ciphers are permanently deleted from the list. The
27530 ciphers deleted can never reappear in the list even if they are explicitly
27531 stated.
27532 .next
27533 If &`-`& is used, the ciphers are deleted from the list, but some or all
27534 of the ciphers can be added again by later options.
27535 .next
27536 If &`+`& is used, the ciphers are moved to the end of the list. This
27537 option does not add any new ciphers; it just moves matching existing ones.
27538 .endlist
27539
27540 If none of these characters is present, the string is interpreted as
27541 a list of ciphers to be appended to the current preference list. If the list
27542 includes any ciphers already present they will be ignored: that is, they will
27543 not be moved to the end of the list.
27544 .endlist
27545
27546 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
27547 string:
27548 .code
27549 # note single-quotes to get ! past any shell history expansion
27550 $ openssl ciphers 'HIGH:!MD5:!SHA1'
27551 .endd
27552
27553 This example will let the library defaults be permitted on the MX port, where
27554 there's probably no identity verification anyway, but ups the ante on the
27555 submission ports where the administrator might have some influence on the
27556 choice of clients used:
27557 .code
27558 # OpenSSL variant; see man ciphers(1)
27559 tls_require_ciphers = ${if =={$received_port}{25}\
27560 {DEFAULT}\
27561 {HIGH:!MD5:!SHA1}}
27562 .endd
27563
27564 This example will prefer ECDSA-authenticated ciphers over RSA ones:
27565 .code
27566 tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT
27567 .endd
27568
27569 .new
27570 For TLS version 1.3 the control available is less fine-grained
27571 and Exim does not provide access to it at present.
27572 The value of the &%tls_require_ciphers%& option is ignored when
27573 TLS version 1.3 is negotiated.
27574
27575 As of writing the library default cipher suite list for TLSv1.3 is
27576 .code
27577 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
27578 .endd
27579 .wen
27580
27581
27582 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
27583 "SECTreqciphgnu"
27584 .cindex "GnuTLS" "specifying parameters for"
27585 .cindex "TLS" "specifying ciphers (GnuTLS)"
27586 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
27587 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
27588 .cindex "TLS" "specifying protocols (GnuTLS)"
27589 .cindex "TLS" "specifying priority string (GnuTLS)"
27590 .oindex "&%tls_require_ciphers%&" "GnuTLS"
27591 The GnuTLS library allows the caller to provide a "priority string", documented
27592 as part of the &[gnutls_priority_init]& function. This is very similar to the
27593 ciphersuite specification in OpenSSL.
27594
27595 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
27596 and controls both protocols and ciphers.
27597
27598 The &%tls_require_ciphers%& option is available both as an global option,
27599 controlling how Exim behaves as a server, and also as an option of the
27600 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
27601 the value is string expanded. The resulting string is not an Exim list and
27602 the string is given to the GnuTLS library, so that Exim does not need to be
27603 aware of future feature enhancements of GnuTLS.
27604
27605 Documentation of the strings accepted may be found in the GnuTLS manual, under
27606 "Priority strings". This is online as
27607 &url(http://www.gnutls.org/manual/html_node/Priority-Strings.html),
27608 but beware that this relates to GnuTLS 3, which may be newer than the version
27609 installed on your system. If you are using GnuTLS 3,
27610 then the example code
27611 &url(http://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string)
27612 on that site can be used to test a given string.
27613
27614 For example:
27615 .code
27616 # Disable older versions of protocols
27617 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
27618 .endd
27619
27620 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
27621 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
27622 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
27623
27624 This example will let the library defaults be permitted on the MX port, where
27625 there's probably no identity verification anyway, and lowers security further
27626 by increasing compatibility; but this ups the ante on the submission ports
27627 where the administrator might have some influence on the choice of clients
27628 used:
27629 .code
27630 # GnuTLS variant
27631 tls_require_ciphers = ${if =={$received_port}{25}\
27632 {NORMAL:%COMPAT}\
27633 {SECURE128}}
27634 .endd
27635
27636
27637 .section "Configuring an Exim server to use TLS" "SECID182"
27638 .cindex "TLS" "configuring an Exim server"
27639 When Exim has been built with TLS support, it advertises the availability of
27640 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
27641 but not to any others. The default value of this option is *, which means
27642 that STARTTLS is always advertised. Set it to blank to never advertise;
27643 this is reasonable for systems that want to use TLS only as a client.
27644
27645 If STARTTLS is to be used you
27646 need to set some other options in order to make TLS available.
27647
27648 If a client issues a STARTTLS command and there is some configuration
27649 problem in the server, the command is rejected with a 454 error. If the client
27650 persists in trying to issue SMTP commands, all except QUIT are rejected
27651 with the error
27652 .code
27653 554 Security failure
27654 .endd
27655 If a STARTTLS command is issued within an existing TLS session, it is
27656 rejected with a 554 error code.
27657
27658 To enable TLS operations on a server, the &%tls_advertise_hosts%& option
27659 must be set to match some hosts. The default is * which matches all hosts.
27660
27661 If this is all you do, TLS encryption will be enabled but not authentication -
27662 meaning that the peer has no assurance it is actually you he is talking to.
27663 You gain protection from a passive sniffer listening on the wire but not
27664 from someone able to intercept the communication.
27665
27666 Further protection requires some further configuration at the server end.
27667
27668 To make TLS work you need to set, in the server,
27669 .code
27670 tls_certificate = /some/file/name
27671 tls_privatekey = /some/file/name
27672 .endd
27673 These options are, in fact, expanded strings, so you can make them depend on
27674 the identity of the client that is connected if you wish. The first file
27675 contains the server's X509 certificate, and the second contains the private key
27676 that goes with it. These files need to be
27677 PEM format and readable by the Exim user, and must
27678 always be given as full path names.
27679 The key must not be password-protected.
27680 They can be the same file if both the
27681 certificate and the key are contained within it. If &%tls_privatekey%& is not
27682 set, or if its expansion is forced to fail or results in an empty string, this
27683 is assumed to be the case. The certificate file may also contain intermediate
27684 certificates that need to be sent to the client to enable it to authenticate
27685 the server's certificate.
27686
27687 For dual-stack (eg. RSA and ECDSA) configurations, these options can be
27688 colon-separated lists of file paths. Ciphers using given authentication
27689 algorithms require the presence of a suitable certificate to supply the
27690 public-key. The server selects among the certificates to present to the
27691 client depending on the selected cipher, hence the priority ordering for
27692 ciphers will affect which certificate is used.
27693
27694 If you do not understand about certificates and keys, please try to find a
27695 source of this background information, which is not Exim-specific. (There are a
27696 few comments below in section &<<SECTcerandall>>&.)
27697
27698 &*Note*&: These options do not apply when Exim is operating as a client &--
27699 they apply only in the case of a server. If you need to use a certificate in an
27700 Exim client, you must set the options of the same names in an &(smtp)&
27701 transport.
27702
27703 With just these options, an Exim server will be able to use TLS. It does not
27704 require the client to have a certificate (but see below for how to insist on
27705 this). There is one other option that may be needed in other situations. If
27706 .code
27707 tls_dhparam = /some/file/name
27708 .endd
27709 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
27710 with the parameters contained in the file.
27711 Set this to &`none`& to disable use of DH entirely, by making no prime
27712 available:
27713 .code
27714 tls_dhparam = none
27715 .endd
27716 This may also be set to a string identifying a standard prime to be used for
27717 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
27718 used is &`ike23`&. There are a few standard primes available, see the
27719 documentation for &%tls_dhparam%& for the complete list.
27720
27721 See the command
27722 .code
27723 openssl dhparam
27724 .endd
27725 for a way of generating file data.
27726
27727 The strings supplied for these three options are expanded every time a client
27728 host connects. It is therefore possible to use different certificates and keys
27729 for different hosts, if you so wish, by making use of the client's IP address
27730 in &$sender_host_address$& to control the expansion. If a string expansion is
27731 forced to fail, Exim behaves as if the option is not set.
27732
27733 .cindex "cipher" "logging"
27734 .cindex "log" "TLS cipher"
27735 .vindex "&$tls_in_cipher$&"
27736 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
27737 an incoming TLS connection. It is included in the &'Received:'& header of an
27738 incoming message (by default &-- you can, of course, change this), and it is
27739 also included in the log line that records a message's arrival, keyed by
27740 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
27741 condition can be used to test for specific cipher suites in ACLs.
27742
27743 Once TLS has been established, the ACLs that run for subsequent SMTP commands
27744 can check the name of the cipher suite and vary their actions accordingly. The
27745 cipher suite names vary, depending on which TLS library is being used. For
27746 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
27747 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
27748 documentation for more details.
27749
27750 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
27751 (again depending on the &%tls_cipher%& log selector).
27752
27753
27754 .section "Requesting and verifying client certificates" "SECID183"
27755 .cindex "certificate" "verification of client"
27756 .cindex "TLS" "client certificate verification"
27757 If you want an Exim server to request a certificate when negotiating a TLS
27758 session with a client, you must set either &%tls_verify_hosts%& or
27759 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
27760 apply to all TLS connections. For any host that matches one of these options,
27761 Exim requests a certificate as part of the setup of the TLS session. The
27762 contents of the certificate are verified by comparing it with a list of
27763 expected certificates.
27764 These may be the system default set (depending on library version),
27765 an explicit file or,
27766 depending on library version, a directory, identified by
27767 &%tls_verify_certificates%&.
27768
27769 A file can contain multiple certificates, concatenated end to end. If a
27770 directory is used
27771 (OpenSSL only),
27772 each certificate must be in a separate file, with a name (or a symbolic link)
27773 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
27774 certificate. You can compute the relevant hash by running the command
27775 .code
27776 openssl x509 -hash -noout -in /cert/file
27777 .endd
27778 where &_/cert/file_& contains a single certificate.
27779
27780 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
27781 what happens if the client does not supply a certificate, or if the certificate
27782 does not match any of the certificates in the collection named by
27783 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
27784 attempt to set up a TLS session is aborted, and the incoming connection is
27785 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
27786 session continues. ACLs that run for subsequent SMTP commands can detect the
27787 fact that no certificate was verified, and vary their actions accordingly. For
27788 example, you can insist on a certificate before accepting a message for
27789 relaying, but not when the message is destined for local delivery.
27790
27791 .vindex "&$tls_in_peerdn$&"
27792 When a client supplies a certificate (whether it verifies or not), the value of
27793 the Distinguished Name of the certificate is made available in the variable
27794 &$tls_in_peerdn$& during subsequent processing of the message.
27795
27796 .cindex "log" "distinguished name"
27797 Because it is often a long text string, it is not included in the log line or
27798 &'Received:'& header by default. You can arrange for it to be logged, keyed by
27799 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
27800 &%received_header_text%& to change the &'Received:'& header. When no
27801 certificate is supplied, &$tls_in_peerdn$& is empty.
27802
27803
27804 .section "Revoked certificates" "SECID184"
27805 .cindex "TLS" "revoked certificates"
27806 .cindex "revocation list"
27807 .cindex "certificate" "revocation list"
27808 .cindex "OCSP" "stapling"
27809 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
27810 certificates are revoked. If you have such a list, you can pass it to an Exim
27811 server using the global option called &%tls_crl%& and to an Exim client using
27812 an identically named option for the &(smtp)& transport. In each case, the value
27813 of the option is expanded and must then be the name of a file that contains a
27814 CRL in PEM format.
27815 The downside is that clients have to periodically re-download a potentially huge
27816 file from every certificate authority they know of.
27817
27818 The way with most moving parts at query time is Online Certificate
27819 Status Protocol (OCSP), where the client verifies the certificate
27820 against an OCSP server run by the CA. This lets the CA track all
27821 usage of the certs. It requires running software with access to the
27822 private key of the CA, to sign the responses to the OCSP queries. OCSP
27823 is based on HTTP and can be proxied accordingly.
27824
27825 The only widespread OCSP server implementation (known to this writer)
27826 comes as part of OpenSSL and aborts on an invalid request, such as
27827 connecting to the port and then disconnecting. This requires
27828 re-entering the passphrase each time some random client does this.
27829
27830 The third way is OCSP Stapling; in this, the server using a certificate
27831 issued by the CA periodically requests an OCSP proof of validity from
27832 the OCSP server, then serves it up inline as part of the TLS
27833 negotiation. This approach adds no extra round trips, does not let the
27834 CA track users, scales well with number of certs issued by the CA and is
27835 resilient to temporary OCSP server failures, as long as the server
27836 starts retrying to fetch an OCSP proof some time before its current
27837 proof expires. The downside is that it requires server support.
27838
27839 Unless Exim is built with the support disabled,
27840 or with GnuTLS earlier than version 3.3.16 / 3.4.8
27841 support for OCSP stapling is included.
27842
27843 There is a global option called &%tls_ocsp_file%&.
27844 The file specified therein is expected to be in DER format, and contain
27845 an OCSP proof. Exim will serve it as part of the TLS handshake. This
27846 option will be re-expanded for SNI, if the &%tls_certificate%& option
27847 contains &`tls_in_sni`&, as per other TLS options.
27848
27849 Exim does not at this time implement any support for fetching a new OCSP
27850 proof. The burden is on the administrator to handle this, outside of
27851 Exim. The file specified should be replaced atomically, so that the
27852 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
27853 on each connection, so a new file will be handled transparently on the
27854 next connection.
27855
27856 When built with OpenSSL Exim will check for a valid next update timestamp
27857 in the OCSP proof; if not present, or if the proof has expired, it will be
27858 ignored.
27859
27860 For the client to be able to verify the stapled OCSP the server must
27861 also supply, in its stapled information, any intermediate
27862 certificates for the chain leading to the OCSP proof from the signer
27863 of the server certificate. There may be zero or one such. These
27864 intermediate certificates should be added to the server OCSP stapling
27865 file named by &%tls_ocsp_file%&.
27866
27867 Note that the proof only covers the terminal server certificate,
27868 not any of the chain from CA to it.
27869
27870 There is no current way to staple a proof for a client certificate.
27871
27872 .code
27873 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
27874 OCSP server is supplied. The server URL may be included in the
27875 server certificate, if the CA is helpful.
27876
27877 One failure mode seen was the OCSP Signer cert expiring before the end
27878 of validity of the OCSP proof. The checking done by Exim/OpenSSL
27879 noted this as invalid overall, but the re-fetch script did not.
27880 .endd
27881
27882
27883
27884
27885 .section "Configuring an Exim client to use TLS" "SECID185"
27886 .cindex "cipher" "logging"
27887 .cindex "log" "TLS cipher"
27888 .cindex "log" "distinguished name"
27889 .cindex "TLS" "configuring an Exim client"
27890 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
27891 deliveries as well as to incoming, the latter one causing logging of the
27892 server certificate's DN. The remaining client configuration for TLS is all
27893 within the &(smtp)& transport.
27894
27895 It is not necessary to set any options to have TLS work in the &(smtp)&
27896 transport. If Exim is built with TLS support, and TLS is advertised by a
27897 server, the &(smtp)& transport always tries to start a TLS session. However,
27898 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
27899 transport) to a list of server hosts for which TLS should not be used.
27900
27901 If you do not want Exim to attempt to send messages unencrypted when an attempt
27902 to set up an encrypted connection fails in any way, you can set
27903 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
27904 those hosts, delivery is always deferred if an encrypted connection cannot be
27905 set up. If there are any other hosts for the address, they are tried in the
27906 usual way.
27907
27908 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
27909 the message unencrypted. It always does this if the response to STARTTLS is
27910 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
27911 session after a success response code, what happens is controlled by the
27912 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
27913 delivery to this host is deferred, and other hosts (if available) are tried. If
27914 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
27915 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
27916 negotiation fails, Exim closes the current connection (because it is in an
27917 unknown state), opens a new one to the same host, and then tries the delivery
27918 unencrypted.
27919
27920 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
27921 transport provide the client with a certificate, which is passed to the server
27922 if it requests it. If the server is Exim, it will request a certificate only if
27923 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
27924
27925 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
27926 specifies a collection of expected server certificates.
27927 These may be
27928 the system default set (depending on library version),
27929 a file,
27930 or (depending on library version) a directory.
27931 The client verifies the server's certificate
27932 against this collection, taking into account any revoked certificates that are
27933 in the list defined by &%tls_crl%&.
27934 Failure to verify fails the TLS connection unless either of the
27935 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
27936
27937 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
27938 certificate verification to the listed servers. Verification either must
27939 or need not succeed respectively.
27940
27941 The &(smtp)& transport has two OCSP-related options:
27942 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
27943 is requested and required for the connection to proceed. The default
27944 value is empty.
27945 &%hosts_request_ocsp%&; a host-list for which (additionally)
27946 a Certificate Status is requested (but not necessarily verified). The default
27947 value is "*" meaning that requests are made unless configured
27948 otherwise.
27949
27950 The host(s) should also be in &%hosts_require_tls%&, and
27951 &%tls_verify_certificates%& configured for the transport,
27952 for OCSP to be relevant.
27953
27954 If
27955 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
27956 list of permitted cipher suites. If either of these checks fails, delivery to
27957 the current host is abandoned, and the &(smtp)& transport tries to deliver to
27958 alternative hosts, if any.
27959
27960 &*Note*&:
27961 These options must be set in the &(smtp)& transport for Exim to use TLS when it
27962 is operating as a client. Exim does not assume that a server certificate (set
27963 by the global options of the same name) should also be used when operating as a
27964 client.
27965
27966 .vindex "&$host$&"
27967 .vindex "&$host_address$&"
27968 All the TLS options in the &(smtp)& transport are expanded before use, with
27969 &$host$& and &$host_address$& containing the name and address of the server to
27970 which the client is connected. Forced failure of an expansion causes Exim to
27971 behave as if the relevant option were unset.
27972
27973 .vindex &$tls_out_bits$&
27974 .vindex &$tls_out_cipher$&
27975 .vindex &$tls_out_peerdn$&
27976 .vindex &$tls_out_sni$&
27977 Before an SMTP connection is established, the
27978 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
27979 variables are emptied. (Until the first connection, they contain the values
27980 that were set when the message was received.) If STARTTLS is subsequently
27981 successfully obeyed, these variables are set to the relevant values for the
27982 outgoing connection.
27983
27984
27985
27986 .section "Use of TLS Server Name Indication" "SECTtlssni"
27987 .cindex "TLS" "Server Name Indication"
27988 .vindex "&$tls_in_sni$&"
27989 .oindex "&%tls_in_sni%&"
27990 With TLS1.0 or above, there is an extension mechanism by which extra
27991 information can be included at various points in the protocol. One of these
27992 extensions, documented in RFC 6066 (and before that RFC 4366) is
27993 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
27994 client in the initial handshake, so that the server can examine the servername
27995 within and possibly choose to use different certificates and keys (and more)
27996 for this session.
27997
27998 This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
27999 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
28000 address.
28001
28002 With SMTP to MX, there are the same problems here as in choosing the identity
28003 against which to validate a certificate: you can't rely on insecure DNS to
28004 provide the identity which you then cryptographically verify. So this will
28005 be of limited use in that environment.
28006
28007 With SMTP to Submission, there is a well-defined hostname which clients are
28008 connecting to and can validate certificates against. Thus clients &*can*&
28009 choose to include this information in the TLS negotiation. If this becomes
28010 wide-spread, then hosters can choose to present different certificates to
28011 different clients. Or even negotiate different cipher suites.
28012
28013 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
28014 if not empty, will be sent on a TLS session as part of the handshake. There's
28015 nothing more to it. Choosing a sensible value not derived insecurely is the
28016 only point of caution. The &$tls_out_sni$& variable will be set to this string
28017 for the lifetime of the client connection (including during authentication).
28018
28019 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
28020 received from a client.
28021 It can be logged with the &%log_selector%& item &`+tls_sni`&.
28022
28023 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
28024 option (prior to expansion) then the following options will be re-expanded
28025 during TLS session handshake, to permit alternative values to be chosen:
28026
28027 .ilist
28028 &%tls_certificate%&
28029 .next
28030 &%tls_crl%&
28031 .next
28032 &%tls_privatekey%&
28033 .next
28034 &%tls_verify_certificates%&
28035 .next
28036 &%tls_ocsp_file%&
28037 .endlist
28038
28039 Great care should be taken to deal with matters of case, various injection
28040 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
28041 can always be referenced; it is important to remember that &$tls_in_sni$& is
28042 arbitrary unverified data provided prior to authentication.
28043 Further, the initial certificate is loaded before SNI is arrived, so
28044 an expansion for &%tls_certificate%& must have a default which is used
28045 when &$tls_in_sni$& is empty.
28046
28047 The Exim developers are proceeding cautiously and so far no other TLS options
28048 are re-expanded.
28049
28050 When Exim is built against OpenSSL, OpenSSL must have been built with support
28051 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
28052 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
28053 see &`-servername`& in the output, then OpenSSL has support.
28054
28055 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
28056 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
28057 built, then you have SNI support).
28058
28059
28060
28061 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
28062 "SECTmulmessam"
28063 .cindex "multiple SMTP deliveries with TLS"
28064 .cindex "TLS" "multiple message deliveries"
28065 Exim sends multiple messages down the same TCP/IP connection by starting up
28066 an entirely new delivery process for each message, passing the socket from
28067 one process to the next. This implementation does not fit well with the use
28068 of TLS, because there is quite a lot of state information associated with a TLS
28069 connection, not just a socket identification. Passing all the state information
28070 to a new process is not feasible. Consequently, for sending using TLS Exim
28071 starts an additional proxy process for handling the encryption, piping the
28072 unencrypted data stream from and to the delivery processes.
28073
28074 An older mode of operation can be enabled on a per-host basis by the
28075 &%hosts_noproxy_tls%& option on the &(smtp)& transport. If the host matches
28076 this list the proxy process described above is not used; instead Exim
28077 shuts down an existing TLS session being run by the delivery process
28078 before passing the socket to a new process. The new process may then
28079 try to start a new TLS session, and if successful, may try to re-authenticate
28080 if AUTH is in use, before sending the next message.
28081
28082 The RFC is not clear as to whether or not an SMTP session continues in clear
28083 after TLS has been shut down, or whether TLS may be restarted again later, as
28084 just described. However, if the server is Exim, this shutdown and
28085 reinitialization works. It is not known which (if any) other servers operate
28086 successfully if the client closes a TLS session and continues with unencrypted
28087 SMTP, but there are certainly some that do not work. For such servers, Exim
28088 should not pass the socket to another process, because the failure of the
28089 subsequent attempt to use it would cause Exim to record a temporary host error,
28090 and delay other deliveries to that host.
28091
28092 To test for this case, Exim sends an EHLO command to the server after
28093 closing down the TLS session. If this fails in any way, the connection is
28094 closed instead of being passed to a new delivery process, but no retry
28095 information is recorded.
28096
28097 There is also a manual override; you can set &%hosts_nopass_tls%& on the
28098 &(smtp)& transport to match those hosts for which Exim should not pass
28099 connections to new processes if TLS has been used.
28100
28101
28102
28103
28104 .section "Certificates and all that" "SECTcerandall"
28105 .cindex "certificate" "references to discussion"
28106 In order to understand fully how TLS works, you need to know about
28107 certificates, certificate signing, and certificate authorities. This is not the
28108 place to give a tutorial, especially as I do not know very much about it
28109 myself. Some helpful introduction can be found in the FAQ for the SSL addition
28110 to Apache, currently at
28111 .display
28112 &url(http://www.modssl.org/docs/2.7/ssl_faq.html#ToC24)
28113 .endd
28114 Other parts of the &'modssl'& documentation are also helpful, and have
28115 links to further files.
28116 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
28117 0-201-61598-3), contains both introductory and more in-depth descriptions.
28118 Some sample programs taken from the book are available from
28119 .display
28120 &url(http://www.rtfm.com/openssl-examples/)
28121 .endd
28122
28123
28124 .section "Certificate chains" "SECID186"
28125 The file named by &%tls_certificate%& may contain more than one
28126 certificate. This is useful in the case where the certificate that is being
28127 sent is validated by an intermediate certificate which the other end does
28128 not have. Multiple certificates must be in the correct order in the file.
28129 First the host's certificate itself, then the first intermediate
28130 certificate to validate the issuer of the host certificate, then the next
28131 intermediate certificate to validate the issuer of the first intermediate
28132 certificate, and so on, until finally (optionally) the root certificate.
28133 The root certificate must already be trusted by the recipient for
28134 validation to succeed, of course, but if it's not preinstalled, sending the
28135 root certificate along with the rest makes it available for the user to
28136 install if the receiving end is a client MUA that can interact with a user.
28137
28138 Note that certificates using MD5 are unlikely to work on today's Internet;
28139 even if your libraries allow loading them for use in Exim when acting as a
28140 server, increasingly clients will not accept such certificates. The error
28141 diagnostics in such a case can be frustratingly vague.
28142
28143
28144
28145 .section "Self-signed certificates" "SECID187"
28146 .cindex "certificate" "self-signed"
28147 You can create a self-signed certificate using the &'req'& command provided
28148 with OpenSSL, like this:
28149 . ==== Do not shorten the duration here without reading and considering
28150 . ==== the text below. Please leave it at 9999 days.
28151 .code
28152 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
28153 -days 9999 -nodes
28154 .endd
28155 &_file1_& and &_file2_& can be the same file; the key and the certificate are
28156 delimited and so can be identified independently. The &%-days%& option
28157 specifies a period for which the certificate is valid. The &%-nodes%& option is
28158 important: if you do not set it, the key is encrypted with a passphrase
28159 that you are prompted for, and any use that is made of the key causes more
28160 prompting for the passphrase. This is not helpful if you are going to use
28161 this certificate and key in an MTA, where prompting is not possible.
28162
28163 . ==== I expect to still be working 26 years from now. The less technical
28164 . ==== debt I create, in terms of storing up trouble for my later years, the
28165 . ==== happier I will be then. We really have reached the point where we
28166 . ==== should start, at the very least, provoking thought and making folks
28167 . ==== pause before proceeding, instead of leaving all the fixes until two
28168 . ==== years before 2^31 seconds after the 1970 Unix epoch.
28169 . ==== -pdp, 2012
28170 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
28171 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
28172 the above command might produce a date in the past. Think carefully about
28173 the lifetime of the systems you're deploying, and either reduce the duration
28174 of the certificate or reconsider your platform deployment. (At time of
28175 writing, reducing the duration is the most likely choice, but the inexorable
28176 progression of time takes us steadily towards an era where this will not
28177 be a sensible resolution).
28178
28179 A self-signed certificate made in this way is sufficient for testing, and
28180 may be adequate for all your requirements if you are mainly interested in
28181 encrypting transfers, and not in secure identification.
28182
28183 However, many clients require that the certificate presented by the server be a
28184 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
28185 certificate. In this situation, the self-signed certificate described above
28186 must be installed on the client host as a trusted root &'certification
28187 authority'& (CA), and the certificate used by Exim must be a user certificate
28188 signed with that self-signed certificate.
28189
28190 For information on creating self-signed CA certificates and using them to sign
28191 user certificates, see the &'General implementation overview'& chapter of the
28192 Open-source PKI book, available online at
28193 &url(http://ospkibook.sourceforge.net/).
28194 .ecindex IIDencsmtp1
28195 .ecindex IIDencsmtp2
28196
28197
28198
28199 .section DANE "SECDANE"
28200 .cindex DANE
28201 DNS-based Authentication of Named Entities, as applied to SMTP over TLS, provides assurance to a client that
28202 it is actually talking to the server it wants to rather than some attacker operating a Man In The Middle (MITM)
28203 operation. The latter can terminate the TLS connection you make, and make another one to the server (so both
28204 you and the server still think you have an encrypted connection) and, if one of the "well known" set of
28205 Certificate Authorities has been suborned - something which *has* been seen already (2014), a verifiable
28206 certificate (if you're using normal root CAs, eg. the Mozilla set, as your trust anchors).
28207
28208 What DANE does is replace the CAs with the DNS as the trust anchor. The assurance is limited to a) the possibility
28209 that the DNS has been suborned, b) mistakes made by the admins of the target server. The attack surface presented
28210 by (a) is thought to be smaller than that of the set of root CAs.
28211
28212 It also allows the server to declare (implicitly) that connections to it should use TLS. An MITM could simply
28213 fail to pass on a server's STARTTLS.
28214
28215 DANE scales better than having to maintain (and side-channel communicate) copies of server certificates
28216 for every possible target server. It also scales (slightly) better than having to maintain on an SMTP
28217 client a copy of the standard CAs bundle. It also means not having to pay a CA for certificates.
28218
28219 DANE requires a server operator to do three things: 1) run DNSSEC. This provides assurance to clients
28220 that DNS lookups they do for the server have not been tampered with. The domain MX record applying
28221 to this server, its A record, its TLSA record and any associated CNAME records must all be covered by
28222 DNSSEC.
28223 2) add TLSA DNS records. These say what the server certificate for a TLS connection should be.
28224 3) offer a server certificate, or certificate chain, in TLS connections which is is anchored by one of the TLSA records.
28225
28226 There are no changes to Exim specific to server-side operation of DANE.
28227 Support for client-side operation of DANE can be included at compile time by defining SUPPORT_DANE=yes
28228 in &_Local/Makefile_&.
28229 If it has been included, the macro "_HAVE_DANE" will be defined.
28230
28231 The TLSA record for the server may have "certificate usage" of DANE-TA(2) or DANE-EE(3).
28232 These are the "Trust Anchor" and "End Entity" variants.
28233 The latter specifies the End Entity directly, i.e. the certificate involved is that of the server
28234 (and if only DANE-EE is used then it should be the sole one transmitted during the TLS handshake);
28235 this is appropriate for a single system, using a self-signed certificate.
28236 DANE-TA usage is effectively declaring a specific CA to be used; this might be a private CA or a public,
28237 well-known one.
28238 A private CA at simplest is just a self-signed certificate (with certain
28239 attributes) which is used to sign cerver certificates, but running one securely
28240 does require careful arrangement.
28241 With DANE-TA, as implemented in Exim and commonly in other MTAs,
28242 the server TLS handshake must transmit the entire certificate chain from CA to server-certificate.
28243 DANE-TA is commonly used for several services and/or servers, each having a TLSA query-domain CNAME record,
28244 all of which point to a single TLSA record.
28245 DANE-TA and DANE-EE can both be used together.
28246
28247 .new
28248 Our recommendation is to use DANE with a certificate from a public CA,
28249 because this enables a variety of strategies for remote clients to verify
28250 your certificate.
28251 You can then publish information both via DANE and another technology,
28252 "MTA-STS", described below.
28253
28254 When you use DANE-TA to publish trust anchor information, you ask entities
28255 outside your administrative control to trust the Certificate Authority for
28256 connections to you.
28257 If using a private CA then you should expect others to still apply the
28258 technical criteria they'd use for a public CA to your certificates.
28259 In particular, you should probably try to follow current best practices for CA
28260 operation around hash algorithms and key sizes.
28261 Do not expect other organizations to lower their security expectations just
28262 because a particular profile might be reasonable for your own internal use.
28263
28264 When this text was last updated, this in practice means to avoid use of SHA-1
28265 and MD5; if using RSA to use key sizes of at least 2048 bits (and no larger
28266 than 4096, for interoperability); to use keyUsage fields correctly; to use
28267 random serial numbers.
28268 The list of requirements is subject to change as best practices evolve.
28269 If you're not already using a private CA, or it doesn't meet these
28270 requirements, then we encourage you to avoid all these issues and use a public
28271 CA such as &url(https://letsencrypt.org/,Let's Encrypt) instead.
28272 .wen
28273
28274 The TLSA record should have a Selector field of SPKI(1) and a Matching Type field of SHA2-512(2).
28275
28276 At the time of writing, &url(https://www.huque.com/bin/gen_tlsa)
28277 is useful for quickly generating TLSA records; and commands like
28278
28279 .code
28280 openssl x509 -in -pubkey -noout <certificate.pem \
28281 | openssl rsa -outform der -pubin 2>/dev/null \
28282 | openssl sha512 \
28283 | awk '{print $2}'
28284 .endd
28285
28286 are workable for 4th-field hashes.
28287
28288 For use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName).
28289
28290 .new
28291 The Certificate issued by the CA published in the DANE-TA model should be
28292 issued using a strong hash algorithm.
28293 Exim, and importantly various other MTAs sending to you, will not
28294 re-enable hash algorithms which have been disabled by default in TLS
28295 libraries.
28296 This means no MD5 and no SHA-1. SHA2-256 is the minimum for reliable
28297 interoperability (and probably the maximum too, in 2018).
28298 .wen
28299
28300 The use of OCSP-stapling should be considered, allowing for fast revocation of certificates (which would otherwise
28301 be limited by the DNS TTL on the TLSA records). However, this is likely to only be usable with DANE-TA. NOTE: the
28302 default of requesting OCSP for all hosts is modified iff DANE is in use, to:
28303
28304 .code
28305 hosts_request_ocsp = ${if or { {= {0}{$tls_out_tlsa_usage}} \
28306 {= {4}{$tls_out_tlsa_usage}} } \
28307 {*}{}}
28308 .endd
28309
28310 The (new) variable &$tls_out_tlsa_usage$& is a bitfield with numbered bits set for TLSA record usage codes.
28311 The zero above means DANE was not in use, the four means that only DANE-TA usage TLSA records were
28312 found. If the definition of &%hosts_request_ocsp%& includes the
28313 string "tls_out_tlsa_usage", they are re-expanded in time to
28314 control the OCSP request.
28315
28316 This modification of hosts_request_ocsp is only done if it has the default value of "*". Admins who change it, and
28317 those who use &%hosts_require_ocsp%&, should consider the interaction with DANE in their OCSP settings.
28318
28319
28320 For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%&
28321 and &%dane_require_tls_ciphers%&.
28322 The require variant will result in failure if the target host is not DNSSEC-secured.
28323
28324 DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
28325
28326 A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using dnssec.
28327 If a TLSA lookup is done and succeeds, a DANE-verified TLS connection
28328 will be required for the host. If it does not, the host will not
28329 be used; there is no fallback to non-DANE or non-TLS.
28330
28331 If DANE is requested and usable, then the TLS cipher list configuration
28332 prefers to use the option &%dane_require_tls_ciphers%& and falls
28333 back to &%tls_require_ciphers%& only if that is unset.
28334 This lets you configure "decent crypto" for DANE and "better than nothing
28335 crypto" as the default. Note though that while GnuTLS lets the string control
28336 which versions of TLS/SSL will be negotiated, OpenSSL does not and you're
28337 limited to ciphersuite constraints.
28338
28339 If DANE is requested and useable (see above) the following transport options are ignored:
28340 .code
28341 hosts_require_tls
28342 tls_verify_hosts
28343 tls_try_verify_hosts
28344 tls_verify_certificates
28345 tls_crl
28346 tls_verify_cert_hostnames
28347 .endd
28348
28349 If DANE is not usable, whether requested or not, and CA-anchored
28350 verification evaluation is wanted, the above variables should be set appropriately.
28351
28352 Currently the &%dnssec_request_domains%& must be active and &%dnssec_require_domains%& is ignored.
28353
28354 If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane".
28355
28356 There is a new variable &$tls_out_dane$& which will have "yes" if
28357 verification succeeded using DANE and "no" otherwise (only useful
28358 in combination with events; see &<<CHAPevents>>&),
28359 and a new variable &$tls_out_tlsa_usage$& (detailed above).
28360
28361 .cindex DANE reporting
28362 An event (see &<<CHAPevents>>&) of type "dane:fail" will be raised on failures
28363 to achieve DANE-verified connection, if one was either requested and offered, or
28364 required. This is intended to support TLS-reporting as defined in
28365 &url(https://tools.ietf.org/html/draft-ietf-uta-smtp-tlsrpt-17).
28366 The &$event_data$& will be one of the Result Types defined in
28367 Section 4.3 of that document.
28368
28369 Under GnuTLS, DANE is only supported from version 3.0.0 onwards.
28370
28371 DANE is specified in published RFCs and decouples certificate authority trust
28372 selection from a "race to the bottom" of "you must trust everything for mail
28373 to get through". There is an alternative technology called MTA-STS, which
28374 instead publishes MX trust anchor information on an HTTPS website. At the
28375 time this text was last updated, MTA-STS was still a draft, not yet an RFC.
28376 Exim has no support for MTA-STS as a client, but Exim mail server operators
28377 can choose to publish information describing their TLS configuration using
28378 MTA-STS to let those clients who do use that protocol derive trust
28379 information.
28380
28381 The MTA-STS design requires a certificate from a public Certificate Authority
28382 which is recognized by clients sending to you.
28383 That selection of which CAs are trusted by others is outside your control.
28384
28385 The most interoperable course of action is probably to use
28386 &url(https://letsencrypt.org/,Let's Encrypt), with automated certificate
28387 renewal; to publish the anchor information in DNSSEC-secured DNS via TLSA
28388 records for DANE clients (such as Exim and Postfix) and to publish anchor
28389 information for MTA-STS as well. This is what is done for the &'exim.org'&
28390 domain itself (with caveats around occasionally broken MTA-STS because of
28391 incompatible specification changes prior to reaching RFC status).
28392
28393
28394
28395 . ////////////////////////////////////////////////////////////////////////////
28396 . ////////////////////////////////////////////////////////////////////////////
28397
28398 .chapter "Access control lists" "CHAPACL"
28399 .scindex IIDacl "&ACL;" "description"
28400 .cindex "control of incoming mail"
28401 .cindex "message" "controlling incoming"
28402 .cindex "policy control" "access control lists"
28403 Access Control Lists (ACLs) are defined in a separate section of the run time
28404 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
28405 name, terminated by a colon. Here is a complete ACL section that contains just
28406 one very small ACL:
28407 .code
28408 begin acl
28409 small_acl:
28410 accept hosts = one.host.only
28411 .endd
28412 You can have as many lists as you like in the ACL section, and the order in
28413 which they appear does not matter. The lists are self-terminating.
28414
28415 The majority of ACLs are used to control Exim's behaviour when it receives
28416 certain SMTP commands. This applies both to incoming TCP/IP connections, and
28417 when a local process submits a message using SMTP by specifying the &%-bs%&
28418 option. The most common use is for controlling which recipients are accepted
28419 in incoming messages. In addition, you can define an ACL that is used to check
28420 local non-SMTP messages. The default configuration file contains an example of
28421 a realistic ACL for checking RCPT commands. This is discussed in chapter
28422 &<<CHAPdefconfil>>&.
28423
28424
28425 .section "Testing ACLs" "SECID188"
28426 The &%-bh%& command line option provides a way of testing your ACL
28427 configuration locally by running a fake SMTP session with which you interact.
28428
28429
28430 .section "Specifying when ACLs are used" "SECID189"
28431 .cindex "&ACL;" "options for specifying"
28432 In order to cause an ACL to be used, you have to name it in one of the relevant
28433 options in the main part of the configuration. These options are:
28434 .cindex "AUTH" "ACL for"
28435 .cindex "DATA" "ACLs for"
28436 .cindex "ETRN" "ACL for"
28437 .cindex "EXPN" "ACL for"
28438 .cindex "HELO" "ACL for"
28439 .cindex "EHLO" "ACL for"
28440 .cindex "DKIM" "ACL for"
28441 .cindex "MAIL" "ACL for"
28442 .cindex "QUIT, ACL for"
28443 .cindex "RCPT" "ACL for"
28444 .cindex "STARTTLS, ACL for"
28445 .cindex "VRFY" "ACL for"
28446 .cindex "SMTP" "connection, ACL for"
28447 .cindex "non-SMTP messages" "ACLs for"
28448 .cindex "MIME content scanning" "ACL for"
28449 .cindex "PRDR" "ACL for"
28450
28451 .table2 140pt
28452 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
28453 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
28454 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
28455 .irow &%acl_smtp_auth%& "ACL for AUTH"
28456 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
28457 .irow &%acl_smtp_data%& "ACL after DATA is complete"
28458 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
28459 .irow &%acl_smtp_dkim%& "ACL for each DKIM signer"
28460 .irow &%acl_smtp_etrn%& "ACL for ETRN"
28461 .irow &%acl_smtp_expn%& "ACL for EXPN"
28462 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
28463 .irow &%acl_smtp_mail%& "ACL for MAIL"
28464 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
28465 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
28466 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
28467 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
28468 .irow &%acl_smtp_quit%& "ACL for QUIT"
28469 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
28470 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
28471 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
28472 .endtable
28473
28474 For example, if you set
28475 .code
28476 acl_smtp_rcpt = small_acl
28477 .endd
28478 the little ACL defined above is used whenever Exim receives a RCPT command
28479 in an SMTP dialogue. The majority of policy tests on incoming messages can be
28480 done when RCPT commands arrive. A rejection of RCPT should cause the
28481 sending MTA to give up on the recipient address contained in the RCPT
28482 command, whereas rejection at other times may cause the client MTA to keep on
28483 trying to deliver the message. It is therefore recommended that you do as much
28484 testing as possible at RCPT time.
28485
28486
28487 .section "The non-SMTP ACLs" "SECID190"
28488 .cindex "non-SMTP messages" "ACLs for"
28489 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
28490 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
28491 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
28492 the state of the SMTP connection such as encryption and authentication) are not
28493 relevant and are forbidden in these ACLs. However, the sender and recipients
28494 are known, so the &%senders%& and &%sender_domains%& conditions and the
28495 &$sender_address$& and &$recipients$& variables can be used. Variables such as
28496 &$authenticated_sender$& are also available. You can specify added header lines
28497 in any of these ACLs.
28498
28499 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
28500 non-SMTP message, before any of the message has been read. (This is the
28501 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
28502 batched SMTP input, it runs after the DATA command has been reached. The
28503 result of this ACL is ignored; it cannot be used to reject a message. If you
28504 really need to, you could set a value in an ACL variable here and reject based
28505 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
28506 controls, and in particular, it can be used to set
28507 .code
28508 control = suppress_local_fixups
28509 .endd
28510 This cannot be used in the other non-SMTP ACLs because by the time they are
28511 run, it is too late.
28512
28513 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
28514 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
28515
28516 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
28517 kind of rejection is treated as permanent, because there is no way of sending a
28518 temporary error for these kinds of message.
28519
28520
28521 .section "The SMTP connect ACL" "SECID191"
28522 .cindex "SMTP" "connection, ACL for"
28523 .oindex &%smtp_banner%&
28524 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
28525 session, after the test specified by &%host_reject_connection%& (which is now
28526 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
28527 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
28528 the message override the banner message that is otherwise specified by the
28529 &%smtp_banner%& option.
28530
28531
28532 .section "The EHLO/HELO ACL" "SECID192"
28533 .cindex "EHLO" "ACL for"
28534 .cindex "HELO" "ACL for"
28535 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
28536 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
28537 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
28538 Note that a client may issue more than one EHLO or HELO command in an SMTP
28539 session, and indeed is required to issue a new EHLO or HELO after successfully
28540 setting up encryption following a STARTTLS command.
28541
28542 Note also that a deny neither forces the client to go away nor means that
28543 mail will be refused on the connection. Consider checking for
28544 &$sender_helo_name$& being defined in a MAIL or RCPT ACL to do that.
28545
28546 If the command is accepted by an &%accept%& verb that has a &%message%&
28547 modifier, the message may not contain more than one line (it will be truncated
28548 at the first newline and a panic logged if it does). Such a message cannot
28549 affect the EHLO options that are listed on the second and subsequent lines of
28550 an EHLO response.
28551
28552
28553 .section "The DATA ACLs" "SECID193"
28554 .cindex "DATA" "ACLs for"
28555 Two ACLs are associated with the DATA command, because it is two-stage
28556 command, with two responses being sent to the client.
28557 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
28558 is obeyed. This gives you control after all the RCPT commands, but before
28559 the message itself is received. It offers the opportunity to give a negative
28560 response to the DATA command before the data is transmitted. Header lines
28561 added by MAIL or RCPT ACLs are not visible at this time, but any that
28562 are defined here are visible when the &%acl_smtp_data%& ACL is run.
28563
28564 You cannot test the contents of the message, for example, to verify addresses
28565 in the headers, at RCPT time or when the DATA command is received. Such
28566 tests have to appear in the ACL that is run after the message itself has been
28567 received, before the final response to the DATA command is sent. This is
28568 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
28569 associated with the DATA command.
28570
28571 .cindex CHUNKING "BDAT command"
28572 .cindex BDAT "SMTP command"
28573 .cindex "RFC 3030" CHUNKING
28574 If CHUNKING was advertised and a BDAT command sequence is received,
28575 the &%acl_smtp_predata%& ACL is not run.
28576 . XXX why not? It should be possible, for the first BDAT.
28577 The &%acl_smtp_data%& is run after the last BDAT command and all of
28578 the data specified is received.
28579
28580 For both of these ACLs, it is not possible to reject individual recipients. An
28581 error response rejects the entire message. Unfortunately, it is known that some
28582 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
28583 before or after the data) correctly &-- they keep the message on their queues
28584 and try again later, but that is their problem, though it does waste some of
28585 your resources.
28586
28587 The &%acl_smtp_data%& ACL is run after
28588 the &%acl_smtp_data_prdr%&,
28589 the &%acl_smtp_dkim%&
28590 and the &%acl_smtp_mime%& ACLs.
28591
28592 .section "The SMTP DKIM ACL" "SECTDKIMACL"
28593 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
28594 enabled (which is the default).
28595
28596 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
28597 received, and is executed for each DKIM signature found in a message. If not
28598 otherwise specified, the default action is to accept.
28599
28600 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
28601
28602 For details on the operation of DKIM, see section &<<SECDKIM>>&.
28603
28604
28605 .section "The SMTP MIME ACL" "SECID194"
28606 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
28607 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
28608
28609 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
28610
28611
28612 .section "The SMTP PRDR ACL" "SECTPRDRACL"
28613 .cindex "PRDR" "ACL for"
28614 .oindex "&%prdr_enable%&"
28615 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
28616 with PRDR support enabled (which is the default).
28617 It becomes active only when the PRDR feature is negotiated between
28618 client and server for a message, and more than one recipient
28619 has been accepted.
28620
28621 The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
28622 has been received, and is executed once for each recipient of the message
28623 with &$local_part$& and &$domain$& valid.
28624 The test may accept, defer or deny for individual recipients.
28625 The &%acl_smtp_data%& will still be called after this ACL and
28626 can reject the message overall, even if this ACL has accepted it
28627 for some or all recipients.
28628
28629 PRDR may be used to support per-user content filtering. Without it
28630 one must defer any recipient after the first that has a different
28631 content-filter configuration. With PRDR, the RCPT-time check
28632 .cindex "PRDR" "variable for"
28633 for this can be disabled when the variable &$prdr_requested$&
28634 is &"yes"&.
28635 Any required difference in behaviour of the main DATA-time
28636 ACL should however depend on the PRDR-time ACL having run, as Exim
28637 will avoid doing so in some situations (e.g. single-recipient mails).
28638
28639 See also the &%prdr_enable%& global option
28640 and the &%hosts_try_prdr%& smtp transport option.
28641
28642 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
28643 If the ACL is not defined, processing completes as if
28644 the feature was not requested by the client.
28645
28646 .section "The QUIT ACL" "SECTQUITACL"
28647 .cindex "QUIT, ACL for"
28648 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
28649 does not affect the response code to QUIT, which is always 221. Thus, the ACL
28650 does not in fact control any access.
28651 For this reason, it may only accept
28652 or warn as its final result.
28653
28654 This ACL can be used for tasks such as custom logging at the end of an SMTP
28655 session. For example, you can use ACL variables in other ACLs to count
28656 messages, recipients, etc., and log the totals at QUIT time using one or
28657 more &%logwrite%& modifiers on a &%warn%& verb.
28658
28659 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
28660 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
28661
28662 You do not need to have a final &%accept%&, but if you do, you can use a
28663 &%message%& modifier to specify custom text that is sent as part of the 221
28664 response to QUIT.
28665
28666 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
28667 failure (for example, failure to open a log file, or when Exim is bombing out
28668 because it has detected an unrecoverable error), all SMTP commands from the
28669 client are given temporary error responses until QUIT is received or the
28670 connection is closed. In these special cases, the QUIT ACL does not run.
28671
28672
28673 .section "The not-QUIT ACL" "SECTNOTQUITACL"
28674 .vindex &$acl_smtp_notquit$&
28675 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
28676 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
28677 trouble, such as being unable to write to its log files, this ACL is not run,
28678 because it might try to do things (such as write to log files) that make the
28679 situation even worse.
28680
28681 Like the QUIT ACL, this ACL is provided to make it possible to do customized
28682 logging or to gather statistics, and its outcome is ignored. The &%delay%&
28683 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
28684 and &%warn%&.
28685
28686 .vindex &$smtp_notquit_reason$&
28687 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
28688 to a string that indicates the reason for the termination of the SMTP
28689 connection. The possible values are:
28690 .table2
28691 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
28692 .irow &`bad-commands`& "Too many unknown or non-mail commands"
28693 .irow &`command-timeout`& "Timeout while reading SMTP commands"
28694 .irow &`connection-lost`& "The SMTP connection has been lost"
28695 .irow &`data-timeout`& "Timeout while reading message data"
28696 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
28697 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
28698 .irow &`signal-exit`& "SIGTERM or SIGINT"
28699 .irow &`synchronization-error`& "SMTP synchronization error"
28700 .irow &`tls-failed`& "TLS failed to start"
28701 .endtable
28702 In most cases when an SMTP connection is closed without having received QUIT,
28703 Exim sends an SMTP response message before actually closing the connection.
28704 With the exception of the &`acl-drop`& case, the default message can be
28705 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
28706 &%drop%& verb in another ACL, it is the message from the other ACL that is
28707 used.
28708
28709
28710 .section "Finding an ACL to use" "SECID195"
28711 .cindex "&ACL;" "finding which to use"
28712 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
28713 you can use different ACLs in different circumstances. For example,
28714 .code
28715 acl_smtp_rcpt = ${if ={25}{$interface_port} \
28716 {acl_check_rcpt} {acl_check_rcpt_submit} }
28717 .endd
28718 In the default configuration file there are some example settings for
28719 providing an RFC 4409 message &"submission"& service on port 587 and
28720 an RFC 8314 &"submissions"& service on port 465. You can use a string
28721 expansion like this to choose an ACL for MUAs on these ports which is
28722 more appropriate for this purpose than the default ACL on port 25.
28723
28724 The expanded string does not have to be the name of an ACL in the
28725 configuration file; there are other possibilities. Having expanded the
28726 string, Exim searches for an ACL as follows:
28727
28728 .ilist
28729 If the string begins with a slash, Exim uses it as a file name, and reads its
28730 contents as an ACL. The lines are processed in the same way as lines in the
28731 Exim configuration file. In particular, continuation lines are supported, blank
28732 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
28733 If the file does not exist or cannot be read, an error occurs (typically
28734 causing a temporary failure of whatever caused the ACL to be run). For example:
28735 .code
28736 acl_smtp_data = /etc/acls/\
28737 ${lookup{$sender_host_address}lsearch\
28738 {/etc/acllist}{$value}{default}}
28739 .endd
28740 This looks up an ACL file to use on the basis of the host's IP address, falling
28741 back to a default if the lookup fails. If an ACL is successfully read from a
28742 file, it is retained in memory for the duration of the Exim process, so that it
28743 can be re-used without having to re-read the file.
28744 .next
28745 If the string does not start with a slash, and does not contain any spaces,
28746 Exim searches the ACL section of the configuration for an ACL whose name
28747 matches the string.
28748 .next
28749 If no named ACL is found, or if the string contains spaces, Exim parses
28750 the string as an inline ACL. This can save typing in cases where you just
28751 want to have something like
28752 .code
28753 acl_smtp_vrfy = accept
28754 .endd
28755 in order to allow free use of the VRFY command. Such a string may contain
28756 newlines; it is processed in the same way as an ACL that is read from a file.
28757 .endlist
28758
28759
28760
28761
28762 .section "ACL return codes" "SECID196"
28763 .cindex "&ACL;" "return codes"
28764 Except for the QUIT ACL, which does not affect the SMTP return code (see
28765 section &<<SECTQUITACL>>& above), the result of running an ACL is either
28766 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
28767 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
28768 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
28769 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
28770 This also causes a 4&'xx'& return code.
28771
28772 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
28773 &"deny"&, because there is no mechanism for passing temporary errors to the
28774 submitters of non-SMTP messages.
28775
28776
28777 ACLs that are relevant to message reception may also return &"discard"&. This
28778 has the effect of &"accept"&, but causes either the entire message or an
28779 individual recipient address to be discarded. In other words, it is a
28780 blackholing facility. Use it with care.
28781
28782 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
28783 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
28784 RCPT ACL is to discard just the one recipient address. If there are no
28785 recipients left when the message's data is received, the DATA ACL is not
28786 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
28787 remaining recipients. The &"discard"& return is not permitted for the
28788 &%acl_smtp_predata%& ACL.
28789
28790 If the ACL for VRFY returns &"accept"&, a recipient verify (without callout)
28791 is done on the address and the result determines the SMTP response.
28792
28793
28794 .cindex "&[local_scan()]& function" "when all recipients discarded"
28795 The &[local_scan()]& function is always run, even if there are no remaining
28796 recipients; it may create new recipients.
28797
28798
28799
28800 .section "Unset ACL options" "SECID197"
28801 .cindex "&ACL;" "unset options"
28802 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
28803 all the same. &*Note*&: These defaults apply only when the relevant ACL is
28804 not defined at all. For any defined ACL, the default action when control
28805 reaches the end of the ACL statements is &"deny"&.
28806
28807 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
28808 these two are ACLs that are used only for their side effects. They cannot be
28809 used to accept or reject anything.
28810
28811 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
28812 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
28813 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
28814 when the ACL is not defined is &"accept"&.
28815
28816 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
28817 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
28818 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
28819 messages over an SMTP connection. For an example, see the ACL in the default
28820 configuration file.
28821
28822
28823
28824
28825 .section "Data for message ACLs" "SECID198"
28826 .cindex "&ACL;" "data for message ACL"
28827 .vindex &$domain$&
28828 .vindex &$local_part$&
28829 .vindex &$sender_address$&
28830 .vindex &$sender_host_address$&
28831 .vindex &$smtp_command$&
28832 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
28833 that contain information about the host and the message's sender (for example,
28834 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
28835 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
28836 &$local_part$& are set from the argument address. The entire SMTP command
28837 is available in &$smtp_command$&.
28838
28839 When an ACL for the AUTH parameter of MAIL is running, the variables that
28840 contain information about the host are set, but &$sender_address$& is not yet
28841 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
28842 how it is used.
28843
28844 .vindex "&$message_size$&"
28845 The &$message_size$& variable is set to the value of the SIZE parameter on
28846 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
28847 that parameter is not given. The value is updated to the true message size by
28848 the time the final DATA ACL is run (after the message data has been
28849 received).
28850
28851 .vindex "&$rcpt_count$&"
28852 .vindex "&$recipients_count$&"
28853 The &$rcpt_count$& variable increases by one for each RCPT command received.
28854 The &$recipients_count$& variable increases by one each time a RCPT command is
28855 accepted, so while an ACL for RCPT is being processed, it contains the number
28856 of previously accepted recipients. At DATA time (for both the DATA ACLs),
28857 &$rcpt_count$& contains the total number of RCPT commands, and
28858 &$recipients_count$& contains the total number of accepted recipients.
28859
28860
28861
28862
28863
28864 .section "Data for non-message ACLs" "SECTdatfornon"
28865 .cindex "&ACL;" "data for non-message ACL"
28866 .vindex &$smtp_command_argument$&
28867 .vindex &$smtp_command$&
28868 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
28869 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
28870 and the entire SMTP command is available in &$smtp_command$&.
28871 These variables can be tested using a &%condition%& condition. For example,
28872 here is an ACL for use with AUTH, which insists that either the session is
28873 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
28874 does not permit authentication methods that use cleartext passwords on
28875 unencrypted connections.
28876 .code
28877 acl_check_auth:
28878 accept encrypted = *
28879 accept condition = ${if eq{${uc:$smtp_command_argument}}\
28880 {CRAM-MD5}}
28881 deny message = TLS encryption or CRAM-MD5 required
28882 .endd
28883 (Another way of applying this restriction is to arrange for the authenticators
28884 that use cleartext passwords not to be advertised when the connection is not
28885 encrypted. You can use the generic &%server_advertise_condition%& authenticator
28886 option to do this.)
28887
28888
28889
28890 .section "Format of an ACL" "SECID199"
28891 .cindex "&ACL;" "format of"
28892 .cindex "&ACL;" "verbs, definition of"
28893 An individual ACL consists of a number of statements. Each statement starts
28894 with a verb, optionally followed by a number of conditions and &"modifiers"&.
28895 Modifiers can change the way the verb operates, define error and log messages,
28896 set variables, insert delays, and vary the processing of accepted messages.
28897
28898 If all the conditions are met, the verb is obeyed. The same condition may be
28899 used (with different arguments) more than once in the same statement. This
28900 provides a means of specifying an &"and"& conjunction between conditions. For
28901 example:
28902 .code
28903 deny dnslists = list1.example
28904 dnslists = list2.example
28905 .endd
28906 If there are no conditions, the verb is always obeyed. Exim stops evaluating
28907 the conditions and modifiers when it reaches a condition that fails. What
28908 happens then depends on the verb (and in one case, on a special modifier). Not
28909 all the conditions make sense at every testing point. For example, you cannot
28910 test a sender address in the ACL that is run for a VRFY command.
28911
28912
28913 .section "ACL verbs" "SECID200"
28914 The ACL verbs are as follows:
28915
28916 .ilist
28917 .cindex "&%accept%& ACL verb"
28918 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
28919 of the conditions are not met, what happens depends on whether &%endpass%&
28920 appears among the conditions (for syntax see below). If the failing condition
28921 is before &%endpass%&, control is passed to the next ACL statement; if it is
28922 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
28923 check a RCPT command:
28924 .code
28925 accept domains = +local_domains
28926 endpass
28927 verify = recipient
28928 .endd
28929 If the recipient domain does not match the &%domains%& condition, control
28930 passes to the next statement. If it does match, the recipient is verified, and
28931 the command is accepted if verification succeeds. However, if verification
28932 fails, the ACL yields &"deny"&, because the failing condition is after
28933 &%endpass%&.
28934
28935 The &%endpass%& feature has turned out to be confusing to many people, so its
28936 use is not recommended nowadays. It is always possible to rewrite an ACL so
28937 that &%endpass%& is not needed, and it is no longer used in the default
28938 configuration.
28939
28940 .cindex "&%message%& ACL modifier" "with &%accept%&"
28941 If a &%message%& modifier appears on an &%accept%& statement, its action
28942 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
28943 (when an &%accept%& verb either accepts or passes control to the next
28944 statement), &%message%& can be used to vary the message that is sent when an
28945 SMTP command is accepted. For example, in a RCPT ACL you could have:
28946 .display
28947 &`accept `&<&'some conditions'&>
28948 &` message = OK, I will allow you through today`&
28949 .endd
28950 You can specify an SMTP response code, optionally followed by an &"extended
28951 response code"& at the start of the message, but the first digit must be the
28952 same as would be sent by default, which is 2 for an &%accept%& verb.
28953
28954 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
28955 an error message that is used when access is denied. This behaviour is retained
28956 for backward compatibility, but current &"best practice"& is to avoid the use
28957 of &%endpass%&.
28958
28959
28960 .next
28961 .cindex "&%defer%& ACL verb"
28962 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
28963 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
28964 &%defer%& is the same as &%deny%&, because there is no way of sending a
28965 temporary error. For a RCPT command, &%defer%& is much the same as using a
28966 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
28967 be used in any ACL, and even for a recipient it might be a simpler approach.
28968
28969
28970 .next
28971 .cindex "&%deny%& ACL verb"
28972 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
28973 the conditions are not met, control is passed to the next ACL statement. For
28974 example,
28975 .code
28976 deny dnslists = blackholes.mail-abuse.org
28977 .endd
28978 rejects commands from hosts that are on a DNS black list.
28979
28980
28981 .next
28982 .cindex "&%discard%& ACL verb"
28983 &%discard%&: This verb behaves like &%accept%&, except that it returns
28984 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
28985 that are concerned with receiving messages. When all the conditions are true,
28986 the sending entity receives a &"success"& response. However, &%discard%& causes
28987 recipients to be discarded. If it is used in an ACL for RCPT, just the one
28988 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
28989 message's recipients are discarded. Recipients that are discarded before DATA
28990 do not appear in the log line when the &%received_recipients%& log selector is set.
28991
28992 If the &%log_message%& modifier is set when &%discard%& operates,
28993 its contents are added to the line that is automatically written to the log.
28994 The &%message%& modifier operates exactly as it does for &%accept%&.
28995
28996
28997 .next
28998 .cindex "&%drop%& ACL verb"
28999 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
29000 forcibly closed after the 5&'xx'& error message has been sent. For example:
29001 .code
29002 drop message = I don't take more than 20 RCPTs
29003 condition = ${if > {$rcpt_count}{20}}
29004 .endd
29005 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
29006 The connection is always dropped after sending a 550 response.
29007
29008 .next
29009 .cindex "&%require%& ACL verb"
29010 &%require%&: If all the conditions are met, control is passed to the next ACL
29011 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
29012 example, when checking a RCPT command,
29013 .code
29014 require message = Sender did not verify
29015 verify = sender
29016 .endd
29017 passes control to subsequent statements only if the message's sender can be
29018 verified. Otherwise, it rejects the command. Note the positioning of the
29019 &%message%& modifier, before the &%verify%& condition. The reason for this is
29020 discussed in section &<<SECTcondmodproc>>&.
29021
29022 .next
29023 .cindex "&%warn%& ACL verb"
29024 &%warn%&: If all the conditions are true, a line specified by the
29025 &%log_message%& modifier is written to Exim's main log. Control always passes
29026 to the next ACL statement. If any condition is false, the log line is not
29027 written. If an identical log line is requested several times in the same
29028 message, only one copy is actually written to the log. If you want to force
29029 duplicates to be written, use the &%logwrite%& modifier instead.
29030
29031 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
29032 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
29033 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
29034 first failing condition. There is more about adding header lines in section
29035 &<<SECTaddheadacl>>&.
29036
29037 If any condition on a &%warn%& statement cannot be completed (that is, there is
29038 some sort of defer), the log line specified by &%log_message%& is not written.
29039 This does not include the case of a forced failure from a lookup, which
29040 is considered to be a successful completion. After a defer, no further
29041 conditions or modifiers in the &%warn%& statement are processed. The incident
29042 is logged, and the ACL continues to be processed, from the next statement
29043 onwards.
29044
29045
29046 .vindex "&$acl_verify_message$&"
29047 When one of the &%warn%& conditions is an address verification that fails, the
29048 text of the verification failure message is in &$acl_verify_message$&. If you
29049 want this logged, you must set it up explicitly. For example:
29050 .code
29051 warn !verify = sender
29052 log_message = sender verify failed: $acl_verify_message
29053 .endd
29054 .endlist
29055
29056 At the end of each ACL there is an implicit unconditional &%deny%&.
29057
29058 As you can see from the examples above, the conditions and modifiers are
29059 written one to a line, with the first one on the same line as the verb, and
29060 subsequent ones on following lines. If you have a very long condition, you can
29061 continue it onto several physical lines by the usual backslash continuation
29062 mechanism. It is conventional to align the conditions vertically.
29063
29064
29065
29066 .section "ACL variables" "SECTaclvariables"
29067 .cindex "&ACL;" "variables"
29068 There are some special variables that can be set during ACL processing. They
29069 can be used to pass information between different ACLs, different invocations
29070 of the same ACL in the same SMTP connection, and between ACLs and the routers,
29071 transports, and filters that are used to deliver a message. The names of these
29072 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
29073 an underscore, but the remainder of the name can be any sequence of
29074 alphanumeric characters and underscores that you choose. There is no limit on
29075 the number of ACL variables. The two sets act as follows:
29076 .ilist
29077 The values of those variables whose names begin with &$acl_c$& persist
29078 throughout an SMTP connection. They are never reset. Thus, a value that is set
29079 while receiving one message is still available when receiving the next message
29080 on the same SMTP connection.
29081 .next
29082 The values of those variables whose names begin with &$acl_m$& persist only
29083 while a message is being received. They are reset afterwards. They are also
29084 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
29085 .endlist
29086
29087 When a message is accepted, the current values of all the ACL variables are
29088 preserved with the message and are subsequently made available at delivery
29089 time. The ACL variables are set by a modifier called &%set%&. For example:
29090 .code
29091 accept hosts = whatever
29092 set acl_m4 = some value
29093 accept authenticated = *
29094 set acl_c_auth = yes
29095 .endd
29096 &*Note*&: A leading dollar sign is not used when naming a variable that is to
29097 be set. If you want to set a variable without taking any action, you can use a
29098 &%warn%& verb without any other modifiers or conditions.
29099
29100 .oindex &%strict_acl_vars%&
29101 What happens if a syntactically valid but undefined ACL variable is
29102 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
29103 false (the default), an empty string is substituted; if it is true, an
29104 error is generated.
29105
29106 Versions of Exim before 4.64 have a limited set of numbered variables, but
29107 their names are compatible, so there is no problem with upgrading.
29108
29109
29110 .section "Condition and modifier processing" "SECTcondmodproc"
29111 .cindex "&ACL;" "conditions; processing"
29112 .cindex "&ACL;" "modifiers; processing"
29113 An exclamation mark preceding a condition negates its result. For example:
29114 .code
29115 deny domains = *.dom.example
29116 !verify = recipient
29117 .endd
29118 causes the ACL to return &"deny"& if the recipient domain ends in
29119 &'dom.example'& and the recipient address cannot be verified. Sometimes
29120 negation can be used on the right-hand side of a condition. For example, these
29121 two statements are equivalent:
29122 .code
29123 deny hosts = !192.168.3.4
29124 deny !hosts = 192.168.3.4
29125 .endd
29126 However, for many conditions (&%verify%& being a good example), only left-hand
29127 side negation of the whole condition is possible.
29128
29129 The arguments of conditions and modifiers are expanded. A forced failure
29130 of an expansion causes a condition to be ignored, that is, it behaves as if the
29131 condition is true. Consider these two statements:
29132 .code
29133 accept senders = ${lookup{$host_name}lsearch\
29134 {/some/file}{$value}fail}
29135 accept senders = ${lookup{$host_name}lsearch\
29136 {/some/file}{$value}{}}
29137 .endd
29138 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
29139 the returned list is searched, but if the lookup fails the behaviour is
29140 different in the two cases. The &%fail%& in the first statement causes the
29141 condition to be ignored, leaving no further conditions. The &%accept%& verb
29142 therefore succeeds. The second statement, however, generates an empty list when
29143 the lookup fails. No sender can match an empty list, so the condition fails,
29144 and therefore the &%accept%& also fails.
29145
29146 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
29147 specify actions that are taken as the conditions for a statement are checked;
29148 others specify text for messages that are used when access is denied or a
29149 warning is generated. The &%control%& modifier affects the way an incoming
29150 message is handled.
29151
29152 The positioning of the modifiers in an ACL statement is important, because the
29153 processing of a verb ceases as soon as its outcome is known. Only those
29154 modifiers that have already been encountered will take effect. For example,
29155 consider this use of the &%message%& modifier:
29156 .code
29157 require message = Can't verify sender
29158 verify = sender
29159 message = Can't verify recipient
29160 verify = recipient
29161 message = This message cannot be used
29162 .endd
29163 If sender verification fails, Exim knows that the result of the statement is
29164 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
29165 so its text is used as the error message. If sender verification succeeds, but
29166 recipient verification fails, the second message is used. If recipient
29167 verification succeeds, the third message becomes &"current"&, but is never used
29168 because there are no more conditions to cause failure.
29169
29170 For the &%deny%& verb, on the other hand, it is always the last &%message%&
29171 modifier that is used, because all the conditions must be true for rejection to
29172 happen. Specifying more than one &%message%& modifier does not make sense, and
29173 the message can even be specified after all the conditions. For example:
29174 .code
29175 deny hosts = ...
29176 !senders = *@my.domain.example
29177 message = Invalid sender from client host
29178 .endd
29179 The &"deny"& result does not happen until the end of the statement is reached,
29180 by which time Exim has set up the message.
29181
29182
29183
29184 .section "ACL modifiers" "SECTACLmodi"
29185 .cindex "&ACL;" "modifiers; list of"
29186 The ACL modifiers are as follows:
29187
29188 .vlist
29189 .vitem &*add_header*&&~=&~<&'text'&>
29190 This modifier specifies one or more header lines that are to be added to an
29191 incoming message, assuming, of course, that the message is ultimately
29192 accepted. For details, see section &<<SECTaddheadacl>>&.
29193
29194 .vitem &*continue*&&~=&~<&'text'&>
29195 .cindex "&%continue%& ACL modifier"
29196 .cindex "database" "updating in ACL"
29197 This modifier does nothing of itself, and processing of the ACL always
29198 continues with the next condition or modifier. The value of &%continue%& is in
29199 the side effects of expanding its argument. Typically this could be used to
29200 update a database. It is really just a syntactic tidiness, to avoid having to
29201 write rather ugly lines like this:
29202 .display
29203 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
29204 .endd
29205 Instead, all you need is
29206 .display
29207 &`continue = `&<&'some expansion'&>
29208 .endd
29209
29210 .vitem &*control*&&~=&~<&'text'&>
29211 .cindex "&%control%& ACL modifier"
29212 This modifier affects the subsequent processing of the SMTP connection or of an
29213 incoming message that is accepted. The effect of the first type of control
29214 lasts for the duration of the connection, whereas the effect of the second type
29215 lasts only until the current message has been received. The message-specific
29216 controls always apply to the whole message, not to individual recipients,
29217 even if the &%control%& modifier appears in a RCPT ACL.
29218
29219 As there are now quite a few controls that can be applied, they are described
29220 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
29221 in several different ways. For example:
29222
29223 . ==== As this is a nested list, any displays it contains must be indented
29224 . ==== as otherwise they are too far to the left. That comment applies only
29225 . ==== when xmlto and fop are used; formatting with sdop gets it right either
29226 . ==== way.
29227
29228 .ilist
29229 It can be at the end of an &%accept%& statement:
29230 .code
29231 accept ...some conditions
29232 control = queue_only
29233 .endd
29234 In this case, the control is applied when this statement yields &"accept"&, in
29235 other words, when the conditions are all true.
29236
29237 .next
29238 It can be in the middle of an &%accept%& statement:
29239 .code
29240 accept ...some conditions...
29241 control = queue_only
29242 ...some more conditions...
29243 .endd
29244 If the first set of conditions are true, the control is applied, even if the
29245 statement does not accept because one of the second set of conditions is false.
29246 In this case, some subsequent statement must yield &"accept"& for the control
29247 to be relevant.
29248
29249 .next
29250 It can be used with &%warn%& to apply the control, leaving the
29251 decision about accepting or denying to a subsequent verb. For
29252 example:
29253 .code
29254 warn ...some conditions...
29255 control = freeze
29256 accept ...
29257 .endd
29258 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
29259 &%logwrite%&, so it does not add anything to the message and does not write a
29260 log entry.
29261
29262 .next
29263 If you want to apply a control unconditionally, you can use it with a
29264 &%require%& verb. For example:
29265 .code
29266 require control = no_multiline_responses
29267 .endd
29268 .endlist
29269
29270 .vitem &*delay*&&~=&~<&'time'&>
29271 .cindex "&%delay%& ACL modifier"
29272 .oindex "&%-bh%&"
29273 This modifier may appear in any ACL except notquit. It causes Exim to wait for
29274 the time interval before proceeding. However, when testing Exim using the
29275 &%-bh%& option, the delay is not actually imposed (an appropriate message is
29276 output instead). The time is given in the usual Exim notation, and the delay
29277 happens as soon as the modifier is processed. In an SMTP session, pending
29278 output is flushed before the delay is imposed.
29279
29280 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
29281 example:
29282 .code
29283 deny ...some conditions...
29284 delay = 30s
29285 .endd
29286 The delay happens if all the conditions are true, before the statement returns
29287 &"deny"&. Compare this with:
29288 .code
29289 deny delay = 30s
29290 ...some conditions...
29291 .endd
29292 which waits for 30s before processing the conditions. The &%delay%& modifier
29293 can also be used with &%warn%& and together with &%control%&:
29294 .code
29295 warn ...some conditions...
29296 delay = 2m
29297 control = freeze
29298 accept ...
29299 .endd
29300
29301 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
29302 responses to several commands are no longer buffered and sent in one packet (as
29303 they would normally be) because all output is flushed before imposing the
29304 delay. This optimization is disabled so that a number of small delays do not
29305 appear to the client as one large aggregated delay that might provoke an
29306 unwanted timeout. You can, however, disable output flushing for &%delay%& by
29307 using a &%control%& modifier to set &%no_delay_flush%&.
29308
29309
29310 .vitem &*endpass*&
29311 .cindex "&%endpass%& ACL modifier"
29312 This modifier, which has no argument, is recognized only in &%accept%& and
29313 &%discard%& statements. It marks the boundary between the conditions whose
29314 failure causes control to pass to the next statement, and the conditions whose
29315 failure causes the ACL to return &"deny"&. This concept has proved to be
29316 confusing to some people, so the use of &%endpass%& is no longer recommended as
29317 &"best practice"&. See the description of &%accept%& above for more details.
29318
29319
29320 .vitem &*log_message*&&~=&~<&'text'&>
29321 .cindex "&%log_message%& ACL modifier"
29322 This modifier sets up a message that is used as part of the log message if the
29323 ACL denies access or a &%warn%& statement's conditions are true. For example:
29324 .code
29325 require log_message = wrong cipher suite $tls_in_cipher
29326 encrypted = DES-CBC3-SHA
29327 .endd
29328 &%log_message%& is also used when recipients are discarded by &%discard%&. For
29329 example:
29330 .display
29331 &`discard `&<&'some conditions'&>
29332 &` log_message = Discarded $local_part@$domain because...`&
29333 .endd
29334 When access is denied, &%log_message%& adds to any underlying error message
29335 that may exist because of a condition failure. For example, while verifying a
29336 recipient address, a &':fail:'& redirection might have already set up a
29337 message.
29338
29339 The message may be defined before the conditions to which it applies, because
29340 the string expansion does not happen until Exim decides that access is to be
29341 denied. This means that any variables that are set by the condition are
29342 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
29343 variables are set after a DNS black list lookup succeeds. If the expansion of
29344 &%log_message%& fails, or if the result is an empty string, the modifier is
29345 ignored.
29346
29347 .vindex "&$acl_verify_message$&"
29348 If you want to use a &%warn%& statement to log the result of an address
29349 verification, you can use &$acl_verify_message$& to include the verification
29350 error message.
29351
29352 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
29353 the start of the logged message. If the same warning log message is requested
29354 more than once while receiving a single email message, only one copy is
29355 actually logged. If you want to log multiple copies, use &%logwrite%& instead
29356 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
29357 is logged for a successful &%warn%& statement.
29358
29359 If &%log_message%& is not present and there is no underlying error message (for
29360 example, from the failure of address verification), but &%message%& is present,
29361 the &%message%& text is used for logging rejections. However, if any text for
29362 logging contains newlines, only the first line is logged. In the absence of
29363 both &%log_message%& and &%message%&, a default built-in message is used for
29364 logging rejections.
29365
29366
29367 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
29368 .cindex "&%log_reject_target%& ACL modifier"
29369 .cindex "logging in ACL" "specifying which log"
29370 This modifier makes it possible to specify which logs are used for messages
29371 about ACL rejections. Its argument is a colon-separated list of words that can
29372 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
29373 may be empty, in which case a rejection is not logged at all. For example, this
29374 ACL fragment writes no logging information when access is denied:
29375 .display
29376 &`deny `&<&'some conditions'&>
29377 &` log_reject_target =`&
29378 .endd
29379 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
29380 permanent and temporary rejections. Its effect lasts for the rest of the
29381 current ACL.
29382
29383
29384 .vitem &*logwrite*&&~=&~<&'text'&>
29385 .cindex "&%logwrite%& ACL modifier"
29386 .cindex "logging in ACL" "immediate"
29387 This modifier writes a message to a log file as soon as it is encountered when
29388 processing an ACL. (Compare &%log_message%&, which, except in the case of
29389 &%warn%& and &%discard%&, is used only if the ACL statement denies
29390 access.) The &%logwrite%& modifier can be used to log special incidents in
29391 ACLs. For example:
29392 .display
29393 &`accept `&<&'some special conditions'&>
29394 &` control = freeze`&
29395 &` logwrite = froze message because ...`&
29396 .endd
29397 By default, the message is written to the main log. However, it may begin
29398 with a colon, followed by a comma-separated list of log names, and then
29399 another colon, to specify exactly which logs are to be written. For
29400 example:
29401 .code
29402 logwrite = :main,reject: text for main and reject logs
29403 logwrite = :panic: text for panic log only
29404 .endd
29405
29406
29407 .vitem &*message*&&~=&~<&'text'&>
29408 .cindex "&%message%& ACL modifier"
29409 This modifier sets up a text string that is expanded and used as a response
29410 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
29411 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
29412 there is some complication if &%endpass%& is involved; see the description of
29413 &%accept%& for details.)
29414
29415 The expansion of the message happens at the time Exim decides that the ACL is
29416 to end, not at the time it processes &%message%&. If the expansion fails, or
29417 generates an empty string, the modifier is ignored. Here is an example where
29418 &%message%& must be specified first, because the ACL ends with a rejection if
29419 the &%hosts%& condition fails:
29420 .code
29421 require message = Host not recognized
29422 hosts = 10.0.0.0/8
29423 .endd
29424 (Once a condition has failed, no further conditions or modifiers are
29425 processed.)
29426
29427 .cindex "SMTP" "error codes"
29428 .oindex "&%smtp_banner%&
29429 For ACLs that are triggered by SMTP commands, the message is returned as part
29430 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
29431 is meaningful only for SMTP, as no message is returned when a non-SMTP message
29432 is accepted. In the case of the connect ACL, accepting with a message modifier
29433 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
29434 accept message may not contain more than one line (otherwise it will be
29435 truncated at the first newline and a panic logged), and it cannot affect the
29436 EHLO options.
29437
29438 When SMTP is involved, the message may begin with an overriding response code,
29439 consisting of three digits optionally followed by an &"extended response code"&
29440 of the form &'n.n.n'&, each code being followed by a space. For example:
29441 .code
29442 deny message = 599 1.2.3 Host not welcome
29443 hosts = 192.168.34.0/24
29444 .endd
29445 The first digit of the supplied response code must be the same as would be sent
29446 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
29447 access, but for the predata ACL, note that the default success code is 354, not
29448 2&'xx'&.
29449
29450 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
29451 the message modifier cannot override the 221 response code.
29452
29453 The text in a &%message%& modifier is literal; any quotes are taken as
29454 literals, but because the string is expanded, backslash escapes are processed
29455 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
29456 response.
29457
29458 .vindex "&$acl_verify_message$&"
29459 For ACLs that are called by an &%acl =%& ACL condition, the message is
29460 stored in &$acl_verify_message$&, from which the calling ACL may use it.
29461
29462 If &%message%& is used on a statement that verifies an address, the message
29463 specified overrides any message that is generated by the verification process.
29464 However, the original message is available in the variable
29465 &$acl_verify_message$&, so you can incorporate it into your message if you
29466 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
29467 routers to be passed back as part of the SMTP response, you should either not
29468 use a &%message%& modifier, or make use of &$acl_verify_message$&.
29469
29470 For compatibility with previous releases of Exim, a &%message%& modifier that
29471 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
29472 modifier, but this usage is now deprecated. However, &%message%& acts only when
29473 all the conditions are true, wherever it appears in an ACL command, whereas
29474 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
29475 &%warn%& in an ACL that is not concerned with receiving a message, it has no
29476 effect.
29477
29478
29479 .vitem &*queue*&&~=&~<&'text'&>
29480 .cindex "&%queue%& ACL modifier"
29481 .cindex "named queues" "selecting in ACL"
29482 This modifier specifies the use of a named queue for spool files
29483 for the message.
29484 It can only be used before the message is received (i.e. not in
29485 the DATA ACL).
29486 This could be used, for example, for known high-volume burst sources
29487 of traffic, or for quarantine of messages.
29488 Separate queue-runner processes will be needed for named queues.
29489 If the text after expansion is empty, the default queue is used.
29490
29491
29492 .vitem &*remove_header*&&~=&~<&'text'&>
29493 This modifier specifies one or more header names in a colon-separated list
29494 that are to be removed from an incoming message, assuming, of course, that
29495 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
29496
29497
29498 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
29499 .cindex "&%set%& ACL modifier"
29500 This modifier puts a value into one of the ACL variables (see section
29501 &<<SECTaclvariables>>&).
29502
29503
29504 .vitem &*udpsend*&&~=&~<&'parameters'&>
29505 .cindex "UDP communications"
29506 This modifier sends a UDP packet, for purposes such as statistics
29507 collection or behaviour monitoring. The parameters are expanded, and
29508 the result of the expansion must be a colon-separated list consisting
29509 of a destination server, port number, and the packet contents. The
29510 server can be specified as a host name or IPv4 or IPv6 address. The
29511 separator can be changed with the usual angle bracket syntax. For
29512 example, you might want to collect information on which hosts connect
29513 when:
29514 .code
29515 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
29516 $tod_zulu $sender_host_address
29517 .endd
29518 .endlist
29519
29520
29521
29522
29523 .section "Use of the control modifier" "SECTcontrols"
29524 .cindex "&%control%& ACL modifier"
29525 The &%control%& modifier supports the following settings:
29526
29527 .vlist
29528 .vitem &*control&~=&~allow_auth_unadvertised*&
29529 This modifier allows a client host to use the SMTP AUTH command even when it
29530 has not been advertised in response to EHLO. Furthermore, because there are
29531 apparently some really broken clients that do this, Exim will accept AUTH after
29532 HELO (rather than EHLO) when this control is set. It should be used only if you
29533 really need it, and you should limit its use to those broken clients that do
29534 not work without it. For example:
29535 .code
29536 warn hosts = 192.168.34.25
29537 control = allow_auth_unadvertised
29538 .endd
29539 Normally, when an Exim server receives an AUTH command, it checks the name of
29540 the authentication mechanism that is given in the command to ensure that it
29541 matches an advertised mechanism. When this control is set, the check that a
29542 mechanism has been advertised is bypassed. Any configured mechanism can be used
29543 by the client. This control is permitted only in the connection and HELO ACLs.
29544
29545
29546 .vitem &*control&~=&~caseful_local_part*& &&&
29547 &*control&~=&~caselower_local_part*&
29548 .cindex "&ACL;" "case of local part in"
29549 .cindex "case of local parts"
29550 .vindex "&$local_part$&"
29551 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
29552 (that is, during RCPT processing). By default, the contents of &$local_part$&
29553 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
29554 any uppercase letters in the original local part are restored in &$local_part$&
29555 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
29556 is encountered.
29557
29558 These controls affect only the current recipient. Moreover, they apply only to
29559 local part handling that takes place directly in the ACL (for example, as a key
29560 in lookups). If a test to verify the recipient is obeyed, the case-related
29561 handling of the local part during the verification is controlled by the router
29562 configuration (see the &%caseful_local_part%& generic router option).
29563
29564 This facility could be used, for example, to add a spam score to local parts
29565 containing upper case letters. For example, using &$acl_m4$& to accumulate the
29566 spam score:
29567 .code
29568 warn control = caseful_local_part
29569 set acl_m4 = ${eval:\
29570 $acl_m4 + \
29571 ${if match{$local_part}{[A-Z]}{1}{0}}\
29572 }
29573 control = caselower_local_part
29574 .endd
29575 Notice that we put back the lower cased version afterwards, assuming that
29576 is what is wanted for subsequent tests.
29577
29578
29579 .vitem &*control&~=&~cutthrough_delivery/*&<&'options'&>
29580 .cindex "&ACL;" "cutthrough routing"
29581 .cindex "cutthrough" "requesting"
29582 This option requests delivery be attempted while the item is being received.
29583
29584 The option is usable in the RCPT ACL.
29585 If enabled for a message received via smtp and routed to an smtp transport,
29586 and only one transport, interface, destination host and port combination
29587 is used for all recipients of the message,
29588 then the delivery connection is made while the receiving connection is open
29589 and data is copied from one to the other.
29590
29591 An attempt to set this option for any recipient but the first
29592 for a mail will be quietly ignored.
29593 If a recipient-verify callout
29594 (with use_sender)
29595 connection is subsequently
29596 requested in the same ACL it is held open and used for
29597 any subsequent recipients and the data,
29598 otherwise one is made after the initial RCPT ACL completes.
29599
29600 Note that routers are used in verify mode,
29601 and cannot depend on content of received headers.
29602 Note also that headers cannot be
29603 modified by any of the post-data ACLs (DATA, MIME and DKIM).
29604 Headers may be modified by routers (subject to the above) and transports.
29605 The &'Received-By:'& header is generated as soon as the body reception starts,
29606 rather than the traditional time after the full message is received;
29607 this will affect the timestamp.
29608
29609 All the usual ACLs are called; if one results in the message being
29610 rejected, all effort spent in delivery (including the costs on
29611 the ultimate destination) will be wasted.
29612 Note that in the case of data-time ACLs this includes the entire
29613 message body.
29614
29615 Cutthrough delivery is not supported via transport-filters or when DKIM signing
29616 of outgoing messages is done, because it sends data to the ultimate destination
29617 before the entire message has been received from the source.
29618 It is not supported for messages received with the SMTP PRDR
29619 or CHUNKING
29620 options in use.
29621
29622 Should the ultimate destination system positively accept or reject the mail,
29623 a corresponding indication is given to the source system and nothing is queued.
29624 If the item is successfully delivered in cutthrough mode
29625 the delivery log lines are tagged with ">>" rather than "=>" and appear
29626 before the acceptance "<=" line.
29627
29628 If there is a temporary error the item is queued for later delivery in the
29629 usual fashion.
29630 This behaviour can be adjusted by appending the option &*defer=*&<&'value'&>
29631 to the control; the default value is &"spool"& and the alternate value
29632 &"pass"& copies an SMTP defer response from the target back to the initiator
29633 and does not queue the message.
29634 Note that this is independent of any recipient verify conditions in the ACL.
29635
29636 Delivery in this mode avoids the generation of a bounce mail to a
29637 (possibly faked)
29638 sender when the destination system is doing content-scan based rejection.
29639
29640
29641 .vitem &*control&~=&~debug/*&<&'options'&>
29642 .cindex "&ACL;" "enabling debug logging"
29643 .cindex "debugging" "enabling from an ACL"
29644 This control turns on debug logging, almost as though Exim had been invoked
29645 with &`-d`&, with the output going to a new logfile in the usual logs directory,
29646 by default called &'debuglog'&.
29647 The filename can be adjusted with the &'tag'& option, which
29648 may access any variables already defined. The logging may be adjusted with
29649 the &'opts'& option, which takes the same values as the &`-d`& command-line
29650 option.
29651 Logging started this way may be stopped, and the file removed,
29652 with the &'kill'& option.
29653 Some examples (which depend on variables that don't exist in all
29654 contexts):
29655 .code
29656 control = debug
29657 control = debug/tag=.$sender_host_address
29658 control = debug/opts=+expand+acl
29659 control = debug/tag=.$message_exim_id/opts=+expand
29660 control = debug/kill
29661 .endd
29662
29663
29664 .vitem &*control&~=&~dkim_disable_verify*&
29665 .cindex "disable DKIM verify"
29666 .cindex "DKIM" "disable verify"
29667 This control turns off DKIM verification processing entirely. For details on
29668 the operation and configuration of DKIM, see section &<<SECDKIM>>&.
29669
29670
29671 .vitem &*control&~=&~dscp/*&<&'value'&>
29672 .cindex "&ACL;" "setting DSCP value"
29673 .cindex "DSCP" "inbound"
29674 This option causes the DSCP value associated with the socket for the inbound
29675 connection to be adjusted to a given value, given as one of a number of fixed
29676 strings or to numeric value.
29677 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
29678 Common values include &`throughput`&, &`mincost`&, and on newer systems
29679 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
29680
29681 The outbound packets from Exim will be marked with this value in the header
29682 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
29683 that these values will have any effect, not be stripped by networking
29684 equipment, or do much of anything without cooperation with your Network
29685 Engineer and those of all network operators between the source and destination.
29686
29687
29688 .vitem &*control&~=&~enforce_sync*& &&&
29689 &*control&~=&~no_enforce_sync*&
29690 .cindex "SMTP" "synchronization checking"
29691 .cindex "synchronization checking in SMTP"
29692 These controls make it possible to be selective about when SMTP synchronization
29693 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
29694 state of the switch (it is true by default). See the description of this option
29695 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
29696
29697 The effect of these two controls lasts for the remainder of the SMTP
29698 connection. They can appear in any ACL except the one for the non-SMTP
29699 messages. The most straightforward place to put them is in the ACL defined by
29700 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
29701 before the first synchronization check. The expected use is to turn off the
29702 synchronization checks for badly-behaved hosts that you nevertheless need to
29703 work with.
29704
29705
29706 .vitem &*control&~=&~fakedefer/*&<&'message'&>
29707 .cindex "fake defer"
29708 .cindex "defer, fake"
29709 This control works in exactly the same way as &%fakereject%& (described below)
29710 except that it causes an SMTP 450 response after the message data instead of a
29711 550 response. You must take care when using &%fakedefer%& because it causes the
29712 messages to be duplicated when the sender retries. Therefore, you should not
29713 use &%fakedefer%& if the message is to be delivered normally.
29714
29715 .vitem &*control&~=&~fakereject/*&<&'message'&>
29716 .cindex "fake rejection"
29717 .cindex "rejection, fake"
29718 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
29719 words, only when an SMTP message is being received. If Exim accepts the
29720 message, instead the final 250 response, a 550 rejection message is sent.
29721 However, Exim proceeds to deliver the message as normal. The control applies
29722 only to the current message, not to any subsequent ones that may be received in
29723 the same SMTP connection.
29724
29725 The text for the 550 response is taken from the &%control%& modifier. If no
29726 message is supplied, the following is used:
29727 .code
29728 550-Your message has been rejected but is being
29729 550-kept for evaluation.
29730 550-If it was a legitimate message, it may still be
29731 550 delivered to the target recipient(s).
29732 .endd
29733 This facility should be used with extreme caution.
29734
29735 .vitem &*control&~=&~freeze*&
29736 .cindex "frozen messages" "forcing in ACL"
29737 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
29738 other words, only when a message is being received. If the message is accepted,
29739 it is placed on Exim's queue and frozen. The control applies only to the
29740 current message, not to any subsequent ones that may be received in the same
29741 SMTP connection.
29742
29743 This modifier can optionally be followed by &`/no_tell`&. If the global option
29744 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
29745 is told about the freezing), provided all the &*control=freeze*& modifiers that
29746 are obeyed for the current message have the &`/no_tell`& option.
29747
29748 .vitem &*control&~=&~no_delay_flush*&
29749 .cindex "SMTP" "output flushing, disabling for delay"
29750 Exim normally flushes SMTP output before implementing a delay in an ACL, to
29751 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
29752 use. This control, as long as it is encountered before the &%delay%& modifier,
29753 disables such output flushing.
29754
29755 .vitem &*control&~=&~no_callout_flush*&
29756 .cindex "SMTP" "output flushing, disabling for callout"
29757 Exim normally flushes SMTP output before performing a callout in an ACL, to
29758 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
29759 use. This control, as long as it is encountered before the &%verify%& condition
29760 that causes the callout, disables such output flushing.
29761
29762 .vitem &*control&~=&~no_mbox_unspool*&
29763 This control is available when Exim is compiled with the content scanning
29764 extension. Content scanning may require a copy of the current message, or parts
29765 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
29766 or spam scanner. Normally, such copies are deleted when they are no longer
29767 needed. If this control is set, the copies are not deleted. The control applies
29768 only to the current message, not to any subsequent ones that may be received in
29769 the same SMTP connection. It is provided for debugging purposes and is unlikely
29770 to be useful in production.
29771
29772 .vitem &*control&~=&~no_multiline_responses*&
29773 .cindex "multiline responses, suppressing"
29774 This control is permitted for any ACL except the one for non-SMTP messages.
29775 It seems that there are broken clients in use that cannot handle multiline
29776 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
29777
29778 If this control is set, multiline SMTP responses from ACL rejections are
29779 suppressed. One way of doing this would have been to put out these responses as
29780 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
29781 (&"use multiline responses for more"& it says &-- ha!), and some of the
29782 responses might get close to that. So this facility, which is after all only a
29783 sop to broken clients, is implemented by doing two very easy things:
29784
29785 .ilist
29786 Extra information that is normally output as part of a rejection caused by
29787 sender verification failure is omitted. Only the final line (typically &"sender
29788 verification failed"&) is sent.
29789 .next
29790 If a &%message%& modifier supplies a multiline response, only the first
29791 line is output.
29792 .endlist
29793
29794 The setting of the switch can, of course, be made conditional on the
29795 calling host. Its effect lasts until the end of the SMTP connection.
29796
29797 .vitem &*control&~=&~no_pipelining*&
29798 .cindex "PIPELINING" "suppressing advertising"
29799 This control turns off the advertising of the PIPELINING extension to SMTP in
29800 the current session. To be useful, it must be obeyed before Exim sends its
29801 response to an EHLO command. Therefore, it should normally appear in an ACL
29802 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
29803 &%pipelining_advertise_hosts%&.
29804
29805 .vitem &*control&~=&~queue_only*&
29806 .oindex "&%queue_only%&"
29807 .cindex "queueing incoming messages"
29808 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
29809 other words, only when a message is being received. If the message is accepted,
29810 it is placed on Exim's queue and left there for delivery by a subsequent queue
29811 runner. No immediate delivery process is started. In other words, it has the
29812 effect as the &%queue_only%& global option. However, the control applies only
29813 to the current message, not to any subsequent ones that may be received in the
29814 same SMTP connection.
29815
29816 .vitem &*control&~=&~submission/*&<&'options'&>
29817 .cindex "message" "submission"
29818 .cindex "submission mode"
29819 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
29820 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
29821 the current message is a submission from a local MUA. In this case, Exim
29822 operates in &"submission mode"&, and applies certain fixups to the message if
29823 necessary. For example, it adds a &'Date:'& header line if one is not present.
29824 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
29825 late (the message has already been created).
29826
29827 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
29828 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
29829 submission mode; the available options for this control are described there.
29830 The control applies only to the current message, not to any subsequent ones
29831 that may be received in the same SMTP connection.
29832
29833 .vitem &*control&~=&~suppress_local_fixups*&
29834 .cindex "submission fixups, suppressing"
29835 This control applies to locally submitted (non TCP/IP) messages, and is the
29836 complement of &`control = submission`&. It disables the fixups that are
29837 normally applied to locally-submitted messages. Specifically:
29838
29839 .ilist
29840 Any &'Sender:'& header line is left alone (in this respect, it is a
29841 dynamic version of &%local_sender_retain%&).
29842 .next
29843 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
29844 .next
29845 There is no check that &'From:'& corresponds to the actual sender.
29846 .endlist ilist
29847
29848 This control may be useful when a remotely-originated message is accepted,
29849 passed to some scanning program, and then re-submitted for delivery. It can be
29850 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
29851 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
29852 data is read.
29853
29854 &*Note:*& This control applies only to the current message, not to any others
29855 that are being submitted at the same time using &%-bs%& or &%-bS%&.
29856
29857 .vitem &*control&~=&~utf8_downconvert*&
29858 This control enables conversion of UTF-8 in message addresses
29859 to a-label form.
29860 For details see section &<<SECTi18nMTA>>&.
29861 .endlist vlist
29862
29863
29864 .section "Summary of message fixup control" "SECTsummesfix"
29865 All four possibilities for message fixups can be specified:
29866
29867 .ilist
29868 Locally submitted, fixups applied: the default.
29869 .next
29870 Locally submitted, no fixups applied: use
29871 &`control = suppress_local_fixups`&.
29872 .next
29873 Remotely submitted, no fixups applied: the default.
29874 .next
29875 Remotely submitted, fixups applied: use &`control = submission`&.
29876 .endlist
29877
29878
29879
29880 .section "Adding header lines in ACLs" "SECTaddheadacl"
29881 .cindex "header lines" "adding in an ACL"
29882 .cindex "header lines" "position of added lines"
29883 .cindex "&%add_header%& ACL modifier"
29884 The &%add_header%& modifier can be used to add one or more extra header lines
29885 to an incoming message, as in this example:
29886 .code
29887 warn dnslists = sbl.spamhaus.org : \
29888 dialup.mail-abuse.org
29889 add_header = X-blacklisted-at: $dnslist_domain
29890 .endd
29891 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
29892 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
29893 receiving a message). The message must ultimately be accepted for
29894 &%add_header%& to have any significant effect. You can use &%add_header%& with
29895 any ACL verb, including &%deny%& (though this is potentially useful only in a
29896 RCPT ACL).
29897
29898 Headers will not be added to the message if the modifier is used in
29899 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
29900
29901 Leading and trailing newlines are removed from
29902 the data for the &%add_header%& modifier; if it then
29903 contains one or more newlines that
29904 are not followed by a space or a tab, it is assumed to contain multiple header
29905 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
29906 front of any line that is not a valid header line.
29907
29908 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
29909 They are added to the message before processing the DATA and MIME ACLs.
29910 However, if an identical header line is requested more than once, only one copy
29911 is actually added to the message. Further header lines may be accumulated
29912 during the DATA and MIME ACLs, after which they are added to the message, again
29913 with duplicates suppressed. Thus, it is possible to add two identical header
29914 lines to an SMTP message, but only if one is added before DATA and one after.
29915 In the case of non-SMTP messages, new headers are accumulated during the
29916 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
29917 message is rejected after DATA or by the non-SMTP ACL, all added header lines
29918 are included in the entry that is written to the reject log.
29919
29920 .cindex "header lines" "added; visibility of"
29921 Header lines are not visible in string expansions
29922 of message headers
29923 until they are added to the
29924 message. It follows that header lines defined in the MAIL, RCPT, and predata
29925 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
29926 header lines that are added by the DATA or MIME ACLs are not visible in those
29927 ACLs. Because of this restriction, you cannot use header lines as a way of
29928 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
29929 this, you can use ACL variables, as described in section
29930 &<<SECTaclvariables>>&.
29931
29932 The list of headers yet to be added is given by the &%$headers_added%& variable.
29933
29934 The &%add_header%& modifier acts immediately as it is encountered during the
29935 processing of an ACL. Notice the difference between these two cases:
29936 .display
29937 &`accept add_header = ADDED: some text`&
29938 &` `&<&'some condition'&>
29939
29940 &`accept `&<&'some condition'&>
29941 &` add_header = ADDED: some text`&
29942 .endd
29943 In the first case, the header line is always added, whether or not the
29944 condition is true. In the second case, the header line is added only if the
29945 condition is true. Multiple occurrences of &%add_header%& may occur in the same
29946 ACL statement. All those that are encountered before a condition fails are
29947 honoured.
29948
29949 .cindex "&%warn%& ACL verb"
29950 For compatibility with previous versions of Exim, a &%message%& modifier for a
29951 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
29952 effect only if all the conditions are true, even if it appears before some of
29953 them. Furthermore, only the last occurrence of &%message%& is honoured. This
29954 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
29955 are present on a &%warn%& verb, both are processed according to their
29956 specifications.
29957
29958 By default, new header lines are added to a message at the end of the existing
29959 header lines. However, you can specify that any particular header line should
29960 be added right at the start (before all the &'Received:'& lines), immediately
29961 after the first block of &'Received:'& lines, or immediately before any line
29962 that is not a &'Received:'& or &'Resent-something:'& header.
29963
29964 This is done by specifying &":at_start:"&, &":after_received:"&, or
29965 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
29966 header line, respectively. (Header text cannot start with a colon, as there has
29967 to be a header name first.) For example:
29968 .code
29969 warn add_header = \
29970 :after_received:X-My-Header: something or other...
29971 .endd
29972 If more than one header line is supplied in a single &%add_header%& modifier,
29973 each one is treated independently and can therefore be placed differently. If
29974 you add more than one line at the start, or after the Received: block, they end
29975 up in reverse order.
29976
29977 &*Warning*&: This facility currently applies only to header lines that are
29978 added in an ACL. It does NOT work for header lines that are added in a
29979 system filter or in a router or transport.
29980
29981
29982
29983 .section "Removing header lines in ACLs" "SECTremoveheadacl"
29984 .cindex "header lines" "removing in an ACL"
29985 .cindex "header lines" "position of removed lines"
29986 .cindex "&%remove_header%& ACL modifier"
29987 The &%remove_header%& modifier can be used to remove one or more header lines
29988 from an incoming message, as in this example:
29989 .code
29990 warn message = Remove internal headers
29991 remove_header = x-route-mail1 : x-route-mail2
29992 .endd
29993 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
29994 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
29995 receiving a message). The message must ultimately be accepted for
29996 &%remove_header%& to have any significant effect. You can use &%remove_header%&
29997 with any ACL verb, including &%deny%&, though this is really not useful for
29998 any verb that doesn't result in a delivered message.
29999
30000 Headers will not be removed from the message if the modifier is used in
30001 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
30002
30003 More than one header can be removed at the same time by using a colon separated
30004 list of header names. The header matching is case insensitive. Wildcards are
30005 not permitted, nor is list expansion performed, so you cannot use hostlists to
30006 create a list of headers, however both connection and message variable expansion
30007 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
30008 .code
30009 warn hosts = +internal_hosts
30010 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
30011 warn message = Remove internal headers
30012 remove_header = $acl_c_ihdrs
30013 .endd
30014 Header names for removal are accumulated during the MAIL, RCPT, and predata ACLs.
30015 Matching header lines are removed from the message before processing the DATA and MIME ACLs.
30016 If multiple header lines match, all are removed.
30017 There is no harm in attempting to remove the same header twice nor in removing
30018 a non-existent header. Further header lines to be removed may be accumulated
30019 during the DATA and MIME ACLs, after which they are removed from the message,
30020 if present. In the case of non-SMTP messages, headers to be removed are
30021 accumulated during the non-SMTP ACLs, and are removed from the message after
30022 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
30023 ACL, there really is no effect because there is no logging of what headers
30024 would have been removed.
30025
30026 .cindex "header lines" "removed; visibility of"
30027 Header lines are not visible in string expansions until the DATA phase when it
30028 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
30029 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
30030 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
30031 this restriction, you cannot use header lines as a way of controlling data
30032 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
30033 you should instead use ACL variables, as described in section
30034 &<<SECTaclvariables>>&.
30035
30036 The &%remove_header%& modifier acts immediately as it is encountered during the
30037 processing of an ACL. Notice the difference between these two cases:
30038 .display
30039 &`accept remove_header = X-Internal`&
30040 &` `&<&'some condition'&>
30041
30042 &`accept `&<&'some condition'&>
30043 &` remove_header = X-Internal`&
30044 .endd
30045 In the first case, the header line is always removed, whether or not the
30046 condition is true. In the second case, the header line is removed only if the
30047 condition is true. Multiple occurrences of &%remove_header%& may occur in the
30048 same ACL statement. All those that are encountered before a condition fails
30049 are honoured.
30050
30051 &*Warning*&: This facility currently applies only to header lines that are
30052 present during ACL processing. It does NOT remove header lines that are added
30053 in a system filter or in a router or transport.
30054
30055
30056
30057
30058 .section "ACL conditions" "SECTaclconditions"
30059 .cindex "&ACL;" "conditions; list of"
30060 Some of the conditions listed in this section are available only when Exim is
30061 compiled with the content-scanning extension. They are included here briefly
30062 for completeness. More detailed descriptions can be found in the discussion on
30063 content scanning in chapter &<<CHAPexiscan>>&.
30064
30065 Not all conditions are relevant in all circumstances. For example, testing
30066 senders and recipients does not make sense in an ACL that is being run as the
30067 result of the arrival of an ETRN command, and checks on message headers can be
30068 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
30069 can use the same condition (with different parameters) more than once in the
30070 same ACL statement. This provides a way of specifying an &"and"& conjunction.
30071 The conditions are as follows:
30072
30073
30074 .vlist
30075 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
30076 .cindex "&ACL;" "nested"
30077 .cindex "&ACL;" "indirect"
30078 .cindex "&ACL;" "arguments"
30079 .cindex "&%acl%& ACL condition"
30080 The possible values of the argument are the same as for the
30081 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
30082 &"accept"& the condition is true; if it returns &"deny"& the condition is
30083 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
30084 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
30085 condition false. This means that further processing of the &%warn%& verb
30086 ceases, but processing of the ACL continues.
30087
30088 If the argument is a named ACL, up to nine space-separated optional values
30089 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
30090 and $acl_narg is set to the count of values.
30091 Previous values of these variables are restored after the call returns.
30092 The name and values are expanded separately.
30093 Note that spaces in complex expansions which are used as arguments
30094 will act as argument separators.
30095
30096 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
30097 the connection is dropped. If it returns &"discard"&, the verb must be
30098 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
30099 conditions are tested.
30100
30101 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
30102 loops. This condition allows you to use different ACLs in different
30103 circumstances. For example, different ACLs can be used to handle RCPT commands
30104 for different local users or different local domains.
30105
30106 .vitem &*authenticated&~=&~*&<&'string&~list'&>
30107 .cindex "&%authenticated%& ACL condition"
30108 .cindex "authentication" "ACL checking"
30109 .cindex "&ACL;" "testing for authentication"
30110 If the SMTP connection is not authenticated, the condition is false. Otherwise,
30111 the name of the authenticator is tested against the list. To test for
30112 authentication by any authenticator, you can set
30113 .code
30114 authenticated = *
30115 .endd
30116
30117 .vitem &*condition&~=&~*&<&'string'&>
30118 .cindex "&%condition%& ACL condition"
30119 .cindex "customizing" "ACL condition"
30120 .cindex "&ACL;" "customized test"
30121 .cindex "&ACL;" "testing, customized"
30122 This feature allows you to make up custom conditions. If the result of
30123 expanding the string is an empty string, the number zero, or one of the strings
30124 &"no"& or &"false"&, the condition is false. If the result is any non-zero
30125 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
30126 any other value, some error is assumed to have occurred, and the ACL returns
30127 &"defer"&. However, if the expansion is forced to fail, the condition is
30128 ignored. The effect is to treat it as true, whether it is positive or
30129 negative.
30130
30131 .vitem &*decode&~=&~*&<&'location'&>
30132 .cindex "&%decode%& ACL condition"
30133 This condition is available only when Exim is compiled with the
30134 content-scanning extension, and it is allowed only in the ACL defined by
30135 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
30136 If all goes well, the condition is true. It is false only if there are
30137 problems such as a syntax error or a memory shortage. For more details, see
30138 chapter &<<CHAPexiscan>>&.
30139
30140 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
30141 .cindex "&%dnslists%& ACL condition"
30142 .cindex "DNS list" "in ACL"
30143 .cindex "black list (DNS)"
30144 .cindex "&ACL;" "testing a DNS list"
30145 This condition checks for entries in DNS black lists. These are also known as
30146 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
30147 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
30148 different variants of this condition to describe briefly here. See sections
30149 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
30150
30151 .vitem &*domains&~=&~*&<&'domain&~list'&>
30152 .cindex "&%domains%& ACL condition"
30153 .cindex "domain" "ACL checking"
30154 .cindex "&ACL;" "testing a recipient domain"
30155 .vindex "&$domain_data$&"
30156 This condition is relevant only after a RCPT command. It checks that the domain
30157 of the recipient address is in the domain list. If percent-hack processing is
30158 enabled, it is done before this test is done. If the check succeeds with a
30159 lookup, the result of the lookup is placed in &$domain_data$& until the next
30160 &%domains%& test.
30161
30162 &*Note carefully*& (because many people seem to fall foul of this): you cannot
30163 use &%domains%& in a DATA ACL.
30164
30165
30166 .vitem &*encrypted&~=&~*&<&'string&~list'&>
30167 .cindex "&%encrypted%& ACL condition"
30168 .cindex "encryption" "checking in an ACL"
30169 .cindex "&ACL;" "testing for encryption"
30170 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
30171 name of the cipher suite in use is tested against the list. To test for
30172 encryption without testing for any specific cipher suite(s), set
30173 .code
30174 encrypted = *
30175 .endd
30176
30177
30178 .vitem &*hosts&~=&~*&<&'host&~list'&>
30179 .cindex "&%hosts%& ACL condition"
30180 .cindex "host" "ACL checking"
30181 .cindex "&ACL;" "testing the client host"
30182 This condition tests that the calling host matches the host list. If you have
30183 name lookups or wildcarded host names and IP addresses in the same host list,
30184 you should normally put the IP addresses first. For example, you could have:
30185 .code
30186 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
30187 .endd
30188 The lookup in this example uses the host name for its key. This is implied by
30189 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
30190 and it wouldn't matter which way round you had these two items.)
30191
30192 The reason for the problem with host names lies in the left-to-right way that
30193 Exim processes lists. It can test IP addresses without doing any DNS lookups,
30194 but when it reaches an item that requires a host name, it fails if it cannot
30195 find a host name to compare with the pattern. If the above list is given in the
30196 opposite order, the &%accept%& statement fails for a host whose name cannot be
30197 found, even if its IP address is 10.9.8.7.
30198
30199 If you really do want to do the name check first, and still recognize the IP
30200 address even if the name lookup fails, you can rewrite the ACL like this:
30201 .code
30202 accept hosts = dbm;/etc/friendly/hosts
30203 accept hosts = 10.9.8.7
30204 .endd
30205 The default action on failing to find the host name is to assume that the host
30206 is not in the list, so the first &%accept%& statement fails. The second
30207 statement can then check the IP address.
30208
30209 .vindex "&$host_data$&"
30210 If a &%hosts%& condition is satisfied by means of a lookup, the result
30211 of the lookup is made available in the &$host_data$& variable. This
30212 allows you, for example, to set up a statement like this:
30213 .code
30214 deny hosts = net-lsearch;/some/file
30215 message = $host_data
30216 .endd
30217 which gives a custom error message for each denied host.
30218
30219 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
30220 .cindex "&%local_parts%& ACL condition"
30221 .cindex "local part" "ACL checking"
30222 .cindex "&ACL;" "testing a local part"
30223 .vindex "&$local_part_data$&"
30224 This condition is relevant only after a RCPT command. It checks that the local
30225 part of the recipient address is in the list. If percent-hack processing is
30226 enabled, it is done before this test. If the check succeeds with a lookup, the
30227 result of the lookup is placed in &$local_part_data$&, which remains set until
30228 the next &%local_parts%& test.
30229
30230 .vitem &*malware&~=&~*&<&'option'&>
30231 .cindex "&%malware%& ACL condition"
30232 .cindex "&ACL;" "virus scanning"
30233 .cindex "&ACL;" "scanning for viruses"
30234 This condition is available only when Exim is compiled with the
30235 content-scanning extension. It causes the incoming message to be scanned for
30236 viruses. For details, see chapter &<<CHAPexiscan>>&.
30237
30238 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
30239 .cindex "&%mime_regex%& ACL condition"
30240 .cindex "&ACL;" "testing by regex matching"
30241 This condition is available only when Exim is compiled with the
30242 content-scanning extension, and it is allowed only in the ACL defined by
30243 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
30244 with any of the regular expressions. For details, see chapter
30245 &<<CHAPexiscan>>&.
30246
30247 .vitem &*ratelimit&~=&~*&<&'parameters'&>
30248 .cindex "rate limiting"
30249 This condition can be used to limit the rate at which a user or host submits
30250 messages. Details are given in section &<<SECTratelimiting>>&.
30251
30252 .vitem &*recipients&~=&~*&<&'address&~list'&>
30253 .cindex "&%recipients%& ACL condition"
30254 .cindex "recipient" "ACL checking"
30255 .cindex "&ACL;" "testing a recipient"
30256 This condition is relevant only after a RCPT command. It checks the entire
30257 recipient address against a list of recipients.
30258
30259 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
30260 .cindex "&%regex%& ACL condition"
30261 .cindex "&ACL;" "testing by regex matching"
30262 This condition is available only when Exim is compiled with the
30263 content-scanning extension, and is available only in the DATA, MIME, and
30264 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
30265 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
30266
30267 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
30268 .cindex "&%sender_domains%& ACL condition"
30269 .cindex "sender" "ACL checking"
30270 .cindex "&ACL;" "testing a sender domain"
30271 .vindex "&$domain$&"
30272 .vindex "&$sender_address_domain$&"
30273 This condition tests the domain of the sender of the message against the given
30274 domain list. &*Note*&: The domain of the sender address is in
30275 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
30276 of this condition. This is an exception to the general rule for testing domain
30277 lists. It is done this way so that, if this condition is used in an ACL for a
30278 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
30279 influence the sender checking.
30280
30281 &*Warning*&: It is a bad idea to use this condition on its own as a control on
30282 relaying, because sender addresses are easily, and commonly, forged.
30283
30284 .vitem &*senders&~=&~*&<&'address&~list'&>
30285 .cindex "&%senders%& ACL condition"
30286 .cindex "sender" "ACL checking"
30287 .cindex "&ACL;" "testing a sender"
30288 This condition tests the sender of the message against the given list. To test
30289 for a bounce message, which has an empty sender, set
30290 .code
30291 senders = :
30292 .endd
30293 &*Warning*&: It is a bad idea to use this condition on its own as a control on
30294 relaying, because sender addresses are easily, and commonly, forged.
30295
30296 .vitem &*spam&~=&~*&<&'username'&>
30297 .cindex "&%spam%& ACL condition"
30298 .cindex "&ACL;" "scanning for spam"
30299 This condition is available only when Exim is compiled with the
30300 content-scanning extension. It causes the incoming message to be scanned by
30301 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
30302
30303 .vitem &*verify&~=&~certificate*&
30304 .cindex "&%verify%& ACL condition"
30305 .cindex "TLS" "client certificate verification"
30306 .cindex "certificate" "verification of client"
30307 .cindex "&ACL;" "certificate verification"
30308 .cindex "&ACL;" "testing a TLS certificate"
30309 This condition is true in an SMTP session if the session is encrypted, and a
30310 certificate was received from the client, and the certificate was verified. The
30311 server requests a certificate only if the client matches &%tls_verify_hosts%&
30312 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
30313
30314 .vitem &*verify&~=&~csa*&
30315 .cindex "CSA verification"
30316 This condition checks whether the sending host (the client) is authorized to
30317 send email. Details of how this works are given in section
30318 &<<SECTverifyCSA>>&.
30319
30320 .vitem &*verify&~=&~header_names_ascii*&
30321 .cindex "&%verify%& ACL condition"
30322 .cindex "&ACL;" "verifying header names only ASCII"
30323 .cindex "header lines" "verifying header names only ASCII"
30324 .cindex "verifying" "header names only ASCII"
30325 This condition is relevant only in an ACL that is run after a message has been
30326 received, that is, in an ACL specified by &%acl_smtp_data%& or
30327 &%acl_not_smtp%&. It checks all header names (not the content) to make sure
30328 there are no non-ASCII characters, also excluding control characters. The
30329 allowable characters are decimal ASCII values 33 through 126.
30330
30331 Exim itself will handle headers with non-ASCII characters, but it can cause
30332 problems for downstream applications, so this option will allow their
30333 detection and rejection in the DATA ACL's.
30334
30335 .vitem &*verify&~=&~header_sender/*&<&'options'&>
30336 .cindex "&%verify%& ACL condition"
30337 .cindex "&ACL;" "verifying sender in the header"
30338 .cindex "header lines" "verifying the sender in"
30339 .cindex "sender" "verifying in header"
30340 .cindex "verifying" "sender in header"
30341 This condition is relevant only in an ACL that is run after a message has been
30342 received, that is, in an ACL specified by &%acl_smtp_data%& or
30343 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
30344 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
30345 is loosely thought of as a &"sender"& address (hence the name of the test).
30346 However, an address that appears in one of these headers need not be an address
30347 that accepts bounce messages; only sender addresses in envelopes are required
30348 to accept bounces. Therefore, if you use the callout option on this check, you
30349 might want to arrange for a non-empty address in the MAIL command.
30350
30351 Details of address verification and the options are given later, starting at
30352 section &<<SECTaddressverification>>& (callouts are described in section
30353 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
30354 condition to restrict it to bounce messages only:
30355 .code
30356 deny senders = :
30357 message = A valid sender header is required for bounces
30358 !verify = header_sender
30359 .endd
30360
30361 .vitem &*verify&~=&~header_syntax*&
30362 .cindex "&%verify%& ACL condition"
30363 .cindex "&ACL;" "verifying header syntax"
30364 .cindex "header lines" "verifying syntax"
30365 .cindex "verifying" "header syntax"
30366 This condition is relevant only in an ACL that is run after a message has been
30367 received, that is, in an ACL specified by &%acl_smtp_data%& or
30368 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
30369 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
30370 and &'Bcc:'&), returning true if there are no problems.
30371 Unqualified addresses (local parts without domains) are
30372 permitted only in locally generated messages and from hosts that match
30373 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
30374 appropriate.
30375
30376 Note that this condition is a syntax check only. However, a common spamming
30377 ploy used to be to send syntactically invalid headers such as
30378 .code
30379 To: @
30380 .endd
30381 and this condition can be used to reject such messages, though they are not as
30382 common as they used to be.
30383
30384 .vitem &*verify&~=&~helo*&
30385 .cindex "&%verify%& ACL condition"
30386 .cindex "&ACL;" "verifying HELO/EHLO"
30387 .cindex "HELO" "verifying"
30388 .cindex "EHLO" "verifying"
30389 .cindex "verifying" "EHLO"
30390 .cindex "verifying" "HELO"
30391 This condition is true if a HELO or EHLO command has been received from the
30392 client host, and its contents have been verified. If there has been no previous
30393 attempt to verify the HELO/EHLO contents, it is carried out when this
30394 condition is encountered. See the description of the &%helo_verify_hosts%& and
30395 &%helo_try_verify_hosts%& options for details of how to request verification
30396 independently of this condition.
30397
30398 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
30399 option), this condition is always true.
30400
30401
30402 .vitem &*verify&~=&~not_blind*&
30403 .cindex "verifying" "not blind"
30404 .cindex "bcc recipients, verifying none"
30405 This condition checks that there are no blind (bcc) recipients in the message.
30406 Every envelope recipient must appear either in a &'To:'& header line or in a
30407 &'Cc:'& header line for this condition to be true. Local parts are checked
30408 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
30409 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
30410 used only in a DATA or non-SMTP ACL.
30411
30412 There are, of course, many legitimate messages that make use of blind (bcc)
30413 recipients. This check should not be used on its own for blocking messages.
30414
30415
30416 .vitem &*verify&~=&~recipient/*&<&'options'&>
30417 .cindex "&%verify%& ACL condition"
30418 .cindex "&ACL;" "verifying recipient"
30419 .cindex "recipient" "verifying"
30420 .cindex "verifying" "recipient"
30421 .vindex "&$address_data$&"
30422 This condition is relevant only after a RCPT command. It verifies the current
30423 recipient. Details of address verification are given later, starting at section
30424 &<<SECTaddressverification>>&. After a recipient has been verified, the value
30425 of &$address_data$& is the last value that was set while routing the address.
30426 This applies even if the verification fails. When an address that is being
30427 verified is redirected to a single address, verification continues with the new
30428 address, and in that case, the subsequent value of &$address_data$& is the
30429 value for the child address.
30430
30431 .vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
30432 .cindex "&%verify%& ACL condition"
30433 .cindex "&ACL;" "verifying host reverse lookup"
30434 .cindex "host" "verifying reverse lookup"
30435 This condition ensures that a verified host name has been looked up from the IP
30436 address of the client host. (This may have happened already if the host name
30437 was needed for checking a host list, or if the host matched &%host_lookup%&.)
30438 Verification ensures that the host name obtained from a reverse DNS lookup, or
30439 one of its aliases, does, when it is itself looked up in the DNS, yield the
30440 original IP address.
30441
30442 There is one possible option, &`defer_ok`&. If this is present and a
30443 DNS operation returns a temporary error, the verify condition succeeds.
30444
30445 If this condition is used for a locally generated message (that is, when there
30446 is no client host involved), it always succeeds.
30447
30448 .vitem &*verify&~=&~sender/*&<&'options'&>
30449 .cindex "&%verify%& ACL condition"
30450 .cindex "&ACL;" "verifying sender"
30451 .cindex "sender" "verifying"
30452 .cindex "verifying" "sender"
30453 This condition is relevant only after a MAIL or RCPT command, or after a
30454 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
30455 the message's sender is empty (that is, this is a bounce message), the
30456 condition is true. Otherwise, the sender address is verified.
30457
30458 .vindex "&$address_data$&"
30459 .vindex "&$sender_address_data$&"
30460 If there is data in the &$address_data$& variable at the end of routing, its
30461 value is placed in &$sender_address_data$& at the end of verification. This
30462 value can be used in subsequent conditions and modifiers in the same ACL
30463 statement. It does not persist after the end of the current statement. If you
30464 want to preserve the value for longer, you can save it in an ACL variable.
30465
30466 Details of verification are given later, starting at section
30467 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
30468 to avoid doing it more than once per message.
30469
30470 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
30471 .cindex "&%verify%& ACL condition"
30472 This is a variation of the previous option, in which a modified address is
30473 verified as a sender.
30474
30475 Note that '/' is legal in local-parts; if the address may have such
30476 (eg. is generated from the received message)
30477 they must be protected from the options parsing by doubling:
30478 .code
30479 verify = sender=${sg{${address:$h_sender:}}{/}{//}}
30480 .endd
30481 .endlist
30482
30483
30484
30485 .section "Using DNS lists" "SECTmorednslists"
30486 .cindex "DNS list" "in ACL"
30487 .cindex "black list (DNS)"
30488 .cindex "&ACL;" "testing a DNS list"
30489 In its simplest form, the &%dnslists%& condition tests whether the calling host
30490 is on at least one of a number of DNS lists by looking up the inverted IP
30491 address in one or more DNS domains. (Note that DNS list domains are not mail
30492 domains, so the &`+`& syntax for named lists doesn't work - it is used for
30493 special options instead.) For example, if the calling host's IP
30494 address is 192.168.62.43, and the ACL statement is
30495 .code
30496 deny dnslists = blackholes.mail-abuse.org : \
30497 dialups.mail-abuse.org
30498 .endd
30499 the following records are looked up:
30500 .code
30501 43.62.168.192.blackholes.mail-abuse.org
30502 43.62.168.192.dialups.mail-abuse.org
30503 .endd
30504 As soon as Exim finds an existing DNS record, processing of the list stops.
30505 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
30506 to test that a host is on more than one list (an &"and"& conjunction), you can
30507 use two separate conditions:
30508 .code
30509 deny dnslists = blackholes.mail-abuse.org
30510 dnslists = dialups.mail-abuse.org
30511 .endd
30512 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
30513 behaves as if the host does not match the list item, that is, as if the DNS
30514 record does not exist. If there are further items in the DNS list, they are
30515 processed.
30516
30517 This is usually the required action when &%dnslists%& is used with &%deny%&
30518 (which is the most common usage), because it prevents a DNS failure from
30519 blocking mail. However, you can change this behaviour by putting one of the
30520 following special items in the list:
30521 .display
30522 &`+include_unknown `& behave as if the item is on the list
30523 &`+exclude_unknown `& behave as if the item is not on the list (default)
30524 &`+defer_unknown `& give a temporary error
30525 .endd
30526 .cindex "&`+include_unknown`&"
30527 .cindex "&`+exclude_unknown`&"
30528 .cindex "&`+defer_unknown`&"
30529 Each of these applies to any subsequent items on the list. For example:
30530 .code
30531 deny dnslists = +defer_unknown : foo.bar.example
30532 .endd
30533 Testing the list of domains stops as soon as a match is found. If you want to
30534 warn for one list and block for another, you can use two different statements:
30535 .code
30536 deny dnslists = blackholes.mail-abuse.org
30537 warn message = X-Warn: sending host is on dialups list
30538 dnslists = dialups.mail-abuse.org
30539 .endd
30540 .cindex caching "of dns lookup"
30541 .cindex DNS TTL
30542 DNS list lookups are cached by Exim for the duration of the SMTP session
30543 (but limited by the DNS return TTL value),
30544 so a lookup based on the IP address is done at most once for any incoming
30545 connection (assuming long-enough TTL).
30546 Exim does not share information between multiple incoming
30547 connections (but your local name server cache should be active).
30548
30549
30550
30551 .section "Specifying the IP address for a DNS list lookup" "SECID201"
30552 .cindex "DNS list" "keyed by explicit IP address"
30553 By default, the IP address that is used in a DNS list lookup is the IP address
30554 of the calling host. However, you can specify another IP address by listing it
30555 after the domain name, introduced by a slash. For example:
30556 .code
30557 deny dnslists = black.list.tld/192.168.1.2
30558 .endd
30559 This feature is not very helpful with explicit IP addresses; it is intended for
30560 use with IP addresses that are looked up, for example, the IP addresses of the
30561 MX hosts or nameservers of an email sender address. For an example, see section
30562 &<<SECTmulkeyfor>>& below.
30563
30564
30565
30566
30567 .section "DNS lists keyed on domain names" "SECID202"
30568 .cindex "DNS list" "keyed by domain name"
30569 There are some lists that are keyed on domain names rather than inverted IP
30570 addresses (see for example the &'domain based zones'& link at
30571 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
30572 with these lists. You can change the name that is looked up in a DNS list by
30573 listing it after the domain name, introduced by a slash. For example,
30574 .code
30575 deny message = Sender's domain is listed at $dnslist_domain
30576 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
30577 .endd
30578 This particular example is useful only in ACLs that are obeyed after the
30579 RCPT or DATA commands, when a sender address is available. If (for
30580 example) the message's sender is &'user@tld.example'& the name that is looked
30581 up by this example is
30582 .code
30583 tld.example.dsn.rfc-ignorant.org
30584 .endd
30585 A single &%dnslists%& condition can contain entries for both names and IP
30586 addresses. For example:
30587 .code
30588 deny dnslists = sbl.spamhaus.org : \
30589 dsn.rfc-ignorant.org/$sender_address_domain
30590 .endd
30591 The first item checks the sending host's IP address; the second checks a domain
30592 name. The whole condition is true if either of the DNS lookups succeeds.
30593
30594
30595
30596
30597 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
30598 .cindex "DNS list" "multiple keys for"
30599 The syntax described above for looking up explicitly-defined values (either
30600 names or IP addresses) in a DNS blacklist is a simplification. After the domain
30601 name for the DNS list, what follows the slash can in fact be a list of items.
30602 As with all lists in Exim, the default separator is a colon. However, because
30603 this is a sublist within the list of DNS blacklist domains, it is necessary
30604 either to double the separators like this:
30605 .code
30606 dnslists = black.list.tld/name.1::name.2
30607 .endd
30608 or to change the separator character, like this:
30609 .code
30610 dnslists = black.list.tld/<;name.1;name.2
30611 .endd
30612 If an item in the list is an IP address, it is inverted before the DNS
30613 blacklist domain is appended. If it is not an IP address, no inversion
30614 occurs. Consider this condition:
30615 .code
30616 dnslists = black.list.tld/<;192.168.1.2;a.domain
30617 .endd
30618 The DNS lookups that occur are:
30619 .code
30620 2.1.168.192.black.list.tld
30621 a.domain.black.list.tld
30622 .endd
30623 Once a DNS record has been found (that matches a specific IP return
30624 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
30625 are done. If there is a temporary DNS error, the rest of the sublist of domains
30626 or IP addresses is tried. A temporary error for the whole dnslists item occurs
30627 only if no other DNS lookup in this sublist succeeds. In other words, a
30628 successful lookup for any of the items in the sublist overrides a temporary
30629 error for a previous item.
30630
30631 The ability to supply a list of items after the slash is in some sense just a
30632 syntactic convenience. These two examples have the same effect:
30633 .code
30634 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
30635 dnslists = black.list.tld/a.domain::b.domain
30636 .endd
30637 However, when the data for the list is obtained from a lookup, the second form
30638 is usually much more convenient. Consider this example:
30639 .code
30640 deny message = The mail servers for the domain \
30641 $sender_address_domain \
30642 are listed at $dnslist_domain ($dnslist_value); \
30643 see $dnslist_text.
30644 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
30645 ${lookup dnsdb {>|mxh=\
30646 $sender_address_domain} }} }
30647 .endd
30648 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
30649 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
30650 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
30651 of expanding the condition might be something like this:
30652 .code
30653 dnslists = sbl.spamhaus.org/<|192.168.2.3|192.168.5.6|...
30654 .endd
30655 Thus, this example checks whether or not the IP addresses of the sender
30656 domain's mail servers are on the Spamhaus black list.
30657
30658 The key that was used for a successful DNS list lookup is put into the variable
30659 &$dnslist_matched$& (see section &<<SECID204>>&).
30660
30661
30662
30663
30664 .section "Data returned by DNS lists" "SECID203"
30665 .cindex "DNS list" "data returned from"
30666 DNS lists are constructed using address records in the DNS. The original RBL
30667 just used the address 127.0.0.1 on the right hand side of each record, but the
30668 RBL+ list and some other lists use a number of values with different meanings.
30669 The values used on the RBL+ list are:
30670 .display
30671 127.1.0.1 RBL
30672 127.1.0.2 DUL
30673 127.1.0.3 DUL and RBL
30674 127.1.0.4 RSS
30675 127.1.0.5 RSS and RBL
30676 127.1.0.6 RSS and DUL
30677 127.1.0.7 RSS and DUL and RBL
30678 .endd
30679 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
30680 different values. Some DNS lists may return more than one address record;
30681 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
30682
30683
30684 .section "Variables set from DNS lists" "SECID204"
30685 .cindex "expansion" "variables, set from DNS list"
30686 .cindex "DNS list" "variables set from"
30687 .vindex "&$dnslist_domain$&"
30688 .vindex "&$dnslist_matched$&"
30689 .vindex "&$dnslist_text$&"
30690 .vindex "&$dnslist_value$&"
30691 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
30692 the name of the overall domain that matched (for example,
30693 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
30694 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
30695 the DNS record. When the key is an IP address, it is not reversed in
30696 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
30697 cases, for example:
30698 .code
30699 deny dnslists = spamhaus.example
30700 .endd
30701 the key is also available in another variable (in this case,
30702 &$sender_host_address$&). In more complicated cases, however, this is not true.
30703 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
30704 might generate a dnslists lookup like this:
30705 .code
30706 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
30707 .endd
30708 If this condition succeeds, the value in &$dnslist_matched$& might be
30709 &`192.168.6.7`& (for example).
30710
30711 If more than one address record is returned by the DNS lookup, all the IP
30712 addresses are included in &$dnslist_value$&, separated by commas and spaces.
30713 The variable &$dnslist_text$& contains the contents of any associated TXT
30714 record. For lists such as RBL+ the TXT record for a merged entry is often not
30715 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
30716 information.
30717
30718 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
30719 &-- although these appear before the condition in the ACL, they are not
30720 expanded until after it has failed. For example:
30721 .code
30722 deny hosts = !+local_networks
30723 message = $sender_host_address is listed \
30724 at $dnslist_domain
30725 dnslists = rbl-plus.mail-abuse.example
30726 .endd
30727
30728
30729
30730 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
30731 .cindex "DNS list" "matching specific returned data"
30732 You can add an equals sign and an IP address after a &%dnslists%& domain name
30733 in order to restrict its action to DNS records with a matching right hand side.
30734 For example,
30735 .code
30736 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
30737 .endd
30738 rejects only those hosts that yield 127.0.0.2. Without this additional data,
30739 any address record is considered to be a match. For the moment, we assume
30740 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
30741 describes how multiple records are handled.
30742
30743 More than one IP address may be given for checking, using a comma as a
30744 separator. These are alternatives &-- if any one of them matches, the
30745 &%dnslists%& condition is true. For example:
30746 .code
30747 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
30748 .endd
30749 If you want to specify a constraining address list and also specify names or IP
30750 addresses to be looked up, the constraining address list must be specified
30751 first. For example:
30752 .code
30753 deny dnslists = dsn.rfc-ignorant.org\
30754 =127.0.0.2/$sender_address_domain
30755 .endd
30756
30757 If the character &`&&`& is used instead of &`=`&, the comparison for each
30758 listed IP address is done by a bitwise &"and"& instead of by an equality test.
30759 In other words, the listed addresses are used as bit masks. The comparison is
30760 true if all the bits in the mask are present in the address that is being
30761 tested. For example:
30762 .code
30763 dnslists = a.b.c&0.0.0.3
30764 .endd
30765 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
30766 want to test whether one bit or another bit is present (as opposed to both
30767 being present), you must use multiple values. For example:
30768 .code
30769 dnslists = a.b.c&0.0.0.1,0.0.0.2
30770 .endd
30771 matches if the final component of the address is an odd number or two times
30772 an odd number.
30773
30774
30775
30776 .section "Negated DNS matching conditions" "SECID205"
30777 You can supply a negative list of IP addresses as part of a &%dnslists%&
30778 condition. Whereas
30779 .code
30780 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
30781 .endd
30782 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
30783 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
30784 .code
30785 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
30786 .endd
30787 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
30788 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
30789 words, the result of the test is inverted if an exclamation mark appears before
30790 the &`=`& (or the &`&&`&) sign.
30791
30792 &*Note*&: This kind of negation is not the same as negation in a domain,
30793 host, or address list (which is why the syntax is different).
30794
30795 If you are using just one list, the negation syntax does not gain you much. The
30796 previous example is precisely equivalent to
30797 .code
30798 deny dnslists = a.b.c
30799 !dnslists = a.b.c=127.0.0.2,127.0.0.3
30800 .endd
30801 However, if you are using multiple lists, the negation syntax is clearer.
30802 Consider this example:
30803 .code
30804 deny dnslists = sbl.spamhaus.org : \
30805 list.dsbl.org : \
30806 dnsbl.njabl.org!=127.0.0.3 : \
30807 relays.ordb.org
30808 .endd
30809 Using only positive lists, this would have to be:
30810 .code
30811 deny dnslists = sbl.spamhaus.org : \
30812 list.dsbl.org
30813 deny dnslists = dnsbl.njabl.org
30814 !dnslists = dnsbl.njabl.org=127.0.0.3
30815 deny dnslists = relays.ordb.org
30816 .endd
30817 which is less clear, and harder to maintain.
30818
30819
30820
30821
30822 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
30823 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
30824 thereby providing more than one IP address. When an item in a &%dnslists%& list
30825 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
30826 the match to specific results from the DNS lookup, there are two ways in which
30827 the checking can be handled. For example, consider the condition:
30828 .code
30829 dnslists = a.b.c=127.0.0.1
30830 .endd
30831 What happens if the DNS lookup for the incoming IP address yields both
30832 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
30833 condition true because at least one given value was found, or is it false
30834 because at least one of the found values was not listed? And how does this
30835 affect negated conditions? Both possibilities are provided for with the help of
30836 additional separators &`==`& and &`=&&`&.
30837
30838 .ilist
30839 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
30840 IP addresses matches one of the listed addresses. For the example above, the
30841 condition is true because 127.0.0.1 matches.
30842 .next
30843 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
30844 looked up IP addresses matches one of the listed addresses. If the condition is
30845 changed to:
30846 .code
30847 dnslists = a.b.c==127.0.0.1
30848 .endd
30849 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
30850 false because 127.0.0.2 is not listed. You would need to have:
30851 .code
30852 dnslists = a.b.c==127.0.0.1,127.0.0.2
30853 .endd
30854 for the condition to be true.
30855 .endlist
30856
30857 When &`!`& is used to negate IP address matching, it inverts the result, giving
30858 the precise opposite of the behaviour above. Thus:
30859 .ilist
30860 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
30861 addresses matches one of the listed addresses. Consider:
30862 .code
30863 dnslists = a.b.c!&0.0.0.1
30864 .endd
30865 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
30866 false because 127.0.0.1 matches.
30867 .next
30868 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
30869 looked up IP address that does not match. Consider:
30870 .code
30871 dnslists = a.b.c!=&0.0.0.1
30872 .endd
30873 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
30874 true, because 127.0.0.2 does not match. You would need to have:
30875 .code
30876 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
30877 .endd
30878 for the condition to be false.
30879 .endlist
30880 When the DNS lookup yields only a single IP address, there is no difference
30881 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
30882
30883
30884
30885
30886 .section "Detailed information from merged DNS lists" "SECTmordetinf"
30887 .cindex "DNS list" "information from merged"
30888 When the facility for restricting the matching IP values in a DNS list is used,
30889 the text from the TXT record that is set in &$dnslist_text$& may not reflect
30890 the true reason for rejection. This happens when lists are merged and the IP
30891 address in the A record is used to distinguish them; unfortunately there is
30892 only one TXT record. One way round this is not to use merged lists, but that
30893 can be inefficient because it requires multiple DNS lookups where one would do
30894 in the vast majority of cases when the host of interest is not on any of the
30895 lists.
30896
30897 A less inefficient way of solving this problem is available. If
30898 two domain names, comma-separated, are given, the second is used first to
30899 do an initial check, making use of any IP value restrictions that are set.
30900 If there is a match, the first domain is used, without any IP value
30901 restrictions, to get the TXT record. As a byproduct of this, there is also
30902 a check that the IP being tested is indeed on the first list. The first
30903 domain is the one that is put in &$dnslist_domain$&. For example:
30904 .code
30905 deny message = \
30906 rejected because $sender_host_address is blacklisted \
30907 at $dnslist_domain\n$dnslist_text
30908 dnslists = \
30909 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
30910 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
30911 .endd
30912 For the first blacklist item, this starts by doing a lookup in
30913 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
30914 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
30915 value, and as long as something is found, it looks for the corresponding TXT
30916 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
30917 The second blacklist item is processed similarly.
30918
30919 If you are interested in more than one merged list, the same list must be
30920 given several times, but because the results of the DNS lookups are cached,
30921 the DNS calls themselves are not repeated. For example:
30922 .code
30923 deny dnslists = \
30924 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
30925 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
30926 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
30927 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
30928 .endd
30929 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
30930 values matches (or if no record is found), this is the only lookup that is
30931 done. Only if there is a match is one of the more specific lists consulted.
30932
30933
30934
30935 .section "DNS lists and IPv6" "SECTmorednslistslast"
30936 .cindex "IPv6" "DNS black lists"
30937 .cindex "DNS list" "IPv6 usage"
30938 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
30939 nibble by nibble. For example, if the calling host's IP address is
30940 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
30941 .code
30942 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
30943 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
30944 .endd
30945 (split over two lines here to fit on the page). Unfortunately, some of the DNS
30946 lists contain wildcard records, intended for IPv4, that interact badly with
30947 IPv6. For example, the DNS entry
30948 .code
30949 *.3.some.list.example. A 127.0.0.1
30950 .endd
30951 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
30952 Unfortunately, it also matches the entire 3::/4 IPv6 network.
30953
30954 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
30955 &%condition%& condition, as in this example:
30956 .code
30957 deny condition = ${if isip4{$sender_host_address}}
30958 dnslists = some.list.example
30959 .endd
30960
30961 If an explicit key is being used for a DNS lookup and it may be an IPv6
30962 address you should specify alternate list separators for both the outer
30963 (DNS list name) list and inner (lookup keys) list:
30964 .code
30965 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
30966 .endd
30967
30968 .section "Rate limiting incoming messages" "SECTratelimiting"
30969 .cindex "rate limiting" "client sending"
30970 .cindex "limiting client sending rates"
30971 .oindex "&%smtp_ratelimit_*%&"
30972 The &%ratelimit%& ACL condition can be used to measure and control the rate at
30973 which clients can send email. This is more powerful than the
30974 &%smtp_ratelimit_*%& options, because those options control the rate of
30975 commands in a single SMTP session only, whereas the &%ratelimit%& condition
30976 works across all connections (concurrent and sequential) from the same client
30977 host. The syntax of the &%ratelimit%& condition is:
30978 .display
30979 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
30980 .endd
30981 If the average client sending rate is less than &'m'& messages per time
30982 period &'p'& then the condition is false; otherwise it is true.
30983
30984 As a side-effect, the &%ratelimit%& condition sets the expansion variable
30985 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
30986 configured value of &'m'&, and &$sender_rate_period$& to the configured value
30987 of &'p'&.
30988
30989 The parameter &'p'& is the smoothing time constant, in the form of an Exim
30990 time interval, for example, &`8h`& for eight hours. A larger time constant
30991 means that it takes Exim longer to forget a client's past behaviour. The
30992 parameter &'m'& is the maximum number of messages that a client is permitted to
30993 send in each time interval. It also specifies the number of messages permitted
30994 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
30995 constant, you can allow a client to send more messages in a burst without
30996 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
30997 both small, messages must be sent at an even rate.
30998
30999 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
31000 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
31001 when deploying the &%ratelimit%& ACL condition. The script prints usage
31002 instructions when it is run with no arguments.
31003
31004 The key is used to look up the data for calculating the client's average
31005 sending rate. This data is stored in Exim's spool directory, alongside the
31006 retry and other hints databases. The default key is &$sender_host_address$&,
31007 which means Exim computes the sending rate of each client host IP address.
31008 By changing the key you can change how Exim identifies clients for the purpose
31009 of ratelimiting. For example, to limit the sending rate of each authenticated
31010 user, independent of the computer they are sending from, set the key to
31011 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
31012 example, &$authenticated_id$& is only meaningful if the client has
31013 authenticated (which you can check with the &%authenticated%& ACL condition).
31014
31015 The lookup key does not have to identify clients: If you want to limit the
31016 rate at which a recipient receives messages, you can use the key
31017 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
31018 ACL.
31019
31020 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
31021 specifies what Exim measures the rate of, for example messages or recipients
31022 or bytes. You can adjust the measurement using the &%unique=%& and/or
31023 &%count=%& options. You can also control when Exim updates the recorded rate
31024 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
31025 separated by a slash, like the other parameters. They may appear in any order.
31026
31027 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
31028 any options that alter the meaning of the stored data. The limit &'m'& is not
31029 stored, so you can alter the configured maximum rate and Exim will still
31030 remember clients' past behaviour. If you change the &%per_*%& mode or add or
31031 remove the &%unique=%& option, the lookup key changes so Exim will forget past
31032 behaviour. The lookup key is not affected by changes to the update mode and
31033 the &%count=%& option.
31034
31035
31036 .section "Ratelimit options for what is being measured" "ratoptmea"
31037 .cindex "rate limiting" "per_* options"
31038 The &%per_conn%& option limits the client's connection rate. It is not
31039 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
31040 &%acl_not_smtp_start%& ACLs.
31041
31042 The &%per_mail%& option limits the client's rate of sending messages. This is
31043 the default if none of the &%per_*%& options is specified. It can be used in
31044 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
31045 &%acl_smtp_data%&, or &%acl_not_smtp%&.
31046
31047 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
31048 the same ACLs as the &%per_mail%& option, though it is best to use this option
31049 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
31050 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
31051 in its MAIL command, which may be inaccurate or completely missing. You can
31052 follow the limit &'m'& in the configuration with K, M, or G to specify limits
31053 in kilobytes, megabytes, or gigabytes, respectively.
31054
31055 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
31056 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
31057 &%acl_smtp_mime%&, &%acl_smtp_data%&, or &%acl_smtp_rcpt%& ACLs. In
31058 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
31059 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
31060 in either case the rate limiting engine will see a message with many
31061 recipients as a large high-speed burst.
31062
31063 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
31064 number of different recipients that the client has sent messages to in the
31065 last time period. That is, if the client repeatedly sends messages to the same
31066 recipient, its measured rate is not increased. This option can only be used in
31067 &%acl_smtp_rcpt%&.
31068
31069 The &%per_cmd%& option causes Exim to recompute the rate every time the
31070 condition is processed. This can be used to limit the rate of any SMTP
31071 command. If it is used in multiple ACLs it can limit the aggregate rate of
31072 multiple different commands.
31073
31074 The &%count=%& option can be used to alter how much Exim adds to the client's
31075 measured rate. For example, the &%per_byte%& option is equivalent to
31076 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
31077 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
31078 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
31079
31080 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
31081
31082
31083 .section "Ratelimit update modes" "ratoptupd"
31084 .cindex "rate limiting" "reading data without updating"
31085 You can specify one of three options with the &%ratelimit%& condition to
31086 control when its database is updated. This section describes the &%readonly%&
31087 mode, and the next section describes the &%strict%& and &%leaky%& modes.
31088
31089 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
31090 previously-computed rate to check against the limit.
31091
31092 For example, you can test the client's sending rate and deny it access (when
31093 it is too fast) in the connect ACL. If the client passes this check then it
31094 can go on to send a message, in which case its recorded rate will be updated
31095 in the MAIL ACL. Subsequent connections from the same client will check this
31096 new rate.
31097 .code
31098 acl_check_connect:
31099 deny ratelimit = 100 / 5m / readonly
31100 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
31101 (max $sender_rate_limit)
31102 # ...
31103 acl_check_mail:
31104 warn ratelimit = 100 / 5m / strict
31105 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
31106 (max $sender_rate_limit)
31107 .endd
31108
31109 If Exim encounters multiple &%ratelimit%& conditions with the same key when
31110 processing a message then it may increase the client's measured rate more than
31111 it should. For example, this will happen if you check the &%per_rcpt%& option
31112 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
31113 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
31114 multiple update problems by using the &%readonly%& option on later ratelimit
31115 checks.
31116
31117 The &%per_*%& options described above do not make sense in some ACLs. If you
31118 use a &%per_*%& option in an ACL where it is not normally permitted then the
31119 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
31120 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
31121 next section) so you must specify the &%readonly%& option explicitly.
31122
31123
31124 .section "Ratelimit options for handling fast clients" "ratoptfast"
31125 .cindex "rate limiting" "strict and leaky modes"
31126 If a client's average rate is greater than the maximum, the rate limiting
31127 engine can react in two possible ways, depending on the presence of the
31128 &%strict%& or &%leaky%& update modes. This is independent of the other
31129 counter-measures (such as rejecting the message) that may be specified by the
31130 rest of the ACL.
31131
31132 The &%leaky%& (default) option means that the client's recorded rate is not
31133 updated if it is above the limit. The effect of this is that Exim measures the
31134 client's average rate of successfully sent email,
31135 .new
31136 up to the given limit.
31137 This is appropriate if the countermeasure when the condition is true
31138 consists of refusing the message, and
31139 is generally the better choice if you have clients that retry automatically.
31140 If the action when true is anything more complex then this option is
31141 likely not what is wanted.
31142 .wen
31143
31144 The &%strict%& option means that the client's recorded rate is always
31145 updated. The effect of this is that Exim measures the client's average rate
31146 of attempts to send email, which can be much higher than the maximum it is
31147 actually allowed. If the client is over the limit it may be subjected to
31148 counter-measures by the ACL. It must slow down and allow sufficient time to
31149 pass that its computed rate falls below the maximum before it can send email
31150 again. The time (the number of smoothing periods) it must wait and not
31151 attempt to send mail can be calculated with this formula:
31152 .code
31153 ln(peakrate/maxrate)
31154 .endd
31155
31156
31157 .section "Limiting the rate of different events" "ratoptuniq"
31158 .cindex "rate limiting" "counting unique events"
31159 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
31160 rate of different events. For example, the &%per_addr%& option uses this
31161 mechanism to count the number of different recipients that the client has
31162 sent messages to in the last time period; it is equivalent to
31163 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
31164 measure the rate that a client uses different sender addresses with the
31165 options &`per_mail/unique=$sender_address`&.
31166
31167 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
31168 has seen for that key. The whole set is thrown away when it is older than the
31169 rate smoothing period &'p'&, so each different event is counted at most once
31170 per period. In the &%leaky%& update mode, an event that causes the client to
31171 go over the limit is not added to the set, in the same way that the client's
31172 recorded rate is not updated in the same situation.
31173
31174 When you combine the &%unique=%& and &%readonly%& options, the specific
31175 &%unique=%& value is ignored, and Exim just retrieves the client's stored
31176 rate.
31177
31178 The &%unique=%& mechanism needs more space in the ratelimit database than the
31179 other &%ratelimit%& options in order to store the event set. The number of
31180 unique values is potentially as large as the rate limit, so the extra space
31181 required increases with larger limits.
31182
31183 The uniqueification is not perfect: there is a small probability that Exim
31184 will think a new event has happened before. If the sender's rate is less than
31185 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
31186 the measured rate can go above the limit, in which case Exim may under-count
31187 events by a significant margin. Fortunately, if the rate is high enough (2.7
31188 times the limit) that the false positive rate goes above 9%, then Exim will
31189 throw away the over-full event set before the measured rate falls below the
31190 limit. Therefore the only harm should be that exceptionally high sending rates
31191 are logged incorrectly; any countermeasures you configure will be as effective
31192 as intended.
31193
31194
31195 .section "Using rate limiting" "useratlim"
31196 Exim's other ACL facilities are used to define what counter-measures are taken
31197 when the rate limit is exceeded. This might be anything from logging a warning
31198 (for example, while measuring existing sending rates in order to define
31199 policy), through time delays to slow down fast senders, up to rejecting the
31200 message. For example:
31201 .code
31202 # Log all senders' rates
31203 warn ratelimit = 0 / 1h / strict
31204 log_message = Sender rate $sender_rate / $sender_rate_period
31205
31206 # Slow down fast senders; note the need to truncate $sender_rate
31207 # at the decimal point.
31208 warn ratelimit = 100 / 1h / per_rcpt / strict
31209 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
31210 $sender_rate_limit }s
31211
31212 # Keep authenticated users under control
31213 deny authenticated = *
31214 ratelimit = 100 / 1d / strict / $authenticated_id
31215
31216 # System-wide rate limit
31217 defer message = Sorry, too busy. Try again later.
31218 ratelimit = 10 / 1s / $primary_hostname
31219
31220 # Restrict incoming rate from each host, with a default
31221 # set using a macro and special cases looked up in a table.
31222 defer message = Sender rate exceeds $sender_rate_limit \
31223 messages per $sender_rate_period
31224 ratelimit = ${lookup {$sender_host_address} \
31225 cdb {DB/ratelimits.cdb} \
31226 {$value} {RATELIMIT} }
31227 .endd
31228 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
31229 especially with the &%per_rcpt%& option, you may suffer from a performance
31230 bottleneck caused by locking on the ratelimit hints database. Apart from
31231 making your ACLs less complicated, you can reduce the problem by using a
31232 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
31233 this means that Exim will lose its hints data after a reboot (including retry
31234 hints, the callout cache, and ratelimit data).
31235
31236
31237
31238 .section "Address verification" "SECTaddressverification"
31239 .cindex "verifying address" "options for"
31240 .cindex "policy control" "address verification"
31241 Several of the &%verify%& conditions described in section
31242 &<<SECTaclconditions>>& cause addresses to be verified. Section
31243 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
31244 The verification conditions can be followed by options that modify the
31245 verification process. The options are separated from the keyword and from each
31246 other by slashes, and some of them contain parameters. For example:
31247 .code
31248 verify = sender/callout
31249 verify = recipient/defer_ok/callout=10s,defer_ok
31250 .endd
31251 The first stage of address verification, which always happens, is to run the
31252 address through the routers, in &"verify mode"&. Routers can detect the
31253 difference between verification and routing for delivery, and their actions can
31254 be varied by a number of generic options such as &%verify%& and &%verify_only%&
31255 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
31256 The available options are as follows:
31257
31258 .ilist
31259 If the &%callout%& option is specified, successful routing to one or more
31260 remote hosts is followed by a &"callout"& to those hosts as an additional
31261 check. Callouts and their sub-options are discussed in the next section.
31262 .next
31263 If there is a defer error while doing verification routing, the ACL
31264 normally returns &"defer"&. However, if you include &%defer_ok%& in the
31265 options, the condition is forced to be true instead. Note that this is a main
31266 verification option as well as a suboption for callouts.
31267 .next
31268 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
31269 discusses the reporting of sender address verification failures.
31270 .next
31271 The &%success_on_redirect%& option causes verification always to succeed
31272 immediately after a successful redirection. By default, if a redirection
31273 generates just one address, that address is also verified. See further
31274 discussion in section &<<SECTredirwhilveri>>&.
31275 .endlist
31276
31277 .cindex "verifying address" "differentiating failures"
31278 .vindex "&$recipient_verify_failure$&"
31279 .vindex "&$sender_verify_failure$&"
31280 .vindex "&$acl_verify_message$&"
31281 After an address verification failure, &$acl_verify_message$& contains the
31282 error message that is associated with the failure. It can be preserved by
31283 coding like this:
31284 .code
31285 warn !verify = sender
31286 set acl_m0 = $acl_verify_message
31287 .endd
31288 If you are writing your own custom rejection message or log message when
31289 denying access, you can use this variable to include information about the
31290 verification failure.
31291
31292 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
31293 appropriate) contains one of the following words:
31294
31295 .ilist
31296 &%qualify%&: The address was unqualified (no domain), and the message
31297 was neither local nor came from an exempted host.
31298 .next
31299 &%route%&: Routing failed.
31300 .next
31301 &%mail%&: Routing succeeded, and a callout was attempted; rejection
31302 occurred at or before the MAIL command (that is, on initial
31303 connection, HELO, or MAIL).
31304 .next
31305 &%recipient%&: The RCPT command in a callout was rejected.
31306 .next
31307 &%postmaster%&: The postmaster check in a callout was rejected.
31308 .endlist
31309
31310 The main use of these variables is expected to be to distinguish between
31311 rejections of MAIL and rejections of RCPT in callouts.
31312
31313 .new
31314 The above variables may also be set after a &*successful*&
31315 address verification to:
31316
31317 .ilist
31318 &%random%&: A random local-part callout succeeded
31319 .endlist
31320 .wen
31321
31322
31323
31324
31325 .section "Callout verification" "SECTcallver"
31326 .cindex "verifying address" "by callout"
31327 .cindex "callout" "verification"
31328 .cindex "SMTP" "callout verification"
31329 For non-local addresses, routing verifies the domain, but is unable to do any
31330 checking of the local part. There are situations where some means of verifying
31331 the local part is desirable. One way this can be done is to make an SMTP
31332 &'callback'& to a delivery host for the sender address or a &'callforward'& to
31333 a subsequent host for a recipient address, to see if the host accepts the
31334 address. We use the term &'callout'& to cover both cases. Note that for a
31335 sender address, the callback is not to the client host that is trying to
31336 deliver the message, but to one of the hosts that accepts incoming mail for the
31337 sender's domain.
31338
31339 Exim does not do callouts by default. If you want them to happen, you must
31340 request them by setting appropriate options on the &%verify%& condition, as
31341 described below. This facility should be used with care, because it can add a
31342 lot of resource usage to the cost of verifying an address. However, Exim does
31343 cache the results of callouts, which helps to reduce the cost. Details of
31344 caching are in section &<<SECTcallvercache>>&.
31345
31346 Recipient callouts are usually used only between hosts that are controlled by
31347 the same administration. For example, a corporate gateway host could use
31348 callouts to check for valid recipients on an internal mailserver. A successful
31349 callout does not guarantee that a real delivery to the address would succeed;
31350 on the other hand, a failing callout does guarantee that a delivery would fail.
31351
31352 If the &%callout%& option is present on a condition that verifies an address, a
31353 second stage of verification occurs if the address is successfully routed to
31354 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
31355 &(manualroute)& router, where the router specifies the hosts. However, if a
31356 router that does not set up hosts routes to an &(smtp)& transport with a
31357 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
31358 &%hosts_override%& set, its hosts are always used, whether or not the router
31359 supplies a host list.
31360 Callouts are only supported on &(smtp)& transports.
31361
31362 The port that is used is taken from the transport, if it is specified and is a
31363 remote transport. (For routers that do verification only, no transport need be
31364 specified.) Otherwise, the default SMTP port is used. If a remote transport
31365 specifies an outgoing interface, this is used; otherwise the interface is not
31366 specified. Likewise, the text that is used for the HELO command is taken from
31367 the transport's &%helo_data%& option; if there is no transport, the value of
31368 &$smtp_active_hostname$& is used.
31369
31370 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
31371 test whether a bounce message could be delivered to the sender address. The
31372 following SMTP commands are sent:
31373 .display
31374 &`HELO `&<&'local host name'&>
31375 &`MAIL FROM:<>`&
31376 &`RCPT TO:`&<&'the address to be tested'&>
31377 &`QUIT`&
31378 .endd
31379 LHLO is used instead of HELO if the transport's &%protocol%& option is
31380 set to &"lmtp"&.
31381
31382 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
31383 settings.
31384
31385 A recipient callout check is similar. By default, it also uses an empty address
31386 for the sender. This default is chosen because most hosts do not make use of
31387 the sender address when verifying a recipient. Using the same address means
31388 that a single cache entry can be used for each recipient. Some sites, however,
31389 do make use of the sender address when verifying. These are catered for by the
31390 &%use_sender%& and &%use_postmaster%& options, described in the next section.
31391
31392 If the response to the RCPT command is a 2&'xx'& code, the verification
31393 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
31394 Exim tries the next host, if any. If there is a problem with all the remote
31395 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
31396 &%callout%& option is given, in which case the condition is forced to succeed.
31397
31398 .cindex "SMTP" "output flushing, disabling for callout"
31399 A callout may take a little time. For this reason, Exim normally flushes SMTP
31400 output before performing a callout in an ACL, to avoid unexpected timeouts in
31401 clients when the SMTP PIPELINING extension is in use. The flushing can be
31402 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
31403
31404
31405
31406
31407 .section "Additional parameters for callouts" "CALLaddparcall"
31408 .cindex "callout" "additional parameters for"
31409 The &%callout%& option can be followed by an equals sign and a number of
31410 optional parameters, separated by commas. For example:
31411 .code
31412 verify = recipient/callout=10s,defer_ok
31413 .endd
31414 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
31415 separate verify options, is retained for backwards compatibility, but is now
31416 deprecated. The additional parameters for &%callout%& are as follows:
31417
31418
31419 .vlist
31420 .vitem <&'a&~time&~interval'&>
31421 .cindex "callout" "timeout, specifying"
31422 This specifies the timeout that applies for the callout attempt to each host.
31423 For example:
31424 .code
31425 verify = sender/callout=5s
31426 .endd
31427 The default is 30 seconds. The timeout is used for each response from the
31428 remote host. It is also used for the initial connection, unless overridden by
31429 the &%connect%& parameter.
31430
31431
31432 .vitem &*connect&~=&~*&<&'time&~interval'&>
31433 .cindex "callout" "connection timeout, specifying"
31434 This parameter makes it possible to set a different (usually smaller) timeout
31435 for making the SMTP connection. For example:
31436 .code
31437 verify = sender/callout=5s,connect=1s
31438 .endd
31439 If not specified, this timeout defaults to the general timeout value.
31440
31441 .vitem &*defer_ok*&
31442 .cindex "callout" "defer, action on"
31443 When this parameter is present, failure to contact any host, or any other kind
31444 of temporary error, is treated as success by the ACL. However, the cache is not
31445 updated in this circumstance.
31446
31447 .vitem &*fullpostmaster*&
31448 .cindex "callout" "full postmaster check"
31449 This operates like the &%postmaster%& option (see below), but if the check for
31450 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
31451 accordance with the specification in RFC 2821. The RFC states that the
31452 unqualified address &'postmaster'& should be accepted.
31453
31454
31455 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
31456 .cindex "callout" "sender when verifying header"
31457 When verifying addresses in header lines using the &%header_sender%&
31458 verification option, Exim behaves by default as if the addresses are envelope
31459 sender addresses from a message. Callout verification therefore tests to see
31460 whether a bounce message could be delivered, by using an empty address in the
31461 MAIL command. However, it is arguable that these addresses might never be used
31462 as envelope senders, and could therefore justifiably reject bounce messages
31463 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
31464 address to use in the MAIL command. For example:
31465 .code
31466 require verify = header_sender/callout=mailfrom=abcd@x.y.z
31467 .endd
31468 This parameter is available only for the &%header_sender%& verification option.
31469
31470
31471 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
31472 .cindex "callout" "overall timeout, specifying"
31473 This parameter sets an overall timeout for performing a callout verification.
31474 For example:
31475 .code
31476 verify = sender/callout=5s,maxwait=30s
31477 .endd
31478 This timeout defaults to four times the callout timeout for individual SMTP
31479 commands. The overall timeout applies when there is more than one host that can
31480 be tried. The timeout is checked before trying the next host. This prevents
31481 very long delays if there are a large number of hosts and all are timing out
31482 (for example, when network connections are timing out).
31483
31484
31485 .vitem &*no_cache*&
31486 .cindex "callout" "cache, suppressing"
31487 .cindex "caching callout, suppressing"
31488 When this parameter is given, the callout cache is neither read nor updated.
31489
31490 .vitem &*postmaster*&
31491 .cindex "callout" "postmaster; checking"
31492 When this parameter is set, a successful callout check is followed by a similar
31493 check for the local part &'postmaster'& at the same domain. If this address is
31494 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
31495 the postmaster check is recorded in a cache record; if it is a failure, this is
31496 used to fail subsequent callouts for the domain without a connection being
31497 made, until the cache record expires.
31498
31499 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
31500 The postmaster check uses an empty sender in the MAIL command by default.
31501 You can use this parameter to do a postmaster check using a different address.
31502 For example:
31503 .code
31504 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
31505 .endd
31506 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
31507 one overrides. The &%postmaster%& parameter is equivalent to this example:
31508 .code
31509 require verify = sender/callout=postmaster_mailfrom=
31510 .endd
31511 &*Warning*&: The caching arrangements for postmaster checking do not take
31512 account of the sender address. It is assumed that either the empty address or
31513 a fixed non-empty address will be used. All that Exim remembers is that the
31514 postmaster check for the domain succeeded or failed.
31515
31516
31517 .vitem &*random*&
31518 .cindex "callout" "&""random""& check"
31519 When this parameter is set, before doing the normal callout check, Exim does a
31520 check for a &"random"& local part at the same domain. The local part is not
31521 really random &-- it is defined by the expansion of the option
31522 &%callout_random_local_part%&, which defaults to
31523 .code
31524 $primary_hostname-$tod_epoch-testing
31525 .endd
31526 The idea here is to try to determine whether the remote host accepts all local
31527 parts without checking. If it does, there is no point in doing callouts for
31528 specific local parts. If the &"random"& check succeeds, the result is saved in
31529 a cache record, and used to force the current and subsequent callout checks to
31530 succeed without a connection being made, until the cache record expires.
31531
31532 .vitem &*use_postmaster*&
31533 .cindex "callout" "sender for recipient check"
31534 This parameter applies to recipient callouts only. For example:
31535 .code
31536 deny !verify = recipient/callout=use_postmaster
31537 .endd
31538 .vindex "&$qualify_domain$&"
31539 It causes a non-empty postmaster address to be used in the MAIL command when
31540 performing the callout for the recipient, and also for a &"random"& check if
31541 that is configured. The local part of the address is &`postmaster`& and the
31542 domain is the contents of &$qualify_domain$&.
31543
31544 .vitem &*use_sender*&
31545 This option applies to recipient callouts only. For example:
31546 .code
31547 require verify = recipient/callout=use_sender
31548 .endd
31549 It causes the message's actual sender address to be used in the MAIL
31550 command when performing the callout, instead of an empty address. There is no
31551 need to use this option unless you know that the called hosts make use of the
31552 sender when checking recipients. If used indiscriminately, it reduces the
31553 usefulness of callout caching.
31554
31555 .vitem &*hold*&
31556 This option applies to recipient callouts only. For example:
31557 .code
31558 require verify = recipient/callout=use_sender,hold
31559 .endd
31560 It causes the connection to be held open and used for any further recipients
31561 and for eventual delivery (should that be done quickly).
31562 Doing this saves on TCP and SMTP startup costs, and TLS costs also
31563 when that is used for the connections.
31564 The advantage is only gained if there are no callout cache hits
31565 (which could be enforced by the no_cache option),
31566 if the use_sender option is used,
31567 if neither the random nor the use_postmaster option is used,
31568 and if no other callouts intervene.
31569 .endlist
31570
31571 If you use any of the parameters that set a non-empty sender for the MAIL
31572 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
31573 &%use_sender%&), you should think about possible loops. Recipient checking is
31574 usually done between two hosts that are under the same management, and the host
31575 that receives the callouts is not normally configured to do callouts itself.
31576 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
31577 these circumstances.
31578
31579 However, if you use a non-empty sender address for a callout to an arbitrary
31580 host, there is the likelihood that the remote host will itself initiate a
31581 callout check back to your host. As it is checking what appears to be a message
31582 sender, it is likely to use an empty address in MAIL, thus avoiding a
31583 callout loop. However, to be on the safe side it would be best to set up your
31584 own ACLs so that they do not do sender verification checks when the recipient
31585 is the address you use for header sender or postmaster callout checking.
31586
31587 Another issue to think about when using non-empty senders for callouts is
31588 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
31589 by the sender/recipient combination; thus, for any given recipient, many more
31590 actual callouts are performed than when an empty sender or postmaster is used.
31591
31592
31593
31594
31595 .section "Callout caching" "SECTcallvercache"
31596 .cindex "hints database" "callout cache"
31597 .cindex "callout" "cache, description of"
31598 .cindex "caching" "callout"
31599 Exim caches the results of callouts in order to reduce the amount of resources
31600 used, unless you specify the &%no_cache%& parameter with the &%callout%&
31601 option. A hints database called &"callout"& is used for the cache. Two
31602 different record types are used: one records the result of a callout check for
31603 a specific address, and the other records information that applies to the
31604 entire domain (for example, that it accepts the local part &'postmaster'&).
31605
31606 When an original callout fails, a detailed SMTP error message is given about
31607 the failure. However, for subsequent failures use the cache data, this message
31608 is not available.
31609
31610 The expiry times for negative and positive address cache records are
31611 independent, and can be set by the global options &%callout_negative_expire%&
31612 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
31613
31614 If a host gives a negative response to an SMTP connection, or rejects any
31615 commands up to and including
31616 .code
31617 MAIL FROM:<>
31618 .endd
31619 (but not including the MAIL command with a non-empty address),
31620 any callout attempt is bound to fail. Exim remembers such failures in a
31621 domain cache record, which it uses to fail callouts for the domain without
31622 making new connections, until the domain record times out. There are two
31623 separate expiry times for domain cache records:
31624 &%callout_domain_negative_expire%& (default 3h) and
31625 &%callout_domain_positive_expire%& (default 7d).
31626
31627 Domain records expire when the negative expiry time is reached if callouts
31628 cannot be made for the domain, or if the postmaster check failed.
31629 Otherwise, they expire when the positive expiry time is reached. This
31630 ensures that, for example, a host that stops accepting &"random"& local parts
31631 will eventually be noticed.
31632
31633 The callout caching mechanism is based on the domain of the address that is
31634 being tested. If the domain routes to several hosts, it is assumed that their
31635 behaviour will be the same.
31636
31637
31638
31639 .section "Sender address verification reporting" "SECTsenaddver"
31640 .cindex "verifying" "suppressing error details"
31641 See section &<<SECTaddressverification>>& for a general discussion of
31642 verification. When sender verification fails in an ACL, the details of the
31643 failure are given as additional output lines before the 550 response to the
31644 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
31645 you might see:
31646 .code
31647 MAIL FROM:<xyz@abc.example>
31648 250 OK
31649 RCPT TO:<pqr@def.example>
31650 550-Verification failed for <xyz@abc.example>
31651 550-Called: 192.168.34.43
31652 550-Sent: RCPT TO:<xyz@abc.example>
31653 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
31654 550 Sender verification failed
31655 .endd
31656 If more than one RCPT command fails in the same way, the details are given
31657 only for the first of them. However, some administrators do not want to send
31658 out this much information. You can suppress the details by adding
31659 &`/no_details`& to the ACL statement that requests sender verification. For
31660 example:
31661 .code
31662 verify = sender/no_details
31663 .endd
31664
31665 .section "Redirection while verifying" "SECTredirwhilveri"
31666 .cindex "verifying" "redirection while"
31667 .cindex "address redirection" "while verifying"
31668 A dilemma arises when a local address is redirected by aliasing or forwarding
31669 during verification: should the generated addresses themselves be verified,
31670 or should the successful expansion of the original address be enough to verify
31671 it? By default, Exim takes the following pragmatic approach:
31672
31673 .ilist
31674 When an incoming address is redirected to just one child address, verification
31675 continues with the child address, and if that fails to verify, the original
31676 verification also fails.
31677 .next
31678 When an incoming address is redirected to more than one child address,
31679 verification does not continue. A success result is returned.
31680 .endlist
31681
31682 This seems the most reasonable behaviour for the common use of aliasing as a
31683 way of redirecting different local parts to the same mailbox. It means, for
31684 example, that a pair of alias entries of the form
31685 .code
31686 A.Wol: aw123
31687 aw123: :fail: Gone away, no forwarding address
31688 .endd
31689 work as expected, with both local parts causing verification failure. When a
31690 redirection generates more than one address, the behaviour is more like a
31691 mailing list, where the existence of the alias itself is sufficient for
31692 verification to succeed.
31693
31694 It is possible, however, to change the default behaviour so that all successful
31695 redirections count as successful verifications, however many new addresses are
31696 generated. This is specified by the &%success_on_redirect%& verification
31697 option. For example:
31698 .code
31699 require verify = recipient/success_on_redirect/callout=10s
31700 .endd
31701 In this example, verification succeeds if a router generates a new address, and
31702 the callout does not occur, because no address was routed to a remote host.
31703
31704 When verification is being tested via the &%-bv%& option, the treatment of
31705 redirections is as just described, unless the &%-v%& or any debugging option is
31706 also specified. In that case, full verification is done for every generated
31707 address and a report is output for each of them.
31708
31709
31710
31711 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
31712 .cindex "CSA" "verifying"
31713 Client SMTP Authorization is a system that allows a site to advertise
31714 which machines are and are not permitted to send email. This is done by placing
31715 special SRV records in the DNS; these are looked up using the client's HELO
31716 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
31717 Authorization checks in Exim are performed by the ACL condition:
31718 .code
31719 verify = csa
31720 .endd
31721 This fails if the client is not authorized. If there is a DNS problem, or if no
31722 valid CSA SRV record is found, or if the client is authorized, the condition
31723 succeeds. These three cases can be distinguished using the expansion variable
31724 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
31725 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
31726 be likely to cause problems for legitimate email.
31727
31728 The error messages produced by the CSA code include slightly more
31729 detail. If &$csa_status$& is &"defer"&, this may be because of problems
31730 looking up the CSA SRV record, or problems looking up the CSA target
31731 address record. There are four reasons for &$csa_status$& being &"fail"&:
31732
31733 .ilist
31734 The client's host name is explicitly not authorized.
31735 .next
31736 The client's IP address does not match any of the CSA target IP addresses.
31737 .next
31738 The client's host name is authorized but it has no valid target IP addresses
31739 (for example, the target's addresses are IPv6 and the client is using IPv4).
31740 .next
31741 The client's host name has no CSA SRV record but a parent domain has asserted
31742 that all subdomains must be explicitly authorized.
31743 .endlist
31744
31745 The &%csa%& verification condition can take an argument which is the domain to
31746 use for the DNS query. The default is:
31747 .code
31748 verify = csa/$sender_helo_name
31749 .endd
31750 This implementation includes an extension to CSA. If the query domain
31751 is an address literal such as [192.0.2.95], or if it is a bare IP
31752 address, Exim searches for CSA SRV records in the reverse DNS as if
31753 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
31754 meaningful to say:
31755 .code
31756 verify = csa/$sender_host_address
31757 .endd
31758 In fact, this is the check that Exim performs if the client does not say HELO.
31759 This extension can be turned off by setting the main configuration option
31760 &%dns_csa_use_reverse%& to be false.
31761
31762 If a CSA SRV record is not found for the domain itself, a search
31763 is performed through its parent domains for a record which might be
31764 making assertions about subdomains. The maximum depth of this search is limited
31765 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
31766 default. Exim does not look for CSA SRV records in a top level domain, so the
31767 default settings handle HELO domains as long as seven
31768 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
31769 of legitimate HELO domains.
31770
31771 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
31772 direct SRV lookups, this is not sufficient because of the extra parent domain
31773 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
31774 addresses into lookups in the reverse DNS space. The result of a successful
31775 lookup such as:
31776 .code
31777 ${lookup dnsdb {csa=$sender_helo_name}}
31778 .endd
31779 has two space-separated fields: an authorization code and a target host name.
31780 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
31781 authorization required but absent, or &"?"& for unknown.
31782
31783
31784
31785
31786 .section "Bounce address tag validation" "SECTverifyPRVS"
31787 .cindex "BATV, verifying"
31788 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
31789 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
31790 Genuine incoming bounce messages should therefore always be addressed to
31791 recipients that have a valid tag. This scheme is a way of detecting unwanted
31792 bounce messages caused by sender address forgeries (often called &"collateral
31793 spam"&), because the recipients of such messages do not include valid tags.
31794
31795 There are two expansion items to help with the implementation of the BATV
31796 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
31797 the original envelope sender address by using a simple key to add a hash of the
31798 address and some time-based randomizing information. The &%prvs%& expansion
31799 item creates a signed address, and the &%prvscheck%& expansion item checks one.
31800 The syntax of these expansion items is described in section
31801 &<<SECTexpansionitems>>&.
31802 The validity period on signed addresses is seven days.
31803
31804 As an example, suppose the secret per-address keys are stored in an MySQL
31805 database. A query to look up the key for an address could be defined as a macro
31806 like this:
31807 .code
31808 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
31809 WHERE sender='${quote_mysql:$prvscheck_address}'\
31810 }{$value}}
31811 .endd
31812 Suppose also that the senders who make use of BATV are defined by an address
31813 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
31814 use this:
31815 .code
31816 # Bounces: drop unsigned addresses for BATV senders
31817 deny message = This address does not send an unsigned reverse path
31818 senders = :
31819 recipients = +batv_senders
31820
31821 # Bounces: In case of prvs-signed address, check signature.
31822 deny message = Invalid reverse path signature.
31823 senders = :
31824 condition = ${prvscheck {$local_part@$domain}\
31825 {PRVSCHECK_SQL}{1}}
31826 !condition = $prvscheck_result
31827 .endd
31828 The first statement rejects recipients for bounce messages that are addressed
31829 to plain BATV sender addresses, because it is known that BATV senders do not
31830 send out messages with plain sender addresses. The second statement rejects
31831 recipients that are prvs-signed, but with invalid signatures (either because
31832 the key is wrong, or the signature has timed out).
31833
31834 A non-prvs-signed address is not rejected by the second statement, because the
31835 &%prvscheck%& expansion yields an empty string if its first argument is not a
31836 prvs-signed address, thus causing the &%condition%& condition to be false. If
31837 the first argument is a syntactically valid prvs-signed address, the yield is
31838 the third string (in this case &"1"&), whether or not the cryptographic and
31839 timeout checks succeed. The &$prvscheck_result$& variable contains the result
31840 of the checks (empty for failure, &"1"& for success).
31841
31842 There is one more issue you must consider when implementing prvs-signing:
31843 you have to ensure that the routers accept prvs-signed addresses and
31844 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
31845 router to remove the signature with a configuration along these lines:
31846 .code
31847 batv_redirect:
31848 driver = redirect
31849 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
31850 .endd
31851 This works because, if the third argument of &%prvscheck%& is empty, the result
31852 of the expansion of a prvs-signed address is the decoded value of the original
31853 address. This router should probably be the first of your routers that handles
31854 local addresses.
31855
31856 To create BATV-signed addresses in the first place, a transport of this form
31857 can be used:
31858 .code
31859 external_smtp_batv:
31860 driver = smtp
31861 return_path = ${prvs {$return_path} \
31862 {${lookup mysql{SELECT \
31863 secret FROM batv_prvs WHERE \
31864 sender='${quote_mysql:$sender_address}'} \
31865 {$value}fail}}}
31866 .endd
31867 If no key can be found for the existing return path, no signing takes place.
31868
31869
31870
31871 .section "Using an ACL to control relaying" "SECTrelaycontrol"
31872 .cindex "&ACL;" "relay control"
31873 .cindex "relaying" "control by ACL"
31874 .cindex "policy control" "relay control"
31875 An MTA is said to &'relay'& a message if it receives it from some host and
31876 delivers it directly to another host as a result of a remote address contained
31877 within it. Redirecting a local address via an alias or forward file and then
31878 passing the message on to another host is not relaying,
31879 .cindex "&""percent hack""&"
31880 but a redirection as a result of the &"percent hack"& is.
31881
31882 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
31883 A host which is acting as a gateway or an MX backup is concerned with incoming
31884 relaying from arbitrary hosts to a specific set of domains. On the other hand,
31885 a host which is acting as a smart host for a number of clients is concerned
31886 with outgoing relaying from those clients to the Internet at large. Often the
31887 same host is fulfilling both functions,
31888 . ///
31889 . as illustrated in the diagram below,
31890 . ///
31891 but in principle these two kinds of relaying are entirely independent. What is
31892 not wanted is the transmission of mail from arbitrary remote hosts through your
31893 system to arbitrary domains.
31894
31895
31896 You can implement relay control by means of suitable statements in the ACL that
31897 runs for each RCPT command. For convenience, it is often easiest to use
31898 Exim's named list facility to define the domains and hosts involved. For
31899 example, suppose you want to do the following:
31900
31901 .ilist
31902 Deliver a number of domains to mailboxes on the local host (or process them
31903 locally in some other way). Let's say these are &'my.dom1.example'& and
31904 &'my.dom2.example'&.
31905 .next
31906 Relay mail for a number of other domains for which you are the secondary MX.
31907 These might be &'friend1.example'& and &'friend2.example'&.
31908 .next
31909 Relay mail from the hosts on your local LAN, to whatever domains are involved.
31910 Suppose your LAN is 192.168.45.0/24.
31911 .endlist
31912
31913
31914 In the main part of the configuration, you put the following definitions:
31915 .code
31916 domainlist local_domains = my.dom1.example : my.dom2.example
31917 domainlist relay_to_domains = friend1.example : friend2.example
31918 hostlist relay_from_hosts = 192.168.45.0/24
31919 .endd
31920 Now you can use these definitions in the ACL that is run for every RCPT
31921 command:
31922 .code
31923 acl_check_rcpt:
31924 accept domains = +local_domains : +relay_to_domains
31925 accept hosts = +relay_from_hosts
31926 .endd
31927 The first statement accepts any RCPT command that contains an address in
31928 the local or relay domains. For any other domain, control passes to the second
31929 statement, which accepts the command only if it comes from one of the relay
31930 hosts. In practice, you will probably want to make your ACL more sophisticated
31931 than this, for example, by including sender and recipient verification. The
31932 default configuration includes a more comprehensive example, which is described
31933 in chapter &<<CHAPdefconfil>>&.
31934
31935
31936
31937 .section "Checking a relay configuration" "SECTcheralcon"
31938 .cindex "relaying" "checking control of"
31939 You can check the relay characteristics of your configuration in the same way
31940 that you can test any ACL behaviour for an incoming SMTP connection, by using
31941 the &%-bh%& option to run a fake SMTP session with which you interact.
31942 .ecindex IIDacl
31943
31944
31945
31946 . ////////////////////////////////////////////////////////////////////////////
31947 . ////////////////////////////////////////////////////////////////////////////
31948
31949 .chapter "Content scanning at ACL time" "CHAPexiscan"
31950 .scindex IIDcosca "content scanning" "at ACL time"
31951 The extension of Exim to include content scanning at ACL time, formerly known
31952 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
31953 was integrated into the main source for Exim release 4.50, and Tom continues to
31954 maintain it. Most of the wording of this chapter is taken from Tom's
31955 specification.
31956
31957 It is also possible to scan the content of messages at other times. The
31958 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
31959 scanning after all the ACLs have run. A transport filter can be used to scan
31960 messages at delivery time (see the &%transport_filter%& option, described in
31961 chapter &<<CHAPtransportgeneric>>&).
31962
31963 If you want to include the ACL-time content-scanning features when you compile
31964 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
31965 &_Local/Makefile_&. When you do that, the Exim binary is built with:
31966
31967 .ilist
31968 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
31969 for all MIME parts for SMTP and non-SMTP messages, respectively.
31970 .next
31971 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
31972 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
31973 run at the end of message reception (the &%acl_smtp_data%& ACL).
31974 .next
31975 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
31976 of messages, or parts of messages, for debugging purposes.
31977 .next
31978 Additional expansion variables that are set in the new ACL and by the new
31979 conditions.
31980 .next
31981 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
31982 .endlist
31983
31984 Content-scanning is continually evolving, and new features are still being
31985 added. While such features are still unstable and liable to incompatible
31986 changes, they are made available in Exim by setting options whose names begin
31987 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
31988 this manual. You can find out about them by reading the file called
31989 &_doc/experimental.txt_&.
31990
31991 All the content-scanning facilities work on a MBOX copy of the message that is
31992 temporarily created in a file called:
31993 .display
31994 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
31995 .endd
31996 The &_.eml_& extension is a friendly hint to virus scanners that they can
31997 expect an MBOX-like structure inside that file. The file is created when the
31998 first content scanning facility is called. Subsequent calls to content
31999 scanning conditions open the same file again. The directory is recursively
32000 removed when the &%acl_smtp_data%& ACL has finished running, unless
32001 .code
32002 control = no_mbox_unspool
32003 .endd
32004 has been encountered. When the MIME ACL decodes files, they are put into the
32005 same directory by default.
32006
32007
32008
32009 .section "Scanning for viruses" "SECTscanvirus"
32010 .cindex "virus scanning"
32011 .cindex "content scanning" "for viruses"
32012 .cindex "content scanning" "the &%malware%& condition"
32013 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
32014 It supports a &"generic"& interface to scanners called via the shell, and
32015 specialized interfaces for &"daemon"& type virus scanners, which are resident
32016 in memory and thus are much faster.
32017
32018 A timeout of 2 minutes is applied to a scanner call (by default);
32019 if it expires then a defer action is taken.
32020
32021 .oindex "&%av_scanner%&"
32022 You can set the &%av_scanner%& option in the main part of the configuration
32023 to specify which scanner to use, together with any additional options that
32024 are needed. The basic syntax is as follows:
32025 .display
32026 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
32027 .endd
32028 If you do not set &%av_scanner%&, it defaults to
32029 .code
32030 av_scanner = sophie:/var/run/sophie
32031 .endd
32032 If the value of &%av_scanner%& starts with a dollar character, it is expanded
32033 before use.
32034 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
32035 The following scanner types are supported in this release,
32036 though individual ones can be included or not at build time:
32037
32038 .vlist
32039 .vitem &%avast%&
32040 .cindex "virus scanners" "avast"
32041 This is the scanner daemon of Avast. It has been tested with Avast Core
32042 Security (currently at version 2.2.0).
32043 You can get a trial version at &url(https://www.avast.com) or for Linux
32044 at &url(https://www.avast.com/linux-server-antivirus).
32045 This scanner type takes one option,
32046 which can be either a full path to a UNIX socket,
32047 or host and port specifiers separated by white space.
32048 The host may be a name or an IP address; the port is either a
32049 single number or a pair of numbers with a dash between.
32050 A list of options may follow. These options are interpreted on the
32051 Exim's side of the malware scanner, or are given on separate lines to
32052 the daemon as options before the main scan command.
32053
32054 .cindex &`pass_unscanned`& "avast"
32055 If &`pass_unscanned`&
32056 is set, any files the Avast scanner can't scan (e.g.
32057 decompression bombs, or invalid archives) are considered clean. Use with
32058 care.
32059
32060 For example:
32061 .code
32062 av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
32063 av_scanner = avast:/var/run/avast/scan.sock:pass_unscanned:FLAGS -fullfiles:SENSITIVITY -pup
32064 av_scanner = avast:192.168.2.22 5036
32065 .endd
32066 If you omit the argument, the default path
32067 &_/var/run/avast/scan.sock_&
32068 is used.
32069 If you use a remote host,
32070 you need to make Exim's spool directory available to it,
32071 as the scanner is passed a file path, not file contents.
32072 For information about available commands and their options you may use
32073 .code
32074 $ socat UNIX:/var/run/avast/scan.sock STDIO:
32075 FLAGS
32076 SENSITIVITY
32077 PACK
32078 .endd
32079
32080 If the scanner returns a temporary failure (e.g. license issues, or
32081 permission problems), the message is deferred and a paniclog entry is
32082 written. The usual &`defer_ok`& option is available.
32083
32084 .vitem &%aveserver%&
32085 .cindex "virus scanners" "Kaspersky"
32086 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
32087 at &url(http://www.kaspersky.com). This scanner type takes one option,
32088 which is the path to the daemon's UNIX socket. The default is shown in this
32089 example:
32090 .code
32091 av_scanner = aveserver:/var/run/aveserver
32092 .endd
32093
32094
32095 .vitem &%clamd%&
32096 .cindex "virus scanners" "clamd"
32097 This daemon-type scanner is GPL and free. You can get it at
32098 &url(http://www.clamav.net/). Some older versions of clamd do not seem to
32099 unpack MIME containers, so it used to be recommended to unpack MIME attachments
32100 in the MIME ACL. This is no longer believed to be necessary.
32101
32102 The options are a list of server specifiers, which may be
32103 a UNIX socket specification,
32104 a TCP socket specification,
32105 or a (global) option.
32106
32107 A socket specification consists of a space-separated list.
32108 For a Unix socket the first element is a full path for the socket,
32109 for a TCP socket the first element is the IP address
32110 and the second a port number,
32111 Any further elements are per-server (non-global) options.
32112 These per-server options are supported:
32113 .code
32114 retry=<timespec> Retry on connect fail
32115 .endd
32116
32117 The &`retry`& option specifies a time after which a single retry for
32118 a failed connect is made. The default is to not retry.
32119
32120 If a Unix socket file is specified, only one server is supported.
32121
32122 Examples:
32123 .code
32124 av_scanner = clamd:/opt/clamd/socket
32125 av_scanner = clamd:192.0.2.3 1234
32126 av_scanner = clamd:192.0.2.3 1234:local
32127 av_scanner = clamd:192.0.2.3 1234 retry=10s
32128 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
32129 .endd
32130 If the value of av_scanner points to a UNIX socket file or contains the
32131 &`local`&
32132 option, then the ClamAV interface will pass a filename containing the data
32133 to be scanned, which should normally result in less I/O happening and be
32134 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
32135 Exim does not assume that there is a common filesystem with the remote host.
32136
32137 The final example shows that multiple TCP targets can be specified. Exim will
32138 randomly use one for each incoming email (i.e. it load balances them). Note
32139 that only TCP targets may be used if specifying a list of scanners; a UNIX
32140 socket cannot be mixed in with TCP targets. If one of the servers becomes
32141 unavailable, Exim will try the remaining one(s) until it finds one that works.
32142 When a clamd server becomes unreachable, Exim will log a message. Exim does
32143 not keep track of scanner state between multiple messages, and the scanner
32144 selection is random, so the message will get logged in the mainlog for each
32145 email that the down scanner gets chosen first (message wrapped to be readable):
32146 .code
32147 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
32148 clamd: connection to localhost, port 3310 failed
32149 (Connection refused)
32150 .endd
32151
32152 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
32153 contributing the code for this scanner.
32154
32155 .vitem &%cmdline%&
32156 .cindex "virus scanners" "command line interface"
32157 This is the keyword for the generic command line scanner interface. It can be
32158 used to attach virus scanners that are invoked from the shell. This scanner
32159 type takes 3 mandatory options:
32160
32161 .olist
32162 The full path and name of the scanner binary, with all command line options,
32163 and a placeholder (&`%s`&) for the directory to scan.
32164
32165 .next
32166 A regular expression to match against the STDOUT and STDERR output of the
32167 virus scanner. If the expression matches, a virus was found. You must make
32168 absolutely sure that this expression matches on &"virus found"&. This is called
32169 the &"trigger"& expression.
32170
32171 .next
32172 Another regular expression, containing exactly one pair of parentheses, to
32173 match the name of the virus found in the scanners output. This is called the
32174 &"name"& expression.
32175 .endlist olist
32176
32177 For example, Sophos Sweep reports a virus on a line like this:
32178 .code
32179 Virus 'W32/Magistr-B' found in file ./those.bat
32180 .endd
32181 For the trigger expression, we can match the phrase &"found in file"&. For the
32182 name expression, we want to extract the W32/Magistr-B string, so we can match
32183 for the single quotes left and right of it. Altogether, this makes the
32184 configuration setting:
32185 .code
32186 av_scanner = cmdline:\
32187 /path/to/sweep -ss -all -rec -archive %s:\
32188 found in file:'(.+)'
32189 .endd
32190 .vitem &%drweb%&
32191 .cindex "virus scanners" "DrWeb"
32192 The DrWeb daemon scanner (&url(http://www.sald.com/)) interface
32193 takes one option,
32194 either a full path to a UNIX socket,
32195 or host and port specifiers separated by white space.
32196 The host may be a name or an IP address; the port is either a
32197 single number or a pair of numbers with a dash between.
32198 For example:
32199 .code
32200 av_scanner = drweb:/var/run/drwebd.sock
32201 av_scanner = drweb:192.168.2.20 31337
32202 .endd
32203 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
32204 is used. Thanks to Alex Miller for contributing the code for this scanner.
32205
32206 .vitem &%f-protd%&
32207 .cindex "virus scanners" "f-protd"
32208 The f-protd scanner is accessed via HTTP over TCP.
32209 One argument is taken, being a space-separated hostname and port number
32210 (or port-range).
32211 For example:
32212 .code
32213 av_scanner = f-protd:localhost 10200-10204
32214 .endd
32215 If you omit the argument, the default values shown above are used.
32216
32217 .vitem &%f-prot6d%&
32218 .cindex "virus scanners" "f-prot6d"
32219 The f-prot6d scanner is accessed using the FPSCAND protocol over TCP.
32220 One argument is taken, being a space-separated hostname and port number.
32221 For example:
32222 .code
32223 av_scanner = f-prot6d:localhost 10200
32224 .endd
32225 If you omit the argument, the default values show above are used.
32226
32227 .vitem &%fsecure%&
32228 .cindex "virus scanners" "F-Secure"
32229 The F-Secure daemon scanner (&url(http://www.f-secure.com)) takes one
32230 argument which is the path to a UNIX socket. For example:
32231 .code
32232 av_scanner = fsecure:/path/to/.fsav
32233 .endd
32234 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
32235 Thelmen for contributing the code for this scanner.
32236
32237 .vitem &%kavdaemon%&
32238 .cindex "virus scanners" "Kaspersky"
32239 This is the scanner daemon of Kaspersky Version 4. This version of the
32240 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
32241 scanner type takes one option, which is the path to the daemon's UNIX socket.
32242 For example:
32243 .code
32244 av_scanner = kavdaemon:/opt/AVP/AvpCtl
32245 .endd
32246 The default path is &_/var/run/AvpCtl_&.
32247
32248 .vitem &%mksd%&
32249 .cindex "virus scanners" "mksd"
32250 This is a daemon type scanner that is aimed mainly at Polish users, though some
32251 parts of documentation are now available in English. You can get it at
32252 &url(http://linux.mks.com.pl/). The only option for this scanner type is
32253 the maximum number of processes used simultaneously to scan the attachments,
32254 provided that mksd has
32255 been run with at least the same number of child processes. For example:
32256 .code
32257 av_scanner = mksd:2
32258 .endd
32259 You can safely omit this option (the default value is 1).
32260
32261 .vitem &%sock%&
32262 .cindex "virus scanners" "simple socket-connected"
32263 This is a general-purpose way of talking to simple scanner daemons
32264 running on the local machine.
32265 There are four options:
32266 an address (which may be an IP address and port, or the path of a Unix socket),
32267 a commandline to send (may include a single %s which will be replaced with
32268 the path to the mail file to be scanned),
32269 an RE to trigger on from the returned data,
32270 and an RE to extract malware_name from the returned data.
32271 For example:
32272 .code
32273 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)$
32274 .endd
32275 Note that surrounding whitespace is stripped from each option, meaning
32276 there is no way to specify a trailing newline.
32277 The socket specifier and both regular-expressions are required.
32278 Default for the commandline is &_%s\n_& (note this does have a trailing newline);
32279 specify an empty element to get this.
32280
32281 .vitem &%sophie%&
32282 .cindex "virus scanners" "Sophos and Sophie"
32283 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
32284 You can get Sophie at &url(http://www.clanfield.info/sophie/). The only option
32285 for this scanner type is the path to the UNIX socket that Sophie uses for
32286 client communication. For example:
32287 .code
32288 av_scanner = sophie:/tmp/sophie
32289 .endd
32290 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
32291 the option.
32292 .endlist
32293
32294 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
32295 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
32296 ACL.
32297
32298 The &%av_scanner%& option is expanded each time &%malware%& is called. This
32299 makes it possible to use different scanners. See further below for an example.
32300 The &%malware%& condition caches its results, so when you use it multiple times
32301 for the same message, the actual scanning process is only carried out once.
32302 However, using expandable items in &%av_scanner%& disables this caching, in
32303 which case each use of the &%malware%& condition causes a new scan of the
32304 message.
32305
32306 The &%malware%& condition takes a right-hand argument that is expanded before
32307 use and taken as a list, slash-separated by default.
32308 The first element can then be one of
32309
32310 .ilist
32311 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
32312 The condition succeeds if a virus was found, and fail otherwise. This is the
32313 recommended usage.
32314 .next
32315 &"false"& or &"0"& or an empty string, in which case no scanning is done and
32316 the condition fails immediately.
32317 .next
32318 A regular expression, in which case the message is scanned for viruses. The
32319 condition succeeds if a virus is found and its name matches the regular
32320 expression. This allows you to take special actions on certain types of virus.
32321 Note that &"/"& characters in the RE must be doubled due to the list-processing,
32322 unless the separator is changed (in the usual way).
32323 .endlist
32324
32325 You can append a &`defer_ok`& element to the &%malware%& argument list to accept
32326 messages even if there is a problem with the virus scanner.
32327 Otherwise, such a problem causes the ACL to defer.
32328
32329 You can append a &`tmo=<val>`& element to the &%malware%& argument list to
32330 specify a non-default timeout. The default is two minutes.
32331 For example:
32332 .code
32333 malware = * / defer_ok / tmo=10s
32334 .endd
32335 A timeout causes the ACL to defer.
32336
32337 .vindex "&$callout_address$&"
32338 When a connection is made to the scanner the expansion variable &$callout_address$&
32339 is set to record the actual address used.
32340
32341 .vindex "&$malware_name$&"
32342 When a virus is found, the condition sets up an expansion variable called
32343 &$malware_name$& that contains the name of the virus. You can use it in a
32344 &%message%& modifier that specifies the error returned to the sender, and/or in
32345 logging data.
32346
32347 Beware the interaction of Exim's &%message_size_limit%& with any size limits
32348 imposed by your anti-virus scanner.
32349
32350 Here is a very simple scanning example:
32351 .code
32352 deny message = This message contains malware ($malware_name)
32353 malware = *
32354 .endd
32355 The next example accepts messages when there is a problem with the scanner:
32356 .code
32357 deny message = This message contains malware ($malware_name)
32358 malware = */defer_ok
32359 .endd
32360 The next example shows how to use an ACL variable to scan with both sophie and
32361 aveserver. It assumes you have set:
32362 .code
32363 av_scanner = $acl_m0
32364 .endd
32365 in the main Exim configuration.
32366 .code
32367 deny message = This message contains malware ($malware_name)
32368 set acl_m0 = sophie
32369 malware = *
32370
32371 deny message = This message contains malware ($malware_name)
32372 set acl_m0 = aveserver
32373 malware = *
32374 .endd
32375
32376
32377 .section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass"
32378 .cindex "content scanning" "for spam"
32379 .cindex "spam scanning"
32380 .cindex "SpamAssassin"
32381 .cindex "Rspamd"
32382 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
32383 score and a report for the message.
32384 Support is also provided for Rspamd.
32385
32386 For more information about installation and configuration of SpamAssassin or
32387 Rspamd refer to their respective websites at
32388 &url(http://spamassassin.apache.org) and &url(http://www.rspamd.com)
32389
32390 SpamAssassin can be installed with CPAN by running:
32391 .code
32392 perl -MCPAN -e 'install Mail::SpamAssassin'
32393 .endd
32394 SpamAssassin has its own set of configuration files. Please review its
32395 documentation to see how you can tweak it. The default installation should work
32396 nicely, however.
32397
32398 .oindex "&%spamd_address%&"
32399 By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
32400 intend to use an instance running on the local host you do not need to set
32401 &%spamd_address%&. If you intend to use another host or port for SpamAssassin,
32402 you must set the &%spamd_address%& option in the global part of the Exim
32403 configuration as follows (example):
32404 .code
32405 spamd_address = 192.168.99.45 387
32406 .endd
32407 The SpamAssassin protocol relies on a TCP half-close from the client.
32408 If your SpamAssassin client side is running a Linux system with an
32409 iptables firewall, consider setting
32410 &%net.netfilter.nf_conntrack_tcp_timeout_close_wait%& to at least the
32411 timeout, Exim uses when waiting for a response from the SpamAssassin
32412 server (currently defaulting to 120s). With a lower value the Linux
32413 connection tracking may consider your half-closed connection as dead too
32414 soon.
32415
32416
32417 To use Rspamd (which by default listens on all local addresses
32418 on TCP port 11333)
32419 you should add &%variant=rspamd%& after the address/port pair, for example:
32420 .code
32421 spamd_address = 127.0.0.1 11333 variant=rspamd
32422 .endd
32423
32424 As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
32425 sockets. If you want to us these, supply &%spamd_address%& with an absolute
32426 file name instead of an address/port pair:
32427 .code
32428 spamd_address = /var/run/spamd_socket
32429 .endd
32430 You can have multiple &%spamd%& servers to improve scalability. These can
32431 reside on other hardware reachable over the network. To specify multiple
32432 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
32433 option, separated with colons (the separator can be changed in the usual way):
32434 .code
32435 spamd_address = 192.168.2.10 783 : \
32436 192.168.2.11 783 : \
32437 192.168.2.12 783
32438 .endd
32439 Up to 32 &%spamd%& servers are supported.
32440 When a server fails to respond to the connection attempt, all other
32441 servers are tried until one succeeds. If no server responds, the &%spam%&
32442 condition defers.
32443
32444 Unix and TCP socket specifications may be mixed in any order.
32445 Each element of the list is a list itself, space-separated by default
32446 and changeable in the usual way; take care to not double the separator.
32447
32448 For TCP socket specifications a host name or IP (v4 or v6, but
32449 subject to list-separator quoting rules) address can be used,
32450 and the port can be one or a dash-separated pair.
32451 In the latter case, the range is tried in strict order.
32452
32453 Elements after the first for Unix sockets, or second for TCP socket,
32454 are options.
32455 The supported options are:
32456 .code
32457 pri=<priority> Selection priority
32458 weight=<value> Selection bias
32459 time=<start>-<end> Use only between these times of day
32460 retry=<timespec> Retry on connect fail
32461 tmo=<timespec> Connection time limit
32462 variant=rspamd Use Rspamd rather than SpamAssassin protocol
32463 .endd
32464
32465 The &`pri`& option specifies a priority for the server within the list,
32466 higher values being tried first.
32467 The default priority is 1.
32468
32469 The &`weight`& option specifies a selection bias.
32470 Within a priority set
32471 servers are queried in a random fashion, weighted by this value.
32472 The default value for selection bias is 1.
32473
32474 Time specifications for the &`time`& option are <hour>.<minute>.<second>
32475 in the local time zone; each element being one or more digits.
32476 Either the seconds or both minutes and seconds, plus the leading &`.`&
32477 characters, may be omitted and will be taken as zero.
32478
32479 Timeout specifications for the &`retry`& and &`tmo`& options
32480 are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
32481
32482 The &`tmo`& option specifies an overall timeout for communication.
32483 The default value is two minutes.
32484
32485 The &`retry`& option specifies a time after which a single retry for
32486 a failed connect is made.
32487 The default is to not retry.
32488
32489 The &%spamd_address%& variable is expanded before use if it starts with
32490 a dollar sign. In this case, the expansion may return a string that is
32491 used as the list so that multiple spamd servers can be the result of an
32492 expansion.
32493
32494 .vindex "&$callout_address$&"
32495 When a connection is made to the server the expansion variable &$callout_address$&
32496 is set to record the actual address used.
32497
32498 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
32499 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
32500 .code
32501 deny message = This message was classified as SPAM
32502 spam = joe
32503 .endd
32504 The right-hand side of the &%spam%& condition specifies a name. This is
32505 relevant if you have set up multiple SpamAssassin profiles. If you do not want
32506 to scan using a specific profile, but rather use the SpamAssassin system-wide
32507 default profile, you can scan for an unknown name, or simply use &"nobody"&.
32508 Rspamd does not use this setting. However, you must put something on the
32509 right-hand side.
32510
32511 The name allows you to use per-domain or per-user antispam profiles in
32512 principle, but this is not straightforward in practice, because a message may
32513 have multiple recipients, not necessarily all in the same domain. Because the
32514 &%spam%& condition has to be called from a DATA-time ACL in order to be able to
32515 read the contents of the message, the variables &$local_part$& and &$domain$&
32516 are not set.
32517 Careful enforcement of single-recipient messages
32518 (e.g. by responding with defer in the recipient ACL for all recipients
32519 after the first),
32520 or the use of PRDR,
32521 .cindex "PRDR" "use for per-user SpamAssassin profiles"
32522 are needed to use this feature.
32523
32524 The right-hand side of the &%spam%& condition is expanded before being used, so
32525 you can put lookups or conditions there. When the right-hand side evaluates to
32526 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
32527
32528
32529 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
32530 large ones may cause significant performance degradation. As most spam messages
32531 are quite small, it is recommended that you do not scan the big ones. For
32532 example:
32533 .code
32534 deny message = This message was classified as SPAM
32535 condition = ${if < {$message_size}{10K}}
32536 spam = nobody
32537 .endd
32538
32539 The &%spam%& condition returns true if the threshold specified in the user's
32540 SpamAssassin profile has been matched or exceeded. If you want to use the
32541 &%spam%& condition for its side effects (see the variables below), you can make
32542 it always return &"true"& by appending &`:true`& to the username.
32543
32544 .cindex "spam scanning" "returned variables"
32545 When the &%spam%& condition is run, it sets up a number of expansion
32546 variables.
32547 Except for &$spam_report$&,
32548 these variables are saved with the received message so are
32549 available for use at delivery time.
32550
32551 .vlist
32552 .vitem &$spam_score$&
32553 The spam score of the message, for example &"3.4"& or &"30.5"&. This is useful
32554 for inclusion in log or reject messages.
32555
32556 .vitem &$spam_score_int$&
32557 The spam score of the message, multiplied by ten, as an integer value. For
32558 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
32559 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
32560 The integer value is useful for numeric comparisons in conditions.
32561
32562 .vitem &$spam_bar$&
32563 A string consisting of a number of &"+"& or &"-"& characters, representing the
32564 integer part of the spam score value. A spam score of 4.4 would have a
32565 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
32566 headers, since MUAs can match on such strings. The maximum length of the
32567 spam bar is 50 characters.
32568
32569 .vitem &$spam_report$&
32570 A multiline text table, containing the full SpamAssassin report for the
32571 message. Useful for inclusion in headers or reject messages.
32572 This variable is only usable in a DATA-time ACL.
32573 Beware that SpamAssassin may return non-ASCII characters, especially
32574 when running in country-specific locales, which are not legal
32575 unencoded in headers.
32576
32577 .vitem &$spam_action$&
32578 For SpamAssassin either 'reject' or 'no action' depending on the
32579 spam score versus threshold.
32580 For Rspamd, the recommended action.
32581
32582 .endlist
32583
32584 The &%spam%& condition caches its results unless expansion in
32585 spamd_address was used. If you call it again with the same user name, it
32586 does not scan again, but rather returns the same values as before.
32587
32588 The &%spam%& condition returns DEFER if there is any error while running
32589 the message through SpamAssassin or if the expansion of spamd_address
32590 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
32591 statement block), append &`/defer_ok`& to the right-hand side of the
32592 spam condition, like this:
32593 .code
32594 deny message = This message was classified as SPAM
32595 spam = joe/defer_ok
32596 .endd
32597 This causes messages to be accepted even if there is a problem with &%spamd%&.
32598
32599 Here is a longer, commented example of the use of the &%spam%&
32600 condition:
32601 .code
32602 # put headers in all messages (no matter if spam or not)
32603 warn spam = nobody:true
32604 add_header = X-Spam-Score: $spam_score ($spam_bar)
32605 add_header = X-Spam-Report: $spam_report
32606
32607 # add second subject line with *SPAM* marker when message
32608 # is over threshold
32609 warn spam = nobody
32610 add_header = Subject: *SPAM* $h_Subject:
32611
32612 # reject spam at high scores (> 12)
32613 deny message = This message scored $spam_score spam points.
32614 spam = nobody:true
32615 condition = ${if >{$spam_score_int}{120}{1}{0}}
32616 .endd
32617
32618
32619
32620 .section "Scanning MIME parts" "SECTscanmimepart"
32621 .cindex "content scanning" "MIME parts"
32622 .cindex "MIME content scanning"
32623 .oindex "&%acl_smtp_mime%&"
32624 .oindex "&%acl_not_smtp_mime%&"
32625 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
32626 each MIME part of an SMTP message, including multipart types, in the sequence
32627 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
32628 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
32629 options may both refer to the same ACL if you want the same processing in both
32630 cases.
32631
32632 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
32633 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
32634 the case of a non-SMTP message. However, a MIME ACL is called only if the
32635 message contains a &'Content-Type:'& header line. When a call to a MIME
32636 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
32637 result code is sent to the client. In the case of an SMTP message, the
32638 &%acl_smtp_data%& ACL is not called when this happens.
32639
32640 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
32641 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
32642 condition to match against the raw MIME part. You can also use the
32643 &%mime_regex%& condition to match against the decoded MIME part (see section
32644 &<<SECTscanregex>>&).
32645
32646 At the start of a MIME ACL, a number of variables are set from the header
32647 information for the relevant MIME part. These are described below. The contents
32648 of the MIME part are not by default decoded into a disk file except for MIME
32649 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
32650 part into a disk file, you can use the &%decode%& condition. The general
32651 syntax is:
32652 .display
32653 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
32654 .endd
32655 The right hand side is expanded before use. After expansion,
32656 the value can be:
32657
32658 .olist
32659 &"0"& or &"false"&, in which case no decoding is done.
32660 .next
32661 The string &"default"&. In that case, the file is put in the temporary
32662 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
32663 a sequential file name consisting of the message id and a sequence number. The
32664 full path and name is available in &$mime_decoded_filename$& after decoding.
32665 .next
32666 A full path name starting with a slash. If the full name is an existing
32667 directory, it is used as a replacement for the default directory. The filename
32668 is then sequentially assigned. If the path does not exist, it is used as
32669 the full path and file name.
32670 .next
32671 If the string does not start with a slash, it is used as the
32672 filename, and the default path is then used.
32673 .endlist
32674 The &%decode%& condition normally succeeds. It is only false for syntax
32675 errors or unusual circumstances such as memory shortages. You can easily decode
32676 a file with its original, proposed filename using
32677 .code
32678 decode = $mime_filename
32679 .endd
32680 However, you should keep in mind that &$mime_filename$& might contain
32681 anything. If you place files outside of the default path, they are not
32682 automatically unlinked.
32683
32684 For RFC822 attachments (these are messages attached to messages, with a
32685 content-type of &"message/rfc822"&), the ACL is called again in the same manner
32686 as for the primary message, only that the &$mime_is_rfc822$& expansion
32687 variable is set (see below). Attached messages are always decoded to disk
32688 before being checked, and the files are unlinked once the check is done.
32689
32690 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
32691 used to match regular expressions against raw and decoded MIME parts,
32692 respectively. They are described in section &<<SECTscanregex>>&.
32693
32694 .cindex "MIME content scanning" "returned variables"
32695 The following list describes all expansion variables that are
32696 available in the MIME ACL:
32697
32698 .vlist
32699 .vitem &$mime_boundary$&
32700 If the current part is a multipart (see &$mime_is_multipart$&) below, it should
32701 have a boundary string, which is stored in this variable. If the current part
32702 has no boundary parameter in the &'Content-Type:'& header, this variable
32703 contains the empty string.
32704
32705 .vitem &$mime_charset$&
32706 This variable contains the character set identifier, if one was found in the
32707 &'Content-Type:'& header. Examples for charset identifiers are:
32708 .code
32709 us-ascii
32710 gb2312 (Chinese)
32711 iso-8859-1
32712 .endd
32713 Please note that this value is not normalized, so you should do matches
32714 case-insensitively.
32715
32716 .vitem &$mime_content_description$&
32717 This variable contains the normalized content of the &'Content-Description:'&
32718 header. It can contain a human-readable description of the parts content. Some
32719 implementations repeat the filename for attachments here, but they are usually
32720 only used for display purposes.
32721
32722 .vitem &$mime_content_disposition$&
32723 This variable contains the normalized content of the &'Content-Disposition:'&
32724 header. You can expect strings like &"attachment"& or &"inline"& here.
32725
32726 .vitem &$mime_content_id$&
32727 This variable contains the normalized content of the &'Content-ID:'& header.
32728 This is a unique ID that can be used to reference a part from another part.
32729
32730 .vitem &$mime_content_size$&
32731 This variable is set only after the &%decode%& modifier (see above) has been
32732 successfully run. It contains the size of the decoded part in kilobytes. The
32733 size is always rounded up to full kilobytes, so only a completely empty part
32734 has a &$mime_content_size$& of zero.
32735
32736 .vitem &$mime_content_transfer_encoding$&
32737 This variable contains the normalized content of the
32738 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
32739 type. Typical values are &"base64"& and &"quoted-printable"&.
32740
32741 .vitem &$mime_content_type$&
32742 If the MIME part has a &'Content-Type:'& header, this variable contains its
32743 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
32744 are some examples of popular MIME types, as they may appear in this variable:
32745 .code
32746 text/plain
32747 text/html
32748 application/octet-stream
32749 image/jpeg
32750 audio/midi
32751 .endd
32752 If the MIME part has no &'Content-Type:'& header, this variable contains the
32753 empty string.
32754
32755 .vitem &$mime_decoded_filename$&
32756 This variable is set only after the &%decode%& modifier (see above) has been
32757 successfully run. It contains the full path and file name of the file
32758 containing the decoded data.
32759 .endlist
32760
32761 .cindex "RFC 2047"
32762 .vlist
32763 .vitem &$mime_filename$&
32764 This is perhaps the most important of the MIME variables. It contains a
32765 proposed filename for an attachment, if one was found in either the
32766 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
32767 RFC2047
32768 or RFC2231
32769 decoded, but no additional sanity checks are done.
32770 If no filename was
32771 found, this variable contains the empty string.
32772
32773 .vitem &$mime_is_coverletter$&
32774 This variable attempts to differentiate the &"cover letter"& of an e-mail from
32775 attached data. It can be used to clamp down on flashy or unnecessarily encoded
32776 content in the cover letter, while not restricting attachments at all.
32777
32778 The variable contains 1 (true) for a MIME part believed to be part of the
32779 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
32780 follows:
32781
32782 .olist
32783 The outermost MIME part of a message is always a cover letter.
32784
32785 .next
32786 If a multipart/alternative or multipart/related MIME part is a cover letter,
32787 so are all MIME subparts within that multipart.
32788
32789 .next
32790 If any other multipart is a cover letter, the first subpart is a cover letter,
32791 and the rest are attachments.
32792
32793 .next
32794 All parts contained within an attachment multipart are attachments.
32795 .endlist olist
32796
32797 As an example, the following will ban &"HTML mail"& (including that sent with
32798 alternative plain text), while allowing HTML files to be attached. HTML
32799 coverletter mail attached to non-HTML coverletter mail will also be allowed:
32800 .code
32801 deny message = HTML mail is not accepted here
32802 !condition = $mime_is_rfc822
32803 condition = $mime_is_coverletter
32804 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
32805 .endd
32806 .vitem &$mime_is_multipart$&
32807 This variable has the value 1 (true) when the current part has the main type
32808 &"multipart"&, for example &"multipart/alternative"& or &"multipart/mixed"&.
32809 Since multipart entities only serve as containers for other parts, you may not
32810 want to carry out specific actions on them.
32811
32812 .vitem &$mime_is_rfc822$&
32813 This variable has the value 1 (true) if the current part is not a part of the
32814 checked message itself, but part of an attached message. Attached message
32815 decoding is fully recursive.
32816
32817 .vitem &$mime_part_count$&
32818 This variable is a counter that is raised for each processed MIME part. It
32819 starts at zero for the very first part (which is usually a multipart). The
32820 counter is per-message, so it is reset when processing RFC822 attachments (see
32821 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
32822 complete, so you can use it in the DATA ACL to determine the number of MIME
32823 parts of a message. For non-MIME messages, this variable contains the value -1.
32824 .endlist
32825
32826
32827
32828 .section "Scanning with regular expressions" "SECTscanregex"
32829 .cindex "content scanning" "with regular expressions"
32830 .cindex "regular expressions" "content scanning with"
32831 You can specify your own custom regular expression matches on the full body of
32832 the message, or on individual MIME parts.
32833
32834 The &%regex%& condition takes one or more regular expressions as arguments and
32835 matches them against the full message (when called in the DATA ACL) or a raw
32836 MIME part (when called in the MIME ACL). The &%regex%& condition matches
32837 linewise, with a maximum line length of 32K characters. That means you cannot
32838 have multiline matches with the &%regex%& condition.
32839
32840 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
32841 to 32K of decoded content (the whole content at once, not linewise). If the
32842 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
32843 is decoded automatically when &%mime_regex%& is executed (using default path
32844 and filename values). If the decoded data is larger than 32K, only the first
32845 32K characters are checked.
32846
32847 The regular expressions are passed as a colon-separated list. To include a
32848 literal colon, you must double it. Since the whole right-hand side string is
32849 expanded before being used, you must also escape dollar signs and backslashes
32850 with more backslashes, or use the &`\N`& facility to disable expansion.
32851 Here is a simple example that contains two regular expressions:
32852 .code
32853 deny message = contains blacklisted regex ($regex_match_string)
32854 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
32855 .endd
32856 The conditions returns true if any one of the regular expressions matches. The
32857 &$regex_match_string$& expansion variable is then set up and contains the
32858 matching regular expression.
32859 The expansion variables &$regex1$& &$regex2$& etc
32860 are set to any substrings captured by the regular expression.
32861
32862 &*Warning*&: With large messages, these conditions can be fairly
32863 CPU-intensive.
32864
32865 .ecindex IIDcosca
32866
32867
32868
32869
32870 . ////////////////////////////////////////////////////////////////////////////
32871 . ////////////////////////////////////////////////////////////////////////////
32872
32873 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
32874 "Local scan function"
32875 .scindex IIDlosca "&[local_scan()]& function" "description of"
32876 .cindex "customizing" "input scan using C function"
32877 .cindex "policy control" "by local scan function"
32878 In these days of email worms, viruses, and ever-increasing spam, some sites
32879 want to apply a lot of checking to messages before accepting them.
32880
32881 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
32882 passing messages to external virus and spam scanning software. You can also do
32883 a certain amount in Exim itself through string expansions and the &%condition%&
32884 condition in the ACL that runs after the SMTP DATA command or the ACL for
32885 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
32886
32887 To allow for further customization to a site's own requirements, there is the
32888 possibility of linking Exim with a private message scanning function, written
32889 in C. If you want to run code that is written in something other than C, you
32890 can of course use a little C stub to call it.
32891
32892 The local scan function is run once for every incoming message, at the point
32893 when Exim is just about to accept the message.
32894 It can therefore be used to control non-SMTP messages from local processes as
32895 well as messages arriving via SMTP.
32896
32897 Exim applies a timeout to calls of the local scan function, and there is an
32898 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
32899 Zero means &"no timeout"&.
32900 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
32901 before calling the local scan function, so that the most common types of crash
32902 are caught. If the timeout is exceeded or one of those signals is caught, the
32903 incoming message is rejected with a temporary error if it is an SMTP message.
32904 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
32905 code. The incident is logged on the main and reject logs.
32906
32907
32908
32909 .section "Building Exim to use a local scan function" "SECID207"
32910 .cindex "&[local_scan()]& function" "building Exim to use"
32911 To make use of the local scan function feature, you must tell Exim where your
32912 function is before building Exim, by setting
32913 .new
32914 both HAVE_LOCAL_SCAN and
32915 .wen
32916 LOCAL_SCAN_SOURCE in your
32917 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
32918 directory, so you might set
32919 .code
32920 HAVE_LOCAL_SCAN=yes
32921 LOCAL_SCAN_SOURCE=Local/local_scan.c
32922 .endd
32923 for example. The function must be called &[local_scan()]&. It is called by
32924 Exim after it has received a message, when the success return code is about to
32925 be sent. This is after all the ACLs have been run. The return code from your
32926 function controls whether the message is actually accepted or not. There is a
32927 commented template function (that just accepts the message) in the file
32928 _src/local_scan.c_.
32929
32930 If you want to make use of Exim's run time configuration file to set options
32931 for your &[local_scan()]& function, you must also set
32932 .code
32933 LOCAL_SCAN_HAS_OPTIONS=yes
32934 .endd
32935 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
32936
32937
32938
32939
32940 .section "API for local_scan()" "SECTapiforloc"
32941 .cindex "&[local_scan()]& function" "API description"
32942 You must include this line near the start of your code:
32943 .code
32944 #include "local_scan.h"
32945 .endd
32946 This header file defines a number of variables and other values, and the
32947 prototype for the function itself. Exim is coded to use unsigned char values
32948 almost exclusively, and one of the things this header defines is a shorthand
32949 for &`unsigned char`& called &`uschar`&.
32950 It also contains the following macro definitions, to simplify casting character
32951 strings and pointers to character strings:
32952 .code
32953 #define CS (char *)
32954 #define CCS (const char *)
32955 #define CSS (char **)
32956 #define US (unsigned char *)
32957 #define CUS (const unsigned char *)
32958 #define USS (unsigned char **)
32959 .endd
32960 The function prototype for &[local_scan()]& is:
32961 .code
32962 extern int local_scan(int fd, uschar **return_text);
32963 .endd
32964 The arguments are as follows:
32965
32966 .ilist
32967 &%fd%& is a file descriptor for the file that contains the body of the message
32968 (the -D file). The file is open for reading and writing, but updating it is not
32969 recommended. &*Warning*&: You must &'not'& close this file descriptor.
32970
32971 The descriptor is positioned at character 19 of the file, which is the first
32972 character of the body itself, because the first 19 characters are the message
32973 id followed by &`-D`& and a newline. If you rewind the file, you should use the
32974 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
32975 case this changes in some future version.
32976 .next
32977 &%return_text%& is an address which you can use to return a pointer to a text
32978 string at the end of the function. The value it points to on entry is NULL.
32979 .endlist
32980
32981 The function must return an &%int%& value which is one of the following macros:
32982
32983 .vlist
32984 .vitem &`LOCAL_SCAN_ACCEPT`&
32985 .vindex "&$local_scan_data$&"
32986 The message is accepted. If you pass back a string of text, it is saved with
32987 the message, and made available in the variable &$local_scan_data$&. No
32988 newlines are permitted (if there are any, they are turned into spaces) and the
32989 maximum length of text is 1000 characters.
32990
32991 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
32992 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
32993 queued without immediate delivery, and is frozen.
32994
32995 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
32996 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
32997 queued without immediate delivery.
32998
32999 .vitem &`LOCAL_SCAN_REJECT`&
33000 The message is rejected; the returned text is used as an error message which is
33001 passed back to the sender and which is also logged. Newlines are permitted &--
33002 they cause a multiline response for SMTP rejections, but are converted to
33003 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
33004 used.
33005
33006 .vitem &`LOCAL_SCAN_TEMPREJECT`&
33007 The message is temporarily rejected; the returned text is used as an error
33008 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
33009 problem"& is used.
33010
33011 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
33012 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
33013 message is not written to the reject log. It has the effect of unsetting the
33014 &%rejected_header%& log selector for just this rejection. If
33015 &%rejected_header%& is already unset (see the discussion of the
33016 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
33017 same as LOCAL_SCAN_REJECT.
33018
33019 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
33020 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
33021 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
33022 .endlist
33023
33024 If the message is not being received by interactive SMTP, rejections are
33025 reported by writing to &%stderr%& or by sending an email, as configured by the
33026 &%-oe%& command line options.
33027
33028
33029
33030 .section "Configuration options for local_scan()" "SECTconoptloc"
33031 .cindex "&[local_scan()]& function" "configuration options"
33032 It is possible to have option settings in the main configuration file
33033 that set values in static variables in the &[local_scan()]& module. If you
33034 want to do this, you must have the line
33035 .code
33036 LOCAL_SCAN_HAS_OPTIONS=yes
33037 .endd
33038 in your &_Local/Makefile_& when you build Exim. (This line is in
33039 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
33040 file, you must define static variables to hold the option values, and a table
33041 to define them.
33042
33043 The table must be a vector called &%local_scan_options%&, of type
33044 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
33045 and a pointer to the variable that holds the value. The entries must appear in
33046 alphabetical order. Following &%local_scan_options%& you must also define a
33047 variable called &%local_scan_options_count%& that contains the number of
33048 entries in the table. Here is a short example, showing two kinds of option:
33049 .code
33050 static int my_integer_option = 42;
33051 static uschar *my_string_option = US"a default string";
33052
33053 optionlist local_scan_options[] = {
33054 { "my_integer", opt_int, &my_integer_option },
33055 { "my_string", opt_stringptr, &my_string_option }
33056 };
33057
33058 int local_scan_options_count =
33059 sizeof(local_scan_options)/sizeof(optionlist);
33060 .endd
33061 The values of the variables can now be changed from Exim's runtime
33062 configuration file by including a local scan section as in this example:
33063 .code
33064 begin local_scan
33065 my_integer = 99
33066 my_string = some string of text...
33067 .endd
33068 The available types of option data are as follows:
33069
33070 .vlist
33071 .vitem &*opt_bool*&
33072 This specifies a boolean (true/false) option. The address should point to a
33073 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
33074 that are defined as &"1"& and &"0"&, respectively. If you want to detect
33075 whether such a variable has been set at all, you can initialize it to
33076 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
33077 values.)
33078
33079 .vitem &*opt_fixed*&
33080 This specifies a fixed point number, such as is used for load averages.
33081 The address should point to a variable of type &`int`&. The value is stored
33082 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
33083
33084 .vitem &*opt_int*&
33085 This specifies an integer; the address should point to a variable of type
33086 &`int`&. The value may be specified in any of the integer formats accepted by
33087 Exim.
33088
33089 .vitem &*opt_mkint*&
33090 This is the same as &%opt_int%&, except that when such a value is output in a
33091 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
33092 printed with the suffix K or M.
33093
33094 .vitem &*opt_octint*&
33095 This also specifies an integer, but the value is always interpreted as an
33096 octal integer, whether or not it starts with the digit zero, and it is
33097 always output in octal.
33098
33099 .vitem &*opt_stringptr*&
33100 This specifies a string value; the address must be a pointer to a
33101 variable that points to a string (for example, of type &`uschar *`&).
33102
33103 .vitem &*opt_time*&
33104 This specifies a time interval value. The address must point to a variable of
33105 type &`int`&. The value that is placed there is a number of seconds.
33106 .endlist
33107
33108 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
33109 out the values of all the &[local_scan()]& options.
33110
33111
33112
33113 .section "Available Exim variables" "SECID208"
33114 .cindex "&[local_scan()]& function" "available Exim variables"
33115 The header &_local_scan.h_& gives you access to a number of C variables. These
33116 are the only ones that are guaranteed to be maintained from release to release.
33117 Note, however, that you can obtain the value of any Exim expansion variable,
33118 including &$recipients$&, by calling &'expand_string()'&. The exported
33119 C variables are as follows:
33120
33121 .vlist
33122 .vitem &*int&~body_linecount*&
33123 This variable contains the number of lines in the message's body.
33124 It is not valid if the &%spool_files_wireformat%& option is used.
33125
33126 .vitem &*int&~body_zerocount*&
33127 This variable contains the number of binary zero bytes in the message's body.
33128 It is not valid if the &%spool_files_wireformat%& option is used.
33129
33130 .vitem &*unsigned&~int&~debug_selector*&
33131 This variable is set to zero when no debugging is taking place. Otherwise, it
33132 is a bitmap of debugging selectors. Two bits are identified for use in
33133 &[local_scan()]&; they are defined as macros:
33134
33135 .ilist
33136 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
33137 testing option that is not privileged &-- any caller may set it. All the
33138 other selector bits can be set only by admin users.
33139
33140 .next
33141 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
33142 by the &`+local_scan`& debug selector. It is not included in the default set
33143 of debugging bits.
33144 .endlist ilist
33145
33146 Thus, to write to the debugging output only when &`+local_scan`& has been
33147 selected, you should use code like this:
33148 .code
33149 if ((debug_selector & D_local_scan) != 0)
33150 debug_printf("xxx", ...);
33151 .endd
33152 .vitem &*uschar&~*expand_string_message*&
33153 After a failing call to &'expand_string()'& (returned value NULL), the
33154 variable &%expand_string_message%& contains the error message, zero-terminated.
33155
33156 .vitem &*header_line&~*header_list*&
33157 A pointer to a chain of header lines. The &%header_line%& structure is
33158 discussed below.
33159
33160 .vitem &*header_line&~*header_last*&
33161 A pointer to the last of the header lines.
33162
33163 .vitem &*uschar&~*headers_charset*&
33164 The value of the &%headers_charset%& configuration option.
33165
33166 .vitem &*BOOL&~host_checking*&
33167 This variable is TRUE during a host checking session that is initiated by the
33168 &%-bh%& command line option.
33169
33170 .vitem &*uschar&~*interface_address*&
33171 The IP address of the interface that received the message, as a string. This
33172 is NULL for locally submitted messages.
33173
33174 .vitem &*int&~interface_port*&
33175 The port on which this message was received. When testing with the &%-bh%&
33176 command line option, the value of this variable is -1 unless a port has been
33177 specified via the &%-oMi%& option.
33178
33179 .vitem &*uschar&~*message_id*&
33180 This variable contains Exim's message id for the incoming message (the value of
33181 &$message_exim_id$&) as a zero-terminated string.
33182
33183 .vitem &*uschar&~*received_protocol*&
33184 The name of the protocol by which the message was received.
33185
33186 .vitem &*int&~recipients_count*&
33187 The number of accepted recipients.
33188
33189 .vitem &*recipient_item&~*recipients_list*&
33190 .cindex "recipient" "adding in local scan"
33191 .cindex "recipient" "removing in local scan"
33192 The list of accepted recipients, held in a vector of length
33193 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
33194 can add additional recipients by calling &'receive_add_recipient()'& (see
33195 below). You can delete recipients by removing them from the vector and
33196 adjusting the value in &%recipients_count%&. In particular, by setting
33197 &%recipients_count%& to zero you remove all recipients. If you then return the
33198 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
33199 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
33200 and then call &'receive_add_recipient()'& as often as needed.
33201
33202 .vitem &*uschar&~*sender_address*&
33203 The envelope sender address. For bounce messages this is the empty string.
33204
33205 .vitem &*uschar&~*sender_host_address*&
33206 The IP address of the sending host, as a string. This is NULL for
33207 locally-submitted messages.
33208
33209 .vitem &*uschar&~*sender_host_authenticated*&
33210 The name of the authentication mechanism that was used, or NULL if the message
33211 was not received over an authenticated SMTP connection.
33212
33213 .vitem &*uschar&~*sender_host_name*&
33214 The name of the sending host, if known.
33215
33216 .vitem &*int&~sender_host_port*&
33217 The port on the sending host.
33218
33219 .vitem &*BOOL&~smtp_input*&
33220 This variable is TRUE for all SMTP input, including BSMTP.
33221
33222 .vitem &*BOOL&~smtp_batched_input*&
33223 This variable is TRUE for BSMTP input.
33224
33225 .vitem &*int&~store_pool*&
33226 The contents of this variable control which pool of memory is used for new
33227 requests. See section &<<SECTmemhanloc>>& for details.
33228 .endlist
33229
33230
33231 .section "Structure of header lines" "SECID209"
33232 The &%header_line%& structure contains the members listed below.
33233 You can add additional header lines by calling the &'header_add()'& function
33234 (see below). You can cause header lines to be ignored (deleted) by setting
33235 their type to *.
33236
33237
33238 .vlist
33239 .vitem &*struct&~header_line&~*next*&
33240 A pointer to the next header line, or NULL for the last line.
33241
33242 .vitem &*int&~type*&
33243 A code identifying certain headers that Exim recognizes. The codes are printing
33244 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
33245 Notice in particular that any header line whose type is * is not transmitted
33246 with the message. This flagging is used for header lines that have been
33247 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
33248 lines.) Effectively, * means &"deleted"&.
33249
33250 .vitem &*int&~slen*&
33251 The number of characters in the header line, including the terminating and any
33252 internal newlines.
33253
33254 .vitem &*uschar&~*text*&
33255 A pointer to the text of the header. It always ends with a newline, followed by
33256 a zero byte. Internal newlines are preserved.
33257 .endlist
33258
33259
33260
33261 .section "Structure of recipient items" "SECID210"
33262 The &%recipient_item%& structure contains these members:
33263
33264 .vlist
33265 .vitem &*uschar&~*address*&
33266 This is a pointer to the recipient address as it was received.
33267
33268 .vitem &*int&~pno*&
33269 This is used in later Exim processing when top level addresses are created by
33270 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
33271 and must always contain -1 at this stage.
33272
33273 .vitem &*uschar&~*errors_to*&
33274 If this value is not NULL, bounce messages caused by failing to deliver to the
33275 recipient are sent to the address it contains. In other words, it overrides the
33276 envelope sender for this one recipient. (Compare the &%errors_to%& generic
33277 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
33278 an unqualified address, Exim qualifies it using the domain from
33279 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
33280 is NULL for all recipients.
33281 .endlist
33282
33283
33284
33285 .section "Available Exim functions" "SECID211"
33286 .cindex "&[local_scan()]& function" "available Exim functions"
33287 The header &_local_scan.h_& gives you access to a number of Exim functions.
33288 These are the only ones that are guaranteed to be maintained from release to
33289 release:
33290
33291 .vlist
33292 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
33293 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
33294
33295 This function creates a child process that runs the command specified by
33296 &%argv%&. The environment for the process is specified by &%envp%&, which can
33297 be NULL if no environment variables are to be passed. A new umask is supplied
33298 for the process in &%newumask%&.
33299
33300 Pipes to the standard input and output of the new process are set up
33301 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
33302 standard error is cloned to the standard output. If there are any file
33303 descriptors &"in the way"& in the new process, they are closed. If the final
33304 argument is TRUE, the new process is made into a process group leader.
33305
33306 The function returns the pid of the new process, or -1 if things go wrong.
33307
33308 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
33309 This function waits for a child process to terminate, or for a timeout (in
33310 seconds) to expire. A timeout value of zero means wait as long as it takes. The
33311 return value is as follows:
33312
33313 .ilist
33314 >= 0
33315
33316 The process terminated by a normal exit and the value is the process
33317 ending status.
33318
33319 .next
33320 < 0 and > &--256
33321
33322 The process was terminated by a signal and the value is the negation of the
33323 signal number.
33324
33325 .next
33326 &--256
33327
33328 The process timed out.
33329 .next
33330 &--257
33331
33332 The was some other error in wait(); &%errno%& is still set.
33333 .endlist
33334
33335 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
33336 This function provide you with a means of submitting a new message to
33337 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
33338 want, but this packages it all up for you.) The function creates a pipe,
33339 forks a subprocess that is running
33340 .code
33341 exim -t -oem -oi -f <>
33342 .endd
33343 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
33344 that is connected to the standard input. The yield of the function is the PID
33345 of the subprocess. You can then write a message to the file descriptor, with
33346 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
33347
33348 When you have finished, call &'child_close()'& to wait for the process to
33349 finish and to collect its ending status. A timeout value of zero is usually
33350 fine in this circumstance. Unless you have made a mistake with the recipient
33351 addresses, you should get a return code of zero.
33352
33353
33354 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
33355 *sender_authentication)*&
33356 This function is a more sophisticated version of &'child_open()'&. The command
33357 that it runs is:
33358 .display
33359 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
33360 .endd
33361 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
33362
33363
33364 .vitem &*void&~debug_printf(char&~*,&~...)*&
33365 This is Exim's debugging function, with arguments as for &'(printf()'&. The
33366 output is written to the standard error stream. If no debugging is selected,
33367 calls to &'debug_printf()'& have no effect. Normally, you should make calls
33368 conditional on the &`local_scan`& debug selector by coding like this:
33369 .code
33370 if ((debug_selector & D_local_scan) != 0)
33371 debug_printf("xxx", ...);
33372 .endd
33373
33374 .vitem &*uschar&~*expand_string(uschar&~*string)*&
33375 This is an interface to Exim's string expansion code. The return value is the
33376 expanded string, or NULL if there was an expansion failure.
33377 The C variable &%expand_string_message%& contains an error message after an
33378 expansion failure. If expansion does not change the string, the return value is
33379 the pointer to the input string. Otherwise, the return value points to a new
33380 block of memory that was obtained by a call to &'store_get()'&. See section
33381 &<<SECTmemhanloc>>& below for a discussion of memory handling.
33382
33383 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
33384 This function allows you to an add additional header line at the end of the
33385 existing ones. The first argument is the type, and should normally be a space
33386 character. The second argument is a format string and any number of
33387 substitution arguments as for &[sprintf()]&. You may include internal newlines
33388 if you want, and you must ensure that the string ends with a newline.
33389
33390 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
33391 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
33392 This function adds a new header line at a specified point in the header
33393 chain. The header itself is specified as for &'header_add()'&.
33394
33395 If &%name%& is NULL, the new header is added at the end of the chain if
33396 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
33397 NULL, the header lines are searched for the first non-deleted header that
33398 matches the name. If one is found, the new header is added before it if
33399 &%after%& is false. If &%after%& is true, the new header is added after the
33400 found header and any adjacent subsequent ones with the same name (even if
33401 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
33402 option controls where the header is added. If it is true, addition is at the
33403 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
33404 headers, or at the top if there are no &'Received:'& headers, you could use
33405 .code
33406 header_add_at_position(TRUE, US"Received", TRUE,
33407 ' ', "X-xxx: ...");
33408 .endd
33409 Normally, there is always at least one non-deleted &'Received:'& header, but
33410 there may not be if &%received_header_text%& expands to an empty string.
33411
33412
33413 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
33414 This function removes header lines. If &%occurrence%& is zero or negative, all
33415 occurrences of the header are removed. If occurrence is greater than zero, that
33416 particular instance of the header is removed. If no header(s) can be found that
33417 match the specification, the function does nothing.
33418
33419
33420 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
33421 int&~length,&~BOOL&~notdel)*&"
33422 This function tests whether the given header has the given name. It is not just
33423 a string comparison, because white space is permitted between the name and the
33424 colon. If the &%notdel%& argument is true, a false return is forced for all
33425 &"deleted"& headers; otherwise they are not treated specially. For example:
33426 .code
33427 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
33428 .endd
33429 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
33430 .cindex "base64 encoding" "functions for &[local_scan()]& use"
33431 This function base64-encodes a string, which is passed by address and length.
33432 The text may contain bytes of any value, including zero. The result is passed
33433 back in dynamic memory that is obtained by calling &'store_get()'&. It is
33434 zero-terminated.
33435
33436 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
33437 This function decodes a base64-encoded string. Its arguments are a
33438 zero-terminated base64-encoded string and the address of a variable that is set
33439 to point to the result, which is in dynamic memory. The length of the decoded
33440 string is the yield of the function. If the input is invalid base64 data, the
33441 yield is -1. A zero byte is added to the end of the output string to make it
33442 easy to interpret as a C string (assuming it contains no zeros of its own). The
33443 added zero byte is not included in the returned count.
33444
33445 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
33446 This function checks for a match in a domain list. Domains are always
33447 matched caselessly. The return value is one of the following:
33448 .display
33449 &`OK `& match succeeded
33450 &`FAIL `& match failed
33451 &`DEFER `& match deferred
33452 .endd
33453 DEFER is usually caused by some kind of lookup defer, such as the
33454 inability to contact a database.
33455
33456 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
33457 BOOL&~caseless)*&"
33458 This function checks for a match in a local part list. The third argument
33459 controls case-sensitivity. The return values are as for
33460 &'lss_match_domain()'&.
33461
33462 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
33463 BOOL&~caseless)*&"
33464 This function checks for a match in an address list. The third argument
33465 controls the case-sensitivity of the local part match. The domain is always
33466 matched caselessly. The return values are as for &'lss_match_domain()'&.
33467
33468 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
33469 uschar&~*list)*&"
33470 This function checks for a match in a host list. The most common usage is
33471 expected to be
33472 .code
33473 lss_match_host(sender_host_name, sender_host_address, ...)
33474 .endd
33475 .vindex "&$sender_host_address$&"
33476 An empty address field matches an empty item in the host list. If the host name
33477 is NULL, the name corresponding to &$sender_host_address$& is automatically
33478 looked up if a host name is required to match an item in the list. The return
33479 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
33480 returns ERROR in the case when it had to look up a host name, but the lookup
33481 failed.
33482
33483 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
33484 *format,&~...)*&"
33485 This function writes to Exim's log files. The first argument should be zero (it
33486 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
33487 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
33488 them. It specifies to which log or logs the message is written. The remaining
33489 arguments are a format and relevant insertion arguments. The string should not
33490 contain any newlines, not even at the end.
33491
33492
33493 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
33494 This function adds an additional recipient to the message. The first argument
33495 is the recipient address. If it is unqualified (has no domain), it is qualified
33496 with the &%qualify_recipient%& domain. The second argument must always be -1.
33497
33498 This function does not allow you to specify a private &%errors_to%& address (as
33499 described with the structure of &%recipient_item%& above), because it pre-dates
33500 the addition of that field to the structure. However, it is easy to add such a
33501 value afterwards. For example:
33502 .code
33503 receive_add_recipient(US"monitor@mydom.example", -1);
33504 recipients_list[recipients_count-1].errors_to =
33505 US"postmaster@mydom.example";
33506 .endd
33507
33508 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
33509 This is a convenience function to remove a named recipient from the list of
33510 recipients. It returns true if a recipient was removed, and false if no
33511 matching recipient could be found. The argument must be a complete email
33512 address.
33513 .endlist
33514
33515
33516 .cindex "RFC 2047"
33517 .vlist
33518 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
33519 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
33520 This function decodes strings that are encoded according to RFC 2047. Typically
33521 these are the contents of header lines. First, each &"encoded word"& is decoded
33522 from the Q or B encoding into a byte-string. Then, if provided with the name of
33523 a charset encoding, and if the &[iconv()]& function is available, an attempt is
33524 made to translate the result to the named character set. If this fails, the
33525 binary string is returned with an error message.
33526
33527 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
33528 maximum MIME word length is enforced. The third argument is the target
33529 encoding, or NULL if no translation is wanted.
33530
33531 .cindex "binary zero" "in RFC 2047 decoding"
33532 .cindex "RFC 2047" "binary zero in"
33533 If a binary zero is encountered in the decoded string, it is replaced by the
33534 contents of the &%zeroval%& argument. For use with Exim headers, the value must
33535 not be 0 because header lines are handled as zero-terminated strings.
33536
33537 The function returns the result of processing the string, zero-terminated; if
33538 &%lenptr%& is not NULL, the length of the result is set in the variable to
33539 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
33540
33541 If an error is encountered, the function returns NULL and uses the &%error%&
33542 argument to return an error message. The variable pointed to by &%error%& is
33543 set to NULL if there is no error; it may be set non-NULL even when the function
33544 returns a non-NULL value if decoding was successful, but there was a problem
33545 with translation.
33546
33547
33548 .vitem &*int&~smtp_fflush(void)*&
33549 This function is used in conjunction with &'smtp_printf()'&, as described
33550 below.
33551
33552 .vitem &*void&~smtp_printf(char&~*,&~...)*&
33553 The arguments of this function are like &[printf()]&; it writes to the SMTP
33554 output stream. You should use this function only when there is an SMTP output
33555 stream, that is, when the incoming message is being received via interactive
33556 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
33557 is FALSE. If you want to test for an incoming message from another host (as
33558 opposed to a local process that used the &%-bs%& command line option), you can
33559 test the value of &%sender_host_address%&, which is non-NULL when a remote host
33560 is involved.
33561
33562 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
33563 output function, so it can be used for all forms of SMTP connection.
33564
33565 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
33566 must start with an appropriate response code: 550 if you are going to return
33567 LOCAL_SCAN_REJECT, 451 if you are going to return
33568 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
33569 initial lines of a multi-line response, the code must be followed by a hyphen
33570 to indicate that the line is not the final response line. You must also ensure
33571 that the lines you write terminate with CRLF. For example:
33572 .code
33573 smtp_printf("550-this is some extra info\r\n");
33574 return LOCAL_SCAN_REJECT;
33575 .endd
33576 Note that you can also create multi-line responses by including newlines in
33577 the data returned via the &%return_text%& argument. The added value of using
33578 &'smtp_printf()'& is that, for instance, you could introduce delays between
33579 multiple output lines.
33580
33581 The &'smtp_printf()'& function does not return any error indication, because it
33582 does not automatically flush pending output, and therefore does not test
33583 the state of the stream. (In the main code of Exim, flushing and error
33584 detection is done when Exim is ready for the next SMTP input command.) If
33585 you want to flush the output and check for an error (for example, the
33586 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
33587 arguments. It flushes the output stream, and returns a non-zero value if there
33588 is an error.
33589
33590 .vitem &*void&~*store_get(int)*&
33591 This function accesses Exim's internal store (memory) manager. It gets a new
33592 chunk of memory whose size is given by the argument. Exim bombs out if it ever
33593 runs out of memory. See the next section for a discussion of memory handling.
33594
33595 .vitem &*void&~*store_get_perm(int)*&
33596 This function is like &'store_get()'&, but it always gets memory from the
33597 permanent pool. See the next section for a discussion of memory handling.
33598
33599 .vitem &*uschar&~*string_copy(uschar&~*string)*&
33600 See below.
33601
33602 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
33603 See below.
33604
33605 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
33606 These three functions create strings using Exim's dynamic memory facilities.
33607 The first makes a copy of an entire string. The second copies up to a maximum
33608 number of characters, indicated by the second argument. The third uses a format
33609 and insertion arguments to create a new string. In each case, the result is a
33610 pointer to a new string in the current memory pool. See the next section for
33611 more discussion.
33612 .endlist
33613
33614
33615
33616 .section "More about Exim's memory handling" "SECTmemhanloc"
33617 .cindex "&[local_scan()]& function" "memory handling"
33618 No function is provided for freeing memory, because that is never needed.
33619 The dynamic memory that Exim uses when receiving a message is automatically
33620 recycled if another message is received by the same process (this applies only
33621 to incoming SMTP connections &-- other input methods can supply only one
33622 message at a time). After receiving the last message, a reception process
33623 terminates.
33624
33625 Because it is recycled, the normal dynamic memory cannot be used for holding
33626 data that must be preserved over a number of incoming messages on the same SMTP
33627 connection. However, Exim in fact uses two pools of dynamic memory; the second
33628 one is not recycled, and can be used for this purpose.
33629
33630 If you want to allocate memory that remains available for subsequent messages
33631 in the same SMTP connection, you should set
33632 .code
33633 store_pool = POOL_PERM
33634 .endd
33635 before calling the function that does the allocation. There is no need to
33636 restore the value if you do not need to; however, if you do want to revert to
33637 the normal pool, you can either restore the previous value of &%store_pool%& or
33638 set it explicitly to POOL_MAIN.
33639
33640 The pool setting applies to all functions that get dynamic memory, including
33641 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
33642 There is also a convenience function called &'store_get_perm()'& that gets a
33643 block of memory from the permanent pool while preserving the value of
33644 &%store_pool%&.
33645 .ecindex IIDlosca
33646
33647
33648
33649
33650 . ////////////////////////////////////////////////////////////////////////////
33651 . ////////////////////////////////////////////////////////////////////////////
33652
33653 .chapter "System-wide message filtering" "CHAPsystemfilter"
33654 .scindex IIDsysfil1 "filter" "system filter"
33655 .scindex IIDsysfil2 "filtering all mail"
33656 .scindex IIDsysfil3 "system filter"
33657 The previous chapters (on ACLs and the local scan function) describe checks
33658 that can be applied to messages before they are accepted by a host. There is
33659 also a mechanism for checking messages once they have been received, but before
33660 they are delivered. This is called the &'system filter'&.
33661
33662 The system filter operates in a similar manner to users' filter files, but it
33663 is run just once per message (however many recipients the message has).
33664 It should not normally be used as a substitute for routing, because &%deliver%&
33665 commands in a system router provide new envelope recipient addresses.
33666 The system filter must be an Exim filter. It cannot be a Sieve filter.
33667
33668 The system filter is run at the start of a delivery attempt, before any routing
33669 is done. If a message fails to be completely delivered at the first attempt,
33670 the system filter is run again at the start of every retry.
33671 If you want your filter to do something only once per message, you can make use
33672 of the &%first_delivery%& condition in an &%if%& command in the filter to
33673 prevent it happening on retries.
33674
33675 .vindex "&$domain$&"
33676 .vindex "&$local_part$&"
33677 &*Warning*&: Because the system filter runs just once, variables that are
33678 specific to individual recipient addresses, such as &$local_part$& and
33679 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
33680 you want to run a centrally-specified filter for each recipient address
33681 independently, you can do so by setting up a suitable &(redirect)& router, as
33682 described in section &<<SECTperaddfil>>& below.
33683
33684
33685 .section "Specifying a system filter" "SECID212"
33686 .cindex "uid (user id)" "system filter"
33687 .cindex "gid (group id)" "system filter"
33688 The name of the file that contains the system filter must be specified by
33689 setting &%system_filter%&. If you want the filter to run under a uid and gid
33690 other than root, you must also set &%system_filter_user%& and
33691 &%system_filter_group%& as appropriate. For example:
33692 .code
33693 system_filter = /etc/mail/exim.filter
33694 system_filter_user = exim
33695 .endd
33696 If a system filter generates any deliveries directly to files or pipes (via the
33697 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
33698 specified by setting &%system_filter_file_transport%& and
33699 &%system_filter_pipe_transport%&, respectively. Similarly,
33700 &%system_filter_reply_transport%& must be set to handle any messages generated
33701 by the &%reply%& command.
33702
33703
33704 .section "Testing a system filter" "SECID213"
33705 You can run simple tests of a system filter in the same way as for a user
33706 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
33707 are permitted only in system filters are recognized.
33708
33709 If you want to test the combined effect of a system filter and a user filter,
33710 you can use both &%-bF%& and &%-bf%& on the same command line.
33711
33712
33713
33714 .section "Contents of a system filter" "SECID214"
33715 The language used to specify system filters is the same as for users' filter
33716 files. It is described in the separate end-user document &'Exim's interface to
33717 mail filtering'&. However, there are some additional features that are
33718 available only in system filters; these are described in subsequent sections.
33719 If they are encountered in a user's filter file or when testing with &%-bf%&,
33720 they cause errors.
33721
33722 .cindex "frozen messages" "manual thaw; testing in filter"
33723 There are two special conditions which, though available in users' filter
33724 files, are designed for use in system filters. The condition &%first_delivery%&
33725 is true only for the first attempt at delivering a message, and
33726 &%manually_thawed%& is true only if the message has been frozen, and
33727 subsequently thawed by an admin user. An explicit forced delivery counts as a
33728 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
33729
33730 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
33731 specify an &"unseen"& (non-significant) delivery, and that delivery does not
33732 succeed, it will not be tried again.
33733 If you want Exim to retry an unseen delivery until it succeeds, you should
33734 arrange to set it up every time the filter runs.
33735
33736 When a system filter finishes running, the values of the variables &$n0$& &--
33737 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
33738 users' filter files. Thus a system filter can, for example, set up &"scores"&
33739 to which users' filter files can refer.
33740
33741
33742
33743 .section "Additional variable for system filters" "SECID215"
33744 .vindex "&$recipients$&"
33745 The expansion variable &$recipients$&, containing a list of all the recipients
33746 of the message (separated by commas and white space), is available in system
33747 filters. It is not available in users' filters for privacy reasons.
33748
33749
33750
33751 .section "Defer, freeze, and fail commands for system filters" "SECID216"
33752 .cindex "freezing messages"
33753 .cindex "message" "freezing"
33754 .cindex "message" "forced failure"
33755 .cindex "&%fail%&" "in system filter"
33756 .cindex "&%freeze%& in system filter"
33757 .cindex "&%defer%& in system filter"
33758 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
33759 always available in system filters, but are not normally enabled in users'
33760 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
33761 for the &(redirect)& router.) These commands can optionally be followed by the
33762 word &%text%& and a string containing an error message, for example:
33763 .code
33764 fail text "this message looks like spam to me"
33765 .endd
33766 The keyword &%text%& is optional if the next character is a double quote.
33767
33768 The &%defer%& command defers delivery of the original recipients of the
33769 message. The &%fail%& command causes all the original recipients to be failed,
33770 and a bounce message to be created. The &%freeze%& command suspends all
33771 delivery attempts for the original recipients. In all cases, any new deliveries
33772 that are specified by the filter are attempted as normal after the filter has
33773 run.
33774
33775 The &%freeze%& command is ignored if the message has been manually unfrozen and
33776 not manually frozen since. This means that automatic freezing by a system
33777 filter can be used as a way of checking out suspicious messages. If a message
33778 is found to be all right, manually unfreezing it allows it to be delivered.
33779
33780 .cindex "log" "&%fail%& command log line"
33781 .cindex "&%fail%&" "log line; reducing"
33782 The text given with a fail command is used as part of the bounce message as
33783 well as being written to the log. If the message is quite long, this can fill
33784 up a lot of log space when such failures are common. To reduce the size of the
33785 log message, Exim interprets the text in a special way if it starts with the
33786 two characters &`<<`& and contains &`>>`& later. The text between these two
33787 strings is written to the log, and the rest of the text is used in the bounce
33788 message. For example:
33789 .code
33790 fail "<<filter test 1>>Your message is rejected \
33791 because it contains attachments that we are \
33792 not prepared to receive."
33793 .endd
33794
33795 .cindex "loop" "caused by &%fail%&"
33796 Take great care with the &%fail%& command when basing the decision to fail on
33797 the contents of the message, because the bounce message will of course include
33798 the contents of the original message and will therefore trigger the &%fail%&
33799 command again (causing a mail loop) unless steps are taken to prevent this.
33800 Testing the &%error_message%& condition is one way to prevent this. You could
33801 use, for example
33802 .code
33803 if $message_body contains "this is spam" and not error_message
33804 then fail text "spam is not wanted here" endif
33805 .endd
33806 though of course that might let through unwanted bounce messages. The
33807 alternative is clever checking of the body and/or headers to detect bounces
33808 generated by the filter.
33809
33810 The interpretation of a system filter file ceases after a
33811 &%defer%&,
33812 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
33813 set up earlier in the filter file are honoured, so you can use a sequence such
33814 as
33815 .code
33816 mail ...
33817 freeze
33818 .endd
33819 to send a specified message when the system filter is freezing (or deferring or
33820 failing) a message. The normal deliveries for the message do not, of course,
33821 take place.
33822
33823
33824
33825 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
33826 .cindex "header lines" "adding; in system filter"
33827 .cindex "header lines" "removing; in system filter"
33828 .cindex "filter" "header lines; adding/removing"
33829 Two filter commands that are available only in system filters are:
33830 .code
33831 headers add <string>
33832 headers remove <string>
33833 .endd
33834 The argument for the &%headers add%& is a string that is expanded and then
33835 added to the end of the message's headers. It is the responsibility of the
33836 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
33837 space is ignored, and if the string is otherwise empty, or if the expansion is
33838 forced to fail, the command has no effect.
33839
33840 You can use &"\n"& within the string, followed by white space, to specify
33841 continued header lines. More than one header may be added in one command by
33842 including &"\n"& within the string without any following white space. For
33843 example:
33844 .code
33845 headers add "X-header-1: ....\n \
33846 continuation of X-header-1 ...\n\
33847 X-header-2: ...."
33848 .endd
33849 Note that the header line continuation white space after the first newline must
33850 be placed before the backslash that continues the input string, because white
33851 space after input continuations is ignored.
33852
33853 The argument for &%headers remove%& is a colon-separated list of header names.
33854 This command applies only to those headers that are stored with the message;
33855 those that are added at delivery time (such as &'Envelope-To:'& and
33856 &'Return-Path:'&) cannot be removed by this means. If there is more than one
33857 header with the same name, they are all removed.
33858
33859 The &%headers%& command in a system filter makes an immediate change to the set
33860 of header lines that was received with the message (with possible additions
33861 from ACL processing). Subsequent commands in the system filter operate on the
33862 modified set, which also forms the basis for subsequent message delivery.
33863 Unless further modified during routing or transporting, this set of headers is
33864 used for all recipients of the message.
33865
33866 During routing and transporting, the variables that refer to the contents of
33867 header lines refer only to those lines that are in this set. Thus, header lines
33868 that are added by a system filter are visible to users' filter files and to all
33869 routers and transports. This contrasts with the manipulation of header lines by
33870 routers and transports, which is not immediate, but which instead is saved up
33871 until the message is actually being written (see section
33872 &<<SECTheadersaddrem>>&).
33873
33874 If the message is not delivered at the first attempt, header lines that were
33875 added by the system filter are stored with the message, and so are still
33876 present at the next delivery attempt. Header lines that were removed are still
33877 present, but marked &"deleted"& so that they are not transported with the
33878 message. For this reason, it is usual to make the &%headers%& command
33879 conditional on &%first_delivery%& so that the set of header lines is not
33880 modified more than once.
33881
33882 Because header modification in a system filter acts immediately, you have to
33883 use an indirect approach if you want to modify the contents of a header line.
33884 For example:
33885 .code
33886 headers add "Old-Subject: $h_subject:"
33887 headers remove "Subject"
33888 headers add "Subject: new subject (was: $h_old-subject:)"
33889 headers remove "Old-Subject"
33890 .endd
33891
33892
33893
33894 .section "Setting an errors address in a system filter" "SECID217"
33895 .cindex "envelope sender"
33896 In a system filter, if a &%deliver%& command is followed by
33897 .code
33898 errors_to <some address>
33899 .endd
33900 in order to change the envelope sender (and hence the error reporting) for that
33901 delivery, any address may be specified. (In a user filter, only the current
33902 user's address can be set.) For example, if some mail is being monitored, you
33903 might use
33904 .code
33905 unseen deliver monitor@spying.example errors_to root@local.example
33906 .endd
33907 to take a copy which would not be sent back to the normal error reporting
33908 address if its delivery failed.
33909
33910
33911
33912 .section "Per-address filtering" "SECTperaddfil"
33913 .vindex "&$domain$&"
33914 .vindex "&$local_part$&"
33915 In contrast to the system filter, which is run just once per message for each
33916 delivery attempt, it is also possible to set up a system-wide filtering
33917 operation that runs once for each recipient address. In this case, variables
33918 such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
33919 filter file could be made dependent on them. This is an example of a router
33920 which implements such a filter:
33921 .code
33922 central_filter:
33923 check_local_user
33924 driver = redirect
33925 domains = +local_domains
33926 file = /central/filters/$local_part
33927 no_verify
33928 allow_filter
33929 allow_freeze
33930 .endd
33931 The filter is run in a separate process under its own uid. Therefore, either
33932 &%check_local_user%& must be set (as above), in which case the filter is run as
33933 the local user, or the &%user%& option must be used to specify which user to
33934 use. If both are set, &%user%& overrides.
33935
33936 Care should be taken to ensure that none of the commands in the filter file
33937 specify a significant delivery if the message is to go on to be delivered to
33938 its intended recipient. The router will not then claim to have dealt with the
33939 address, so it will be passed on to subsequent routers to be delivered in the
33940 normal way.
33941 .ecindex IIDsysfil1
33942 .ecindex IIDsysfil2
33943 .ecindex IIDsysfil3
33944
33945
33946
33947
33948
33949
33950 . ////////////////////////////////////////////////////////////////////////////
33951 . ////////////////////////////////////////////////////////////////////////////
33952
33953 .chapter "Message processing" "CHAPmsgproc"
33954 .scindex IIDmesproc "message" "general processing"
33955 Exim performs various transformations on the sender and recipient addresses of
33956 all messages that it handles, and also on the messages' header lines. Some of
33957 these are optional and configurable, while others always take place. All of
33958 this processing, except rewriting as a result of routing, and the addition or
33959 removal of header lines while delivering, happens when a message is received,
33960 before it is placed on Exim's queue.
33961
33962 Some of the automatic processing takes place by default only for
33963 &"locally-originated"& messages. This adjective is used to describe messages
33964 that are not received over TCP/IP, but instead are passed to an Exim process on
33965 its standard input. This includes the interactive &"local SMTP"& case that is
33966 set up by the &%-bs%& command line option.
33967
33968 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
33969 or ::1) are not considered to be locally-originated. Exim does not treat the
33970 loopback interface specially in any way.
33971
33972 If you want the loopback interface to be treated specially, you must ensure
33973 that there are appropriate entries in your ACLs.
33974
33975
33976
33977
33978 .section "Submission mode for non-local messages" "SECTsubmodnon"
33979 .cindex "message" "submission"
33980 .cindex "submission mode"
33981 Processing that happens automatically for locally-originated messages (unless
33982 &%suppress_local_fixups%& is set) can also be requested for messages that are
33983 received over TCP/IP. The term &"submission mode"& is used to describe this
33984 state. Submission mode is set by the modifier
33985 .code
33986 control = submission
33987 .endd
33988 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
33989 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
33990 a local submission, and is normally used when the source of the message is
33991 known to be an MUA running on a client host (as opposed to an MTA). For
33992 example, to set submission mode for messages originating on the IPv4 loopback
33993 interface, you could include the following in the MAIL ACL:
33994 .code
33995 warn hosts = 127.0.0.1
33996 control = submission
33997 .endd
33998 .cindex "&%sender_retain%& submission option"
33999 There are some options that can be used when setting submission mode. A slash
34000 is used to separate options. For example:
34001 .code
34002 control = submission/sender_retain
34003 .endd
34004 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
34005 true and &%local_from_check%& false for the current incoming message. The first
34006 of these allows an existing &'Sender:'& header in the message to remain, and
34007 the second suppresses the check to ensure that &'From:'& matches the
34008 authenticated sender. With this setting, Exim still fixes up messages by adding
34009 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
34010 attempt to check sender authenticity in header lines.
34011
34012 When &%sender_retain%& is not set, a submission mode setting may specify a
34013 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
34014 example:
34015 .code
34016 control = submission/domain=some.domain
34017 .endd
34018 The domain may be empty. How this value is used is described in sections
34019 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
34020 that allows you to specify the user's full name for inclusion in a created
34021 &'Sender:'& or &'From:'& header line. For example:
34022 .code
34023 accept authenticated = *
34024 control = submission/domain=wonderland.example/\
34025 name=${lookup {$authenticated_id} \
34026 lsearch {/etc/exim/namelist}}
34027 .endd
34028 Because the name may contain any characters, including slashes, the &%name%&
34029 option must be given last. The remainder of the string is used as the name. For
34030 the example above, if &_/etc/exim/namelist_& contains:
34031 .code
34032 bigegg: Humpty Dumpty
34033 .endd
34034 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
34035 line would be:
34036 .code
34037 Sender: Humpty Dumpty <bigegg@wonderland.example>
34038 .endd
34039 .cindex "return path" "in submission mode"
34040 By default, submission mode forces the return path to the same address as is
34041 used to create the &'Sender:'& header. However, if &%sender_retain%& is
34042 specified, the return path is also left unchanged.
34043
34044 &*Note*&: The changes caused by submission mode take effect after the predata
34045 ACL. This means that any sender checks performed before the fix-ups use the
34046 untrusted sender address specified by the user, not the trusted sender address
34047 specified by submission mode. Although this might be slightly unexpected, it
34048 does mean that you can configure ACL checks to spot that a user is trying to
34049 spoof another's address.
34050
34051 .section "Line endings" "SECTlineendings"
34052 .cindex "line endings"
34053 .cindex "carriage return"
34054 .cindex "linefeed"
34055 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
34056 linefeed) is the line ending for messages transmitted over the Internet using
34057 SMTP over TCP/IP. However, within individual operating systems, different
34058 conventions are used. For example, Unix-like systems use just LF, but others
34059 use CRLF or just CR.
34060
34061 Exim was designed for Unix-like systems, and internally, it stores messages
34062 using the system's convention of a single LF as a line terminator. When
34063 receiving a message, all line endings are translated to this standard format.
34064 Originally, it was thought that programs that passed messages directly to an
34065 MTA within an operating system would use that system's convention. Experience
34066 has shown that this is not the case; for example, there are Unix applications
34067 that use CRLF in this circumstance. For this reason, and for compatibility with
34068 other MTAs, the way Exim handles line endings for all messages is now as
34069 follows:
34070
34071 .ilist
34072 LF not preceded by CR is treated as a line ending.
34073 .next
34074 CR is treated as a line ending; if it is immediately followed by LF, the LF
34075 is ignored.
34076 .next
34077 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
34078 nor a local message in the state where a line containing only a dot is a
34079 terminator.
34080 .next
34081 If a bare CR is encountered within a header line, an extra space is added after
34082 the line terminator so as not to end the header line. The reasoning behind this
34083 is that bare CRs in header lines are most likely either to be mistakes, or
34084 people trying to play silly games.
34085 .next
34086 If the first header line received in a message ends with CRLF, a subsequent
34087 bare LF in a header line is treated in the same way as a bare CR in a header
34088 line.
34089 .endlist
34090
34091
34092
34093
34094
34095 .section "Unqualified addresses" "SECID218"
34096 .cindex "unqualified addresses"
34097 .cindex "address" "qualification"
34098 By default, Exim expects every envelope address it receives from an external
34099 host to be fully qualified. Unqualified addresses cause negative responses to
34100 SMTP commands. However, because SMTP is used as a means of transporting
34101 messages from MUAs running on personal workstations, there is sometimes a
34102 requirement to accept unqualified addresses from specific hosts or IP networks.
34103
34104 Exim has two options that separately control which hosts may send unqualified
34105 sender or recipient addresses in SMTP commands, namely
34106 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
34107 cases, if an unqualified address is accepted, it is qualified by adding the
34108 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
34109
34110 .oindex "&%qualify_domain%&"
34111 .oindex "&%qualify_recipient%&"
34112 Unqualified addresses in header lines are automatically qualified for messages
34113 that are locally originated, unless the &%-bnq%& option is given on the command
34114 line. For messages received over SMTP, unqualified addresses in header lines
34115 are qualified only if unqualified addresses are permitted in SMTP commands. In
34116 other words, such qualification is also controlled by
34117 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
34118
34119
34120
34121
34122 .section "The UUCP From line" "SECID219"
34123 .cindex "&""From""& line"
34124 .cindex "UUCP" "&""From""& line"
34125 .cindex "sender" "address"
34126 .oindex "&%uucp_from_pattern%&"
34127 .oindex "&%uucp_from_sender%&"
34128 .cindex "envelope sender"
34129 .cindex "Sendmail compatibility" "&""From""& line"
34130 Messages that have come from UUCP (and some other applications) often begin
34131 with a line containing the envelope sender and a timestamp, following the word
34132 &"From"&. Examples of two common formats are:
34133 .code
34134 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
34135 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
34136 .endd
34137 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
34138 Exim recognizes such lines at the start of messages that are submitted to it
34139 via the command line (that is, on the standard input). It does not recognize
34140 such lines in incoming SMTP messages, unless the sending host matches
34141 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
34142 and &%ignore_fromline_local%& is set. The recognition is controlled by a
34143 regular expression that is defined by the &%uucp_from_pattern%& option, whose
34144 default value matches the two common cases shown above and puts the address
34145 that follows &"From"& into &$1$&.
34146
34147 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
34148 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
34149 a trusted user, the message's sender address is constructed by expanding the
34150 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
34151 then parsed as an RFC 2822 address. If there is no domain, the local part is
34152 qualified with &%qualify_domain%& unless it is the empty string. However, if
34153 the command line &%-f%& option is used, it overrides the &"From"& line.
34154
34155 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
34156 sender address is not changed. This is also the case for incoming SMTP messages
34157 that are permitted to contain &"From"& lines.
34158
34159 Only one &"From"& line is recognized. If there is more than one, the second is
34160 treated as a data line that starts the body of the message, as it is not valid
34161 as a header line. This also happens if a &"From"& line is present in an
34162 incoming SMTP message from a source that is not permitted to send them.
34163
34164
34165
34166 .section "Resent- header lines" "SECID220"
34167 .cindex "&%Resent-%& header lines"
34168 .cindex "header lines" "Resent-"
34169 RFC 2822 makes provision for sets of header lines starting with the string
34170 &`Resent-`& to be added to a message when it is resent by the original
34171 recipient to somebody else. These headers are &'Resent-Date:'&,
34172 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
34173 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
34174
34175 .blockquote
34176 &'Resent fields are strictly informational. They MUST NOT be used in the normal
34177 processing of replies or other such automatic actions on messages.'&
34178 .endblockquote
34179
34180 This leaves things a bit vague as far as other processing actions such as
34181 address rewriting are concerned. Exim treats &%Resent-%& header lines as
34182 follows:
34183
34184 .ilist
34185 A &'Resent-From:'& line that just contains the login id of the submitting user
34186 is automatically rewritten in the same way as &'From:'& (see below).
34187 .next
34188 If there's a rewriting rule for a particular header line, it is also applied to
34189 &%Resent-%& header lines of the same type. For example, a rule that rewrites
34190 &'From:'& also rewrites &'Resent-From:'&.
34191 .next
34192 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
34193 also removed.
34194 .next
34195 For a locally-submitted message,
34196 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
34197 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
34198 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
34199 included in log lines in this case.
34200 .next
34201 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
34202 &%Resent-%& header lines are present.
34203 .endlist
34204
34205
34206
34207
34208 .section "The Auto-Submitted: header line" "SECID221"
34209 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
34210 includes the header line:
34211 .code
34212 Auto-Submitted: auto-replied
34213 .endd
34214
34215 .section "The Bcc: header line" "SECID222"
34216 .cindex "&'Bcc:'& header line"
34217 If Exim is called with the &%-t%& option, to take recipient addresses from a
34218 message's header, it removes any &'Bcc:'& header line that may exist (after
34219 extracting its addresses). If &%-t%& is not present on the command line, any
34220 existing &'Bcc:'& is not removed.
34221
34222
34223 .section "The Date: header line" "SECID223"
34224 .cindex "&'Date:'& header line"
34225 .cindex "header lines" "Date:"
34226 If a locally-generated or submission-mode message has no &'Date:'& header line,
34227 Exim adds one, using the current date and time, unless the
34228 &%suppress_local_fixups%& control has been specified.
34229
34230 .section "The Delivery-date: header line" "SECID224"
34231 .cindex "&'Delivery-date:'& header line"
34232 .oindex "&%delivery_date_remove%&"
34233 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
34234 set. Exim can be configured to add them to the final delivery of messages. (See
34235 the generic &%delivery_date_add%& transport option.) They should not be present
34236 in messages in transit. If the &%delivery_date_remove%& configuration option is
34237 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
34238 messages.
34239
34240
34241 .section "The Envelope-to: header line" "SECID225"
34242 .cindex "&'Envelope-to:'& header line"
34243 .cindex "header lines" "Envelope-to:"
34244 .oindex "&%envelope_to_remove%&"
34245 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
34246 Exim can be configured to add them to the final delivery of messages. (See the
34247 generic &%envelope_to_add%& transport option.) They should not be present in
34248 messages in transit. If the &%envelope_to_remove%& configuration option is set
34249 (the default), Exim removes &'Envelope-to:'& header lines from incoming
34250 messages.
34251
34252
34253 .section "The From: header line" "SECTthefrohea"
34254 .cindex "&'From:'& header line"
34255 .cindex "header lines" "From:"
34256 .cindex "Sendmail compatibility" "&""From""& line"
34257 .cindex "message" "submission"
34258 .cindex "submission mode"
34259 If a submission-mode message does not contain a &'From:'& header line, Exim
34260 adds one if either of the following conditions is true:
34261
34262 .ilist
34263 The envelope sender address is not empty (that is, this is not a bounce
34264 message). The added header line copies the envelope sender address.
34265 .next
34266 .vindex "&$authenticated_id$&"
34267 The SMTP session is authenticated and &$authenticated_id$& is not empty.
34268 .olist
34269 .vindex "&$qualify_domain$&"
34270 If no domain is specified by the submission control, the local part is
34271 &$authenticated_id$& and the domain is &$qualify_domain$&.
34272 .next
34273 If a non-empty domain is specified by the submission control, the local
34274 part is &$authenticated_id$&, and the domain is the specified domain.
34275 .next
34276 If an empty domain is specified by the submission control,
34277 &$authenticated_id$& is assumed to be the complete address.
34278 .endlist
34279 .endlist
34280
34281 A non-empty envelope sender takes precedence.
34282
34283 If a locally-generated incoming message does not contain a &'From:'& header
34284 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
34285 containing the sender's address. The calling user's login name and full name
34286 are used to construct the address, as described in section &<<SECTconstr>>&.
34287 They are obtained from the password data by calling &[getpwuid()]& (but see the
34288 &%unknown_login%& configuration option). The address is qualified with
34289 &%qualify_domain%&.
34290
34291 For compatibility with Sendmail, if an incoming, non-SMTP message has a
34292 &'From:'& header line containing just the unqualified login name of the calling
34293 user, this is replaced by an address containing the user's login name and full
34294 name as described in section &<<SECTconstr>>&.
34295
34296
34297 .section "The Message-ID: header line" "SECID226"
34298 .cindex "&'Message-ID:'& header line"
34299 .cindex "header lines" "Message-ID:"
34300 .cindex "message" "submission"
34301 .oindex "&%message_id_header_text%&"
34302 If a locally-generated or submission-mode incoming message does not contain a
34303 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
34304 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
34305 to the message. If there are any &'Resent-:'& headers in the message, it
34306 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
34307 message id, preceded by the letter E to ensure it starts with a letter, and
34308 followed by @ and the primary host name. Additional information can be included
34309 in this header line by setting the &%message_id_header_text%& and/or
34310 &%message_id_header_domain%& options.
34311
34312
34313 .section "The Received: header line" "SECID227"
34314 .cindex "&'Received:'& header line"
34315 .cindex "header lines" "Received:"
34316 A &'Received:'& header line is added at the start of every message. The
34317 contents are defined by the &%received_header_text%& configuration option, and
34318 Exim automatically adds a semicolon and a timestamp to the configured string.
34319
34320 The &'Received:'& header is generated as soon as the message's header lines
34321 have been received. At this stage, the timestamp in the &'Received:'& header
34322 line is the time that the message started to be received. This is the value
34323 that is seen by the DATA ACL and by the &[local_scan()]& function.
34324
34325 Once a message is accepted, the timestamp in the &'Received:'& header line is
34326 changed to the time of acceptance, which is (apart from a small delay while the
34327 -H spool file is written) the earliest time at which delivery could start.
34328
34329
34330 .section "The References: header line" "SECID228"
34331 .cindex "&'References:'& header line"
34332 .cindex "header lines" "References:"
34333 Messages created by the &(autoreply)& transport include a &'References:'&
34334 header line. This is constructed according to the rules that are described in
34335 section 3.64 of RFC 2822 (which states that replies should contain such a
34336 header line), and section 3.14 of RFC 3834 (which states that automatic
34337 responses are not different in this respect). However, because some mail
34338 processing software does not cope well with very long header lines, no more
34339 than 12 message IDs are copied from the &'References:'& header line in the
34340 incoming message. If there are more than 12, the first one and then the final
34341 11 are copied, before adding the message ID of the incoming message.
34342
34343
34344
34345 .section "The Return-path: header line" "SECID229"
34346 .cindex "&'Return-path:'& header line"
34347 .cindex "header lines" "Return-path:"
34348 .oindex "&%return_path_remove%&"
34349 &'Return-path:'& header lines are defined as something an MTA may insert when
34350 it does the final delivery of messages. (See the generic &%return_path_add%&
34351 transport option.) Therefore, they should not be present in messages in
34352 transit. If the &%return_path_remove%& configuration option is set (the
34353 default), Exim removes &'Return-path:'& header lines from incoming messages.
34354
34355
34356
34357 .section "The Sender: header line" "SECTthesenhea"
34358 .cindex "&'Sender:'& header line"
34359 .cindex "message" "submission"
34360 .cindex "header lines" "Sender:"
34361 For a locally-originated message from an untrusted user, Exim may remove an
34362 existing &'Sender:'& header line, and it may add a new one. You can modify
34363 these actions by setting the &%local_sender_retain%& option true, the
34364 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
34365 control setting.
34366
34367 When a local message is received from an untrusted user and
34368 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
34369 control has not been set, a check is made to see if the address given in the
34370 &'From:'& header line is the correct (local) sender of the message. The address
34371 that is expected has the login name as the local part and the value of
34372 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
34373 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
34374 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
34375 line is added to the message.
34376
34377 If you set &%local_from_check%& false, this checking does not occur. However,
34378 the removal of an existing &'Sender:'& line still happens, unless you also set
34379 &%local_sender_retain%& to be true. It is not possible to set both of these
34380 options true at the same time.
34381
34382 .cindex "submission mode"
34383 By default, no processing of &'Sender:'& header lines is done for messages
34384 received over TCP/IP or for messages submitted by trusted users. However, when
34385 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
34386 not specified on the submission control, the following processing takes place:
34387
34388 .vindex "&$authenticated_id$&"
34389 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
34390 authenticated, and &$authenticated_id$& is not empty, a sender address is
34391 created as follows:
34392
34393 .ilist
34394 .vindex "&$qualify_domain$&"
34395 If no domain is specified by the submission control, the local part is
34396 &$authenticated_id$& and the domain is &$qualify_domain$&.
34397 .next
34398 If a non-empty domain is specified by the submission control, the local part
34399 is &$authenticated_id$&, and the domain is the specified domain.
34400 .next
34401 If an empty domain is specified by the submission control,
34402 &$authenticated_id$& is assumed to be the complete address.
34403 .endlist
34404
34405 This address is compared with the address in the &'From:'& header line. If they
34406 are different, a &'Sender:'& header line containing the created address is
34407 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
34408 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
34409
34410 .cindex "return path" "created from &'Sender:'&"
34411 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
34412 the message (the envelope sender address) is changed to be the same address,
34413 except in the case of submission mode when &%sender_retain%& is specified.
34414
34415
34416
34417 .section "Adding and removing header lines in routers and transports" &&&
34418 "SECTheadersaddrem"
34419 .cindex "header lines" "adding; in router or transport"
34420 .cindex "header lines" "removing; in router or transport"
34421 When a message is delivered, the addition and removal of header lines can be
34422 specified in a system filter, or on any of the routers and transports that
34423 process the message. Section &<<SECTaddremheasys>>& contains details about
34424 modifying headers in a system filter. Header lines can also be added in an ACL
34425 as a message is received (see section &<<SECTaddheadacl>>&).
34426
34427 In contrast to what happens in a system filter, header modifications that are
34428 specified on routers and transports apply only to the particular recipient
34429 addresses that are being processed by those routers and transports. These
34430 changes do not actually take place until a copy of the message is being
34431 transported. Therefore, they do not affect the basic set of header lines, and
34432 they do not affect the values of the variables that refer to header lines.
34433
34434 &*Note*&: In particular, this means that any expansions in the configuration of
34435 the transport cannot refer to the modified header lines, because such
34436 expansions all occur before the message is actually transported.
34437
34438 For both routers and transports, the argument of a &%headers_add%&
34439 option must be in the form of one or more RFC 2822 header lines, separated by
34440 newlines (coded as &"\n"&). For example:
34441 .code
34442 headers_add = X-added-header: added by $primary_hostname\n\
34443 X-added-second: another added header line
34444 .endd
34445 Exim does not check the syntax of these added header lines.
34446
34447 Multiple &%headers_add%& options for a single router or transport can be
34448 specified; the values will append to a single list of header lines.
34449 Each header-line is separately expanded.
34450
34451 The argument of a &%headers_remove%& option must consist of a colon-separated
34452 list of header names. This is confusing, because header names themselves are
34453 often terminated by colons. In this case, the colons are the list separators,
34454 not part of the names. For example:
34455 .code
34456 headers_remove = return-receipt-to:acknowledge-to
34457 .endd
34458
34459 Multiple &%headers_remove%& options for a single router or transport can be
34460 specified; the arguments will append to a single header-names list.
34461 Each item is separately expanded.
34462 Note that colons in complex expansions which are used to
34463 form all or part of a &%headers_remove%& list
34464 will act as list separators.
34465
34466 When &%headers_add%& or &%headers_remove%& is specified on a router,
34467 items are expanded at routing time,
34468 and then associated with all addresses that are
34469 accepted by that router, and also with any new addresses that it generates. If
34470 an address passes through several routers as a result of aliasing or
34471 forwarding, the changes are cumulative.
34472
34473 .oindex "&%unseen%&"
34474 However, this does not apply to multiple routers that result from the use of
34475 the &%unseen%& option. Any header modifications that were specified by the
34476 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
34477
34478 Addresses that end up with different &%headers_add%& or &%headers_remove%&
34479 settings cannot be delivered together in a batch, so a transport is always
34480 dealing with a set of addresses that have the same header-processing
34481 requirements.
34482
34483 The transport starts by writing the original set of header lines that arrived
34484 with the message, possibly modified by the system filter. As it writes out
34485 these lines, it consults the list of header names that were attached to the
34486 recipient address(es) by &%headers_remove%& options in routers, and it also
34487 consults the transport's own &%headers_remove%& option. Header lines whose
34488 names are on either of these lists are not written out. If there are multiple
34489 instances of any listed header, they are all skipped.
34490
34491 After the remaining original header lines have been written, new header
34492 lines that were specified by routers' &%headers_add%& options are written, in
34493 the order in which they were attached to the address. These are followed by any
34494 header lines specified by the transport's &%headers_add%& option.
34495
34496 This way of handling header line modifications in routers and transports has
34497 the following consequences:
34498
34499 .ilist
34500 The original set of header lines, possibly modified by the system filter,
34501 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
34502 to it, at all times.
34503 .next
34504 Header lines that are added by a router's
34505 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
34506 expansion syntax in subsequent routers or the transport.
34507 .next
34508 Conversely, header lines that are specified for removal by &%headers_remove%&
34509 in a router remain visible to subsequent routers and the transport.
34510 .next
34511 Headers added to an address by &%headers_add%& in a router cannot be removed by
34512 a later router or by a transport.
34513 .next
34514 An added header can refer to the contents of an original header that is to be
34515 removed, even it has the same name as the added header. For example:
34516 .code
34517 headers_remove = subject
34518 headers_add = Subject: new subject (was: $h_subject:)
34519 .endd
34520 .endlist
34521
34522 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
34523 for a &(redirect)& router that has the &%one_time%& option set.
34524
34525
34526
34527
34528
34529 .section "Constructed addresses" "SECTconstr"
34530 .cindex "address" "constructed"
34531 .cindex "constructed address"
34532 When Exim constructs a sender address for a locally-generated message, it uses
34533 the form
34534 .display
34535 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
34536 .endd
34537 For example:
34538 .code
34539 Zaphod Beeblebrox <zaphod@end.univ.example>
34540 .endd
34541 The user name is obtained from the &%-F%& command line option if set, or
34542 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
34543 &"gecos"& field from the password entry. If the &"gecos"& field contains an
34544 ampersand character, this is replaced by the login name with the first letter
34545 upper cased, as is conventional in a number of operating systems. See the
34546 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
34547 The &%unknown_username%& option can be used to specify user names in cases when
34548 there is no password file entry.
34549
34550 .cindex "RFC 2047"
34551 In all cases, the user name is made to conform to RFC 2822 by quoting all or
34552 parts of it if necessary. In addition, if it contains any non-printing
34553 characters, it is encoded as described in RFC 2047, which defines a way of
34554 including non-ASCII characters in header lines. The value of the
34555 &%headers_charset%& option specifies the name of the encoding that is used (the
34556 characters are assumed to be in this encoding). The setting of
34557 &%print_topbitchars%& controls whether characters with the top bit set (that
34558 is, with codes greater than 127) count as printing characters or not.
34559
34560
34561
34562 .section "Case of local parts" "SECID230"
34563 .cindex "case of local parts"
34564 .cindex "local part" "case of"
34565 RFC 2822 states that the case of letters in the local parts of addresses cannot
34566 be assumed to be non-significant. Exim preserves the case of local parts of
34567 addresses, but by default it uses a lower-cased form when it is routing,
34568 because on most Unix systems, usernames are in lower case and case-insensitive
34569 routing is required. However, any particular router can be made to use the
34570 original case for local parts by setting the &%caseful_local_part%& generic
34571 router option.
34572
34573 .cindex "mixed-case login names"
34574 If you must have mixed-case user names on your system, the best way to proceed,
34575 assuming you want case-independent handling of incoming email, is to set up
34576 your first router to convert incoming local parts in your domains to the
34577 correct case by means of a file lookup. For example:
34578 .code
34579 correct_case:
34580 driver = redirect
34581 domains = +local_domains
34582 data = ${lookup{$local_part}cdb\
34583 {/etc/usercased.cdb}{$value}fail}\
34584 @$domain
34585 .endd
34586 For this router, the local part is forced to lower case by the default action
34587 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
34588 up a new local part in the correct case. If you then set &%caseful_local_part%&
34589 on any subsequent routers which process your domains, they will operate on
34590 local parts with the correct case in a case-sensitive manner.
34591
34592
34593
34594 .section "Dots in local parts" "SECID231"
34595 .cindex "dot" "in local part"
34596 .cindex "local part" "dots in"
34597 RFC 2822 forbids empty components in local parts. That is, an unquoted local
34598 part may not begin or end with a dot, nor have two consecutive dots in the
34599 middle. However, it seems that many MTAs do not enforce this, so Exim permits
34600 empty components for compatibility.
34601
34602
34603
34604 .section "Rewriting addresses" "SECID232"
34605 .cindex "rewriting" "addresses"
34606 Rewriting of sender and recipient addresses, and addresses in headers, can
34607 happen automatically, or as the result of configuration options, as described
34608 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
34609 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
34610
34611 Automatic rewriting includes qualification, as mentioned above. The other case
34612 in which it can happen is when an incomplete non-local domain is given. The
34613 routing process may cause this to be expanded into the full domain name. For
34614 example, a header such as
34615 .code
34616 To: hare@teaparty
34617 .endd
34618 might get rewritten as
34619 .code
34620 To: hare@teaparty.wonderland.fict.example
34621 .endd
34622 Rewriting as a result of routing is the one kind of message processing that
34623 does not happen at input time, as it cannot be done until the address has
34624 been routed.
34625
34626 Strictly, one should not do &'any'& deliveries of a message until all its
34627 addresses have been routed, in case any of the headers get changed as a
34628 result of routing. However, doing this in practice would hold up many
34629 deliveries for unreasonable amounts of time, just because one address could not
34630 immediately be routed. Exim therefore does not delay other deliveries when
34631 routing of one or more addresses is deferred.
34632 .ecindex IIDmesproc
34633
34634
34635
34636 . ////////////////////////////////////////////////////////////////////////////
34637 . ////////////////////////////////////////////////////////////////////////////
34638
34639 .chapter "SMTP processing" "CHAPSMTP"
34640 .scindex IIDsmtpproc1 "SMTP" "processing details"
34641 .scindex IIDsmtpproc2 "LMTP" "processing details"
34642 Exim supports a number of different ways of using the SMTP protocol, and its
34643 LMTP variant, which is an interactive protocol for transferring messages into a
34644 closed mail store application. This chapter contains details of how SMTP is
34645 processed. For incoming mail, the following are available:
34646
34647 .ilist
34648 SMTP over TCP/IP (Exim daemon or &'inetd'&);
34649 .next
34650 SMTP over the standard input and output (the &%-bs%& option);
34651 .next
34652 Batched SMTP on the standard input (the &%-bS%& option).
34653 .endlist
34654
34655 For mail delivery, the following are available:
34656
34657 .ilist
34658 SMTP over TCP/IP (the &(smtp)& transport);
34659 .next
34660 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
34661 &"lmtp"&);
34662 .next
34663 LMTP over a pipe to a process running in the local host (the &(lmtp)&
34664 transport);
34665 .next
34666 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
34667 the &%use_bsmtp%& option set).
34668 .endlist
34669
34670 &'Batched SMTP'& is the name for a process in which batches of messages are
34671 stored in or read from files (or pipes), in a format in which SMTP commands are
34672 used to contain the envelope information.
34673
34674
34675
34676 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
34677 .cindex "SMTP" "outgoing over TCP/IP"
34678 .cindex "outgoing SMTP over TCP/IP"
34679 .cindex "LMTP" "over TCP/IP"
34680 .cindex "outgoing LMTP over TCP/IP"
34681 .cindex "EHLO"
34682 .cindex "HELO"
34683 .cindex "SIZE option on MAIL command"
34684 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
34685 The &%protocol%& option selects which protocol is to be used, but the actual
34686 processing is the same in both cases.
34687
34688 If, in response to its EHLO command, Exim is told that the SIZE
34689 parameter is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
34690 command. The value of <&'n'&> is the message size plus the value of the
34691 &%size_addition%& option (default 1024) to allow for additions to the message
34692 such as per-transport header lines, or changes made in a
34693 .cindex "transport" "filter"
34694 .cindex "filter" "transport filter"
34695 transport filter. If &%size_addition%& is set negative, the use of SIZE is
34696 suppressed.
34697
34698 If the remote server advertises support for PIPELINING, Exim uses the
34699 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
34700 required for the transaction.
34701
34702 If the remote server advertises support for the STARTTLS command, and Exim
34703 was built to support TLS encryption, it tries to start a TLS session unless the
34704 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
34705 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
34706 is called for verification.
34707
34708 If the remote server advertises support for the AUTH command, Exim scans
34709 the authenticators configuration for any suitable client settings, as described
34710 in chapter &<<CHAPSMTPAUTH>>&.
34711
34712 .cindex "carriage return"
34713 .cindex "linefeed"
34714 Responses from the remote host are supposed to be terminated by CR followed by
34715 LF. However, there are known to be hosts that do not send CR characters, so in
34716 order to be able to interwork with such hosts, Exim treats LF on its own as a
34717 line terminator.
34718
34719 If a message contains a number of different addresses, all those with the same
34720 characteristics (for example, the same envelope sender) that resolve to the
34721 same set of hosts, in the same order, are sent in a single SMTP transaction,
34722 even if they are for different domains, unless there are more than the setting
34723 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
34724 they are split into groups containing no more than &%max_rcpt%&s addresses
34725 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
34726 in parallel sessions. The order of hosts with identical MX values is not
34727 significant when checking whether addresses can be batched in this way.
34728
34729 When the &(smtp)& transport suffers a temporary failure that is not
34730 message-related, Exim updates its transport-specific database, which contains
34731 records indexed by host name that remember which messages are waiting for each
34732 particular host. It also updates the retry database with new retry times.
34733
34734 .cindex "hints database" "retry keys"
34735 Exim's retry hints are based on host name plus IP address, so if one address of
34736 a multi-homed host is broken, it will soon be skipped most of the time.
34737 See the next section for more detail about error handling.
34738
34739 .cindex "SMTP" "passed connection"
34740 .cindex "SMTP" "batching over TCP/IP"
34741 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
34742 looks in the hints database for the transport to see if there are any queued
34743 messages waiting for the host to which it is connected. If it finds one, it
34744 creates a new Exim process using the &%-MC%& option (which can only be used by
34745 a process running as root or the Exim user) and passes the TCP/IP socket to it
34746 so that it can deliver another message using the same socket. The new process
34747 does only those deliveries that are routed to the connected host, and may in
34748 turn pass the socket on to a third process, and so on.
34749
34750 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
34751 limit the number of messages sent down a single TCP/IP connection.
34752
34753 .cindex "asterisk" "after IP address"
34754 The second and subsequent messages delivered down an existing connection are
34755 identified in the main log by the addition of an asterisk after the closing
34756 square bracket of the IP address.
34757
34758
34759
34760
34761 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
34762 .cindex "error" "in outgoing SMTP"
34763 .cindex "SMTP" "errors in outgoing"
34764 .cindex "host" "error"
34765 Three different kinds of error are recognized for outgoing SMTP: host errors,
34766 message errors, and recipient errors.
34767
34768 .vlist
34769 .vitem "&*Host errors*&"
34770 A host error is not associated with a particular message or with a
34771 particular recipient of a message. The host errors are:
34772
34773 .ilist
34774 Connection refused or timed out,
34775 .next
34776 Any error response code on connection,
34777 .next
34778 Any error response code to EHLO or HELO,
34779 .next
34780 Loss of connection at any time, except after &"."&,
34781 .next
34782 I/O errors at any time,
34783 .next
34784 Timeouts during the session, other than in response to MAIL, RCPT or
34785 the &"."& at the end of the data.
34786 .endlist ilist
34787
34788 For a host error, a permanent error response on connection, or in response to
34789 EHLO, causes all addresses routed to the host to be failed. Any other host
34790 error causes all addresses to be deferred, and retry data to be created for the
34791 host. It is not tried again, for any message, until its retry time arrives. If
34792 the current set of addresses are not all delivered in this run (to some
34793 alternative host), the message is added to the list of those waiting for this
34794 host, so if it is still undelivered when a subsequent successful delivery is
34795 made to the host, it will be sent down the same SMTP connection.
34796
34797 .vitem "&*Message errors*&"
34798 .cindex "message" "error"
34799 A message error is associated with a particular message when sent to a
34800 particular host, but not with a particular recipient of the message. The
34801 message errors are:
34802
34803 .ilist
34804 Any error response code to MAIL, DATA, or the &"."& that terminates
34805 the data,
34806 .next
34807 Timeout after MAIL,
34808 .next
34809 Timeout or loss of connection after the &"."& that terminates the data. A
34810 timeout after the DATA command itself is treated as a host error, as is loss of
34811 connection at any other time.
34812 .endlist ilist
34813
34814 For a message error, a permanent error response (5&'xx'&) causes all addresses
34815 to be failed, and a delivery error report to be returned to the sender. A
34816 temporary error response (4&'xx'&), or one of the timeouts, causes all
34817 addresses to be deferred. Retry data is not created for the host, but instead,
34818 a retry record for the combination of host plus message id is created. The
34819 message is not added to the list of those waiting for this host. This ensures
34820 that the failing message will not be sent to this host again until the retry
34821 time arrives. However, other messages that are routed to the host are not
34822 affected, so if it is some property of the message that is causing the error,
34823 it will not stop the delivery of other mail.
34824
34825 If the remote host specified support for the SIZE parameter in its response
34826 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
34827 over-large message will cause a message error because the error arrives as a
34828 response to MAIL.
34829
34830 .vitem "&*Recipient errors*&"
34831 .cindex "recipient" "error"
34832 A recipient error is associated with a particular recipient of a message. The
34833 recipient errors are:
34834
34835 .ilist
34836 Any error response to RCPT,
34837 .next
34838 Timeout after RCPT.
34839 .endlist
34840
34841 For a recipient error, a permanent error response (5&'xx'&) causes the
34842 recipient address to be failed, and a bounce message to be returned to the
34843 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
34844 address to be deferred, and routing retry data to be created for it. This is
34845 used to delay processing of the address in subsequent queue runs, until its
34846 routing retry time arrives. This applies to all messages, but because it
34847 operates only in queue runs, one attempt will be made to deliver a new message
34848 to the failing address before the delay starts to operate. This ensures that,
34849 if the failure is really related to the message rather than the recipient
34850 (&"message too big for this recipient"& is a possible example), other messages
34851 have a chance of getting delivered. If a delivery to the address does succeed,
34852 the retry information gets cleared, so all stuck messages get tried again, and
34853 the retry clock is reset.
34854
34855 The message is not added to the list of those waiting for this host. Use of the
34856 host for other messages is unaffected, and except in the case of a timeout,
34857 other recipients are processed independently, and may be successfully delivered
34858 in the current SMTP session. After a timeout it is of course impossible to
34859 proceed with the session, so all addresses get deferred. However, those other
34860 than the one that failed do not suffer any subsequent retry delays. Therefore,
34861 if one recipient is causing trouble, the others have a chance of getting
34862 through when a subsequent delivery attempt occurs before the failing
34863 recipient's retry time.
34864 .endlist
34865
34866 In all cases, if there are other hosts (or IP addresses) available for the
34867 current set of addresses (for example, from multiple MX records), they are
34868 tried in this run for any undelivered addresses, subject of course to their
34869 own retry data. In other words, recipient error retry data does not take effect
34870 until the next delivery attempt.
34871
34872 Some hosts have been observed to give temporary error responses to every
34873 MAIL command at certain times (&"insufficient space"& has been seen). It
34874 would be nice if such circumstances could be recognized, and defer data for the
34875 host itself created, but this is not possible within the current Exim design.
34876 What actually happens is that retry data for every (host, message) combination
34877 is created.
34878
34879 The reason that timeouts after MAIL and RCPT are treated specially is that
34880 these can sometimes arise as a result of the remote host's verification
34881 procedures. Exim makes this assumption, and treats them as if a temporary error
34882 response had been received. A timeout after &"."& is treated specially because
34883 it is known that some broken implementations fail to recognize the end of the
34884 message if the last character of the last line is a binary zero. Thus, it is
34885 helpful to treat this case as a message error.
34886
34887 Timeouts at other times are treated as host errors, assuming a problem with the
34888 host, or the connection to it. If a timeout after MAIL, RCPT,
34889 or &"."& is really a connection problem, the assumption is that at the next try
34890 the timeout is likely to occur at some other point in the dialogue, causing it
34891 then to be treated as a host error.
34892
34893 There is experimental evidence that some MTAs drop the connection after the
34894 terminating &"."& if they do not like the contents of the message for some
34895 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
34896 should be given. That is why Exim treats this case as a message rather than a
34897 host error, in order not to delay other messages to the same host.
34898
34899
34900
34901
34902 .section "Incoming SMTP messages over TCP/IP" "SECID233"
34903 .cindex "SMTP" "incoming over TCP/IP"
34904 .cindex "incoming SMTP over TCP/IP"
34905 .cindex "inetd"
34906 .cindex "daemon"
34907 Incoming SMTP messages can be accepted in one of two ways: by running a
34908 listening daemon, or by using &'inetd'&. In the latter case, the entry in
34909 &_/etc/inetd.conf_& should be like this:
34910 .code
34911 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
34912 .endd
34913 Exim distinguishes between this case and the case of a locally running user
34914 agent using the &%-bs%& option by checking whether or not the standard input is
34915 a socket. When it is, either the port must be privileged (less than 1024), or
34916 the caller must be root or the Exim user. If any other user passes a socket
34917 with an unprivileged port number, Exim prints a message on the standard error
34918 stream and exits with an error code.
34919
34920 By default, Exim does not make a log entry when a remote host connects or
34921 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
34922 unexpected. It can be made to write such log entries by setting the
34923 &%smtp_connection%& log selector.
34924
34925 .cindex "carriage return"
34926 .cindex "linefeed"
34927 Commands from the remote host are supposed to be terminated by CR followed by
34928 LF. However, there are known to be hosts that do not send CR characters. In
34929 order to be able to interwork with such hosts, Exim treats LF on its own as a
34930 line terminator.
34931 Furthermore, because common code is used for receiving messages from all
34932 sources, a CR on its own is also interpreted as a line terminator. However, the
34933 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
34934
34935 .cindex "EHLO" "invalid data"
34936 .cindex "HELO" "invalid data"
34937 One area that sometimes gives rise to problems concerns the EHLO or
34938 HELO commands. Some clients send syntactically invalid versions of these
34939 commands, which Exim rejects by default. (This is nothing to do with verifying
34940 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
34941 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
34942 match the broken hosts that send invalid commands.
34943
34944 .cindex "SIZE option on MAIL command"
34945 .cindex "MAIL" "SIZE option"
34946 The amount of disk space available is checked whenever SIZE is received on
34947 a MAIL command, independently of whether &%message_size_limit%& or
34948 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
34949 false. A temporary error is given if there is not enough space. If
34950 &%check_spool_space%& is set, the check is for that amount of space plus the
34951 value given with SIZE, that is, it checks that the addition of the incoming
34952 message will not reduce the space below the threshold.
34953
34954 When a message is successfully received, Exim includes the local message id in
34955 its response to the final &"."& that terminates the data. If the remote host
34956 logs this text it can help with tracing what has happened to a message.
34957
34958 The Exim daemon can limit the number of simultaneous incoming connections it is
34959 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
34960 number of simultaneous incoming connections from a single remote host (see the
34961 &%smtp_accept_max_per_host%& option). Additional connection attempts are
34962 rejected using the SMTP temporary error code 421.
34963
34964 The Exim daemon does not rely on the SIGCHLD signal to detect when a
34965 subprocess has finished, as this can get lost at busy times. Instead, it looks
34966 for completed subprocesses every time it wakes up. Provided there are other
34967 things happening (new incoming calls, starts of queue runs), completed
34968 processes will be noticed and tidied away. On very quiet systems you may
34969 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
34970 it will be noticed when the daemon next wakes up.
34971
34972 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
34973 and can also be set up to reject SMTP calls from non-reserved hosts at times of
34974 high system load &-- for details see the &%smtp_accept_reserve%&,
34975 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
34976 applies in both the daemon and &'inetd'& cases.
34977
34978 Exim normally starts a delivery process for each message received, though this
34979 can be varied by means of the &%-odq%& command line option and the
34980 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
34981 number of simultaneously running delivery processes started in this way from
34982 SMTP input can be limited by the &%smtp_accept_queue%& and
34983 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
34984 subsequently received messages are just put on the input queue without starting
34985 a delivery process.
34986
34987 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
34988 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
34989 started up from the &'inetd'& daemon, because in that case each connection is
34990 handled by an entirely independent Exim process. Control by load average is,
34991 however, available with &'inetd'&.
34992
34993 Exim can be configured to verify addresses in incoming SMTP commands as they
34994 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
34995 to rewrite addresses at this time &-- before any syntax checking is done. See
34996 section &<<SECTrewriteS>>&.
34997
34998 Exim can also be configured to limit the rate at which a client host submits
34999 MAIL and RCPT commands in a single SMTP session. See the
35000 &%smtp_ratelimit_hosts%& option.
35001
35002
35003
35004 .section "Unrecognized SMTP commands" "SECID234"
35005 .cindex "SMTP" "unrecognized commands"
35006 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
35007 commands during a single SMTP connection, it drops the connection after sending
35008 the error response to the last command. The default value for
35009 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
35010 abuse that subvert web servers into making connections to SMTP ports; in these
35011 circumstances, a number of non-SMTP lines are sent first.
35012
35013
35014 .section "Syntax and protocol errors in SMTP commands" "SECID235"
35015 .cindex "SMTP" "syntax errors"
35016 .cindex "SMTP" "protocol errors"
35017 A syntax error is detected if an SMTP command is recognized, but there is
35018 something syntactically wrong with its data, for example, a malformed email
35019 address in a RCPT command. Protocol errors include invalid command
35020 sequencing such as RCPT before MAIL. If Exim receives more than
35021 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
35022 drops the connection after sending the error response to the last command. The
35023 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
35024 broken clients that loop sending bad commands (yes, it has been seen).
35025
35026
35027
35028 .section "Use of non-mail SMTP commands" "SECID236"
35029 .cindex "SMTP" "non-mail commands"
35030 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
35031 DATA. Exim counts such commands, and drops the connection if there are too
35032 many of them in a single SMTP session. This action catches some
35033 denial-of-service attempts and things like repeated failing AUTHs, or a mad
35034 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
35035 defines what &"too many"& means. Its default value is 10.
35036
35037 When a new message is expected, one occurrence of RSET is not counted. This
35038 allows a client to send one RSET between messages (this is not necessary,
35039 but some clients do it). Exim also allows one uncounted occurrence of HELO
35040 or EHLO, and one occurrence of STARTTLS between messages. After
35041 starting up a TLS session, another EHLO is expected, and so it too is not
35042 counted.
35043
35044 The first occurrence of AUTH in a connection, or immediately following
35045 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
35046 RCPT, DATA, and QUIT are counted.
35047
35048 You can control which hosts are subject to the limit set by
35049 &%smtp_accept_max_nonmail%& by setting
35050 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
35051 the limit apply to all hosts. This option means that you can exclude any
35052 specific badly-behaved hosts that you have to live with.
35053
35054
35055
35056
35057 .section "The VRFY and EXPN commands" "SECID237"
35058 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
35059 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
35060 appropriate) in order to decide whether the command should be accepted or not.
35061
35062 .cindex "VRFY" "processing"
35063 When no ACL is defined for VRFY, or if it rejects without
35064 setting an explicit response code, the command is accepted
35065 (with a 252 SMTP response code)
35066 in order to support awkward clients that do a VRFY before every RCPT.
35067 When VRFY is accepted, it runs exactly the same code as when Exim is
35068 called with the &%-bv%& option, and returns 250/451/550
35069 SMTP response codes.
35070
35071 .cindex "EXPN" "processing"
35072 If no ACL for EXPN is defined, the command is rejected.
35073 When EXPN is accepted, a single-level expansion of the address is done.
35074 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
35075 than a verification (the &%-bv%& option). If an unqualified local part is given
35076 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
35077 of VRFY and EXPN commands are logged on the main and reject logs, and
35078 VRFY verification failures are logged on the main log for consistency with
35079 RCPT failures.
35080
35081
35082
35083 .section "The ETRN command" "SECTETRN"
35084 .cindex "ETRN" "processing"
35085 RFC 1985 describes an SMTP command called ETRN that is designed to
35086 overcome the security problems of the TURN command (which has fallen into
35087 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
35088 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
35089 should be accepted or not. If no ACL is defined, the command is rejected.
35090
35091 The ETRN command is concerned with &"releasing"& messages that are awaiting
35092 delivery to certain hosts. As Exim does not organize its message queue by host,
35093 the only form of ETRN that is supported by default is the one where the
35094 text starts with the &"#"& prefix, in which case the remainder of the text is
35095 specific to the SMTP server. A valid ETRN command causes a run of Exim with
35096 the &%-R%& option to happen, with the remainder of the ETRN text as its
35097 argument. For example,
35098 .code
35099 ETRN #brigadoon
35100 .endd
35101 runs the command
35102 .code
35103 exim -R brigadoon
35104 .endd
35105 which causes a delivery attempt on all messages with undelivered addresses
35106 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
35107 default), Exim prevents the simultaneous execution of more than one queue run
35108 for the same argument string as a result of an ETRN command. This stops
35109 a misbehaving client from starting more than one queue runner at once.
35110
35111 .cindex "hints database" "ETRN serialization"
35112 Exim implements the serialization by means of a hints database in which a
35113 record is written whenever a process is started by ETRN, and deleted when
35114 the process completes. However, Exim does not keep the SMTP session waiting for
35115 the ETRN process to complete. Once ETRN is accepted, the client is sent
35116 a &"success"& return code. Obviously there is scope for hints records to get
35117 left lying around if there is a system or program crash. To guard against this,
35118 Exim ignores any records that are more than six hours old.
35119
35120 .oindex "&%smtp_etrn_command%&"
35121 For more control over what ETRN does, the &%smtp_etrn_command%& option can
35122 used. This specifies a command that is run whenever ETRN is received,
35123 whatever the form of its argument. For
35124 example:
35125 .code
35126 smtp_etrn_command = /etc/etrn_command $domain \
35127 $sender_host_address
35128 .endd
35129 .vindex "&$domain$&"
35130 The string is split up into arguments which are independently expanded. The
35131 expansion variable &$domain$& is set to the argument of the ETRN command,
35132 and no syntax checking is done on the contents of this argument. Exim does not
35133 wait for the command to complete, so its status code is not checked. Exim runs
35134 under its own uid and gid when receiving incoming SMTP, so it is not possible
35135 for it to change them before running the command.
35136
35137
35138
35139 .section "Incoming local SMTP" "SECID238"
35140 .cindex "SMTP" "local incoming"
35141 Some user agents use SMTP to pass messages to their local MTA using the
35142 standard input and output, as opposed to passing the envelope on the command
35143 line and writing the message to the standard input. This is supported by the
35144 &%-bs%& option. This form of SMTP is handled in the same way as incoming
35145 messages over TCP/IP (including the use of ACLs), except that the envelope
35146 sender given in a MAIL command is ignored unless the caller is trusted. In
35147 an ACL you can detect this form of SMTP input by testing for an empty host
35148 identification. It is common to have this as the first line in the ACL that
35149 runs for RCPT commands:
35150 .code
35151 accept hosts = :
35152 .endd
35153 This accepts SMTP messages from local processes without doing any other tests.
35154
35155
35156
35157 .section "Outgoing batched SMTP" "SECTbatchSMTP"
35158 .cindex "SMTP" "batched outgoing"
35159 .cindex "batched SMTP output"
35160 Both the &(appendfile)& and &(pipe)& transports can be used for handling
35161 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
35162 be output in BSMTP format. No SMTP responses are possible for this form of
35163 delivery. All it is doing is using SMTP commands as a way of transmitting the
35164 envelope along with the message.
35165
35166 The message is written to the file or pipe preceded by the SMTP commands
35167 MAIL and RCPT, and followed by a line containing a single dot. Lines in
35168 the message that start with a dot have an extra dot added. The SMTP command
35169 HELO is not normally used. If it is required, the &%message_prefix%& option
35170 can be used to specify it.
35171
35172 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
35173 one recipient address at a time by default. However, you can arrange for them
35174 to handle several addresses at once by setting the &%batch_max%& option. When
35175 this is done for BSMTP, messages may contain multiple RCPT commands. See
35176 chapter &<<CHAPbatching>>& for more details.
35177
35178 .vindex "&$host$&"
35179 When one or more addresses are routed to a BSMTP transport by a router that
35180 sets up a host list, the name of the first host on the list is available to the
35181 transport in the variable &$host$&. Here is an example of such a transport and
35182 router:
35183 .code
35184 begin routers
35185 route_append:
35186 driver = manualroute
35187 transport = smtp_appendfile
35188 route_list = domain.example batch.host.example
35189
35190 begin transports
35191 smtp_appendfile:
35192 driver = appendfile
35193 directory = /var/bsmtp/$host
35194 batch_max = 1000
35195 use_bsmtp
35196 user = exim
35197 .endd
35198 This causes messages addressed to &'domain.example'& to be written in BSMTP
35199 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
35200 message (unless there are more than 1000 recipients).
35201
35202
35203
35204 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
35205 .cindex "SMTP" "batched incoming"
35206 .cindex "batched SMTP input"
35207 The &%-bS%& command line option causes Exim to accept one or more messages by
35208 reading SMTP on the standard input, but to generate no responses. If the caller
35209 is trusted, the senders in the MAIL commands are believed; otherwise the
35210 sender is always the caller of Exim. Unqualified senders and receivers are not
35211 rejected (there seems little point) but instead just get qualified. HELO
35212 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
35213 as NOOP; QUIT quits.
35214
35215 Minimal policy checking is done for BSMTP input. Only the non-SMTP
35216 ACL is run in the same way as for non-SMTP local input.
35217
35218 If an error is detected while reading a message, including a missing &"."& at
35219 the end, Exim gives up immediately. It writes details of the error to the
35220 standard output in a stylized way that the calling program should be able to
35221 make some use of automatically, for example:
35222 .code
35223 554 Unexpected end of file
35224 Transaction started in line 10
35225 Error detected in line 14
35226 .endd
35227 It writes a more verbose version, for human consumption, to the standard error
35228 file, for example:
35229 .code
35230 An error was detected while processing a file of BSMTP input.
35231 The error message was:
35232
35233 501 '>' missing at end of address
35234
35235 The SMTP transaction started in line 10.
35236 The error was detected in line 12.
35237 The SMTP command at fault was:
35238
35239 rcpt to:<malformed@in.com.plete
35240
35241 1 previous message was successfully processed.
35242 The rest of the batch was abandoned.
35243 .endd
35244 The return code from Exim is zero only if there were no errors. It is 1 if some
35245 messages were accepted before an error was detected, and 2 if no messages were
35246 accepted.
35247 .ecindex IIDsmtpproc1
35248 .ecindex IIDsmtpproc2
35249
35250
35251
35252 . ////////////////////////////////////////////////////////////////////////////
35253 . ////////////////////////////////////////////////////////////////////////////
35254
35255 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
35256 "Customizing messages"
35257 When a message fails to be delivered, or remains on the queue for more than a
35258 configured amount of time, Exim sends a message to the original sender, or
35259 to an alternative configured address. The text of these messages is built into
35260 the code of Exim, but it is possible to change it, either by adding a single
35261 string, or by replacing each of the paragraphs by text supplied in a file.
35262
35263 The &'From:'& and &'To:'& header lines are automatically generated; you can
35264 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
35265 option. Exim also adds the line
35266 .code
35267 Auto-Submitted: auto-generated
35268 .endd
35269 to all warning and bounce messages,
35270
35271
35272 .section "Customizing bounce messages" "SECID239"
35273 .cindex "customizing" "bounce message"
35274 .cindex "bounce message" "customizing"
35275 If &%bounce_message_text%& is set, its contents are included in the default
35276 message immediately after &"This message was created automatically by mail
35277 delivery software."& The string is not expanded. It is not used if
35278 &%bounce_message_file%& is set.
35279
35280 When &%bounce_message_file%& is set, it must point to a template file for
35281 constructing error messages. The file consists of a series of text items,
35282 separated by lines consisting of exactly four asterisks. If the file cannot be
35283 opened, default text is used and a message is written to the main and panic
35284 logs. If any text item in the file is empty, default text is used for that
35285 item.
35286
35287 .vindex "&$bounce_recipient$&"
35288 .vindex "&$bounce_return_size_limit$&"
35289 Each item of text that is read from the file is expanded, and there are two
35290 expansion variables which can be of use here: &$bounce_recipient$& is set to
35291 the recipient of an error message while it is being created, and
35292 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
35293 option, rounded to a whole number.
35294
35295 The items must appear in the file in the following order:
35296
35297 .ilist
35298 The first item is included in the headers, and should include at least a
35299 &'Subject:'& header. Exim does not check the syntax of these headers.
35300 .next
35301 The second item forms the start of the error message. After it, Exim lists the
35302 failing addresses with their error messages.
35303 .next
35304 The third item is used to introduce any text from pipe transports that is to be
35305 returned to the sender. It is omitted if there is no such text.
35306 .next
35307 The fourth, fifth and sixth items will be ignored and may be empty.
35308 The fields exist for back-compatibility
35309 .endlist
35310
35311 The default state (&%bounce_message_file%& unset) is equivalent to the
35312 following file, in which the sixth item is empty. The &'Subject:'& and some
35313 other lines have been split in order to fit them on the page:
35314 .code
35315 Subject: Mail delivery failed
35316 ${if eq{$sender_address}{$bounce_recipient}
35317 {: returning message to sender}}
35318 ****
35319 This message was created automatically by mail delivery software.
35320
35321 A message ${if eq{$sender_address}{$bounce_recipient}
35322 {that you sent }{sent by
35323
35324 <$sender_address>
35325
35326 }}could not be delivered to all of its recipients.
35327 This is a permanent error. The following address(es) failed:
35328 ****
35329 The following text was generated during the delivery attempt(s):
35330 ****
35331 ------ This is a copy of the message, including all the headers.
35332 ------
35333 ****
35334 ------ The body of the message is $message_size characters long;
35335 only the first
35336 ------ $bounce_return_size_limit or so are included here.
35337 ****
35338 .endd
35339 .section "Customizing warning messages" "SECTcustwarn"
35340 .cindex "customizing" "warning message"
35341 .cindex "warning of delay" "customizing the message"
35342 The option &%warn_message_file%& can be pointed at a template file for use when
35343 warnings about message delays are created. In this case there are only three
35344 text sections:
35345
35346 .ilist
35347 The first item is included in the headers, and should include at least a
35348 &'Subject:'& header. Exim does not check the syntax of these headers.
35349 .next
35350 The second item forms the start of the warning message. After it, Exim lists
35351 the delayed addresses.
35352 .next
35353 The third item then ends the message.
35354 .endlist
35355
35356 The default state is equivalent to the following file, except that some lines
35357 have been split here, in order to fit them on the page:
35358 .code
35359 Subject: Warning: message $message_exim_id delayed
35360 $warn_message_delay
35361 ****
35362 This message was created automatically by mail delivery software.
35363
35364 A message ${if eq{$sender_address}{$warn_message_recipients}
35365 {that you sent }{sent by
35366
35367 <$sender_address>
35368
35369 }}has not been delivered to all of its recipients after
35370 more than $warn_message_delay on the queue on $primary_hostname.
35371
35372 The message identifier is: $message_exim_id
35373 The subject of the message is: $h_subject
35374 The date of the message is: $h_date
35375
35376 The following address(es) have not yet been delivered:
35377 ****
35378 No action is required on your part. Delivery attempts will
35379 continue for some time, and this warning may be repeated at
35380 intervals if the message remains undelivered. Eventually the
35381 mail delivery software will give up, and when that happens,
35382 the message will be returned to you.
35383 .endd
35384 .vindex "&$warn_message_delay$&"
35385 .vindex "&$warn_message_recipients$&"
35386 However, in the default state the subject and date lines are omitted if no
35387 appropriate headers exist. During the expansion of this file,
35388 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
35389 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
35390 of recipients for the warning message. There may be more than one if there are
35391 multiple addresses with different &%errors_to%& settings on the routers that
35392 handled them.
35393
35394
35395
35396
35397 . ////////////////////////////////////////////////////////////////////////////
35398 . ////////////////////////////////////////////////////////////////////////////
35399
35400 .chapter "Some common configuration settings" "CHAPcomconreq"
35401 This chapter discusses some configuration settings that seem to be fairly
35402 common. More examples and discussion can be found in the Exim book.
35403
35404
35405
35406 .section "Sending mail to a smart host" "SECID240"
35407 .cindex "smart host" "example router"
35408 If you want to send all mail for non-local domains to a &"smart host"&, you
35409 should replace the default &(dnslookup)& router with a router which does the
35410 routing explicitly:
35411 .code
35412 send_to_smart_host:
35413 driver = manualroute
35414 route_list = !+local_domains smart.host.name
35415 transport = remote_smtp
35416 .endd
35417 You can use the smart host's IP address instead of the name if you wish.
35418 If you are using Exim only to submit messages to a smart host, and not for
35419 receiving incoming messages, you can arrange for it to do the submission
35420 synchronously by setting the &%mua_wrapper%& option (see chapter
35421 &<<CHAPnonqueueing>>&).
35422
35423
35424
35425
35426 .section "Using Exim to handle mailing lists" "SECTmailinglists"
35427 .cindex "mailing lists"
35428 Exim can be used to run simple mailing lists, but for large and/or complicated
35429 requirements, the use of additional specialized mailing list software such as
35430 Majordomo or Mailman is recommended.
35431
35432 The &(redirect)& router can be used to handle mailing lists where each list
35433 is maintained in a separate file, which can therefore be managed by an
35434 independent manager. The &%domains%& router option can be used to run these
35435 lists in a separate domain from normal mail. For example:
35436 .code
35437 lists:
35438 driver = redirect
35439 domains = lists.example
35440 file = /usr/lists/$local_part
35441 forbid_pipe
35442 forbid_file
35443 errors_to = $local_part-request@lists.example
35444 no_more
35445 .endd
35446 This router is skipped for domains other than &'lists.example'&. For addresses
35447 in that domain, it looks for a file that matches the local part. If there is no
35448 such file, the router declines, but because &%no_more%& is set, no subsequent
35449 routers are tried, and so the whole delivery fails.
35450
35451 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
35452 expanded into a file name or a pipe delivery, which is usually inappropriate in
35453 a mailing list.
35454
35455 .oindex "&%errors_to%&"
35456 The &%errors_to%& option specifies that any delivery errors caused by addresses
35457 taken from a mailing list are to be sent to the given address rather than the
35458 original sender of the message. However, before acting on this, Exim verifies
35459 the error address, and ignores it if verification fails.
35460
35461 For example, using the configuration above, mail sent to
35462 &'dicts@lists.example'& is passed on to those addresses contained in
35463 &_/usr/lists/dicts_&, with error reports directed to
35464 &'dicts-request@lists.example'&, provided that this address can be verified.
35465 There could be a file called &_/usr/lists/dicts-request_& containing
35466 the address(es) of this particular list's manager(s), but other approaches,
35467 such as setting up an earlier router (possibly using the &%local_part_prefix%&
35468 or &%local_part_suffix%& options) to handle addresses of the form
35469 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
35470
35471
35472
35473 .section "Syntax errors in mailing lists" "SECID241"
35474 .cindex "mailing lists" "syntax errors in"
35475 If an entry in redirection data contains a syntax error, Exim normally defers
35476 delivery of the original address. That means that a syntax error in a mailing
35477 list holds up all deliveries to the list. This may not be appropriate when a
35478 list is being maintained automatically from data supplied by users, and the
35479 addresses are not rigorously checked.
35480
35481 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
35482 entries that fail to parse, noting the incident in the log. If in addition
35483 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
35484 whenever a broken address is skipped. It is usually appropriate to set
35485 &%syntax_errors_to%& to the same address as &%errors_to%&.
35486
35487
35488
35489 .section "Re-expansion of mailing lists" "SECID242"
35490 .cindex "mailing lists" "re-expansion of"
35491 Exim remembers every individual address to which a message has been delivered,
35492 in order to avoid duplication, but it normally stores only the original
35493 recipient addresses with a message. If all the deliveries to a mailing list
35494 cannot be done at the first attempt, the mailing list is re-expanded when the
35495 delivery is next tried. This means that alterations to the list are taken into
35496 account at each delivery attempt, so addresses that have been added to
35497 the list since the message arrived will therefore receive a copy of the
35498 message, even though it pre-dates their subscription.
35499
35500 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
35501 on the &(redirect)& router. If this is done, any addresses generated by the
35502 router that fail to deliver at the first attempt are added to the message as
35503 &"top level"& addresses, and the parent address that generated them is marked
35504 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
35505 subsequent delivery attempts. The disadvantage of this is that if any of the
35506 failing addresses are incorrect, correcting them in the file has no effect on
35507 pre-existing messages.
35508
35509 The original top-level address is remembered with each of the generated
35510 addresses, and is output in any log messages. However, any intermediate parent
35511 addresses are not recorded. This makes a difference to the log only if the
35512 &%all_parents%& selector is set, but for mailing lists there is normally only
35513 one level of expansion anyway.
35514
35515
35516
35517 .section "Closed mailing lists" "SECID243"
35518 .cindex "mailing lists" "closed"
35519 The examples so far have assumed open mailing lists, to which anybody may
35520 send mail. It is also possible to set up closed lists, where mail is accepted
35521 from specified senders only. This is done by making use of the generic
35522 &%senders%& option to restrict the router that handles the list.
35523
35524 The following example uses the same file as a list of recipients and as a list
35525 of permitted senders. It requires three routers:
35526 .code
35527 lists_request:
35528 driver = redirect
35529 domains = lists.example
35530 local_part_suffix = -request
35531 file = /usr/lists/$local_part$local_part_suffix
35532 no_more
35533
35534 lists_post:
35535 driver = redirect
35536 domains = lists.example
35537 senders = ${if exists {/usr/lists/$local_part}\
35538 {lsearch;/usr/lists/$local_part}{*}}
35539 file = /usr/lists/$local_part
35540 forbid_pipe
35541 forbid_file
35542 errors_to = $local_part-request@lists.example
35543 no_more
35544
35545 lists_closed:
35546 driver = redirect
35547 domains = lists.example
35548 allow_fail
35549 data = :fail: $local_part@lists.example is a closed mailing list
35550 .endd
35551 All three routers have the same &%domains%& setting, so for any other domains,
35552 they are all skipped. The first router runs only if the local part ends in
35553 &%-request%&. It handles messages to the list manager(s) by means of an open
35554 mailing list.
35555
35556 The second router runs only if the &%senders%& precondition is satisfied. It
35557 checks for the existence of a list that corresponds to the local part, and then
35558 checks that the sender is on the list by means of a linear search. It is
35559 necessary to check for the existence of the file before trying to search it,
35560 because otherwise Exim thinks there is a configuration error. If the file does
35561 not exist, the expansion of &%senders%& is *, which matches all senders. This
35562 means that the router runs, but because there is no list, declines, and
35563 &%no_more%& ensures that no further routers are run. The address fails with an
35564 &"unrouteable address"& error.
35565
35566 The third router runs only if the second router is skipped, which happens when
35567 a mailing list exists, but the sender is not on it. This router forcibly fails
35568 the address, giving a suitable error message.
35569
35570
35571
35572
35573 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
35574 .cindex "VERP"
35575 .cindex "Variable Envelope Return Paths"
35576 .cindex "envelope sender"
35577 Variable Envelope Return Paths &-- see &url(http://cr.yp.to/proto/verp.txt) &--
35578 are a way of helping mailing list administrators discover which subscription
35579 address is the cause of a particular delivery failure. The idea is to encode
35580 the original recipient address in the outgoing envelope sender address, so that
35581 if the message is forwarded by another host and then subsequently bounces, the
35582 original recipient can be extracted from the recipient address of the bounce.
35583
35584 .oindex &%errors_to%&
35585 .oindex &%return_path%&
35586 Envelope sender addresses can be modified by Exim using two different
35587 facilities: the &%errors_to%& option on a router (as shown in previous mailing
35588 list examples), or the &%return_path%& option on a transport. The second of
35589 these is effective only if the message is successfully delivered to another
35590 host; it is not used for errors detected on the local host (see the description
35591 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
35592 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
35593 .code
35594 verp_smtp:
35595 driver = smtp
35596 max_rcpt = 1
35597 return_path = \
35598 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
35599 {$1-request+$local_part=$domain@your.dom.example}fail}
35600 .endd
35601 This has the effect of rewriting the return path (envelope sender) on outgoing
35602 SMTP messages, if the local part of the original return path ends in
35603 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
35604 local part and domain of the recipient into the return path. Suppose, for
35605 example, that a message whose return path has been set to
35606 &'somelist-request@your.dom.example'& is sent to
35607 &'subscriber@other.dom.example'&. In the transport, the return path is
35608 rewritten as
35609 .code
35610 somelist-request+subscriber=other.dom.example@your.dom.example
35611 .endd
35612 .vindex "&$local_part$&"
35613 For this to work, you must tell Exim to send multiple copies of messages that
35614 have more than one recipient, so that each copy has just one recipient. This is
35615 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
35616 might be sent to several different recipients in the same domain, in which case
35617 &$local_part$& is not available in the transport, because it is not unique.
35618
35619 Unless your host is doing nothing but mailing list deliveries, you should
35620 probably use a separate transport for the VERP deliveries, so as not to use
35621 extra resources in making one-per-recipient copies for other deliveries. This
35622 can easily be done by expanding the &%transport%& option in the router:
35623 .code
35624 dnslookup:
35625 driver = dnslookup
35626 domains = ! +local_domains
35627 transport = \
35628 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
35629 {verp_smtp}{remote_smtp}}
35630 no_more
35631 .endd
35632 If you want to change the return path using &%errors_to%& in a router instead
35633 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
35634 routers that handle mailing list addresses. This will ensure that all delivery
35635 errors, including those detected on the local host, are sent to the VERP
35636 address.
35637
35638 On a host that does no local deliveries and has no manual routing, only the
35639 &(dnslookup)& router needs to be changed. A special transport is not needed for
35640 SMTP deliveries. Every mailing list recipient has its own return path value,
35641 and so Exim must hand them to the transport one at a time. Here is an example
35642 of a &(dnslookup)& router that implements VERP:
35643 .code
35644 verp_dnslookup:
35645 driver = dnslookup
35646 domains = ! +local_domains
35647 transport = remote_smtp
35648 errors_to = \
35649 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
35650 {$1-request+$local_part=$domain@your.dom.example}fail}
35651 no_more
35652 .endd
35653 Before you start sending out messages with VERPed return paths, you must also
35654 configure Exim to accept the bounce messages that come back to those paths.
35655 Typically this is done by setting a &%local_part_suffix%& option for a
35656 router, and using this to route the messages to wherever you want to handle
35657 them.
35658
35659 The overhead incurred in using VERP depends very much on the size of the
35660 message, the number of recipient addresses that resolve to the same remote
35661 host, and the speed of the connection over which the message is being sent. If
35662 a lot of addresses resolve to the same host and the connection is slow, sending
35663 a separate copy of the message for each address may take substantially longer
35664 than sending a single copy with many recipients (for which VERP cannot be
35665 used).
35666
35667
35668
35669
35670
35671
35672 .section "Virtual domains" "SECTvirtualdomains"
35673 .cindex "virtual domains"
35674 .cindex "domain" "virtual"
35675 The phrase &'virtual domain'& is unfortunately used with two rather different
35676 meanings:
35677
35678 .ilist
35679 A domain for which there are no real mailboxes; all valid local parts are
35680 aliases for other email addresses. Common examples are organizational
35681 top-level domains and &"vanity"& domains.
35682 .next
35683 One of a number of independent domains that are all handled by the same host,
35684 with mailboxes on that host, but where the mailbox owners do not necessarily
35685 have login accounts on that host.
35686 .endlist
35687
35688 The first usage is probably more common, and does seem more &"virtual"& than
35689 the second. This kind of domain can be handled in Exim with a straightforward
35690 aliasing router. One approach is to create a separate alias file for each
35691 virtual domain. Exim can test for the existence of the alias file to determine
35692 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
35693 to a router of this form:
35694 .code
35695 virtual:
35696 driver = redirect
35697 domains = dsearch;/etc/mail/virtual
35698 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
35699 no_more
35700 .endd
35701 The &%domains%& option specifies that the router is to be skipped, unless there
35702 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
35703 domain that is being processed. When the router runs, it looks up the local
35704 part in the file to find a new address (or list of addresses). The &%no_more%&
35705 setting ensures that if the lookup fails (leading to &%data%& being an empty
35706 string), Exim gives up on the address without trying any subsequent routers.
35707
35708 This one router can handle all the virtual domains because the alias file names
35709 follow a fixed pattern. Permissions can be arranged so that appropriate people
35710 can edit the different alias files. A successful aliasing operation results in
35711 a new envelope recipient address, which is then routed from scratch.
35712
35713 The other kind of &"virtual"& domain can also be handled in a straightforward
35714 way. One approach is to create a file for each domain containing a list of
35715 valid local parts, and use it in a router like this:
35716 .code
35717 my_domains:
35718 driver = accept
35719 domains = dsearch;/etc/mail/domains
35720 local_parts = lsearch;/etc/mail/domains/$domain
35721 transport = my_mailboxes
35722 .endd
35723 The address is accepted if there is a file for the domain, and the local part
35724 can be found in the file. The &%domains%& option is used to check for the
35725 file's existence because &%domains%& is tested before the &%local_parts%&
35726 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
35727 because that option is tested after &%local_parts%&. The transport is as
35728 follows:
35729 .code
35730 my_mailboxes:
35731 driver = appendfile
35732 file = /var/mail/$domain/$local_part
35733 user = mail
35734 .endd
35735 This uses a directory of mailboxes for each domain. The &%user%& setting is
35736 required, to specify which uid is to be used for writing to the mailboxes.
35737
35738 The configuration shown here is just one example of how you might support this
35739 requirement. There are many other ways this kind of configuration can be set
35740 up, for example, by using a database instead of separate files to hold all the
35741 information about the domains.
35742
35743
35744
35745 .section "Multiple user mailboxes" "SECTmulbox"
35746 .cindex "multiple mailboxes"
35747 .cindex "mailbox" "multiple"
35748 .cindex "local part" "prefix"
35749 .cindex "local part" "suffix"
35750 Heavy email users often want to operate with multiple mailboxes, into which
35751 incoming mail is automatically sorted. A popular way of handling this is to
35752 allow users to use multiple sender addresses, so that replies can easily be
35753 identified. Users are permitted to add prefixes or suffixes to their local
35754 parts for this purpose. The wildcard facility of the generic router options
35755 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
35756 example, consider this router:
35757 .code
35758 userforward:
35759 driver = redirect
35760 check_local_user
35761 file = $home/.forward
35762 local_part_suffix = -*
35763 local_part_suffix_optional
35764 allow_filter
35765 .endd
35766 .vindex "&$local_part_suffix$&"
35767 It runs a user's &_.forward_& file for all local parts of the form
35768 &'username-*'&. Within the filter file the user can distinguish different
35769 cases by testing the variable &$local_part_suffix$&. For example:
35770 .code
35771 if $local_part_suffix contains -special then
35772 save /home/$local_part/Mail/special
35773 endif
35774 .endd
35775 If the filter file does not exist, or does not deal with such addresses, they
35776 fall through to subsequent routers, and, assuming no subsequent use of the
35777 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
35778 control over which suffixes are valid.
35779
35780 Alternatively, a suffix can be used to trigger the use of a different
35781 &_.forward_& file &-- which is the way a similar facility is implemented in
35782 another MTA:
35783 .code
35784 userforward:
35785 driver = redirect
35786 check_local_user
35787 file = $home/.forward$local_part_suffix
35788 local_part_suffix = -*
35789 local_part_suffix_optional
35790 allow_filter
35791 .endd
35792 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
35793 example, &_.forward-special_& is used. Once again, if the appropriate file
35794 does not exist, or does not deal with the address, it is passed on to
35795 subsequent routers, which could, if required, look for an unqualified
35796 &_.forward_& file to use as a default.
35797
35798
35799
35800 .section "Simplified vacation processing" "SECID244"
35801 .cindex "vacation processing"
35802 The traditional way of running the &'vacation'& program is for a user to set up
35803 a pipe command in a &_.forward_& file
35804 (see section &<<SECTspecitredli>>& for syntax details).
35805 This is prone to error by inexperienced users. There are two features of Exim
35806 that can be used to make this process simpler for users:
35807
35808 .ilist
35809 A local part prefix such as &"vacation-"& can be specified on a router which
35810 can cause the message to be delivered directly to the &'vacation'& program, or
35811 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
35812 &_.forward_& file are then much simpler. For example:
35813 .code
35814 spqr, vacation-spqr
35815 .endd
35816 .next
35817 The &%require_files%& generic router option can be used to trigger a
35818 vacation delivery by checking for the existence of a certain file in the
35819 user's home directory. The &%unseen%& generic option should also be used, to
35820 ensure that the original delivery also proceeds. In this case, all the user has
35821 to do is to create a file called, say, &_.vacation_&, containing a vacation
35822 message.
35823 .endlist
35824
35825 Another advantage of both these methods is that they both work even when the
35826 use of arbitrary pipes by users is locked out.
35827
35828
35829
35830 .section "Taking copies of mail" "SECID245"
35831 .cindex "message" "copying every"
35832 Some installations have policies that require archive copies of all messages to
35833 be made. A single copy of each message can easily be taken by an appropriate
35834 command in a system filter, which could, for example, use a different file for
35835 each day's messages.
35836
35837 There is also a shadow transport mechanism that can be used to take copies of
35838 messages that are successfully delivered by local transports, one copy per
35839 delivery. This could be used, &'inter alia'&, to implement automatic
35840 notification of delivery by sites that insist on doing such things.
35841
35842
35843
35844 .section "Intermittently connected hosts" "SECID246"
35845 .cindex "intermittently connected hosts"
35846 It has become quite common (because it is cheaper) for hosts to connect to the
35847 Internet periodically rather than remain connected all the time. The normal
35848 arrangement is that mail for such hosts accumulates on a system that is
35849 permanently connected.
35850
35851 Exim was designed for use on permanently connected hosts, and so it is not
35852 particularly well-suited to use in an intermittently connected environment.
35853 Nevertheless there are some features that can be used.
35854
35855
35856 .section "Exim on the upstream server host" "SECID247"
35857 It is tempting to arrange for incoming mail for the intermittently connected
35858 host to remain on Exim's queue until the client connects. However, this
35859 approach does not scale very well. Two different kinds of waiting message are
35860 being mixed up in the same queue &-- those that cannot be delivered because of
35861 some temporary problem, and those that are waiting for their destination host
35862 to connect. This makes it hard to manage the queue, as well as wasting
35863 resources, because each queue runner scans the entire queue.
35864
35865 A better approach is to separate off those messages that are waiting for an
35866 intermittently connected host. This can be done by delivering these messages
35867 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
35868 format, from where they are transmitted by other software when their
35869 destination connects. This makes it easy to collect all the mail for one host
35870 in a single directory, and to apply local timeout rules on a per-message basis
35871 if required.
35872
35873 On a very small scale, leaving the mail on Exim's queue can be made to work. If
35874 you are doing this, you should configure Exim with a long retry period for the
35875 intermittent host. For example:
35876 .code
35877 cheshire.wonderland.fict.example * F,5d,24h
35878 .endd
35879 This stops a lot of failed delivery attempts from occurring, but Exim remembers
35880 which messages it has queued up for that host. Once the intermittent host comes
35881 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
35882 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
35883 causes all the queued up messages to be delivered, often down a single SMTP
35884 connection. While the host remains connected, any new messages get delivered
35885 immediately.
35886
35887 If the connecting hosts do not have fixed IP addresses, that is, if a host is
35888 issued with a different IP address each time it connects, Exim's retry
35889 mechanisms on the holding host get confused, because the IP address is normally
35890 used as part of the key string for holding retry information. This can be
35891 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
35892 Since this has disadvantages for permanently connected hosts, it is best to
35893 arrange a separate transport for the intermittently connected ones.
35894
35895
35896
35897 .section "Exim on the intermittently connected client host" "SECID248"
35898 The value of &%smtp_accept_queue_per_connection%& should probably be
35899 increased, or even set to zero (that is, disabled) on the intermittently
35900 connected host, so that all incoming messages down a single connection get
35901 delivered immediately.
35902
35903 .cindex "SMTP" "passed connection"
35904 .cindex "SMTP" "multiple deliveries"
35905 .cindex "multiple SMTP deliveries"
35906 Mail waiting to be sent from an intermittently connected host will probably
35907 not have been routed, because without a connection DNS lookups are not
35908 possible. This means that if a normal queue run is done at connection time,
35909 each message is likely to be sent in a separate SMTP session. This can be
35910 avoided by starting the queue run with a command line option beginning with
35911 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
35912 first pass, routing is done but no deliveries take place. The second pass is a
35913 normal queue run; since all the messages have been previously routed, those
35914 destined for the same host are likely to get sent as multiple deliveries in a
35915 single SMTP connection.
35916
35917
35918
35919 . ////////////////////////////////////////////////////////////////////////////
35920 . ////////////////////////////////////////////////////////////////////////////
35921
35922 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
35923 "Exim as a non-queueing client"
35924 .cindex "client, non-queueing"
35925 .cindex "smart host" "suppressing queueing"
35926 On a personal computer, it is a common requirement for all
35927 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
35928 configured to operate that way, for all the popular operating systems.
35929 However, there are some MUAs for Unix-like systems that cannot be so
35930 configured: they submit messages using the command line interface of
35931 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
35932 messages this way.
35933
35934 If the personal computer runs continuously, there is no problem, because it can
35935 run a conventional MTA that handles delivery to the smart host, and deal with
35936 any delays via its queueing mechanism. However, if the computer does not run
35937 continuously or runs different operating systems at different times, queueing
35938 email is not desirable.
35939
35940 There is therefore a requirement for something that can provide the
35941 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
35942 any queueing or retrying facilities. Furthermore, the delivery to the smart
35943 host should be synchronous, so that if it fails, the sending MUA is immediately
35944 informed. In other words, we want something that extends an MUA that submits
35945 to a local MTA via the command line so that it behaves like one that submits
35946 to a remote smart host using TCP/SMTP.
35947
35948 There are a number of applications (for example, there is one called &'ssmtp'&)
35949 that do this job. However, people have found them to be lacking in various
35950 ways. For instance, you might want to allow aliasing and forwarding to be done
35951 before sending a message to the smart host.
35952
35953 Exim already had the necessary infrastructure for doing this job. Just a few
35954 tweaks were needed to make it behave as required, though it is somewhat of an
35955 overkill to use a fully-featured MTA for this purpose.
35956
35957 .oindex "&%mua_wrapper%&"
35958 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
35959 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
35960 assumes that it is being used to &"wrap"& a command-line MUA in the manner
35961 just described. As well as setting &%mua_wrapper%&, you also need to provide a
35962 compatible router and transport configuration. Typically there will be just one
35963 router and one transport, sending everything to a smart host.
35964
35965 When run in MUA wrapping mode, the behaviour of Exim changes in the
35966 following ways:
35967
35968 .ilist
35969 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
35970 In other words, the only way to submit messages is via the command line.
35971 .next
35972 Each message is synchronously delivered as soon as it is received (&%-odi%& is
35973 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
35974 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
35975 does not finish until the delivery attempt is complete. If the delivery is
35976 successful, a zero return code is given.
35977 .next
35978 Address redirection is permitted, but the final routing for all addresses must
35979 be to the same remote transport, and to the same list of hosts. Furthermore,
35980 the return address (envelope sender) must be the same for all recipients, as
35981 must any added or deleted header lines. In other words, it must be possible to
35982 deliver the message in a single SMTP transaction, however many recipients there
35983 are.
35984 .next
35985 If these conditions are not met, or if routing any address results in a
35986 failure or defer status, or if Exim is unable to deliver all the recipients
35987 successfully to one of the smart hosts, delivery of the entire message fails.
35988 .next
35989 Because no queueing is allowed, all failures are treated as permanent; there
35990 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
35991 smart host. Furthermore, because only a single yes/no response can be given to
35992 the caller, it is not possible to deliver to some recipients and not others. If
35993 there is an error (temporary or permanent) for any recipient, all are failed.
35994 .next
35995 If more than one smart host is listed, Exim will try another host after a
35996 connection failure or a timeout, in the normal way. However, if this kind of
35997 failure happens for all the hosts, the delivery fails.
35998 .next
35999 When delivery fails, an error message is written to the standard error stream
36000 (as well as to Exim's log), and Exim exits to the caller with a return code
36001 value 1. The message is expunged from Exim's spool files. No bounce messages
36002 are ever generated.
36003 .next
36004 No retry data is maintained, and any retry rules are ignored.
36005 .next
36006 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
36007 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
36008 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
36009 .endlist
36010
36011 The overall effect is that Exim makes a single synchronous attempt to deliver
36012 the message, failing if there is any kind of problem. Because no local
36013 deliveries are done and no daemon can be run, Exim does not need root
36014 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
36015 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
36016 the advantages and disadvantages of running without root privilege.
36017
36018
36019
36020
36021 . ////////////////////////////////////////////////////////////////////////////
36022 . ////////////////////////////////////////////////////////////////////////////
36023
36024 .chapter "Log files" "CHAPlog"
36025 .scindex IIDloggen "log" "general description"
36026 .cindex "log" "types of"
36027 Exim writes three different logs, referred to as the main log, the reject log,
36028 and the panic log:
36029
36030 .ilist
36031 .cindex "main log"
36032 The main log records the arrival of each message and each delivery in a single
36033 line in each case. The format is as compact as possible, in an attempt to keep
36034 down the size of log files. Two-character flag sequences make it easy to pick
36035 out these lines. A number of other events are recorded in the main log. Some of
36036 them are optional, in which case the &%log_selector%& option controls whether
36037 they are included or not. A Perl script called &'eximstats'&, which does simple
36038 analysis of main log files, is provided in the Exim distribution (see section
36039 &<<SECTmailstat>>&).
36040 .next
36041 .cindex "reject log"
36042 The reject log records information from messages that are rejected as a result
36043 of a configuration option (that is, for policy reasons).
36044 The first line of each rejection is a copy of the line that is also written to
36045 the main log. Then, if the message's header has been read at the time the log
36046 is written, its contents are written to this log. Only the original header
36047 lines are available; header lines added by ACLs are not logged. You can use the
36048 reject log to check that your policy controls are working correctly; on a busy
36049 host this may be easier than scanning the main log for rejection messages. You
36050 can suppress the writing of the reject log by setting &%write_rejectlog%&
36051 false.
36052 .next
36053 .cindex "panic log"
36054 .cindex "system log"
36055 When certain serious errors occur, Exim writes entries to its panic log. If the
36056 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
36057 are usually written to the main log as well, but can get lost amid the mass of
36058 other entries. The panic log should be empty under normal circumstances. It is
36059 therefore a good idea to check it (or to have a &'cron'& script check it)
36060 regularly, in order to become aware of any problems. When Exim cannot open its
36061 panic log, it tries as a last resort to write to the system log (syslog). This
36062 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
36063 message itself is written at priority LOG_CRIT.
36064 .endlist
36065
36066 Every log line starts with a timestamp, in the format shown in the following
36067 example. Note that many of the examples shown in this chapter are line-wrapped.
36068 In the log file, this would be all on one line:
36069 .code
36070 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
36071 by QUIT
36072 .endd
36073 By default, the timestamps are in the local timezone. There are two
36074 ways of changing this:
36075
36076 .ilist
36077 You can set the &%timezone%& option to a different time zone; in particular, if
36078 you set
36079 .code
36080 timezone = UTC
36081 .endd
36082 the timestamps will be in UTC (aka GMT).
36083 .next
36084 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
36085 example:
36086 .code
36087 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
36088 .endd
36089 .endlist
36090
36091 .cindex "log" "process ids in"
36092 .cindex "pid (process id)" "in log lines"
36093 Exim does not include its process id in log lines by default, but you can
36094 request that it does so by specifying the &`pid`& log selector (see section
36095 &<<SECTlogselector>>&). When this is set, the process id is output, in square
36096 brackets, immediately after the time and date.
36097
36098
36099
36100
36101 .section "Where the logs are written" "SECTwhelogwri"
36102 .cindex "log" "destination"
36103 .cindex "log" "to file"
36104 .cindex "log" "to syslog"
36105 .cindex "syslog"
36106 The logs may be written to local files, or to syslog, or both. However, it
36107 should be noted that many syslog implementations use UDP as a transport, and
36108 are therefore unreliable in the sense that messages are not guaranteed to
36109 arrive at the loghost, nor is the ordering of messages necessarily maintained.
36110 It has also been reported that on large log files (tens of megabytes) you may
36111 need to tweak syslog to prevent it syncing the file with each write &-- on
36112 Linux this has been seen to make syslog take 90% plus of CPU time.
36113
36114 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
36115 &_Local/Makefile_& or by setting &%log_file_path%& in the run time
36116 configuration. This latter string is expanded, so it can contain, for example,
36117 references to the host name:
36118 .code
36119 log_file_path = /var/log/$primary_hostname/exim_%slog
36120 .endd
36121 It is generally advisable, however, to set the string in &_Local/Makefile_&
36122 rather than at run time, because then the setting is available right from the
36123 start of Exim's execution. Otherwise, if there's something it wants to log
36124 before it has read the configuration file (for example, an error in the
36125 configuration file) it will not use the path you want, and may not be able to
36126 log at all.
36127
36128 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
36129 list, currently limited to at most two items. This is one option where the
36130 facility for changing a list separator may not be used. The list must always be
36131 colon-separated. If an item in the list is &"syslog"& then syslog is used;
36132 otherwise the item must either be an absolute path, containing &`%s`& at the
36133 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
36134 implying the use of a default path.
36135
36136 When Exim encounters an empty item in the list, it searches the list defined by
36137 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
36138 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
36139 mean &"use the path specified at build time"&. It no such item exists, log
36140 files are written in the &_log_& subdirectory of the spool directory. This is
36141 equivalent to the setting:
36142 .code
36143 log_file_path = $spool_directory/log/%slog
36144 .endd
36145 If you do not specify anything at build time or run time,
36146 or if you unset the option at run time (i.e. &`log_file_path = `&),
36147 that is where the logs are written.
36148
36149 A log file path may also contain &`%D`& or &`%M`& if datestamped log file names
36150 are in use &-- see section &<<SECTdatlogfil>>& below.
36151
36152 Here are some examples of possible settings:
36153 .display
36154 &`LOG_FILE_PATH=syslog `& syslog only
36155 &`LOG_FILE_PATH=:syslog `& syslog and default path
36156 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
36157 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
36158 .endd
36159 If there are more than two paths in the list, the first is used and a panic
36160 error is logged.
36161
36162
36163
36164 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
36165 .cindex "log" "cycling local files"
36166 .cindex "cycling logs"
36167 .cindex "&'exicyclog'&"
36168 .cindex "log" "local files; writing to"
36169 Some operating systems provide centralized and standardized methods for cycling
36170 log files. For those that do not, a utility script called &'exicyclog'& is
36171 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
36172 main and reject logs each time it is called. The maximum number of old logs to
36173 keep can be set. It is suggested this script is run as a daily &'cron'& job.
36174
36175 An Exim delivery process opens the main log when it first needs to write to it,
36176 and it keeps the file open in case subsequent entries are required &-- for
36177 example, if a number of different deliveries are being done for the same
36178 message. However, remote SMTP deliveries can take a long time, and this means
36179 that the file may be kept open long after it is renamed if &'exicyclog'& or
36180 something similar is being used to rename log files on a regular basis. To
36181 ensure that a switch of log files is noticed as soon as possible, Exim calls
36182 &[stat()]& on the main log's name before reusing an open file, and if the file
36183 does not exist, or its inode has changed, the old file is closed and Exim
36184 tries to open the main log from scratch. Thus, an old log file may remain open
36185 for quite some time, but no Exim processes should write to it once it has been
36186 renamed.
36187
36188
36189
36190 .section "Datestamped log files" "SECTdatlogfil"
36191 .cindex "log" "datestamped files"
36192 Instead of cycling the main and reject log files by renaming them
36193 periodically, some sites like to use files whose names contain a datestamp,
36194 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
36195 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
36196 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
36197 point where the datestamp is required. For example:
36198 .code
36199 log_file_path = /var/spool/exim/log/%slog-%D
36200 log_file_path = /var/log/exim-%s-%D.log
36201 log_file_path = /var/spool/exim/log/%D-%slog
36202 log_file_path = /var/log/exim/%s.%M
36203 .endd
36204 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
36205 examples of names generated by the above examples:
36206 .code
36207 /var/spool/exim/log/mainlog-20021225
36208 /var/log/exim-reject-20021225.log
36209 /var/spool/exim/log/20021225-mainlog
36210 /var/log/exim/main.200212
36211 .endd
36212 When this form of log file is specified, Exim automatically switches to new
36213 files at midnight. It does not make any attempt to compress old logs; you
36214 will need to write your own script if you require this. You should not
36215 run &'exicyclog'& with this form of logging.
36216
36217 The location of the panic log is also determined by &%log_file_path%&, but it
36218 is not datestamped, because rotation of the panic log does not make sense.
36219 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
36220 the string. In addition, if it immediately follows a slash, a following
36221 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
36222 character is removed. Thus, the four examples above would give these panic
36223 log names:
36224 .code
36225 /var/spool/exim/log/paniclog
36226 /var/log/exim-panic.log
36227 /var/spool/exim/log/paniclog
36228 /var/log/exim/panic
36229 .endd
36230
36231
36232 .section "Logging to syslog" "SECID249"
36233 .cindex "log" "syslog; writing to"
36234 The use of syslog does not change what Exim logs or the format of its messages,
36235 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
36236 Exim's log lines are omitted when these lines are sent to syslog. Apart from
36237 that, the same strings are written to syslog as to log files. The syslog
36238 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
36239 by default, but you can change these by setting the &%syslog_facility%& and
36240 &%syslog_processname%& options, respectively. If Exim was compiled with
36241 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
36242 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
36243 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
36244 the time and host name to each line.
36245 The three log streams are mapped onto syslog priorities as follows:
36246
36247 .ilist
36248 &'mainlog'& is mapped to LOG_INFO
36249 .next
36250 &'rejectlog'& is mapped to LOG_NOTICE
36251 .next
36252 &'paniclog'& is mapped to LOG_ALERT
36253 .endlist
36254
36255 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
36256 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
36257 these are routed by syslog to the same place. You can suppress this duplication
36258 by setting &%syslog_duplication%& false.
36259
36260 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
36261 entries contain multiple lines when headers are included. To cope with both
36262 these cases, entries written to syslog are split into separate &[syslog()]&
36263 calls at each internal newline, and also after a maximum of
36264 870 data characters. (This allows for a total syslog line length of 1024, when
36265 additions such as timestamps are added.) If you are running a syslog
36266 replacement that can handle lines longer than the 1024 characters allowed by
36267 RFC 3164, you should set
36268 .code
36269 SYSLOG_LONG_LINES=yes
36270 .endd
36271 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
36272 lines, but it still splits at internal newlines in &'reject'& log entries.
36273
36274 To make it easy to re-assemble split lines later, each component of a split
36275 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
36276 where <&'n'&> is the component number and <&'m'&> is the total number of
36277 components in the entry. The / delimiter is used when the line was split
36278 because it was too long; if it was split because of an internal newline, the \
36279 delimiter is used. For example, supposing the length limit to be 50 instead of
36280 870, the following would be the result of a typical rejection message to
36281 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
36282 name, and pid as added by syslog:
36283 .code
36284 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
36285 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
36286 [3/5] when scanning for sender: missing or malformed lo
36287 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
36288 [5/5] mple>)
36289 .endd
36290 The same error might cause the following lines to be written to &"rejectlog"&
36291 (LOG_NOTICE):
36292 .code
36293 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
36294 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
36295 [3/18] er when scanning for sender: missing or malformed
36296 [4/18] local part in "<>" (envelope sender is <ph10@cam
36297 [5\18] .example>)
36298 [6\18] Recipients: ph10@some.domain.cam.example
36299 [7\18] P Received: from [127.0.0.1] (ident=ph10)
36300 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
36301 [9\18] id 16RdAL-0006pc-00
36302 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
36303 [11\18] 09:43 +0100
36304 [12\18] F From: <>
36305 [13\18] Subject: this is a test header
36306 [18\18] X-something: this is another header
36307 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
36308 [16\18] le>
36309 [17\18] B Bcc:
36310 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
36311 .endd
36312 Log lines that are neither too long nor contain newlines are written to syslog
36313 without modification.
36314
36315 If only syslog is being used, the Exim monitor is unable to provide a log tail
36316 display, unless syslog is routing &'mainlog'& to a file on the local host and
36317 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
36318 where it is.
36319
36320
36321
36322 .section "Log line flags" "SECID250"
36323 One line is written to the main log for each message received, and for each
36324 successful, unsuccessful, and delayed delivery. These lines can readily be
36325 picked out by the distinctive two-character flags that immediately follow the
36326 timestamp. The flags are:
36327 .display
36328 &`<=`& message arrival
36329 &`(=`& message fakereject
36330 &`=>`& normal message delivery
36331 &`->`& additional address in same delivery
36332 &`>>`& cutthrough message delivery
36333 &`*>`& delivery suppressed by &%-N%&
36334 &`**`& delivery failed; address bounced
36335 &`==`& delivery deferred; temporary problem
36336 .endd
36337
36338
36339 .section "Logging message reception" "SECID251"
36340 .cindex "log" "reception line"
36341 The format of the single-line entry in the main log that is written for every
36342 message received is shown in the basic example below, which is split over
36343 several lines in order to fit it on the page:
36344 .code
36345 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
36346 H=mailer.fict.example [192.168.123.123] U=exim
36347 P=smtp S=5678 id=<incoming message id>
36348 .endd
36349 The address immediately following &"<="& is the envelope sender address. A
36350 bounce message is shown with the sender address &"<>"&, and if it is locally
36351 generated, this is followed by an item of the form
36352 .code
36353 R=<message id>
36354 .endd
36355 which is a reference to the message that caused the bounce to be sent.
36356
36357 .cindex "HELO"
36358 .cindex "EHLO"
36359 For messages from other hosts, the H and U fields identify the remote host and
36360 record the RFC 1413 identity of the user that sent the message, if one was
36361 received. The number given in square brackets is the IP address of the sending
36362 host. If there is a single, unparenthesized host name in the H field, as
36363 above, it has been verified to correspond to the IP address (see the
36364 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
36365 by the remote host in the SMTP HELO or EHLO command, and has not been
36366 verified. If verification yields a different name to that given for HELO or
36367 EHLO, the verified name appears first, followed by the HELO or EHLO
36368 name in parentheses.
36369
36370 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
36371 without brackets, in the HELO or EHLO command, leading to entries in
36372 the log containing text like these examples:
36373 .code
36374 H=(10.21.32.43) [192.168.8.34]
36375 H=([10.21.32.43]) [192.168.8.34]
36376 .endd
36377 This can be confusing. Only the final address in square brackets can be relied
36378 on.
36379
36380 For locally generated messages (that is, messages not received over TCP/IP),
36381 the H field is omitted, and the U field contains the login name of the caller
36382 of Exim.
36383
36384 .cindex "authentication" "logging"
36385 .cindex "AUTH" "logging"
36386 For all messages, the P field specifies the protocol used to receive the
36387 message. This is the value that is stored in &$received_protocol$&. In the case
36388 of incoming SMTP messages, the value indicates whether or not any SMTP
36389 extensions (ESMTP), encryption, or authentication were used. If the SMTP
36390 session was encrypted, there is an additional X field that records the cipher
36391 suite that was used.
36392
36393 .cindex log protocol
36394 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
36395 hosts that have authenticated themselves using the SMTP AUTH command. The first
36396 value is used when the SMTP connection was encrypted (&"secure"&). In this case
36397 there is an additional item A= followed by the name of the authenticator that
36398 was used. If an authenticated identification was set up by the authenticator's
36399 &%server_set_id%& option, this is logged too, separated by a colon from the
36400 authenticator name.
36401
36402 .cindex "size" "of message"
36403 The id field records the existing message id, if present. The size of the
36404 received message is given by the S field. When the message is delivered,
36405 headers may be removed or added, so that the size of delivered copies of the
36406 message may not correspond with this value (and indeed may be different to each
36407 other).
36408
36409 The &%log_selector%& option can be used to request the logging of additional
36410 data when a message is received. See section &<<SECTlogselector>>& below.
36411
36412
36413
36414 .section "Logging deliveries" "SECID252"
36415 .cindex "log" "delivery line"
36416 The format of the single-line entry in the main log that is written for every
36417 delivery is shown in one of the examples below, for local and remote
36418 deliveries, respectively. Each example has been split into multiple lines in order
36419 to fit it on the page:
36420 .code
36421 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
36422 <marv@hitch.fict.example> R=localuser T=local_delivery
36423 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
36424 monk@holistic.fict.example R=dnslookup T=remote_smtp
36425 H=holistic.fict.example [192.168.234.234]
36426 .endd
36427 For ordinary local deliveries, the original address is given in angle brackets
36428 after the final delivery address, which might be a pipe or a file. If
36429 intermediate address(es) exist between the original and the final address, the
36430 last of these is given in parentheses after the final address. The R and T
36431 fields record the router and transport that were used to process the address.
36432
36433 If SMTP AUTH was used for the delivery there is an additional item A=
36434 followed by the name of the authenticator that was used.
36435 If an authenticated identification was set up by the authenticator's &%client_set_id%&
36436 option, this is logged too, separated by a colon from the authenticator name.
36437
36438 If a shadow transport was run after a successful local delivery, the log line
36439 for the successful delivery has an item added on the end, of the form
36440 .display
36441 &`ST=<`&&'shadow transport name'&&`>`&
36442 .endd
36443 If the shadow transport did not succeed, the error message is put in
36444 parentheses afterwards.
36445
36446 .cindex "asterisk" "after IP address"
36447 When more than one address is included in a single delivery (for example, two
36448 SMTP RCPT commands in one transaction) the second and subsequent addresses are
36449 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
36450 down a single SMTP connection, an asterisk follows the IP address in the log
36451 lines for the second and subsequent messages.
36452 When two or more messages are delivered down a single TLS connection, the
36453 DNS and some TLS-related information logged for the first message delivered
36454 will not be present in the log lines for the second and subsequent messages.
36455 TLS cipher information is still available.
36456
36457 .cindex "delivery" "cutthrough; logging"
36458 .cindex "cutthrough" "logging"
36459 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
36460 line precedes the reception line, since cutthrough waits for a possible
36461 rejection from the destination in case it can reject the sourced item.
36462
36463 The generation of a reply message by a filter file gets logged as a
36464 &"delivery"& to the addressee, preceded by &">"&.
36465
36466 The &%log_selector%& option can be used to request the logging of additional
36467 data when a message is delivered. See section &<<SECTlogselector>>& below.
36468
36469
36470 .section "Discarded deliveries" "SECID253"
36471 .cindex "discarded messages"
36472 .cindex "message" "discarded"
36473 .cindex "delivery" "discarded; logging"
36474 When a message is discarded as a result of the command &"seen finish"& being
36475 obeyed in a filter file which generates no deliveries, a log entry of the form
36476 .code
36477 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
36478 <low.club@bridge.example> R=userforward
36479 .endd
36480 is written, to record why no deliveries are logged. When a message is discarded
36481 because it is aliased to &":blackhole:"& the log line is like this:
36482 .code
36483 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
36484 <hole@nowhere.example> R=blackhole_router
36485 .endd
36486
36487
36488 .section "Deferred deliveries" "SECID254"
36489 When a delivery is deferred, a line of the following form is logged:
36490 .code
36491 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
36492 R=dnslookup T=smtp defer (146): Connection refused
36493 .endd
36494 In the case of remote deliveries, the error is the one that was given for the
36495 last IP address that was tried. Details of individual SMTP failures are also
36496 written to the log, so the above line would be preceded by something like
36497 .code
36498 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
36499 mail1.endrest.example [192.168.239.239]: Connection refused
36500 .endd
36501 When a deferred address is skipped because its retry time has not been reached,
36502 a message is written to the log, but this can be suppressed by setting an
36503 appropriate value in &%log_selector%&.
36504
36505
36506
36507 .section "Delivery failures" "SECID255"
36508 .cindex "delivery" "failure; logging"
36509 If a delivery fails because an address cannot be routed, a line of the
36510 following form is logged:
36511 .code
36512 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
36513 <jim@trek99.example>: unknown mail domain
36514 .endd
36515 If a delivery fails at transport time, the router and transport are shown, and
36516 the response from the remote host is included, as in this example:
36517 .code
36518 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
36519 R=dnslookup T=remote_smtp: SMTP error from remote mailer
36520 after pipelined RCPT TO:<ace400@pb.example>: host
36521 pbmail3.py.example [192.168.63.111]: 553 5.3.0
36522 <ace400@pb.example>...Addressee unknown
36523 .endd
36524 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
36525 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
36526 disabling PIPELINING. The log lines for all forms of delivery failure are
36527 flagged with &`**`&.
36528
36529
36530
36531 .section "Fake deliveries" "SECID256"
36532 .cindex "delivery" "fake; logging"
36533 If a delivery does not actually take place because the &%-N%& option has been
36534 used to suppress it, a normal delivery line is written to the log, except that
36535 &"=>"& is replaced by &"*>"&.
36536
36537
36538
36539 .section "Completion" "SECID257"
36540 A line of the form
36541 .code
36542 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
36543 .endd
36544 is written to the main log when a message is about to be removed from the spool
36545 at the end of its processing.
36546
36547
36548
36549
36550 .section "Summary of Fields in Log Lines" "SECID258"
36551 .cindex "log" "summary of fields"
36552 A summary of the field identifiers that are used in log lines is shown in
36553 the following table:
36554 .display
36555 &`A `& authenticator name (and optional id and sender)
36556 &`C `& SMTP confirmation on delivery
36557 &` `& command list for &"no mail in SMTP session"&
36558 &`CV `& certificate verification status
36559 &`D `& duration of &"no mail in SMTP session"&
36560 &`DKIM`& domain verified in incoming message
36561 &`DN `& distinguished name from peer certificate
36562 &`DS `& DNSSEC secured lookups
36563 &`DT `& on &`=>`& lines: time taken for a delivery
36564 &`F `& sender address (on delivery lines)
36565 &`H `& host name and IP address
36566 &`I `& local interface used
36567 &`id `& message id for incoming message
36568 &`K `& CHUNKING extension used
36569 &`L `& on &`<=`& and &`=>`& lines: PIPELINING extension offered or used
36570 &`M8S `& 8BITMIME status for incoming message
36571 &`P `& on &`<=`& lines: protocol used
36572 &` `& on &`=>`& and &`**`& lines: return path
36573 &`PRDR`& PRDR extension used
36574 &`PRX `& on &`<=`& and &`=>`& lines: proxy address
36575 &`Q `& alternate queue name
36576 &`QT `& on &`=>`& lines: time spent on queue so far
36577 &` `& on &"Completed"& lines: time spent on queue
36578 &`R `& on &`<=`& lines: reference for local bounce
36579 &` `& on &`=>`& &`>>`& &`**`& and &`==`& lines: router name
36580 &`RT `& on &`<=`& lines: time taken for reception
36581 &`S `& size of message in bytes
36582 &`SNI `& server name indication from TLS client hello
36583 &`ST `& shadow transport name
36584 &`T `& on &`<=`& lines: message subject (topic)
36585 &`TFO `& connection took advantage of TCP Fast Open
36586 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
36587 &`U `& local user or RFC 1413 identity
36588 &`X `& TLS cipher suite
36589 .endd
36590
36591
36592 .section "Other log entries" "SECID259"
36593 Various other types of log entry are written from time to time. Most should be
36594 self-explanatory. Among the more common are:
36595
36596 .ilist
36597 .cindex "retry" "time not reached"
36598 &'retry time not reached'&&~&~An address previously suffered a temporary error
36599 during routing or local delivery, and the time to retry has not yet arrived.
36600 This message is not written to an individual message log file unless it happens
36601 during the first delivery attempt.
36602 .next
36603 &'retry time not reached for any host'&&~&~An address previously suffered
36604 temporary errors during remote delivery, and the retry time has not yet arrived
36605 for any of the hosts to which it is routed.
36606 .next
36607 .cindex "spool directory" "file locked"
36608 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
36609 some other Exim process is already working on the message. This can be quite
36610 common if queue running processes are started at frequent intervals. The
36611 &'exiwhat'& utility script can be used to find out what Exim processes are
36612 doing.
36613 .next
36614 .cindex "error" "ignored"
36615 &'error ignored'&&~&~There are several circumstances that give rise to this
36616 message:
36617 .olist
36618 Exim failed to deliver a bounce message whose age was greater than
36619 &%ignore_bounce_errors_after%&. The bounce was discarded.
36620 .next
36621 A filter file set up a delivery using the &"noerror"& option, and the delivery
36622 failed. The delivery was discarded.
36623 .next
36624 A delivery set up by a router configured with
36625 . ==== As this is a nested list, any displays it contains must be indented
36626 . ==== as otherwise they are too far to the left.
36627 .code
36628 errors_to = <>
36629 .endd
36630 failed. The delivery was discarded.
36631 .endlist olist
36632 .next
36633 .cindex DKIM "log line"
36634 &'DKIM: d='&&~&~Verbose results of a DKIM verification attempt, if enabled for
36635 logging and the message has a DKIM signature header.
36636 .endlist ilist
36637
36638
36639
36640
36641
36642 .section "Reducing or increasing what is logged" "SECTlogselector"
36643 .cindex "log" "selectors"
36644 By setting the &%log_selector%& global option, you can disable some of Exim's
36645 default logging, or you can request additional logging. The value of
36646 &%log_selector%& is made up of names preceded by plus or minus characters. For
36647 example:
36648 .code
36649 log_selector = +arguments -retry_defer
36650 .endd
36651 The list of optional log items is in the following table, with the default
36652 selection marked by asterisks:
36653 .display
36654 &` 8bitmime `& received 8BITMIME status
36655 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
36656 &` address_rewrite `& address rewriting
36657 &` all_parents `& all parents in => lines
36658 &` arguments `& command line arguments
36659 &`*connection_reject `& connection rejections
36660 &`*delay_delivery `& immediate delivery delayed
36661 &` deliver_time `& time taken to perform delivery
36662 &` delivery_size `& add &`S=`&&'nnn'& to => lines
36663 &`*dkim `& DKIM verified domain on <= lines
36664 &` dkim_verbose `& separate full DKIM verification result line, per signature
36665 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
36666 &` dnssec `& DNSSEC secured lookups
36667 &`*etrn `& ETRN commands
36668 &`*host_lookup_failed `& as it says
36669 &` ident_timeout `& timeout for ident connection
36670 &` incoming_interface `& local interface on <= and => lines
36671 &` incoming_port `& remote port on <= lines
36672 &`*lost_incoming_connection `& as it says (includes timeouts)
36673 &` millisec `& millisecond timestamps and RT,QT,DT,D times
36674 &` outgoing_interface `& local interface on => lines
36675 &` outgoing_port `& add remote port to => lines
36676 &`*queue_run `& start and end queue runs
36677 &` queue_time `& time on queue for one recipient
36678 &` queue_time_overall `& time on queue for whole message
36679 &` pid `& Exim process id
36680 &` pipelining `& PIPELINING, advertisement on <= lines, use on => lines
36681 &` proxy `& proxy address on <= and => lines
36682 &` receive_time `& time taken to receive message
36683 &` received_recipients `& recipients on <= lines
36684 &` received_sender `& sender on <= lines
36685 &`*rejected_header `& header contents on reject log
36686 &`*retry_defer `& &"retry time not reached"&
36687 &` return_path_on_delivery `& put return path on => and ** lines
36688 &` sender_on_delivery `& add sender to => lines
36689 &`*sender_verify_fail `& sender verification failures
36690 &`*size_reject `& rejection because too big
36691 &`*skip_delivery `& delivery skipped in a queue run
36692 &`*smtp_confirmation `& SMTP confirmation on => lines
36693 &` smtp_connection `& incoming SMTP connections
36694 &` smtp_incomplete_transaction`& incomplete SMTP transactions
36695 &` smtp_mailauth `& AUTH argument to MAIL commands
36696 &` smtp_no_mail `& session with no MAIL commands
36697 &` smtp_protocol_error `& SMTP protocol errors
36698 &` smtp_syntax_error `& SMTP syntax errors
36699 &` subject `& contents of &'Subject:'& on <= lines
36700 &`*tls_certificate_verified `& certificate verification status
36701 &`*tls_cipher `& TLS cipher suite on <= and => lines
36702 &` tls_peerdn `& TLS peer DN on <= and => lines
36703 &` tls_sni `& TLS SNI on <= lines
36704 &` unknown_in_list `& DNS lookup failed in list match
36705
36706 &` all `& all of the above
36707 .endd
36708 See also the &%slow_lookup_log%& main configuration option,
36709 section &<<SECID99>>&
36710
36711 More details on each of these items follows:
36712
36713 .ilist
36714 .cindex "8BITMIME"
36715 .cindex "log" "8BITMIME"
36716 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
36717 which may help in tracking down interoperability issues with ancient MTAs
36718 that are not 8bit clean. This is added to the &"<="& line, tagged with
36719 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
36720 &`7BIT`& and &`8BITMIME`& respectively.
36721 .next
36722 .cindex "&%warn%& ACL verb" "log when skipping"
36723 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
36724 its conditions cannot be evaluated, a log line to this effect is written if
36725 this log selector is set.
36726 .next
36727 .cindex "log" "rewriting"
36728 .cindex "rewriting" "logging"
36729 &%address_rewrite%&: This applies both to global rewrites and per-transport
36730 rewrites, but not to rewrites in filters run as an unprivileged user (because
36731 such users cannot access the log).
36732 .next
36733 .cindex "log" "full parentage"
36734 &%all_parents%&: Normally only the original and final addresses are logged on
36735 delivery lines; with this selector, intermediate parents are given in
36736 parentheses between them.
36737 .next
36738 .cindex "log" "Exim arguments"
36739 .cindex "Exim arguments, logging"
36740 &%arguments%&: This causes Exim to write the arguments with which it was called
36741 to the main log, preceded by the current working directory. This is a debugging
36742 feature, added to make it easier to find out how certain MUAs call
36743 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
36744 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
36745 that are empty or that contain white space are quoted. Non-printing characters
36746 are shown as escape sequences. This facility cannot log unrecognized arguments,
36747 because the arguments are checked before the configuration file is read. The
36748 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
36749 between the caller and Exim.
36750 .next
36751 .cindex "log" "connection rejections"
36752 &%connection_reject%&: A log entry is written whenever an incoming SMTP
36753 connection is rejected, for whatever reason.
36754 .next
36755 .cindex "log" "delayed delivery"
36756 .cindex "delayed delivery, logging"
36757 &%delay_delivery%&: A log entry is written whenever a delivery process is not
36758 started for an incoming message because the load is too high or too many
36759 messages were received on one connection. Logging does not occur if no delivery
36760 process is started because &%queue_only%& is set or &%-odq%& was used.
36761 .next
36762 .cindex "log" "delivery duration"
36763 &%deliver_time%&: For each delivery, the amount of real time it has taken to
36764 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
36765 If millisecond logging is enabled, short times will be shown with greater
36766 precision, eg. &`DT=0.304s`&.
36767 .next
36768 .cindex "log" "message size on delivery"
36769 .cindex "size" "of message"
36770 &%delivery_size%&: For each delivery, the size of message delivered is added to
36771 the &"=>"& line, tagged with S=.
36772 .next
36773 .cindex log "DKIM verification"
36774 .cindex DKIM "verification logging"
36775 &%dkim%&: For message acceptance log lines, when an DKIM signature in the header
36776 verifies successfully a tag of DKIM is added, with one of the verified domains.
36777 .next
36778 .cindex log "DKIM verification"
36779 .cindex DKIM "verification logging"
36780 &%dkim_verbose%&: A log entry is written for each attempted DKIM verification.
36781 .next
36782 .cindex "log" "dnslist defer"
36783 .cindex "DNS list" "logging defer"
36784 .cindex "black list (DNS)"
36785 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
36786 DNS black list suffers a temporary error.
36787 .next
36788 .cindex log dnssec
36789 .cindex dnssec logging
36790 &%dnssec%&: For message acceptance and (attempted) delivery log lines, when
36791 dns lookups gave secure results a tag of DS is added.
36792 For acceptance this covers the reverse and forward lookups for host name verification.
36793 It does not cover helo-name verification.
36794 For delivery this covers the SRV, MX, A and/or AAAA lookups.
36795 .next
36796 .cindex "log" "ETRN commands"
36797 .cindex "ETRN" "logging"
36798 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
36799 is run to determine whether or not it is actually accepted. An invalid ETRN
36800 command, or one received within a message transaction is not logged by this
36801 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
36802 .next
36803 .cindex "log" "host lookup failure"
36804 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
36805 any addresses, or when a lookup of an IP address fails to find a host name, a
36806 log line is written. This logging does not apply to direct DNS lookups when
36807 routing email addresses, but it does apply to &"byname"& lookups.
36808 .next
36809 .cindex "log" "ident timeout"
36810 .cindex "RFC 1413" "logging timeout"
36811 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
36812 client's ident port times out.
36813 .next
36814 .cindex "log" "incoming interface"
36815 .cindex "log" "local interface"
36816 .cindex "log" "local address and port"
36817 .cindex "TCP/IP" "logging local address and port"
36818 .cindex "interface" "logging"
36819 &%incoming_interface%&: The interface on which a message was received is added
36820 to the &"<="& line as an IP address in square brackets, tagged by I= and
36821 followed by a colon and the port number. The local interface and port are also
36822 added to other SMTP log lines, for example &"SMTP connection from"&, to
36823 rejection lines, and (despite the name) to outgoing &"=>"& and &"->"& lines.
36824 The latter can be disabled by turning off the &%outgoing_interface%& option.
36825 .next
36826 .cindex log "incoming proxy address"
36827 .cindex proxy "logging proxy address"
36828 .cindex "TCP/IP" "logging proxy address"
36829 &%proxy%&: The internal (closest to the system running Exim) IP address
36830 of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
36831 on a proxied connection
36832 or the &"=>"& line for a message delivered on a proxied connection.
36833 See &<<SECTproxyInbound>>& for more information.
36834 .next
36835 .cindex "log" "incoming remote port"
36836 .cindex "port" "logging remote"
36837 .cindex "TCP/IP" "logging incoming remote port"
36838 .vindex "&$sender_fullhost$&"
36839 .vindex "&$sender_rcvhost$&"
36840 &%incoming_port%&: The remote port number from which a message was received is
36841 added to log entries and &'Received:'& header lines, following the IP address
36842 in square brackets, and separated from it by a colon. This is implemented by
36843 changing the value that is put in the &$sender_fullhost$& and
36844 &$sender_rcvhost$& variables. Recording the remote port number has become more
36845 important with the widening use of NAT (see RFC 2505).
36846 .next
36847 .cindex "log" "dropped connection"
36848 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
36849 connection is unexpectedly dropped.
36850 .next
36851 .cindex "log" "millisecond timestamps"
36852 .cindex millisecond logging
36853 .cindex timestamps "millisecond, in logs"
36854 &%millisec%&: Timestamps have a period and three decimal places of finer granularity
36855 appended to the seconds value.
36856 .next
36857 .cindex "log" "outgoing interface"
36858 .cindex "log" "local interface"
36859 .cindex "log" "local address and port"
36860 .cindex "TCP/IP" "logging local address and port"
36861 .cindex "interface" "logging"
36862 &%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
36863 interface on which a message was sent is added to delivery lines as an I= tag
36864 followed by IP address in square brackets. You can disable this by turning
36865 off the &%outgoing_interface%& option.
36866 .next
36867 .cindex "log" "outgoing remote port"
36868 .cindex "port" "logging outgoing remote"
36869 .cindex "TCP/IP" "logging outgoing remote port"
36870 &%outgoing_port%&: The remote port number is added to delivery log lines (those
36871 containing => tags) following the IP address.
36872 The local port is also added if &%incoming_interface%& and
36873 &%outgoing_interface%& are both enabled.
36874 This option is not included in the default setting, because for most ordinary
36875 configurations, the remote port number is always 25 (the SMTP port), and the
36876 local port is a random ephemeral port.
36877 .next
36878 .cindex "log" "process ids in"
36879 .cindex "pid (process id)" "in log lines"
36880 &%pid%&: The current process id is added to every log line, in square brackets,
36881 immediately after the time and date.
36882 .next
36883 .cindex log pipelining
36884 .cindex pipelining "logging outgoing"
36885 &%pipelining%&: A field is added to delivery and accept
36886 log lines when the ESMTP PIPELINING extension was used.
36887 The field is a single "L".
36888 .next
36889 .cindex "log" "queue run"
36890 .cindex "queue runner" "logging"
36891 &%queue_run%&: The start and end of every queue run are logged.
36892 .next
36893 .cindex "log" "queue time"
36894 &%queue_time%&: The amount of time the message has been in the queue on the
36895 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
36896 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
36897 includes reception time as well as the delivery time for the current address.
36898 This means that it may be longer than the difference between the arrival and
36899 delivery log line times, because the arrival log line is not written until the
36900 message has been successfully received.
36901 If millisecond logging is enabled, short times will be shown with greater
36902 precision, eg. &`QT=1.578s`&.
36903 .next
36904 &%queue_time_overall%&: The amount of time the message has been in the queue on
36905 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
36906 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
36907 message, so it includes reception time as well as the total delivery time.
36908 .next
36909 .cindex "log" "receive duration"
36910 &%receive_time%&: For each message, the amount of real time it has taken to
36911 perform the reception is logged as RT=<&'time'&>, for example, &`RT=1s`&.
36912 If millisecond logging is enabled, short times will be shown with greater
36913 precision, eg. &`RT=0.204s`&.
36914 .next
36915 .cindex "log" "recipients"
36916 &%received_recipients%&: The recipients of a message are listed in the main log
36917 as soon as the message is received. The list appears at the end of the log line
36918 that is written when a message is received, preceded by the word &"for"&. The
36919 addresses are listed after they have been qualified, but before any rewriting
36920 has taken place.
36921 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
36922 in the list.
36923 .next
36924 .cindex "log" "sender reception"
36925 &%received_sender%&: The unrewritten original sender of a message is added to
36926 the end of the log line that records the message's arrival, after the word
36927 &"from"& (before the recipients if &%received_recipients%& is also set).
36928 .next
36929 .cindex "log" "header lines for rejection"
36930 &%rejected_header%&: If a message's header has been received at the time a
36931 rejection is written to the reject log, the complete header is added to the
36932 log. Header logging can be turned off individually for messages that are
36933 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
36934 .next
36935 .cindex "log" "retry defer"
36936 &%retry_defer%&: A log line is written if a delivery is deferred because a
36937 retry time has not yet been reached. However, this &"retry time not reached"&
36938 message is always omitted from individual message logs after the first delivery
36939 attempt.
36940 .next
36941 .cindex "log" "return path"
36942 &%return_path_on_delivery%&: The return path that is being transmitted with
36943 the message is included in delivery and bounce lines, using the tag P=.
36944 This is omitted if no delivery actually happens, for example, if routing fails,
36945 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
36946 .next
36947 .cindex "log" "sender on delivery"
36948 &%sender_on_delivery%&: The message's sender address is added to every delivery
36949 and bounce line, tagged by F= (for &"from"&).
36950 This is the original sender that was received with the message; it is not
36951 necessarily the same as the outgoing return path.
36952 .next
36953 .cindex "log" "sender verify failure"
36954 &%sender_verify_fail%&: If this selector is unset, the separate log line that
36955 gives details of a sender verification failure is not written. Log lines for
36956 the rejection of SMTP commands contain just &"sender verify failed"&, so some
36957 detail is lost.
36958 .next
36959 .cindex "log" "size rejection"
36960 &%size_reject%&: A log line is written whenever a message is rejected because
36961 it is too big.
36962 .next
36963 .cindex "log" "frozen messages; skipped"
36964 .cindex "frozen messages" "logging skipping"
36965 &%skip_delivery%&: A log line is written whenever a message is skipped during a
36966 queue run because it is frozen or because another process is already delivering
36967 it.
36968 .cindex "&""spool file is locked""&"
36969 The message that is written is &"spool file is locked"&.
36970 .next
36971 .cindex "log" "smtp confirmation"
36972 .cindex "SMTP" "logging confirmation"
36973 .cindex "LMTP" "logging confirmation"
36974 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
36975 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
36976 A number of MTAs (including Exim) return an identifying string in this
36977 response.
36978 .next
36979 .cindex "log" "SMTP connections"
36980 .cindex "SMTP" "logging connections"
36981 &%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
36982 established or closed, unless the connection is from a host that matches
36983 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
36984 only when the closure is unexpected.) This applies to connections from local
36985 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
36986 dropped in the middle of a message, a log line is always written, whether or
36987 not this selector is set, but otherwise nothing is written at the start and end
36988 of connections unless this selector is enabled.
36989
36990 For TCP/IP connections to an Exim daemon, the current number of connections is
36991 included in the log message for each new connection, but note that the count is
36992 reset if the daemon is restarted.
36993 Also, because connections are closed (and the closure is logged) in
36994 subprocesses, the count may not include connections that have been closed but
36995 whose termination the daemon has not yet noticed. Thus, while it is possible to
36996 match up the opening and closing of connections in the log, the value of the
36997 logged counts may not be entirely accurate.
36998 .next
36999 .cindex "log" "SMTP transaction; incomplete"
37000 .cindex "SMTP" "logging incomplete transactions"
37001 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
37002 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
37003 and the message sender plus any accepted recipients are included in the log
37004 line. This can provide evidence of dictionary attacks.
37005 .next
37006 .cindex "log" "non-MAIL SMTP sessions"
37007 .cindex "MAIL" "logging session without"
37008 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
37009 connection terminates without having issued a MAIL command. This includes both
37010 the case when the connection is dropped, and the case when QUIT is used. It
37011 does not include cases where the connection is rejected right at the start (by
37012 an ACL, or because there are too many connections, or whatever). These cases
37013 already have their own log lines.
37014
37015 The log line that is written contains the identity of the client in the usual
37016 way, followed by D= and a time, which records the duration of the connection.
37017 If the connection was authenticated, this fact is logged exactly as it is for
37018 an incoming message, with an A= item. If the connection was encrypted, CV=,
37019 DN=, and X= items may appear as they do for an incoming message, controlled by
37020 the same logging options.
37021
37022 Finally, if any SMTP commands were issued during the connection, a C= item
37023 is added to the line, listing the commands that were used. For example,
37024 .code
37025 C=EHLO,QUIT
37026 .endd
37027 shows that the client issued QUIT straight after EHLO. If there were fewer
37028 than 20 commands, they are all listed. If there were more than 20 commands,
37029 the last 20 are listed, preceded by &"..."&. However, with the default
37030 setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
37031 have been aborted before 20 non-mail commands are processed.
37032 .next
37033 &%smtp_mailauth%&: A third subfield with the authenticated sender,
37034 colon-separated, is appended to the A= item for a message arrival or delivery
37035 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
37036 was accepted or used.
37037 .next
37038 .cindex "log" "SMTP protocol error"
37039 .cindex "SMTP" "logging protocol error"
37040 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
37041 encountered. Exim does not have perfect detection of all protocol errors
37042 because of transmission delays and the use of pipelining. If PIPELINING has
37043 been advertised to a client, an Exim server assumes that the client will use
37044 it, and therefore it does not count &"expected"& errors (for example, RCPT
37045 received after rejecting MAIL) as protocol errors.
37046 .next
37047 .cindex "SMTP" "logging syntax errors"
37048 .cindex "SMTP" "syntax errors; logging"
37049 .cindex "SMTP" "unknown command; logging"
37050 .cindex "log" "unknown SMTP command"
37051 .cindex "log" "SMTP syntax error"
37052 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
37053 encountered. An unrecognized command is treated as a syntax error. For an
37054 external connection, the host identity is given; for an internal connection
37055 using &%-bs%& the sender identification (normally the calling user) is given.
37056 .next
37057 .cindex "log" "subject"
37058 .cindex "subject, logging"
37059 &%subject%&: The subject of the message is added to the arrival log line,
37060 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
37061 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
37062 specifies whether characters with values greater than 127 should be logged
37063 unchanged, or whether they should be rendered as escape sequences.
37064 .next
37065 .cindex "log" "certificate verification"
37066 .cindex log DANE
37067 .cindex DANE logging
37068 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
37069 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
37070 verified
37071 using a CA trust anchor,
37072 &`CA=dane`& if using a DNS trust anchor,
37073 and &`CV=no`& if not.
37074 .next
37075 .cindex "log" "TLS cipher"
37076 .cindex "TLS" "logging cipher"
37077 &%tls_cipher%&: When a message is sent or received over an encrypted
37078 connection, the cipher suite used is added to the log line, preceded by X=.
37079 .next
37080 .cindex "log" "TLS peer DN"
37081 .cindex "TLS" "logging peer DN"
37082 &%tls_peerdn%&: When a message is sent or received over an encrypted
37083 connection, and a certificate is supplied by the remote host, the peer DN is
37084 added to the log line, preceded by DN=.
37085 .next
37086 .cindex "log" "TLS SNI"
37087 .cindex "TLS" "logging SNI"
37088 &%tls_sni%&: When a message is received over an encrypted connection, and
37089 the remote host provided the Server Name Indication extension, the SNI is
37090 added to the log line, preceded by SNI=.
37091 .next
37092 .cindex "log" "DNS failure in list"
37093 &%unknown_in_list%&: This setting causes a log entry to be written when the
37094 result of a list match is failure because a DNS lookup failed.
37095 .endlist
37096
37097
37098 .section "Message log" "SECID260"
37099 .cindex "message" "log file for"
37100 .cindex "log" "message log; description of"
37101 .cindex "&_msglog_& directory"
37102 .oindex "&%preserve_message_logs%&"
37103 In addition to the general log files, Exim writes a log file for each message
37104 that it handles. The names of these per-message logs are the message ids, and
37105 they are kept in the &_msglog_& sub-directory of the spool directory. Each
37106 message log contains copies of the log lines that apply to the message. This
37107 makes it easier to inspect the status of an individual message without having
37108 to search the main log. A message log is deleted when processing of the message
37109 is complete, unless &%preserve_message_logs%& is set, but this should be used
37110 only with great care because they can fill up your disk very quickly.
37111
37112 On a heavily loaded system, it may be desirable to disable the use of
37113 per-message logs, in order to reduce disk I/O. This can be done by setting the
37114 &%message_logs%& option false.
37115 .ecindex IIDloggen
37116
37117
37118
37119
37120 . ////////////////////////////////////////////////////////////////////////////
37121 . ////////////////////////////////////////////////////////////////////////////
37122
37123 .chapter "Exim utilities" "CHAPutils"
37124 .scindex IIDutils "utilities"
37125 A number of utility scripts and programs are supplied with Exim and are
37126 described in this chapter. There is also the Exim Monitor, which is covered in
37127 the next chapter. The utilities described here are:
37128
37129 .itable none 0 0 3 7* left 15* left 40* left
37130 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
37131 "list what Exim processes are doing"
37132 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
37133 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
37134 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
37135 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
37136 various criteria"
37137 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
37138 .irow &<<SECTmailstat>>& &'eximstats'& &&&
37139 "extract statistics from the log"
37140 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
37141 "check address acceptance from given IP"
37142 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
37143 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
37144 .irow &<<SECThindatmai>>& &'exim_dumpdb'& "dump a hints database"
37145 .irow &<<SECThindatmai>>& &'exim_tidydb'& "clean up a hints database"
37146 .irow &<<SECThindatmai>>& &'exim_fixdb'& "patch a hints database"
37147 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
37148 .endtable
37149
37150 Another utility that might be of use to sites with many MTAs is Tom Kistner's
37151 &'exilog'&. It provides log visualizations across multiple Exim servers. See
37152 &url(http://duncanthrax.net/exilog/) for details.
37153
37154
37155
37156
37157 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
37158 .cindex "&'exiwhat'&"
37159 .cindex "process, querying"
37160 .cindex "SIGUSR1"
37161 On operating systems that can restart a system call after receiving a signal
37162 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
37163 a line describing what it is doing to the file &_exim-process.info_& in the
37164 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
37165 processes it can find, having first emptied the file. It then waits for one
37166 second to allow the Exim processes to react before displaying the results. In
37167 order to run &'exiwhat'& successfully you have to have sufficient privilege to
37168 send the signal to the Exim processes, so it is normally run as root.
37169
37170 &*Warning*&: This is not an efficient process. It is intended for occasional
37171 use by system administrators. It is not sensible, for example, to set up a
37172 script that sends SIGUSR1 signals to Exim processes at short intervals.
37173
37174
37175 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
37176 varies in different operating systems. Not only are different options used,
37177 but the format of the output is different. For this reason, there are some
37178 system configuration options that configure exactly how &'exiwhat'& works. If
37179 it doesn't seem to be working for you, check the following compile-time
37180 options:
37181 .display
37182 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
37183 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
37184 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
37185 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
37186 .endd
37187 An example of typical output from &'exiwhat'& is
37188 .code
37189 164 daemon: -q1h, listening on port 25
37190 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
37191 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
37192 [10.19.42.42] (editor@ref.example)
37193 10592 handling incoming call from [192.168.243.242]
37194 10628 accepting a local non-SMTP message
37195 .endd
37196 The first number in the output line is the process number. The third line has
37197 been split here, in order to fit it on the page.
37198
37199
37200
37201 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
37202 .cindex "&'exiqgrep'&"
37203 .cindex "queue" "grepping"
37204 This utility is a Perl script contributed by Matt Hubbard. It runs
37205 .code
37206 exim -bpu
37207 .endd
37208 or (in case &*-a*& switch is specified)
37209 .code
37210 exim -bp
37211 .endd
37212 The &*-C*& option is used to specify an alternate &_exim.conf_& which might
37213 contain alternate exim configuration the queue management might be using.
37214
37215 to obtain a queue listing, and then greps the output to select messages
37216 that match given criteria. The following selection options are available:
37217
37218 .vlist
37219 .vitem &*-f*&&~<&'regex'&>
37220 Match the sender address using a case-insensitive search. The field that is
37221 tested is enclosed in angle brackets, so you can test for bounce messages with
37222 .code
37223 exiqgrep -f '^<>$'
37224 .endd
37225 .vitem &*-r*&&~<&'regex'&>
37226 Match a recipient address using a case-insensitive search. The field that is
37227 tested is not enclosed in angle brackets.
37228
37229 .vitem &*-s*&&~<&'regex'&>
37230 Match against the size field.
37231
37232 .vitem &*-y*&&~<&'seconds'&>
37233 Match messages that are younger than the given time.
37234
37235 .vitem &*-o*&&~<&'seconds'&>
37236 Match messages that are older than the given time.
37237
37238 .vitem &*-z*&
37239 Match only frozen messages.
37240
37241 .vitem &*-x*&
37242 Match only non-frozen messages.
37243 .endlist
37244
37245 The following options control the format of the output:
37246
37247 .vlist
37248 .vitem &*-c*&
37249 Display only the count of matching messages.
37250
37251 .vitem &*-l*&
37252 Long format &-- display the full message information as output by Exim. This is
37253 the default.
37254
37255 .vitem &*-i*&
37256 Display message ids only.
37257
37258 .vitem &*-b*&
37259 Brief format &-- one line per message.
37260
37261 .vitem &*-R*&
37262 Display messages in reverse order.
37263
37264 .vitem &*-a*&
37265 Include delivered recipients in queue listing.
37266 .endlist
37267
37268 There is one more option, &%-h%&, which outputs a list of options.
37269
37270
37271
37272 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
37273 .cindex "&'exiqsumm'&"
37274 .cindex "queue" "summary"
37275 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
37276 -bp`& and produces a summary of the messages on the queue. Thus, you use it by
37277 running a command such as
37278 .code
37279 exim -bp | exiqsumm
37280 .endd
37281 The output consists of one line for each domain that has messages waiting for
37282 it, as in the following example:
37283 .code
37284 3 2322 74m 66m msn.com.example
37285 .endd
37286 Each line lists the number of pending deliveries for a domain, their total
37287 volume, and the length of time that the oldest and the newest messages have
37288 been waiting. Note that the number of pending deliveries is greater than the
37289 number of messages when messages have more than one recipient.
37290
37291 A summary line is output at the end. By default the output is sorted on the
37292 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
37293 the output to be sorted by oldest message and by count of messages,
37294 respectively. There are also three options that split the messages for each
37295 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
37296 separates frozen messages, and &%-s%& separates messages according to their
37297 sender.
37298
37299 The output of &'exim -bp'& contains the original addresses in the message, so
37300 this also applies to the output from &'exiqsumm'&. No domains from addresses
37301 generated by aliasing or forwarding are included (unless the &%one_time%&
37302 option of the &(redirect)& router has been used to convert them into &"top
37303 level"& addresses).
37304
37305
37306
37307
37308 .section "Extracting specific information from the log (exigrep)" &&&
37309 "SECTextspeinf"
37310 .cindex "&'exigrep'&"
37311 .cindex "log" "extracts; grepping for"
37312 The &'exigrep'& utility is a Perl script that searches one or more main log
37313 files for entries that match a given pattern. When it finds a match, it
37314 extracts all the log entries for the relevant message, not just those that
37315 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
37316 given message, or all mail for a given user, or for a given host, for example.
37317 The input files can be in Exim log format or syslog format.
37318 If a matching log line is not associated with a specific message, it is
37319 included in &'exigrep'&'s output without any additional lines. The usage is:
37320 .display
37321 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
37322 .endd
37323 If no log file names are given on the command line, the standard input is read.
37324
37325 The &%-t%& argument specifies a number of seconds. It adds an additional
37326 condition for message selection. Messages that are complete are shown only if
37327 they spent more than <&'n'&> seconds on the queue.
37328
37329 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
37330 makes it case-sensitive. This may give a performance improvement when searching
37331 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
37332 option; with &%-I%& they do not. In both cases it is possible to change the
37333 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
37334
37335 The &%-l%& option means &"literal"&, that is, treat all characters in the
37336 pattern as standing for themselves. Otherwise the pattern must be a Perl
37337 regular expression.
37338
37339 The &%-v%& option inverts the matching condition. That is, a line is selected
37340 if it does &'not'& match the pattern.
37341
37342 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
37343 that are generated as a result/response to a message that &'exigrep'& matched
37344 normally.
37345
37346 Example of &%-M%&:
37347 user_a sends a message to user_b, which generates a bounce back to user_b. If
37348 &'exigrep'& is used to search for &"user_a"&, only the first message will be
37349 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
37350 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
37351 when searching for &"user_a"& will show both messages since the bounce is
37352 &"related"& to or a &"result"& of the first message that was found by the
37353 search term.
37354
37355 If the location of a &'zcat'& command is known from the definition of
37356 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
37357 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
37358 If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
37359 autodetection of some well known compression extensions.
37360
37361
37362 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
37363 .cindex "&'exipick'&"
37364 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
37365 lists messages from the queue according to a variety of criteria. For details
37366 of &'exipick'&'s facilities, run &'exipick'& with
37367 the &%--help%& option.
37368
37369
37370 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
37371 .cindex "log" "cycling local files"
37372 .cindex "cycling logs"
37373 .cindex "&'exicyclog'&"
37374 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
37375 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
37376 you are using log files with datestamps in their names (see section
37377 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
37378 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
37379 There are two command line options for &'exicyclog'&:
37380 .ilist
37381 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
37382 default that is set when Exim is built. The default default is 10.
37383 .next
37384 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
37385 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
37386 overriding the script's default, which is to find the setting from Exim's
37387 configuration.
37388 .endlist
37389
37390 Each time &'exicyclog'& is run the file names get &"shuffled down"& by one. If
37391 the main log file name is &_mainlog_& (the default) then when &'exicyclog'& is
37392 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
37393 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
37394 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
37395 logs are handled similarly.
37396
37397 If the limit is greater than 99, the script uses 3-digit numbers such as
37398 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
37399 to one that is greater, or &'vice versa'&, you will have to fix the names of
37400 any existing log files.
37401
37402 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
37403 the end are deleted. All files with numbers greater than 01 are compressed,
37404 using a compression command which is configured by the COMPRESS_COMMAND
37405 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
37406 root &%crontab%& entry of the form
37407 .code
37408 1 0 * * * su exim -c /usr/exim/bin/exicyclog
37409 .endd
37410 assuming you have used the name &"exim"& for the Exim user. You can run
37411 &'exicyclog'& as root if you wish, but there is no need.
37412
37413
37414
37415 .section "Mail statistics (eximstats)" "SECTmailstat"
37416 .cindex "statistics"
37417 .cindex "&'eximstats'&"
37418 A Perl script called &'eximstats'& is provided for extracting statistical
37419 information from log files. The output is either plain text, or HTML.
37420 Exim log files are also supported by the &'Lire'& system produced by the
37421 LogReport Foundation &url(http://www.logreport.org).
37422
37423 The &'eximstats'& script has been hacked about quite a bit over time. The
37424 latest version is the result of some extensive revision by Steve Campbell. A
37425 lot of information is given by default, but there are options for suppressing
37426 various parts of it. Following any options, the arguments to the script are a
37427 list of files, which should be main log files. For example:
37428 .code
37429 eximstats -nr /var/spool/exim/log/mainlog.01
37430 .endd
37431 By default, &'eximstats'& extracts information about the number and volume of
37432 messages received from or delivered to various hosts. The information is sorted
37433 both by message count and by volume, and the top fifty hosts in each category
37434 are listed on the standard output. Similar information, based on email
37435 addresses or domains instead of hosts can be requested by means of various
37436 options. For messages delivered and received locally, similar statistics are
37437 also produced per user.
37438
37439 The output also includes total counts and statistics about delivery errors, and
37440 histograms showing the number of messages received and deliveries made in each
37441 hour of the day. A delivery with more than one address in its envelope (for
37442 example, an SMTP transaction with more than one RCPT command) is counted
37443 as a single delivery by &'eximstats'&.
37444
37445 Though normally more deliveries than receipts are reported (as messages may
37446 have multiple recipients), it is possible for &'eximstats'& to report more
37447 messages received than delivered, even though the queue is empty at the start
37448 and end of the period in question. If an incoming message contains no valid
37449 recipients, no deliveries are recorded for it. A bounce message is handled as
37450 an entirely separate message.
37451
37452 &'eximstats'& always outputs a grand total summary giving the volume and number
37453 of messages received and deliveries made, and the number of hosts involved in
37454 each case. It also outputs the number of messages that were delayed (that is,
37455 not completely delivered at the first attempt), and the number that had at
37456 least one address that failed.
37457
37458 The remainder of the output is in sections that can be independently disabled
37459 or modified by various options. It consists of a summary of deliveries by
37460 transport, histograms of messages received and delivered per time interval
37461 (default per hour), information about the time messages spent on the queue,
37462 a list of relayed messages, lists of the top fifty sending hosts, local
37463 senders, destination hosts, and destination local users by count and by volume,
37464 and a list of delivery errors that occurred.
37465
37466 The relay information lists messages that were actually relayed, that is, they
37467 came from a remote host and were directly delivered to some other remote host,
37468 without being processed (for example, for aliasing or forwarding) locally.
37469
37470 There are quite a few options for &'eximstats'& to control exactly what it
37471 outputs. These are documented in the Perl script itself, and can be extracted
37472 by running the command &(perldoc)& on the script. For example:
37473 .code
37474 perldoc /usr/exim/bin/eximstats
37475 .endd
37476
37477 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
37478 .cindex "&'exim_checkaccess'&"
37479 .cindex "policy control" "checking access"
37480 .cindex "checking access"
37481 The &%-bh%& command line argument allows you to run a fake SMTP session with
37482 debugging output, in order to check what Exim is doing when it is applying
37483 policy controls to incoming SMTP mail. However, not everybody is sufficiently
37484 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
37485 sometimes you just want to answer the question &"Does this address have
37486 access?"& without bothering with any further details.
37487
37488 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
37489 two arguments, an IP address and an email address:
37490 .code
37491 exim_checkaccess 10.9.8.7 A.User@a.domain.example
37492 .endd
37493 The utility runs a call to Exim with the &%-bh%& option, to test whether the
37494 given email address would be accepted in a RCPT command in a TCP/IP
37495 connection from the host with the given IP address. The output of the utility
37496 is either the word &"accepted"&, or the SMTP error response, for example:
37497 .code
37498 Rejected:
37499 550 Relay not permitted
37500 .endd
37501 When running this test, the utility uses &`<>`& as the envelope sender address
37502 for the MAIL command, but you can change this by providing additional
37503 options. These are passed directly to the Exim command. For example, to specify
37504 that the test is to be run with the sender address &'himself@there.example'&
37505 you can use:
37506 .code
37507 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
37508 -f himself@there.example
37509 .endd
37510 Note that these additional Exim command line items must be given after the two
37511 mandatory arguments.
37512
37513 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
37514 while running its checks. You can run checks that include callouts by using
37515 &%-bhc%&, but this is not yet available in a &"packaged"& form.
37516
37517
37518
37519 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
37520 .cindex "DBM" "building dbm files"
37521 .cindex "building DBM files"
37522 .cindex "&'exim_dbmbuild'&"
37523 .cindex "lower casing"
37524 .cindex "binary zero" "in lookup key"
37525 The &'exim_dbmbuild'& program reads an input file containing keys and data in
37526 the format used by the &(lsearch)& lookup (see section
37527 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
37528 names as keys and the remainder of the information as data. The lower-casing
37529 can be prevented by calling the program with the &%-nolc%& option.
37530
37531 A terminating zero is included as part of the key string. This is expected by
37532 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
37533 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
37534 strings or the data strings. The &(dbmnz)& lookup type can be used with such
37535 files.
37536
37537 The program requires two arguments: the name of the input file (which can be a
37538 single hyphen to indicate the standard input), and the name of the output file.
37539 It creates the output under a temporary name, and then renames it if all went
37540 well.
37541
37542 .cindex "USE_DB"
37543 If the native DB interface is in use (USE_DB is set in a compile-time
37544 configuration file &-- this is common in free versions of Unix) the two file
37545 names must be different, because in this mode the Berkeley DB functions create
37546 a single output file using exactly the name given. For example,
37547 .code
37548 exim_dbmbuild /etc/aliases /etc/aliases.db
37549 .endd
37550 reads the system alias file and creates a DBM version of it in
37551 &_/etc/aliases.db_&.
37552
37553 In systems that use the &'ndbm'& routines (mostly proprietary versions of
37554 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
37555 environment, the suffixes are added to the second argument of
37556 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
37557 when the Berkeley functions are used in compatibility mode (though this is not
37558 recommended), because in that case it adds a &_.db_& suffix to the file name.
37559
37560 If a duplicate key is encountered, the program outputs a warning, and when it
37561 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
37562 option is used. By default, only the first of a set of duplicates is used &--
37563 this makes it compatible with &(lsearch)& lookups. There is an option
37564 &%-lastdup%& which causes it to use the data for the last duplicate instead.
37565 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
37566 &%stderr%&. For other errors, where it doesn't actually make a new file, the
37567 return code is 2.
37568
37569
37570
37571
37572 .section "Finding individual retry times (exinext)" "SECTfinindret"
37573 .cindex "retry" "times"
37574 .cindex "&'exinext'&"
37575 A utility called &'exinext'& (mostly a Perl script) provides the ability to
37576 fish specific information out of the retry database. Given a mail domain (or a
37577 complete address), it looks up the hosts for that domain, and outputs any retry
37578 information for the hosts or for the domain. At present, the retry information
37579 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
37580 output. For example:
37581 .code
37582 $ exinext piglet@milne.fict.example
37583 kanga.milne.example:192.168.8.1 error 146: Connection refused
37584 first failed: 21-Feb-1996 14:57:34
37585 last tried: 21-Feb-1996 14:57:34
37586 next try at: 21-Feb-1996 15:02:34
37587 roo.milne.example:192.168.8.3 error 146: Connection refused
37588 first failed: 20-Jan-1996 13:12:08
37589 last tried: 21-Feb-1996 11:42:03
37590 next try at: 21-Feb-1996 19:42:03
37591 past final cutoff time
37592 .endd
37593 You can also give &'exinext'& a local part, without a domain, and it
37594 will give any retry information for that local part in your default domain.
37595 A message id can be used to obtain retry information pertaining to a specific
37596 message. This exists only when an attempt to deliver a message to a remote host
37597 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
37598 &'exinext'& is not particularly efficient, but then it is not expected to be
37599 run very often.
37600
37601 The &'exinext'& utility calls Exim to find out information such as the location
37602 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
37603 passed on to the &'exim'& commands. The first specifies an alternate Exim
37604 configuration file, and the second sets macros for use within the configuration
37605 file. These features are mainly to help in testing, but might also be useful in
37606 environments where more than one configuration file is in use.
37607
37608
37609
37610 .section "Hints database maintenance" "SECThindatmai"
37611 .cindex "hints database" "maintenance"
37612 .cindex "maintaining Exim's hints database"
37613 Three utility programs are provided for maintaining the DBM files that Exim
37614 uses to contain its delivery hint information. Each program requires two
37615 arguments. The first specifies the name of Exim's spool directory, and the
37616 second is the name of the database it is to operate on. These are as follows:
37617
37618 .ilist
37619 &'retry'&: the database of retry information
37620 .next
37621 &'wait-'&<&'transport name'&>: databases of information about messages waiting
37622 for remote hosts
37623 .next
37624 &'callout'&: the callout cache
37625 .next
37626 &'ratelimit'&: the data for implementing the ratelimit ACL condition
37627 .next
37628 &'misc'&: other hints data
37629 .endlist
37630
37631 The &'misc'& database is used for
37632
37633 .ilist
37634 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
37635 .next
37636 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
37637 &(smtp)& transport)
37638 .next
37639 Limiting the concurrency of specific transports (when &%max_parallel%& is set
37640 in a transport)
37641 .endlist
37642
37643
37644
37645 .section "exim_dumpdb" "SECID261"
37646 .cindex "&'exim_dumpdb'&"
37647 The entire contents of a database are written to the standard output by the
37648 &'exim_dumpdb'& program, which has no options or arguments other than the
37649 spool and database names. For example, to dump the retry database:
37650 .code
37651 exim_dumpdb /var/spool/exim retry
37652 .endd
37653 Two lines of output are produced for each entry:
37654 .code
37655 T:mail.ref.example:192.168.242.242 146 77 Connection refused
37656 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
37657 .endd
37658 The first item on the first line is the key of the record. It starts with one
37659 of the letters R, or T, depending on whether it refers to a routing or
37660 transport retry. For a local delivery, the next part is the local address; for
37661 a remote delivery it is the name of the remote host, followed by its failing IP
37662 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
37663 transport). If the remote port is not the standard one (port 25), it is added
37664 to the IP address. Then there follows an error code, an additional error code,
37665 and a textual description of the error.
37666
37667 The three times on the second line are the time of first failure, the time of
37668 the last delivery attempt, and the computed time for the next attempt. The line
37669 ends with an asterisk if the cutoff time for the last retry rule has been
37670 exceeded.
37671
37672 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
37673 consists of a host name followed by a list of ids for messages that are or were
37674 waiting to be delivered to that host. If there are a very large number for any
37675 one host, continuation records, with a sequence number added to the host name,
37676 may be seen. The data in these records is often out of date, because a message
37677 may be routed to several alternative hosts, and Exim makes no effort to keep
37678 cross-references.
37679
37680
37681
37682 .section "exim_tidydb" "SECID262"
37683 .cindex "&'exim_tidydb'&"
37684 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
37685 database. If run with no options, it removes all records that are more than 30
37686 days old. The age is calculated from the date and time that the record was last
37687 updated. Note that, in the case of the retry database, it is &'not'& the time
37688 since the first delivery failure. Information about a host that has been down
37689 for more than 30 days will remain in the database, provided that the record is
37690 updated sufficiently often.
37691
37692 The cutoff date can be altered by means of the &%-t%& option, which must be
37693 followed by a time. For example, to remove all records older than a week from
37694 the retry database:
37695 .code
37696 exim_tidydb -t 7d /var/spool/exim retry
37697 .endd
37698 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
37699 message ids. In the former these appear as data in records keyed by host &--
37700 they were messages that were waiting for that host &-- and in the latter they
37701 are the keys for retry information for messages that have suffered certain
37702 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
37703 message ids in database records are those of messages that are still on the
37704 queue. Message ids for messages that no longer exist are removed from
37705 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
37706 For the &'retry'& database, records whose keys are non-existent message ids are
37707 removed. The &'exim_tidydb'& utility outputs comments on the standard output
37708 whenever it removes information from the database.
37709
37710 Certain records are automatically removed by Exim when they are no longer
37711 needed, but others are not. For example, if all the MX hosts for a domain are
37712 down, a retry record is created for each one. If the primary MX host comes back
37713 first, its record is removed when Exim successfully delivers to it, but the
37714 records for the others remain because Exim has not tried to use those hosts.
37715
37716 It is important, therefore, to run &'exim_tidydb'& periodically on all the
37717 hints databases. You should do this at a quiet time of day, because it requires
37718 a database to be locked (and therefore inaccessible to Exim) while it does its
37719 work. Removing records from a DBM file does not normally make the file smaller,
37720 but all the common DBM libraries are able to re-use the space that is released.
37721 After an initial phase of increasing in size, the databases normally reach a
37722 point at which they no longer get any bigger, as long as they are regularly
37723 tidied.
37724
37725 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
37726 databases is likely to keep on increasing.
37727
37728
37729
37730
37731 .section "exim_fixdb" "SECID263"
37732 .cindex "&'exim_fixdb'&"
37733 The &'exim_fixdb'& program is a utility for interactively modifying databases.
37734 Its main use is for testing Exim, but it might also be occasionally useful for
37735 getting round problems in a live system. It has no options, and its interface
37736 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
37737 key of a database record can then be entered, and the data for that record is
37738 displayed.
37739
37740 If &"d"& is typed at the next prompt, the entire record is deleted. For all
37741 except the &'retry'& database, that is the only operation that can be carried
37742 out. For the &'retry'& database, each field is output preceded by a number, and
37743 data for individual fields can be changed by typing the field number followed
37744 by new data, for example:
37745 .code
37746 > 4 951102:1000
37747 .endd
37748 resets the time of the next delivery attempt. Time values are given as a
37749 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
37750 used as optional separators.
37751
37752
37753
37754
37755 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
37756 .cindex "mailbox" "maintenance"
37757 .cindex "&'exim_lock'&"
37758 .cindex "locking mailboxes"
37759 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
37760 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
37761 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
37762 a user agent while investigating a problem. The utility requires the name of
37763 the file as its first argument. If the locking is successful, the second
37764 argument is run as a command (using C's &[system()]& function); if there is no
37765 second argument, the value of the SHELL environment variable is used; if this
37766 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
37767 is unlocked and the utility ends. The following options are available:
37768
37769 .vlist
37770 .vitem &%-fcntl%&
37771 Use &[fcntl()]& locking on the open mailbox.
37772
37773 .vitem &%-flock%&
37774 Use &[flock()]& locking on the open mailbox, provided the operating system
37775 supports it.
37776
37777 .vitem &%-interval%&
37778 This must be followed by a number, which is a number of seconds; it sets the
37779 interval to sleep between retries (default 3).
37780
37781 .vitem &%-lockfile%&
37782 Create a lock file before opening the mailbox.
37783
37784 .vitem &%-mbx%&
37785 Lock the mailbox using MBX rules.
37786
37787 .vitem &%-q%&
37788 Suppress verification output.
37789
37790 .vitem &%-retries%&
37791 This must be followed by a number; it sets the number of times to try to get
37792 the lock (default 10).
37793
37794 .vitem &%-restore_time%&
37795 This option causes &%exim_lock%& to restore the modified and read times to the
37796 locked file before exiting. This allows you to access a locked mailbox (for
37797 example, to take a backup copy) without disturbing the times that the user
37798 subsequently sees.
37799
37800 .vitem &%-timeout%&
37801 This must be followed by a number, which is a number of seconds; it sets a
37802 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
37803 default), a non-blocking call is used.
37804
37805 .vitem &%-v%&
37806 Generate verbose output.
37807 .endlist
37808
37809 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
37810 default is to create a lock file and also to use &[fcntl()]& locking on the
37811 mailbox, which is the same as Exim's default. The use of &%-flock%& or
37812 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
37813 requires that the directory containing the file be writeable. Locking by lock
37814 file does not last for ever; Exim assumes that a lock file is expired if it is
37815 more than 30 minutes old.
37816
37817 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
37818 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
37819 to be taken out on the open mailbox, and an exclusive lock on the file
37820 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
37821 number of the mailbox file. When the locking is released, if an exclusive lock
37822 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
37823
37824 The default output contains verification of the locking that takes place. The
37825 &%-v%& option causes some additional information to be given. The &%-q%& option
37826 suppresses all output except error messages.
37827
37828 A command such as
37829 .code
37830 exim_lock /var/spool/mail/spqr
37831 .endd
37832 runs an interactive shell while the file is locked, whereas
37833 .display
37834 &`exim_lock -q /var/spool/mail/spqr <<End`&
37835 <&'some commands'&>
37836 &`End`&
37837 .endd
37838 runs a specific non-interactive sequence of commands while the file is locked,
37839 suppressing all verification output. A single command can be run by a command
37840 such as
37841 .code
37842 exim_lock -q /var/spool/mail/spqr \
37843 "cp /var/spool/mail/spqr /some/where"
37844 .endd
37845 Note that if a command is supplied, it must be entirely contained within the
37846 second argument &-- hence the quotes.
37847 .ecindex IIDutils
37848
37849
37850 . ////////////////////////////////////////////////////////////////////////////
37851 . ////////////////////////////////////////////////////////////////////////////
37852
37853 .chapter "The Exim monitor" "CHAPeximon"
37854 .scindex IIDeximon "Exim monitor" "description"
37855 .cindex "X-windows"
37856 .cindex "&'eximon'&"
37857 .cindex "Local/eximon.conf"
37858 .cindex "&_exim_monitor/EDITME_&"
37859 The Exim monitor is an application which displays in an X window information
37860 about the state of Exim's queue and what Exim is doing. An admin user can
37861 perform certain operations on messages from this GUI interface; however all
37862 such facilities are also available from the command line, and indeed, the
37863 monitor itself makes use of the command line to perform any actions requested.
37864
37865
37866
37867 .section "Running the monitor" "SECID264"
37868 The monitor is started by running the script called &'eximon'&. This is a shell
37869 script that sets up a number of environment variables, and then runs the
37870 binary called &_eximon.bin_&. The default appearance of the monitor window can
37871 be changed by editing the &_Local/eximon.conf_& file created by editing
37872 &_exim_monitor/EDITME_&. Comments in that file describe what the various
37873 parameters are for.
37874
37875 The parameters that get built into the &'eximon'& script can be overridden for
37876 a particular invocation by setting up environment variables of the same names,
37877 preceded by &`EXIMON_`&. For example, a shell command such as
37878 .code
37879 EXIMON_LOG_DEPTH=400 eximon
37880 .endd
37881 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
37882 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
37883 overrides the Exim log file configuration. This makes it possible to have
37884 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
37885 syslog messages are routed to a file on the local host.
37886
37887 X resources can be used to change the appearance of the window in the normal
37888 way. For example, a resource setting of the form
37889 .code
37890 Eximon*background: gray94
37891 .endd
37892 changes the colour of the background to light grey rather than white. The
37893 stripcharts are drawn with both the data lines and the reference lines in
37894 black. This means that the reference lines are not visible when on top of the
37895 data. However, their colour can be changed by setting a resource called
37896 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
37897 For example, if your X server is running Unix, you could set up lighter
37898 reference lines in the stripcharts by obeying
37899 .code
37900 xrdb -merge <<End
37901 Eximon*highlight: gray
37902 End
37903 .endd
37904 .cindex "admin user"
37905 In order to see the contents of messages on the queue, and to operate on them,
37906 &'eximon'& must either be run as root or by an admin user.
37907
37908 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
37909 contain X11 resource parameters interpreted by the X11 library. In addition,
37910 if the first parameter starts with the string "gdb" then it is removed and the
37911 binary is invoked under gdb (the parameter is used as the gdb command-name, so
37912 versioned variants of gdb can be invoked).
37913
37914 The monitor's window is divided into three parts. The first contains one or
37915 more stripcharts and two action buttons, the second contains a &"tail"& of the
37916 main log file, and the third is a display of the queue of messages awaiting
37917 delivery, with two more action buttons. The following sections describe these
37918 different parts of the display.
37919
37920
37921
37922
37923 .section "The stripcharts" "SECID265"
37924 .cindex "stripchart"
37925 The first stripchart is always a count of messages on the queue. Its name can
37926 be configured by setting QUEUE_STRIPCHART_NAME in the
37927 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
37928 configuration script by regular expression matches on log file entries, making
37929 it possible to display, for example, counts of messages delivered to certain
37930 hosts or using certain transports. The supplied defaults display counts of
37931 received and delivered messages, and of local and SMTP deliveries. The default
37932 period between stripchart updates is one minute; this can be adjusted by a
37933 parameter in the &_Local/eximon.conf_& file.
37934
37935 The stripchart displays rescale themselves automatically as the value they are
37936 displaying changes. There are always 10 horizontal lines in each chart; the
37937 title string indicates the value of each division when it is greater than one.
37938 For example, &"x2"& means that each division represents a value of 2.
37939
37940 It is also possible to have a stripchart which shows the percentage fullness of
37941 a particular disk partition, which is useful when local deliveries are confined
37942 to a single partition.
37943
37944 .cindex "&%statvfs%& function"
37945 This relies on the availability of the &[statvfs()]& function or equivalent in
37946 the operating system. Most, but not all versions of Unix that support Exim have
37947 this. For this particular stripchart, the top of the chart always represents
37948 100%, and the scale is given as &"x10%"&. This chart is configured by setting
37949 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
37950 &_Local/eximon.conf_& file.
37951
37952
37953
37954
37955 .section "Main action buttons" "SECID266"
37956 .cindex "size" "of monitor window"
37957 .cindex "Exim monitor" "window size"
37958 .cindex "window size"
37959 Below the stripcharts there is an action button for quitting the monitor. Next
37960 to this is another button marked &"Size"&. They are placed here so that
37961 shrinking the window to its default minimum size leaves just the queue count
37962 stripchart and these two buttons visible. Pressing the &"Size"& button causes
37963 the window to expand to its maximum size, unless it is already at the maximum,
37964 in which case it is reduced to its minimum.
37965
37966 When expanding to the maximum, if the window cannot be fully seen where it
37967 currently is, it is moved back to where it was the last time it was at full
37968 size. When it is expanding from its minimum size, the old position is
37969 remembered, and next time it is reduced to the minimum it is moved back there.
37970
37971 The idea is that you can keep a reduced window just showing one or two
37972 stripcharts at a convenient place on your screen, easily expand it to show
37973 the full window when required, and just as easily put it back to what it was.
37974 The idea is copied from what the &'twm'& window manager does for its
37975 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
37976 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
37977
37978 Normally, the monitor starts up with the window at its full size, but it can be
37979 built so that it starts up with the window at its smallest size, by setting
37980 START_SMALL=yes in &_Local/eximon.conf_&.
37981
37982
37983
37984 .section "The log display" "SECID267"
37985 .cindex "log" "tail of; in monitor"
37986 The second section of the window is an area in which a display of the tail of
37987 the main log is maintained.
37988 To save space on the screen, the timestamp on each log line is shortened by
37989 removing the date and, if &%log_timezone%& is set, the timezone.
37990 The log tail is not available when the only destination for logging data is
37991 syslog, unless the syslog lines are routed to a local file whose name is passed
37992 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
37993
37994 The log sub-window has a scroll bar at its lefthand side which can be used to
37995 move back to look at earlier text, and the up and down arrow keys also have a
37996 scrolling effect. The amount of log that is kept depends on the setting of
37997 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
37998 to use. When this is full, the earlier 50% of data is discarded &-- this is
37999 much more efficient than throwing it away line by line. The sub-window also has
38000 a horizontal scroll bar for accessing the ends of long log lines. This is the
38001 only means of horizontal scrolling; the right and left arrow keys are not
38002 available. Text can be cut from this part of the window using the mouse in the
38003 normal way. The size of this subwindow is controlled by parameters in the
38004 configuration file &_Local/eximon.conf_&.
38005
38006 Searches of the text in the log window can be carried out by means of the ^R
38007 and ^S keystrokes, which default to a reverse and a forward search,
38008 respectively. The search covers only the text that is displayed in the window.
38009 It cannot go further back up the log.
38010
38011 The point from which the search starts is indicated by a caret marker. This is
38012 normally at the end of the text in the window, but can be positioned explicitly
38013 by pointing and clicking with the left mouse button, and is moved automatically
38014 by a successful search. If new text arrives in the window when it is scrolled
38015 back, the caret remains where it is, but if the window is not scrolled back,
38016 the caret is moved to the end of the new text.
38017
38018 Pressing ^R or ^S pops up a window into which the search text can be typed.
38019 There are buttons for selecting forward or reverse searching, for carrying out
38020 the search, and for cancelling. If the &"Search"& button is pressed, the search
38021 happens and the window remains so that further searches can be done. If the
38022 &"Return"& key is pressed, a single search is done and the window is closed. If
38023 ^C is typed the search is cancelled.
38024
38025 The searching facility is implemented using the facilities of the Athena text
38026 widget. By default this pops up a window containing both &"search"& and
38027 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
38028 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
38029 However, the linkers in BSDI and HP-UX seem unable to handle an externally
38030 provided version of &%TextPop%& when the remaining parts of the text widget
38031 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
38032 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
38033 on these systems, at the expense of having unwanted items in the search popup
38034 window.
38035
38036
38037
38038 .section "The queue display" "SECID268"
38039 .cindex "queue" "display in monitor"
38040 The bottom section of the monitor window contains a list of all messages that
38041 are on the queue, which includes those currently being received or delivered,
38042 as well as those awaiting delivery. The size of this subwindow is controlled by
38043 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
38044 at which it is updated is controlled by another parameter in the same file &--
38045 the default is 5 minutes, since queue scans can be quite expensive. However,
38046 there is an &"Update"& action button just above the display which can be used
38047 to force an update of the queue display at any time.
38048
38049 When a host is down for some time, a lot of pending mail can build up for it,
38050 and this can make it hard to deal with other messages on the queue. To help
38051 with this situation there is a button next to &"Update"& called &"Hide"&. If
38052 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
38053 type anything in here and press &"Return"&, the text is added to a chain of
38054 such texts, and if every undelivered address in a message matches at least one
38055 of the texts, the message is not displayed.
38056
38057 If there is an address that does not match any of the texts, all the addresses
38058 are displayed as normal. The matching happens on the ends of addresses so, for
38059 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
38060 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
38061 has been set up, a button called &"Unhide"& is displayed. If pressed, it
38062 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
38063 a hide request is automatically cancelled after one hour.
38064
38065 While the dialogue box is displayed, you can't press any buttons or do anything
38066 else to the monitor window. For this reason, if you want to cut text from the
38067 queue display to use in the dialogue box, you have to do the cutting before
38068 pressing the &"Hide"& button.
38069
38070 The queue display contains, for each unhidden queued message, the length of
38071 time it has been on the queue, the size of the message, the message id, the
38072 message sender, and the first undelivered recipient, all on one line. If it is
38073 a bounce message, the sender is shown as &"<>"&. If there is more than one
38074 recipient to which the message has not yet been delivered, subsequent ones are
38075 listed on additional lines, up to a maximum configured number, following which
38076 an ellipsis is displayed. Recipients that have already received the message are
38077 not shown.
38078
38079 .cindex "frozen messages" "display"
38080 If a message is frozen, an asterisk is displayed at the left-hand side.
38081
38082 The queue display has a vertical scroll bar, and can also be scrolled by means
38083 of the arrow keys. Text can be cut from it using the mouse in the normal way.
38084 The text searching facilities, as described above for the log window, are also
38085 available, but the caret is always moved to the end of the text when the queue
38086 display is updated.
38087
38088
38089
38090 .section "The queue menu" "SECID269"
38091 .cindex "queue" "menu in monitor"
38092 If the &%shift%& key is held down and the left button is clicked when the mouse
38093 pointer is over the text for any message, an action menu pops up, and the first
38094 line of the queue display for the message is highlighted. This does not affect
38095 any selected text.
38096
38097 If you want to use some other event for popping up the menu, you can set the
38098 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
38099 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
38100 value set in this parameter is a standard X event description. For example, to
38101 run eximon using &%ctrl%& rather than &%shift%& you could use
38102 .code
38103 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
38104 .endd
38105 The title of the menu is the message id, and it contains entries which act as
38106 follows:
38107
38108 .ilist
38109 &'message log'&: The contents of the message log for the message are displayed
38110 in a new text window.
38111 .next
38112 &'headers'&: Information from the spool file that contains the envelope
38113 information and headers is displayed in a new text window. See chapter
38114 &<<CHAPspool>>& for a description of the format of spool files.
38115 .next
38116 &'body'&: The contents of the spool file containing the body of the message are
38117 displayed in a new text window. There is a default limit of 20,000 bytes to the
38118 amount of data displayed. This can be changed by setting the BODY_MAX
38119 option at compile time, or the EXIMON_BODY_MAX option at run time.
38120 .next
38121 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
38122 delivery of the message. This causes an automatic thaw if the message is
38123 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
38124 a new text window. The delivery is run in a separate process, to avoid holding
38125 up the monitor while the delivery proceeds.
38126 .next
38127 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
38128 that the message be frozen.
38129 .next
38130 .cindex "thawing messages"
38131 .cindex "unfreezing messages"
38132 .cindex "frozen messages" "thawing"
38133 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
38134 that the message be thawed.
38135 .next
38136 .cindex "delivery" "forcing failure"
38137 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
38138 that Exim gives up trying to deliver the message. A bounce message is generated
38139 for any remaining undelivered addresses.
38140 .next
38141 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
38142 that the message be deleted from the system without generating a bounce
38143 message.
38144 .next
38145 &'add recipient'&: A dialog box is displayed into which a recipient address can
38146 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
38147 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
38148 Otherwise it must be entered as a fully qualified address. Pressing RETURN
38149 causes a call to Exim to be made using the &%-Mar%& option to request that an
38150 additional recipient be added to the message, unless the entry box is empty, in
38151 which case no action is taken.
38152 .next
38153 &'mark delivered'&: A dialog box is displayed into which a recipient address
38154 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
38155 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
38156 Otherwise it must be entered as a fully qualified address. Pressing RETURN
38157 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
38158 recipient address as already delivered, unless the entry box is empty, in which
38159 case no action is taken.
38160 .next
38161 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
38162 mark all recipient addresses as already delivered.
38163 .next
38164 &'edit sender'&: A dialog box is displayed initialized with the current
38165 sender's address. Pressing RETURN causes a call to Exim to be made using the
38166 &%-Mes%& option to replace the sender address, unless the entry box is empty,
38167 in which case no action is taken. If you want to set an empty sender (as in
38168 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
38169 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
38170 the address is qualified with that domain.
38171 .endlist
38172
38173 When a delivery is forced, a window showing the &%-v%& output is displayed. In
38174 other cases when a call to Exim is made, if there is any output from Exim (in
38175 particular, if the command fails) a window containing the command and the
38176 output is displayed. Otherwise, the results of the action are normally apparent
38177 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
38178 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
38179 if no output is generated.
38180
38181 The queue display is automatically updated for actions such as freezing and
38182 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
38183 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
38184 force an update of the display after one of these actions.
38185
38186 In any text window that is displayed as result of a menu action, the normal
38187 cut-and-paste facility is available, and searching can be carried out using ^R
38188 and ^S, as described above for the log tail window.
38189 .ecindex IIDeximon
38190
38191
38192
38193
38194
38195 . ////////////////////////////////////////////////////////////////////////////
38196 . ////////////////////////////////////////////////////////////////////////////
38197
38198 .chapter "Security considerations" "CHAPsecurity"
38199 .scindex IIDsecurcon "security" "discussion of"
38200 This chapter discusses a number of issues concerned with security, some of
38201 which are also covered in other parts of this manual.
38202
38203 For reasons that this author does not understand, some people have promoted
38204 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
38205 existence of this chapter in the documentation. However, the intent of the
38206 chapter is simply to describe the way Exim works in relation to certain
38207 security concerns, not to make any specific claims about the effectiveness of
38208 its security as compared with other MTAs.
38209
38210 What follows is a description of the way Exim is supposed to be. Best efforts
38211 have been made to try to ensure that the code agrees with the theory, but an
38212 absence of bugs can never be guaranteed. Any that are reported will get fixed
38213 as soon as possible.
38214
38215
38216 .section "Building a more &""hardened""& Exim" "SECID286"
38217 .cindex "security" "build-time features"
38218 There are a number of build-time options that can be set in &_Local/Makefile_&
38219 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
38220 Exim administrator who does not have the root password, or by someone who has
38221 penetrated the Exim (but not the root) account. These options are as follows:
38222
38223 .ilist
38224 ALT_CONFIG_PREFIX can be set to a string that is required to match the
38225 start of any file names used with the &%-C%& option. When it is set, these file
38226 names are also not allowed to contain the sequence &"/../"&. (However, if the
38227 value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
38228 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
38229 default setting for &%ALT_CONFIG_PREFIX%&.
38230
38231 If the permitted configuration files are confined to a directory to
38232 which only root has access, this guards against someone who has broken
38233 into the Exim account from running a privileged Exim with an arbitrary
38234 configuration file, and using it to break into other accounts.
38235 .next
38236
38237 If a non-trusted configuration file (i.e. not the default configuration file
38238 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
38239 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
38240 the next item), then root privilege is retained only if the caller of Exim is
38241 root. This locks out the possibility of testing a configuration using &%-C%&
38242 right through message reception and delivery, even if the caller is root. The
38243 reception works, but by that time, Exim is running as the Exim user, so when
38244 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
38245 privilege to be lost. However, root can test reception and delivery using two
38246 separate commands.
38247
38248 .next
38249 The WHITELIST_D_MACROS build option declares some macros to be safe to override
38250 with &%-D%& if the real uid is one of root, the Exim run-time user or the
38251 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
38252 requiring the run-time value supplied to &%-D%& to match a regex that errs on
38253 the restrictive side. Requiring build-time selection of safe macros is onerous
38254 but this option is intended solely as a transition mechanism to permit
38255 previously-working configurations to continue to work after release 4.73.
38256 .next
38257 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
38258 is disabled.
38259 .next
38260 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
38261 never to be used for any deliveries. This is like the &%never_users%& runtime
38262 option, but it cannot be overridden; the runtime option adds additional users
38263 to the list. The default setting is &"root"&; this prevents a non-root user who
38264 is permitted to modify the runtime file from using Exim as a way to get root.
38265 .endlist
38266
38267
38268
38269 .section "Root privilege" "SECID270"
38270 .cindex "setuid"
38271 .cindex "root privilege"
38272 The Exim binary is normally setuid to root, which means that it gains root
38273 privilege (runs as root) when it starts execution. In some special cases (for
38274 example, when the daemon is not in use and there are no local deliveries), it
38275 may be possible to run Exim setuid to some user other than root. This is
38276 discussed in the next section. However, in most installations, root privilege
38277 is required for two things:
38278
38279 .ilist
38280 To set up a socket connected to the standard SMTP port (25) when initialising
38281 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
38282 not required.
38283 .next
38284 To be able to change uid and gid in order to read users' &_.forward_& files and
38285 perform local deliveries as the receiving user or as specified in the
38286 configuration.
38287 .endlist
38288
38289 It is not necessary to be root to do any of the other things Exim does, such as
38290 receiving messages and delivering them externally over SMTP, and it is
38291 obviously more secure if Exim does not run as root except when necessary.
38292 For this reason, a user and group for Exim to use must be defined in
38293 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
38294 group"&. Their values can be changed by the run time configuration, though this
38295 is not recommended. Often a user called &'exim'& is used, but some sites use
38296 &'mail'& or another user name altogether.
38297
38298 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
38299 abdication; the process cannot regain root afterwards. Prior to release 4.00,
38300 &[seteuid()]& was used in some circumstances, but this is no longer the case.
38301
38302 After a new Exim process has interpreted its command line options, it changes
38303 uid and gid in the following cases:
38304
38305 .ilist
38306 .oindex "&%-C%&"
38307 .oindex "&%-D%&"
38308 If the &%-C%& option is used to specify an alternate configuration file, or if
38309 the &%-D%& option is used to define macro values for the configuration, and the
38310 calling process is not running as root, the uid and gid are changed to those of
38311 the calling process.
38312 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
38313 option may not be used at all.
38314 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
38315 can be supplied if the calling process is running as root, the Exim run-time
38316 user or CONFIGURE_OWNER, if defined.
38317 .next
38318 .oindex "&%-be%&"
38319 .oindex "&%-bf%&"
38320 .oindex "&%-bF%&"
38321 If the expansion test option (&%-be%&) or one of the filter testing options
38322 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
38323 calling process.
38324 .next
38325 If the process is not a daemon process or a queue runner process or a delivery
38326 process or a process for testing address routing (started with &%-bt%&), the
38327 uid and gid are changed to the Exim user and group. This means that Exim always
38328 runs under its own uid and gid when receiving messages. This also applies when
38329 testing address verification
38330 .oindex "&%-bv%&"
38331 .oindex "&%-bh%&"
38332 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
38333 option).
38334 .next
38335 For a daemon, queue runner, delivery, or address testing process, the uid
38336 remains as root at this stage, but the gid is changed to the Exim group.
38337 .endlist
38338
38339 The processes that initially retain root privilege behave as follows:
38340
38341 .ilist
38342 A daemon process changes the gid to the Exim group and the uid to the Exim
38343 user after setting up one or more listening sockets. The &[initgroups()]&
38344 function is called, so that if the Exim user is in any additional groups, they
38345 will be used during message reception.
38346 .next
38347 A queue runner process retains root privilege throughout its execution. Its
38348 job is to fork a controlled sequence of delivery processes.
38349 .next
38350 A delivery process retains root privilege throughout most of its execution,
38351 but any actual deliveries (that is, the transports themselves) are run in
38352 subprocesses which always change to a non-root uid and gid. For local
38353 deliveries this is typically the uid and gid of the owner of the mailbox; for
38354 remote deliveries, the Exim uid and gid are used. Once all the delivery
38355 subprocesses have been run, a delivery process changes to the Exim uid and gid
38356 while doing post-delivery tidying up such as updating the retry database and
38357 generating bounce and warning messages.
38358
38359 While the recipient addresses in a message are being routed, the delivery
38360 process runs as root. However, if a user's filter file has to be processed,
38361 this is done in a subprocess that runs under the individual user's uid and
38362 gid. A system filter is run as root unless &%system_filter_user%& is set.
38363 .next
38364 A process that is testing addresses (the &%-bt%& option) runs as root so that
38365 the routing is done in the same environment as a message delivery.
38366 .endlist
38367
38368
38369
38370
38371 .section "Running Exim without privilege" "SECTrunexiwitpri"
38372 .cindex "privilege, running without"
38373 .cindex "unprivileged running"
38374 .cindex "root privilege" "running without"
38375 Some installations like to run Exim in an unprivileged state for more of its
38376 operation, for added security. Support for this mode of operation is provided
38377 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
38378 gid are changed to the Exim user and group at the start of a delivery process
38379 (and also queue runner and address testing processes). This means that address
38380 routing is no longer run as root, and the deliveries themselves cannot change
38381 to any other uid.
38382
38383 .cindex SIGHUP
38384 .cindex "daemon" "restarting"
38385 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
38386 that the daemon can still be started in the usual way, and it can respond
38387 correctly to SIGHUP because the re-invocation regains root privilege.
38388
38389 An alternative approach is to make Exim setuid to the Exim user and also setgid
38390 to the Exim group. If you do this, the daemon must be started from a root
38391 process. (Calling Exim from a root process makes it behave in the way it does
38392 when it is setuid root.) However, the daemon cannot restart itself after a
38393 SIGHUP signal because it cannot regain privilege.
38394
38395 It is still useful to set &%deliver_drop_privilege%& in this case, because it
38396 stops Exim from trying to re-invoke itself to do a delivery after a message has
38397 been received. Such a re-invocation is a waste of resources because it has no
38398 effect.
38399
38400 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
38401 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
38402 to the Exim user seems a clean approach, but there is one complication:
38403
38404 In this style of operation, Exim is running with the real uid and gid set to
38405 those of the calling process, and the effective uid/gid set to Exim's values.
38406 Ideally, any association with the calling process' uid/gid should be dropped,
38407 that is, the real uid/gid should be reset to the effective values so as to
38408 discard any privileges that the caller may have. While some operating systems
38409 have a function that permits this action for a non-root effective uid, quite a
38410 number of them do not. Because of this lack of standardization, Exim does not
38411 address this problem at this time.
38412
38413 For this reason, the recommended approach for &"mostly unprivileged"& running
38414 is to keep the Exim binary setuid to root, and to set
38415 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
38416 be used in the most straightforward way.
38417
38418 If you configure Exim not to run delivery processes as root, there are a
38419 number of restrictions on what you can do:
38420
38421 .ilist
38422 You can deliver only as the Exim user/group. You should explicitly use the
38423 &%user%& and &%group%& options to override routers or local transports that
38424 normally deliver as the recipient. This makes sure that configurations that
38425 work in this mode function the same way in normal mode. Any implicit or
38426 explicit specification of another user causes an error.
38427 .next
38428 Use of &_.forward_& files is severely restricted, such that it is usually
38429 not worthwhile to include them in the configuration.
38430 .next
38431 Users who wish to use &_.forward_& would have to make their home directory and
38432 the file itself accessible to the Exim user. Pipe and append-to-file entries,
38433 and their equivalents in Exim filters, cannot be used. While they could be
38434 enabled in the Exim user's name, that would be insecure and not very useful.
38435 .next
38436 Unless the local user mailboxes are all owned by the Exim user (possible in
38437 some POP3 or IMAP-only environments):
38438
38439 .olist
38440 They must be owned by the Exim group and be writeable by that group. This
38441 implies you must set &%mode%& in the appendfile configuration, as well as the
38442 mode of the mailbox files themselves.
38443 .next
38444 You must set &%no_check_owner%&, since most or all of the files will not be
38445 owned by the Exim user.
38446 .next
38447 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
38448 on a newly created mailbox when unprivileged. This also implies that new
38449 mailboxes need to be created manually.
38450 .endlist olist
38451 .endlist ilist
38452
38453
38454 These restrictions severely restrict what can be done in local deliveries.
38455 However, there are no restrictions on remote deliveries. If you are running a
38456 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
38457 gives more security at essentially no cost.
38458
38459 If you are using the &%mua_wrapper%& facility (see chapter
38460 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
38461
38462
38463
38464
38465 .section "Delivering to local files" "SECID271"
38466 Full details of the checks applied by &(appendfile)& before it writes to a file
38467 are given in chapter &<<CHAPappendfile>>&.
38468
38469
38470
38471 .section "Running local commands" "SECTsecconslocalcmds"
38472 .cindex "security" "local commands"
38473 .cindex "security" "command injection attacks"
38474 There are a number of ways in which an administrator can configure Exim to run
38475 commands based upon received, untrustworthy, data. Further, in some
38476 configurations a user who can control a &_.forward_& file can also arrange to
38477 run commands. Configuration to check includes, but is not limited to:
38478
38479 .ilist
38480 Use of &%use_shell%& in the pipe transport: various forms of shell command
38481 injection may be possible with this option present. It is dangerous and should
38482 be used only with considerable caution. Consider constraints which whitelist
38483 allowed characters in a variable which is to be used in a pipe transport that
38484 has &%use_shell%& enabled.
38485 .next
38486 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
38487 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
38488 &_.forward_& files in a redirect router. If Exim is running on a central mail
38489 hub to which ordinary users do not have shell access, but home directories are
38490 NFS mounted (for instance) then administrators should review the list of these
38491 forbid options available, and should bear in mind that the options that may
38492 need forbidding can change as new features are added between releases.
38493 .next
38494 The &%${run...}%& expansion item does not use a shell by default, but
38495 administrators can configure use of &_/bin/sh_& as part of the command.
38496 Such invocations should be viewed with prejudicial suspicion.
38497 .next
38498 Administrators who use embedded Perl are advised to explore how Perl's
38499 taint checking might apply to their usage.
38500 .next
38501 Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
38502 administrators are well advised to view its use with suspicion, in case (for
38503 instance) it allows a local-part to contain embedded Exim directives.
38504 .next
38505 Use of &%${match_local_part...}%& and friends becomes more dangerous if
38506 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
38507 each can reference arbitrary lists and files, rather than just being a list
38508 of opaque strings.
38509 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
38510 real-world security vulnerabilities caused by its use with untrustworthy data
38511 injected in, for SQL injection attacks.
38512 Consider the use of the &%inlisti%& expansion condition instead.
38513 .endlist
38514
38515
38516
38517
38518 .section "Trust in configuration data" "SECTsecconfdata"
38519 .cindex "security" "data sources"
38520 .cindex "security" "regular expressions"
38521 .cindex "regular expressions" "security"
38522 .cindex "PCRE" "security"
38523 If configuration data for Exim can come from untrustworthy sources, there
38524 are some issues to be aware of:
38525
38526 .ilist
38527 Use of &%${expand...}%& may provide a path for shell injection attacks.
38528 .next
38529 Letting untrusted data provide a regular expression is unwise.
38530 .next
38531 Using &%${match...}%& to apply a fixed regular expression against untrusted
38532 data may result in pathological behaviour within PCRE. Be aware of what
38533 "backtracking" means and consider options for being more strict with a regular
38534 expression. Avenues to explore include limiting what can match (avoiding &`.`&
38535 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
38536 possessive quantifiers or just not using regular expressions against untrusted
38537 data.
38538 .next
38539 It can be important to correctly use &%${quote:...}%&,
38540 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
38541 items to ensure that data is correctly constructed.
38542 .next
38543 Some lookups might return multiple results, even though normal usage is only
38544 expected to yield one result.
38545 .endlist
38546
38547
38548
38549
38550 .section "IPv4 source routing" "SECID272"
38551 .cindex "source routing" "in IP packets"
38552 .cindex "IP source routing"
38553 Many operating systems suppress IP source-routed packets in the kernel, but
38554 some cannot be made to do this, so Exim does its own check. It logs incoming
38555 IPv4 source-routed TCP calls, and then drops them. Things are all different in
38556 IPv6. No special checking is currently done.
38557
38558
38559
38560 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
38561 Support for these SMTP commands is disabled by default. If required, they can
38562 be enabled by defining suitable ACLs.
38563
38564
38565
38566
38567 .section "Privileged users" "SECID274"
38568 .cindex "trusted users"
38569 .cindex "admin user"
38570 .cindex "privileged user"
38571 .cindex "user" "trusted"
38572 .cindex "user" "admin"
38573 Exim recognizes two sets of users with special privileges. Trusted users are
38574 able to submit new messages to Exim locally, but supply their own sender
38575 addresses and information about a sending host. For other users submitting
38576 local messages, Exim sets up the sender address from the uid, and doesn't
38577 permit a remote host to be specified.
38578
38579 .oindex "&%-f%&"
38580 However, an untrusted user is permitted to use the &%-f%& command line option
38581 in the special form &%-f <>%& to indicate that a delivery failure for the
38582 message should not cause an error report. This affects the message's envelope,
38583 but it does not affect the &'Sender:'& header. Untrusted users may also be
38584 permitted to use specific forms of address with the &%-f%& option by setting
38585 the &%untrusted_set_sender%& option.
38586
38587 Trusted users are used to run processes that receive mail messages from some
38588 other mail domain and pass them on to Exim for delivery either locally, or over
38589 the Internet. Exim trusts a caller that is running as root, as the Exim user,
38590 as any user listed in the &%trusted_users%& configuration option, or under any
38591 group listed in the &%trusted_groups%& option.
38592
38593 Admin users are permitted to do things to the messages on Exim's queue. They
38594 can freeze or thaw messages, cause them to be returned to their senders, remove
38595 them entirely, or modify them in various ways. In addition, admin users can run
38596 the Exim monitor and see all the information it is capable of providing, which
38597 includes the contents of files on the spool.
38598
38599 .oindex "&%-M%&"
38600 .oindex "&%-q%&"
38601 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
38602 delivery of messages on its queue is restricted to admin users. This
38603 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
38604 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
38605 queue is also restricted to admin users. This restriction can be relaxed by
38606 setting &%no_queue_list_requires_admin%&.
38607
38608 Exim recognizes an admin user if the calling process is running as root or as
38609 the Exim user or if any of the groups associated with the calling process is
38610 the Exim group. It is not necessary actually to be running under the Exim
38611 group. However, if admin users who are not root or the Exim user are to access
38612 the contents of files on the spool via the Exim monitor (which runs
38613 unprivileged), Exim must be built to allow group read access to its spool
38614 files.
38615
38616 By default, regular users are trusted to perform basic testing and
38617 introspection commands, as themselves. This setting can be tightened by
38618 setting the &%commandline_checks_require_admin%& option.
38619 This affects most of the checking options,
38620 such as &%-be%& and anything else &%-b*%&.
38621
38622
38623 .section "Spool files" "SECID275"
38624 .cindex "spool directory" "files"
38625 Exim's spool directory and everything it contains is owned by the Exim user and
38626 set to the Exim group. The mode for spool files is defined in the
38627 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
38628 any user who is a member of the Exim group can access these files.
38629
38630
38631
38632 .section "Use of argv[0]" "SECID276"
38633 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
38634 of specific strings, Exim assumes certain options. For example, calling Exim
38635 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
38636 to calling it with the option &%-bS%&. There are no security implications in
38637 this.
38638
38639
38640
38641 .section "Use of %f formatting" "SECID277"
38642 The only use made of &"%f"& by Exim is in formatting load average values. These
38643 are actually stored in integer variables as 1000 times the load average.
38644 Consequently, their range is limited and so therefore is the length of the
38645 converted output.
38646
38647
38648
38649 .section "Embedded Exim path" "SECID278"
38650 Exim uses its own path name, which is embedded in the code, only when it needs
38651 to re-exec in order to regain root privilege. Therefore, it is not root when it
38652 does so. If some bug allowed the path to get overwritten, it would lead to an
38653 arbitrary program's being run as exim, not as root.
38654
38655
38656
38657 .section "Dynamic module directory" "SECTdynmoddir"
38658 Any dynamically loadable modules must be installed into the directory
38659 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
38660 loading it.
38661
38662
38663 .section "Use of sprintf()" "SECID279"
38664 .cindex "&[sprintf()]&"
38665 A large number of occurrences of &"sprintf"& in the code are actually calls to
38666 &'string_sprintf()'&, a function that returns the result in malloc'd store.
38667 The intermediate formatting is done into a large fixed buffer by a function
38668 that runs through the format string itself, and checks the length of each
38669 conversion before performing it, thus preventing buffer overruns.
38670
38671 The remaining uses of &[sprintf()]& happen in controlled circumstances where
38672 the output buffer is known to be sufficiently long to contain the converted
38673 string.
38674
38675
38676
38677 .section "Use of debug_printf() and log_write()" "SECID280"
38678 Arbitrary strings are passed to both these functions, but they do their
38679 formatting by calling the function &'string_vformat()'&, which runs through
38680 the format string itself, and checks the length of each conversion.
38681
38682
38683
38684 .section "Use of strcat() and strcpy()" "SECID281"
38685 These are used only in cases where the output buffer is known to be large
38686 enough to hold the result.
38687 .ecindex IIDsecurcon
38688
38689
38690
38691
38692 . ////////////////////////////////////////////////////////////////////////////
38693 . ////////////////////////////////////////////////////////////////////////////
38694
38695 .chapter "Format of spool files" "CHAPspool"
38696 .scindex IIDforspo1 "format" "spool files"
38697 .scindex IIDforspo2 "spool directory" "format of files"
38698 .scindex IIDforspo3 "spool files" "format of"
38699 .cindex "spool files" "editing"
38700 A message on Exim's queue consists of two files, whose names are the message id
38701 followed by -D and -H, respectively. The data portion of the message is kept in
38702 the -D file on its own. The message's envelope, status, and headers are all
38703 kept in the -H file, whose format is described in this chapter. Each of these
38704 two files contains the final component of its own name as its first line. This
38705 is insurance against disk crashes where the directory is lost but the files
38706 themselves are recoverable.
38707
38708 .new
38709 The file formats may be changed, or new formats added, at any release.
38710 Spool files are not intended as an interface to other programs
38711 and should not be used as such.
38712 .wen
38713
38714 Some people are tempted into editing -D files in order to modify messages. You
38715 need to be extremely careful if you do this; it is not recommended and you are
38716 on your own if you do it. Here are some of the pitfalls:
38717
38718 .ilist
38719 You must ensure that Exim does not try to deliver the message while you are
38720 fiddling with it. The safest way is to take out a write lock on the -D file,
38721 which is what Exim itself does, using &[fcntl()]&. If you update the file in
38722 place, the lock will be retained. If you write a new file and rename it, the
38723 lock will be lost at the instant of rename.
38724 .next
38725 .vindex "&$body_linecount$&"
38726 If you change the number of lines in the file, the value of
38727 &$body_linecount$&, which is stored in the -H file, will be incorrect and can
38728 cause incomplete transmission of messages or undeliverable messages.
38729 .next
38730 If the message is in MIME format, you must take care not to break it.
38731 .next
38732 If the message is cryptographically signed, any change will invalidate the
38733 signature.
38734 .endlist
38735 All in all, modifying -D files is fraught with danger.
38736
38737 Files whose names end with -J may also be seen in the &_input_& directory (or
38738 its subdirectories when &%split_spool_directory%& is set). These are journal
38739 files, used to record addresses to which the message has been delivered during
38740 the course of a delivery attempt. If there are still undelivered recipients at
38741 the end, the -H file is updated, and the -J file is deleted. If, however, there
38742 is some kind of crash (for example, a power outage) before this happens, the -J
38743 file remains in existence. When Exim next processes the message, it notices the
38744 -J file and uses it to update the -H file before starting the next delivery
38745 attempt.
38746
38747 Files whose names end with -K or .eml may also be seen in the spool.
38748 These are temporaries used for DKIM or malware processing, when that is used.
38749 They should be tidied up by normal operations; any old ones are probably
38750 relics of crashes and can be removed.
38751
38752 .section "Format of the -H file" "SECID282"
38753 .cindex "uid (user id)" "in spool file"
38754 .cindex "gid (group id)" "in spool file"
38755 The second line of the -H file contains the login name for the uid of the
38756 process that called Exim to read the message, followed by the numerical uid and
38757 gid. For a locally generated message, this is normally the user who sent the
38758 message. For a message received over TCP/IP via the daemon, it is
38759 normally the Exim user.
38760
38761 The third line of the file contains the address of the message's sender as
38762 transmitted in the envelope, contained in angle brackets. The sender address is
38763 empty for bounce messages. For incoming SMTP mail, the sender address is given
38764 in the MAIL command. For locally generated mail, the sender address is
38765 created by Exim from the login name of the current user and the configured
38766 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
38767 leading &"From&~"& line if the caller is trusted, or if the supplied address is
38768 &"<>"& or an address that matches &%untrusted_set_senders%&.
38769
38770 The fourth line contains two numbers. The first is the time that the message
38771 was received, in the conventional Unix form &-- the number of seconds since the
38772 start of the epoch. The second number is a count of the number of messages
38773 warning of delayed delivery that have been sent to the sender.
38774
38775 There follow a number of lines starting with a hyphen. These can appear in any
38776 order, and are omitted when not relevant:
38777
38778 .vlist
38779 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
38780 This item is obsolete, and is not generated from Exim release 4.61 onwards;
38781 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
38782 recognized, to provide backward compatibility. In the old format, a line of
38783 this form is present for every ACL variable that is not empty. The number
38784 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
38785 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
38786 the data string for the variable. The string itself starts at the beginning of
38787 the next line, and is followed by a newline character. It may contain internal
38788 newlines.
38789
38790 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
38791 A line of this form is present for every ACL connection variable that is
38792 defined. Note that there is a space between &%-aclc%& and the rest of the name.
38793 The length is the length of the data string for the variable. The string itself
38794 starts at the beginning of the next line, and is followed by a newline
38795 character. It may contain internal newlines.
38796
38797 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
38798 A line of this form is present for every ACL message variable that is defined.
38799 Note that there is a space between &%-aclm%& and the rest of the name. The
38800 length is the length of the data string for the variable. The string itself
38801 starts at the beginning of the next line, and is followed by a newline
38802 character. It may contain internal newlines.
38803
38804 .vitem "&%-active_hostname%&&~<&'hostname'&>"
38805 This is present if, when the message was received over SMTP, the value of
38806 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
38807
38808 .vitem &%-allow_unqualified_recipient%&
38809 This is present if unqualified recipient addresses are permitted in header
38810 lines (to stop such addresses from being qualified if rewriting occurs at
38811 transport time). Local messages that were input using &%-bnq%& and remote
38812 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
38813
38814 .vitem &%-allow_unqualified_sender%&
38815 This is present if unqualified sender addresses are permitted in header lines
38816 (to stop such addresses from being qualified if rewriting occurs at transport
38817 time). Local messages that were input using &%-bnq%& and remote messages from
38818 hosts that match &%sender_unqualified_hosts%& set this flag.
38819
38820 .vitem "&%-auth_id%&&~<&'text'&>"
38821 The id information for a message received on an authenticated SMTP connection
38822 &-- the value of the &$authenticated_id$& variable.
38823
38824 .vitem "&%-auth_sender%&&~<&'address'&>"
38825 The address of an authenticated sender &-- the value of the
38826 &$authenticated_sender$& variable.
38827
38828 .vitem "&%-body_linecount%&&~<&'number'&>"
38829 This records the number of lines in the body of the message, and is
38830 present unless &%-spool_file_wireformat%& is.
38831
38832 .vitem "&%-body_zerocount%&&~<&'number'&>"
38833 This records the number of binary zero bytes in the body of the message, and is
38834 present if the number is greater than zero.
38835
38836 .vitem &%-deliver_firsttime%&
38837 This is written when a new message is first added to the spool. When the spool
38838 file is updated after a deferral, it is omitted.
38839
38840 .vitem "&%-frozen%&&~<&'time'&>"
38841 .cindex "frozen messages" "spool data"
38842 The message is frozen, and the freezing happened at <&'time'&>.
38843
38844 .vitem "&%-helo_name%&&~<&'text'&>"
38845 This records the host name as specified by a remote host in a HELO or EHLO
38846 command.
38847
38848 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
38849 This records the IP address of the host from which the message was received and
38850 the remote port number that was used. It is omitted for locally generated
38851 messages.
38852
38853 .vitem "&%-host_auth%&&~<&'text'&>"
38854 If the message was received on an authenticated SMTP connection, this records
38855 the name of the authenticator &-- the value of the
38856 &$sender_host_authenticated$& variable.
38857
38858 .vitem &%-host_lookup_failed%&
38859 This is present if an attempt to look up the sending host's name from its IP
38860 address failed. It corresponds to the &$host_lookup_failed$& variable.
38861
38862 .vitem "&%-host_name%&&~<&'text'&>"
38863 .cindex "reverse DNS lookup"
38864 .cindex "DNS" "reverse lookup"
38865 This records the name of the remote host from which the message was received,
38866 if the host name was looked up from the IP address when the message was being
38867 received. It is not present if no reverse lookup was done.
38868
38869 .vitem "&%-ident%&&~<&'text'&>"
38870 For locally submitted messages, this records the login of the originating user,
38871 unless it was a trusted user and the &%-oMt%& option was used to specify an
38872 ident value. For messages received over TCP/IP, this records the ident string
38873 supplied by the remote host, if any.
38874
38875 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
38876 This records the IP address of the local interface and the port number through
38877 which a message was received from a remote host. It is omitted for locally
38878 generated messages.
38879
38880 .vitem &%-local%&
38881 The message is from a local sender.
38882
38883 .vitem &%-localerror%&
38884 The message is a locally-generated bounce message.
38885
38886 .vitem "&%-local_scan%&&~<&'string'&>"
38887 This records the data string that was returned by the &[local_scan()]& function
38888 when the message was received &-- the value of the &$local_scan_data$&
38889 variable. It is omitted if no data was returned.
38890
38891 .vitem &%-manual_thaw%&
38892 The message was frozen but has been thawed manually, that is, by an explicit
38893 Exim command rather than via the auto-thaw process.
38894
38895 .vitem &%-N%&
38896 A testing delivery process was started using the &%-N%& option to suppress any
38897 actual deliveries, but delivery was deferred. At any further delivery attempts,
38898 &%-N%& is assumed.
38899
38900 .vitem &%-received_protocol%&
38901 This records the value of the &$received_protocol$& variable, which contains
38902 the name of the protocol by which the message was received.
38903
38904 .vitem &%-sender_set_untrusted%&
38905 The envelope sender of this message was set by an untrusted local caller (used
38906 to ensure that the caller is displayed in queue listings).
38907
38908 .vitem "&%-spam_score_int%&&~<&'number'&>"
38909 If a message was scanned by SpamAssassin, this is present. It records the value
38910 of &$spam_score_int$&.
38911
38912 .vitem &%-spool_file_wireformat%&
38913 The -D file for this message is in wire-format (for ESMTP CHUNKING)
38914 rather than Unix-format.
38915 The line-ending is CRLF rather than newline.
38916 There is still, however, no leading-dot-stuffing.
38917
38918 .vitem &%-tls_certificate_verified%&
38919 A TLS certificate was received from the client that sent this message, and the
38920 certificate was verified by the server.
38921
38922 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
38923 When the message was received over an encrypted connection, this records the
38924 name of the cipher suite that was used.
38925
38926 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
38927 When the message was received over an encrypted connection, and a certificate
38928 was received from the client, this records the Distinguished Name from that
38929 certificate.
38930 .endlist
38931
38932 Following the options there is a list of those addresses to which the message
38933 is not to be delivered. This set of addresses is initialized from the command
38934 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
38935 is set; otherwise it starts out empty. Whenever a successful delivery is made,
38936 the address is added to this set. The addresses are kept internally as a
38937 balanced binary tree, and it is a representation of that tree which is written
38938 to the spool file. If an address is expanded via an alias or forward file, the
38939 original address is added to the tree when deliveries to all its child
38940 addresses are complete.
38941
38942 If the tree is empty, there is a single line in the spool file containing just
38943 the text &"XX"&. Otherwise, each line consists of two letters, which are either
38944 Y or N, followed by an address. The address is the value for the node of the
38945 tree, and the letters indicate whether the node has a left branch and/or a
38946 right branch attached to it, respectively. If branches exist, they immediately
38947 follow. Here is an example of a three-node tree:
38948 .code
38949 YY darcy@austen.fict.example
38950 NN alice@wonderland.fict.example
38951 NN editor@thesaurus.ref.example
38952 .endd
38953 After the non-recipients tree, there is a list of the message's recipients.
38954 This is a simple list, preceded by a count. It includes all the original
38955 recipients of the message, including those to whom the message has already been
38956 delivered. In the simplest case, the list contains one address per line. For
38957 example:
38958 .code
38959 4
38960 editor@thesaurus.ref.example
38961 darcy@austen.fict.example
38962 rdo@foundation
38963 alice@wonderland.fict.example
38964 .endd
38965 However, when a child address has been added to the top-level addresses as a
38966 result of the use of the &%one_time%& option on a &(redirect)& router, each
38967 line is of the following form:
38968 .display
38969 <&'top-level address'&> <&'errors_to address'&> &&&
38970 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
38971 .endd
38972 The 01 flag bit indicates the presence of the three other fields that follow
38973 the top-level address. Other bits may be used in future to support additional
38974 fields. The <&'parent number'&> is the offset in the recipients list of the
38975 original parent of the &"one time"& address. The first two fields are the
38976 envelope sender that is associated with this address and its length. If the
38977 length is zero, there is no special envelope sender (there are then two space
38978 characters in the line). A non-empty field can arise from a &(redirect)& router
38979 that has an &%errors_to%& setting.
38980
38981
38982 A blank line separates the envelope and status information from the headers
38983 which follow. A header may occupy several lines of the file, and to save effort
38984 when reading it in, each header is preceded by a number and an identifying
38985 character. The number is the number of characters in the header, including any
38986 embedded newlines and the terminating newline. The character is one of the
38987 following:
38988
38989 .table2 50pt
38990 .row <&'blank'&> "header in which Exim has no special interest"
38991 .row &`B`& "&'Bcc:'& header"
38992 .row &`C`& "&'Cc:'& header"
38993 .row &`F`& "&'From:'& header"
38994 .row &`I`& "&'Message-id:'& header"
38995 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
38996 .row &`R`& "&'Reply-To:'& header"
38997 .row &`S`& "&'Sender:'& header"
38998 .row &`T`& "&'To:'& header"
38999 .row &`*`& "replaced or deleted header"
39000 .endtable
39001
39002 Deleted or replaced (rewritten) headers remain in the spool file for debugging
39003 purposes. They are not transmitted when the message is delivered. Here is a
39004 typical set of headers:
39005 .code
39006 111P Received: by hobbit.fict.example with local (Exim 4.00)
39007 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
39008 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
39009 038* X-rewrote-sender: bb@hobbit.fict.example
39010 042* From: Bilbo Baggins <bb@hobbit.fict.example>
39011 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
39012 099* To: alice@wonderland.fict.example, rdo@foundation,
39013 darcy@austen.fict.example, editor@thesaurus.ref.example
39014 104T To: alice@wonderland.fict.example, rdo@foundation.example,
39015 darcy@austen.fict.example, editor@thesaurus.ref.example
39016 038 Date: Fri, 11 May 2001 10:28:59 +0100
39017 .endd
39018 The asterisked headers indicate that the envelope sender, &'From:'& header, and
39019 &'To:'& header have been rewritten, the last one because routing expanded the
39020 unqualified domain &'foundation'&.
39021 .ecindex IIDforspo1
39022 .ecindex IIDforspo2
39023 .ecindex IIDforspo3
39024
39025 .section "Format of the -D file" "SECID282a"
39026 The data file is traditionally in Unix-standard format: lines are ended with
39027 an ASCII newline character.
39028 However, when the &%spool_wireformat%& main option is used some -D files
39029 can have an alternate format.
39030 This is flagged by a &%-spool_file_wireformat%& line in the corresponding -H file.
39031 The -D file lines (not including the first name-component line) are
39032 suitable for direct copying to the wire when transmitting using the
39033 ESMTP CHUNKING option, meaning lower processing overhead.
39034 Lines are terminated with an ASCII CRLF pair.
39035 There is no dot-stuffing (and no dot-termination).
39036
39037 . ////////////////////////////////////////////////////////////////////////////
39038 . ////////////////////////////////////////////////////////////////////////////
39039
39040 .chapter "DKIM and SPF" "CHAPdkim" &&&
39041 "DKIM and SPF Support"
39042 .cindex "DKIM"
39043
39044 .section "DKIM (DomainKeys Identified Mail)" SECDKIM
39045
39046 DKIM is a mechanism by which messages sent by some entity can be provably
39047 linked to a domain which that entity controls. It permits reputation to
39048 be tracked on a per-domain basis, rather than merely upon source IP address.
39049 DKIM is documented in RFC 6376.
39050
39051 As DKIM relies on the message being unchanged in transit, messages handled
39052 by a mailing-list (which traditionally adds to the message) will not match
39053 any original DKIM signature.
39054
39055 DKIM support is compiled into Exim by default if TLS support is present.
39056 It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
39057
39058 Exim's DKIM implementation allows for
39059 .olist
39060 Signing outgoing messages: This function is implemented in the SMTP transport.
39061 It can co-exist with all other Exim features
39062 (including transport filters)
39063 except cutthrough delivery.
39064 .next
39065 Verifying signatures in incoming messages: This is implemented by an additional
39066 ACL (acl_smtp_dkim), which can be called several times per message, with
39067 different signature contexts.
39068 .endlist
39069
39070 In typical Exim style, the verification implementation does not include any
39071 default "policy". Instead it enables you to build your own policy using
39072 Exim's standard controls.
39073
39074 Please note that verification of DKIM signatures in incoming mail is turned
39075 on by default for logging (in the <= line) purposes.
39076
39077 Additional log detail can be enabled using the &%dkim_verbose%& log_selector.
39078 When set, for each signature in incoming email,
39079 exim will log a line displaying the most important signature details, and the
39080 signature status. Here is an example (with line-breaks added for clarity):
39081 .code
39082 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
39083 d=facebookmail.com s=q1-2009b
39084 c=relaxed/relaxed a=rsa-sha1
39085 i=@facebookmail.com t=1252484542 [verification succeeded]
39086 .endd
39087
39088 You might want to turn off DKIM verification processing entirely for internal
39089 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
39090 control modifier. This should typically be done in the RCPT ACL, at points
39091 where you accept mail from relay sources (internal hosts or authenticated
39092 senders).
39093
39094
39095 .section "Signing outgoing messages" "SECDKIMSIGN"
39096 .cindex "DKIM" "signing"
39097
39098 For signing to be usable you must have published a DKIM record in DNS.
39099 Note that RFC 8301 says:
39100 .code
39101 rsa-sha1 MUST NOT be used for signing or verifying.
39102
39103 Signers MUST use RSA keys of at least 1024 bits for all keys.
39104 Signers SHOULD use RSA keys of at least 2048 bits.
39105 .endd
39106
39107 Note also that the key content (the 'p=' field)
39108 in the DNS record is different between RSA and EC keys;
39109 for the former it is the base64 of the ASN.1 for the RSA public key
39110 (equivalent to the private-key .pem with the header/trailer stripped)
39111 but for EC keys it is the base64 of the pure key; no ASN.1 wrapping.
39112
39113 Signing is enabled by setting private options on the SMTP transport.
39114 These options take (expandable) strings as arguments.
39115
39116 .option dkim_domain smtp string list&!! unset
39117 The domain(s) you want to sign with.
39118 After expansion, this can be a list.
39119 Each element in turn is put into the &%$dkim_domain%& expansion variable
39120 while expanding the remaining signing options.
39121 If it is empty after expansion, DKIM signing is not done,
39122 and no error will result even if &%dkim_strict%& is set.
39123
39124 .option dkim_selector smtp string list&!! unset
39125 This sets the key selector string.
39126 After expansion, which can use &$dkim_domain$&, this can be a list.
39127 Each element in turn is put in the expansion
39128 variable &%$dkim_selector%& which may be used in the &%dkim_private_key%&
39129 option along with &%$dkim_domain%&.
39130 If the option is empty after expansion, DKIM signing is not done for this domain,
39131 and no error will result even if &%dkim_strict%& is set.
39132
39133 .option dkim_private_key smtp string&!! unset
39134 This sets the private key to use.
39135 You can use the &%$dkim_domain%& and
39136 &%$dkim_selector%& expansion variables to determine the private key to use.
39137 The result can either
39138 .ilist
39139 be a valid RSA private key in ASCII armor (.pem file), including line breaks
39140 .next
39141 with GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
39142 be a valid Ed25519 private key (same format as above)
39143 .next
39144 start with a slash, in which case it is treated as a file that contains
39145 the private key
39146 .next
39147 be "0", "false" or the empty string, in which case the message will not
39148 be signed. This case will not result in an error, even if &%dkim_strict%&
39149 is set.
39150 .endlist
39151
39152 To generate keys under OpenSSL:
39153 .code
39154 openssl genrsa -out dkim_rsa.private 2048
39155 openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM
39156 .endd
39157 Take the base-64 lines from the output of the second command, concatenated,
39158 for the DNS TXT record.
39159 See section 3.6 of RFC6376 for the record specification.
39160
39161 Under GnuTLS:
39162 .code
39163 certtool --generate-privkey --rsa --bits=2048 --password='' -8 --outfile=dkim_rsa.private
39164 certtool --load-privkey=dkim_rsa.private --pubkey-info
39165 .endd
39166
39167 Note that RFC 8301 says:
39168 .code
39169 Signers MUST use RSA keys of at least 1024 bits for all keys.
39170 Signers SHOULD use RSA keys of at least 2048 bits.
39171 .endd
39172
39173 Support for EC keys is being developed under
39174 &url(https://datatracker.ietf.org/doc/draft-ietf-dcrup-dkim-crypto/).
39175 They are considerably smaller than RSA keys for equivalent protection.
39176 As they are a recent development, users should consider dual-signing
39177 (by setting a list of selectors, and an expansion for this option)
39178 for some transition period.
39179 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
39180 for EC keys.
39181
39182 OpenSSL 1.1.1 and GnuTLS 3.6.0 can create Ed25519 private keys:
39183 .code
39184 openssl genpkey -algorithm ed25519 -out dkim_ed25519.private
39185 certtool --generate-privkey --key-type=ed25519 --outfile=dkim_ed25519.private
39186 .endd
39187
39188 To produce the required public key value for a DNS record:
39189 .code
39190 openssl pkey -outform DER -pubout -in dkim_ed25519.private | tail -c +13 | base64
39191 certtool --load_privkey=dkim_ed25519.private --pubkey_info --outder | tail -c +13 | base64
39192 .endd
39193
39194 Note that the format
39195 of Ed25519 keys in DNS has not yet been decided; this release supports
39196 both of the leading candidates at this time, a future release will
39197 probably drop support for whichever proposal loses.
39198
39199 .option dkim_hash smtp string&!! sha256
39200 Can be set to any one of the supported hash methods, which are:
39201 .ilist
39202 &`sha1`& &-- should not be used, is old and insecure
39203 .next
39204 &`sha256`& &-- the default
39205 .next
39206 &`sha512`& &-- possibly more secure but less well supported
39207 .endlist
39208
39209 Note that RFC 8301 says:
39210 .code
39211 rsa-sha1 MUST NOT be used for signing or verifying.
39212 .endd
39213
39214 .option dkim_identity smtp string&!! unset
39215 If set after expansion, the value is used to set an "i=" tag in
39216 the signing header. The DKIM standards restrict the permissible
39217 syntax of this optional tag to a mail address, with possibly-empty
39218 local part, an @, and a domain identical to or subdomain of the "d="
39219 tag value. Note that Exim does not check the value.
39220
39221 .option dkim_canon smtp string&!! unset
39222 This option sets the canonicalization method used when signing a message.
39223 The DKIM RFC currently supports two methods: "simple" and "relaxed".
39224 The option defaults to "relaxed" when unset. Note: the current implementation
39225 only supports signing with the same canonicalization method for both headers and body.
39226
39227 .option dkim_strict smtp string&!! unset
39228 This option defines how Exim behaves when signing a message that
39229 should be signed fails for some reason. When the expansion evaluates to
39230 either "1" or "true", Exim will defer. Otherwise Exim will send the message
39231 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
39232 variables here.
39233
39234 .option dkim_sign_headers smtp string&!! "see below"
39235 If set, this option must expand to a colon-separated
39236 list of header names.
39237 Headers with these names, or the absence or such a header, will be included
39238 in the message signature.
39239 When unspecified, the header names listed in RFC4871 will be used,
39240 whether or not each header is present in the message.
39241 The default list is available for the expansion in the macro
39242 "_DKIM_SIGN_HEADERS".
39243
39244 If a name is repeated, multiple headers by that name (or the absence thereof)
39245 will be signed. The textually later headers in the headers part of the
39246 message are signed first, if there are multiples.
39247
39248 A name can be prefixed with either an '=' or a '+' character.
39249 If an '=' prefix is used, all headers that are present with this name
39250 will be signed.
39251 If a '+' prefix if used, all headers that are present with this name
39252 will be signed, and one signature added for a missing header with the
39253 name will be appended.
39254
39255 .new
39256 .option dkim_timestamps smtp integer&!! unset
39257 This option controls the inclusion of timestamp information in the signature.
39258 If not set, no such information will be included.
39259 Otherwise, must be an unsigned number giving an offset in seconds from the current time
39260 for the expiry tag
39261 (eg. 1209600 for two weeks);
39262 both creation (t=) and expiry (x=) tags will be included.
39263
39264 RFC 6376 lists these tags as RECOMMENDED.
39265 .wen
39266
39267
39268 .section "Verifying DKIM signatures in incoming mail" "SECDKIMVFY"
39269 .cindex "DKIM" "verification"
39270
39271 .new
39272 Verification of DKIM signatures in SMTP incoming email is done for all
39273 messages for which an ACL control &%dkim_disable_verify%& has not been set.
39274 .cindex authentication "expansion item"
39275 Performing verification sets up information used by the
39276 &$authresults$& expansion item.
39277 .wen
39278
39279 .new The results of that verification are then made available to the
39280 &%acl_smtp_dkim%& ACL, &new(which can examine and modify them).
39281 By default, this ACL is called once for each
39282 syntactically(!) correct signature in the incoming message.
39283 A missing ACL definition defaults to accept.
39284 If any ACL call does not accept, the message is not accepted.
39285 If a cutthrough delivery was in progress for the message, that is
39286 summarily dropped (having wasted the transmission effort).
39287
39288 To evaluate the &new(verification result) in the ACL
39289 a large number of expansion variables
39290 containing the signature status and its details are set up during the
39291 runtime of the ACL.
39292
39293 Calling the ACL only for existing signatures is not sufficient to build
39294 more advanced policies. For that reason, the global option
39295 &%dkim_verify_signers%&, and a global expansion variable
39296 &%$dkim_signers%& exist.
39297
39298 The global option &%dkim_verify_signers%& can be set to a colon-separated
39299 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
39300 called. It is expanded when the message has been received. At this point,
39301 the expansion variable &%$dkim_signers%& already contains a colon-separated
39302 list of signer domains and identities for the message. When
39303 &%dkim_verify_signers%& is not specified in the main configuration,
39304 it defaults as:
39305 .code
39306 dkim_verify_signers = $dkim_signers
39307 .endd
39308 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
39309 DKIM signature in the message. Current DKIM verifiers may want to explicitly
39310 call the ACL for known domains or identities. This would be achieved as follows:
39311 .code
39312 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
39313 .endd
39314 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
39315 and "ebay.com", plus all domains and identities that have signatures in the message.
39316 You can also be more creative in constructing your policy. For example:
39317 .code
39318 dkim_verify_signers = $sender_address_domain:$dkim_signers
39319 .endd
39320
39321 If a domain or identity is listed several times in the (expanded) value of
39322 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
39323
39324 If multiple signatures match a domain (or identity), the ACL is called once
39325 for each matching signature.
39326
39327
39328 Inside the &%acl_smtp_dkim%&, the following expansion variables are
39329 available (from most to least important):
39330
39331
39332 .vlist
39333 .vitem &%$dkim_cur_signer%&
39334 The signer that is being evaluated in this ACL run. This can be a domain or
39335 an identity. This is one of the list items from the expanded main option
39336 &%dkim_verify_signers%& (see above).
39337
39338 .vitem &%$dkim_verify_status%&
39339 Within the DKIM ACL,
39340 a string describing the general status of the signature. One of
39341 .ilist
39342 &%none%&: There is no signature in the message for the current domain or
39343 identity (as reflected by &%$dkim_cur_signer%&).
39344 .next
39345 &%invalid%&: The signature could not be verified due to a processing error.
39346 More detail is available in &%$dkim_verify_reason%&.
39347 .next
39348 &%fail%&: Verification of the signature failed. More detail is
39349 available in &%$dkim_verify_reason%&.
39350 .next
39351 &%pass%&: The signature passed verification. It is valid.
39352 .endlist
39353
39354 This variable can be overwritten using an ACL 'set' modifier.
39355 This might, for instance, be done to enforce a policy restriction on
39356 hash-method or key-size:
39357 .code
39358 warn condition = ${if eq {$dkim_verify_status}{pass}}
39359 condition = ${if eq {${length_3:$dkim_algo}}{rsa}}
39360 condition = ${if or {{eq {$dkim_algo}{rsa-sha1}} \
39361 {< {$dkim_key_length}{1024}}}}
39362 logwrite = NOTE: forcing DKIM verify fail (was pass)
39363 set dkim_verify_status = fail
39364 set dkim_verify_reason = hash too weak or key too short
39365 .endd
39366
39367 So long as a DKIM ACL is defined (it need do no more than accept),
39368 after all the DKIM ACL runs have completed, the value becomes a
39369 colon-separated list of the values after each run.
39370 This is maintained for the mime, prdr and data ACLs.
39371
39372 .vitem &%$dkim_verify_reason%&
39373 A string giving a little bit more detail when &%$dkim_verify_status%& is either
39374 "fail" or "invalid". One of
39375 .ilist
39376 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
39377 key for the domain could not be retrieved. This may be a temporary problem.
39378 .next
39379 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
39380 record for the domain is syntactically invalid.
39381 .next
39382 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
39383 body hash does not match the one specified in the signature header. This
39384 means that the message body was modified in transit.
39385 .next
39386 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
39387 could not be verified. This may mean that headers were modified,
39388 re-written or otherwise changed in a way which is incompatible with
39389 DKIM verification. It may of course also mean that the signature is forged.
39390 .endlist
39391
39392 This variable can be overwritten, with any value, using an ACL 'set' modifier.
39393
39394 .vitem &%$dkim_domain%&
39395 The signing domain. IMPORTANT: This variable is only populated if there is
39396 an actual signature in the message for the current domain or identity (as
39397 reflected by &%$dkim_cur_signer%&).
39398
39399 .vitem &%$dkim_identity%&
39400 The signing identity, if present. IMPORTANT: This variable is only populated
39401 if there is an actual signature in the message for the current domain or
39402 identity (as reflected by &%$dkim_cur_signer%&).
39403
39404 .vitem &%$dkim_selector%&
39405 The key record selector string.
39406
39407 .vitem &%$dkim_algo%&
39408 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
39409 If running under GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
39410 may also be 'ed25519-sha256'.
39411 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
39412 for EC keys.
39413
39414 Note that RFC 8301 says:
39415 .code
39416 rsa-sha1 MUST NOT be used for signing or verifying.
39417
39418 DKIM signatures identified as having been signed with historic
39419 algorithms (currently, rsa-sha1) have permanently failed evaluation
39420 .endd
39421
39422 To enforce this you must have a DKIM ACL which checks this variable
39423 and overwrites the &$dkim_verify_status$& variable as discussed above.
39424
39425 .vitem &%$dkim_canon_body%&
39426 The body canonicalization method. One of 'relaxed' or 'simple'.
39427
39428 .vitem &%$dkim_canon_headers%&
39429 The header canonicalization method. One of 'relaxed' or 'simple'.
39430
39431 .vitem &%$dkim_copiedheaders%&
39432 A transcript of headers and their values which are included in the signature
39433 (copied from the 'z=' tag of the signature).
39434 Note that RFC6376 requires that verification fail if the From: header is
39435 not included in the signature. Exim does not enforce this; sites wishing
39436 strict enforcement should code the check explicitly.
39437
39438 .vitem &%$dkim_bodylength%&
39439 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
39440 limit was set by the signer, "9999999999999" is returned. This makes sure
39441 that this variable always expands to an integer value.
39442 .new
39443 &*Note:*& The presence of the signature tag specifying a signing body length
39444 is one possible route to spoofing of valid DKIM signatures.
39445 A paranoid implementation might wish to regard signature where this variable
39446 shows less than the "no limit" return as being invalid.
39447 .wen
39448
39449 .vitem &%$dkim_created%&
39450 UNIX timestamp reflecting the date and time when the signature was created.
39451 When this was not specified by the signer, "0" is returned.
39452
39453 .vitem &%$dkim_expires%&
39454 UNIX timestamp reflecting the date and time when the signer wants the
39455 signature to be treated as "expired". When this was not specified by the
39456 signer, "9999999999999" is returned. This makes it possible to do useful
39457 integer size comparisons against this value.
39458 Note that Exim does not check this value.
39459
39460 .vitem &%$dkim_headernames%&
39461 A colon-separated list of names of headers included in the signature.
39462
39463 .vitem &%$dkim_key_testing%&
39464 "1" if the key record has the "testing" flag set, "0" if not.
39465
39466 .vitem &%$dkim_key_nosubdomains%&
39467 "1" if the key record forbids subdomaining, "0" otherwise.
39468
39469 .vitem &%$dkim_key_srvtype%&
39470 Service type (tag s=) from the key record. Defaults to "*" if not specified
39471 in the key record.
39472
39473 .vitem &%$dkim_key_granularity%&
39474 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
39475 in the key record.
39476
39477 .vitem &%$dkim_key_notes%&
39478 Notes from the key record (tag n=).
39479
39480 .vitem &%$dkim_key_length%&
39481 Number of bits in the key.
39482
39483 Note that RFC 8301 says:
39484 .code
39485 Verifiers MUST NOT consider signatures using RSA keys of
39486 less than 1024 bits as valid signatures.
39487 .endd
39488
39489 To enforce this you must have a DKIM ACL which checks this variable
39490 and overwrites the &$dkim_verify_status$& variable as discussed above.
39491 As EC keys are much smaller, the check should only do this for RSA keys.
39492
39493 .endlist
39494
39495 In addition, two ACL conditions are provided:
39496
39497 .vlist
39498 .vitem &%dkim_signers%&
39499 ACL condition that checks a colon-separated list of domains or identities
39500 for a match against the domain or identity that the ACL is currently verifying
39501 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
39502 verb to a group of domains or identities. For example:
39503
39504 .code
39505 # Warn when Mail purportedly from GMail has no gmail signature
39506 warn log_message = GMail sender without gmail.com DKIM signature
39507 sender_domains = gmail.com
39508 dkim_signers = gmail.com
39509 dkim_status = none
39510 .endd
39511
39512 Note that the above does not check for a total lack of DKIM signing;
39513 for that check for empty &$h_DKIM-Signature:$& in the data ACL.
39514
39515 .vitem &%dkim_status%&
39516 ACL condition that checks a colon-separated list of possible DKIM verification
39517 results against the actual result of verification. This is typically used
39518 to restrict an ACL verb to a list of verification outcomes, for example:
39519
39520 .code
39521 deny message = Mail from Paypal with invalid/missing signature
39522 sender_domains = paypal.com:paypal.de
39523 dkim_signers = paypal.com:paypal.de
39524 dkim_status = none:invalid:fail
39525 .endd
39526
39527 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
39528 see the documentation of the &%$dkim_verify_status%& expansion variable above
39529 for more information of what they mean.
39530 .endlist
39531
39532
39533
39534
39535 .section "SPF (Sender Policy Framework)" SECSPF
39536 .cindex SPF verification
39537
39538 SPF is a mechanism whereby a domain may assert which IP addresses may transmit
39539 messages with its domain in the envelope from, documented by RFC 7208.
39540 For more information on SPF see &url(http://www.openspf.org).
39541
39542 Messages sent by a system not authorised will fail checking of such assertions.
39543 This includes retransmissions done by traditional forwarders.
39544
39545 SPF verification support is built into Exim if SUPPORT_SPF=yes is set in
39546 &_Local/Makefile_&. The support uses the &_libspf2_& library
39547 &url(http://www.libspf2.org/).
39548 There is no Exim involvement in the transmission of messages;
39549 publishing certain DNS records is all that is required.
39550
39551 For verification, an ACL condition and an expansion lookup are provided.
39552 .cindex authentication "expansion item"
39553 Performing verification sets up information used by the
39554 &$authresults$& expansion item.
39555
39556
39557 .cindex SPF "ACL condition"
39558 .cindex ACL "spf condition"
39559 The ACL condition "spf" can be used at or after the MAIL ACL.
39560 It takes as an argument a list of strings giving the outcome of the SPF check,
39561 and will succeed for any matching outcome.
39562 Valid strings are:
39563 .vlist
39564 .vitem &%pass%&
39565 The SPF check passed, the sending host is positively verified by SPF.
39566
39567 .vitem &%fail%&
39568 The SPF check failed, the sending host is NOT allowed to send mail for the
39569 domain in the envelope-from address.
39570
39571 .vitem &%softfail%&
39572 The SPF check failed, but the queried domain can't absolutely confirm that this
39573 is a forgery.
39574
39575 .vitem &%none%&
39576 The queried domain does not publish SPF records.
39577
39578 .vitem &%neutral%&
39579 The SPF check returned a "neutral" state. This means the queried domain has
39580 published a SPF record, but wants to allow outside servers to send mail under
39581 its domain as well. This should be treated like "none".
39582
39583 .vitem &%permerror%&
39584 This indicates a syntax error in the SPF record of the queried domain.
39585 You may deny messages when this occurs.
39586
39587 .vitem &%temperror%&
39588 This indicates a temporary error during all processing, including Exim's
39589 SPF processing. You may defer messages when this occurs.
39590 .endlist
39591
39592 You can prefix each string with an exclamation mark to invert
39593 its meaning, for example "!fail" will match all results but
39594 "fail". The string list is evaluated left-to-right, in a
39595 short-circuit fashion.
39596
39597 Example:
39598 .code
39599 deny spf = fail
39600 message = $sender_host_address is not allowed to send mail from \
39601 ${if def:sender_address_domain \
39602 {$sender_address_domain}{$sender_helo_name}}. \
39603 Please see http://www.openspf.org/Why?scope=\
39604 ${if def:sender_address_domain {mfrom}{helo}};\
39605 identity=${if def:sender_address_domain \
39606 {$sender_address}{$sender_helo_name}};\
39607 ip=$sender_host_address
39608 .endd
39609
39610 When the spf condition has run, it sets up several expansion
39611 variables:
39612
39613 .cindex SPF "verification variables"
39614 .vlist
39615 .vitem &$spf_header_comment$&
39616 .vindex &$spf_header_comment$&
39617 This contains a human-readable string describing the outcome
39618 of the SPF check. You can add it to a custom header or use
39619 it for logging purposes.
39620
39621 .vitem &$spf_received$&
39622 .vindex &$spf_received$&
39623 This contains a complete Received-SPF: header that can be
39624 added to the message. Please note that according to the SPF
39625 draft, this header must be added at the top of the header
39626 list. Please see section 10 on how you can do this.
39627
39628 Note: in case of "Best-guess" (see below), the convention is
39629 to put this string in a header called X-SPF-Guess: instead.
39630
39631 .vitem &$spf_result$&
39632 .vindex &$spf_result$&
39633 This contains the outcome of the SPF check in string form,
39634 one of pass, fail, softfail, none, neutral, permerror or
39635 temperror.
39636
39637 .vitem &$spf_result_guessed$&
39638 .vindex &$spf_result_guessed$&
39639 This boolean is true only if a best-guess operation was used
39640 and required in order to obtain a result.
39641
39642 .vitem &$spf_smtp_comment$&
39643 .vindex &$spf_smtp_comment$&
39644 This contains a string that can be used in a SMTP response
39645 to the calling party. Useful for "fail".
39646 .endlist
39647
39648
39649 .cindex SPF "ACL condition"
39650 .cindex ACL "spf_guess condition"
39651 .cindex SPF "best guess"
39652 In addition to SPF, you can also perform checks for so-called
39653 "Best-guess". Strictly speaking, "Best-guess" is not standard
39654 SPF, but it is supported by the same framework that enables SPF
39655 capability.
39656 Refer to &url(http://www.openspf.org/FAQ/Best_guess_record)
39657 for a description of what it means.
39658
39659 To access this feature, simply use the spf_guess condition in place
39660 of the spf one. For example:
39661
39662 .code
39663 deny spf_guess = fail
39664 message = $sender_host_address doesn't look trustworthy to me
39665 .endd
39666
39667 In case you decide to reject messages based on this check, you
39668 should note that although it uses the same framework, "Best-guess"
39669 is not SPF, and therefore you should not mention SPF at all in your
39670 reject message.
39671
39672 When the spf_guess condition has run, it sets up the same expansion
39673 variables as when spf condition is run, described above.
39674
39675 Additionally, since Best-guess is not standardized, you may redefine
39676 what "Best-guess" means to you by redefining the main configuration
39677 &%spf_guess%& option.
39678 For example, the following:
39679
39680 .code
39681 spf_guess = v=spf1 a/16 mx/16 ptr ?all
39682 .endd
39683
39684 would relax host matching rules to a broader network range.
39685
39686
39687 .cindex SPF "lookup expansion"
39688 .cindex lookup spf
39689 A lookup expansion is also available. It takes an email
39690 address as the key and an IP address as the database:
39691
39692 .code
39693 ${lookup {username@domain} spf {ip.ip.ip.ip}}
39694 .endd
39695
39696 The lookup will return the same result strings as can appear in
39697 &$spf_result$& (pass,fail,softfail,neutral,none,err_perm,err_temp).
39698 Currently, only IPv4 addresses are supported.
39699
39700
39701
39702
39703 . ////////////////////////////////////////////////////////////////////////////
39704 . ////////////////////////////////////////////////////////////////////////////
39705
39706 .chapter "Proxies" "CHAPproxies" &&&
39707 "Proxy support"
39708 .cindex "proxy support"
39709 .cindex "proxy" "access via"
39710
39711 A proxy is an intermediate system through which communication is passed.
39712 Proxies may provide a security, availability or load-distribution function.
39713
39714
39715 .section "Inbound proxies" SECTproxyInbound
39716 .cindex proxy inbound
39717 .cindex proxy "server side"
39718 .cindex proxy "Proxy protocol"
39719 .cindex "Proxy protocol" proxy
39720
39721 Exim has support for receiving inbound SMTP connections via a proxy
39722 that uses &"Proxy Protocol"& to speak to it.
39723 To include this support, include &"SUPPORT_PROXY=yes"&
39724 in Local/Makefile.
39725
39726 It was built on specifications from:
39727 (&url(http://haproxy.1wt.eu/download/1.5/doc/proxy-protocol.txt)).
39728 That URL was revised in May 2014 to version 2 spec:
39729 (&url(http://git.1wt.eu/web?p=haproxy.git;a=commitdiff;h=afb768340c9d7e50d8e)).
39730
39731 The purpose of this facility is so that an application load balancer,
39732 such as HAProxy, can sit in front of several Exim servers
39733 to distribute load.
39734 Exim uses the local protocol communication with the proxy to obtain
39735 the remote SMTP system IP address and port information.
39736 There is no logging if a host passes or
39737 fails Proxy Protocol negotiation, but it can easily be determined and
39738 recorded in an ACL (example is below).
39739
39740 Use of a proxy is enabled by setting the &%hosts_proxy%&
39741 main configuration option to a hostlist; connections from these
39742 hosts will use Proxy Protocol.
39743 Exim supports both version 1 and version 2 of the Proxy Protocol and
39744 automatically determines which version is in use.
39745
39746 The Proxy Protocol header is the first data received on a TCP connection
39747 and is inserted before any TLS-on-connect handshake from the client; Exim
39748 negotiates TLS between Exim-as-server and the remote client, not between
39749 Exim and the proxy server.
39750
39751 The following expansion variables are usable
39752 (&"internal"& and &"external"& here refer to the interfaces
39753 of the proxy):
39754 .display
39755 &'proxy_external_address '& IP of host being proxied or IP of remote interface of proxy
39756 &'proxy_external_port '& Port of host being proxied or Port on remote interface of proxy
39757 &'proxy_local_address '& IP of proxy server inbound or IP of local interface of proxy
39758 &'proxy_local_port '& Port of proxy server inbound or Port on local interface of proxy
39759 &'proxy_session '& boolean: SMTP connection via proxy
39760 .endd
39761 If &$proxy_session$& is set but &$proxy_external_address$& is empty
39762 there was a protocol error.
39763
39764 Since the real connections are all coming from the proxy, and the
39765 per host connection tracking is done before Proxy Protocol is
39766 evaluated, &%smtp_accept_max_per_host%& must be set high enough to
39767 handle all of the parallel volume you expect per inbound proxy.
39768 With the option set so high, you lose the ability
39769 to protect your server from many connections from one IP.
39770 In order to prevent your server from overload, you
39771 need to add a per connection ratelimit to your connect ACL.
39772 A possible solution is:
39773 .display
39774 # Set max number of connections per host
39775 LIMIT = 5
39776 # Or do some kind of IP lookup in a flat file or database
39777 # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
39778
39779 defer message = Too many connections from this IP right now
39780 ratelimit = LIMIT / 5s / per_conn / strict
39781 .endd
39782
39783
39784
39785 .section "Outbound proxies" SECTproxySOCKS
39786 .cindex proxy outbound
39787 .cindex proxy "client side"
39788 .cindex proxy SOCKS
39789 .cindex SOCKS proxy
39790 Exim has support for sending outbound SMTP via a proxy
39791 using a protocol called SOCKS5 (defined by RFC1928).
39792 The support can be optionally included by defining SUPPORT_SOCKS=yes in
39793 Local/Makefile.
39794
39795 Use of a proxy is enabled by setting the &%socks_proxy%& option
39796 on an smtp transport.
39797 The option value is expanded and should then be a list
39798 (colon-separated by default) of proxy specifiers.
39799 Each proxy specifier is a list
39800 (space-separated by default) where the initial element
39801 is an IP address and any subsequent elements are options.
39802
39803 Options are a string <name>=<value>.
39804 The list of options is in the following table:
39805 .display
39806 &'auth '& authentication method
39807 &'name '& authentication username
39808 &'pass '& authentication password
39809 &'port '& tcp port
39810 &'tmo '& connection timeout
39811 &'pri '& priority
39812 &'weight '& selection bias
39813 .endd
39814
39815 More details on each of these options follows:
39816
39817 .ilist
39818 .cindex authentication "to proxy"
39819 .cindex proxy authentication
39820 &%auth%&: Either &"none"& (default) or &"name"&.
39821 Using &"name"& selects username/password authentication per RFC 1929
39822 for access to the proxy.
39823 Default is &"none"&.
39824 .next
39825 &%name%&: sets the username for the &"name"& authentication method.
39826 Default is empty.
39827 .next
39828 &%pass%&: sets the password for the &"name"& authentication method.
39829 Default is empty.
39830 .next
39831 &%port%&: the TCP port number to use for the connection to the proxy.
39832 Default is 1080.
39833 .next
39834 &%tmo%&: sets a connection timeout in seconds for this proxy.
39835 Default is 5.
39836 .next
39837 &%pri%&: specifies a priority for the proxy within the list,
39838 higher values being tried first.
39839 The default priority is 1.
39840 .next
39841 &%weight%&: specifies a selection bias.
39842 Within a priority set servers are queried in a random fashion,
39843 weighted by this value.
39844 The default value for selection bias is 1.
39845 .endlist
39846
39847 Proxies from the list are tried according to their priority
39848 and weight settings until one responds. The timeout for the
39849 overall connection applies to the set of proxied attempts.
39850
39851 .section Logging SECTproxyLog
39852 To log the (local) IP of a proxy in the incoming or delivery logline,
39853 add &"+proxy"& to the &%log_selector%& option.
39854 This will add a component tagged with &"PRX="& to the line.
39855
39856 . ////////////////////////////////////////////////////////////////////////////
39857 . ////////////////////////////////////////////////////////////////////////////
39858
39859 .chapter "Internationalisation" "CHAPi18n" &&&
39860 "Internationalisation""
39861 .cindex internationalisation "email address"
39862 .cindex EAI
39863 .cindex i18n
39864 .cindex utf8 "mail name handling"
39865
39866 Exim has support for Internationalised mail names.
39867 To include this it must be built with SUPPORT_I18N and the libidn library.
39868 Standards supported are RFCs 2060, 5890, 6530 and 6533.
39869
39870 If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not
39871 instead of it) then IDNA2008 is supported; this adds an extra library
39872 requirement, upon libidn2.
39873
39874 .section "MTA operations" SECTi18nMTA
39875 .cindex SMTPUTF8 "ESMTP option"
39876 The main configuration option &%smtputf8_advertise_hosts%& specifies
39877 a host list. If this matches the sending host and
39878 accept_8bitmime is true (the default) then the ESMTP option
39879 SMTPUTF8 will be advertised.
39880
39881 If the sender specifies the SMTPUTF8 option on a MAIL command
39882 international handling for the message is enabled and
39883 the expansion variable &$message_smtputf8$& will have value TRUE.
39884
39885 The option &%allow_utf8_domains%& is set to true for this
39886 message. All DNS lookups are converted to a-label form
39887 whatever the setting of &%allow_utf8_domains%&
39888 when Exim is built with SUPPORT_I18N.
39889
39890 Both localparts and domain are maintained as the original
39891 UTF-8 form internally; any comparison or regular-expression use will
39892 require appropriate care. Filenames created, eg. by
39893 the appendfile transport, will have UTF-8 names.
39894
39895 HELO names sent by the smtp transport will have any UTF-8
39896 components expanded to a-label form,
39897 and any certificate name checks will be done using the a-label
39898 form of the name.
39899
39900 .cindex log protocol
39901 .cindex SMTPUTF8 logging
39902 .cindex i18n logging
39903 Log lines and Received-by: header lines will acquire a "utf8"
39904 prefix on the protocol element, eg. utf8esmtp.
39905
39906 The following expansion operators can be used:
39907 .code
39908 ${utf8_domain_to_alabel:str}
39909 ${utf8_domain_from_alabel:str}
39910 ${utf8_localpart_to_alabel:str}
39911 ${utf8_localpart_from_alabel:str}
39912 .endd
39913
39914 .cindex utf8 "address downconversion"
39915 .cindex i18n "utf8 address downconversion"
39916 The RCPT ACL
39917 may use the following modifier:
39918 .display
39919 control = utf8_downconvert
39920 control = utf8_downconvert/<value>
39921 .endd
39922 This sets a flag requiring that addresses are converted to
39923 a-label form before smtp delivery, for use in a
39924 Message Submission Agent context.
39925 If a value is appended it may be:
39926 .display
39927 &`1 `& (default) mandatory downconversion
39928 &`0 `& no downconversion
39929 &`-1 `& if SMTPUTF8 not supported by destination host
39930 .endd
39931
39932 If mua_wrapper is set, the utf8_downconvert control
39933 is initially set to -1.
39934
39935 .new
39936 The smtp transport has an option &%utf8_downconvert%&.
39937 If set it must expand to one of the three values described above,
39938 and it overrides any previously set value.
39939 .wen
39940
39941
39942 There is no explicit support for VRFY and EXPN.
39943 Configurations supporting these should inspect
39944 &$smtp_command_argument$& for an SMTPUTF8 argument.
39945
39946 There is no support for LMTP on Unix sockets.
39947 Using the "lmtp" protocol option on an smtp transport,
39948 for LMTP over TCP, should work as expected.
39949
39950 There is no support for DSN unitext handling,
39951 and no provision for converting logging from or to UTF-8.
39952
39953
39954
39955 .section "MDA operations" SECTi18nMDA
39956 To aid in constructing names suitable for IMAP folders
39957 the following expansion operator can be used:
39958 .code
39959 ${imapfolder {<string>} {<sep>} {<specials>}}
39960 .endd
39961
39962 The string is converted from the charset specified by
39963 the "headers charset" command (in a filter file)
39964 or &%headers_charset%& main configuration option (otherwise),
39965 to the
39966 modified UTF-7 encoding specified by RFC 2060,
39967 with the following exception: All occurrences of <sep>
39968 (which has to be a single character)
39969 are replaced with periods ("."), and all periods and slashes that are not
39970 <sep> and are not in the <specials> string are BASE64 encoded.
39971
39972 The third argument can be omitted, defaulting to an empty string.
39973 The second argument can be omitted, defaulting to "/".
39974
39975 This is the encoding used by Courier for Maildir names on disk, and followed
39976 by many other IMAP servers.
39977
39978 Examples:
39979 .display
39980 &`${imapfolder {Foo/Bar}} `& yields &`Foo.Bar`&
39981 &`${imapfolder {Foo/Bar}{.}{/}} `& yields &`Foo&&AC8-Bar`&
39982 &`${imapfolder {Räksmörgås}} `& yields &`R&&AOQ-ksm&&APY-rg&&AOU-s`&
39983 .endd
39984
39985 Note that the source charset setting is vital, and also that characters
39986 must be representable in UTF-16.
39987
39988
39989 . ////////////////////////////////////////////////////////////////////////////
39990 . ////////////////////////////////////////////////////////////////////////////
39991
39992 .chapter "Events" "CHAPevents" &&&
39993 "Events"
39994 .cindex events
39995
39996 The events mechanism in Exim can be used to intercept processing at a number
39997 of points. It was originally invented to give a way to do customised logging
39998 actions (for example, to a database) but can also be used to modify some
39999 processing actions.
40000
40001 Most installations will never need to use Events.
40002 The support can be left out of a build by defining DISABLE_EVENT=yes
40003 in &_Local/Makefile_&.
40004
40005 There are two major classes of events: main and transport.
40006 The main configuration option &%event_action%& controls reception events;
40007 a transport option &%event_action%& controls delivery events.
40008
40009 Both options are a string which is expanded when the event fires.
40010 An example might look like:
40011 .cindex logging custom
40012 .code
40013 event_action = ${if eq {msg:delivery}{$event_name} \
40014 {${lookup pgsql {SELECT * FROM record_Delivery( \
40015 '${quote_pgsql:$sender_address_domain}',\
40016 '${quote_pgsql:${lc:$sender_address_local_part}}', \
40017 '${quote_pgsql:$domain}', \
40018 '${quote_pgsql:${lc:$local_part}}', \
40019 '${quote_pgsql:$host_address}', \
40020 '${quote_pgsql:${lc:$host}}', \
40021 '${quote_pgsql:$message_exim_id}')}} \
40022 } {}}
40023 .endd
40024
40025 Events have names which correspond to the point in process at which they fire.
40026 The name is placed in the variable &$event_name$& and the event action
40027 expansion must check this, as it will be called for every possible event type.
40028
40029 The current list of events is:
40030 .display
40031 &`dane:fail after transport `& per connection
40032 &`msg:complete after main `& per message
40033 &`msg:delivery after transport `& per recipient
40034 &`msg:rcpt:host:defer after transport `& per recipient per host
40035 &`msg:rcpt:defer after transport `& per recipient
40036 &`msg:host:defer after transport `& per attempt
40037 &`msg:fail:delivery after transport `& per recipient
40038 &`msg:fail:internal after main `& per recipient
40039 &`tcp:connect before transport `& per connection
40040 &`tcp:close after transport `& per connection
40041 &`tls:cert before both `& per certificate in verification chain
40042 &`smtp:connect after transport `& per connection
40043 .endd
40044 New event types may be added in future.
40045
40046 The event name is a colon-separated list, defining the type of
40047 event in a tree of possibilities. It may be used as a list
40048 or just matched on as a whole. There will be no spaces in the name.
40049
40050 The second column in the table above describes whether the event fires
40051 before or after the action is associates with. Those which fire before
40052 can be used to affect that action (more on this below).
40053
40054 The third column in the table above says what section of the configuration
40055 should define the event action.
40056
40057 An additional variable, &$event_data$&, is filled with information varying
40058 with the event type:
40059 .display
40060 &`dane:fail `& failure reason
40061 &`msg:delivery `& smtp confirmation message
40062 &`msg:rcpt:host:defer `& error string
40063 &`msg:rcpt:defer `& error string
40064 &`msg:host:defer `& error string
40065 &`tls:cert `& verification chain depth
40066 &`smtp:connect `& smtp banner
40067 .endd
40068
40069 The :defer events populate one extra variable: &$event_defer_errno$&.
40070
40071 For complex operations an ACL expansion can be used in &%event_action%&
40072 however due to the multiple contexts that Exim operates in during
40073 the course of its processing:
40074 .ilist
40075 variables set in transport events will not be visible outside that
40076 transport call
40077 .next
40078 acl_m variables in a server context are lost on a new connection,
40079 and after smtp helo/ehlo/mail/starttls/rset commands
40080 .endlist
40081 Using an ACL expansion with the logwrite modifier can be
40082 a useful way of writing to the main log.
40083
40084 The expansion of the event_action option should normally
40085 return an empty string. Should it return anything else the
40086 following will be forced:
40087 .display
40088 &`tcp:connect `& do not connect
40089 &`tls:cert `& refuse verification
40090 &`smtp:connect `& close connection
40091 .endd
40092 All other message types ignore the result string, and
40093 no other use is made of it.
40094
40095 For a tcp:connect event, if the connection is being made to a proxy
40096 then the address and port variables will be that of the proxy and not
40097 the target system.
40098
40099 For tls:cert events, if GnuTLS is in use this will trigger only per
40100 chain element received on the connection.
40101 For OpenSSL it will trigger for every chain element including those
40102 loaded locally.
40103
40104 . ////////////////////////////////////////////////////////////////////////////
40105 . ////////////////////////////////////////////////////////////////////////////
40106
40107 .chapter "Adding new drivers or lookup types" "CHID13" &&&
40108 "Adding drivers or lookups"
40109 .cindex "adding drivers"
40110 .cindex "new drivers, adding"
40111 .cindex "drivers" "adding new"
40112 The following actions have to be taken in order to add a new router, transport,
40113 authenticator, or lookup type to Exim:
40114
40115 .olist
40116 Choose a name for the driver or lookup type that does not conflict with any
40117 existing name; I will use &"newdriver"& in what follows.
40118 .next
40119 Add to &_src/EDITME_& the line:
40120 .display
40121 <&'type'&>&`_NEWDRIVER=yes`&
40122 .endd
40123 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
40124 code is not to be included in the binary by default, comment this line out. You
40125 should also add any relevant comments about the driver or lookup type.
40126 .next
40127 Add to &_src/config.h.defaults_& the line:
40128 .code
40129 #define <type>_NEWDRIVER
40130 .endd
40131 .next
40132 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
40133 and create a table entry as is done for all the other drivers and lookup types.
40134 .next
40135 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
40136 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
40137 Add your &`NEWDRIVER`& to that list.
40138 As long as the dynamic module would be named &_newdriver.so_&, you can use the
40139 simple form that most lookups have.
40140 .next
40141 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
40142 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
40143 driver or lookup type and add it to the definition of OBJ.
40144 .next
40145 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
40146 &_src_&.
40147 .next
40148 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
40149 as for other drivers and lookups.
40150 .endlist
40151
40152 Then all you need to do is write the code! A good way to start is to make a
40153 proforma by copying an existing module of the same type, globally changing all
40154 occurrences of the name, and cutting out most of the code. Note that any
40155 options you create must be listed in alphabetical order, because the tables are
40156 searched using a binary chop procedure.
40157
40158 There is a &_README_& file in each of the sub-directories of &_src_& describing
40159 the interface that is expected.
40160
40161
40162
40163
40164 . ////////////////////////////////////////////////////////////////////////////
40165 . ////////////////////////////////////////////////////////////////////////////
40166
40167 . /////////////////////////////////////////////////////////////////////////////
40168 . These lines are processing instructions for the Simple DocBook Processor that
40169 . Philip Hazel has developed as a less cumbersome way of making PostScript and
40170 . PDFs than using xmlto and fop. They will be ignored by all other XML
40171 . processors.
40172 . /////////////////////////////////////////////////////////////////////////////
40173
40174 .literal xml
40175 <?sdop
40176 format="newpage"
40177 foot_right_recto="&chaptertitle;"
40178 foot_right_verso="&chaptertitle;"
40179 ?>
40180 .literal off
40181
40182 .makeindex "Options index" "option"
40183 .makeindex "Variables index" "variable"
40184 .makeindex "Concept index" "concept"
40185
40186
40187 . /////////////////////////////////////////////////////////////////////////////
40188 . /////////////////////////////////////////////////////////////////////////////