Bug 1454: Option -oMm for message reference
[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 "4.80"
49 .include ./local_params
50
51 .set ACL "access control lists (ACLs)"
52 .set I "&nbsp;&nbsp;&nbsp;&nbsp;"
53
54 .macro copyyear
55 2014
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 .endtable
440
441 The main specification and the specification of the filtering language are also
442 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
443 &<<SECTavail>>& below tells you how to get hold of these.
444
445
446
447 .section "FTP and web sites" "SECID2"
448 .cindex "web site"
449 .cindex "FTP site"
450 The primary site for Exim source distributions is currently the University of
451 Cambridge's FTP site, whose contents are described in &'Where to find the Exim
452 distribution'& below. In addition, there is a web site and an FTP site at
453 &%exim.org%&. These are now also hosted at the University of Cambridge. The
454 &%exim.org%& site was previously hosted for a number of years by Energis
455 Squared, formerly Planet Online Ltd, whose support I gratefully acknowledge.
456
457 .cindex "wiki"
458 .cindex "FAQ"
459 As well as Exim distribution tar files, the Exim web site contains a number of
460 differently formatted versions of the documentation. A recent addition to the
461 online information is the Exim wiki (&url(http://wiki.exim.org)),
462 which contains what used to be a separate FAQ, as well as various other
463 examples, tips, and know-how that have been contributed by Exim users.
464
465 .cindex Bugzilla
466 An Exim Bugzilla exists at &url(http://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
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 "Exim training" "SECID4"
496 .cindex "training courses"
497 Training courses in Cambridge (UK) used to be run annually by the author of
498 Exim, before he retired. At the time of writing, there are no plans to run
499 further Exim courses in Cambridge. However, if that changes, relevant
500 information will be posted at &url(http://www-tus.csx.cam.ac.uk/courses/exim/).
501
502 .section "Bug reports" "SECID5"
503 .cindex "bug reports"
504 .cindex "reporting bugs"
505 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
506 via the Bugzilla (&url(http://bugs.exim.org)). However, if you are unsure
507 whether some behaviour is a bug or not, the best thing to do is to post a
508 message to the &'exim-dev'& mailing list and have it discussed.
509
510
511
512 .section "Where to find the Exim distribution" "SECTavail"
513 .cindex "FTP site"
514 .cindex "distribution" "ftp site"
515 The master ftp site for the Exim distribution is
516 .display
517 &*ftp://ftp.csx.cam.ac.uk/pub/software/email/exim*&
518 .endd
519 This is mirrored by
520 .display
521 &*ftp://ftp.exim.org/pub/exim*&
522 .endd
523 The file references that follow are relative to the &_exim_& directories at
524 these sites. There are now quite a number of independent mirror sites around
525 the world. Those that I know about are listed in the file called &_Mirrors_&.
526
527 Within the &_exim_& directory there are subdirectories called &_exim3_& (for
528 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
529 distributions), and &_Testing_& for testing versions. In the &_exim4_&
530 subdirectory, the current release can always be found in files called
531 .display
532 &_exim-n.nn.tar.gz_&
533 &_exim-n.nn.tar.bz2_&
534 .endd
535 where &'n.nn'& is the highest such version number in the directory. The two
536 files contain identical data; the only difference is the type of compression.
537 The &_.bz2_& file is usually a lot smaller than the &_.gz_& file.
538
539 .cindex "distribution" "signing details"
540 .cindex "distribution" "public key"
541 .cindex "public key for signed distribution"
542 The distributions will be PGP signed by an individual key of the Release
543 Coordinator. This key will have a uid containing an email address in the
544 &'exim.org'& domain and will have signatures from other people, including
545 other Exim maintainers. We expect that the key will be in the "strong set" of
546 PGP keys. There should be a trust path to that key from Nigel Metheringham's
547 PGP key, a version of which can be found in the release directory in the file
548 &_nigel-pubkey.asc_&. All keys used will be available in public keyserver pools,
549 such as &'pool.sks-keyservers.net'&.
550
551 At time of last update, releases were being made by Phil Pennock and signed with
552 key &'0x403043153903637F'&, although that key is expected to be replaced in 2013.
553 A trust path from Nigel's key to Phil's can be observed at
554 &url(https://www.security.spodhuis.org/exim-trustpath).
555
556 Releases have also been authorized to be performed by Todd Lyons who signs with
557 key &'0xC4F4F94804D29EBA'&. A direct trust path exists between previous RE Phil
558 Pennock and Todd Lyons through a common associate.
559
560 The signatures for the tar bundles are in:
561 .display
562 &_exim-n.nn.tar.gz.asc_&
563 &_exim-n.nn.tar.bz2.asc_&
564 .endd
565 For each released version, the log of changes is made separately available in a
566 separate file in the directory &_ChangeLogs_& so that it is possible to
567 find out what has changed without having to download the entire distribution.
568
569 .cindex "documentation" "available formats"
570 The main distribution contains ASCII versions of this specification and other
571 documentation; other formats of the documents are available in separate files
572 inside the &_exim4_& directory of the FTP site:
573 .display
574 &_exim-html-n.nn.tar.gz_&
575 &_exim-pdf-n.nn.tar.gz_&
576 &_exim-postscript-n.nn.tar.gz_&
577 &_exim-texinfo-n.nn.tar.gz_&
578 .endd
579 These tar files contain only the &_doc_& directory, not the complete
580 distribution, and are also available in &_.bz2_& as well as &_.gz_& forms.
581
582
583 .section "Limitations" "SECID6"
584 .ilist
585 .cindex "limitations of Exim"
586 .cindex "bang paths" "not handled by Exim"
587 Exim is designed for use as an Internet MTA, and therefore handles addresses in
588 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
589 simple two-component bang paths can be converted by a straightforward rewriting
590 configuration. This restriction does not prevent Exim from being interfaced to
591 UUCP as a transport mechanism, provided that domain addresses are used.
592 .next
593 .cindex "domainless addresses"
594 .cindex "address" "without domain"
595 Exim insists that every address it handles has a domain attached. For incoming
596 local messages, domainless addresses are automatically qualified with a
597 configured domain value. Configuration options specify from which remote
598 systems unqualified addresses are acceptable. These are then qualified on
599 arrival.
600 .next
601 .cindex "transport" "external"
602 .cindex "external transports"
603 The only external transport mechanisms that are currently implemented are SMTP
604 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
605 transport is available, and there are facilities for writing messages to files
606 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
607 to send messages to other transport mechanisms such as UUCP, provided they can
608 handle domain-style addresses. Batched SMTP input is also catered for.
609 .next
610 Exim is not designed for storing mail for dial-in hosts. When the volumes of
611 such mail are large, it is better to get the messages &"delivered"& into files
612 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
613 other means.
614 .next
615 Although Exim does have basic facilities for scanning incoming messages, these
616 are not comprehensive enough to do full virus or spam scanning. Such operations
617 are best carried out using additional specialized software packages. If you
618 compile Exim with the content-scanning extension, straightforward interfaces to
619 a number of common scanners are provided.
620 .endlist
621
622
623 .section "Run time configuration" "SECID7"
624 Exim's run time configuration is held in a single text file that is divided
625 into a number of sections. The entries in this file consist of keywords and
626 values, in the style of Smail 3 configuration files. A default configuration
627 file which is suitable for simple online installations is provided in the
628 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
629
630
631 .section "Calling interface" "SECID8"
632 .cindex "Sendmail compatibility" "command line interface"
633 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
634 can be a straight replacement for &_/usr/lib/sendmail_& or
635 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
636 about Sendmail in order to run Exim. For actions other than sending messages,
637 Sendmail-compatible options also exist, but those that produce output (for
638 example, &%-bp%&, which lists the messages on the queue) do so in Exim's own
639 format. There are also some additional options that are compatible with Smail
640 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
641 documents all Exim's command line options. This information is automatically
642 made into the man page that forms part of the Exim distribution.
643
644 Control of messages on the queue can be done via certain privileged command
645 line options. There is also an optional monitor program called &'eximon'&,
646 which displays current information in an X window, and which contains a menu
647 interface to Exim's command line administration options.
648
649
650
651 .section "Terminology" "SECID9"
652 .cindex "terminology definitions"
653 .cindex "body of message" "definition of"
654 The &'body'& of a message is the actual data that the sender wants to transmit.
655 It is the last part of a message, and is separated from the &'header'& (see
656 below) by a blank line.
657
658 .cindex "bounce message" "definition of"
659 When a message cannot be delivered, it is normally returned to the sender in a
660 delivery failure message or a &"non-delivery report"& (NDR). The term
661 &'bounce'& is commonly used for this action, and the error reports are often
662 called &'bounce messages'&. This is a convenient shorthand for &"delivery
663 failure error report"&. Such messages have an empty sender address in the
664 message's &'envelope'& (see below) to ensure that they cannot themselves give
665 rise to further bounce messages.
666
667 The term &'default'& appears frequently in this manual. It is used to qualify a
668 value which is used in the absence of any setting in the configuration. It may
669 also qualify an action which is taken unless a configuration setting specifies
670 otherwise.
671
672 The term &'defer'& is used when the delivery of a message to a specific
673 destination cannot immediately take place for some reason (a remote host may be
674 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
675 until a later time.
676
677 The word &'domain'& is sometimes used to mean all but the first component of a
678 host's name. It is &'not'& used in that sense here, where it normally refers to
679 the part of an email address following the @ sign.
680
681 .cindex "envelope, definition of"
682 .cindex "sender" "definition of"
683 A message in transit has an associated &'envelope'&, as well as a header and a
684 body. The envelope contains a sender address (to which bounce messages should
685 be delivered), and any number of recipient addresses. References to the
686 sender or the recipients of a message usually mean the addresses in the
687 envelope. An MTA uses these addresses for delivery, and for returning bounce
688 messages, not the addresses that appear in the header lines.
689
690 .cindex "message" "header, definition of"
691 .cindex "header section" "definition of"
692 The &'header'& of a message is the first part of a message's text, consisting
693 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
694 &'Subject:'&, etc. Long header lines can be split over several text lines by
695 indenting the continuations. The header is separated from the body by a blank
696 line.
697
698 .cindex "local part" "definition of"
699 .cindex "domain" "definition of"
700 The term &'local part'&, which is taken from RFC 2822, is used to refer to that
701 part of an email address that precedes the @ sign. The part that follows the
702 @ sign is called the &'domain'& or &'mail domain'&.
703
704 .cindex "local delivery" "definition of"
705 .cindex "remote delivery, definition of"
706 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
707 delivery to a file or a pipe on the local host from delivery by SMTP over
708 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
709 host it is running on are &'remote'&.
710
711 .cindex "return path" "definition of"
712 &'Return path'& is another name that is used for the sender address in a
713 message's envelope.
714
715 .cindex "queue" "definition of"
716 The term &'queue'& is used to refer to the set of messages awaiting delivery,
717 because this term is in widespread use in the context of MTAs. However, in
718 Exim's case the reality is more like a pool than a queue, because there is
719 normally no ordering of waiting messages.
720
721 .cindex "queue runner" "definition of"
722 The term &'queue runner'& is used to describe a process that scans the queue
723 and attempts to deliver those messages whose retry times have come. This term
724 is used by other MTAs, and also relates to the command &%runq%&, but in Exim
725 the waiting messages are normally processed in an unpredictable order.
726
727 .cindex "spool directory" "definition of"
728 The term &'spool directory'& is used for a directory in which Exim keeps the
729 messages on its queue &-- that is, those that it is in the process of
730 delivering. This should not be confused with the directory in which local
731 mailboxes are stored, which is called a &"spool directory"& by some people. In
732 the Exim documentation, &"spool"& is always used in the first sense.
733
734
735
736
737
738
739 . ////////////////////////////////////////////////////////////////////////////
740 . ////////////////////////////////////////////////////////////////////////////
741
742 .chapter "Incorporated code" "CHID2"
743 .cindex "incorporated code"
744 .cindex "regular expressions" "library"
745 .cindex "PCRE"
746 .cindex "OpenDMARC"
747 A number of pieces of external code are included in the Exim distribution.
748
749 .ilist
750 Regular expressions are supported in the main Exim program and in the
751 Exim monitor using the freely-distributable PCRE library, copyright
752 &copy; University of Cambridge. The source to PCRE is no longer shipped with
753 Exim, so you will need to use the version of PCRE shipped with your system,
754 or obtain and install the full version of the library from
755 &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
756 .next
757 .cindex "cdb" "acknowledgment"
758 Support for the cdb (Constant DataBase) lookup method is provided by code
759 contributed by Nigel Metheringham of (at the time he contributed it) Planet
760 Online Ltd. The implementation is completely contained within the code of Exim.
761 It does not link against an external cdb library. The code contains the
762 following statements:
763
764 .blockquote
765 Copyright &copy; 1998 Nigel Metheringham, Planet Online Ltd
766
767 This program is free software; you can redistribute it and/or modify it under
768 the terms of the GNU General Public License as published by the Free Software
769 Foundation; either version 2 of the License, or (at your option) any later
770 version.
771 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
772 the spec and sample code for cdb can be obtained from
773 &url(http://www.pobox.com/~djb/cdb.html). This implementation borrows
774 some code from Dan Bernstein's implementation (which has no license
775 restrictions applied to it).
776 .endblockquote
777 .next
778 .cindex "SPA authentication"
779 .cindex "Samba project"
780 .cindex "Microsoft Secure Password Authentication"
781 Client support for Microsoft's &'Secure Password Authentication'& is provided
782 by code contributed by Marc Prud'hommeaux. Server support was contributed by
783 Tom Kistner. This includes code taken from the Samba project, which is released
784 under the Gnu GPL.
785 .next
786 .cindex "Cyrus"
787 .cindex "&'pwcheck'& daemon"
788 .cindex "&'pwauthd'& daemon"
789 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
790 by code taken from the Cyrus-SASL library and adapted by Alexander S.
791 Sabourenkov. The permission notice appears below, in accordance with the
792 conditions expressed therein.
793
794 .blockquote
795 Copyright &copy; 2001 Carnegie Mellon University. All rights reserved.
796
797 Redistribution and use in source and binary forms, with or without
798 modification, are permitted provided that the following conditions
799 are met:
800
801 .olist
802 Redistributions of source code must retain the above copyright
803 notice, this list of conditions and the following disclaimer.
804 .next
805 Redistributions in binary form must reproduce the above copyright
806 notice, this list of conditions and the following disclaimer in
807 the documentation and/or other materials provided with the
808 distribution.
809 .next
810 The name &"Carnegie Mellon University"& must not be used to
811 endorse or promote products derived from this software without
812 prior written permission. For permission or any other legal
813 details, please contact
814 .display
815 Office of Technology Transfer
816 Carnegie Mellon University
817 5000 Forbes Avenue
818 Pittsburgh, PA 15213-3890
819 (412) 268-4387, fax: (412) 268-7395
820 tech-transfer@andrew.cmu.edu
821 .endd
822 .next
823 Redistributions of any form whatsoever must retain the following
824 acknowledgment:
825
826 &"This product includes software developed by Computing Services
827 at Carnegie Mellon University (&url(http://www.cmu.edu/computing/)."&
828
829 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
830 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
831 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
832 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
833 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
834 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
835 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
836 .endlist
837 .endblockquote
838
839 .next
840 .cindex "Exim monitor" "acknowledgment"
841 .cindex "X-windows"
842 .cindex "Athena"
843 The Exim Monitor program, which is an X-Window application, includes
844 modified versions of the Athena StripChart and TextPop widgets.
845 This code is copyright by DEC and MIT, and their permission notice appears
846 below, in accordance with the conditions expressed therein.
847
848 .blockquote
849 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
850 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
851
852 All Rights Reserved
853
854 Permission to use, copy, modify, and distribute this software and its
855 documentation for any purpose and without fee is hereby granted,
856 provided that the above copyright notice appear in all copies and that
857 both that copyright notice and this permission notice appear in
858 supporting documentation, and that the names of Digital or MIT not be
859 used in advertising or publicity pertaining to distribution of the
860 software without specific, written prior permission.
861
862 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
863 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
864 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
865 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
866 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
867 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
868 SOFTWARE.
869 .endblockquote
870
871 .next
872 .cindex "opendmarc" "acknowledgment"
873 The DMARC implementation uses the OpenDMARC library which is Copyrighted by
874 The Trusted Domain Project. Portions of Exim source which use OpenDMARC
875 derived code are indicated in the respective source files. The full OpenDMARC
876 license is provided in the LICENSE.opendmarc file contained in the distributed
877 source code.
878
879 .next
880 Many people have contributed code fragments, some large, some small, that were
881 not covered by any specific licence requirements. It is assumed that the
882 contributors are happy to see their code incorporated into Exim under the GPL.
883 .endlist
884
885
886
887
888
889 . ////////////////////////////////////////////////////////////////////////////
890 . ////////////////////////////////////////////////////////////////////////////
891
892 .chapter "How Exim receives and delivers mail" "CHID11" &&&
893 "Receiving and delivering mail"
894
895
896 .section "Overall philosophy" "SECID10"
897 .cindex "design philosophy"
898 Exim is designed to work efficiently on systems that are permanently connected
899 to the Internet and are handling a general mix of mail. In such circumstances,
900 most messages can be delivered immediately. Consequently, Exim does not
901 maintain independent queues of messages for specific domains or hosts, though
902 it does try to send several messages in a single SMTP connection after a host
903 has been down, and it also maintains per-host retry information.
904
905
906 .section "Policy control" "SECID11"
907 .cindex "policy control" "overview"
908 Policy controls are now an important feature of MTAs that are connected to the
909 Internet. Perhaps their most important job is to stop MTAs being abused as
910 &"open relays"& by misguided individuals who send out vast amounts of
911 unsolicited junk, and want to disguise its source. Exim provides flexible
912 facilities for specifying policy controls on incoming mail:
913
914 .ilist
915 .cindex "&ACL;" "introduction"
916 Exim 4 (unlike previous versions of Exim) implements policy controls on
917 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
918 series of statements that may either grant or deny access. ACLs can be used at
919 several places in the SMTP dialogue while receiving a message from a remote
920 host. However, the most common places are after each RCPT command, and at the
921 very end of the message. The sysadmin can specify conditions for accepting or
922 rejecting individual recipients or the entire message, respectively, at these
923 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
924 error code.
925 .next
926 An ACL is also available for locally generated, non-SMTP messages. In this
927 case, the only available actions are to accept or deny the entire message.
928 .next
929 When Exim is compiled with the content-scanning extension, facilities are
930 provided in the ACL mechanism for passing the message to external virus and/or
931 spam scanning software. The result of such a scan is passed back to the ACL,
932 which can then use it to decide what to do with the message.
933 .next
934 When a message has been received, either from a remote host or from the local
935 host, but before the final acknowledgment has been sent, a locally supplied C
936 function called &[local_scan()]& can be run to inspect the message and decide
937 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
938 is accepted, the list of recipients can be modified by the function.
939 .next
940 Using the &[local_scan()]& mechanism is another way of calling external scanner
941 software. The &%SA-Exim%& add-on package works this way. It does not require
942 Exim to be compiled with the content-scanning extension.
943 .next
944 After a message has been accepted, a further checking mechanism is available in
945 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
946 runs at the start of every delivery process.
947 .endlist
948
949
950
951 .section "User filters" "SECID12"
952 .cindex "filter" "introduction"
953 .cindex "Sieve filter"
954 In a conventional Exim configuration, users are able to run private filters by
955 setting up appropriate &_.forward_& files in their home directories. See
956 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
957 configuration needed to support this, and the separate document entitled
958 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
959 of filtering are available:
960
961 .ilist
962 Sieve filters are written in the standard filtering language that is defined
963 by RFC 3028.
964 .next
965 Exim filters are written in a syntax that is unique to Exim, but which is more
966 powerful than Sieve, which it pre-dates.
967 .endlist
968
969 User filters are run as part of the routing process, described below.
970
971
972
973 .section "Message identification" "SECTmessiden"
974 .cindex "message ids" "details of format"
975 .cindex "format" "of message id"
976 .cindex "id of message"
977 .cindex "base62"
978 .cindex "base36"
979 .cindex "Darwin"
980 .cindex "Cygwin"
981 Every message handled by Exim is given a &'message id'& which is sixteen
982 characters long. It is divided into three parts, separated by hyphens, for
983 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
984 normally encoding numbers in base 62. However, in the Darwin operating
985 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
986 (avoiding the use of lower case letters) is used instead, because the message
987 id is used to construct file names, and the names of files in those systems are
988 not always case-sensitive.
989
990 .cindex "pid (process id)" "re-use of"
991 The detail of the contents of the message id have changed as Exim has evolved.
992 Earlier versions relied on the operating system not re-using a process id (pid)
993 within one second. On modern operating systems, this assumption can no longer
994 be made, so the algorithm had to be changed. To retain backward compatibility,
995 the format of the message id was retained, which is why the following rules are
996 somewhat eccentric:
997
998 .ilist
999 The first six characters of the message id are the time at which the message
1000 started to be received, to a granularity of one second. That is, this field
1001 contains the number of seconds since the start of the epoch (the normal Unix
1002 way of representing the date and time of day).
1003 .next
1004 After the first hyphen, the next six characters are the id of the process that
1005 received the message.
1006 .next
1007 There are two different possibilities for the final two characters:
1008 .olist
1009 .oindex "&%localhost_number%&"
1010 If &%localhost_number%& is not set, this value is the fractional part of the
1011 time of reception, normally in units of 1/2000 of a second, but for systems
1012 that must use base 36 instead of base 62 (because of case-insensitive file
1013 systems), the units are 1/1000 of a second.
1014 .next
1015 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
1016 the fractional part of the time, which in this case is in units of 1/200
1017 (1/100) of a second.
1018 .endlist
1019 .endlist
1020
1021 After a message has been received, Exim waits for the clock to tick at the
1022 appropriate resolution before proceeding, so that if another message is
1023 received by the same process, or by another process with the same (re-used)
1024 pid, it is guaranteed that the time will be different. In most cases, the clock
1025 will already have ticked while the message was being received.
1026
1027
1028 .section "Receiving mail" "SECID13"
1029 .cindex "receiving mail"
1030 .cindex "message" "reception"
1031 The only way Exim can receive mail from another host is using SMTP over
1032 TCP/IP, in which case the sender and recipient addresses are transferred using
1033 SMTP commands. However, from a locally running process (such as a user's MUA),
1034 there are several possibilities:
1035
1036 .ilist
1037 If the process runs Exim with the &%-bm%& option, the message is read
1038 non-interactively (usually via a pipe), with the recipients taken from the
1039 command line, or from the body of the message if &%-t%& is also used.
1040 .next
1041 If the process runs Exim with the &%-bS%& option, the message is also read
1042 non-interactively, but in this case the recipients are listed at the start of
1043 the message in a series of SMTP RCPT commands, terminated by a DATA
1044 command. This is so-called &"batch SMTP"& format,
1045 but it isn't really SMTP. The SMTP commands are just another way of passing
1046 envelope addresses in a non-interactive submission.
1047 .next
1048 If the process runs Exim with the &%-bs%& option, the message is read
1049 interactively, using the SMTP protocol. A two-way pipe is normally used for
1050 passing data between the local process and the Exim process.
1051 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1052 example, the ACLs for SMTP commands are used for this form of submission.
1053 .next
1054 A local process may also make a TCP/IP call to the host's loopback address
1055 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1056 does not treat the loopback address specially. It treats all such connections
1057 in the same way as connections from other hosts.
1058 .endlist
1059
1060
1061 .cindex "message sender, constructed by Exim"
1062 .cindex "sender" "constructed by Exim"
1063 In the three cases that do not involve TCP/IP, the sender address is
1064 constructed from the login name of the user that called Exim and a default
1065 qualification domain (which can be set by the &%qualify_domain%& configuration
1066 option). For local or batch SMTP, a sender address that is passed using the
1067 SMTP MAIL command is ignored. However, the system administrator may allow
1068 certain users (&"trusted users"&) to specify a different sender address
1069 unconditionally, or all users to specify certain forms of different sender
1070 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1071 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1072 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1073 users to change sender addresses.
1074
1075 Messages received by either of the non-interactive mechanisms are subject to
1076 checking by the non-SMTP ACL, if one is defined. Messages received using SMTP
1077 (either over TCP/IP, or interacting with a local process) can be checked by a
1078 number of ACLs that operate at different times during the SMTP session. Either
1079 individual recipients, or the entire message, can be rejected if local policy
1080 requirements are not met. The &[local_scan()]& function (see chapter
1081 &<<CHAPlocalscan>>&) is run for all incoming messages.
1082
1083 Exim can be configured not to start a delivery process when a message is
1084 received; this can be unconditional, or depend on the number of incoming SMTP
1085 connections or the system load. In these situations, new messages wait on the
1086 queue until a queue runner process picks them up. However, in standard
1087 configurations under normal conditions, delivery is started as soon as a
1088 message is received.
1089
1090
1091
1092
1093
1094 .section "Handling an incoming message" "SECID14"
1095 .cindex "spool directory" "files that hold a message"
1096 .cindex "file" "how a message is held"
1097 When Exim accepts a message, it writes two files in its spool directory. The
1098 first contains the envelope information, the current status of the message, and
1099 the header lines, and the second contains the body of the message. The names of
1100 the two spool files consist of the message id, followed by &`-H`& for the
1101 file containing the envelope and header, and &`-D`& for the data file.
1102
1103 .cindex "spool directory" "&_input_& sub-directory"
1104 By default all these message files are held in a single directory called
1105 &_input_& inside the general Exim spool directory. Some operating systems do
1106 not perform very well if the number of files in a directory gets large; to
1107 improve performance in such cases, the &%split_spool_directory%& option can be
1108 used. This causes Exim to split up the input files into 62 sub-directories
1109 whose names are single letters or digits. When this is done, the queue is
1110 processed one sub-directory at a time instead of all at once, which can improve
1111 overall performance even when there are not enough files in each directory to
1112 affect file system performance.
1113
1114 The envelope information consists of the address of the message's sender and
1115 the addresses of the recipients. This information is entirely separate from
1116 any addresses contained in the header lines. The status of the message includes
1117 a list of recipients who have already received the message. The format of the
1118 first spool file is described in chapter &<<CHAPspool>>&.
1119
1120 .cindex "rewriting" "addresses"
1121 Address rewriting that is specified in the rewrite section of the configuration
1122 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1123 both in the header lines and the envelope, at the time the message is accepted.
1124 If during the course of delivery additional addresses are generated (for
1125 example, via aliasing), these new addresses are rewritten as soon as they are
1126 generated. At the time a message is actually delivered (transported) further
1127 rewriting can take place; because this is a transport option, it can be
1128 different for different forms of delivery. It is also possible to specify the
1129 addition or removal of certain header lines at the time the message is
1130 delivered (see chapters &<<CHAProutergeneric>>& and
1131 &<<CHAPtransportgeneric>>&).
1132
1133
1134
1135 .section "Life of a message" "SECID15"
1136 .cindex "message" "life of"
1137 .cindex "message" "frozen"
1138 A message remains in the spool directory until it is completely delivered to
1139 its recipients or to an error address, or until it is deleted by an
1140 administrator or by the user who originally created it. In cases when delivery
1141 cannot proceed &-- for example, when a message can neither be delivered to its
1142 recipients nor returned to its sender, the message is marked &"frozen"& on the
1143 spool, and no more deliveries are attempted.
1144
1145 .cindex "frozen messages" "thawing"
1146 .cindex "message" "thawing frozen"
1147 An administrator can &"thaw"& such messages when the problem has been
1148 corrected, and can also freeze individual messages by hand if necessary. In
1149 addition, an administrator can force a delivery error, causing a bounce message
1150 to be sent.
1151
1152 .oindex "&%timeout_frozen_after%&"
1153 .oindex "&%ignore_bounce_errors_after%&"
1154 There are options called &%ignore_bounce_errors_after%& and
1155 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1156 The first applies only to frozen bounces, the second to any frozen messages.
1157
1158 .cindex "message" "log file for"
1159 .cindex "log" "file for each message"
1160 While Exim is working on a message, it writes information about each delivery
1161 attempt to its main log file. This includes successful, unsuccessful, and
1162 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1163 lines are also written to a separate &'message log'& file for each message.
1164 These logs are solely for the benefit of the administrator, and are normally
1165 deleted along with the spool files when processing of a message is complete.
1166 The use of individual message logs can be disabled by setting
1167 &%no_message_logs%&; this might give an improvement in performance on very busy
1168 systems.
1169
1170 .cindex "journal file"
1171 .cindex "file" "journal"
1172 All the information Exim itself needs to set up a delivery is kept in the first
1173 spool file, along with the header lines. When a successful delivery occurs, the
1174 address is immediately written at the end of a journal file, whose name is the
1175 message id followed by &`-J`&. At the end of a delivery run, if there are some
1176 addresses left to be tried again later, the first spool file (the &`-H`& file)
1177 is updated to indicate which these are, and the journal file is then deleted.
1178 Updating the spool file is done by writing a new file and renaming it, to
1179 minimize the possibility of data loss.
1180
1181 Should the system or the program crash after a successful delivery but before
1182 the spool file has been updated, the journal is left lying around. The next
1183 time Exim attempts to deliver the message, it reads the journal file and
1184 updates the spool file before proceeding. This minimizes the chances of double
1185 deliveries caused by crashes.
1186
1187
1188
1189 .section "Processing an address for delivery" "SECTprocaddress"
1190 .cindex "drivers" "definition of"
1191 .cindex "router" "definition of"
1192 .cindex "transport" "definition of"
1193 The main delivery processing elements of Exim are called &'routers'& and
1194 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1195 number of them is provided in the source distribution, and compile-time options
1196 specify which ones are included in the binary. Run time options specify which
1197 ones are actually used for delivering messages.
1198
1199 .cindex "drivers" "instance definition"
1200 Each driver that is specified in the run time configuration is an &'instance'&
1201 of that particular driver type. Multiple instances are allowed; for example,
1202 you can set up several different &(smtp)& transports, each with different
1203 option values that might specify different ports or different timeouts. Each
1204 instance has its own identifying name. In what follows we will normally use the
1205 instance name when discussing one particular instance (that is, one specific
1206 configuration of the driver), and the generic driver name when discussing
1207 the driver's features in general.
1208
1209 A &'router'& is a driver that operates on an address, either determining how
1210 its delivery should happen, by assigning it to a specific transport, or
1211 converting the address into one or more new addresses (for example, via an
1212 alias file). A router may also explicitly choose to fail an address, causing it
1213 to be bounced.
1214
1215 A &'transport'& is a driver that transmits a copy of the message from Exim's
1216 spool to some destination. There are two kinds of transport: for a &'local'&
1217 transport, the destination is a file or a pipe on the local host, whereas for a
1218 &'remote'& transport the destination is some other host. A message is passed
1219 to a specific transport as a result of successful routing. If a message has
1220 several recipients, it may be passed to a number of different transports.
1221
1222 .cindex "preconditions" "definition of"
1223 An address is processed by passing it to each configured router instance in
1224 turn, subject to certain preconditions, until a router accepts the address or
1225 specifies that it should be bounced. We will describe this process in more
1226 detail shortly. First, as a simple example, we consider how each recipient
1227 address in a message is processed in a small configuration of three routers.
1228
1229 To make this a more concrete example, it is described in terms of some actual
1230 routers, but remember, this is only an example. You can configure Exim's
1231 routers in many different ways, and there may be any number of routers in a
1232 configuration.
1233
1234 The first router that is specified in a configuration is often one that handles
1235 addresses in domains that are not recognized specially by the local host. These
1236 are typically addresses for arbitrary domains on the Internet. A precondition
1237 is set up which looks for the special domains known to the host (for example,
1238 its own domain name), and the router is run for addresses that do &'not'&
1239 match. Typically, this is a router that looks up domains in the DNS in order to
1240 find the hosts to which this address routes. If it succeeds, the address is
1241 assigned to a suitable SMTP transport; if it does not succeed, the router is
1242 configured to fail the address.
1243
1244 The second router is reached only when the domain is recognized as one that
1245 &"belongs"& to the local host. This router does redirection &-- also known as
1246 aliasing and forwarding. When it generates one or more new addresses from the
1247 original, each of them is routed independently from the start. Otherwise, the
1248 router may cause an address to fail, or it may simply decline to handle the
1249 address, in which case the address is passed to the next router.
1250
1251 The final router in many configurations is one that checks to see if the
1252 address belongs to a local mailbox. The precondition may involve a check to
1253 see if the local part is the name of a login account, or it may look up the
1254 local part in a file or a database. If its preconditions are not met, or if
1255 the router declines, we have reached the end of the routers. When this happens,
1256 the address is bounced.
1257
1258
1259
1260 .section "Processing an address for verification" "SECID16"
1261 .cindex "router" "for verification"
1262 .cindex "verifying address" "overview"
1263 As well as being used to decide how to deliver to an address, Exim's routers
1264 are also used for &'address verification'&. Verification can be requested as
1265 one of the checks to be performed in an ACL for incoming messages, on both
1266 sender and recipient addresses, and it can be tested using the &%-bv%& and
1267 &%-bvs%& command line options.
1268
1269 When an address is being verified, the routers are run in &"verify mode"&. This
1270 does not affect the way the routers work, but it is a state that can be
1271 detected. By this means, a router can be skipped or made to behave differently
1272 when verifying. A common example is a configuration in which the first router
1273 sends all messages to a message-scanning program, unless they have been
1274 previously scanned. Thus, the first router accepts all addresses without any
1275 checking, making it useless for verifying. Normally, the &%no_verify%& option
1276 would be set for such a router, causing it to be skipped in verify mode.
1277
1278
1279
1280
1281 .section "Running an individual router" "SECTrunindrou"
1282 .cindex "router" "running details"
1283 .cindex "preconditions" "checking"
1284 .cindex "router" "result of running"
1285 As explained in the example above, a number of preconditions are checked before
1286 running a router. If any are not met, the router is skipped, and the address is
1287 passed to the next router. When all the preconditions on a router &'are'& met,
1288 the router is run. What happens next depends on the outcome, which is one of
1289 the following:
1290
1291 .ilist
1292 &'accept'&: The router accepts the address, and either assigns it to a
1293 transport, or generates one or more &"child"& addresses. Processing the
1294 original address ceases,
1295 .oindex "&%unseen%&"
1296 unless the &%unseen%& option is set on the router. This option
1297 can be used to set up multiple deliveries with different routing (for example,
1298 for keeping archive copies of messages). When &%unseen%& is set, the address is
1299 passed to the next router. Normally, however, an &'accept'& return marks the
1300 end of routing.
1301
1302 Any child addresses generated by the router are processed independently,
1303 starting with the first router by default. It is possible to change this by
1304 setting the &%redirect_router%& option to specify which router to start at for
1305 child addresses. Unlike &%pass_router%& (see below) the router specified by
1306 &%redirect_router%& may be anywhere in the router configuration.
1307 .next
1308 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1309 requests that the address be passed to another router. By default the address
1310 is passed to the next router, but this can be changed by setting the
1311 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1312 must be below the current router (to avoid loops).
1313 .next
1314 &'decline'&: The router declines to accept the address because it does not
1315 recognize it at all. By default, the address is passed to the next router, but
1316 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1317 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1318 &'decline'& into &'fail'&.
1319 .next
1320 &'fail'&: The router determines that the address should fail, and queues it for
1321 the generation of a bounce message. There is no further processing of the
1322 original address unless &%unseen%& is set on the router.
1323 .next
1324 &'defer'&: The router cannot handle the address at the present time. (A
1325 database may be offline, or a DNS lookup may have timed out.) No further
1326 processing of the address happens in this delivery attempt. It is tried again
1327 next time the message is considered for delivery.
1328 .next
1329 &'error'&: There is some error in the router (for example, a syntax error in
1330 its configuration). The action is as for defer.
1331 .endlist
1332
1333 If an address reaches the end of the routers without having been accepted by
1334 any of them, it is bounced as unrouteable. The default error message in this
1335 situation is &"unrouteable address"&, but you can set your own message by
1336 making use of the &%cannot_route_message%& option. This can be set for any
1337 router; the value from the last router that &"saw"& the address is used.
1338
1339 Sometimes while routing you want to fail a delivery when some conditions are
1340 met but others are not, instead of passing the address on for further routing.
1341 You can do this by having a second router that explicitly fails the delivery
1342 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1343 facility for this purpose.
1344
1345
1346 .section "Duplicate addresses" "SECID17"
1347 .cindex "case of local parts"
1348 .cindex "address duplicate, discarding"
1349 .cindex "duplicate addresses"
1350 Once routing is complete, Exim scans the addresses that are assigned to local
1351 and remote transports, and discards any duplicates that it finds. During this
1352 check, local parts are treated as case-sensitive. This happens only when
1353 actually delivering a message; when testing routers with &%-bt%&, all the
1354 routed addresses are shown.
1355
1356
1357
1358 .section "Router preconditions" "SECTrouprecon"
1359 .cindex "router" "preconditions, order of processing"
1360 .cindex "preconditions" "order of processing"
1361 The preconditions that are tested for each router are listed below, in the
1362 order in which they are tested. The individual configuration options are
1363 described in more detail in chapter &<<CHAProutergeneric>>&.
1364
1365 .ilist
1366 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1367 the local parts handled by the router may or must have certain prefixes and/or
1368 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1369 skipped. These conditions are tested first. When an affix is present, it is
1370 removed from the local part before further processing, including the evaluation
1371 of any other conditions.
1372 .next
1373 Routers can be designated for use only when not verifying an address, that is,
1374 only when routing it for delivery (or testing its delivery routing). If the
1375 &%verify%& option is set false, the router is skipped when Exim is verifying an
1376 address.
1377 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1378 &%verify_recipient%&, which independently control the use of the router for
1379 sender and recipient verification. You can set these options directly if
1380 you want a router to be used for only one type of verification.
1381 Note that cutthrough delivery is classed as a recipient verification for this purpose.
1382 .next
1383 If the &%address_test%& option is set false, the router is skipped when Exim is
1384 run with the &%-bt%& option to test an address routing. This can be helpful
1385 when the first router sends all new messages to a scanner of some sort; it
1386 makes it possible to use &%-bt%& to test subsequent delivery routing without
1387 having to simulate the effect of the scanner.
1388 .next
1389 Routers can be designated for use only when verifying an address, as
1390 opposed to routing it for delivery. The &%verify_only%& option controls this.
1391 Again, cutthrough delivery counts as a verification.
1392 .next
1393 Individual routers can be explicitly skipped when running the routers to
1394 check an address given in the SMTP EXPN command (see the &%expn%& option).
1395 .next
1396 If the &%domains%& option is set, the domain of the address must be in the set
1397 of domains that it defines.
1398 .next
1399 .vindex "&$local_part_prefix$&"
1400 .vindex "&$local_part$&"
1401 .vindex "&$local_part_suffix$&"
1402 If the &%local_parts%& option is set, the local part of the address must be in
1403 the set of local parts that it defines. If &%local_part_prefix%& or
1404 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1405 part before this check. If you want to do precondition tests on local parts
1406 that include affixes, you can do so by using a &%condition%& option (see below)
1407 that uses the variables &$local_part$&, &$local_part_prefix$&, and
1408 &$local_part_suffix$& as necessary.
1409 .next
1410 .vindex "&$local_user_uid$&"
1411 .vindex "&$local_user_gid$&"
1412 .vindex "&$home$&"
1413 If the &%check_local_user%& option is set, the local part must be the name of
1414 an account on the local host. If this check succeeds, the uid and gid of the
1415 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1416 user's home directory is placed in &$home$&; these values can be used in the
1417 remaining preconditions.
1418 .next
1419 If the &%router_home_directory%& option is set, it is expanded at this point,
1420 because it overrides the value of &$home$&. If this expansion were left till
1421 later, the value of &$home$& as set by &%check_local_user%& would be used in
1422 subsequent tests. Having two different values of &$home$& in the same router
1423 could lead to confusion.
1424 .next
1425 If the &%senders%& option is set, the envelope sender address must be in the
1426 set of addresses that it defines.
1427 .next
1428 If the &%require_files%& option is set, the existence or non-existence of
1429 specified files is tested.
1430 .next
1431 .cindex "customizing" "precondition"
1432 If the &%condition%& option is set, it is evaluated and tested. This option
1433 uses an expanded string to allow you to set up your own custom preconditions.
1434 Expanded strings are described in chapter &<<CHAPexpand>>&.
1435 .endlist
1436
1437
1438 Note that &%require_files%& comes near the end of the list, so you cannot use
1439 it to check for the existence of a file in which to lookup up a domain, local
1440 part, or sender. However, as these options are all expanded, you can use the
1441 &%exists%& expansion condition to make such tests within each condition. The
1442 &%require_files%& option is intended for checking files that the router may be
1443 going to use internally, or which are needed by a specific transport (for
1444 example, &_.procmailrc_&).
1445
1446
1447
1448 .section "Delivery in detail" "SECID18"
1449 .cindex "delivery" "in detail"
1450 When a message is to be delivered, the sequence of events is as follows:
1451
1452 .ilist
1453 If a system-wide filter file is specified, the message is passed to it. The
1454 filter may add recipients to the message, replace the recipients, discard the
1455 message, cause a new message to be generated, or cause the message delivery to
1456 fail. The format of the system filter file is the same as for Exim user filter
1457 files, described in the separate document entitled &'Exim's interfaces to mail
1458 filtering'&.
1459 .cindex "Sieve filter" "not available for system filter"
1460 (&*Note*&: Sieve cannot be used for system filter files.)
1461
1462 Some additional features are available in system filters &-- see chapter
1463 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1464 filter only once per delivery attempt, however many recipients it has. However,
1465 if there are several delivery attempts because one or more addresses could not
1466 be immediately delivered, the system filter is run each time. The filter
1467 condition &%first_delivery%& can be used to detect the first run of the system
1468 filter.
1469 .next
1470 Each recipient address is offered to each configured router in turn, subject to
1471 its preconditions, until one is able to handle it. If no router can handle the
1472 address, that is, if they all decline, the address is failed. Because routers
1473 can be targeted at particular domains, several locally handled domains can be
1474 processed entirely independently of each other.
1475 .next
1476 .cindex "routing" "loops in"
1477 .cindex "loop" "while routing"
1478 A router that accepts an address may assign it to a local or a remote
1479 transport. However, the transport is not run at this time. Instead, the address
1480 is placed on a list for the particular transport, which will be run later.
1481 Alternatively, the router may generate one or more new addresses (typically
1482 from alias, forward, or filter files). New addresses are fed back into this
1483 process from the top, but in order to avoid loops, a router ignores any address
1484 which has an identically-named ancestor that was processed by itself.
1485 .next
1486 When all the routing has been done, addresses that have been successfully
1487 handled are passed to their assigned transports. When local transports are
1488 doing real local deliveries, they handle only one address at a time, but if a
1489 local transport is being used as a pseudo-remote transport (for example, to
1490 collect batched SMTP messages for transmission by some other means) multiple
1491 addresses can be handled. Remote transports can always handle more than one
1492 address at a time, but can be configured not to do so, or to restrict multiple
1493 addresses to the same domain.
1494 .next
1495 Each local delivery to a file or a pipe runs in a separate process under a
1496 non-privileged uid, and these deliveries are run one at a time. Remote
1497 deliveries also run in separate processes, normally under a uid that is private
1498 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1499 run in parallel. The maximum number of simultaneous remote deliveries for any
1500 one message is set by the &%remote_max_parallel%& option.
1501 The order in which deliveries are done is not defined, except that all local
1502 deliveries happen before any remote deliveries.
1503 .next
1504 .cindex "queue runner"
1505 When it encounters a local delivery during a queue run, Exim checks its retry
1506 database to see if there has been a previous temporary delivery failure for the
1507 address before running the local transport. If there was a previous failure,
1508 Exim does not attempt a new delivery until the retry time for the address is
1509 reached. However, this happens only for delivery attempts that are part of a
1510 queue run. Local deliveries are always attempted when delivery immediately
1511 follows message reception, even if retry times are set for them. This makes for
1512 better behaviour if one particular message is causing problems (for example,
1513 causing quota overflow, or provoking an error in a filter file).
1514 .next
1515 .cindex "delivery" "retry in remote transports"
1516 Remote transports do their own retry handling, since an address may be
1517 deliverable to one of a number of hosts, each of which may have a different
1518 retry time. If there have been previous temporary failures and no host has
1519 reached its retry time, no delivery is attempted, whether in a queue run or
1520 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1521 .next
1522 If there were any permanent errors, a bounce message is returned to an
1523 appropriate address (the sender in the common case), with details of the error
1524 for each failing address. Exim can be configured to send copies of bounce
1525 messages to other addresses.
1526 .next
1527 .cindex "delivery" "deferral"
1528 If one or more addresses suffered a temporary failure, the message is left on
1529 the queue, to be tried again later. Delivery of these addresses is said to be
1530 &'deferred'&.
1531 .next
1532 When all the recipient addresses have either been delivered or bounced,
1533 handling of the message is complete. The spool files and message log are
1534 deleted, though the message log can optionally be preserved if required.
1535 .endlist
1536
1537
1538
1539
1540 .section "Retry mechanism" "SECID19"
1541 .cindex "delivery" "retry mechanism"
1542 .cindex "retry" "description of mechanism"
1543 .cindex "queue runner"
1544 Exim's mechanism for retrying messages that fail to get delivered at the first
1545 attempt is the queue runner process. You must either run an Exim daemon that
1546 uses the &%-q%& option with a time interval to start queue runners at regular
1547 intervals, or use some other means (such as &'cron'&) to start them. If you do
1548 not arrange for queue runners to be run, messages that fail temporarily at the
1549 first attempt will remain on your queue for ever. A queue runner process works
1550 its way through the queue, one message at a time, trying each delivery that has
1551 passed its retry time.
1552 You can run several queue runners at once.
1553
1554 Exim uses a set of configured rules to determine when next to retry the failing
1555 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1556 should give up trying to deliver to the address, at which point it generates a
1557 bounce message. If no retry rules are set for a particular host, address, and
1558 error combination, no retries are attempted, and temporary errors are treated
1559 as permanent.
1560
1561
1562
1563 .section "Temporary delivery failure" "SECID20"
1564 .cindex "delivery" "temporary failure"
1565 There are many reasons why a message may not be immediately deliverable to a
1566 particular address. Failure to connect to a remote machine (because it, or the
1567 connection to it, is down) is one of the most common. Temporary failures may be
1568 detected during routing as well as during the transport stage of delivery.
1569 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1570 is on a file system where the user is over quota. Exim can be configured to
1571 impose its own quotas on local mailboxes; where system quotas are set they will
1572 also apply.
1573
1574 If a host is unreachable for a period of time, a number of messages may be
1575 waiting for it by the time it recovers, and sending them in a single SMTP
1576 connection is clearly beneficial. Whenever a delivery to a remote host is
1577 deferred,
1578 .cindex "hints database"
1579 Exim makes a note in its hints database, and whenever a successful
1580 SMTP delivery has happened, it looks to see if any other messages are waiting
1581 for the same host. If any are found, they are sent over the same SMTP
1582 connection, subject to a configuration limit as to the maximum number in any
1583 one connection.
1584
1585
1586
1587 .section "Permanent delivery failure" "SECID21"
1588 .cindex "delivery" "permanent failure"
1589 .cindex "bounce message" "when generated"
1590 When a message cannot be delivered to some or all of its intended recipients, a
1591 bounce message is generated. Temporary delivery failures turn into permanent
1592 errors when their timeout expires. All the addresses that fail in a given
1593 delivery attempt are listed in a single message. If the original message has
1594 many recipients, it is possible for some addresses to fail in one delivery
1595 attempt and others to fail subsequently, giving rise to more than one bounce
1596 message. The wording of bounce messages can be customized by the administrator.
1597 See chapter &<<CHAPemsgcust>>& for details.
1598
1599 .cindex "&'X-Failed-Recipients:'& header line"
1600 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1601 failed addresses, for the benefit of programs that try to analyse such messages
1602 automatically.
1603
1604 .cindex "bounce message" "recipient of"
1605 A bounce message is normally sent to the sender of the original message, as
1606 obtained from the message's envelope. For incoming SMTP messages, this is the
1607 address given in the MAIL command. However, when an address is expanded via a
1608 forward or alias file, an alternative address can be specified for delivery
1609 failures of the generated addresses. For a mailing list expansion (see section
1610 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1611 of the list.
1612
1613
1614
1615 .section "Failures to deliver bounce messages" "SECID22"
1616 .cindex "bounce message" "failure to deliver"
1617 If a bounce message (either locally generated or received from a remote host)
1618 itself suffers a permanent delivery failure, the message is left on the queue,
1619 but it is frozen, awaiting the attention of an administrator. There are options
1620 that can be used to make Exim discard such failed messages, or to keep them
1621 for only a short time (see &%timeout_frozen_after%& and
1622 &%ignore_bounce_errors_after%&).
1623
1624
1625
1626
1627
1628 . ////////////////////////////////////////////////////////////////////////////
1629 . ////////////////////////////////////////////////////////////////////////////
1630
1631 .chapter "Building and installing Exim" "CHID3"
1632 .scindex IIDbuex "building Exim"
1633
1634 .section "Unpacking" "SECID23"
1635 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1636 creates a directory with the name of the current release (for example,
1637 &_exim-&version()_&) into which the following files are placed:
1638
1639 .table2 140pt
1640 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1641 .irow &_CHANGES_& "contains a reference to where changes are &&&
1642 documented"
1643 .irow &_LICENCE_& "the GNU General Public Licence"
1644 .irow &_Makefile_& "top-level make file"
1645 .irow &_NOTICE_& "conditions for the use of Exim"
1646 .irow &_README_& "list of files, directories and simple build &&&
1647 instructions"
1648 .endtable
1649
1650 Other files whose names begin with &_README_& may also be present. The
1651 following subdirectories are created:
1652
1653 .table2 140pt
1654 .irow &_Local_& "an empty directory for local configuration files"
1655 .irow &_OS_& "OS-specific files"
1656 .irow &_doc_& "documentation files"
1657 .irow &_exim_monitor_& "source files for the Exim monitor"
1658 .irow &_scripts_& "scripts used in the build process"
1659 .irow &_src_& "remaining source files"
1660 .irow &_util_& "independent utilities"
1661 .endtable
1662
1663 The main utility programs are contained in the &_src_& directory, and are built
1664 with the Exim binary. The &_util_& directory contains a few optional scripts
1665 that may be useful to some sites.
1666
1667
1668 .section "Multiple machine architectures and operating systems" "SECID24"
1669 .cindex "building Exim" "multiple OS/architectures"
1670 The building process for Exim is arranged to make it easy to build binaries for
1671 a number of different architectures and operating systems from the same set of
1672 source files. Compilation does not take place in the &_src_& directory.
1673 Instead, a &'build directory'& is created for each architecture and operating
1674 system.
1675 .cindex "symbolic link" "to build directory"
1676 Symbolic links to the sources are installed in this directory, which is where
1677 the actual building takes place. In most cases, Exim can discover the machine
1678 architecture and operating system for itself, but the defaults can be
1679 overridden if necessary.
1680
1681
1682 .section "PCRE library" "SECTpcre"
1683 .cindex "PCRE library"
1684 Exim no longer has an embedded PCRE library as the vast majority of
1685 modern systems include PCRE as a system library, although you may need
1686 to install the PCRE or PCRE development package for your operating
1687 system. If your system has a normal PCRE installation the Exim build
1688 process will need no further configuration. If the library or the
1689 headers are in an unusual location you will need to either set the PCRE_LIBS
1690 and INCLUDE directives appropriately,
1691 or set PCRE_CONFIG=yes to use the installed &(pcre-config)& command.
1692 If your operating system has no
1693 PCRE support then you will need to obtain and build the current PCRE
1694 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
1695 More information on PCRE is available at &url(http://www.pcre.org/).
1696
1697 .section "DBM libraries" "SECTdb"
1698 .cindex "DBM libraries" "discussion of"
1699 .cindex "hints database" "DBM files used for"
1700 Even if you do not use any DBM files in your configuration, Exim still needs a
1701 DBM library in order to operate, because it uses indexed files for its hints
1702 databases. Unfortunately, there are a number of DBM libraries in existence, and
1703 different operating systems often have different ones installed.
1704
1705 .cindex "Solaris" "DBM library for"
1706 .cindex "IRIX, DBM library for"
1707 .cindex "BSD, DBM library for"
1708 .cindex "Linux, DBM library for"
1709 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1710 Linux distribution, the DBM configuration should happen automatically, and you
1711 may be able to ignore this section. Otherwise, you may have to learn more than
1712 you would like about DBM libraries from what follows.
1713
1714 .cindex "&'ndbm'& DBM library"
1715 Licensed versions of Unix normally contain a library of DBM functions operating
1716 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1717 versions of Unix seem to vary in what they contain as standard. In particular,
1718 some early versions of Linux have no default DBM library, and different
1719 distributors have chosen to bundle different libraries with their packaged
1720 versions. However, the more recent releases seem to have standardized on the
1721 Berkeley DB library.
1722
1723 Different DBM libraries have different conventions for naming the files they
1724 use. When a program opens a file called &_dbmfile_&, there are several
1725 possibilities:
1726
1727 .olist
1728 A traditional &'ndbm'& implementation, such as that supplied as part of
1729 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1730 .next
1731 .cindex "&'gdbm'& DBM library"
1732 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1733 compatibility interface it makes two different hard links to it with names
1734 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1735 file name is used unmodified.
1736 .next
1737 .cindex "Berkeley DB library"
1738 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1739 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1740 programmer exactly the same as the traditional &'ndbm'& implementation.
1741 .next
1742 If the Berkeley package is used in its native mode, it operates on a single
1743 file called &_dbmfile_&; the programmer's interface is somewhat different to
1744 the traditional &'ndbm'& interface.
1745 .next
1746 To complicate things further, there are several very different versions of the
1747 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1748 2.&'x'& and 3.&'x'& were current for a while, but the latest versions are now
1749 numbered 4.&'x'&. Maintenance of some of the earlier releases has ceased. All
1750 versions of Berkeley DB can be obtained from
1751 &url(http://www.sleepycat.com/).
1752 .next
1753 .cindex "&'tdb'& DBM library"
1754 Yet another DBM library, called &'tdb'&, is available from
1755 &url(http://download.sourceforge.net/tdb). It has its own interface, and also
1756 operates on a single file.
1757 .endlist
1758
1759 .cindex "USE_DB"
1760 .cindex "DBM libraries" "configuration for building"
1761 Exim and its utilities can be compiled to use any of these interfaces. In order
1762 to use any version of the Berkeley DB package in native mode, you must set
1763 USE_DB in an appropriate configuration file (typically
1764 &_Local/Makefile_&). For example:
1765 .code
1766 USE_DB=yes
1767 .endd
1768 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1769 error is diagnosed if you set more than one of these.
1770
1771 At the lowest level, the build-time configuration sets none of these options,
1772 thereby assuming an interface of type (1). However, some operating system
1773 configuration files (for example, those for the BSD operating systems and
1774 Linux) assume type (4) by setting USE_DB as their default, and the
1775 configuration files for Cygwin set USE_GDBM. Anything you set in
1776 &_Local/Makefile_&, however, overrides these system defaults.
1777
1778 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1779 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1780 in one of these lines:
1781 .code
1782 DBMLIB = -ldb
1783 DBMLIB = -ltdb
1784 .endd
1785 Settings like that will work if the DBM library is installed in the standard
1786 place. Sometimes it is not, and the library's header file may also not be in
1787 the default path. You may need to set INCLUDE to specify where the header
1788 file is, and to specify the path to the library more fully in DBMLIB, as in
1789 this example:
1790 .code
1791 INCLUDE=-I/usr/local/include/db-4.1
1792 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1793 .endd
1794 There is further detailed discussion about the various DBM libraries in the
1795 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1796
1797
1798
1799 .section "Pre-building configuration" "SECID25"
1800 .cindex "building Exim" "pre-building configuration"
1801 .cindex "configuration for building Exim"
1802 .cindex "&_Local/Makefile_&"
1803 .cindex "&_src/EDITME_&"
1804 Before building Exim, a local configuration file that specifies options
1805 independent of any operating system has to be created with the name
1806 &_Local/Makefile_&. A template for this file is supplied as the file
1807 &_src/EDITME_&, and it contains full descriptions of all the option settings
1808 therein. These descriptions are therefore not repeated here. If you are
1809 building Exim for the first time, the simplest thing to do is to copy
1810 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1811
1812 There are three settings that you must supply, because Exim will not build
1813 without them. They are the location of the run time configuration file
1814 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1815 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1816 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1817 a colon-separated list of file names; Exim uses the first of them that exists.
1818
1819 There are a few other parameters that can be specified either at build time or
1820 at run time, to enable the same binary to be used on a number of different
1821 machines. However, if the locations of Exim's spool directory and log file
1822 directory (if not within the spool directory) are fixed, it is recommended that
1823 you specify them in &_Local/Makefile_& instead of at run time, so that errors
1824 detected early in Exim's execution (such as a malformed configuration file) can
1825 be logged.
1826
1827 .cindex "content scanning" "specifying at build time"
1828 Exim's interfaces for calling virus and spam scanning software directly from
1829 access control lists are not compiled by default. If you want to include these
1830 facilities, you need to set
1831 .code
1832 WITH_CONTENT_SCAN=yes
1833 .endd
1834 in your &_Local/Makefile_&. For details of the facilities themselves, see
1835 chapter &<<CHAPexiscan>>&.
1836
1837
1838 .cindex "&_Local/eximon.conf_&"
1839 .cindex "&_exim_monitor/EDITME_&"
1840 If you are going to build the Exim monitor, a similar configuration process is
1841 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1842 your installation and saved under the name &_Local/eximon.conf_&. If you are
1843 happy with the default settings described in &_exim_monitor/EDITME_&,
1844 &_Local/eximon.conf_& can be empty, but it must exist.
1845
1846 This is all the configuration that is needed in straightforward cases for known
1847 operating systems. However, the building process is set up so that it is easy
1848 to override options that are set by default or by operating-system-specific
1849 configuration files, for example to change the name of the C compiler, which
1850 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1851 do this.
1852
1853
1854
1855 .section "Support for iconv()" "SECID26"
1856 .cindex "&[iconv()]& support"
1857 .cindex "RFC 2047"
1858 The contents of header lines in messages may be encoded according to the rules
1859 described RFC 2047. This makes it possible to transmit characters that are not
1860 in the ASCII character set, and to label them as being in a particular
1861 character set. When Exim is inspecting header lines by means of the &%$h_%&
1862 mechanism, it decodes them, and translates them into a specified character set
1863 (default ISO-8859-1). The translation is possible only if the operating system
1864 supports the &[iconv()]& function.
1865
1866 However, some of the operating systems that supply &[iconv()]& do not support
1867 very many conversions. The GNU &%libiconv%& library (available from
1868 &url(http://www.gnu.org/software/libiconv/)) can be installed on such
1869 systems to remedy this deficiency, as well as on systems that do not supply
1870 &[iconv()]& at all. After installing &%libiconv%&, you should add
1871 .code
1872 HAVE_ICONV=yes
1873 .endd
1874 to your &_Local/Makefile_& and rebuild Exim.
1875
1876
1877
1878 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1879 .cindex "TLS" "including support for TLS"
1880 .cindex "encryption" "including support for"
1881 .cindex "SUPPORT_TLS"
1882 .cindex "OpenSSL" "building Exim with"
1883 .cindex "GnuTLS" "building Exim with"
1884 Exim can be built to support encrypted SMTP connections, using the STARTTLS
1885 command as per RFC 2487. It can also support legacy clients that expect to
1886 start a TLS session immediately on connection to a non-standard port (see the
1887 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1888 line option).
1889
1890 If you want to build Exim with TLS support, you must first install either the
1891 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1892 implementing SSL.
1893
1894 If OpenSSL is installed, you should set
1895 .code
1896 SUPPORT_TLS=yes
1897 TLS_LIBS=-lssl -lcrypto
1898 .endd
1899 in &_Local/Makefile_&. You may also need to specify the locations of the
1900 OpenSSL library and include files. For example:
1901 .code
1902 SUPPORT_TLS=yes
1903 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1904 TLS_INCLUDE=-I/usr/local/openssl/include/
1905 .endd
1906 .cindex "pkg-config" "OpenSSL"
1907 If you have &'pkg-config'& available, then instead you can just use:
1908 .code
1909 SUPPORT_TLS=yes
1910 USE_OPENSSL_PC=openssl
1911 .endd
1912 .cindex "USE_GNUTLS"
1913 If GnuTLS is installed, you should set
1914 .code
1915 SUPPORT_TLS=yes
1916 USE_GNUTLS=yes
1917 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1918 .endd
1919 in &_Local/Makefile_&, and again you may need to specify the locations of the
1920 library and include files. For example:
1921 .code
1922 SUPPORT_TLS=yes
1923 USE_GNUTLS=yes
1924 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1925 TLS_INCLUDE=-I/usr/gnu/include
1926 .endd
1927 .cindex "pkg-config" "GnuTLS"
1928 If you have &'pkg-config'& available, then instead you can just use:
1929 .code
1930 SUPPORT_TLS=yes
1931 USE_GNUTLS=yes
1932 USE_GNUTLS_PC=gnutls
1933 .endd
1934
1935 You do not need to set TLS_INCLUDE if the relevant directory is already
1936 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1937 given in chapter &<<CHAPTLS>>&.
1938
1939
1940
1941
1942 .section "Use of tcpwrappers" "SECID27"
1943
1944 .cindex "tcpwrappers, building Exim to support"
1945 .cindex "USE_TCP_WRAPPERS"
1946 .cindex "TCP_WRAPPERS_DAEMON_NAME"
1947 .cindex "tcp_wrappers_daemon_name"
1948 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
1949 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
1950 alternative to Exim's own checking facilities for installations that are
1951 already making use of &'tcpwrappers'& for other purposes. To do this, you
1952 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
1953 &_tcpd.h_& to be available at compile time, and also ensure that the library
1954 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
1955 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
1956 you might have
1957 .code
1958 USE_TCP_WRAPPERS=yes
1959 CFLAGS=-O -I/usr/local/include
1960 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
1961 .endd
1962 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
1963 files is &"exim"&. For example, the line
1964 .code
1965 exim : LOCAL 192.168.1. .friendly.domain.example
1966 .endd
1967 in your &_/etc/hosts.allow_& file allows connections from the local host, from
1968 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
1969 All other connections are denied. The daemon name used by &'tcpwrappers'&
1970 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
1971 &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
1972 configure file. Consult the &'tcpwrappers'& documentation for
1973 further details.
1974
1975
1976 .section "Including support for IPv6" "SECID28"
1977 .cindex "IPv6" "including support for"
1978 Exim contains code for use on systems that have IPv6 support. Setting
1979 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
1980 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
1981 where the IPv6 support is not fully integrated into the normal include and
1982 library files.
1983
1984 Two different types of DNS record for handling IPv6 addresses have been
1985 defined. AAAA records (analogous to A records for IPv4) are in use, and are
1986 currently seen as the mainstream. Another record type called A6 was proposed
1987 as better than AAAA because it had more flexibility. However, it was felt to be
1988 over-complex, and its status was reduced to &"experimental"&. It is not known
1989 if anyone is actually using A6 records. Exim has support for A6 records, but
1990 this is included only if you set &`SUPPORT_A6=YES`& in &_Local/Makefile_&. The
1991 support has not been tested for some time.
1992
1993
1994
1995 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
1996 .cindex "lookup modules"
1997 .cindex "dynamic modules"
1998 .cindex ".so building"
1999 On some platforms, Exim supports not compiling all lookup types directly into
2000 the main binary, instead putting some into external modules which can be loaded
2001 on demand.
2002 This permits packagers to build Exim with support for lookups with extensive
2003 library dependencies without requiring all users to install all of those
2004 dependencies.
2005 Most, but not all, lookup types can be built this way.
2006
2007 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2008 installed; Exim will only load modules from that directory, as a security
2009 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2010 for your OS; see &_OS/Makefile-Linux_& for an example.
2011 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2012 see &_src/EDITME_& for details.
2013
2014 Then, for each module to be loaded dynamically, define the relevant
2015 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2016 For example, this will build in lsearch but load sqlite and mysql support
2017 on demand:
2018 .code
2019 LOOKUP_LSEARCH=yes
2020 LOOKUP_SQLITE=2
2021 LOOKUP_MYSQL=2
2022 .endd
2023
2024
2025 .section "The building process" "SECID29"
2026 .cindex "build directory"
2027 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2028 created, run &'make'& at the top level. It determines the architecture and
2029 operating system types, and creates a build directory if one does not exist.
2030 For example, on a Sun system running Solaris 8, the directory
2031 &_build-SunOS5-5.8-sparc_& is created.
2032 .cindex "symbolic link" "to source files"
2033 Symbolic links to relevant source files are installed in the build directory.
2034
2035 &*Warning*&: The &%-j%& (parallel) flag must not be used with &'make'&; the
2036 building process fails if it is set.
2037
2038 If this is the first time &'make'& has been run, it calls a script that builds
2039 a make file inside the build directory, using the configuration files from the
2040 &_Local_& directory. The new make file is then passed to another instance of
2041 &'make'&. This does the real work, building a number of utility scripts, and
2042 then compiling and linking the binaries for the Exim monitor (if configured), a
2043 number of utility programs, and finally Exim itself. The command &`make
2044 makefile`& can be used to force a rebuild of the make file in the build
2045 directory, should this ever be necessary.
2046
2047 If you have problems building Exim, check for any comments there may be in the
2048 &_README_& file concerning your operating system, and also take a look at the
2049 FAQ, where some common problems are covered.
2050
2051
2052
2053 .section 'Output from &"make"&' "SECID283"
2054 The output produced by the &'make'& process for compile lines is often very
2055 unreadable, because these lines can be very long. For this reason, the normal
2056 output is suppressed by default, and instead output similar to that which
2057 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2058 each module that is being compiled or linked. However, it is still possible to
2059 get the full output, by calling &'make'& like this:
2060 .code
2061 FULLECHO='' make -e
2062 .endd
2063 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2064 command reflection in &'make'&. When you ask for the full output, it is
2065 given in addition to the short output.
2066
2067
2068
2069 .section "Overriding build-time options for Exim" "SECToverride"
2070 .cindex "build-time options, overriding"
2071 The main make file that is created at the beginning of the building process
2072 consists of the concatenation of a number of files which set configuration
2073 values, followed by a fixed set of &'make'& instructions. If a value is set
2074 more than once, the last setting overrides any previous ones. This provides a
2075 convenient way of overriding defaults. The files that are concatenated are, in
2076 order:
2077 .display
2078 &_OS/Makefile-Default_&
2079 &_OS/Makefile-_&<&'ostype'&>
2080 &_Local/Makefile_&
2081 &_Local/Makefile-_&<&'ostype'&>
2082 &_Local/Makefile-_&<&'archtype'&>
2083 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2084 &_OS/Makefile-Base_&
2085 .endd
2086 .cindex "&_Local/Makefile_&"
2087 .cindex "building Exim" "operating system type"
2088 .cindex "building Exim" "architecture type"
2089 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2090 architecture type. &_Local/Makefile_& is required to exist, and the building
2091 process fails if it is absent. The other three &_Local_& files are optional,
2092 and are often not needed.
2093
2094 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2095 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2096 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2097 values are used, thereby providing a means of forcing particular settings.
2098 Otherwise, the scripts try to get values from the &%uname%& command. If this
2099 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2100 of &'ad hoc'& transformations are then applied, to produce the standard names
2101 that Exim expects. You can run these scripts directly from the shell in order
2102 to find out what values are being used on your system.
2103
2104
2105 &_OS/Makefile-Default_& contains comments about the variables that are set
2106 therein. Some (but not all) are mentioned below. If there is something that
2107 needs changing, review the contents of this file and the contents of the make
2108 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2109 default values are.
2110
2111
2112 .cindex "building Exim" "overriding default settings"
2113 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2114 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2115 need to change the original files. Instead, you should make the changes by
2116 putting the new values in an appropriate &_Local_& file. For example,
2117 .cindex "Tru64-Unix build-time settings"
2118 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2119 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2120 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2121 called with the option &%-std1%&, to make it recognize some of the features of
2122 Standard C that Exim uses. (Most other compilers recognize Standard C by
2123 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2124 containing the lines
2125 .code
2126 CC=cc
2127 CFLAGS=-std1
2128 .endd
2129 If you are compiling for just one operating system, it may be easier to put
2130 these lines directly into &_Local/Makefile_&.
2131
2132 Keeping all your local configuration settings separate from the distributed
2133 files makes it easy to transfer them to new versions of Exim simply by copying
2134 the contents of the &_Local_& directory.
2135
2136
2137 .cindex "NIS lookup type" "including support for"
2138 .cindex "NIS+ lookup type" "including support for"
2139 .cindex "LDAP" "including support for"
2140 .cindex "lookup" "inclusion in binary"
2141 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2142 lookup, but not all systems have these components installed, so the default is
2143 not to include the relevant code in the binary. All the different kinds of file
2144 and database lookup that Exim supports are implemented as separate code modules
2145 which are included only if the relevant compile-time options are set. In the
2146 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2147 .code
2148 LOOKUP_LDAP=yes
2149 LOOKUP_NIS=yes
2150 LOOKUP_NISPLUS=yes
2151 .endd
2152 and similar settings apply to the other lookup types. They are all listed in
2153 &_src/EDITME_&. In many cases the relevant include files and interface
2154 libraries need to be installed before compiling Exim.
2155 .cindex "cdb" "including support for"
2156 However, there are some optional lookup types (such as cdb) for which
2157 the code is entirely contained within Exim, and no external include
2158 files or libraries are required. When a lookup type is not included in the
2159 binary, attempts to configure Exim to use it cause run time configuration
2160 errors.
2161
2162 .cindex "pkg-config" "lookups"
2163 .cindex "pkg-config" "authenticators"
2164 Many systems now use a tool called &'pkg-config'& to encapsulate information
2165 about how to compile against a library; Exim has some initial support for
2166 being able to use pkg-config for lookups and authenticators. For any given
2167 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2168 variable with the &`_PC`& suffix in the name and assign as the value the
2169 name of the package to be queried. The results of querying via the
2170 &'pkg-config'& command will be added to the appropriate Makefile variables
2171 with &`+=`& directives, so your version of &'make'& will need to support that
2172 syntax. For instance:
2173 .code
2174 LOOKUP_SQLITE=yes
2175 LOOKUP_SQLITE_PC=sqlite3
2176 AUTH_GSASL=yes
2177 AUTH_GSASL_PC=libgsasl
2178 AUTH_HEIMDAL_GSSAPI=yes
2179 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2180 .endd
2181
2182 .cindex "Perl" "including support for"
2183 Exim can be linked with an embedded Perl interpreter, allowing Perl
2184 subroutines to be called during string expansion. To enable this facility,
2185 .code
2186 EXIM_PERL=perl.o
2187 .endd
2188 must be defined in &_Local/Makefile_&. Details of this facility are given in
2189 chapter &<<CHAPperl>>&.
2190
2191 .cindex "X11 libraries, location of"
2192 The location of the X11 libraries is something that varies a lot between
2193 operating systems, and there may be different versions of X11 to cope
2194 with. Exim itself makes no use of X11, but if you are compiling the Exim
2195 monitor, the X11 libraries must be available.
2196 The following three variables are set in &_OS/Makefile-Default_&:
2197 .code
2198 X11=/usr/X11R6
2199 XINCLUDE=-I$(X11)/include
2200 XLFLAGS=-L$(X11)/lib
2201 .endd
2202 These are overridden in some of the operating-system configuration files. For
2203 example, in &_OS/Makefile-SunOS5_& there is
2204 .code
2205 X11=/usr/openwin
2206 XINCLUDE=-I$(X11)/include
2207 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2208 .endd
2209 If you need to override the default setting for your operating system, place a
2210 definition of all three of these variables into your
2211 &_Local/Makefile-<ostype>_& file.
2212
2213 .cindex "EXTRALIBS"
2214 If you need to add any extra libraries to the link steps, these can be put in a
2215 variable called EXTRALIBS, which appears in all the link commands, but by
2216 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2217 command for linking the main Exim binary, and not for any associated utilities.
2218
2219 .cindex "DBM libraries" "configuration for building"
2220 There is also DBMLIB, which appears in the link commands for binaries that
2221 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2222 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2223 binary, and which can be used, for example, to include additional X11
2224 libraries.
2225
2226 .cindex "configuration file" "editing"
2227 The make file copes with rebuilding Exim correctly if any of the configuration
2228 files are edited. However, if an optional configuration file is deleted, it is
2229 necessary to touch the associated non-optional file (that is,
2230 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2231
2232
2233 .section "OS-specific header files" "SECID30"
2234 .cindex "&_os.h_&"
2235 .cindex "building Exim" "OS-specific C header files"
2236 The &_OS_& directory contains a number of files with names of the form
2237 &_os.h-<ostype>_&. These are system-specific C header files that should not
2238 normally need to be changed. There is a list of macro settings that are
2239 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2240 are porting Exim to a new operating system.
2241
2242
2243
2244 .section "Overriding build-time options for the monitor" "SECID31"
2245 .cindex "building Eximon"
2246 A similar process is used for overriding things when building the Exim monitor,
2247 where the files that are involved are
2248 .display
2249 &_OS/eximon.conf-Default_&
2250 &_OS/eximon.conf-_&<&'ostype'&>
2251 &_Local/eximon.conf_&
2252 &_Local/eximon.conf-_&<&'ostype'&>
2253 &_Local/eximon.conf-_&<&'archtype'&>
2254 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2255 .endd
2256 .cindex "&_Local/eximon.conf_&"
2257 As with Exim itself, the final three files need not exist, and in this case the
2258 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2259 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2260 variables of the same name, preceded by EXIMON_. For example, setting
2261 EXIMON_LOG_DEPTH in the environment overrides the value of
2262 LOG_DEPTH at run time.
2263 .ecindex IIDbuex
2264
2265
2266 .section "Installing Exim binaries and scripts" "SECID32"
2267 .cindex "installing Exim"
2268 .cindex "BIN_DIRECTORY"
2269 The command &`make install`& runs the &(exim_install)& script with no
2270 arguments. The script copies binaries and utility scripts into the directory
2271 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2272 .cindex "setuid" "installing Exim with"
2273 The install script copies files only if they are newer than the files they are
2274 going to replace. The Exim binary is required to be owned by root and have the
2275 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2276 install`& as root so that it can set up the Exim binary in this way. However, in
2277 some special situations (for example, if a host is doing no local deliveries)
2278 it may be possible to run Exim without making the binary setuid root (see
2279 chapter &<<CHAPsecurity>>& for details).
2280
2281 .cindex "CONFIGURE_FILE"
2282 Exim's run time configuration file is named by the CONFIGURE_FILE setting
2283 in &_Local/Makefile_&. If this names a single file, and the file does not
2284 exist, the default configuration file &_src/configure.default_& is copied there
2285 by the installation script. If a run time configuration file already exists, it
2286 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2287 alternative files, no default is installed.
2288
2289 .cindex "system aliases file"
2290 .cindex "&_/etc/aliases_&"
2291 One change is made to the default configuration file when it is installed: the
2292 default configuration contains a router that references a system aliases file.
2293 The path to this file is set to the value specified by
2294 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2295 If the system aliases file does not exist, the installation script creates it,
2296 and outputs a comment to the user.
2297
2298 The created file contains no aliases, but it does contain comments about the
2299 aliases a site should normally have. Mail aliases have traditionally been
2300 kept in &_/etc/aliases_&. However, some operating systems are now using
2301 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2302 Exim's configuration if necessary.
2303
2304 The default configuration uses the local host's name as the only local domain,
2305 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2306 running as the local user. System aliases and &_.forward_& files in users' home
2307 directories are supported, but no NIS or NIS+ support is configured. Domains
2308 other than the name of the local host are routed using the DNS, with delivery
2309 over SMTP.
2310
2311 It is possible to install Exim for special purposes (such as building a binary
2312 distribution) in a private part of the file system. You can do this by a
2313 command such as
2314 .code
2315 make DESTDIR=/some/directory/ install
2316 .endd
2317 This has the effect of pre-pending the specified directory to all the file
2318 paths, except the name of the system aliases file that appears in the default
2319 configuration. (If a default alias file is created, its name &'is'& modified.)
2320 For backwards compatibility, ROOT is used if DESTDIR is not set,
2321 but this usage is deprecated.
2322
2323 .cindex "installing Exim" "what is not installed"
2324 Running &'make install'& does not copy the Exim 4 conversion script
2325 &'convert4r4'&. You will probably run this only once if you are
2326 upgrading from Exim 3. None of the documentation files in the &_doc_&
2327 directory are copied, except for the info files when you have set
2328 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2329
2330 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2331 to their names. The Exim binary itself, however, is handled differently. It is
2332 installed under a name that includes the version number and the compile number,
2333 for example &_exim-&version()-1_&. The script then arranges for a symbolic link
2334 called &_exim_& to point to the binary. If you are updating a previous version
2335 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2336 from the directory (as seen by other processes).
2337
2338 .cindex "installing Exim" "testing the script"
2339 If you want to see what the &'make install'& will do before running it for
2340 real, you can pass the &%-n%& option to the installation script by this
2341 command:
2342 .code
2343 make INSTALL_ARG=-n install
2344 .endd
2345 The contents of the variable INSTALL_ARG are passed to the installation
2346 script. You do not need to be root to run this test. Alternatively, you can run
2347 the installation script directly, but this must be from within the build
2348 directory. For example, from the top-level Exim directory you could use this
2349 command:
2350 .code
2351 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2352 .endd
2353 .cindex "installing Exim" "install script options"
2354 There are two other options that can be supplied to the installation script.
2355
2356 .ilist
2357 &%-no_chown%& bypasses the call to change the owner of the installed binary
2358 to root, and the call to make it a setuid binary.
2359 .next
2360 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2361 installed binary.
2362 .endlist
2363
2364 INSTALL_ARG can be used to pass these options to the script. For example:
2365 .code
2366 make INSTALL_ARG=-no_symlink install
2367 .endd
2368 The installation script can also be given arguments specifying which files are
2369 to be copied. For example, to install just the Exim binary, and nothing else,
2370 without creating the symbolic link, you could use:
2371 .code
2372 make INSTALL_ARG='-no_symlink exim' install
2373 .endd
2374
2375
2376
2377 .section "Installing info documentation" "SECTinsinfdoc"
2378 .cindex "installing Exim" "&'info'& documentation"
2379 Not all systems use the GNU &'info'& system for documentation, and for this
2380 reason, the Texinfo source of Exim's documentation is not included in the main
2381 distribution. Instead it is available separately from the ftp site (see section
2382 &<<SECTavail>>&).
2383
2384 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2385 source of the documentation is found in the source tree, running &`make
2386 install`& automatically builds the info files and installs them.
2387
2388
2389
2390 .section "Setting up the spool directory" "SECID33"
2391 .cindex "spool directory" "creating"
2392 When it starts up, Exim tries to create its spool directory if it does not
2393 exist. The Exim uid and gid are used for the owner and group of the spool
2394 directory. Sub-directories are automatically created in the spool directory as
2395 necessary.
2396
2397
2398
2399
2400 .section "Testing" "SECID34"
2401 .cindex "testing" "installation"
2402 Having installed Exim, you can check that the run time configuration file is
2403 syntactically valid by running the following command, which assumes that the
2404 Exim binary directory is within your PATH environment variable:
2405 .code
2406 exim -bV
2407 .endd
2408 If there are any errors in the configuration file, Exim outputs error messages.
2409 Otherwise it outputs the version number and build date,
2410 the DBM library that is being used, and information about which drivers and
2411 other optional code modules are included in the binary.
2412 Some simple routing tests can be done by using the address testing option. For
2413 example,
2414 .display
2415 &`exim -bt`& <&'local username'&>
2416 .endd
2417 should verify that it recognizes a local mailbox, and
2418 .display
2419 &`exim -bt`& <&'remote address'&>
2420 .endd
2421 a remote one. Then try getting it to deliver mail, both locally and remotely.
2422 This can be done by passing messages directly to Exim, without going through a
2423 user agent. For example:
2424 .code
2425 exim -v postmaster@your.domain.example
2426 From: user@your.domain.example
2427 To: postmaster@your.domain.example
2428 Subject: Testing Exim
2429
2430 This is a test message.
2431 ^D
2432 .endd
2433 The &%-v%& option causes Exim to output some verification of what it is doing.
2434 In this case you should see copies of three log lines, one for the message's
2435 arrival, one for its delivery, and one containing &"Completed"&.
2436
2437 .cindex "delivery" "problems with"
2438 If you encounter problems, look at Exim's log files (&'mainlog'& and
2439 &'paniclog'&) to see if there is any relevant information there. Another source
2440 of information is running Exim with debugging turned on, by specifying the
2441 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2442 with debugging turned on by a command of the form
2443 .display
2444 &`exim -d -M`& <&'exim-message-id'&>
2445 .endd
2446 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2447 produces rather a lot of output, but you can cut this down to specific areas.
2448 For example, if you use &%-d-all+route%& only the debugging information
2449 relevant to routing is included. (See the &%-d%& option in chapter
2450 &<<CHAPcommandline>>& for more details.)
2451
2452 .cindex '&"sticky"& bit'
2453 .cindex "lock files"
2454 One specific problem that has shown up on some sites is the inability to do
2455 local deliveries into a shared mailbox directory, because it does not have the
2456 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2457 writing to a mailbox file, and if it cannot create the lock file, the delivery
2458 is deferred. You can get round this either by setting the &"sticky bit"& on the
2459 directory, or by setting a specific group for local deliveries and allowing
2460 that group to create files in the directory (see the comments above the
2461 &(local_delivery)& transport in the default configuration file). Another
2462 approach is to configure Exim not to use lock files, but just to rely on
2463 &[fcntl()]& locking instead. However, you should do this only if all user
2464 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2465 see chapter &<<CHAPappendfile>>&.
2466
2467 One thing that cannot be tested on a system that is already running an MTA is
2468 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2469 &%-oX%& option can be used to run an Exim daemon that listens on some other
2470 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2471 &'exim_checkaccess'& utility can be used to check out policy controls on
2472 incoming SMTP mail.
2473
2474 Testing a new version on a system that is already running Exim can most easily
2475 be done by building a binary with a different CONFIGURE_FILE setting. From
2476 within the run time configuration, all other file and directory names
2477 that Exim uses can be altered, in order to keep it entirely clear of the
2478 production version.
2479
2480
2481 .section "Replacing another MTA with Exim" "SECID35"
2482 .cindex "replacing another MTA"
2483 Building and installing Exim for the first time does not of itself put it in
2484 general use. The name by which the system's MTA is called by mail user agents
2485 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2486 operating system), and it is necessary to make this name point to the &'exim'&
2487 binary in order to get the user agents to pass messages to Exim. This is
2488 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2489 or &_/usr/lib/sendmail_&
2490 .cindex "symbolic link" "to &'exim'& binary"
2491 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2492 privilege and executable status from the old MTA. It is then necessary to stop
2493 and restart the mailer daemon, if one is running.
2494
2495 .cindex "FreeBSD, MTA indirection"
2496 .cindex "&_/etc/mail/mailer.conf_&"
2497 Some operating systems have introduced alternative ways of switching MTAs. For
2498 example, if you are running FreeBSD, you need to edit the file
2499 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2500 described. A typical example of the contents of this file for running Exim is
2501 as follows:
2502 .code
2503 sendmail /usr/exim/bin/exim
2504 send-mail /usr/exim/bin/exim
2505 mailq /usr/exim/bin/exim -bp
2506 newaliases /usr/bin/true
2507 .endd
2508 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2509 your Exim installation is &"live"&. Check it by sending a message from your
2510 favourite user agent.
2511
2512 You should consider what to tell your users about the change of MTA. Exim may
2513 have different capabilities to what was previously running, and there are
2514 various operational differences such as the text of messages produced by
2515 command line options and in bounce messages. If you allow your users to make
2516 use of Exim's filtering capabilities, you should make the document entitled
2517 &'Exim's interface to mail filtering'& available to them.
2518
2519
2520
2521 .section "Upgrading Exim" "SECID36"
2522 .cindex "upgrading Exim"
2523 If you are already running Exim on your host, building and installing a new
2524 version automatically makes it available to MUAs, or any other programs that
2525 call the MTA directly. However, if you are running an Exim daemon, you do need
2526 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2527 new binary. You do not need to stop processing mail in order to install a new
2528 version of Exim. The install script does not modify an existing runtime
2529 configuration file.
2530
2531
2532
2533
2534 .section "Stopping the Exim daemon on Solaris" "SECID37"
2535 .cindex "Solaris" "stopping Exim on"
2536 The standard command for stopping the mailer daemon on Solaris is
2537 .code
2538 /etc/init.d/sendmail stop
2539 .endd
2540 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2541 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2542 for the text &"sendmail"&; this is not present because the actual program name
2543 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2544 solution is to replace the line that finds the process id with something like
2545 .code
2546 pid=`cat /var/spool/exim/exim-daemon.pid`
2547 .endd
2548 to obtain the daemon's pid directly from the file that Exim saves it in.
2549
2550 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2551 still be received from local processes, and if automatic delivery is configured
2552 (the normal case), deliveries will still occur.
2553
2554
2555
2556
2557 . ////////////////////////////////////////////////////////////////////////////
2558 . ////////////////////////////////////////////////////////////////////////////
2559
2560 .chapter "The Exim command line" "CHAPcommandline"
2561 .scindex IIDclo1 "command line" "options"
2562 .scindex IIDclo2 "options" "command line"
2563 Exim's command line takes the standard Unix form of a sequence of options,
2564 each starting with a hyphen character, followed by a number of arguments. The
2565 options are compatible with the main options of Sendmail, and there are also
2566 some additional options, some of which are compatible with Smail 3. Certain
2567 combinations of options do not make sense, and provoke an error if used.
2568 The form of the arguments depends on which options are set.
2569
2570
2571 .section "Setting options by program name" "SECID38"
2572 .cindex "&'mailq'&"
2573 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2574 were present before any other options.
2575 The &%-bp%& option requests a listing of the contents of the mail queue on the
2576 standard output.
2577 This feature is for compatibility with some systems that contain a command of
2578 that name in one of the standard libraries, symbolically linked to
2579 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2580
2581 .cindex "&'rsmtp'&"
2582 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2583 were present before any other options, for compatibility with Smail. The
2584 &%-bS%& option is used for reading in a number of messages in batched SMTP
2585 format.
2586
2587 .cindex "&'rmail'&"
2588 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2589 &%-oee%& options were present before any other options, for compatibility with
2590 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2591
2592 .cindex "&'runq'&"
2593 .cindex "queue runner"
2594 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2595 were present before any other options, for compatibility with Smail. The &%-q%&
2596 option causes a single queue runner process to be started.
2597
2598 .cindex "&'newaliases'&"
2599 .cindex "alias file" "building"
2600 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2601 If Exim is called under the name &'newaliases'& it behaves as if the option
2602 &%-bi%& were present before any other options, for compatibility with Sendmail.
2603 This option is used for rebuilding Sendmail's alias file. Exim does not have
2604 the concept of a single alias file, but can be configured to run a given
2605 command if called with the &%-bi%& option.
2606
2607
2608 .section "Trusted and admin users" "SECTtrustedadmin"
2609 Some Exim options are available only to &'trusted users'& and others are
2610 available only to &'admin users'&. In the description below, the phrases &"Exim
2611 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2612 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2613 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2614
2615 .ilist
2616 .cindex "trusted users" "definition of"
2617 .cindex "user" "trusted definition of"
2618 The trusted users are root, the Exim user, any user listed in the
2619 &%trusted_users%& configuration option, and any user whose current group or any
2620 supplementary group is one of those listed in the &%trusted_groups%&
2621 configuration option. Note that the Exim group is not automatically trusted.
2622
2623 .cindex '&"From"& line'
2624 .cindex "envelope sender"
2625 Trusted users are always permitted to use the &%-f%& option or a leading
2626 &"From&~"& line to specify the envelope sender of a message that is passed to
2627 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2628 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2629 users to set envelope senders.
2630
2631 .cindex "&'From:'& header line"
2632 .cindex "&'Sender:'& header line"
2633 For a trusted user, there is never any check on the contents of the &'From:'&
2634 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2635 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2636
2637 Trusted users may also specify a host name, host address, interface address,
2638 protocol name, ident value, and authentication data when submitting a message
2639 locally. Thus, they are able to insert messages into Exim's queue locally that
2640 have the characteristics of messages received from a remote host. Untrusted
2641 users may in some circumstances use &%-f%&, but can never set the other values
2642 that are available to trusted users.
2643 .next
2644 .cindex "user" "admin definition of"
2645 .cindex "admin user" "definition of"
2646 The admin users are root, the Exim user, and any user that is a member of the
2647 Exim group or of any group listed in the &%admin_groups%& configuration option.
2648 The current group does not have to be one of these groups.
2649
2650 Admin users are permitted to list the queue, and to carry out certain
2651 operations on messages, for example, to force delivery failures. It is also
2652 necessary to be an admin user in order to see the full information provided by
2653 the Exim monitor, and full debugging output.
2654
2655 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2656 Exim to attempt delivery of messages on its queue is restricted to admin users.
2657 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2658 option false (that is, specifying &%no_prod_requires_admin%&).
2659
2660 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2661 is restricted to admin users unless &%queue_list_requires_admin%& is set
2662 false.
2663 .endlist
2664
2665
2666 &*Warning*&: If you configure your system so that admin users are able to
2667 edit Exim's configuration file, you are giving those users an easy way of
2668 getting root. There is further discussion of this issue at the start of chapter
2669 &<<CHAPconf>>&.
2670
2671
2672
2673
2674 .section "Command line options" "SECID39"
2675 Exim's command line options are described in alphabetical order below. If none
2676 of the options that specifies a specific action (such as starting the daemon or
2677 a queue runner, or testing an address, or receiving a message in a specific
2678 format, or listing the queue) are present, and there is at least one argument
2679 on the command line, &%-bm%& (accept a local message on the standard input,
2680 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2681 outputs a brief message about itself and exits.
2682
2683 . ////////////////////////////////////////////////////////////////////////////
2684 . Insert a stylized XML comment here, to identify the start of the command line
2685 . options. This is for the benefit of the Perl script that automatically
2686 . creates a man page for the options.
2687 . ////////////////////////////////////////////////////////////////////////////
2688
2689 .literal xml
2690 <!-- === Start of command line options === -->
2691 .literal off
2692
2693
2694 .vlist
2695 .vitem &%--%&
2696 .oindex "--"
2697 .cindex "options" "command line; terminating"
2698 This is a pseudo-option whose only purpose is to terminate the options and
2699 therefore to cause subsequent command line items to be treated as arguments
2700 rather than options, even if they begin with hyphens.
2701
2702 .vitem &%--help%&
2703 .oindex "&%--help%&"
2704 This option causes Exim to output a few sentences stating what it is.
2705 The same output is generated if the Exim binary is called with no options and
2706 no arguments.
2707
2708 .vitem &%--version%&
2709 .oindex "&%--version%&"
2710 This option is an alias for &%-bV%& and causes version information to be
2711 displayed.
2712
2713 .vitem &%-Ac%& &&&
2714 &%-Am%&
2715 .oindex "&%-Ac%&"
2716 .oindex "&%-Am%&"
2717 These options are used by Sendmail for selecting configuration files and are
2718 ignored by Exim.
2719
2720 .vitem &%-B%&<&'type'&>
2721 .oindex "&%-B%&"
2722 .cindex "8-bit characters"
2723 .cindex "Sendmail compatibility" "8-bit characters"
2724 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2725 clean; it ignores this option.
2726
2727 .vitem &%-bd%&
2728 .oindex "&%-bd%&"
2729 .cindex "daemon"
2730 .cindex "SMTP" "listener"
2731 .cindex "queue runner"
2732 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2733 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2734 that the daemon should also initiate periodic queue runs.
2735
2736 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2737 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2738 disconnect from the controlling terminal. When running this way, it can be
2739 stopped by pressing ctrl-C.
2740
2741 By default, Exim listens for incoming connections to the standard SMTP port on
2742 all the host's running interfaces. However, it is possible to listen on other
2743 ports, on multiple ports, and only on specific interfaces. Chapter
2744 &<<CHAPinterfaces>>& contains a description of the options that control this.
2745
2746 When a listening daemon
2747 .cindex "daemon" "process id (pid)"
2748 .cindex "pid (process id)" "of daemon"
2749 is started without the use of &%-oX%& (that is, without overriding the normal
2750 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2751 in Exim's spool directory. This location can be overridden by setting
2752 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2753 running as root.
2754
2755 When &%-oX%& is used on the command line to start a listening daemon, the
2756 process id is not written to the normal pid file path. However, &%-oP%& can be
2757 used to specify a path on the command line if a pid file is required.
2758
2759 The SIGHUP signal
2760 .cindex "SIGHUP"
2761 .cindex "daemon" "restarting"
2762 can be used to cause the daemon to re-execute itself. This should be done
2763 whenever Exim's configuration file, or any file that is incorporated into it by
2764 means of the &%.include%& facility, is changed, and also whenever a new version
2765 of Exim is installed. It is not necessary to do this when other files that are
2766 referenced from the configuration (for example, alias files) are changed,
2767 because these are reread each time they are used.
2768
2769 .vitem &%-bdf%&
2770 .oindex "&%-bdf%&"
2771 This option has the same effect as &%-bd%& except that it never disconnects
2772 from the controlling terminal, even when no debugging is specified.
2773
2774 .vitem &%-be%&
2775 .oindex "&%-be%&"
2776 .cindex "testing" "string expansion"
2777 .cindex "expansion" "testing"
2778 Run Exim in expansion testing mode. Exim discards its root privilege, to
2779 prevent ordinary users from using this mode to read otherwise inaccessible
2780 files. If no arguments are given, Exim runs interactively, prompting for lines
2781 of data. Otherwise, it processes each argument in turn.
2782
2783 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2784 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2785 used without command line arguments. If successful, it uses the &[readline()]&
2786 function, which provides extensive line-editing facilities, for reading the
2787 test data. A line history is supported.
2788
2789 Long expansion expressions can be split over several lines by using backslash
2790 continuations. As in Exim's run time configuration, white space at the start of
2791 continuation lines is ignored. Each argument or data line is passed through the
2792 string expansion mechanism, and the result is output. Variable values from the
2793 configuration file (for example, &$qualify_domain$&) are available, but no
2794 message-specific values (such as &$sender_domain$&) are set, because no message
2795 is being processed (but see &%-bem%& and &%-Mset%&).
2796
2797 &*Note*&: If you use this mechanism to test lookups, and you change the data
2798 files or databases you are using, you must exit and restart Exim before trying
2799 the same lookup again. Otherwise, because each Exim process caches the results
2800 of lookups, you will just get the same result as before.
2801
2802 .vitem &%-bem%&&~<&'filename'&>
2803 .oindex "&%-bem%&"
2804 .cindex "testing" "string expansion"
2805 .cindex "expansion" "testing"
2806 This option operates like &%-be%& except that it must be followed by the name
2807 of a file. For example:
2808 .code
2809 exim -bem /tmp/testmessage
2810 .endd
2811 The file is read as a message (as if receiving a locally-submitted non-SMTP
2812 message) before any of the test expansions are done. Thus, message-specific
2813 variables such as &$message_size$& and &$header_from:$& are available. However,
2814 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2815 recipients are read from the headers in the normal way, and are shown in the
2816 &$recipients$& variable. Note that recipients cannot be given on the command
2817 line, because further arguments are taken as strings to expand (just like
2818 &%-be%&).
2819
2820 .vitem &%-bF%&&~<&'filename'&>
2821 .oindex "&%-bF%&"
2822 .cindex "system filter" "testing"
2823 .cindex "testing" "system filter"
2824 This option is the same as &%-bf%& except that it assumes that the filter being
2825 tested is a system filter. The additional commands that are available only in
2826 system filters are recognized.
2827
2828 .vitem &%-bf%&&~<&'filename'&>
2829 .oindex "&%-bf%&"
2830 .cindex "filter" "testing"
2831 .cindex "testing" "filter file"
2832 .cindex "forward file" "testing"
2833 .cindex "testing" "forward file"
2834 .cindex "Sieve filter" "testing"
2835 This option runs Exim in user filter testing mode; the file is the filter file
2836 to be tested, and a test message must be supplied on the standard input. If
2837 there are no message-dependent tests in the filter, an empty file can be
2838 supplied.
2839
2840 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2841 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2842 filter and a user filter in the same run. For example:
2843 .code
2844 exim -bF /system/filter -bf /user/filter </test/message
2845 .endd
2846 This is helpful when the system filter adds header lines or sets filter
2847 variables that are used by the user filter.
2848
2849 If the test filter file does not begin with one of the special lines
2850 .code
2851 # Exim filter
2852 # Sieve filter
2853 .endd
2854 it is taken to be a normal &_.forward_& file, and is tested for validity under
2855 that interpretation. See sections &<<SECTitenonfilred>>& to
2856 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2857 redirection lists.
2858
2859 The result of an Exim command that uses &%-bf%&, provided no errors are
2860 detected, is a list of the actions that Exim would try to take if presented
2861 with the message for real. More details of filter testing are given in the
2862 separate document entitled &'Exim's interfaces to mail filtering'&.
2863
2864 When testing a filter file,
2865 .cindex "&""From""& line"
2866 .cindex "envelope sender"
2867 .oindex "&%-f%&" "for filter testing"
2868 the envelope sender can be set by the &%-f%& option,
2869 or by a &"From&~"& line at the start of the test message. Various parameters
2870 that would normally be taken from the envelope recipient address of the message
2871 can be set by means of additional command line options (see the next four
2872 options).
2873
2874 .vitem &%-bfd%&&~<&'domain'&>
2875 .oindex "&%-bfd%&"
2876 .vindex "&$qualify_domain$&"
2877 This sets the domain of the recipient address when a filter file is being
2878 tested by means of the &%-bf%& option. The default is the value of
2879 &$qualify_domain$&.
2880
2881 .vitem &%-bfl%&&~<&'local&~part'&>
2882 .oindex "&%-bfl%&"
2883 This sets the local part of the recipient address when a filter file is being
2884 tested by means of the &%-bf%& option. The default is the username of the
2885 process that calls Exim. A local part should be specified with any prefix or
2886 suffix stripped, because that is how it appears to the filter when a message is
2887 actually being delivered.
2888
2889 .vitem &%-bfp%&&~<&'prefix'&>
2890 .oindex "&%-bfp%&"
2891 This sets the prefix of the local part of the recipient address when a filter
2892 file is being tested by means of the &%-bf%& option. The default is an empty
2893 prefix.
2894
2895 .vitem &%-bfs%&&~<&'suffix'&>
2896 .oindex "&%-bfs%&"
2897 This sets the suffix of the local part of the recipient address when a filter
2898 file is being tested by means of the &%-bf%& option. The default is an empty
2899 suffix.
2900
2901 .vitem &%-bh%&&~<&'IP&~address'&>
2902 .oindex "&%-bh%&"
2903 .cindex "testing" "incoming SMTP"
2904 .cindex "SMTP" "testing incoming"
2905 .cindex "testing" "relay control"
2906 .cindex "relaying" "testing configuration"
2907 .cindex "policy control" "testing"
2908 .cindex "debugging" "&%-bh%& option"
2909 This option runs a fake SMTP session as if from the given IP address, using the
2910 standard input and output. The IP address may include a port number at the end,
2911 after a full stop. For example:
2912 .code
2913 exim -bh 10.9.8.7.1234
2914 exim -bh fe80::a00:20ff:fe86:a061.5678
2915 .endd
2916 When an IPv6 address is given, it is converted into canonical form. In the case
2917 of the second example above, the value of &$sender_host_address$& after
2918 conversion to the canonical form is
2919 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2920
2921 Comments as to what is going on are written to the standard error file. These
2922 include lines beginning with &"LOG"& for anything that would have been logged.
2923 This facility is provided for testing configuration options for incoming
2924 messages, to make sure they implement the required policy. For example, you can
2925 test your relay controls using &%-bh%&.
2926
2927 &*Warning 1*&:
2928 .cindex "RFC 1413"
2929 You can test features of the configuration that rely on ident (RFC 1413)
2930 information by using the &%-oMt%& option. However, Exim cannot actually perform
2931 an ident callout when testing using &%-bh%& because there is no incoming SMTP
2932 connection.
2933
2934 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2935 are also skipped when testing using &%-bh%&. If you want these callouts to
2936 occur, use &%-bhc%& instead.
2937
2938 Messages supplied during the testing session are discarded, and nothing is
2939 written to any of the real log files. There may be pauses when DNS (and other)
2940 lookups are taking place, and of course these may time out. The &%-oMi%& option
2941 can be used to specify a specific IP interface and port if this is important,
2942 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
2943 session were authenticated.
2944
2945 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2946 output just states whether a given recipient address from a given host is
2947 acceptable or not. See section &<<SECTcheckaccess>>&.
2948
2949 Features such as authentication and encryption, where the client input is not
2950 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
2951 specialized SMTP test program such as
2952 &url(http://jetmore.org/john/code/#swaks,swaks).
2953
2954 .vitem &%-bhc%&&~<&'IP&~address'&>
2955 .oindex "&%-bhc%&"
2956 This option operates in the same way as &%-bh%&, except that address
2957 verification callouts are performed if required. This includes consulting and
2958 updating the callout cache database.
2959
2960 .vitem &%-bi%&
2961 .oindex "&%-bi%&"
2962 .cindex "alias file" "building"
2963 .cindex "building alias file"
2964 .cindex "Sendmail compatibility" "&%-bi%& option"
2965 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
2966 Exim does not have the concept of a single alias file, and so it cannot mimic
2967 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
2968 tend to appear in various scripts such as NIS make files, so the option must be
2969 recognized.
2970
2971 If &%-bi%& is encountered, the command specified by the &%bi_command%&
2972 configuration option is run, under the uid and gid of the caller of Exim. If
2973 the &%-oA%& option is used, its value is passed to the command as an argument.
2974 The command set by &%bi_command%& may not contain arguments. The command can
2975 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
2976 if this is required. If the &%bi_command%& option is not set, calling Exim with
2977 &%-bi%& is a no-op.
2978
2979 . // Keep :help first, then the rest in alphabetical order
2980 .vitem &%-bI:help%&
2981 .oindex "&%-bI:help%&"
2982 .cindex "querying exim information"
2983 We shall provide various options starting &`-bI:`& for querying Exim for
2984 information. The output of many of these will be intended for machine
2985 consumption. This one is not. The &%-bI:help%& option asks Exim for a
2986 synopsis of supported options beginning &`-bI:`&. Use of any of these
2987 options shall cause Exim to exit after producing the requested output.
2988
2989 .vitem &%-bI:dscp%&
2990 .oindex "&%-bI:dscp%&"
2991 .cindex "DSCP" "values"
2992 This option causes Exim to emit an alphabetically sorted list of all
2993 recognised DSCP names.
2994
2995 .vitem &%-bI:sieve%&
2996 .oindex "&%-bI:sieve%&"
2997 .cindex "Sieve filter" "capabilities"
2998 This option causes Exim to emit an alphabetically sorted list of all supported
2999 Sieve protocol extensions on stdout, one per line. This is anticipated to be
3000 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
3001 &`SIEVE`& capability response line. As the precise list may depend upon
3002 compile-time build options, which this option will adapt to, this is the only
3003 way to guarantee a correct response.
3004
3005 .vitem &%-bm%&
3006 .oindex "&%-bm%&"
3007 .cindex "local message reception"
3008 This option runs an Exim receiving process that accepts an incoming,
3009 locally-generated message on the standard input. The recipients are given as the
3010 command arguments (except when &%-t%& is also present &-- see below). Each
3011 argument can be a comma-separated list of RFC 2822 addresses. This is the
3012 default option for selecting the overall action of an Exim call; it is assumed
3013 if no other conflicting option is present.
3014
3015 If any addresses in the message are unqualified (have no domain), they are
3016 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3017 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3018 suppressing this for special cases.
3019
3020 Policy checks on the contents of local messages can be enforced by means of
3021 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3022
3023 .cindex "return code" "for &%-bm%&"
3024 The return code is zero if the message is successfully accepted. Otherwise, the
3025 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3026
3027 The format
3028 .cindex "message" "format"
3029 .cindex "format" "message"
3030 .cindex "&""From""& line"
3031 .cindex "UUCP" "&""From""& line"
3032 .cindex "Sendmail compatibility" "&""From""& line"
3033 of the message must be as defined in RFC 2822, except that, for
3034 compatibility with Sendmail and Smail, a line in one of the forms
3035 .code
3036 From sender Fri Jan 5 12:55 GMT 1997
3037 From sender Fri, 5 Jan 97 12:55:01
3038 .endd
3039 (with the weekday optional, and possibly with additional text after the date)
3040 is permitted to appear at the start of the message. There appears to be no
3041 authoritative specification of the format of this line. Exim recognizes it by
3042 matching against the regular expression defined by the &%uucp_from_pattern%&
3043 option, which can be changed if necessary.
3044
3045 .oindex "&%-f%&" "overriding &""From""& line"
3046 The specified sender is treated as if it were given as the argument to the
3047 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3048 preference to the address taken from the message. The caller of Exim must be a
3049 trusted user for the sender of a message to be set in this way.
3050
3051 .vitem &%-bmalware%&&~<&'filename'&>
3052 .oindex "&%-bmalware%&"
3053 .cindex "testing", "malware"
3054 .cindex "malware scan test"
3055 This debugging option causes Exim to scan the given file,
3056 using the malware scanning framework. The option of &%av_scanner%& influences
3057 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3058 the expansion should have defaults which apply to this invocation. ACLs are
3059 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3060 will never be populated and &%-bmalware%& will fail.
3061
3062 Exim will have changed working directory before resolving the filename, so
3063 using fully qualified pathnames is advisable. Exim will be running as the Exim
3064 user when it tries to open the file, rather than as the invoking user.
3065 This option requires admin privileges.
3066
3067 The &%-bmalware%& option will not be extended to be more generally useful,
3068 there are better tools for file-scanning. This option exists to help
3069 administrators verify their Exim and AV scanner configuration.
3070
3071 .vitem &%-bnq%&
3072 .oindex "&%-bnq%&"
3073 .cindex "address qualification, suppressing"
3074 By default, Exim automatically qualifies unqualified addresses (those
3075 without domains) that appear in messages that are submitted locally (that
3076 is, not over TCP/IP). This qualification applies both to addresses in
3077 envelopes, and addresses in header lines. Sender addresses are qualified using
3078 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3079 defaults to the value of &%qualify_domain%&).
3080
3081 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3082 being used to re-submit messages that originally came from remote hosts after
3083 content scanning, you probably do not want to qualify unqualified addresses in
3084 header lines. (Such lines will be present only if you have not enabled a header
3085 syntax check in the appropriate ACL.)
3086
3087 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3088 messages that originate on the local host. When this is used, unqualified
3089 addresses in the envelope provoke errors (causing message rejection) and
3090 unqualified addresses in header lines are left alone.
3091
3092
3093 .vitem &%-bP%&
3094 .oindex "&%-bP%&"
3095 .cindex "configuration options" "extracting"
3096 .cindex "options" "configuration &-- extracting"
3097 If this option is given with no arguments, it causes the values of all Exim's
3098 main configuration options to be written to the standard output. The values
3099 of one or more specific options can be requested by giving their names as
3100 arguments, for example:
3101 .code
3102 exim -bP qualify_domain hold_domains
3103 .endd
3104 .cindex "hiding configuration option values"
3105 .cindex "configuration options" "hiding value of"
3106 .cindex "options" "hiding value of"
3107 However, any option setting that is preceded by the word &"hide"& in the
3108 configuration file is not shown in full, except to an admin user. For other
3109 users, the output is as in this example:
3110 .code
3111 mysql_servers = <value not displayable>
3112 .endd
3113 If &%configure_file%& is given as an argument, the name of the run time
3114 configuration file is output.
3115 If a list of configuration files was supplied, the value that is output here
3116 is the name of the file that was actually used.
3117
3118 .cindex "options" "hiding name of"
3119 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3120 name will not be output.
3121
3122 .cindex "daemon" "process id (pid)"
3123 .cindex "pid (process id)" "of daemon"
3124 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3125 directories where log files and daemon pid files are written are output,
3126 respectively. If these values are unset, log files are written in a
3127 sub-directory of the spool directory called &%log%&, and the pid file is
3128 written directly into the spool directory.
3129
3130 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3131 .code
3132 exim -bP +local_domains
3133 .endd
3134 it searches for a matching named list of any type (domain, host, address, or
3135 local part) and outputs what it finds.
3136
3137 .cindex "options" "router &-- extracting"
3138 .cindex "options" "transport &-- extracting"
3139 .cindex "options" "authenticator &-- extracting"
3140 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3141 followed by the name of an appropriate driver instance, the option settings for
3142 that driver are output. For example:
3143 .code
3144 exim -bP transport local_delivery
3145 .endd
3146 The generic driver options are output first, followed by the driver's private
3147 options. A list of the names of drivers of a particular type can be obtained by
3148 using one of the words &%router_list%&, &%transport_list%&, or
3149 &%authenticator_list%&, and a complete list of all drivers with their option
3150 settings can be obtained by using &%routers%&, &%transports%&, or
3151 &%authenticators%&.
3152
3153 .cindex "options" "macro &-- extracting"
3154 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3155 are available, similarly to the drivers. Because macros are sometimes used
3156 for storing passwords, this option is restricted.
3157 The output format is one item per line.
3158
3159 .vitem &%-bp%&
3160 .oindex "&%-bp%&"
3161 .cindex "queue" "listing messages on"
3162 .cindex "listing" "messages on the queue"
3163 This option requests a listing of the contents of the mail queue on the
3164 standard output. If the &%-bp%& option is followed by a list of message ids,
3165 just those messages are listed. By default, this option can be used only by an
3166 admin user. However, the &%queue_list_requires_admin%& option can be set false
3167 to allow any user to see the queue.
3168
3169 Each message on the queue is displayed as in the following example:
3170 .code
3171 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3172 red.king@looking-glass.fict.example
3173 <other addresses>
3174 .endd
3175 .cindex "message" "size in queue listing"
3176 .cindex "size" "of message"
3177 The first line contains the length of time the message has been on the queue
3178 (in this case 25 minutes), the size of the message (2.9K), the unique local
3179 identifier for the message, and the message sender, as contained in the
3180 envelope. For bounce messages, the sender address is empty, and appears as
3181 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3182 the default sender address, the user's login name is shown in parentheses
3183 before the sender address.
3184
3185 .cindex "frozen messages" "in queue listing"
3186 If the message is frozen (attempts to deliver it are suspended) then the text
3187 &"*** frozen ***"& is displayed at the end of this line.
3188
3189 The recipients of the message (taken from the envelope, not the headers) are
3190 displayed on subsequent lines. Those addresses to which the message has already
3191 been delivered are marked with the letter D. If an original address gets
3192 expanded into several addresses via an alias or forward file, the original is
3193 displayed with a D only when deliveries for all of its child addresses are
3194 complete.
3195
3196
3197 .vitem &%-bpa%&
3198 .oindex "&%-bpa%&"
3199 This option operates like &%-bp%&, but in addition it shows delivered addresses
3200 that were generated from the original top level address(es) in each message by
3201 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3202 of just &"D"&.
3203
3204
3205 .vitem &%-bpc%&
3206 .oindex "&%-bpc%&"
3207 .cindex "queue" "count of messages on"
3208 This option counts the number of messages on the queue, and writes the total
3209 to the standard output. It is restricted to admin users, unless
3210 &%queue_list_requires_admin%& is set false.
3211
3212
3213 .vitem &%-bpr%&
3214 .oindex "&%-bpr%&"
3215 This option operates like &%-bp%&, but the output is not sorted into
3216 chronological order of message arrival. This can speed it up when there are
3217 lots of messages on the queue, and is particularly useful if the output is
3218 going to be post-processed in a way that doesn't need the sorting.
3219
3220 .vitem &%-bpra%&
3221 .oindex "&%-bpra%&"
3222 This option is a combination of &%-bpr%& and &%-bpa%&.
3223
3224 .vitem &%-bpru%&
3225 .oindex "&%-bpru%&"
3226 This option is a combination of &%-bpr%& and &%-bpu%&.
3227
3228
3229 .vitem &%-bpu%&
3230 .oindex "&%-bpu%&"
3231 This option operates like &%-bp%& but shows only undelivered top-level
3232 addresses for each message displayed. Addresses generated by aliasing or
3233 forwarding are not shown, unless the message was deferred after processing by a
3234 router with the &%one_time%& option set.
3235
3236
3237 .vitem &%-brt%&
3238 .oindex "&%-brt%&"
3239 .cindex "testing" "retry configuration"
3240 .cindex "retry" "configuration testing"
3241 This option is for testing retry rules, and it must be followed by up to three
3242 arguments. It causes Exim to look for a retry rule that matches the values
3243 and to write it to the standard output. For example:
3244 .code
3245 exim -brt bach.comp.mus.example
3246 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3247 .endd
3248 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3249 argument, which is required, can be a complete address in the form
3250 &'local_part@domain'&, or it can be just a domain name. If the second argument
3251 contains a dot, it is interpreted as an optional second domain name; if no
3252 retry rule is found for the first argument, the second is tried. This ties in
3253 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3254 rule is found that matches the host, one that matches the mail domain is
3255 sought. Finally, an argument that is the name of a specific delivery error, as
3256 used in setting up retry rules, can be given. For example:
3257 .code
3258 exim -brt haydn.comp.mus.example quota_3d
3259 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3260 .endd
3261
3262 .vitem &%-brw%&
3263 .oindex "&%-brw%&"
3264 .cindex "testing" "rewriting"
3265 .cindex "rewriting" "testing"
3266 This option is for testing address rewriting rules, and it must be followed by
3267 a single argument, consisting of either a local part without a domain, or a
3268 complete address with a fully qualified domain. Exim outputs how this address
3269 would be rewritten for each possible place it might appear. See chapter
3270 &<<CHAPrewrite>>& for further details.
3271
3272 .vitem &%-bS%&
3273 .oindex "&%-bS%&"
3274 .cindex "SMTP" "batched incoming"
3275 .cindex "batched SMTP input"
3276 This option is used for batched SMTP input, which is an alternative interface
3277 for non-interactive local message submission. A number of messages can be
3278 submitted in a single run. However, despite its name, this is not really SMTP
3279 input. Exim reads each message's envelope from SMTP commands on the standard
3280 input, but generates no responses. If the caller is trusted, or
3281 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3282 believed; otherwise the sender is always the caller of Exim.
3283
3284 The message itself is read from the standard input, in SMTP format (leading
3285 dots doubled), terminated by a line containing just a single dot. An error is
3286 provoked if the terminating dot is missing. A further message may then follow.
3287
3288 As for other local message submissions, the contents of incoming batch SMTP
3289 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3290 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3291 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3292
3293 Some other SMTP commands are recognized in the input. HELO and EHLO act
3294 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3295 QUIT quits, ignoring the rest of the standard input.
3296
3297 .cindex "return code" "for &%-bS%&"
3298 If any error is encountered, reports are written to the standard output and
3299 error streams, and Exim gives up immediately. The return code is 0 if no error
3300 was detected; it is 1 if one or more messages were accepted before the error
3301 was detected; otherwise it is 2.
3302
3303 More details of input using batched SMTP are given in section
3304 &<<SECTincomingbatchedSMTP>>&.
3305
3306 .vitem &%-bs%&
3307 .oindex "&%-bs%&"
3308 .cindex "SMTP" "local input"
3309 .cindex "local SMTP input"
3310 This option causes Exim to accept one or more messages by reading SMTP commands
3311 on the standard input, and producing SMTP replies on the standard output. SMTP
3312 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3313 Some user agents use this interface as a way of passing locally-generated
3314 messages to the MTA.
3315
3316 In
3317 .cindex "sender" "source of"
3318 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3319 set, the senders of messages are taken from the SMTP MAIL commands.
3320 Otherwise the content of these commands is ignored and the sender is set up as
3321 the calling user. Unqualified addresses are automatically qualified using
3322 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3323 &%-bnq%& option is used.
3324
3325 .cindex "inetd"
3326 The
3327 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3328 using a listening daemon. Exim can distinguish the two cases by checking
3329 whether the standard input is a TCP/IP socket. When Exim is called from
3330 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3331 above concerning senders and qualification do not apply. In this situation,
3332 Exim behaves in exactly the same way as it does when receiving a message via
3333 the listening daemon.
3334
3335 .vitem &%-bt%&
3336 .oindex "&%-bt%&"
3337 .cindex "testing" "addresses"
3338 .cindex "address" "testing"
3339 This option runs Exim in address testing mode, in which each argument is taken
3340 as a recipient address to be tested for deliverability. The results are
3341 written to the standard output. If a test fails, and the caller is not an admin
3342 user, no details of the failure are output, because these might contain
3343 sensitive information such as usernames and passwords for database lookups.
3344
3345 If no arguments are given, Exim runs in an interactive manner, prompting with a
3346 right angle bracket for addresses to be tested.
3347
3348 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3349 &[readline()]& function, because it is running as &'root'& and there are
3350 security issues.
3351
3352 Each address is handled as if it were the recipient address of a message
3353 (compare the &%-bv%& option). It is passed to the routers and the result is
3354 written to the standard output. However, any router that has
3355 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3356 genuine routing tests if your first router passes everything to a scanner
3357 program.
3358
3359 .cindex "return code" "for &%-bt%&"
3360 The return code is 2 if any address failed outright; it is 1 if no address
3361 failed outright but at least one could not be resolved for some reason. Return
3362 code 0 is given only when all addresses succeed.
3363
3364 .cindex "duplicate addresses"
3365 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3366 addresses after routing is complete, so that only one delivery takes place.
3367 This does not happen when testing with &%-bt%&; the full results of routing are
3368 always shown.
3369
3370 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3371 routers in the configuration makes any tests on the sender address of a
3372 message,
3373 .oindex "&%-f%&" "for address testing"
3374 you can use the &%-f%& option to set an appropriate sender when running
3375 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3376 default qualifying domain. However, if you have set up (for example) routers
3377 whose behaviour depends on the contents of an incoming message, you cannot test
3378 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3379 doing such tests.
3380
3381 .vitem &%-bV%&
3382 .oindex "&%-bV%&"
3383 .cindex "version number of Exim"
3384 This option causes Exim to write the current version number, compilation
3385 number, and compilation date of the &'exim'& binary to the standard output.
3386 It also lists the DBM library that is being used, the optional modules (such as
3387 specific lookup types), the drivers that are included in the binary, and the
3388 name of the run time configuration file that is in use.
3389
3390 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3391 configuration file. However, this is a static check only. It cannot check
3392 values that are to be expanded. For example, although a misspelt ACL verb is
3393 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3394 alone to discover (for example) all the typos in the configuration; some
3395 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3396 dynamic testing facilities.
3397
3398 .vitem &%-bv%&
3399 .oindex "&%-bv%&"
3400 .cindex "verifying address" "using &%-bv%&"
3401 .cindex "address" "verification"
3402 This option runs Exim in address verification mode, in which each argument is
3403 taken as a recipient address to be verified by the routers. (This does
3404 not involve any verification callouts). During normal operation, verification
3405 happens mostly as a consequence processing a &%verify%& condition in an ACL
3406 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3407 including callouts, see the &%-bh%& and &%-bhc%& options.
3408
3409 If verification fails, and the caller is not an admin user, no details of the
3410 failure are output, because these might contain sensitive information such as
3411 usernames and passwords for database lookups.
3412
3413 If no arguments are given, Exim runs in an interactive manner, prompting with a
3414 right angle bracket for addresses to be verified.
3415
3416 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3417 &[readline()]& function, because it is running as &'exim'& and there are
3418 security issues.
3419
3420 Verification differs from address testing (the &%-bt%& option) in that routers
3421 that have &%no_verify%& set are skipped, and if the address is accepted by a
3422 router that has &%fail_verify%& set, verification fails. The address is
3423 verified as a recipient if &%-bv%& is used; to test verification for a sender
3424 address, &%-bvs%& should be used.
3425
3426 If the &%-v%& option is not set, the output consists of a single line for each
3427 address, stating whether it was verified or not, and giving a reason in the
3428 latter case. Without &%-v%&, generating more than one address by redirection
3429 causes verification to end successfully, without considering the generated
3430 addresses. However, if just one address is generated, processing continues,
3431 and the generated address must verify successfully for the overall verification
3432 to succeed.
3433
3434 When &%-v%& is set, more details are given of how the address has been handled,
3435 and in the case of address redirection, all the generated addresses are also
3436 considered. Verification may succeed for some and fail for others.
3437
3438 The
3439 .cindex "return code" "for &%-bv%&"
3440 return code is 2 if any address failed outright; it is 1 if no address
3441 failed outright but at least one could not be resolved for some reason. Return
3442 code 0 is given only when all addresses succeed.
3443
3444 If any of the routers in the configuration makes any tests on the sender
3445 address of a message, you should use the &%-f%& option to set an appropriate
3446 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3447 calling user at the default qualifying domain.
3448
3449 .vitem &%-bvs%&
3450 .oindex "&%-bvs%&"
3451 This option acts like &%-bv%&, but verifies the address as a sender rather
3452 than a recipient address. This affects any rewriting and qualification that
3453 might happen.
3454
3455 .vitem &%-bw%&
3456 .oindex "&%-bw%&"
3457 .cindex "daemon"
3458 .cindex "inetd"
3459 .cindex "inetd" "wait mode"
3460 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3461 similarly to the &%-bd%& option. All port specifications on the command-line
3462 and in the configuration file are ignored. Queue-running may not be specified.
3463
3464 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3465 listening for connections. This permits the system to start up and have
3466 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3467 each port only when the first connection is received.
3468
3469 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3470 which the daemon will exit, which should cause inetd to listen once more.
3471
3472 .vitem &%-C%&&~<&'filelist'&>
3473 .oindex "&%-C%&"
3474 .cindex "configuration file" "alternate"
3475 .cindex "CONFIGURE_FILE"
3476 .cindex "alternate configuration file"
3477 This option causes Exim to find the run time configuration file from the given
3478 list instead of from the list specified by the CONFIGURE_FILE
3479 compile-time setting. Usually, the list will consist of just a single file
3480 name, but it can be a colon-separated list of names. In this case, the first
3481 file that exists is used. Failure to open an existing file stops Exim from
3482 proceeding any further along the list, and an error is generated.
3483
3484 When this option is used by a caller other than root, and the list is different
3485 from the compiled-in list, Exim gives up its root privilege immediately, and
3486 runs with the real and effective uid and gid set to those of the caller.
3487 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3488 file contains a list of full pathnames, one per line, for configuration files
3489 which are trusted. Root privilege is retained for any configuration file so
3490 listed, as long as the caller is the Exim user (or the user specified in the
3491 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3492 not writeable by inappropriate users or groups.
3493
3494 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3495 configuration using &%-C%& right through message reception and delivery,
3496 even if the caller is root. The reception works, but by that time, Exim is
3497 running as the Exim user, so when it re-executes to regain privilege for the
3498 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3499 test reception and delivery using two separate commands (one to put a message
3500 on the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3501
3502 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3503 prefix string with which any file named in a &%-C%& command line option
3504 must start. In addition, the file name must not contain the sequence &`/../`&.
3505 However, if the value of the &%-C%& option is identical to the value of
3506 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3507 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3508 unset, any file name can be used with &%-C%&.
3509
3510 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3511 to a directory to which only root has access. This prevents someone who has
3512 broken into the Exim account from running a privileged Exim with an arbitrary
3513 configuration file.
3514
3515 The &%-C%& facility is useful for ensuring that configuration files are
3516 syntactically correct, but cannot be used for test deliveries, unless the
3517 caller is privileged, or unless it is an exotic configuration that does not
3518 require privilege. No check is made on the owner or group of the files
3519 specified by this option.
3520
3521
3522 .vitem &%-D%&<&'macro'&>=<&'value'&>
3523 .oindex "&%-D%&"
3524 .cindex "macro" "setting on command line"
3525 This option can be used to override macro definitions in the configuration file
3526 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3527 unprivileged caller, it causes Exim to give up its root privilege.
3528 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3529 completely disabled, and its use causes an immediate error exit.
3530
3531 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3532 colon-separated list of macros which are considered safe and, if &%-D%& only
3533 supplies macros from this list, and the values are acceptable, then Exim will
3534 not give up root privilege if the caller is root, the Exim run-time user, or
3535 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3536 to be removed in the future. Acceptable values for the macros satisfy the
3537 regexp: &`^[A-Za-z0-9_/.-]*$`&
3538
3539 The entire option (including equals sign if present) must all be within one
3540 command line item. &%-D%& can be used to set the value of a macro to the empty
3541 string, in which case the equals sign is optional. These two commands are
3542 synonymous:
3543 .code
3544 exim -DABC ...
3545 exim -DABC= ...
3546 .endd
3547 To include spaces in a macro definition item, quotes must be used. If you use
3548 quotes, spaces are permitted around the macro name and the equals sign. For
3549 example:
3550 .code
3551 exim '-D ABC = something' ...
3552 .endd
3553 &%-D%& may be repeated up to 10 times on a command line.
3554
3555
3556 .vitem &%-d%&<&'debug&~options'&>
3557 .oindex "&%-d%&"
3558 .cindex "debugging" "list of selectors"
3559 .cindex "debugging" "&%-d%& option"
3560 This option causes debugging information to be written to the standard
3561 error stream. It is restricted to admin users because debugging output may show
3562 database queries that contain password information. Also, the details of users'
3563 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3564 writes an error message to the standard error stream and exits with a non-zero
3565 return code.
3566
3567 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3568 standard debugging data is output. This can be reduced, or increased to include
3569 some more rarely needed information, by directly following &%-d%& with a string
3570 made up of names preceded by plus or minus characters. These add or remove sets
3571 of debugging data, respectively. For example, &%-d+filter%& adds filter
3572 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3573 no spaces are allowed in the debug setting. The available debugging categories
3574 are:
3575 .display
3576 &`acl `& ACL interpretation
3577 &`auth `& authenticators
3578 &`deliver `& general delivery logic
3579 &`dns `& DNS lookups (see also resolver)
3580 &`dnsbl `& DNS black list (aka RBL) code
3581 &`exec `& arguments for &[execv()]& calls
3582 &`expand `& detailed debugging for string expansions
3583 &`filter `& filter handling
3584 &`hints_lookup `& hints data lookups
3585 &`host_lookup `& all types of name-to-IP address handling
3586 &`ident `& ident lookup
3587 &`interface `& lists of local interfaces
3588 &`lists `& matching things in lists
3589 &`load `& system load checks
3590 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3591 &<<CHAPlocalscan>>&)
3592 &`lookup `& general lookup code and all lookups
3593 &`memory `& memory handling
3594 &`pid `& add pid to debug output lines
3595 &`process_info `& setting info for the process log
3596 &`queue_run `& queue runs
3597 &`receive `& general message reception logic
3598 &`resolver `& turn on the DNS resolver's debugging output
3599 &`retry `& retry handling
3600 &`rewrite `& address rewriting
3601 &`route `& address routing
3602 &`timestamp `& add timestamp to debug output lines
3603 &`tls `& TLS logic
3604 &`transport `& transports
3605 &`uid `& changes of uid/gid and looking up uid/gid
3606 &`verify `& address verification logic
3607 &`all `& almost all of the above (see below), and also &%-v%&
3608 .endd
3609 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3610 for &`-all`&. The reason for this is that &`+all`& is something that people
3611 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3612 is included, an awful lot of output that is very rarely of interest is
3613 generated, so it now has to be explicitly requested. However, &`-all`& does
3614 turn everything off.
3615
3616 .cindex "resolver, debugging output"
3617 .cindex "DNS resolver, debugging output"
3618 The &`resolver`& option produces output only if the DNS resolver was compiled
3619 with DEBUG enabled. This is not the case in some operating systems. Also,
3620 unfortunately, debugging output from the DNS resolver is written to stdout
3621 rather than stderr.
3622
3623 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3624 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3625 However, the &`pid`& selector is forced when debugging is turned on for a
3626 daemon, which then passes it on to any re-executed Exims. Exim also
3627 automatically adds the pid to debug lines when several remote deliveries are
3628 run in parallel.
3629
3630 The &`timestamp`& selector causes the current time to be inserted at the start
3631 of all debug output lines. This can be useful when trying to track down delays
3632 in processing.
3633
3634 If the &%debug_print%& option is set in any driver, it produces output whenever
3635 any debugging is selected, or if &%-v%& is used.
3636
3637 .vitem &%-dd%&<&'debug&~options'&>
3638 .oindex "&%-dd%&"
3639 This option behaves exactly like &%-d%& except when used on a command that
3640 starts a daemon process. In that case, debugging is turned off for the
3641 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3642 behaviour of the daemon without creating as much output as full debugging does.
3643
3644 .vitem &%-dropcr%&
3645 .oindex "&%-dropcr%&"
3646 This is an obsolete option that is now a no-op. It used to affect the way Exim
3647 handled CR and LF characters in incoming messages. What happens now is
3648 described in section &<<SECTlineendings>>&.
3649
3650 .vitem &%-E%&
3651 .oindex "&%-E%&"
3652 .cindex "bounce message" "generating"
3653 This option specifies that an incoming message is a locally-generated delivery
3654 failure report. It is used internally by Exim when handling delivery failures
3655 and is not intended for external use. Its only effect is to stop Exim
3656 generating certain messages to the postmaster, as otherwise message cascades
3657 could occur in some situations. As part of the same option, a message id may
3658 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3659 new message contains the id, following &"R="&, as a cross-reference.
3660
3661 .vitem &%-e%&&'x'&
3662 .oindex "&%-e%&&'x'&"
3663 There are a number of Sendmail options starting with &%-oe%& which seem to be
3664 called by various programs without the leading &%o%& in the option. For
3665 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3666 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3667
3668 .vitem &%-F%&&~<&'string'&>
3669 .oindex "&%-F%&"
3670 .cindex "sender" "name"
3671 .cindex "name" "of sender"
3672 This option sets the sender's full name for use when a locally-generated
3673 message is being accepted. In the absence of this option, the user's &'gecos'&
3674 entry from the password data is used. As users are generally permitted to alter
3675 their &'gecos'& entries, no security considerations are involved. White space
3676 between &%-F%& and the <&'string'&> is optional.
3677
3678 .vitem &%-f%&&~<&'address'&>
3679 .oindex "&%-f%&"
3680 .cindex "sender" "address"
3681 .cindex "address" "sender"
3682 .cindex "trusted users"
3683 .cindex "envelope sender"
3684 .cindex "user" "trusted"
3685 This option sets the address of the envelope sender of a locally-generated
3686 message (also known as the return path). The option can normally be used only
3687 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3688 users to use it.
3689
3690 Processes running as root or the Exim user are always trusted. Other
3691 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3692 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3693 of a local message is set to the caller's login name at the default qualify
3694 domain.
3695
3696 There is one exception to the restriction on the use of &%-f%&: an empty sender
3697 can be specified by any user, trusted or not, to create a message that can
3698 never provoke a bounce. An empty sender can be specified either as an empty
3699 string, or as a pair of angle brackets with nothing between them, as in these
3700 examples of shell commands:
3701 .code
3702 exim -f '<>' user@domain
3703 exim -f "" user@domain
3704 .endd
3705 In addition, the use of &%-f%& is not restricted when testing a filter file
3706 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3707 &%-bv%& options.
3708
3709 Allowing untrusted users to change the sender address does not of itself make
3710 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3711 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3712 though this can be overridden by setting &%no_local_from_check%&.
3713
3714 White
3715 .cindex "&""From""& line"
3716 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3717 given as two arguments or one combined argument). The sender of a
3718 locally-generated message can also be set (when permitted) by an initial
3719 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3720 if &%-f%& is also present, it overrides &"From&~"&.
3721
3722 .vitem &%-G%&
3723 .oindex "&%-G%&"
3724 .cindex "submission fixups, suppressing (command-line)"
3725 This option is equivalent to an ACL applying:
3726 .code
3727 control = suppress_local_fixups
3728 .endd
3729 for every message received. Note that Sendmail will complain about such
3730 bad formatting, where Exim silently just does not fix it up. This may change
3731 in future.
3732
3733 As this affects audit information, the caller must be a trusted user to use
3734 this option.
3735
3736 .vitem &%-h%&&~<&'number'&>
3737 .oindex "&%-h%&"
3738 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3739 This option is accepted for compatibility with Sendmail, but has no effect. (In
3740 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3741 headers.)
3742
3743 .vitem &%-i%&
3744 .oindex "&%-i%&"
3745 .cindex "Solaris" "&'mail'& command"
3746 .cindex "dot" "in incoming non-SMTP message"
3747 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3748 line by itself should not terminate an incoming, non-SMTP message. I can find
3749 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3750 command in Solaris 2.4 uses it. See also &%-ti%&.
3751
3752 .vitem &%-L%&&~<&'tag'&>
3753 .oindex "&%-L%&"
3754 .cindex "syslog" "process name; set with flag"
3755 This option is equivalent to setting &%syslog_processname%& in the config
3756 file and setting &%log_file_path%& to &`syslog`&.
3757 Its use is restricted to administrators. The configuration file has to be
3758 read and parsed, to determine access rights, before this is set and takes
3759 effect, so early configuration file errors will not honour this flag.
3760
3761 The tag should not be longer than 32 characters.
3762
3763 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3764 .oindex "&%-M%&"
3765 .cindex "forcing delivery"
3766 .cindex "delivery" "forcing attempt"
3767 .cindex "frozen messages" "forcing delivery"
3768 This option requests Exim to run a delivery attempt on each message in turn. If
3769 any of the messages are frozen, they are automatically thawed before the
3770 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3771 and &%hold_domains%& are ignored.
3772
3773 Retry
3774 .cindex "hints database" "overriding retry hints"
3775 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3776 the normal retry time has not yet been reached. This option requires the caller
3777 to be an admin user. However, there is an option called &%prod_requires_admin%&
3778 which can be set false to relax this restriction (and also the same requirement
3779 for the &%-q%&, &%-R%&, and &%-S%& options).
3780
3781 The deliveries happen synchronously, that is, the original Exim process does
3782 not terminate until all the delivery attempts have finished. No output is
3783 produced unless there is a serious error. If you want to see what is happening,
3784 use the &%-v%& option as well, or inspect Exim's main log.
3785
3786 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3787 .oindex "&%-Mar%&"
3788 .cindex "message" "adding recipients"
3789 .cindex "recipient" "adding"
3790 This option requests Exim to add the addresses to the list of recipients of the
3791 message (&"ar"& for &"add recipients"&). The first argument must be a message
3792 id, and the remaining ones must be email addresses. However, if the message is
3793 active (in the middle of a delivery attempt), it is not altered. This option
3794 can be used only by an admin user.
3795
3796 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3797 &~<&'message&~id'&>"
3798 .oindex "&%-MC%&"
3799 .cindex "SMTP" "passed connection"
3800 .cindex "SMTP" "multiple deliveries"
3801 .cindex "multiple SMTP deliveries"
3802 This option is not intended for use by external callers. It is used internally
3803 by Exim to invoke another instance of itself to deliver a waiting message using
3804 an existing SMTP connection, which is passed as the standard input. Details are
3805 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3806 must be root or the Exim user in order to use it.
3807
3808 .vitem &%-MCA%&
3809 .oindex "&%-MCA%&"
3810 This option is not intended for use by external callers. It is used internally
3811 by Exim in conjunction with the &%-MC%& option. It signifies that the
3812 connection to the remote host has been authenticated.
3813
3814 .vitem &%-MCP%&
3815 .oindex "&%-MCP%&"
3816 This option is not intended for use by external callers. It is used internally
3817 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3818 which Exim is connected supports pipelining.
3819
3820 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3821 .oindex "&%-MCQ%&"
3822 This option is not intended for use by external callers. It is used internally
3823 by Exim in conjunction with the &%-MC%& option when the original delivery was
3824 started by a queue runner. It passes on the process id of the queue runner,
3825 together with the file descriptor number of an open pipe. Closure of the pipe
3826 signals the final completion of the sequence of processes that are passing
3827 messages through the same SMTP connection.
3828
3829 .vitem &%-MCS%&
3830 .oindex "&%-MCS%&"
3831 This option is not intended for use by external callers. It is used internally
3832 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3833 SMTP SIZE option should be used on messages delivered down the existing
3834 connection.
3835
3836 .vitem &%-MCT%&
3837 .oindex "&%-MCT%&"
3838 This option is not intended for use by external callers. It is used internally
3839 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3840 host to which Exim is connected supports TLS encryption.
3841
3842 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3843 .oindex "&%-Mc%&"
3844 .cindex "hints database" "not overridden by &%-Mc%&"
3845 .cindex "delivery" "manually started &-- not forced"
3846 This option requests Exim to run a delivery attempt on each message in turn,
3847 but unlike the &%-M%& option, it does check for retry hints, and respects any
3848 that are found. This option is not very useful to external callers. It is
3849 provided mainly for internal use by Exim when it needs to re-invoke itself in
3850 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3851 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3852 respects retry times and other options such as &%hold_domains%& that are
3853 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3854 If you want to run a specific delivery as if in a queue run, you should use
3855 &%-q%& with a message id argument. A distinction between queue run deliveries
3856 and other deliveries is made in one or two places.
3857
3858 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3859 .oindex "&%-Mes%&"
3860 .cindex "message" "changing sender"
3861 .cindex "sender" "changing"
3862 This option requests Exim to change the sender address in the message to the
3863 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3864 &"edit sender"&). There must be exactly two arguments. The first argument must
3865 be a message id, and the second one an email address. However, if the message
3866 is active (in the middle of a delivery attempt), its status is not altered.
3867 This option can be used only by an admin user.
3868
3869 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3870 .oindex "&%-Mf%&"
3871 .cindex "freezing messages"
3872 .cindex "message" "manually freezing"
3873 This option requests Exim to mark each listed message as &"frozen"&. This
3874 prevents any delivery attempts taking place until the message is &"thawed"&,
3875 either manually or as a result of the &%auto_thaw%& configuration option.
3876 However, if any of the messages are active (in the middle of a delivery
3877 attempt), their status is not altered. This option can be used only by an admin
3878 user.
3879
3880 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3881 .oindex "&%-Mg%&"
3882 .cindex "giving up on messages"
3883 .cindex "message" "abandoning delivery attempts"
3884 .cindex "delivery" "abandoning further attempts"
3885 This option requests Exim to give up trying to deliver the listed messages,
3886 including any that are frozen. However, if any of the messages are active,
3887 their status is not altered. For non-bounce messages, a delivery error message
3888 is sent to the sender, containing the text &"cancelled by administrator"&.
3889 Bounce messages are just discarded. This option can be used only by an admin
3890 user.
3891
3892 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3893 .oindex "&%-Mmad%&"
3894 .cindex "delivery" "cancelling all"
3895 This option requests Exim to mark all the recipient addresses in the messages
3896 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
3897 message is active (in the middle of a delivery attempt), its status is not
3898 altered. This option can be used only by an admin user.
3899
3900 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3901 .oindex "&%-Mmd%&"
3902 .cindex "delivery" "cancelling by address"
3903 .cindex "recipient" "removing"
3904 .cindex "removing recipients"
3905 This option requests Exim to mark the given addresses as already delivered
3906 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
3907 the remaining ones must be email addresses. These are matched to recipient
3908 addresses in the message in a case-sensitive manner. If the message is active
3909 (in the middle of a delivery attempt), its status is not altered. This option
3910 can be used only by an admin user.
3911
3912 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3913 .oindex "&%-Mrm%&"
3914 .cindex "removing messages"
3915 .cindex "abandoning mail"
3916 .cindex "message" "manually discarding"
3917 This option requests Exim to remove the given messages from the queue. No
3918 bounce messages are sent; each message is simply forgotten. However, if any of
3919 the messages are active, their status is not altered. This option can be used
3920 only by an admin user or by the user who originally caused the message to be
3921 placed on the queue.
3922
3923 .vitem &%-Mset%&&~<&'message&~id'&>
3924 .oindex "&%-Mset%&
3925 .cindex "testing" "string expansion"
3926 .cindex "expansion" "testing"
3927 This option is useful only in conjunction with &%-be%& (that is, when testing
3928 string expansions). Exim loads the given message from its spool before doing
3929 the test expansions, thus setting message-specific variables such as
3930 &$message_size$& and the header variables. The &$recipients$& variable is made
3931 available. This feature is provided to make it easier to test expansions that
3932 make use of these variables. However, this option can be used only by an admin
3933 user. See also &%-bem%&.
3934
3935 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3936 .oindex "&%-Mt%&"
3937 .cindex "thawing messages"
3938 .cindex "unfreezing messages"
3939 .cindex "frozen messages" "thawing"
3940 .cindex "message" "thawing frozen"
3941 This option requests Exim to &"thaw"& any of the listed messages that are
3942 &"frozen"&, so that delivery attempts can resume. However, if any of the
3943 messages are active, their status is not altered. This option can be used only
3944 by an admin user.
3945
3946 .vitem &%-Mvb%&&~<&'message&~id'&>
3947 .oindex "&%-Mvb%&"
3948 .cindex "listing" "message body"
3949 .cindex "message" "listing body of"
3950 This option causes the contents of the message body (-D) spool file to be
3951 written to the standard output. This option can be used only by an admin user.
3952
3953 .vitem &%-Mvc%&&~<&'message&~id'&>
3954 .oindex "&%-Mvc%&"
3955 .cindex "message" "listing in RFC 2822 format"
3956 .cindex "listing" "message in RFC 2822 format"
3957 This option causes a copy of the complete message (header lines plus body) to
3958 be written to the standard output in RFC 2822 format. This option can be used
3959 only by an admin user.
3960
3961 .vitem &%-Mvh%&&~<&'message&~id'&>
3962 .oindex "&%-Mvh%&"
3963 .cindex "listing" "message headers"
3964 .cindex "header lines" "listing"
3965 .cindex "message" "listing header lines"
3966 This option causes the contents of the message headers (-H) spool file to be
3967 written to the standard output. This option can be used only by an admin user.
3968
3969 .vitem &%-Mvl%&&~<&'message&~id'&>
3970 .oindex "&%-Mvl%&"
3971 .cindex "listing" "message log"
3972 .cindex "message" "listing message log"
3973 This option causes the contents of the message log spool file to be written to
3974 the standard output. This option can be used only by an admin user.
3975
3976 .vitem &%-m%&
3977 .oindex "&%-m%&"
3978 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
3979 treats it that way too.
3980
3981 .vitem &%-N%&
3982 .oindex "&%-N%&"
3983 .cindex "debugging" "&%-N%& option"
3984 .cindex "debugging" "suppressing delivery"
3985 This is a debugging option that inhibits delivery of a message at the transport
3986 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
3987 it just doesn't actually transport the message, but instead behaves as if it
3988 had successfully done so. However, it does not make any updates to the retry
3989 database, and the log entries for deliveries are flagged with &"*>"& rather
3990 than &"=>"&.
3991
3992 Because &%-N%& discards any message to which it applies, only root or the Exim
3993 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
3994 words, an ordinary user can use it only when supplying an incoming message to
3995 which it will apply. Although transportation never fails when &%-N%& is set, an
3996 address may be deferred because of a configuration problem on a transport, or a
3997 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
3998 the message, and applies to any subsequent delivery attempts that may happen
3999 for that message.
4000
4001 .vitem &%-n%&
4002 .oindex "&%-n%&"
4003 This option is interpreted by Sendmail to mean &"no aliasing"&.
4004 For normal modes of operation, it is ignored by Exim.
4005 When combined with &%-bP%& it suppresses the name of an option from being output.
4006
4007 .vitem &%-O%&&~<&'data'&>
4008 .oindex "&%-O%&"
4009 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4010 Exim.
4011
4012 .vitem &%-oA%&&~<&'file&~name'&>
4013 .oindex "&%-oA%&"
4014 .cindex "Sendmail compatibility" "&%-oA%& option"
4015 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4016 alternative alias file name. Exim handles &%-bi%& differently; see the
4017 description above.
4018
4019 .vitem &%-oB%&&~<&'n'&>
4020 .oindex "&%-oB%&"
4021 .cindex "SMTP" "passed connection"
4022 .cindex "SMTP" "multiple deliveries"
4023 .cindex "multiple SMTP deliveries"
4024 This is a debugging option which limits the maximum number of messages that can
4025 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4026 transport. If <&'n'&> is omitted, the limit is set to 1.
4027
4028 .vitem &%-odb%&
4029 .oindex "&%-odb%&"
4030 .cindex "background delivery"
4031 .cindex "delivery" "in the background"
4032 This option applies to all modes in which Exim accepts incoming messages,
4033 including the listening daemon. It requests &"background"& delivery of such
4034 messages, which means that the accepting process automatically starts a
4035 delivery process for each message received, but does not wait for the delivery
4036 processes to finish.
4037
4038 When all the messages have been received, the reception process exits,
4039 leaving the delivery processes to finish in their own time. The standard output
4040 and error streams are closed at the start of each delivery process.
4041 This is the default action if none of the &%-od%& options are present.
4042
4043 If one of the queueing options in the configuration file
4044 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4045 overrides it if &%queue_only_override%& is set true, which is the default
4046 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4047
4048 .vitem &%-odf%&
4049 .oindex "&%-odf%&"
4050 .cindex "foreground delivery"
4051 .cindex "delivery" "in the foreground"
4052 This option requests &"foreground"& (synchronous) delivery when Exim has
4053 accepted a locally-generated message. (For the daemon it is exactly the same as
4054 &%-odb%&.) A delivery process is automatically started to deliver the message,
4055 and Exim waits for it to complete before proceeding.
4056
4057 The original Exim reception process does not finish until the delivery
4058 process for the final message has ended. The standard error stream is left open
4059 during deliveries.
4060
4061 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4062 false and one of the queueing options in the configuration file is in effect.
4063
4064 If there is a temporary delivery error during foreground delivery, the
4065 message is left on the queue for later delivery, and the original reception
4066 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4067 restricted configuration that never queues messages.
4068
4069
4070 .vitem &%-odi%&
4071 .oindex "&%-odi%&"
4072 This option is synonymous with &%-odf%&. It is provided for compatibility with
4073 Sendmail.
4074
4075 .vitem &%-odq%&
4076 .oindex "&%-odq%&"
4077 .cindex "non-immediate delivery"
4078 .cindex "delivery" "suppressing immediate"
4079 .cindex "queueing incoming messages"
4080 This option applies to all modes in which Exim accepts incoming messages,
4081 including the listening daemon. It specifies that the accepting process should
4082 not automatically start a delivery process for each message received. Messages
4083 are placed on the queue, and remain there until a subsequent queue runner
4084 process encounters them. There are several configuration options (such as
4085 &%queue_only%&) that can be used to queue incoming messages under certain
4086 conditions. This option overrides all of them and also &%-odqs%&. It always
4087 forces queueing.
4088
4089 .vitem &%-odqs%&
4090 .oindex "&%-odqs%&"
4091 .cindex "SMTP" "delaying delivery"
4092 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4093 However, like &%-odb%& and &%-odi%&, this option has no effect if
4094 &%queue_only_override%& is false and one of the queueing options in the
4095 configuration file is in effect.
4096
4097 When &%-odqs%& does operate, a delivery process is started for each incoming
4098 message, in the background by default, but in the foreground if &%-odi%& is
4099 also present. The recipient addresses are routed, and local deliveries are done
4100 in the normal way. However, if any SMTP deliveries are required, they are not
4101 done at this time, so the message remains on the queue until a subsequent queue
4102 runner process encounters it. Because routing was done, Exim knows which
4103 messages are waiting for which hosts, and so a number of messages for the same
4104 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4105 configuration option has the same effect for specific domains. See also the
4106 &%-qq%& option.
4107
4108 .vitem &%-oee%&
4109 .oindex "&%-oee%&"
4110 .cindex "error" "reporting"
4111 If an error is detected while a non-SMTP message is being received (for
4112 example, a malformed address), the error is reported to the sender in a mail
4113 message.
4114
4115 .cindex "return code" "for &%-oee%&"
4116 Provided
4117 this error message is successfully sent, the Exim receiving process
4118 exits with a return code of zero. If not, the return code is 2 if the problem
4119 is that the original message has no recipients, or 1 for any other error.
4120 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4121
4122 .vitem &%-oem%&
4123 .oindex "&%-oem%&"
4124 .cindex "error" "reporting"
4125 .cindex "return code" "for &%-oem%&"
4126 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4127 return code, whether or not the error message was successfully sent.
4128 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4129
4130 .vitem &%-oep%&
4131 .oindex "&%-oep%&"
4132 .cindex "error" "reporting"
4133 If an error is detected while a non-SMTP message is being received, the
4134 error is reported by writing a message to the standard error file (stderr).
4135 .cindex "return code" "for &%-oep%&"
4136 The return code is 1 for all errors.
4137
4138 .vitem &%-oeq%&
4139 .oindex "&%-oeq%&"
4140 .cindex "error" "reporting"
4141 This option is supported for compatibility with Sendmail, but has the same
4142 effect as &%-oep%&.
4143
4144 .vitem &%-oew%&
4145 .oindex "&%-oew%&"
4146 .cindex "error" "reporting"
4147 This option is supported for compatibility with Sendmail, but has the same
4148 effect as &%-oem%&.
4149
4150 .vitem &%-oi%&
4151 .oindex "&%-oi%&"
4152 .cindex "dot" "in incoming non-SMTP message"
4153 This option, which has the same effect as &%-i%&, specifies that a dot on a
4154 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4155 single dot does terminate, though Exim does no special processing for other
4156 lines that start with a dot. This option is set by default if Exim is called as
4157 &'rmail'&. See also &%-ti%&.
4158
4159 .vitem &%-oitrue%&
4160 .oindex "&%-oitrue%&"
4161 This option is treated as synonymous with &%-oi%&.
4162
4163 .vitem &%-oMa%&&~<&'host&~address'&>
4164 .oindex "&%-oMa%&"
4165 .cindex "sender" "host address, specifying for local message"
4166 A number of options starting with &%-oM%& can be used to set values associated
4167 with remote hosts on locally-submitted messages (that is, messages not received
4168 over TCP/IP). These options can be used by any caller in conjunction with the
4169 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4170 other circumstances, they are ignored unless the caller is trusted.
4171
4172 The &%-oMa%& option sets the sender host address. This may include a port
4173 number at the end, after a full stop (period). For example:
4174 .code
4175 exim -bs -oMa 10.9.8.7.1234
4176 .endd
4177 An alternative syntax is to enclose the IP address in square brackets,
4178 followed by a colon and the port number:
4179 .code
4180 exim -bs -oMa [10.9.8.7]:1234
4181 .endd
4182 The IP address is placed in the &$sender_host_address$& variable, and the
4183 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4184 are present on the command line, the sender host IP address is taken from
4185 whichever one is last.
4186
4187 .vitem &%-oMaa%&&~<&'name'&>
4188 .oindex "&%-oMaa%&"
4189 .cindex "authentication" "name, specifying for local message"
4190 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4191 option sets the value of &$sender_host_authenticated$& (the authenticator
4192 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4193 This option can be used with &%-bh%& and &%-bs%& to set up an
4194 authenticated SMTP session without actually using the SMTP AUTH command.
4195
4196 .vitem &%-oMai%&&~<&'string'&>
4197 .oindex "&%-oMai%&"
4198 .cindex "authentication" "id, specifying for local message"
4199 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4200 option sets the value of &$authenticated_id$& (the id that was authenticated).
4201 This overrides the default value (the caller's login id, except with &%-bh%&,
4202 where there is no default) for messages from local sources. See chapter
4203 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4204
4205 .vitem &%-oMas%&&~<&'address'&>
4206 .oindex "&%-oMas%&"
4207 .cindex "authentication" "sender, specifying for local message"
4208 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4209 option sets the authenticated sender value in &$authenticated_sender$&. It
4210 overrides the sender address that is created from the caller's login id for
4211 messages from local sources, except when &%-bh%& is used, when there is no
4212 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4213 specified on a MAIL command overrides this value. See chapter
4214 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4215
4216 .vitem &%-oMi%&&~<&'interface&~address'&>
4217 .oindex "&%-oMi%&"
4218 .cindex "interface" "address, specifying for local message"
4219 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4220 option sets the IP interface address value. A port number may be included,
4221 using the same syntax as for &%-oMa%&. The interface address is placed in
4222 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4223
4224 .vitem &%-oMm%&&~<&'message&~reference'&>
4225 .oindex "&%-oMm%&"
4226 .cindex "message reference" "message reference, specifying for local message"
4227 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4228 option sets the message reference, e.g. message-id, and is logged during
4229 delivery. This is useful when some kind of audit trail is required to tie
4230 messages together. The format of the message reference is checked and will
4231 abort if the format is invalid. The option will only be accepted if exim is
4232 running in trusted mode, not as any regular user.
4233
4234 The best example of a message reference is when Exim sends a bounce message.
4235 The message reference is the message-id of the original message for which Exim
4236 is sending the bounce.
4237
4238 .vitem &%-oMr%&&~<&'protocol&~name'&>
4239 .oindex "&%-oMr%&"
4240 .cindex "protocol, specifying for local message"
4241 .vindex "&$received_protocol$&"
4242 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4243 option sets the received protocol value that is stored in
4244 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4245 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4246 SMTP protocol names (see the description of &$received_protocol$& in section
4247 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4248 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4249 be set by &%-oMr%&.
4250
4251 .vitem &%-oMs%&&~<&'host&~name'&>
4252 .oindex "&%-oMs%&"
4253 .cindex "sender" "host name, specifying for local message"
4254 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4255 option sets the sender host name in &$sender_host_name$&. When this option is
4256 present, Exim does not attempt to look up a host name from an IP address; it
4257 uses the name it is given.
4258
4259 .vitem &%-oMt%&&~<&'ident&~string'&>
4260 .oindex "&%-oMt%&"
4261 .cindex "sender" "ident string, specifying for local message"
4262 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4263 option sets the sender ident value in &$sender_ident$&. The default setting for
4264 local callers is the login id of the calling process, except when &%-bh%& is
4265 used, when there is no default.
4266
4267 .vitem &%-om%&
4268 .oindex "&%-om%&"
4269 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4270 In Sendmail, this option means &"me too"&, indicating that the sender of a
4271 message should receive a copy of the message if the sender appears in an alias
4272 expansion. Exim always does this, so the option does nothing.
4273
4274 .vitem &%-oo%&
4275 .oindex "&%-oo%&"
4276 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4277 This option is ignored. In Sendmail it specifies &"old style headers"&,
4278 whatever that means.
4279
4280 .vitem &%-oP%&&~<&'path'&>
4281 .oindex "&%-oP%&"
4282 .cindex "pid (process id)" "of daemon"
4283 .cindex "daemon" "process id (pid)"
4284 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4285 value. The option specifies the file to which the process id of the daemon is
4286 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4287 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4288 because in those cases, the normal pid file is not used.
4289
4290 .vitem &%-or%&&~<&'time'&>
4291 .oindex "&%-or%&"
4292 .cindex "timeout" "for non-SMTP input"
4293 This option sets a timeout value for incoming non-SMTP messages. If it is not
4294 set, Exim will wait forever for the standard input. The value can also be set
4295 by the &%receive_timeout%& option. The format used for specifying times is
4296 described in section &<<SECTtimeformat>>&.
4297
4298 .vitem &%-os%&&~<&'time'&>
4299 .oindex "&%-os%&"
4300 .cindex "timeout" "for SMTP input"
4301 .cindex "SMTP" "input timeout"
4302 This option sets a timeout value for incoming SMTP messages. The timeout
4303 applies to each SMTP command and block of data. The value can also be set by
4304 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4305 for specifying times is described in section &<<SECTtimeformat>>&.
4306
4307 .vitem &%-ov%&
4308 .oindex "&%-ov%&"
4309 This option has exactly the same effect as &%-v%&.
4310
4311 .vitem &%-oX%&&~<&'number&~or&~string'&>
4312 .oindex "&%-oX%&"
4313 .cindex "TCP/IP" "setting listening ports"
4314 .cindex "TCP/IP" "setting listening interfaces"
4315 .cindex "port" "receiving TCP/IP"
4316 This option is relevant only when the &%-bd%& (start listening daemon) option
4317 is also given. It controls which ports and interfaces the daemon uses. Details
4318 of the syntax, and how it interacts with configuration file options, are given
4319 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4320 file is written unless &%-oP%& is also present to specify a pid file name.
4321
4322 .vitem &%-pd%&
4323 .oindex "&%-pd%&"
4324 .cindex "Perl" "starting the interpreter"
4325 This option applies when an embedded Perl interpreter is linked with Exim (see
4326 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4327 option, forcing the starting of the interpreter to be delayed until it is
4328 needed.
4329
4330 .vitem &%-ps%&
4331 .oindex "&%-ps%&"
4332 .cindex "Perl" "starting the interpreter"
4333 This option applies when an embedded Perl interpreter is linked with Exim (see
4334 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4335 option, forcing the starting of the interpreter to occur as soon as Exim is
4336 started.
4337
4338 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4339 .oindex "&%-p%&"
4340 For compatibility with Sendmail, this option is equivalent to
4341 .display
4342 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4343 .endd
4344 It sets the incoming protocol and host name (for trusted callers). The
4345 host name and its colon can be omitted when only the protocol is to be set.
4346 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4347 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4348 or &`s`& using this option (but that does not seem a real limitation).
4349
4350 .vitem &%-q%&
4351 .oindex "&%-q%&"
4352 .cindex "queue runner" "starting manually"
4353 This option is normally restricted to admin users. However, there is a
4354 configuration option called &%prod_requires_admin%& which can be set false to
4355 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4356 and &%-S%& options).
4357
4358 .cindex "queue runner" "description of operation"
4359 The &%-q%& option starts one queue runner process. This scans the queue of
4360 waiting messages, and runs a delivery process for each one in turn. It waits
4361 for each delivery process to finish before starting the next one. A delivery
4362 process may not actually do any deliveries if the retry times for the addresses
4363 have not been reached. Use &%-qf%& (see below) if you want to override this.
4364
4365 If
4366 .cindex "SMTP" "passed connection"
4367 .cindex "SMTP" "multiple deliveries"
4368 .cindex "multiple SMTP deliveries"
4369 the delivery process spawns other processes to deliver other messages down
4370 passed SMTP connections, the queue runner waits for these to finish before
4371 proceeding.
4372
4373 When all the queued messages have been considered, the original queue runner
4374 process terminates. In other words, a single pass is made over the waiting
4375 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4376 this to be repeated periodically.
4377
4378 Exim processes the waiting messages in an unpredictable order. It isn't very
4379 random, but it is likely to be different each time, which is all that matters.
4380 If one particular message screws up a remote MTA, other messages to the same
4381 MTA have a chance of getting through if they get tried first.
4382
4383 It is possible to cause the messages to be processed in lexical message id
4384 order, which is essentially the order in which they arrived, by setting the
4385 &%queue_run_in_order%& option, but this is not recommended for normal use.
4386
4387 .vitem &%-q%&<&'qflags'&>
4388 The &%-q%& option may be followed by one or more flag letters that change its
4389 behaviour. They are all optional, but if more than one is present, they must
4390 appear in the correct order. Each flag is described in a separate item below.
4391
4392 .vitem &%-qq...%&
4393 .oindex "&%-qq%&"
4394 .cindex "queue" "double scanning"
4395 .cindex "queue" "routing"
4396 .cindex "routing" "whole queue before delivery"
4397 An option starting with &%-qq%& requests a two-stage queue run. In the first
4398 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4399 every domain. Addresses are routed, local deliveries happen, but no remote
4400 transports are run.
4401
4402 .cindex "hints database" "remembering routing"
4403 The hints database that remembers which messages are waiting for specific hosts
4404 is updated, as if delivery to those hosts had been deferred. After this is
4405 complete, a second, normal queue scan happens, with routing and delivery taking
4406 place as normal. Messages that are routed to the same host should mostly be
4407 delivered down a single SMTP
4408 .cindex "SMTP" "passed connection"
4409 .cindex "SMTP" "multiple deliveries"
4410 .cindex "multiple SMTP deliveries"
4411 connection because of the hints that were set up during the first queue scan.
4412 This option may be useful for hosts that are connected to the Internet
4413 intermittently.
4414
4415 .vitem &%-q[q]i...%&
4416 .oindex "&%-qi%&"
4417 .cindex "queue" "initial delivery"
4418 If the &'i'& flag is present, the queue runner runs delivery processes only for
4419 those messages that haven't previously been tried. (&'i'& stands for &"initial
4420 delivery"&.) This can be helpful if you are putting messages on the queue using
4421 &%-odq%& and want a queue runner just to process the new messages.
4422
4423 .vitem &%-q[q][i]f...%&
4424 .oindex "&%-qf%&"
4425 .cindex "queue" "forcing delivery"
4426 .cindex "delivery" "forcing in queue run"
4427 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4428 message, whereas without &'f'& only those non-frozen addresses that have passed
4429 their retry times are tried.
4430
4431 .vitem &%-q[q][i]ff...%&
4432 .oindex "&%-qff%&"
4433 .cindex "frozen messages" "forcing delivery"
4434 If &'ff'& is present, a delivery attempt is forced for every message, whether
4435 frozen or not.
4436
4437 .vitem &%-q[q][i][f[f]]l%&
4438 .oindex "&%-ql%&"
4439 .cindex "queue" "local deliveries only"
4440 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4441 be done. If a message requires any remote deliveries, it remains on the queue
4442 for later delivery.
4443
4444 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4445 .cindex "queue" "delivering specific messages"
4446 When scanning the queue, Exim can be made to skip over messages whose ids are
4447 lexically less than a given value by following the &%-q%& option with a
4448 starting message id. For example:
4449 .code
4450 exim -q 0t5C6f-0000c8-00
4451 .endd
4452 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4453 second message id is given, messages whose ids are lexically greater than it
4454 are also skipped. If the same id is given twice, for example,
4455 .code
4456 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4457 .endd
4458 just one delivery process is started, for that message. This differs from
4459 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4460 that it counts as a delivery from a queue run. Note that the selection
4461 mechanism does not affect the order in which the messages are scanned. There
4462 are also other ways of selecting specific sets of messages for delivery in a
4463 queue run &-- see &%-R%& and &%-S%&.
4464
4465 .vitem &%-q%&<&'qflags'&><&'time'&>
4466 .cindex "queue runner" "starting periodically"
4467 .cindex "periodic queue running"
4468 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4469 starting a queue runner process at intervals specified by the given time value
4470 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4471 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4472 single daemon process handles both functions. A common way of starting up a
4473 combined daemon at system boot time is to use a command such as
4474 .code
4475 /usr/exim/bin/exim -bd -q30m
4476 .endd
4477 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4478 process every 30 minutes.
4479
4480 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4481 pid file is written unless one is explicitly requested by the &%-oP%& option.
4482
4483 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4484 .oindex "&%-qR%&"
4485 This option is synonymous with &%-R%&. It is provided for Sendmail
4486 compatibility.
4487
4488 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4489 .oindex "&%-qS%&"
4490 This option is synonymous with &%-S%&.
4491
4492 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4493 .oindex "&%-R%&"
4494 .cindex "queue runner" "for specific recipients"
4495 .cindex "delivery" "to given domain"
4496 .cindex "domain" "delivery to"
4497 The <&'rsflags'&> may be empty, in which case the white space before the string
4498 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4499 which are the possible values for <&'rsflags'&>. White space is required if
4500 <&'rsflags'&> is not empty.
4501
4502 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4503 perform a single queue run, except that, when scanning the messages on the
4504 queue, Exim processes only those that have at least one undelivered recipient
4505 address containing the given string, which is checked in a case-independent
4506 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4507 regular expression; otherwise it is a literal string.
4508
4509 If you want to do periodic queue runs for messages with specific recipients,
4510 you can combine &%-R%& with &%-q%& and a time value. For example:
4511 .code
4512 exim -q25m -R @special.domain.example
4513 .endd
4514 This example does a queue run for messages with recipients in the given domain
4515 every 25 minutes. Any additional flags that are specified with &%-q%& are
4516 applied to each queue run.
4517
4518 Once a message is selected for delivery by this mechanism, all its addresses
4519 are processed. For the first selected message, Exim overrides any retry
4520 information and forces a delivery attempt for each undelivered address. This
4521 means that if delivery of any address in the first message is successful, any
4522 existing retry information is deleted, and so delivery attempts for that
4523 address in subsequently selected messages (which are processed without forcing)
4524 will run. However, if delivery of any address does not succeed, the retry
4525 information is updated, and in subsequently selected messages, the failing
4526 address will be skipped.
4527
4528 .cindex "frozen messages" "forcing delivery"
4529 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4530 all selected messages, not just the first; frozen messages are included when
4531 &'ff'& is present.
4532
4533 The &%-R%& option makes it straightforward to initiate delivery of all messages
4534 to a given domain after a host has been down for some time. When the SMTP
4535 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4536 effect is to run Exim with the &%-R%& option, but it can be configured to run
4537 an arbitrary command instead.
4538
4539 .vitem &%-r%&
4540 .oindex "&%-r%&"
4541 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4542
4543 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4544 .oindex "&%-S%&"
4545 .cindex "delivery" "from given sender"
4546 .cindex "queue runner" "for specific senders"
4547 This option acts like &%-R%& except that it checks the string against each
4548 message's sender instead of against the recipients. If &%-R%& is also set, both
4549 conditions must be met for a message to be selected. If either of the options
4550 has &'f'& or &'ff'& in its flags, the associated action is taken.
4551
4552 .vitem &%-Tqt%&&~<&'times'&>
4553 .oindex "&%-Tqt%&"
4554 This is an option that is exclusively for use by the Exim testing suite. It is not
4555 recognized when Exim is run normally. It allows for the setting up of explicit
4556 &"queue times"& so that various warning/retry features can be tested.
4557
4558 .vitem &%-t%&
4559 .oindex "&%-t%&"
4560 .cindex "recipient" "extracting from header lines"
4561 .cindex "&'Bcc:'& header line"
4562 .cindex "&'Cc:'& header line"
4563 .cindex "&'To:'& header line"
4564 When Exim is receiving a locally-generated, non-SMTP message on its standard
4565 input, the &%-t%& option causes the recipients of the message to be obtained
4566 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4567 from the command arguments. The addresses are extracted before any rewriting
4568 takes place and the &'Bcc:'& header line, if present, is then removed.
4569
4570 .cindex "Sendmail compatibility" "&%-t%& option"
4571 If the command has any arguments, they specify addresses to which the message
4572 is &'not'& to be delivered. That is, the argument addresses are removed from
4573 the recipients list obtained from the headers. This is compatible with Smail 3
4574 and in accordance with the documented behaviour of several versions of
4575 Sendmail, as described in man pages on a number of operating systems (e.g.
4576 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4577 argument addresses to those obtained from the headers, and the O'Reilly
4578 Sendmail book documents it that way. Exim can be made to add argument addresses
4579 instead of subtracting them by setting the option
4580 &%extract_addresses_remove_arguments%& false.
4581
4582 .cindex "&%Resent-%& header lines" "with &%-t%&"
4583 If there are any &%Resent-%& header lines in the message, Exim extracts
4584 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4585 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4586 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4587 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4588
4589 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4590 message is resent several times). The RFC also specifies that they should be
4591 added at the front of the message, and separated by &'Received:'& lines. It is
4592 not at all clear how &%-t%& should operate in the present of multiple sets,
4593 nor indeed exactly what constitutes a &"set"&.
4594 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4595 are often added at the end of the header, and if a message is resent more than
4596 once, it is common for the original set of &%Resent-%& headers to be renamed as
4597 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4598
4599 .vitem &%-ti%&
4600 .oindex "&%-ti%&"
4601 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4602 compatibility with Sendmail.
4603
4604 .vitem &%-tls-on-connect%&
4605 .oindex "&%-tls-on-connect%&"
4606 .cindex "TLS" "use without STARTTLS"
4607 .cindex "TLS" "automatic start"
4608 This option is available when Exim is compiled with TLS support. It forces all
4609 incoming SMTP connections to behave as if the incoming port is listed in the
4610 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4611 &<<CHAPTLS>>& for further details.
4612
4613
4614 .vitem &%-U%&
4615 .oindex "&%-U%&"
4616 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4617 Sendmail uses this option for &"initial message submission"&, and its
4618 documentation states that in future releases, it may complain about
4619 syntactically invalid messages rather than fixing them when this flag is not
4620 set. Exim ignores this option.
4621
4622 .vitem &%-v%&
4623 .oindex "&%-v%&"
4624 This option causes Exim to write information to the standard error stream,
4625 describing what it is doing. In particular, it shows the log lines for
4626 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4627 dialogue is shown. Some of the log lines shown may not actually be written to
4628 the log if the setting of &%log_selector%& discards them. Any relevant
4629 selectors are shown with each log line. If none are shown, the logging is
4630 unconditional.
4631
4632 .vitem &%-x%&
4633 .oindex "&%-x%&"
4634 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4635 National Language Support extended characters in the body of the mail item"&).
4636 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4637 this option.
4638
4639 .vitem &%-X%&&~<&'logfile'&>
4640 .oindex "&%-X%&"
4641 This option is interpreted by Sendmail to cause debug information to be sent
4642 to the named file. It is ignored by Exim.
4643 .endlist
4644
4645 .ecindex IIDclo1
4646 .ecindex IIDclo2
4647
4648
4649 . ////////////////////////////////////////////////////////////////////////////
4650 . Insert a stylized DocBook comment here, to identify the end of the command
4651 . line options. This is for the benefit of the Perl script that automatically
4652 . creates a man page for the options.
4653 . ////////////////////////////////////////////////////////////////////////////
4654
4655 .literal xml
4656 <!-- === End of command line options === -->
4657 .literal off
4658
4659
4660
4661
4662
4663 . ////////////////////////////////////////////////////////////////////////////
4664 . ////////////////////////////////////////////////////////////////////////////
4665
4666
4667 .chapter "The Exim run time configuration file" "CHAPconf" &&&
4668 "The runtime configuration file"
4669
4670 .cindex "run time configuration"
4671 .cindex "configuration file" "general description"
4672 .cindex "CONFIGURE_FILE"
4673 .cindex "configuration file" "errors in"
4674 .cindex "error" "in configuration file"
4675 .cindex "return code" "for bad configuration"
4676 Exim uses a single run time configuration file that is read whenever an Exim
4677 binary is executed. Note that in normal operation, this happens frequently,
4678 because Exim is designed to operate in a distributed manner, without central
4679 control.
4680
4681 If a syntax error is detected while reading the configuration file, Exim
4682 writes a message on the standard error, and exits with a non-zero return code.
4683 The message is also written to the panic log. &*Note*&: Only simple syntax
4684 errors can be detected at this time. The values of any expanded options are
4685 not checked until the expansion happens, even when the expansion does not
4686 actually alter the string.
4687
4688 The name of the configuration file is compiled into the binary for security
4689 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4690 most configurations, this specifies a single file. However, it is permitted to
4691 give a colon-separated list of file names, in which case Exim uses the first
4692 existing file in the list.
4693
4694 .cindex "EXIM_USER"
4695 .cindex "EXIM_GROUP"
4696 .cindex "CONFIGURE_OWNER"
4697 .cindex "CONFIGURE_GROUP"
4698 .cindex "configuration file" "ownership"
4699 .cindex "ownership" "configuration file"
4700 The run time configuration file must be owned by root or by the user that is
4701 specified at compile time by the CONFIGURE_OWNER option (if set). The
4702 configuration file must not be world-writeable, or group-writeable unless its
4703 group is the root group or the one specified at compile time by the
4704 CONFIGURE_GROUP option.
4705
4706 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4707 to root, anybody who is able to edit the run time configuration file has an
4708 easy way to run commands as root. If you specify a user or group in the
4709 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4710 who are members of that group will trivially be able to obtain root privileges.
4711
4712 Up to Exim version 4.72, the run time configuration file was also permitted to
4713 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4714 since it offered a simple privilege escalation for any attacker who managed to
4715 compromise the Exim user account.
4716
4717 A default configuration file, which will work correctly in simple situations,
4718 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4719 defines just one file name, the installation process copies the default
4720 configuration to a new file of that name if it did not previously exist. If
4721 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4722 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4723 configuration.
4724
4725
4726
4727 .section "Using a different configuration file" "SECID40"
4728 .cindex "configuration file" "alternate"
4729 A one-off alternate configuration can be specified by the &%-C%& command line
4730 option, which may specify a single file or a list of files. However, when
4731 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4732 unless the argument for &%-C%& is identical to the built-in value from
4733 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4734 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4735 is useful mainly for checking the syntax of configuration files before
4736 installing them. No owner or group checks are done on a configuration file
4737 specified by &%-C%&, if root privilege has been dropped.
4738
4739 Even the Exim user is not trusted to specify an arbitrary configuration file
4740 with the &%-C%& option to be used with root privileges, unless that file is
4741 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
4742 testing a configuration using &%-C%& right through message reception and
4743 delivery, even if the caller is root. The reception works, but by that time,
4744 Exim is running as the Exim user, so when it re-execs to regain privilege for
4745 the delivery, the use of &%-C%& causes privilege to be lost. However, root
4746 can test reception and delivery using two separate commands (one to put a
4747 message on the queue, using &%-odq%&, and another to do the delivery, using
4748 &%-M%&).
4749
4750 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4751 prefix string with which any file named in a &%-C%& command line option must
4752 start. In addition, the file name must not contain the sequence &"&`/../`&"&.
4753 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any file
4754 name can be used with &%-C%&.
4755
4756 One-off changes to a configuration can be specified by the &%-D%& command line
4757 option, which defines and overrides values for macros used inside the
4758 configuration file. However, like &%-C%&, the use of this option by a
4759 non-privileged user causes Exim to discard its root privilege.
4760 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4761 completely disabled, and its use causes an immediate error exit.
4762
4763 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
4764 to declare certain macro names trusted, such that root privilege will not
4765 necessarily be discarded.
4766 WHITELIST_D_MACROS defines a colon-separated list of macros which are
4767 considered safe and, if &%-D%& only supplies macros from this list, and the
4768 values are acceptable, then Exim will not give up root privilege if the caller
4769 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
4770 transition mechanism and is expected to be removed in the future. Acceptable
4771 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
4772
4773 Some sites may wish to use the same Exim binary on different machines that
4774 share a file system, but to use different configuration files on each machine.
4775 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4776 looks for a file whose name is the configuration file name followed by a dot
4777 and the machine's node name, as obtained from the &[uname()]& function. If this
4778 file does not exist, the standard name is tried. This processing occurs for
4779 each file name in the list given by CONFIGURE_FILE or &%-C%&.
4780
4781 In some esoteric situations different versions of Exim may be run under
4782 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4783 help with this. See the comments in &_src/EDITME_& for details.
4784
4785
4786
4787 .section "Configuration file format" "SECTconffilfor"
4788 .cindex "configuration file" "format of"
4789 .cindex "format" "configuration file"
4790 Exim's configuration file is divided into a number of different parts. General
4791 option settings must always appear at the start of the file. The other parts
4792 are all optional, and may appear in any order. Each part other than the first
4793 is introduced by the word &"begin"& followed by the name of the part. The
4794 optional parts are:
4795
4796 .ilist
4797 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
4798 &<<CHAPACL>>&).
4799 .next
4800 .cindex "AUTH" "configuration"
4801 &'authenticators'&: Configuration settings for the authenticator drivers. These
4802 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4803 .next
4804 &'routers'&: Configuration settings for the router drivers. Routers process
4805 addresses and determine how the message is to be delivered (see chapters
4806 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
4807 .next
4808 &'transports'&: Configuration settings for the transport drivers. Transports
4809 define mechanisms for copying messages to destinations (see chapters
4810 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
4811 .next
4812 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
4813 If there is no retry section, or if it is empty (that is, no retry rules are
4814 defined), Exim will not retry deliveries. In this situation, temporary errors
4815 are treated the same as permanent errors. Retry rules are discussed in chapter
4816 &<<CHAPretry>>&.
4817 .next
4818 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4819 when new addresses are generated during delivery. Rewriting is discussed in
4820 chapter &<<CHAPrewrite>>&.
4821 .next
4822 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4823 want to use this feature, you must set
4824 .code
4825 LOCAL_SCAN_HAS_OPTIONS=yes
4826 .endd
4827 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
4828 facility are given in chapter &<<CHAPlocalscan>>&.
4829 .endlist
4830
4831 .cindex "configuration file" "leading white space in"
4832 .cindex "configuration file" "trailing white space in"
4833 .cindex "white space" "in configuration file"
4834 Leading and trailing white space in configuration lines is always ignored.
4835
4836 Blank lines in the file, and lines starting with a # character (ignoring
4837 leading white space) are treated as comments and are ignored. &*Note*&: A
4838 # character other than at the beginning of a line is not treated specially,
4839 and does not introduce a comment.
4840
4841 Any non-comment line can be continued by ending it with a backslash. Note that
4842 the general rule for white space means that trailing white space after the
4843 backslash and leading white space at the start of continuation
4844 lines is ignored. Comment lines beginning with # (but not empty lines) may
4845 appear in the middle of a sequence of continuation lines.
4846
4847 A convenient way to create a configuration file is to start from the
4848 default, which is supplied in &_src/configure.default_&, and add, delete, or
4849 change settings as required.
4850
4851 The ACLs, retry rules, and rewriting rules have their own syntax which is
4852 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
4853 respectively. The other parts of the configuration file have some syntactic
4854 items in common, and these are described below, from section &<<SECTcos>>&
4855 onwards. Before that, the inclusion, macro, and conditional facilities are
4856 described.
4857
4858
4859
4860 .section "File inclusions in the configuration file" "SECID41"
4861 .cindex "inclusions in configuration file"
4862 .cindex "configuration file" "including other files"
4863 .cindex "&`.include`& in configuration file"
4864 .cindex "&`.include_if_exists`& in configuration file"
4865 You can include other files inside Exim's run time configuration file by
4866 using this syntax:
4867 .display
4868 &`.include`& <&'file name'&>
4869 &`.include_if_exists`& <&'file name'&>
4870 .endd
4871 on a line by itself. Double quotes round the file name are optional. If you use
4872 the first form, a configuration error occurs if the file does not exist; the
4873 second form does nothing for non-existent files. In all cases, an absolute file
4874 name is required.
4875
4876 Includes may be nested to any depth, but remember that Exim reads its
4877 configuration file often, so it is a good idea to keep them to a minimum.
4878 If you change the contents of an included file, you must HUP the daemon,
4879 because an included file is read only when the configuration itself is read.
4880
4881 The processing of inclusions happens early, at a physical line level, so, like
4882 comment lines, an inclusion can be used in the middle of an option setting,
4883 for example:
4884 .code
4885 hosts_lookup = a.b.c \
4886 .include /some/file
4887 .endd
4888 Include processing happens after macro processing (see below). Its effect is to
4889 process the lines of the included file as if they occurred inline where the
4890 inclusion appears.
4891
4892
4893
4894 .section "Macros in the configuration file" "SECTmacrodefs"
4895 .cindex "macro" "description of"
4896 .cindex "configuration file" "macros"
4897 If a line in the main part of the configuration (that is, before the first
4898 &"begin"& line) begins with an upper case letter, it is taken as a macro
4899 definition, and must be of the form
4900 .display
4901 <&'name'&> = <&'rest of line'&>
4902 .endd
4903 The name must consist of letters, digits, and underscores, and need not all be
4904 in upper case, though that is recommended. The rest of the line, including any
4905 continuations, is the replacement text, and has leading and trailing white
4906 space removed. Quotes are not removed. The replacement text can never end with
4907 a backslash character, but this doesn't seem to be a serious limitation.
4908
4909 Macros may also be defined between router, transport, authenticator, or ACL
4910 definitions. They may not, however, be defined within an individual driver or
4911 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
4912
4913 .section "Macro substitution" "SECID42"
4914 Once a macro is defined, all subsequent lines in the file (and any included
4915 files) are scanned for the macro name; if there are several macros, the line is
4916 scanned for each in turn, in the order in which the macros are defined. The
4917 replacement text is not re-scanned for the current macro, though it is scanned
4918 for subsequently defined macros. For this reason, a macro name may not contain
4919 the name of a previously defined macro as a substring. You could, for example,
4920 define
4921 .display
4922 &`ABCD_XYZ = `&<&'something'&>
4923 &`ABCD = `&<&'something else'&>
4924 .endd
4925 but putting the definitions in the opposite order would provoke a configuration
4926 error. Macro expansion is applied to individual physical lines from the file,
4927 before checking for line continuation or file inclusion (see above). If a line
4928 consists solely of a macro name, and the expansion of the macro is empty, the
4929 line is ignored. A macro at the start of a line may turn the line into a
4930 comment line or a &`.include`& line.
4931
4932
4933 .section "Redefining macros" "SECID43"
4934 Once defined, the value of a macro can be redefined later in the configuration
4935 (or in an included file). Redefinition is specified by using &'=='& instead of
4936 &'='&. For example:
4937 .code
4938 MAC = initial value
4939 ...
4940 MAC == updated value
4941 .endd
4942 Redefinition does not alter the order in which the macros are applied to the
4943 subsequent lines of the configuration file. It is still the same order in which
4944 the macros were originally defined. All that changes is the macro's value.
4945 Redefinition makes it possible to accumulate values. For example:
4946 .code
4947 MAC = initial value
4948 ...
4949 MAC == MAC and something added
4950 .endd
4951 This can be helpful in situations where the configuration file is built
4952 from a number of other files.
4953
4954 .section "Overriding macro values" "SECID44"
4955 The values set for macros in the configuration file can be overridden by the
4956 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
4957 used, unless called by root or the Exim user. A definition on the command line
4958 using the &%-D%& option causes all definitions and redefinitions within the
4959 file to be ignored.
4960
4961
4962
4963 .section "Example of macro usage" "SECID45"
4964 As an example of macro usage, consider a configuration where aliases are looked
4965 up in a MySQL database. It helps to keep the file less cluttered if long
4966 strings such as SQL statements are defined separately as macros, for example:
4967 .code
4968 ALIAS_QUERY = select mailbox from user where \
4969 login='${quote_mysql:$local_part}';
4970 .endd
4971 This can then be used in a &(redirect)& router setting like this:
4972 .code
4973 data = ${lookup mysql{ALIAS_QUERY}}
4974 .endd
4975 In earlier versions of Exim macros were sometimes used for domain, host, or
4976 address lists. In Exim 4 these are handled better by named lists &-- see
4977 section &<<SECTnamedlists>>&.
4978
4979
4980 .section "Conditional skips in the configuration file" "SECID46"
4981 .cindex "configuration file" "conditional skips"
4982 .cindex "&`.ifdef`&"
4983 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
4984 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
4985 portions of the configuration file. The processing happens whenever the file is
4986 read (that is, when an Exim binary starts to run).
4987
4988 The implementation is very simple. Instances of the first four directives must
4989 be followed by text that includes the names of one or macros. The condition
4990 that is tested is whether or not any macro substitution has taken place in the
4991 line. Thus:
4992 .code
4993 .ifdef AAA
4994 message_size_limit = 50M
4995 .else
4996 message_size_limit = 100M
4997 .endif
4998 .endd
4999 sets a message size limit of 50M if the macro &`AAA`& is defined, and 100M
5000 otherwise. If there is more than one macro named on the line, the condition
5001 is true if any of them are defined. That is, it is an &"or"& condition. To
5002 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5003
5004 Although you can use a macro expansion to generate one of these directives,
5005 it is not very useful, because the condition &"there was a macro substitution
5006 in this line"& will always be true.
5007
5008 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5009 to clarify complicated nestings.
5010
5011
5012
5013 .section "Common option syntax" "SECTcos"
5014 .cindex "common option syntax"
5015 .cindex "syntax of common options"
5016 .cindex "configuration file" "common option syntax"
5017 For the main set of options, driver options, and &[local_scan()]& options,
5018 each setting is on a line by itself, and starts with a name consisting of
5019 lower-case letters and underscores. Many options require a data value, and in
5020 these cases the name must be followed by an equals sign (with optional white
5021 space) and then the value. For example:
5022 .code
5023 qualify_domain = mydomain.example.com
5024 .endd
5025 .cindex "hiding configuration option values"
5026 .cindex "configuration options" "hiding value of"
5027 .cindex "options" "hiding value of"
5028 Some option settings may contain sensitive data, for example, passwords for
5029 accessing databases. To stop non-admin users from using the &%-bP%& command
5030 line option to read these values, you can precede the option settings with the
5031 word &"hide"&. For example:
5032 .code
5033 hide mysql_servers = localhost/users/admin/secret-password
5034 .endd
5035 For non-admin users, such options are displayed like this:
5036 .code
5037 mysql_servers = <value not displayable>
5038 .endd
5039 If &"hide"& is used on a driver option, it hides the value of that option on
5040 all instances of the same driver.
5041
5042 The following sections describe the syntax used for the different data types
5043 that are found in option settings.
5044
5045
5046 .section "Boolean options" "SECID47"
5047 .cindex "format" "boolean"
5048 .cindex "boolean configuration values"
5049 .oindex "&%no_%&&'xxx'&"
5050 .oindex "&%not_%&&'xxx'&"
5051 Options whose type is given as boolean are on/off switches. There are two
5052 different ways of specifying such options: with and without a data value. If
5053 the option name is specified on its own without data, the switch is turned on;
5054 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5055 boolean options may be followed by an equals sign and one of the words
5056 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5057 the following two settings have exactly the same effect:
5058 .code
5059 queue_only
5060 queue_only = true
5061 .endd
5062 The following two lines also have the same (opposite) effect:
5063 .code
5064 no_queue_only
5065 queue_only = false
5066 .endd
5067 You can use whichever syntax you prefer.
5068
5069
5070
5071
5072 .section "Integer values" "SECID48"
5073 .cindex "integer configuration values"
5074 .cindex "format" "integer"
5075 If an option's type is given as &"integer"&, the value can be given in decimal,
5076 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5077 number is assumed. Otherwise, it is treated as an octal number unless it starts
5078 with the characters &"0x"&, in which case the remainder is interpreted as a
5079 hexadecimal number.
5080
5081 If an integer value is followed by the letter K, it is multiplied by 1024; if
5082 it is followed by the letter M, it is multiplied by 1024x1024. When the values
5083 of integer option settings are output, values which are an exact multiple of
5084 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5085 and M. The printing style is independent of the actual input format that was
5086 used.
5087
5088
5089 .section "Octal integer values" "SECID49"
5090 .cindex "integer format"
5091 .cindex "format" "octal integer"
5092 If an option's type is given as &"octal integer"&, its value is always
5093 interpreted as an octal number, whether or not it starts with the digit zero.
5094 Such options are always output in octal.
5095
5096
5097 .section "Fixed point numbers" "SECID50"
5098 .cindex "fixed point configuration values"
5099 .cindex "format" "fixed point"
5100 If an option's type is given as &"fixed-point"&, its value must be a decimal
5101 integer, optionally followed by a decimal point and up to three further digits.
5102
5103
5104
5105 .section "Time intervals" "SECTtimeformat"
5106 .cindex "time interval" "specifying in configuration"
5107 .cindex "format" "time interval"
5108 A time interval is specified as a sequence of numbers, each followed by one of
5109 the following letters, with no intervening white space:
5110
5111 .table2 30pt
5112 .irow &%s%& seconds
5113 .irow &%m%& minutes
5114 .irow &%h%& hours
5115 .irow &%d%& days
5116 .irow &%w%& weeks
5117 .endtable
5118
5119 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5120 intervals are output in the same format. Exim does not restrict the values; it
5121 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5122
5123
5124
5125 .section "String values" "SECTstrings"
5126 .cindex "string" "format of configuration values"
5127 .cindex "format" "string"
5128 If an option's type is specified as &"string"&, the value can be specified with
5129 or without double-quotes. If it does not start with a double-quote, the value
5130 consists of the remainder of the line plus any continuation lines, starting at
5131 the first character after any leading white space, with trailing white space
5132 removed, and with no interpretation of the characters in the string. Because
5133 Exim removes comment lines (those beginning with #) at an early stage, they can
5134 appear in the middle of a multi-line string. The following two settings are
5135 therefore equivalent:
5136 .code
5137 trusted_users = uucp:mail
5138 trusted_users = uucp:\
5139 # This comment line is ignored
5140 mail
5141 .endd
5142 .cindex "string" "quoted"
5143 .cindex "escape characters in quoted strings"
5144 If a string does start with a double-quote, it must end with a closing
5145 double-quote, and any backslash characters other than those used for line
5146 continuation are interpreted as escape characters, as follows:
5147
5148 .table2 100pt
5149 .irow &`\\`& "single backslash"
5150 .irow &`\n`& "newline"
5151 .irow &`\r`& "carriage return"
5152 .irow &`\t`& "tab"
5153 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5154 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5155 character"
5156 .endtable
5157
5158 If a backslash is followed by some other character, including a double-quote
5159 character, that character replaces the pair.
5160
5161 Quoting is necessary only if you want to make use of the backslash escapes to
5162 insert special characters, or if you need to specify a value with leading or
5163 trailing spaces. These cases are rare, so quoting is almost never needed in
5164 current versions of Exim. In versions of Exim before 3.14, quoting was required
5165 in order to continue lines, so you may come across older configuration files
5166 and examples that apparently quote unnecessarily.
5167
5168
5169 .section "Expanded strings" "SECID51"
5170 .cindex "expansion" "definition of"
5171 Some strings in the configuration file are subjected to &'string expansion'&,
5172 by which means various parts of the string may be changed according to the
5173 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5174 is as just described; in particular, the handling of backslashes in quoted
5175 strings is done as part of the input process, before expansion takes place.
5176 However, backslash is also an escape character for the expander, so any
5177 backslashes that are required for that reason must be doubled if they are
5178 within a quoted configuration string.
5179
5180
5181 .section "User and group names" "SECID52"
5182 .cindex "user name" "format of"
5183 .cindex "format" "user name"
5184 .cindex "groups" "name format"
5185 .cindex "format" "group name"
5186 User and group names are specified as strings, using the syntax described
5187 above, but the strings are interpreted specially. A user or group name must
5188 either consist entirely of digits, or be a name that can be looked up using the
5189 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5190
5191
5192 .section "List construction" "SECTlistconstruct"
5193 .cindex "list" "syntax of in configuration"
5194 .cindex "format" "list item in configuration"
5195 .cindex "string" "list, definition of"
5196 The data for some configuration options is a list of items, with colon as the
5197 default separator. Many of these options are shown with type &"string list"& in
5198 the descriptions later in this document. Others are listed as &"domain list"&,
5199 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5200 are all the same; however, those other than &"string list"& are subject to
5201 particular kinds of interpretation, as described in chapter
5202 &<<CHAPdomhosaddlists>>&.
5203
5204 In all these cases, the entire list is treated as a single string as far as the
5205 input syntax is concerned. The &%trusted_users%& setting in section
5206 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5207 in a list, it must be entered as two colons. Leading and trailing white space
5208 on each item in a list is ignored. This makes it possible to include items that
5209 start with a colon, and in particular, certain forms of IPv6 address. For
5210 example, the list
5211 .code
5212 local_interfaces = 127.0.0.1 : ::::1
5213 .endd
5214 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5215
5216 &*Note*&: Although leading and trailing white space is ignored in individual
5217 list items, it is not ignored when parsing the list. The space after the first
5218 colon in the example above is necessary. If it were not there, the list would
5219 be interpreted as the two items 127.0.0.1:: and 1.
5220
5221 .section "Changing list separators" "SECID53"
5222 .cindex "list separator" "changing"
5223 .cindex "IPv6" "addresses in lists"
5224 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5225 introduced to allow the separator character to be changed. If a list begins
5226 with a left angle bracket, followed by any punctuation character, that
5227 character is used instead of colon as the list separator. For example, the list
5228 above can be rewritten to use a semicolon separator like this:
5229 .code
5230 local_interfaces = <; 127.0.0.1 ; ::1
5231 .endd
5232 This facility applies to all lists, with the exception of the list in
5233 &%log_file_path%&. It is recommended that the use of non-colon separators be
5234 confined to circumstances where they really are needed.
5235
5236 .cindex "list separator" "newline as"
5237 .cindex "newline" "as list separator"
5238 It is also possible to use newline and other control characters (those with
5239 code values less than 32, plus DEL) as separators in lists. Such separators
5240 must be provided literally at the time the list is processed. For options that
5241 are string-expanded, you can write the separator using a normal escape
5242 sequence. This will be processed by the expander before the string is
5243 interpreted as a list. For example, if a newline-separated list of domains is
5244 generated by a lookup, you can process it directly by a line such as this:
5245 .code
5246 domains = <\n ${lookup mysql{.....}}
5247 .endd
5248 This avoids having to change the list separator in such data. You are unlikely
5249 to want to use a control character as a separator in an option that is not
5250 expanded, because the value is literal text. However, it can be done by giving
5251 the value in quotes. For example:
5252 .code
5253 local_interfaces = "<\n 127.0.0.1 \n ::1"
5254 .endd
5255 Unlike printing character separators, which can be included in list items by
5256 doubling, it is not possible to include a control character as data when it is
5257 set as the separator. Two such characters in succession are interpreted as
5258 enclosing an empty list item.
5259
5260
5261
5262 .section "Empty items in lists" "SECTempitelis"
5263 .cindex "list" "empty item in"
5264 An empty item at the end of a list is always ignored. In other words, trailing
5265 separator characters are ignored. Thus, the list in
5266 .code
5267 senders = user@domain :
5268 .endd
5269 contains only a single item. If you want to include an empty string as one item
5270 in a list, it must not be the last item. For example, this list contains three
5271 items, the second of which is empty:
5272 .code
5273 senders = user1@domain : : user2@domain
5274 .endd
5275 &*Note*&: There must be white space between the two colons, as otherwise they
5276 are interpreted as representing a single colon data character (and the list
5277 would then contain just one item). If you want to specify a list that contains
5278 just one, empty item, you can do it as in this example:
5279 .code
5280 senders = :
5281 .endd
5282 In this case, the first item is empty, and the second is discarded because it
5283 is at the end of the list.
5284
5285
5286
5287
5288 .section "Format of driver configurations" "SECTfordricon"
5289 .cindex "drivers" "configuration format"
5290 There are separate parts in the configuration for defining routers, transports,
5291 and authenticators. In each part, you are defining a number of driver
5292 instances, each with its own set of options. Each driver instance is defined by
5293 a sequence of lines like this:
5294 .display
5295 <&'instance name'&>:
5296 <&'option'&>
5297 ...
5298 <&'option'&>
5299 .endd
5300 In the following example, the instance name is &(localuser)&, and it is
5301 followed by three options settings:
5302 .code
5303 localuser:
5304 driver = accept
5305 check_local_user
5306 transport = local_delivery
5307 .endd
5308 For each driver instance, you specify which Exim code module it uses &-- by the
5309 setting of the &%driver%& option &-- and (optionally) some configuration
5310 settings. For example, in the case of transports, if you want a transport to
5311 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5312 a local file you would use the &(appendfile)& driver. Each of the drivers is
5313 described in detail in its own separate chapter later in this manual.
5314
5315 You can have several routers, transports, or authenticators that are based on
5316 the same underlying driver (each must have a different instance name).
5317
5318 The order in which routers are defined is important, because addresses are
5319 passed to individual routers one by one, in order. The order in which
5320 transports are defined does not matter at all. The order in which
5321 authenticators are defined is used only when Exim, as a client, is searching
5322 them to find one that matches an authentication mechanism offered by the
5323 server.
5324
5325 .cindex "generic options"
5326 .cindex "options" "generic &-- definition of"
5327 Within a driver instance definition, there are two kinds of option: &'generic'&
5328 and &'private'&. The generic options are those that apply to all drivers of the
5329 same type (that is, all routers, all transports or all authenticators). The
5330 &%driver%& option is a generic option that must appear in every definition.
5331 .cindex "private options"
5332 The private options are special for each driver, and none need appear, because
5333 they all have default values.
5334
5335 The options may appear in any order, except that the &%driver%& option must
5336 precede any private options, since these depend on the particular driver. For
5337 this reason, it is recommended that &%driver%& always be the first option.
5338
5339 Driver instance names, which are used for reference in log entries and
5340 elsewhere, can be any sequence of letters, digits, and underscores (starting
5341 with a letter) and must be unique among drivers of the same type. A router and
5342 a transport (for example) can each have the same name, but no two router
5343 instances can have the same name. The name of a driver instance should not be
5344 confused with the name of the underlying driver module. For example, the
5345 configuration lines:
5346 .code
5347 remote_smtp:
5348 driver = smtp
5349 .endd
5350 create an instance of the &(smtp)& transport driver whose name is
5351 &(remote_smtp)&. The same driver code can be used more than once, with
5352 different instance names and different option settings each time. A second
5353 instance of the &(smtp)& transport, with different options, might be defined
5354 thus:
5355 .code
5356 special_smtp:
5357 driver = smtp
5358 port = 1234
5359 command_timeout = 10s
5360 .endd
5361 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5362 these transport instances from routers, and these names would appear in log
5363 lines.
5364
5365 Comment lines may be present in the middle of driver specifications. The full
5366 list of option settings for any particular driver instance, including all the
5367 defaulted values, can be extracted by making use of the &%-bP%& command line
5368 option.
5369
5370
5371
5372
5373
5374
5375 . ////////////////////////////////////////////////////////////////////////////
5376 . ////////////////////////////////////////////////////////////////////////////
5377
5378 .chapter "The default configuration file" "CHAPdefconfil"
5379 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5380 .cindex "default" "configuration file &""walk through""&"
5381 The default configuration file supplied with Exim as &_src/configure.default_&
5382 is sufficient for a host with simple mail requirements. As an introduction to
5383 the way Exim is configured, this chapter &"walks through"& the default
5384 configuration, giving brief explanations of the settings. Detailed descriptions
5385 of the options are given in subsequent chapters. The default configuration file
5386 itself contains extensive comments about ways you might want to modify the
5387 initial settings. However, note that there are many options that are not
5388 mentioned at all in the default configuration.
5389
5390
5391
5392 .section "Main configuration settings" "SECTdefconfmain"
5393 The main (global) configuration option settings must always come first in the
5394 file. The first thing you'll see in the file, after some initial comments, is
5395 the line
5396 .code
5397 # primary_hostname =
5398 .endd
5399 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5400 to know the official, fully qualified name of your host, and this is where you
5401 can specify it. However, in most cases you do not need to set this option. When
5402 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5403
5404 The first three non-comment configuration lines are as follows:
5405 .code
5406 domainlist local_domains = @
5407 domainlist relay_to_domains =
5408 hostlist relay_from_hosts = 127.0.0.1
5409 .endd
5410 These are not, in fact, option settings. They are definitions of two named
5411 domain lists and one named host list. Exim allows you to give names to lists of
5412 domains, hosts, and email addresses, in order to make it easier to manage the
5413 configuration file (see section &<<SECTnamedlists>>&).
5414
5415 The first line defines a domain list called &'local_domains'&; this is used
5416 later in the configuration to identify domains that are to be delivered
5417 on the local host.
5418
5419 .cindex "@ in a domain list"
5420 There is just one item in this list, the string &"@"&. This is a special form
5421 of entry which means &"the name of the local host"&. Thus, if the local host is
5422 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5423 be delivered locally. Because the local host's name is referenced indirectly,
5424 the same configuration file can be used on different hosts.
5425
5426 The second line defines a domain list called &'relay_to_domains'&, but the
5427 list itself is empty. Later in the configuration we will come to the part that
5428 controls mail relaying through the local host; it allows relaying to any
5429 domains in this list. By default, therefore, no relaying on the basis of a mail
5430 domain is permitted.
5431
5432 The third line defines a host list called &'relay_from_hosts'&. This list is
5433 used later in the configuration to permit relaying from any host or IP address
5434 that matches the list. The default contains just the IP address of the IPv4
5435 loopback interface, which means that processes on the local host are able to
5436 submit mail for relaying by sending it over TCP/IP to that interface. No other
5437 hosts are permitted to submit messages for relaying.
5438
5439 Just to be sure there's no misunderstanding: at this point in the configuration
5440 we aren't actually setting up any controls. We are just defining some domains
5441 and hosts that will be used in the controls that are specified later.
5442
5443 The next two configuration lines are genuine option settings:
5444 .code
5445 acl_smtp_rcpt = acl_check_rcpt
5446 acl_smtp_data = acl_check_data
5447 .endd
5448 These options specify &'Access Control Lists'& (ACLs) that are to be used
5449 during an incoming SMTP session for every recipient of a message (every RCPT
5450 command), and after the contents of the message have been received,
5451 respectively. The names of the lists are &'acl_check_rcpt'& and
5452 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5453 section of the configuration. The RCPT ACL controls which recipients are
5454 accepted for an incoming message &-- if a configuration does not provide an ACL
5455 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5456 contents of a message to be checked.
5457
5458 Two commented-out option settings are next:
5459 .code
5460 # av_scanner = clamd:/tmp/clamd
5461 # spamd_address = 127.0.0.1 783
5462 .endd
5463 These are example settings that can be used when Exim is compiled with the
5464 content-scanning extension. The first specifies the interface to the virus
5465 scanner, and the second specifies the interface to SpamAssassin. Further
5466 details are given in chapter &<<CHAPexiscan>>&.
5467
5468 Three more commented-out option settings follow:
5469 .code
5470 # tls_advertise_hosts = *
5471 # tls_certificate = /etc/ssl/exim.crt
5472 # tls_privatekey = /etc/ssl/exim.pem
5473 .endd
5474 These are example settings that can be used when Exim is compiled with
5475 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5476 first one specifies the list of clients that are allowed to use TLS when
5477 connecting to this server; in this case the wildcard means all clients. The
5478 other options specify where Exim should find its TLS certificate and private
5479 key, which together prove the server's identity to any clients that connect.
5480 More details are given in chapter &<<CHAPTLS>>&.
5481
5482 Another two commented-out option settings follow:
5483 .code
5484 # daemon_smtp_ports = 25 : 465 : 587
5485 # tls_on_connect_ports = 465
5486 .endd
5487 .cindex "port" "465 and 587"
5488 .cindex "port" "for message submission"
5489 .cindex "message" "submission, ports for"
5490 .cindex "ssmtp protocol"
5491 .cindex "smtps protocol"
5492 .cindex "SMTP" "ssmtp protocol"
5493 .cindex "SMTP" "smtps protocol"
5494 These options provide better support for roaming users who wish to use this
5495 server for message submission. They are not much use unless you have turned on
5496 TLS (as described in the previous paragraph) and authentication (about which
5497 more in section &<<SECTdefconfauth>>&). The usual SMTP port 25 is often blocked
5498 on end-user networks, so RFC 4409 specifies that message submission should use
5499 port 587 instead. However some software (notably Microsoft Outlook) cannot be
5500 configured to use port 587 correctly, so these settings also enable the
5501 non-standard &"smtps"& (aka &"ssmtp"&) port 465 (see section
5502 &<<SECTsupobssmt>>&).
5503
5504 Two more commented-out options settings follow:
5505 .code
5506 # qualify_domain =
5507 # qualify_recipient =
5508 .endd
5509 The first of these specifies a domain that Exim uses when it constructs a
5510 complete email address from a local login name. This is often needed when Exim
5511 receives a message from a local process. If you do not set &%qualify_domain%&,
5512 the value of &%primary_hostname%& is used. If you set both of these options,
5513 you can have different qualification domains for sender and recipient
5514 addresses. If you set only the first one, its value is used in both cases.
5515
5516 .cindex "domain literal" "recognizing format"
5517 The following line must be uncommented if you want Exim to recognize
5518 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5519 (an IP address within square brackets) instead of a named domain.
5520 .code
5521 # allow_domain_literals
5522 .endd
5523 The RFCs still require this form, but many people think that in the modern
5524 Internet it makes little sense to permit mail to be sent to specific hosts by
5525 quoting their IP addresses. This ancient format has been used by people who
5526 try to abuse hosts by using them for unwanted relaying. However, some
5527 people believe there are circumstances (for example, messages addressed to
5528 &'postmaster'&) where domain literals are still useful.
5529
5530 The next configuration line is a kind of trigger guard:
5531 .code
5532 never_users = root
5533 .endd
5534 It specifies that no delivery must ever be run as the root user. The normal
5535 convention is to set up &'root'& as an alias for the system administrator. This
5536 setting is a guard against slips in the configuration.
5537 The list of users specified by &%never_users%& is not, however, the complete
5538 list; the build-time configuration in &_Local/Makefile_& has an option called
5539 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5540 contents of &%never_users%& are added to this list. By default
5541 FIXED_NEVER_USERS also specifies root.
5542
5543 When a remote host connects to Exim in order to send mail, the only information
5544 Exim has about the host's identity is its IP address. The next configuration
5545 line,
5546 .code
5547 host_lookup = *
5548 .endd
5549 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5550 in order to get a host name. This improves the quality of the logging
5551 information, but if you feel it is too expensive, you can remove it entirely,
5552 or restrict the lookup to hosts on &"nearby"& networks.
5553 Note that it is not always possible to find a host name from an IP address,
5554 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5555 unreachable.
5556
5557 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5558 1413 (hence their names):
5559 .code
5560 rfc1413_hosts = *
5561 rfc1413_query_timeout = 5s
5562 .endd
5563 These settings cause Exim to make ident callbacks for all incoming SMTP calls.
5564 You can limit the hosts to which these calls are made, or change the timeout
5565 that is used. If you set the timeout to zero, all ident calls are disabled.
5566 Although they are cheap and can provide useful information for tracing problem
5567 messages, some hosts and firewalls have problems with ident calls. This can
5568 result in a timeout instead of an immediate refused connection, leading to
5569 delays on starting up an incoming SMTP session.
5570
5571 When Exim receives messages over SMTP connections, it expects all addresses to
5572 be fully qualified with a domain, as required by the SMTP definition. However,
5573 if you are running a server to which simple clients submit messages, you may
5574 find that they send unqualified addresses. The two commented-out options:
5575 .code
5576 # sender_unqualified_hosts =
5577 # recipient_unqualified_hosts =
5578 .endd
5579 show how you can specify hosts that are permitted to send unqualified sender
5580 and recipient addresses, respectively.
5581
5582 The &%percent_hack_domains%& option is also commented out:
5583 .code
5584 # percent_hack_domains =
5585 .endd
5586 It provides a list of domains for which the &"percent hack"& is to operate.
5587 This is an almost obsolete form of explicit email routing. If you do not know
5588 anything about it, you can safely ignore this topic.
5589
5590 The last two settings in the main part of the default configuration are
5591 concerned with messages that have been &"frozen"& on Exim's queue. When a
5592 message is frozen, Exim no longer continues to try to deliver it. Freezing
5593 occurs when a bounce message encounters a permanent failure because the sender
5594 address of the original message that caused the bounce is invalid, so the
5595 bounce cannot be delivered. This is probably the most common case, but there
5596 are also other conditions that cause freezing, and frozen messages are not
5597 always bounce messages.
5598 .code
5599 ignore_bounce_errors_after = 2d
5600 timeout_frozen_after = 7d
5601 .endd
5602 The first of these options specifies that failing bounce messages are to be
5603 discarded after 2 days on the queue. The second specifies that any frozen
5604 message (whether a bounce message or not) is to be timed out (and discarded)
5605 after a week. In this configuration, the first setting ensures that no failing
5606 bounce message ever lasts a week.
5607
5608
5609
5610 .section "ACL configuration" "SECID54"
5611 .cindex "default" "ACLs"
5612 .cindex "&ACL;" "default configuration"
5613 In the default configuration, the ACL section follows the main configuration.
5614 It starts with the line
5615 .code
5616 begin acl
5617 .endd
5618 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5619 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5620 and &%acl_smtp_data%& above.
5621
5622 .cindex "RCPT" "ACL for"
5623 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5624 RCPT command specifies one of the message's recipients. The ACL statements
5625 are considered in order, until the recipient address is either accepted or
5626 rejected. The RCPT command is then accepted or rejected, according to the
5627 result of the ACL processing.
5628 .code
5629 acl_check_rcpt:
5630 .endd
5631 This line, consisting of a name terminated by a colon, marks the start of the
5632 ACL, and names it.
5633 .code
5634 accept hosts = :
5635 .endd
5636 This ACL statement accepts the recipient if the sending host matches the list.
5637 But what does that strange list mean? It doesn't actually contain any host
5638 names or IP addresses. The presence of the colon puts an empty item in the
5639 list; Exim matches this only if the incoming message did not come from a remote
5640 host, because in that case, the remote hostname is empty. The colon is
5641 important. Without it, the list itself is empty, and can never match anything.
5642
5643 What this statement is doing is to accept unconditionally all recipients in
5644 messages that are submitted by SMTP from local processes using the standard
5645 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5646 manner.
5647 .code
5648 deny message = Restricted characters in address
5649 domains = +local_domains
5650 local_parts = ^[.] : ^.*[@%!/|]
5651
5652 deny message = Restricted characters in address
5653 domains = !+local_domains
5654 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5655 .endd
5656 These statements are concerned with local parts that contain any of the
5657 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5658 Although these characters are entirely legal in local parts (in the case of
5659 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5660 in Internet mail addresses.
5661
5662 The first three have in the past been associated with explicitly routed
5663 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5664 option). Addresses containing these characters are regularly tried by spammers
5665 in an attempt to bypass relaying restrictions, and also by open relay testing
5666 programs. Unless you really need them it is safest to reject these characters
5667 at this early stage. This configuration is heavy-handed in rejecting these
5668 characters for all messages it accepts from remote hosts. This is a deliberate
5669 policy of being as safe as possible.
5670
5671 The first rule above is stricter, and is applied to messages that are addressed
5672 to one of the local domains handled by this host. This is implemented by the
5673 first condition, which restricts it to domains that are listed in the
5674 &'local_domains'& domain list. The &"+"& character is used to indicate a
5675 reference to a named list. In this configuration, there is just one domain in
5676 &'local_domains'&, but in general there may be many.
5677
5678 The second condition on the first statement uses two regular expressions to
5679 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5680 or &"|"&. If you have local accounts that include these characters, you will
5681 have to modify this rule.
5682
5683 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5684 allows them because they have been encountered in practice. (Consider the
5685 common convention of local parts constructed as
5686 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5687 the author of Exim, who has no second initial.) However, a local part starting
5688 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5689 file name (for example, for a mailing list). This is also true for local parts
5690 that contain slashes. A pipe symbol can also be troublesome if the local part
5691 is incorporated unthinkingly into a shell command line.
5692
5693 The second rule above applies to all other domains, and is less strict. This
5694 allows your own users to send outgoing messages to sites that use slashes
5695 and vertical bars in their local parts. It blocks local parts that begin
5696 with a dot, slash, or vertical bar, but allows these characters within the
5697 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5698 and &"!"& is blocked, as before. The motivation here is to prevent your users
5699 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5700 .code
5701 accept local_parts = postmaster
5702 domains = +local_domains
5703 .endd
5704 This statement, which has two conditions, accepts an incoming address if the
5705 local part is &'postmaster'& and the domain is one of those listed in the
5706 &'local_domains'& domain list. The &"+"& character is used to indicate a
5707 reference to a named list. In this configuration, there is just one domain in
5708 &'local_domains'&, but in general there may be many.
5709
5710 The presence of this statement means that mail to postmaster is never blocked
5711 by any of the subsequent tests. This can be helpful while sorting out problems
5712 in cases where the subsequent tests are incorrectly denying access.
5713 .code
5714 require verify = sender
5715 .endd
5716 This statement requires the sender address to be verified before any subsequent
5717 ACL statement can be used. If verification fails, the incoming recipient
5718 address is refused. Verification consists of trying to route the address, to
5719 see if a bounce message could be delivered to it. In the case of remote
5720 addresses, basic verification checks only the domain, but &'callouts'& can be
5721 used for more verification if required. Section &<<SECTaddressverification>>&
5722 discusses the details of address verification.
5723 .code
5724 accept hosts = +relay_from_hosts
5725 control = submission
5726 .endd
5727 This statement accepts the address if the message is coming from one of the
5728 hosts that are defined as being allowed to relay through this host. Recipient
5729 verification is omitted here, because in many cases the clients are dumb MUAs
5730 that do not cope well with SMTP error responses. For the same reason, the
5731 second line specifies &"submission mode"& for messages that are accepted. This
5732 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
5733 messages that are deficient in some way, for example, because they lack a
5734 &'Date:'& header line. If you are actually relaying out from MTAs, you should
5735 probably add recipient verification here, and disable submission mode.
5736 .code
5737 accept authenticated = *
5738 control = submission
5739 .endd
5740 This statement accepts the address if the client host has authenticated itself.
5741 Submission mode is again specified, on the grounds that such messages are most
5742 likely to come from MUAs. The default configuration does not define any
5743 authenticators, though it does include some nearly complete commented-out
5744 examples described in &<<SECTdefconfauth>>&. This means that no client can in
5745 fact authenticate until you complete the authenticator definitions.
5746 .code
5747 require message = relay not permitted
5748 domains = +local_domains : +relay_to_domains
5749 .endd
5750 This statement rejects the address if its domain is neither a local domain nor
5751 one of the domains for which this host is a relay.
5752 .code
5753 require verify = recipient
5754 .endd
5755 This statement requires the recipient address to be verified; if verification
5756 fails, the address is rejected.
5757 .code
5758 # deny message = rejected because $sender_host_address \
5759 # is in a black list at $dnslist_domain\n\
5760 # $dnslist_text
5761 # dnslists = black.list.example
5762 #
5763 # warn dnslists = black.list.example
5764 # add_header = X-Warning: $sender_host_address is in \
5765 # a black list at $dnslist_domain
5766 # log_message = found in $dnslist_domain
5767 .endd
5768 These commented-out lines are examples of how you could configure Exim to check
5769 sending hosts against a DNS black list. The first statement rejects messages
5770 from blacklisted hosts, whereas the second just inserts a warning header
5771 line.
5772 .code
5773 # require verify = csa
5774 .endd
5775 This commented-out line is an example of how you could turn on client SMTP
5776 authorization (CSA) checking. Such checks do DNS lookups for special SRV
5777 records.
5778 .code
5779 accept
5780 .endd
5781 The final statement in the first ACL unconditionally accepts any recipient
5782 address that has successfully passed all the previous tests.
5783 .code
5784 acl_check_data:
5785 .endd
5786 This line marks the start of the second ACL, and names it. Most of the contents
5787 of this ACL are commented out:
5788 .code
5789 # deny malware = *
5790 # message = This message contains a virus \
5791 # ($malware_name).
5792 .endd
5793 These lines are examples of how to arrange for messages to be scanned for
5794 viruses when Exim has been compiled with the content-scanning extension, and a
5795 suitable virus scanner is installed. If the message is found to contain a
5796 virus, it is rejected with the given custom error message.
5797 .code
5798 # warn spam = nobody
5799 # message = X-Spam_score: $spam_score\n\
5800 # X-Spam_score_int: $spam_score_int\n\
5801 # X-Spam_bar: $spam_bar\n\
5802 # X-Spam_report: $spam_report
5803 .endd
5804 These lines are an example of how to arrange for messages to be scanned by
5805 SpamAssassin when Exim has been compiled with the content-scanning extension,
5806 and SpamAssassin has been installed. The SpamAssassin check is run with
5807 &`nobody`& as its user parameter, and the results are added to the message as a
5808 series of extra header line. In this case, the message is not rejected,
5809 whatever the spam score.
5810 .code
5811 accept
5812 .endd
5813 This final line in the DATA ACL accepts the message unconditionally.
5814
5815
5816 .section "Router configuration" "SECID55"
5817 .cindex "default" "routers"
5818 .cindex "routers" "default"
5819 The router configuration comes next in the default configuration, introduced
5820 by the line
5821 .code
5822 begin routers
5823 .endd
5824 Routers are the modules in Exim that make decisions about where to send
5825 messages. An address is passed to each router in turn, until it is either
5826 accepted, or failed. This means that the order in which you define the routers
5827 matters. Each router is fully described in its own chapter later in this
5828 manual. Here we give only brief overviews.
5829 .code
5830 # domain_literal:
5831 # driver = ipliteral
5832 # domains = !+local_domains
5833 # transport = remote_smtp
5834 .endd
5835 .cindex "domain literal" "default router"
5836 This router is commented out because the majority of sites do not want to
5837 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
5838 you uncomment this router, you also need to uncomment the setting of
5839 &%allow_domain_literals%& in the main part of the configuration.
5840 .code
5841 dnslookup:
5842 driver = dnslookup
5843 domains = ! +local_domains
5844 transport = remote_smtp
5845 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
5846 no_more
5847 .endd
5848 The first uncommented router handles addresses that do not involve any local
5849 domains. This is specified by the line
5850 .code
5851 domains = ! +local_domains
5852 .endd
5853 The &%domains%& option lists the domains to which this router applies, but the
5854 exclamation mark is a negation sign, so the router is used only for domains
5855 that are not in the domain list called &'local_domains'& (which was defined at
5856 the start of the configuration). The plus sign before &'local_domains'&
5857 indicates that it is referring to a named list. Addresses in other domains are
5858 passed on to the following routers.
5859
5860 The name of the router driver is &(dnslookup)&,
5861 and is specified by the &%driver%& option. Do not be confused by the fact that
5862 the name of this router instance is the same as the name of the driver. The
5863 instance name is arbitrary, but the name set in the &%driver%& option must be
5864 one of the driver modules that is in the Exim binary.
5865
5866 The &(dnslookup)& router routes addresses by looking up their domains in the
5867 DNS in order to obtain a list of hosts to which the address is routed. If the
5868 router succeeds, the address is queued for the &(remote_smtp)& transport, as
5869 specified by the &%transport%& option. If the router does not find the domain
5870 in the DNS, no further routers are tried because of the &%no_more%& setting, so
5871 the address fails and is bounced.
5872
5873 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
5874 be entirely ignored. This option is present because a number of cases have been
5875 encountered where MX records in the DNS point to host names
5876 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
5877 Completely ignoring these IP addresses causes Exim to fail to route the
5878 email address, so it bounces. Otherwise, Exim would log a routing problem, and
5879 continue to try to deliver the message periodically until the address timed
5880 out.
5881 .code
5882 system_aliases:
5883 driver = redirect
5884 allow_fail
5885 allow_defer
5886 data = ${lookup{$local_part}lsearch{/etc/aliases}}
5887 # user = exim
5888 file_transport = address_file
5889 pipe_transport = address_pipe
5890 .endd
5891 Control reaches this and subsequent routers only for addresses in the local
5892 domains. This router checks to see whether the local part is defined as an
5893 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
5894 data that it looks up from that file. If no data is found for the local part,
5895 the value of the &%data%& option is empty, causing the address to be passed to
5896 the next router.
5897
5898 &_/etc/aliases_& is a conventional name for the system aliases file that is
5899 often used. That is why it is referenced by from the default configuration
5900 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
5901 &_Local/Makefile_& before building Exim.
5902 .code
5903 userforward:
5904 driver = redirect
5905 check_local_user
5906 # local_part_suffix = +* : -*
5907 # local_part_suffix_optional
5908 file = $home/.forward
5909 # allow_filter
5910 no_verify
5911 no_expn
5912 check_ancestor
5913 file_transport = address_file
5914 pipe_transport = address_pipe
5915 reply_transport = address_reply
5916 .endd
5917 This is the most complicated router in the default configuration. It is another
5918 redirection router, but this time it is looking for forwarding data set up by
5919 individual users. The &%check_local_user%& setting specifies a check that the
5920 local part of the address is the login name of a local user. If it is not, the
5921 router is skipped. The two commented options that follow &%check_local_user%&,
5922 namely:
5923 .code
5924 # local_part_suffix = +* : -*
5925 # local_part_suffix_optional
5926 .endd
5927 .vindex "&$local_part_suffix$&"
5928 show how you can specify the recognition of local part suffixes. If the first
5929 is uncommented, a suffix beginning with either a plus or a minus sign, followed
5930 by any sequence of characters, is removed from the local part and placed in the
5931 variable &$local_part_suffix$&. The second suffix option specifies that the
5932 presence of a suffix in the local part is optional. When a suffix is present,
5933 the check for a local login uses the local part with the suffix removed.
5934
5935 When a local user account is found, the file called &_.forward_& in the user's
5936 home directory is consulted. If it does not exist, or is empty, the router
5937 declines. Otherwise, the contents of &_.forward_& are interpreted as
5938 redirection data (see chapter &<<CHAPredirect>>& for more details).
5939
5940 .cindex "Sieve filter" "enabling in default router"
5941 Traditional &_.forward_& files contain just a list of addresses, pipes, or
5942 files. Exim supports this by default. However, if &%allow_filter%& is set (it
5943 is commented out by default), the contents of the file are interpreted as a set
5944 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
5945 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
5946 separate document entitled &'Exim's interfaces to mail filtering'&.
5947
5948 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
5949 verifying addresses, or when running as a consequence of an SMTP EXPN command.
5950 There are two reasons for doing this:
5951
5952 .olist
5953 Whether or not a local user has a &_.forward_& file is not really relevant when
5954 checking an address for validity; it makes sense not to waste resources doing
5955 unnecessary work.
5956 .next
5957 More importantly, when Exim is verifying addresses or handling an EXPN
5958 command during an SMTP session, it is running as the Exim user, not as root.
5959 The group is the Exim group, and no additional groups are set up.
5960 It may therefore not be possible for Exim to read users' &_.forward_& files at
5961 this time.
5962 .endlist
5963
5964 The setting of &%check_ancestor%& prevents the router from generating a new
5965 address that is the same as any previous address that was redirected. (This
5966 works round a problem concerning a bad interaction between aliasing and
5967 forwarding &-- see section &<<SECTredlocmai>>&).
5968
5969 The final three option settings specify the transports that are to be used when
5970 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
5971 auto-reply, respectively. For example, if a &_.forward_& file contains
5972 .code
5973 a.nother@elsewhere.example, /home/spqr/archive
5974 .endd
5975 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
5976 transport.
5977 .code
5978 localuser:
5979 driver = accept
5980 check_local_user
5981 # local_part_suffix = +* : -*
5982 # local_part_suffix_optional
5983 transport = local_delivery
5984 .endd
5985 The final router sets up delivery into local mailboxes, provided that the local
5986 part is the name of a local login, by accepting the address and assigning it to
5987 the &(local_delivery)& transport. Otherwise, we have reached the end of the
5988 routers, so the address is bounced. The commented suffix settings fulfil the
5989 same purpose as they do for the &(userforward)& router.
5990
5991
5992 .section "Transport configuration" "SECID56"
5993 .cindex "default" "transports"
5994 .cindex "transports" "default"
5995 Transports define mechanisms for actually delivering messages. They operate
5996 only when referenced from routers, so the order in which they are defined does
5997 not matter. The transports section of the configuration starts with
5998 .code
5999 begin transports
6000 .endd
6001 One remote transport and four local transports are defined.
6002 .code
6003 remote_smtp:
6004 driver = smtp
6005 .endd
6006 This transport is used for delivering messages over SMTP connections. All its
6007 options are defaulted. The list of remote hosts comes from the router.
6008 .code
6009 local_delivery:
6010 driver = appendfile
6011 file = /var/mail/$local_part
6012 delivery_date_add
6013 envelope_to_add
6014 return_path_add
6015 # group = mail
6016 # mode = 0660
6017 .endd
6018 This &(appendfile)& transport is used for local delivery to user mailboxes in
6019 traditional BSD mailbox format. By default it runs under the uid and gid of the
6020 local user, which requires the sticky bit to be set on the &_/var/mail_&
6021 directory. Some systems use the alternative approach of running mail deliveries
6022 under a particular group instead of using the sticky bit. The commented options
6023 show how this can be done.
6024
6025 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6026 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6027 similarly-named options above.
6028 .code
6029 address_pipe:
6030 driver = pipe
6031 return_output
6032 .endd
6033 This transport is used for handling deliveries to pipes that are generated by
6034 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6035 option specifies that any output generated by the pipe is to be returned to the
6036 sender.
6037 .code
6038 address_file:
6039 driver = appendfile
6040 delivery_date_add
6041 envelope_to_add
6042 return_path_add
6043 .endd
6044 This transport is used for handling deliveries to files that are generated by
6045 redirection. The name of the file is not specified in this instance of
6046 &(appendfile)&, because it comes from the &(redirect)& router.
6047 .code
6048 address_reply:
6049 driver = autoreply
6050 .endd
6051 This transport is used for handling automatic replies generated by users'
6052 filter files.
6053
6054
6055
6056 .section "Default retry rule" "SECID57"
6057 .cindex "retry" "default rule"
6058 .cindex "default" "retry rule"
6059 The retry section of the configuration file contains rules which affect the way
6060 Exim retries deliveries that cannot be completed at the first attempt. It is
6061 introduced by the line
6062 .code
6063 begin retry
6064 .endd
6065 In the default configuration, there is just one rule, which applies to all
6066 errors:
6067 .code
6068 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6069 .endd
6070 This causes any temporarily failing address to be retried every 15 minutes for
6071 2 hours, then at intervals starting at one hour and increasing by a factor of
6072 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6073 is not delivered after 4 days of temporary failure, it is bounced.
6074
6075 If the retry section is removed from the configuration, or is empty (that is,
6076 if no retry rules are defined), Exim will not retry deliveries. This turns
6077 temporary errors into permanent errors.
6078
6079
6080 .section "Rewriting configuration" "SECID58"
6081 The rewriting section of the configuration, introduced by
6082 .code
6083 begin rewrite
6084 .endd
6085 contains rules for rewriting addresses in messages as they arrive. There are no
6086 rewriting rules in the default configuration file.
6087
6088
6089
6090 .section "Authenticators configuration" "SECTdefconfauth"
6091 .cindex "AUTH" "configuration"
6092 The authenticators section of the configuration, introduced by
6093 .code
6094 begin authenticators
6095 .endd
6096 defines mechanisms for the use of the SMTP AUTH command. The default
6097 configuration file contains two commented-out example authenticators
6098 which support plaintext username/password authentication using the
6099 standard PLAIN mechanism and the traditional but non-standard LOGIN
6100 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6101 to support most MUA software.
6102
6103 The example PLAIN authenticator looks like this:
6104 .code
6105 #PLAIN:
6106 # driver = plaintext
6107 # server_set_id = $auth2
6108 # server_prompts = :
6109 # server_condition = Authentication is not yet configured
6110 # server_advertise_condition = ${if def:tls_in_cipher }
6111 .endd
6112 And the example LOGIN authenticator looks like this:
6113 .code
6114 #LOGIN:
6115 # driver = plaintext
6116 # server_set_id = $auth1
6117 # server_prompts = <| Username: | Password:
6118 # server_condition = Authentication is not yet configured
6119 # server_advertise_condition = ${if def:tls_in_cipher }
6120 .endd
6121
6122 The &%server_set_id%& option makes Exim remember the authenticated username
6123 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6124 &%server_prompts%& option configures the &(plaintext)& authenticator so
6125 that it implements the details of the specific authentication mechanism,
6126 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6127 when Exim offers authentication to clients; in the examples, this is only
6128 when TLS or SSL has been started, so to enable the authenticators you also
6129 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6130
6131 The &%server_condition%& setting defines how to verify that the username and
6132 password are correct. In the examples it just produces an error message.
6133 To make the authenticators work, you can use a string expansion
6134 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6135
6136 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6137 usercode and password are in different positions.
6138 Chapter &<<CHAPplaintext>>& covers both.
6139
6140 .ecindex IIDconfiwal
6141
6142
6143
6144 . ////////////////////////////////////////////////////////////////////////////
6145 . ////////////////////////////////////////////////////////////////////////////
6146
6147 .chapter "Regular expressions" "CHAPregexp"
6148
6149 .cindex "regular expressions" "library"
6150 .cindex "PCRE"
6151 Exim supports the use of regular expressions in many of its options. It
6152 uses the PCRE regular expression library; this provides regular expression
6153 matching that is compatible with Perl 5. The syntax and semantics of
6154 regular expressions is discussed in many Perl reference books, and also in
6155 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6156 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6157
6158 The documentation for the syntax and semantics of the regular expressions that
6159 are supported by PCRE is included in the PCRE distribution, and no further
6160 description is included here. The PCRE functions are called from Exim using
6161 the default option settings (that is, with no PCRE options set), except that
6162 the PCRE_CASELESS option is set when the matching is required to be
6163 case-insensitive.
6164
6165 In most cases, when a regular expression is required in an Exim configuration,
6166 it has to start with a circumflex, in order to distinguish it from plain text
6167 or an &"ends with"& wildcard. In this example of a configuration setting, the
6168 second item in the colon-separated list is a regular expression.
6169 .code
6170 domains = a.b.c : ^\\d{3} : *.y.z : ...
6171 .endd
6172 The doubling of the backslash is required because of string expansion that
6173 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6174 of this issue, and a way of avoiding the need for doubling backslashes. The
6175 regular expression that is eventually used in this example contains just one
6176 backslash. The circumflex is included in the regular expression, and has the
6177 normal effect of &"anchoring"& it to the start of the string that is being
6178 matched.
6179
6180 There are, however, two cases where a circumflex is not required for the
6181 recognition of a regular expression: these are the &%match%& condition in a
6182 string expansion, and the &%matches%& condition in an Exim filter file. In
6183 these cases, the relevant string is always treated as a regular expression; if
6184 it does not start with a circumflex, the expression is not anchored, and can
6185 match anywhere in the subject string.
6186
6187 In all cases, if you want a regular expression to match at the end of a string,
6188 you must code the $ metacharacter to indicate this. For example:
6189 .code
6190 domains = ^\\d{3}\\.example
6191 .endd
6192 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6193 You need to use:
6194 .code
6195 domains = ^\\d{3}\\.example\$
6196 .endd
6197 if you want &'example'& to be the top-level domain. The backslash before the
6198 $ is needed because string expansion also interprets dollar characters.
6199
6200
6201
6202 . ////////////////////////////////////////////////////////////////////////////
6203 . ////////////////////////////////////////////////////////////////////////////
6204
6205 .chapter "File and database lookups" "CHAPfdlookup"
6206 .scindex IIDfidalo1 "file" "lookups"
6207 .scindex IIDfidalo2 "database" "lookups"
6208 .cindex "lookup" "description of"
6209 Exim can be configured to look up data in files or databases as it processes
6210 messages. Two different kinds of syntax are used:
6211
6212 .olist
6213 A string that is to be expanded may contain explicit lookup requests. These
6214 cause parts of the string to be replaced by data that is obtained from the
6215 lookup. Lookups of this type are conditional expansion items. Different results
6216 can be defined for the cases of lookup success and failure. See chapter
6217 &<<CHAPexpand>>&, where string expansions are described in detail.
6218 .next
6219 Lists of domains, hosts, and email addresses can contain lookup requests as a
6220 way of avoiding excessively long linear lists. In this case, the data that is
6221 returned by the lookup is often (but not always) discarded; whether the lookup
6222 succeeds or fails is what really counts. These kinds of list are described in
6223 chapter &<<CHAPdomhosaddlists>>&.
6224 .endlist
6225
6226 String expansions, lists, and lookups interact with each other in such a way
6227 that there is no order in which to describe any one of them that does not
6228 involve references to the others. Each of these three chapters makes more sense
6229 if you have read the other two first. If you are reading this for the first
6230 time, be aware that some of it will make a lot more sense after you have read
6231 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6232
6233 .section "Examples of different lookup syntax" "SECID60"
6234 It is easy to confuse the two different kinds of lookup, especially as the
6235 lists that may contain the second kind are always expanded before being
6236 processed as lists. Therefore, they may also contain lookups of the first kind.
6237 Be careful to distinguish between the following two examples:
6238 .code
6239 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6240 domains = lsearch;/some/file
6241 .endd
6242 The first uses a string expansion, the result of which must be a domain list.
6243 No strings have been specified for a successful or a failing lookup; the
6244 defaults in this case are the looked-up data and an empty string, respectively.
6245 The expansion takes place before the string is processed as a list, and the
6246 file that is searched could contain lines like this:
6247 .code
6248 192.168.3.4: domain1:domain2:...
6249 192.168.1.9: domain3:domain4:...
6250 .endd
6251 When the lookup succeeds, the result of the expansion is a list of domains (and
6252 possibly other types of item that are allowed in domain lists).
6253
6254 In the second example, the lookup is a single item in a domain list. It causes
6255 Exim to use a lookup to see if the domain that is being processed can be found
6256 in the file. The file could contains lines like this:
6257 .code
6258 domain1:
6259 domain2:
6260 .endd
6261 Any data that follows the keys is not relevant when checking that the domain
6262 matches the list item.
6263
6264 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6265 Consider a file containing lines like this:
6266 .code
6267 192.168.5.6: lsearch;/another/file
6268 .endd
6269 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6270 first &%domains%& setting above generates the second setting, which therefore
6271 causes a second lookup to occur.
6272
6273 The rest of this chapter describes the different lookup types that are
6274 available. Any of them can be used in any part of the configuration where a
6275 lookup is permitted.
6276
6277
6278 .section "Lookup types" "SECID61"
6279 .cindex "lookup" "types of"
6280 .cindex "single-key lookup" "definition of"
6281 Two different types of data lookup are implemented:
6282
6283 .ilist
6284 The &'single-key'& type requires the specification of a file in which to look,
6285 and a single key to search for. The key must be a non-empty string for the
6286 lookup to succeed. The lookup type determines how the file is searched.
6287 .next
6288 .cindex "query-style lookup" "definition of"
6289 The &'query-style'& type accepts a generalized database query. No particular
6290 key value is assumed by Exim for query-style lookups. You can use whichever
6291 Exim variables you need to construct the database query.
6292 .endlist
6293
6294 The code for each lookup type is in a separate source file that is included in
6295 the binary of Exim only if the corresponding compile-time option is set. The
6296 default settings in &_src/EDITME_& are:
6297 .code
6298 LOOKUP_DBM=yes
6299 LOOKUP_LSEARCH=yes
6300 .endd
6301 which means that only linear searching and DBM lookups are included by default.
6302 For some types of lookup (e.g. SQL databases), you need to install appropriate
6303 libraries and header files before building Exim.
6304
6305
6306
6307
6308 .section "Single-key lookup types" "SECTsinglekeylookups"
6309 .cindex "lookup" "single-key types"
6310 .cindex "single-key lookup" "list of types"
6311 The following single-key lookup types are implemented:
6312
6313 .ilist
6314 .cindex "cdb" "description of"
6315 .cindex "lookup" "cdb"
6316 .cindex "binary zero" "in lookup key"
6317 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6318 string without a terminating binary zero. The cdb format is designed for
6319 indexed files that are read frequently and never updated, except by total
6320 re-creation. As such, it is particularly suitable for large files containing
6321 aliases or other indexed data referenced by an MTA. Information about cdb can
6322 be found in several places:
6323 .display
6324 &url(http://www.pobox.com/~djb/cdb.html)
6325 &url(ftp://ftp.corpit.ru/pub/tinycdb/)
6326 &url(http://packages.debian.org/stable/utils/freecdb.html)
6327 .endd
6328 A cdb distribution is not needed in order to build Exim with cdb support,
6329 because the code for reading cdb files is included directly in Exim itself.
6330 However, no means of building or testing cdb files is provided with Exim, so
6331 you need to obtain a cdb distribution in order to do this.
6332 .next
6333 .cindex "DBM" "lookup type"
6334 .cindex "lookup" "dbm"
6335 .cindex "binary zero" "in lookup key"
6336 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6337 DBM file by looking up the record with the given key. A terminating binary
6338 zero is included in the key that is passed to the DBM library. See section
6339 &<<SECTdb>>& for a discussion of DBM libraries.
6340
6341 .cindex "Berkeley DB library" "file format"
6342 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6343 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6344 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6345 the DB_UNKNOWN option. This enables it to handle any of the types of database
6346 that the library supports, and can be useful for accessing DBM files created by
6347 other applications. (For earlier DB versions, DB_HASH is always used.)
6348 .next
6349 .cindex "lookup" "dbmjz"
6350 .cindex "lookup" "dbm &-- embedded NULs"
6351 .cindex "sasldb2"
6352 .cindex "dbmjz lookup type"
6353 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6354 interpreted as an Exim list; the elements of the list are joined together with
6355 ASCII NUL characters to form the lookup key. An example usage would be to
6356 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6357 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6358 &(cram_md5)& authenticator.
6359 .next
6360 .cindex "lookup" "dbmnz"
6361 .cindex "lookup" "dbm &-- terminating zero"
6362 .cindex "binary zero" "in lookup key"
6363 .cindex "Courier"
6364 .cindex "&_/etc/userdbshadow.dat_&"
6365 .cindex "dbmnz lookup type"
6366 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6367 is not included in the key that is passed to the DBM library. You may need this
6368 if you want to look up data in files that are created by or shared with some
6369 other application that does not use terminating zeros. For example, you need to
6370 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6371 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6372 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6373 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6374 .next
6375 .cindex "lookup" "dsearch"
6376 .cindex "dsearch lookup type"
6377 &(dsearch)&: The given file must be a directory; this is searched for an entry
6378 whose name is the key by calling the &[lstat()]& function. The key may not
6379 contain any forward slash characters. If &[lstat()]& succeeds, the result of
6380 the lookup is the name of the entry, which may be a file, directory,
6381 symbolic link, or any other kind of directory entry. An example of how this
6382 lookup can be used to support virtual domains is given in section
6383 &<<SECTvirtualdomains>>&.
6384 .next
6385 .cindex "lookup" "iplsearch"
6386 .cindex "iplsearch lookup type"
6387 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6388 terminated by a colon or white space or the end of the line. The keys in the
6389 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6390 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6391 being interpreted as a key terminator. For example:
6392 .code
6393 1.2.3.4: data for 1.2.3.4
6394 192.168.0.0/16: data for 192.168.0.0/16
6395 "abcd::cdab": data for abcd::cdab
6396 "abcd:abcd::/32" data for abcd:abcd::/32
6397 .endd
6398 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6399 file is searched linearly, using the CIDR masks where present, until a matching
6400 key is found. The first key that matches is used; there is no attempt to find a
6401 &"best"& match. Apart from the way the keys are matched, the processing for
6402 &(iplsearch)& is the same as for &(lsearch)&.
6403
6404 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6405 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6406 lookup types support only literal keys.
6407
6408 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6409 the implicit key is the host's IP address rather than its name (see section
6410 &<<SECThoslispatsikey>>&).
6411 .next
6412 .cindex "linear search"
6413 .cindex "lookup" "lsearch"
6414 .cindex "lsearch lookup type"
6415 .cindex "case sensitivity" "in lsearch lookup"
6416 &(lsearch)&: The given file is a text file that is searched linearly for a
6417 line beginning with the search key, terminated by a colon or white space or the
6418 end of the line. The search is case-insensitive; that is, upper and lower case
6419 letters are treated as the same. The first occurrence of the key that is found
6420 in the file is used.
6421
6422 White space between the key and the colon is permitted. The remainder of the
6423 line, with leading and trailing white space removed, is the data. This can be
6424 continued onto subsequent lines by starting them with any amount of white
6425 space, but only a single space character is included in the data at such a
6426 junction. If the data begins with a colon, the key must be terminated by a
6427 colon, for example:
6428 .code
6429 baduser: :fail:
6430 .endd
6431 Empty lines and lines beginning with # are ignored, even if they occur in the
6432 middle of an item. This is the traditional textual format of alias files. Note
6433 that the keys in an &(lsearch)& file are literal strings. There is no
6434 wildcarding of any kind.
6435
6436 .cindex "lookup" "lsearch &-- colons in keys"
6437 .cindex "white space" "in lsearch key"
6438 In most &(lsearch)& files, keys are not required to contain colons or #
6439 characters, or white space. However, if you need this feature, it is available.
6440 If a key begins with a doublequote character, it is terminated only by a
6441 matching quote (or end of line), and the normal escaping rules apply to its
6442 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6443 quoted keys (exactly as for unquoted keys). There is no special handling of
6444 quotes for the data part of an &(lsearch)& line.
6445
6446 .next
6447 .cindex "NIS lookup type"
6448 .cindex "lookup" "NIS"
6449 .cindex "binary zero" "in lookup key"
6450 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
6451 the given key, without a terminating binary zero. There is a variant called
6452 &(nis0)& which does include the terminating binary zero in the key. This is
6453 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6454 aliases; the full map names must be used.
6455
6456 .next
6457 .cindex "wildlsearch lookup type"
6458 .cindex "lookup" "wildlsearch"
6459 .cindex "nwildlsearch lookup type"
6460 .cindex "lookup" "nwildlsearch"
6461 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6462 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6463 the file may be wildcarded. The difference between these two lookup types is
6464 that for &(wildlsearch)&, each key in the file is string-expanded before being
6465 used, whereas for &(nwildlsearch)&, no expansion takes place.
6466
6467 .cindex "case sensitivity" "in (n)wildlsearch lookup"
6468 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
6469 file that are regular expressions can be made case-sensitive by the use of
6470 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
6471
6472 . ==== As this is a nested list, any displays it contains must be indented
6473 . ==== as otherwise they are too far to the left.
6474
6475 .olist
6476 The string may begin with an asterisk to mean &"ends with"&. For example:
6477 .code
6478 *.a.b.c data for anything.a.b.c
6479 *fish data for anythingfish
6480 .endd
6481 .next
6482 The string may begin with a circumflex to indicate a regular expression. For
6483 example, for &(wildlsearch)&:
6484 .code
6485 ^\N\d+\.a\.b\N data for <digits>.a.b
6486 .endd
6487 Note the use of &`\N`& to disable expansion of the contents of the regular
6488 expression. If you are using &(nwildlsearch)&, where the keys are not
6489 string-expanded, the equivalent entry is:
6490 .code
6491 ^\d+\.a\.b data for <digits>.a.b
6492 .endd
6493 The case-insensitive flag is set at the start of compiling the regular
6494 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
6495 For example, to make the entire pattern case-sensitive:
6496 .code
6497 ^(?-i)\d+\.a\.b data for <digits>.a.b
6498 .endd
6499
6500 If the regular expression contains white space or colon characters, you must
6501 either quote it (see &(lsearch)& above), or represent these characters in other
6502 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
6503 colon. This may be easier than quoting, because if you quote, you have to
6504 escape all the backslashes inside the quotes.
6505
6506 &*Note*&: It is not possible to capture substrings in a regular expression
6507 match for later use, because the results of all lookups are cached. If a lookup
6508 is repeated, the result is taken from the cache, and no actual pattern matching
6509 takes place. The values of all the numeric variables are unset after a
6510 &((n)wildlsearch)& match.
6511
6512 .next
6513 Although I cannot see it being of much use, the general matching function that
6514 is used to implement &((n)wildlsearch)& means that the string may begin with a
6515 lookup name terminated by a semicolon, and followed by lookup data. For
6516 example:
6517 .code
6518 cdb;/some/file data for keys that match the file
6519 .endd
6520 The data that is obtained from the nested lookup is discarded.
6521 .endlist olist
6522
6523 Keys that do not match any of these patterns are interpreted literally. The
6524 continuation rules for the data are the same as for &(lsearch)&, and keys may
6525 be followed by optional colons.
6526
6527 &*Warning*&: Unlike most other single-key lookup types, a file of data for
6528 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
6529 lookup types support only literal keys.
6530 .endlist ilist
6531
6532
6533 .section "Query-style lookup types" "SECID62"
6534 .cindex "lookup" "query-style types"
6535 .cindex "query-style lookup" "list of types"
6536 The supported query-style lookup types are listed below. Further details about
6537 many of them are given in later sections.
6538
6539 .ilist
6540 .cindex "DNS" "as a lookup type"
6541 .cindex "lookup" "DNS"
6542 &(dnsdb)&: This does a DNS search for one or more records whose domain names
6543 are given in the supplied query. The resulting data is the contents of the
6544 records. See section &<<SECTdnsdb>>&.
6545 .next
6546 .cindex "InterBase lookup type"
6547 .cindex "lookup" "InterBase"
6548 &(ibase)&: This does a lookup in an InterBase database.
6549 .next
6550 .cindex "LDAP" "lookup type"
6551 .cindex "lookup" "LDAP"
6552 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
6553 returns attributes from a single entry. There is a variant called &(ldapm)&
6554 that permits values from multiple entries to be returned. A third variant
6555 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
6556 any attribute values. See section &<<SECTldap>>&.
6557 .next
6558 .cindex "MySQL" "lookup type"
6559 .cindex "lookup" "MySQL"
6560 &(mysql)&: The format of the query is an SQL statement that is passed to a
6561 MySQL database. See section &<<SECTsql>>&.
6562 .next
6563 .cindex "NIS+ lookup type"
6564 .cindex "lookup" "NIS+"
6565 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
6566 the field to be returned. See section &<<SECTnisplus>>&.
6567 .next
6568 .cindex "Oracle" "lookup type"
6569 .cindex "lookup" "Oracle"
6570 &(oracle)&: The format of the query is an SQL statement that is passed to an
6571 Oracle database. See section &<<SECTsql>>&.
6572 .next
6573 .cindex "lookup" "passwd"
6574 .cindex "passwd lookup type"
6575 .cindex "&_/etc/passwd_&"
6576 &(passwd)& is a query-style lookup with queries that are just user names. The
6577 lookup calls &[getpwnam()]& to interrogate the system password data, and on
6578 success, the result string is the same as you would get from an &(lsearch)&
6579 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
6580 password value. For example:
6581 .code
6582 *:42:42:King Rat:/home/kr:/bin/bash
6583 .endd
6584 .next
6585 .cindex "PostgreSQL lookup type"
6586 .cindex "lookup" "PostgreSQL"
6587 &(pgsql)&: The format of the query is an SQL statement that is passed to a
6588 PostgreSQL database. See section &<<SECTsql>>&.
6589
6590 .next
6591 .cindex "sqlite lookup type"
6592 .cindex "lookup" "sqlite"
6593 &(sqlite)&: The format of the query is a file name followed by an SQL statement
6594 that is passed to an SQLite database. See section &<<SECTsqlite>>&.
6595
6596 .next
6597 &(testdb)&: This is a lookup type that is used for testing Exim. It is
6598 not likely to be useful in normal operation.
6599 .next
6600 .cindex "whoson lookup type"
6601 .cindex "lookup" "whoson"
6602 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
6603 allows a server to check whether a particular (dynamically allocated) IP
6604 address is currently allocated to a known (trusted) user and, optionally, to
6605 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
6606 at one time for &"POP before SMTP"& authentication, but that approach has been
6607 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
6608 &"POP before SMTP"& checking using ACL statements such as
6609 .code
6610 require condition = \
6611 ${lookup whoson {$sender_host_address}{yes}{no}}
6612 .endd
6613 The query consists of a single IP address. The value returned is the name of
6614 the authenticated user, which is stored in the variable &$value$&. However, in
6615 this example, the data in &$value$& is not used; the result of the lookup is
6616 one of the fixed strings &"yes"& or &"no"&.
6617 .endlist
6618
6619
6620
6621 .section "Temporary errors in lookups" "SECID63"
6622 .cindex "lookup" "temporary error in"
6623 Lookup functions can return temporary error codes if the lookup cannot be
6624 completed. For example, an SQL or LDAP database might be unavailable. For this
6625 reason, it is not advisable to use a lookup that might do this for critical
6626 options such as a list of local domains.
6627
6628 When a lookup cannot be completed in a router or transport, delivery
6629 of the message (to the relevant address) is deferred, as for any other
6630 temporary error. In other circumstances Exim may assume the lookup has failed,
6631 or may give up altogether.
6632
6633
6634
6635 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
6636 .cindex "wildcard lookups"
6637 .cindex "lookup" "default values"
6638 .cindex "lookup" "wildcard"
6639 .cindex "lookup" "* added to type"
6640 .cindex "default" "in single-key lookups"
6641 In this context, a &"default value"& is a value specified by the administrator
6642 that is to be used if a lookup fails.
6643
6644 &*Note:*& This section applies only to single-key lookups. For query-style
6645 lookups, the facilities of the query language must be used. An attempt to
6646 specify a default for a query-style lookup provokes an error.
6647
6648 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
6649 and the initial lookup fails, the key &"*"& is looked up in the file to
6650 provide a default value. See also the section on partial matching below.
6651
6652 .cindex "*@ with single-key lookup"
6653 .cindex "lookup" "*@ added to type"
6654 .cindex "alias file" "per-domain default"
6655 Alternatively, if &"*@"& is added to a single-key lookup type (for example
6656 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
6657 character, a second lookup is done with everything before the last @ replaced
6658 by *. This makes it possible to provide per-domain defaults in alias files
6659 that include the domains in the keys. If the second lookup fails (or doesn't
6660 take place because there is no @ in the key), &"*"& is looked up.
6661 For example, a &(redirect)& router might contain:
6662 .code
6663 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
6664 .endd
6665 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
6666 looks up these keys, in this order:
6667 .code
6668 jane@eyre.example
6669 *@eyre.example
6670 *
6671 .endd
6672 The data is taken from whichever key it finds first. &*Note*&: In an
6673 &(lsearch)& file, this does not mean the first of these keys in the file. A
6674 complete scan is done for each key, and only if it is not found at all does
6675 Exim move on to try the next key.
6676
6677
6678
6679 .section "Partial matching in single-key lookups" "SECTpartiallookup"
6680 .cindex "partial matching"
6681 .cindex "wildcard lookups"
6682 .cindex "lookup" "partial matching"
6683 .cindex "lookup" "wildcard"
6684 .cindex "asterisk" "in search type"
6685 The normal operation of a single-key lookup is to search the file for an exact
6686 match with the given key. However, in a number of situations where domains are
6687 being looked up, it is useful to be able to do partial matching. In this case,
6688 information in the file that has a key starting with &"*."& is matched by any
6689 domain that ends with the components that follow the full stop. For example, if
6690 a key in a DBM file is
6691 .code
6692 *.dates.fict.example
6693 .endd
6694 then when partial matching is enabled this is matched by (amongst others)
6695 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
6696 by &'dates.fict.example'&, if that does not appear as a separate key in the
6697 file.
6698
6699 &*Note*&: Partial matching is not available for query-style lookups. It is
6700 also not available for any lookup items in address lists (see section
6701 &<<SECTaddresslist>>&).
6702
6703 Partial matching is implemented by doing a series of separate lookups using
6704 keys constructed by modifying the original subject key. This means that it can
6705 be used with any of the single-key lookup types, provided that
6706 partial matching keys
6707 beginning with a special prefix (default &"*."&) are included in the data file.
6708 Keys in the file that do not begin with the prefix are matched only by
6709 unmodified subject keys when partial matching is in use.
6710
6711 Partial matching is requested by adding the string &"partial-"& to the front of
6712 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
6713 is done, the subject key is first looked up unmodified; if that fails, &"*."&
6714 is added at the start of the subject key, and it is looked up again. If that
6715 fails, further lookups are tried with dot-separated components removed from the
6716 start of the subject key, one-by-one, and &"*."& added on the front of what
6717 remains.
6718
6719 A minimum number of two non-* components are required. This can be adjusted
6720 by including a number before the hyphen in the search type. For example,
6721 &%partial3-lsearch%& specifies a minimum of three non-* components in the
6722 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
6723 subject key is &'2250.dates.fict.example'& then the following keys are looked
6724 up when the minimum number of non-* components is two:
6725 .code
6726 2250.dates.fict.example
6727 *.2250.dates.fict.example
6728 *.dates.fict.example
6729 *.fict.example
6730 .endd
6731 As soon as one key in the sequence is successfully looked up, the lookup
6732 finishes.
6733
6734 .cindex "lookup" "partial matching &-- changing prefix"
6735 .cindex "prefix" "for partial matching"
6736 The use of &"*."& as the partial matching prefix is a default that can be
6737 changed. The motivation for this feature is to allow Exim to operate with file
6738 formats that are used by other MTAs. A different prefix can be supplied in
6739 parentheses instead of the hyphen after &"partial"&. For example:
6740 .code
6741 domains = partial(.)lsearch;/some/file
6742 .endd
6743 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
6744 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
6745 components is unchanged). The prefix may consist of any punctuation characters
6746 other than a closing parenthesis. It may be empty, for example:
6747 .code
6748 domains = partial1()cdb;/some/file
6749 .endd
6750 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
6751 &`a.b.c`&, &`b.c`&, and &`c`&.
6752
6753 If &"partial0"& is specified, what happens at the end (when the lookup with
6754 just one non-wild component has failed, and the original key is shortened right
6755 down to the null string) depends on the prefix:
6756
6757 .ilist
6758 If the prefix has zero length, the whole lookup fails.
6759 .next
6760 If the prefix has length 1, a lookup for just the prefix is done. For
6761 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
6762 .next
6763 Otherwise, if the prefix ends in a dot, the dot is removed, and the
6764 remainder is looked up. With the default prefix, therefore, the final lookup is
6765 for &"*"& on its own.
6766 .next
6767 Otherwise, the whole prefix is looked up.
6768 .endlist
6769
6770
6771 If the search type ends in &"*"& or &"*@"& (see section
6772 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
6773 this implies happens after all partial lookups have failed. If &"partial0"& is
6774 specified, adding &"*"& to the search type has no effect with the default
6775 prefix, because the &"*"& key is already included in the sequence of partial
6776 lookups. However, there might be a use for lookup types such as
6777 &"partial0(.)lsearch*"&.
6778
6779 The use of &"*"& in lookup partial matching differs from its use as a wildcard
6780 in domain lists and the like. Partial matching works only in terms of
6781 dot-separated components; a key such as &`*fict.example`&
6782 in a database file is useless, because the asterisk in a partial matching
6783 subject key is always followed by a dot.
6784
6785
6786
6787
6788 .section "Lookup caching" "SECID64"
6789 .cindex "lookup" "caching"
6790 .cindex "caching" "lookup data"
6791 Exim caches all lookup results in order to avoid needless repetition of
6792 lookups. However, because (apart from the daemon) Exim operates as a collection
6793 of independent, short-lived processes, this caching applies only within a
6794 single Exim process. There is no inter-process lookup caching facility.
6795
6796 For single-key lookups, Exim keeps the relevant files open in case there is
6797 another lookup that needs them. In some types of configuration this can lead to
6798 many files being kept open for messages with many recipients. To avoid hitting
6799 the operating system limit on the number of simultaneously open files, Exim
6800 closes the least recently used file when it needs to open more files than its
6801 own internal limit, which can be changed via the &%lookup_open_max%& option.
6802
6803 The single-key lookup files are closed and the lookup caches are flushed at
6804 strategic points during delivery &-- for example, after all routing is
6805 complete.
6806
6807
6808
6809
6810 .section "Quoting lookup data" "SECID65"
6811 .cindex "lookup" "quoting"
6812 .cindex "quoting" "in lookups"
6813 When data from an incoming message is included in a query-style lookup, there
6814 is the possibility of special characters in the data messing up the syntax of
6815 the query. For example, a NIS+ query that contains
6816 .code
6817 [name=$local_part]
6818 .endd
6819 will be broken if the local part happens to contain a closing square bracket.
6820 For NIS+, data can be enclosed in double quotes like this:
6821 .code
6822 [name="$local_part"]
6823 .endd
6824 but this still leaves the problem of a double quote in the data. The rule for
6825 NIS+ is that double quotes must be doubled. Other lookup types have different
6826 rules, and to cope with the differing requirements, an expansion operator
6827 of the following form is provided:
6828 .code
6829 ${quote_<lookup-type>:<string>}
6830 .endd
6831 For example, the safest way to write the NIS+ query is
6832 .code
6833 [name="${quote_nisplus:$local_part}"]
6834 .endd
6835 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
6836 operator can be used for all lookup types, but has no effect for single-key
6837 lookups, since no quoting is ever needed in their key strings.
6838
6839
6840
6841
6842 .section "More about dnsdb" "SECTdnsdb"
6843 .cindex "dnsdb lookup"
6844 .cindex "lookup" "dnsdb"
6845 .cindex "DNS" "as a lookup type"
6846 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
6847 of a record type and a domain name, separated by an equals sign. For example,
6848 an expansion string could contain:
6849 .code
6850 ${lookup dnsdb{mx=a.b.example}{$value}fail}
6851 .endd
6852 If the lookup succeeds, the result is placed in &$value$&, which in this case
6853 is used on its own as the result. If the lookup does not succeed, the
6854 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
6855 &<<SECTforexpfai>>& for an explanation of what this means.
6856
6857 The supported DNS record types are A, CNAME, MX, NS, PTR, SPF, SRV, TLSA and TXT,
6858 and, when Exim is compiled with IPv6 support, AAAA (and A6 if that is also
6859 configured). If no type is given, TXT is assumed. When the type is PTR,
6860 the data can be an IP address, written as normal; inversion and the addition of
6861 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
6862 .code
6863 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
6864 .endd
6865 If the data for a PTR record is not a syntactically valid IP address, it is not
6866 altered and nothing is added.
6867
6868 .cindex "MX record" "in &(dnsdb)& lookup"
6869 .cindex "SRV record" "in &(dnsdb)& lookup"
6870 For an MX lookup, both the preference value and the host name are returned for
6871 each record, separated by a space. For an SRV lookup, the priority, weight,
6872 port, and host name are returned for each record, separated by spaces.
6873
6874 For any record type, if multiple records are found (or, for A6 lookups, if a
6875 single record leads to multiple addresses), the data is returned as a
6876 concatenation, with newline as the default separator. The order, of course,
6877 depends on the DNS resolver. You can specify a different separator character
6878 between multiple records by putting a right angle-bracket followed immediately
6879 by the new separator at the start of the query. For example:
6880 .code
6881 ${lookup dnsdb{>: a=host1.example}}
6882 .endd
6883 It is permitted to specify a space as the separator character. Further
6884 white space is ignored.
6885
6886 .cindex "TXT record" "in &(dnsdb)& lookup"
6887 .cindex "SPF record" "in &(dnsdb)& lookup"
6888 For TXT records with multiple items of data, only the first item is returned,
6889 unless a separator for them is specified using a comma after the separator
6890 character followed immediately by the TXT record item separator. To concatenate
6891 items without a separator, use a semicolon instead. For SPF records the
6892 default behaviour is to concatenate multiple items without using a separator.
6893 .code
6894 ${lookup dnsdb{>\n,: txt=a.b.example}}
6895 ${lookup dnsdb{>\n; txt=a.b.example}}
6896 ${lookup dnsdb{spf=example.org}}
6897 .endd
6898 It is permitted to specify a space as the separator character. Further
6899 white space is ignored.
6900
6901 .section "Pseudo dnsdb record types" "SECID66"
6902 .cindex "MX record" "in &(dnsdb)& lookup"
6903 By default, both the preference value and the host name are returned for
6904 each MX record, separated by a space. If you want only host names, you can use
6905 the pseudo-type MXH:
6906 .code
6907 ${lookup dnsdb{mxh=a.b.example}}
6908 .endd
6909 In this case, the preference values are omitted, and just the host names are
6910 returned.
6911
6912 .cindex "name server for enclosing domain"
6913 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
6914 records on the given domain, but if none are found, it removes the first
6915 component of the domain name, and tries again. This process continues until NS
6916 records are found or there are no more components left (or there is a DNS
6917 error). In other words, it may return the name servers for a top-level domain,
6918 but it never returns the root name servers. If there are no NS records for the
6919 top-level domain, the lookup fails. Consider these examples:
6920 .code
6921 ${lookup dnsdb{zns=xxx.quercite.com}}
6922 ${lookup dnsdb{zns=xxx.edu}}
6923 .endd
6924 Assuming that in each case there are no NS records for the full domain name,
6925 the first returns the name servers for &%quercite.com%&, and the second returns
6926 the name servers for &%edu%&.
6927
6928 You should be careful about how you use this lookup because, unless the
6929 top-level domain does not exist, the lookup always returns some host names. The
6930 sort of use to which this might be put is for seeing if the name servers for a
6931 given domain are on a blacklist. You can probably assume that the name servers
6932 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
6933 such a list.
6934
6935 .cindex "CSA" "in &(dnsdb)& lookup"
6936 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
6937 records according to the CSA rules, which are described in section
6938 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
6939 not sufficient because of the extra parent domain search behaviour of CSA. The
6940 result of a successful lookup such as:
6941 .code
6942 ${lookup dnsdb {csa=$sender_helo_name}}
6943 .endd
6944 has two space-separated fields: an authorization code and a target host name.
6945 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
6946 authorization required but absent, or &"?"& for unknown.
6947
6948 .cindex "A+" "in &(dnsdb)& lookup"
6949 The pseudo-type A+ performs an A6 lookup (if configured) followed by an AAAA
6950 and then an A lookup. All results are returned; defer processing
6951 (see below) is handled separately for each lookup. Example:
6952 .code
6953 ${lookup dnsdb {>; a+=$sender_helo_name}}
6954 .endd
6955
6956
6957 .section "Multiple dnsdb lookups" "SECID67"
6958 In the previous sections, &(dnsdb)& lookups for a single domain are described.
6959 However, you can specify a list of domains or IP addresses in a single
6960 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
6961 the default separator, but with the ability to change this. For example:
6962 .code
6963 ${lookup dnsdb{one.domain.com:two.domain.com}}
6964 ${lookup dnsdb{a=one.host.com:two.host.com}}
6965 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
6966 .endd
6967 In order to retain backwards compatibility, there is one special case: if
6968 the lookup type is PTR and no change of separator is specified, Exim looks
6969 to see if the rest of the string is precisely one IPv6 address. In this
6970 case, it does not treat it as a list.
6971
6972 The data from each lookup is concatenated, with newline separators by default,
6973 in the same way that multiple DNS records for a single item are handled. A
6974 different separator can be specified, as described above.
6975
6976 Modifiers for &(dnsdb)& lookups are givien by optional keywords,
6977 each followed by a comma,
6978 that may appear before the record type.
6979
6980 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
6981 temporary DNS error for any of them, the behaviour is controlled by
6982 a defer-option modifier.
6983 The possible keywords are
6984 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
6985 With &"strict"& behaviour, any temporary DNS error causes the
6986 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
6987 ignored, and the behaviour is as if the DNS lookup failed to find anything.
6988 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
6989 error causes the whole lookup to defer only if none of the other lookups
6990 succeed. The default is &"lax"&, so the following lookups are equivalent:
6991 .code
6992 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
6993 ${lookup dnsdb{a=one.host.com:two.host.com}}
6994 .endd
6995 Thus, in the default case, as long as at least one of the DNS lookups
6996 yields some data, the lookup succeeds.
6997
6998 .new
6999 .cindex "DNSSEC" "dns lookup"
7000 Use of &(DNSSEC)& is controlled by a dnssec modifier.
7001 The possible keywords are
7002 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
7003 With &"strict"& or &"lax"& DNSSEC information is requested
7004 with the lookup.
7005 With &"strict"& a response from the DNS resolver that
7006 is not labelled as authenticated data
7007 is treated as equivalent to a temporary DNS error.
7008 The default is &"never"&.
7009
7010 See also the &$lookup_dnssec_authenticated$& variable.
7011 .wen
7012
7013
7014
7015
7016 .section "More about LDAP" "SECTldap"
7017 .cindex "LDAP" "lookup, more about"
7018 .cindex "lookup" "LDAP"
7019 .cindex "Solaris" "LDAP"
7020 The original LDAP implementation came from the University of Michigan; this has
7021 become &"Open LDAP"&, and there are now two different releases. Another
7022 implementation comes from Netscape, and Solaris 7 and subsequent releases
7023 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7024 the lookup function level, their error handling is different. For this reason
7025 it is necessary to set a compile-time variable when building Exim with LDAP, to
7026 indicate which LDAP library is in use. One of the following should appear in
7027 your &_Local/Makefile_&:
7028 .code
7029 LDAP_LIB_TYPE=UMICHIGAN
7030 LDAP_LIB_TYPE=OPENLDAP1
7031 LDAP_LIB_TYPE=OPENLDAP2
7032 LDAP_LIB_TYPE=NETSCAPE
7033 LDAP_LIB_TYPE=SOLARIS
7034 .endd
7035 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7036 same interface as the University of Michigan version.
7037
7038 There are three LDAP lookup types in Exim. These behave slightly differently in
7039 the way they handle the results of a query:
7040
7041 .ilist
7042 &(ldap)& requires the result to contain just one entry; if there are more, it
7043 gives an error.
7044 .next
7045 &(ldapdn)& also requires the result to contain just one entry, but it is the
7046 Distinguished Name that is returned rather than any attribute values.
7047 .next
7048 &(ldapm)& permits the result to contain more than one entry; the attributes
7049 from all of them are returned.
7050 .endlist
7051
7052
7053 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7054 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7055 the data returned by a successful lookup is described in the next section.
7056 First we explain how LDAP queries are coded.
7057
7058
7059 .section "Format of LDAP queries" "SECTforldaque"
7060 .cindex "LDAP" "query format"
7061 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7062 the configuration of a &(redirect)& router one might have this setting:
7063 .code
7064 data = ${lookup ldap \
7065 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7066 c=UK?mailbox?base?}}
7067 .endd
7068 .cindex "LDAP" "with TLS"
7069 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7070 secure (encrypted) LDAP connections. The second of these ensures that an
7071 encrypted TLS connection is used.
7072
7073 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7074 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7075 See the &%ldap_start_tls%& option.
7076
7077 .new
7078 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7079 controlled. Every part of the TLS configuration can be configured by settings in
7080 &_exim.conf_&. Depending on the version of the client libraries installed on
7081 your system, some of the initialization may have required setting options in
7082 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7083 certificates. This revealed a nuance where the current UID that exim was
7084 running as could affect which config files it read. With Exim 4.83, these
7085 methods become optional, only taking effect if not specifically set in
7086 &_exim.conf_&.
7087 .wen
7088
7089
7090 .section "LDAP quoting" "SECID68"
7091 .cindex "LDAP" "quoting"
7092 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7093 and the second because the LDAP query is represented as a URL. Furthermore,
7094 within an LDAP query, two different kinds of quoting are required. For this
7095 reason, there are two different LDAP-specific quoting operators.
7096
7097 The &%quote_ldap%& operator is designed for use on strings that are part of
7098 filter specifications. Conceptually, it first does the following conversions on
7099 the string:
7100 .code
7101 * => \2A
7102 ( => \28
7103 ) => \29
7104 \ => \5C
7105 .endd
7106 in accordance with RFC 2254. The resulting string is then quoted according
7107 to the rules for URLs, that is, all non-alphanumeric characters except
7108 .code
7109 ! $ ' - . _ ( ) * +
7110 .endd
7111 are converted to their hex values, preceded by a percent sign. For example:
7112 .code
7113 ${quote_ldap: a(bc)*, a<yz>; }
7114 .endd
7115 yields
7116 .code
7117 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7118 .endd
7119 Removing the URL quoting, this is (with a leading and a trailing space):
7120 .code
7121 a\28bc\29\2A, a<yz>;
7122 .endd
7123 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7124 base DN specifications in queries. Conceptually, it first converts the string
7125 by inserting a backslash in front of any of the following characters:
7126 .code
7127 , + " \ < > ;
7128 .endd
7129 It also inserts a backslash before any leading spaces or # characters, and
7130 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7131 is then quoted according to the rules for URLs. For example:
7132 .code
7133 ${quote_ldap_dn: a(bc)*, a<yz>; }
7134 .endd
7135 yields
7136 .code
7137 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7138 .endd
7139 Removing the URL quoting, this is (with a trailing space):
7140 .code
7141 \ a(bc)*\, a\<yz\>\;\
7142 .endd
7143 There are some further comments about quoting in the section on LDAP
7144 authentication below.
7145
7146
7147 .section "LDAP connections" "SECID69"
7148 .cindex "LDAP" "connections"
7149 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7150 is in use, via a Unix domain socket. The example given above does not specify
7151 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7152 by starting it with
7153 .code
7154 ldap://<hostname>:<port>/...
7155 .endd
7156 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7157 used. When no server is specified in a query, a list of default servers is
7158 taken from the &%ldap_default_servers%& configuration option. This supplies a
7159 colon-separated list of servers which are tried in turn until one successfully
7160 handles a query, or there is a serious error. Successful handling either
7161 returns the requested data, or indicates that it does not exist. Serious errors
7162 are syntactical, or multiple values when only a single value is expected.
7163 Errors which cause the next server to be tried are connection failures, bind
7164 failures, and timeouts.
7165
7166 For each server name in the list, a port number can be given. The standard way
7167 of specifying a host and port is to use a colon separator (RFC 1738). Because
7168 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7169 doubled. For example
7170 .code
7171 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7172 .endd
7173 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7174 to the LDAP library with no server name, and the library's default (normally
7175 the local host) is used.
7176
7177 If you are using the OpenLDAP library, you can connect to an LDAP server using
7178 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7179 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7180 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7181 not available.
7182
7183 For this type of connection, instead of a host name for the server, a pathname
7184 for the socket is required, and the port number is not relevant. The pathname
7185 can be specified either as an item in &%ldap_default_servers%&, or inline in
7186 the query. In the former case, you can have settings such as
7187 .code
7188 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7189 .endd
7190 When the pathname is given in the query, you have to escape the slashes as
7191 &`%2F`& to fit in with the LDAP URL syntax. For example:
7192 .code
7193 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7194 .endd
7195 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7196 a pathname, it uses the Unix domain socket code, even if the query actually
7197 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7198 socket connection. This behaviour means that you can use a setting of
7199 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7200 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7201 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7202 backup host.
7203
7204 If an explicit &`ldapi`& type is given in a query when a host name is
7205 specified, an error is diagnosed. However, if there are more items in
7206 &%ldap_default_servers%&, they are tried. In other words:
7207
7208 .ilist
7209 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7210 interface.
7211 .next
7212 Using &`ldapi`& with a host name causes an error.
7213 .endlist
7214
7215
7216 Using &`ldapi`& with no host or path in the query, and no setting of
7217 &%ldap_default_servers%&, does whatever the library does by default.
7218
7219
7220
7221 .section "LDAP authentication and control information" "SECID70"
7222 .cindex "LDAP" "authentication"
7223 The LDAP URL syntax provides no way of passing authentication and other control
7224 information to the server. To make this possible, the URL in an LDAP query may
7225 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7226 spaces. If a value contains spaces it must be enclosed in double quotes, and
7227 when double quotes are used, backslash is interpreted in the usual way inside
7228 them. The following names are recognized:
7229 .display
7230 &`DEREFERENCE`& set the dereferencing parameter
7231 &`NETTIME `& set a timeout for a network operation
7232 &`USER `& set the DN, for authenticating the LDAP bind
7233 &`PASS `& set the password, likewise
7234 &`REFERRALS `& set the referrals parameter
7235 .new
7236 &`SERVERS `& set alternate server list for this query only
7237 .wen
7238 &`SIZE `& set the limit for the number of entries returned
7239 &`TIME `& set the maximum waiting time for a query
7240 .endd
7241 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7242 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7243 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7244 library from trying to follow referrals issued by the LDAP server.
7245
7246 The name CONNECT is an obsolete name for NETTIME, retained for
7247 backwards compatibility. This timeout (specified as a number of seconds) is
7248 enforced from the client end for operations that can be carried out over a
7249 network. Specifically, it applies to network connections and calls to the
7250 &'ldap_result()'& function. If the value is greater than zero, it is used if
7251 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7252 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7253 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7254 Netscape SDK; for OpenLDAP no action is taken.
7255
7256 The TIME parameter (also a number of seconds) is passed to the server to
7257 set a server-side limit on the time taken to complete a search.
7258
7259 .new
7260 The SERVERS parameter allows you to specify an alternate list of ldap servers
7261 to use for an individual lookup. The global ldap_servers option provides a
7262 default list of ldap servers, and a single lookup can specify a single ldap
7263 server to use. But when you need to do a lookup with a list of servers that is
7264 different than the default list (maybe different order, maybe a completely
7265 different set of servers), the SERVERS parameter allows you to specify this
7266 alternate list.
7267 .wen
7268
7269 Here is an example of an LDAP query in an Exim lookup that uses some of these
7270 values. This is a single line, folded to fit on the page:
7271 .code
7272 ${lookup ldap
7273 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7274 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7275 {$value}fail}
7276 .endd
7277 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7278 any of the auxiliary data. Exim configuration settings that include lookups
7279 which contain password information should be preceded by &"hide"& to prevent
7280 non-admin users from using the &%-bP%& option to see their values.
7281
7282 The auxiliary data items may be given in any order. The default is no
7283 connection timeout (the system timeout is used), no user or password, no limit
7284 on the number of entries returned, and no time limit on queries.
7285
7286 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7287 removes any URL quoting that it may contain before passing it LDAP. Apparently
7288 some libraries do this for themselves, but some do not. Removing the URL
7289 quoting has two advantages:
7290
7291 .ilist
7292 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7293 DNs as with DNs inside actual queries.
7294 .next
7295 It permits spaces inside USER= DNs.
7296 .endlist
7297
7298 For example, a setting such as
7299 .code
7300 USER=cn=${quote_ldap_dn:$1}
7301 .endd
7302 should work even if &$1$& contains spaces.
7303
7304 Expanded data for the PASS= value should be quoted using the &%quote%&
7305 expansion operator, rather than the LDAP quote operators. The only reason this
7306 field needs quoting is to ensure that it conforms to the Exim syntax, which
7307 does not allow unquoted spaces. For example:
7308 .code
7309 PASS=${quote:$3}
7310 .endd
7311 The LDAP authentication mechanism can be used to check passwords as part of
7312 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7313 &<<CHAPexpand>>&.
7314
7315
7316
7317 .section "Format of data returned by LDAP" "SECID71"
7318 .cindex "LDAP" "returned data formats"
7319 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7320 as a sequence of values, for example
7321 .code
7322 cn=manager, o=University of Cambridge, c=UK
7323 .endd
7324 The &(ldap)& lookup type generates an error if more than one entry matches the
7325 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7326 the result between the data from different entries. It is possible for multiple
7327 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7328 you know that whatever values are returned all came from a single entry in the
7329 directory.
7330
7331 In the common case where you specify a single attribute in your LDAP query, the
7332 result is not quoted, and does not contain the attribute name. If the attribute
7333 has multiple values, they are separated by commas.
7334
7335 If you specify multiple attributes, the result contains space-separated, quoted
7336 strings, each preceded by the attribute name and an equals sign. Within the
7337 quotes, the quote character, backslash, and newline are escaped with
7338 backslashes, and commas are used to separate multiple values for the attribute.
7339 Apart from the escaping, the string within quotes takes the same form as the
7340 output when a single attribute is requested. Specifying no attributes is the
7341 same as specifying all of an entry's attributes.
7342
7343 Here are some examples of the output format. The first line of each pair is an
7344 LDAP query, and the second is the data that is returned. The attribute called
7345 &%attr1%& has two values, whereas &%attr2%& has only one value:
7346 .code
7347 ldap:///o=base?attr1?sub?(uid=fred)
7348 value1.1, value1.2
7349
7350 ldap:///o=base?attr2?sub?(uid=fred)
7351 value two
7352
7353 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7354 attr1="value1.1, value1.2" attr2="value two"
7355
7356 ldap:///o=base??sub?(uid=fred)
7357 objectClass="top" attr1="value1.1, value1.2" attr2="value two"
7358 .endd
7359 The &%extract%& operator in string expansions can be used to pick out
7360 individual fields from data that consists of &'key'&=&'value'& pairs. You can
7361 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7362 results of LDAP lookups.
7363
7364
7365
7366
7367 .section "More about NIS+" "SECTnisplus"
7368 .cindex "NIS+ lookup type"
7369 .cindex "lookup" "NIS+"
7370 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7371 and field name. If this is given, the result of a successful query is the
7372 contents of the named field; otherwise the result consists of a concatenation
7373 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
7374 values containing spaces are quoted. For example, the query
7375 .code
7376 [name=mg1456],passwd.org_dir
7377 .endd
7378 might return the string
7379 .code
7380 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
7381 home=/home/mg1456 shell=/bin/bash shadow=""
7382 .endd
7383 (split over two lines here to fit on the page), whereas
7384 .code
7385 [name=mg1456],passwd.org_dir:gcos
7386 .endd
7387 would just return
7388 .code
7389 Martin Guerre
7390 .endd
7391 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
7392 for the given indexed key. The effect of the &%quote_nisplus%& expansion
7393 operator is to double any quote characters within the text.
7394
7395
7396
7397 .section "SQL lookups" "SECTsql"
7398 .cindex "SQL lookup types"
7399 .cindex "MySQL" "lookup type"
7400 .cindex "PostgreSQL lookup type"
7401 .cindex "lookup" "MySQL"
7402 .cindex "lookup" "PostgreSQL"
7403 .cindex "Oracle" "lookup type"
7404 .cindex "lookup" "Oracle"
7405 .cindex "InterBase lookup type"
7406 .cindex "lookup" "InterBase"
7407 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, and SQLite
7408 databases. Queries for these databases contain SQL statements, so an example
7409 might be
7410 .code
7411 ${lookup mysql{select mailbox from users where id='userx'}\
7412 {$value}fail}
7413 .endd
7414 If the result of the query contains more than one field, the data for each
7415 field in the row is returned, preceded by its name, so the result of
7416 .code
7417 ${lookup pgsql{select home,name from users where id='userx'}\
7418 {$value}}
7419 .endd
7420 might be
7421 .code
7422 home=/home/userx name="Mister X"
7423 .endd
7424 Empty values and values containing spaces are double quoted, with embedded
7425 quotes escaped by a backslash. If the result of the query contains just one
7426 field, the value is passed back verbatim, without a field name, for example:
7427 .code
7428 Mister X
7429 .endd
7430 If the result of the query yields more than one row, it is all concatenated,
7431 with a newline between the data for each row.
7432
7433
7434 .section "More about MySQL, PostgreSQL, Oracle, and InterBase" "SECID72"
7435 .cindex "MySQL" "lookup type"
7436 .cindex "PostgreSQL lookup type"
7437 .cindex "lookup" "MySQL"
7438 .cindex "lookup" "PostgreSQL"
7439 .cindex "Oracle" "lookup type"
7440 .cindex "lookup" "Oracle"
7441 .cindex "InterBase lookup type"
7442 .cindex "lookup" "InterBase"
7443 If any MySQL, PostgreSQL, Oracle, or InterBase lookups are used, the
7444 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, or &%ibase_servers%&
7445 option (as appropriate) must be set to a colon-separated list of server
7446 information.
7447 (For MySQL and PostgreSQL only, the global option need not be set if all
7448 queries contain their own server information &-- see section
7449 &<<SECTspeserque>>&.) Each item in the list is a slash-separated list of four
7450 items: host name, database name, user name, and password. In the case of
7451 Oracle, the host name field is used for the &"service name"&, and the database
7452 name field is not used and should be empty. For example:
7453 .code
7454 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
7455 .endd
7456 Because password data is sensitive, you should always precede the setting with
7457 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
7458 option. Here is an example where two MySQL servers are listed:
7459 .code
7460 hide mysql_servers = localhost/users/root/secret:\
7461 otherhost/users/root/othersecret
7462 .endd
7463 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
7464 because this is a colon-separated list, the colon has to be doubled. For each
7465 query, these parameter groups are tried in order until a connection is made and
7466 a query is successfully processed. The result of a query may be that no data is
7467 found, but that is still a successful query. In other words, the list of
7468 servers provides a backup facility, not a list of different places to look.
7469
7470 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
7471 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
7472 respectively, and the characters single-quote, double-quote, and backslash
7473 itself are escaped with backslashes. The &%quote_pgsql%& expansion operator, in
7474 addition, escapes the percent and underscore characters. This cannot be done
7475 for MySQL because these escapes are not recognized in contexts where these
7476 characters are not special.
7477
7478 .section "Specifying the server in the query" "SECTspeserque"
7479 For MySQL and PostgreSQL lookups (but not currently for Oracle and InterBase),
7480 it is possible to specify a list of servers with an individual query. This is
7481 done by starting the query with
7482 .display
7483 &`servers=`&&'server1:server2:server3:...'&&`;`&
7484 .endd
7485 Each item in the list may take one of two forms:
7486 .olist
7487 If it contains no slashes it is assumed to be just a host name. The appropriate
7488 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
7489 of the same name, and the remaining parameters (database, user, password) are
7490 taken from there.
7491 .next
7492 If it contains any slashes, it is taken as a complete parameter set.
7493 .endlist
7494 The list of servers is used in exactly the same way as the global list.
7495 Once a connection to a server has happened and a query has been
7496 successfully executed, processing of the lookup ceases.
7497
7498 This feature is intended for use in master/slave situations where updates
7499 are occurring and you want to update the master rather than a slave. If the
7500 master is in the list as a backup for reading, you might have a global setting
7501 like this:
7502 .code
7503 mysql_servers = slave1/db/name/pw:\
7504 slave2/db/name/pw:\
7505 master/db/name/pw
7506 .endd
7507 In an updating lookup, you could then write:
7508 .code
7509 ${lookup mysql{servers=master; UPDATE ...} }
7510 .endd
7511 That query would then be sent only to the master server. If, on the other hand,
7512 the master is not to be used for reading, and so is not present in the global
7513 option, you can still update it by a query of this form:
7514 .code
7515 ${lookup pgsql{servers=master/db/name/pw; UPDATE ...} }
7516 .endd
7517
7518
7519 .section "Special MySQL features" "SECID73"
7520 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
7521 causes a connection to the server on the local host by means of a Unix domain
7522 socket. An alternate socket can be specified in parentheses. The full syntax of
7523 each item in &%mysql_servers%& is:
7524 .display
7525 <&'hostname'&>::<&'port'&>(<&'socket name'&>)/<&'database'&>/&&&
7526 <&'user'&>/<&'password'&>
7527 .endd
7528 Any of the three sub-parts of the first field can be omitted. For normal use on
7529 the local host it can be left blank or set to just &"localhost"&.
7530
7531 No database need be supplied &-- but if it is absent here, it must be given in
7532 the queries.
7533
7534 If a MySQL query is issued that does not request any data (an insert, update,
7535 or delete command), the result of the lookup is the number of rows affected.
7536
7537 &*Warning*&: This can be misleading. If an update does not actually change
7538 anything (for example, setting a field to the value it already has), the result
7539 is zero because no rows are affected.
7540
7541
7542 .section "Special PostgreSQL features" "SECID74"
7543 PostgreSQL lookups can also use Unix domain socket connections to the database.
7544 This is usually faster and costs less CPU time than a TCP/IP connection.
7545 However it can be used only if the mail server runs on the same machine as the
7546 database server. A configuration line for PostgreSQL via Unix domain sockets
7547 looks like this:
7548 .code
7549 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
7550 .endd
7551 In other words, instead of supplying a host name, a path to the socket is
7552 given. The path name is enclosed in parentheses so that its slashes aren't
7553 visually confused with the delimiters for the other server parameters.
7554
7555 If a PostgreSQL query is issued that does not request any data (an insert,
7556 update, or delete command), the result of the lookup is the number of rows
7557 affected.
7558
7559 .section "More about SQLite" "SECTsqlite"
7560 .cindex "lookup" "SQLite"
7561 .cindex "sqlite lookup type"
7562 SQLite is different to the other SQL lookups because a file name is required in
7563 addition to the SQL query. An SQLite database is a single file, and there is no
7564 daemon as in the other SQL databases. The interface to Exim requires the name
7565 of the file, as an absolute path, to be given at the start of the query. It is
7566 separated from the query by white space. This means that the path name cannot
7567 contain white space. Here is a lookup expansion example:
7568 .code
7569 ${lookup sqlite {/some/thing/sqlitedb \
7570 select name from aliases where id='userx';}}
7571 .endd
7572 In a list, the syntax is similar. For example:
7573 .code
7574 domainlist relay_to_domains = sqlite;/some/thing/sqlitedb \
7575 select * from relays where ip='$sender_host_address';
7576 .endd
7577 The only character affected by the &%quote_sqlite%& operator is a single
7578 quote, which it doubles.
7579
7580 The SQLite library handles multiple simultaneous accesses to the database
7581 internally. Multiple readers are permitted, but only one process can
7582 update at once. Attempts to access the database while it is being updated
7583 are rejected after a timeout period, during which the SQLite library
7584 waits for the lock to be released. In Exim, the default timeout is set
7585 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
7586 option.
7587 .ecindex IIDfidalo1
7588 .ecindex IIDfidalo2
7589
7590
7591 . ////////////////////////////////////////////////////////////////////////////
7592 . ////////////////////////////////////////////////////////////////////////////
7593
7594 .chapter "Domain, host, address, and local part lists" &&&
7595 "CHAPdomhosaddlists" &&&
7596 "Domain, host, and address lists"
7597 .scindex IIDdohoadli "lists of domains; hosts; etc."
7598 A number of Exim configuration options contain lists of domains, hosts,
7599 email addresses, or local parts. For example, the &%hold_domains%& option
7600 contains a list of domains whose delivery is currently suspended. These lists
7601 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
7602 arguments to expansion conditions such as &%match_domain%&.
7603
7604 Each item in one of these lists is a pattern to be matched against a domain,
7605 host, email address, or local part, respectively. In the sections below, the
7606 different types of pattern for each case are described, but first we cover some
7607 general facilities that apply to all four kinds of list.
7608
7609
7610
7611 .section "Expansion of lists" "SECID75"
7612 .cindex "expansion" "of lists"
7613 Each list is expanded as a single string before it is used. The result of
7614 expansion must be a list, possibly containing empty items, which is split up
7615 into separate items for matching. By default, colon is the separator character,
7616 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
7617 &<<SECTempitelis>>& for details of the list syntax; the second of these
7618 discusses the way to specify empty list items.
7619
7620
7621 If the string expansion is forced to fail, Exim behaves as if the item it is
7622 testing (domain, host, address, or local part) is not in the list. Other
7623 expansion failures cause temporary errors.
7624
7625 If an item in a list is a regular expression, backslashes, dollars and possibly
7626 other special characters in the expression must be protected against
7627 misinterpretation by the string expander. The easiest way to do this is to use
7628 the &`\N`& expansion feature to indicate that the contents of the regular
7629 expression should not be expanded. For example, in an ACL you might have:
7630 .code
7631 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
7632 ${lookup{$domain}lsearch{/badsenders/bydomain}}
7633 .endd
7634 The first item is a regular expression that is protected from expansion by
7635 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
7636 senders based on the receiving domain.
7637
7638
7639
7640
7641 .section "Negated items in lists" "SECID76"
7642 .cindex "list" "negation"
7643 .cindex "negation" "in lists"
7644 Items in a list may be positive or negative. Negative items are indicated by a
7645 leading exclamation mark, which may be followed by optional white space. A list
7646 defines a set of items (domains, etc). When Exim processes one of these lists,
7647 it is trying to find out whether a domain, host, address, or local part
7648 (respectively) is in the set that is defined by the list. It works like this:
7649
7650 The list is scanned from left to right. If a positive item is matched, the
7651 subject that is being checked is in the set; if a negative item is matched, the
7652 subject is not in the set. If the end of the list is reached without the
7653 subject having matched any of the patterns, it is in the set if the last item
7654 was a negative one, but not if it was a positive one. For example, the list in
7655 .code
7656 domainlist relay_to_domains = !a.b.c : *.b.c
7657 .endd
7658 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
7659 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
7660 list is positive. However, if the setting were
7661 .code
7662 domainlist relay_to_domains = !a.b.c
7663 .endd
7664 then all domains other than &'a.b.c'& would match because the last item in the
7665 list is negative. In other words, a list that ends with a negative item behaves
7666 as if it had an extra item &`:*`& on the end.
7667
7668 Another way of thinking about positive and negative items in lists is to read
7669 the connector as &"or"& after a positive item and as &"and"& after a negative
7670 item.
7671
7672
7673
7674 .section "File names in lists" "SECTfilnamlis"
7675 .cindex "list" "file name in"
7676 If an item in a domain, host, address, or local part list is an absolute file
7677 name (beginning with a slash character), each line of the file is read and
7678 processed as if it were an independent item in the list, except that further
7679 file names are not allowed,
7680 and no expansion of the data from the file takes place.
7681 Empty lines in the file are ignored, and the file may also contain comment
7682 lines:
7683
7684 .ilist
7685 For domain and host lists, if a # character appears anywhere in a line of the
7686 file, it and all following characters are ignored.
7687 .next
7688 Because local parts may legitimately contain # characters, a comment in an
7689 address list or local part list file is recognized only if # is preceded by
7690 white space or the start of the line. For example:
7691 .code
7692 not#comment@x.y.z # but this is a comment
7693 .endd
7694 .endlist
7695
7696 Putting a file name in a list has the same effect as inserting each line of the
7697 file as an item in the list (blank lines and comments excepted). However, there
7698 is one important difference: the file is read each time the list is processed,
7699 so if its contents vary over time, Exim's behaviour changes.
7700
7701 If a file name is preceded by an exclamation mark, the sense of any match
7702 within the file is inverted. For example, if
7703 .code
7704 hold_domains = !/etc/nohold-domains
7705 .endd
7706 and the file contains the lines
7707 .code
7708 !a.b.c
7709 *.b.c
7710 .endd
7711 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
7712 any domain matching &`*.b.c`& is not.
7713
7714
7715
7716 .section "An lsearch file is not an out-of-line list" "SECID77"
7717 As will be described in the sections that follow, lookups can be used in lists
7718 to provide indexed methods of checking list membership. There has been some
7719 confusion about the way &(lsearch)& lookups work in lists. Because
7720 an &(lsearch)& file contains plain text and is scanned sequentially, it is
7721 sometimes thought that it is allowed to contain wild cards and other kinds of
7722 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
7723 always fixed strings, just as for any other single-key lookup type.
7724
7725 If you want to use a file to contain wild-card patterns that form part of a
7726 list, just give the file name on its own, without a search type, as described
7727 in the previous section. You could also use the &(wildlsearch)& or
7728 &(nwildlsearch)&, but there is no advantage in doing this.
7729
7730
7731
7732
7733 .section "Named lists" "SECTnamedlists"
7734 .cindex "named lists"
7735 .cindex "list" "named"
7736 A list of domains, hosts, email addresses, or local parts can be given a name
7737 which is then used to refer to the list elsewhere in the configuration. This is
7738 particularly convenient if the same list is required in several different
7739 places. It also allows lists to be given meaningful names, which can improve
7740 the readability of the configuration. For example, it is conventional to define
7741 a domain list called &'local_domains'& for all the domains that are handled
7742 locally on a host, using a configuration line such as
7743 .code
7744 domainlist local_domains = localhost:my.dom.example
7745 .endd
7746 Named lists are referenced by giving their name preceded by a plus sign, so,
7747 for example, a router that is intended to handle local domains would be
7748 configured with the line
7749 .code
7750 domains = +local_domains
7751 .endd
7752 The first router in a configuration is often one that handles all domains
7753 except the local ones, using a configuration with a negated item like this:
7754 .code
7755 dnslookup:
7756 driver = dnslookup
7757 domains = ! +local_domains
7758 transport = remote_smtp
7759 no_more
7760 .endd
7761 The four kinds of named list are created by configuration lines starting with
7762 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
7763 respectively. Then there follows the name that you are defining, followed by an
7764 equals sign and the list itself. For example:
7765 .code
7766 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
7767 addresslist bad_senders = cdb;/etc/badsenders
7768 .endd
7769 A named list may refer to other named lists:
7770 .code
7771 domainlist dom1 = first.example : second.example
7772 domainlist dom2 = +dom1 : third.example
7773 domainlist dom3 = fourth.example : +dom2 : fifth.example
7774 .endd
7775 &*Warning*&: If the last item in a referenced list is a negative one, the
7776 effect may not be what you intended, because the negation does not propagate
7777 out to the higher level. For example, consider:
7778 .code
7779 domainlist dom1 = !a.b
7780 domainlist dom2 = +dom1 : *.b
7781 .endd
7782 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
7783 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
7784 means it matches the second list as well. The effect is not the same as
7785 .code
7786 domainlist dom2 = !a.b : *.b
7787 .endd
7788 where &'x.y'& does not match. It's best to avoid negation altogether in
7789 referenced lists if you can.
7790
7791 Named lists may have a performance advantage. When Exim is routing an
7792 address or checking an incoming message, it caches the result of tests on named
7793 lists. So, if you have a setting such as
7794 .code
7795 domains = +local_domains
7796 .endd
7797 on several of your routers
7798 or in several ACL statements,
7799 the actual test is done only for the first one. However, the caching works only
7800 if there are no expansions within the list itself or any sublists that it
7801 references. In other words, caching happens only for lists that are known to be
7802 the same each time they are referenced.
7803
7804 By default, there may be up to 16 named lists of each type. This limit can be
7805 extended by changing a compile-time variable. The use of domain and host lists
7806 is recommended for concepts such as local domains, relay domains, and relay
7807 hosts. The default configuration is set up like this.
7808
7809
7810
7811 .section "Named lists compared with macros" "SECID78"
7812 .cindex "list" "named compared with macro"
7813 .cindex "macro" "compared with named list"
7814 At first sight, named lists might seem to be no different from macros in the
7815 configuration file. However, macros are just textual substitutions. If you
7816 write
7817 .code
7818 ALIST = host1 : host2
7819 auth_advertise_hosts = !ALIST
7820 .endd
7821 it probably won't do what you want, because that is exactly the same as
7822 .code
7823 auth_advertise_hosts = !host1 : host2
7824 .endd
7825 Notice that the second host name is not negated. However, if you use a host
7826 list, and write
7827 .code
7828 hostlist alist = host1 : host2
7829 auth_advertise_hosts = ! +alist
7830 .endd
7831 the negation applies to the whole list, and so that is equivalent to
7832 .code
7833 auth_advertise_hosts = !host1 : !host2
7834 .endd
7835
7836
7837 .section "Named list caching" "SECID79"
7838 .cindex "list" "caching of named"
7839 .cindex "caching" "named lists"
7840 While processing a message, Exim caches the result of checking a named list if
7841 it is sure that the list is the same each time. In practice, this means that
7842 the cache operates only if the list contains no $ characters, which guarantees
7843 that it will not change when it is expanded. Sometimes, however, you may have
7844 an expanded list that you know will be the same each time within a given
7845 message. For example:
7846 .code
7847 domainlist special_domains = \
7848 ${lookup{$sender_host_address}cdb{/some/file}}
7849 .endd
7850 This provides a list of domains that depends only on the sending host's IP
7851 address. If this domain list is referenced a number of times (for example,
7852 in several ACL lines, or in several routers) the result of the check is not
7853 cached by default, because Exim does not know that it is going to be the
7854 same list each time.
7855
7856 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
7857 cache the result anyway. For example:
7858 .code
7859 domainlist_cache special_domains = ${lookup{...
7860 .endd
7861 If you do this, you should be absolutely sure that caching is going to do
7862 the right thing in all cases. When in doubt, leave it out.
7863
7864
7865
7866 .section "Domain lists" "SECTdomainlist"
7867 .cindex "domain list" "patterns for"
7868 .cindex "list" "domain list"
7869 Domain lists contain patterns that are to be matched against a mail domain.
7870 The following types of item may appear in domain lists:
7871
7872 .ilist
7873 .cindex "primary host name"
7874 .cindex "host name" "matched in domain list"
7875 .oindex "&%primary_hostname%&"
7876 .cindex "domain list" "matching primary host name"
7877 .cindex "@ in a domain list"
7878 If a pattern consists of a single @ character, it matches the local host name,
7879 as set by the &%primary_hostname%& option (or defaulted). This makes it
7880 possible to use the same configuration file on several different hosts that
7881 differ only in their names.
7882 .next
7883 .cindex "@[] in a domain list"
7884 .cindex "domain list" "matching local IP interfaces"
7885 .cindex "domain literal"
7886 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
7887 in square brackets (as in an email address that contains a domain literal), but
7888 only if that IP address is recognized as local for email routing purposes. The
7889 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
7890 control which of a host's several IP addresses are treated as local.
7891 In today's Internet, the use of domain literals is controversial.
7892 .next
7893 .cindex "@mx_any"
7894 .cindex "@mx_primary"
7895 .cindex "@mx_secondary"
7896 .cindex "domain list" "matching MX pointers to local host"
7897 If a pattern consists of the string &`@mx_any`& it matches any domain that
7898 has an MX record pointing to the local host or to any host that is listed in
7899 .oindex "&%hosts_treat_as_local%&"
7900 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
7901 are similar, except that the first matches only when a primary MX target is the
7902 local host, and the second only when no primary MX target is the local host,
7903 but a secondary MX target is. &"Primary"& means an MX record with the lowest
7904 preference value &-- there may of course be more than one of them.
7905
7906 The MX lookup that takes place when matching a pattern of this type is
7907 performed with the resolver options for widening names turned off. Thus, for
7908 example, a single-component domain will &'not'& be expanded by adding the
7909 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
7910 options of the &(dnslookup)& router for a discussion of domain widening.
7911
7912 Sometimes you may want to ignore certain IP addresses when using one of these
7913 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
7914 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
7915 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
7916 on a router). For example:
7917 .code
7918 domains = @mx_any/ignore=127.0.0.1
7919 .endd
7920 This example matches any domain that has an MX record pointing to one of
7921 the local host's IP addresses other than 127.0.0.1.
7922
7923 The list of IP addresses is in fact processed by the same code that processes
7924 host lists, so it may contain CIDR-coded network specifications and it may also
7925 contain negative items.
7926
7927 Because the list of IP addresses is a sublist within a domain list, you have to
7928 be careful about delimiters if there is more than one address. Like any other
7929 list, the default delimiter can be changed. Thus, you might have:
7930 .code
7931 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
7932 an.other.domain : ...
7933 .endd
7934 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
7935 involved, it is easiest to change the delimiter for the main list as well:
7936 .code
7937 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
7938 an.other.domain ? ...
7939 .endd
7940 .next
7941 .cindex "asterisk" "in domain list"
7942 .cindex "domain list" "asterisk in"
7943 .cindex "domain list" "matching &""ends with""&"
7944 If a pattern starts with an asterisk, the remaining characters of the pattern
7945 are compared with the terminating characters of the domain. The use of &"*"& in
7946 domain lists differs from its use in partial matching lookups. In a domain
7947 list, the character following the asterisk need not be a dot, whereas partial
7948 matching works only in terms of dot-separated components. For example, a domain
7949 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
7950 &'cipher.key.ex'&.
7951
7952 .next
7953 .cindex "regular expressions" "in domain list"
7954 .cindex "domain list" "matching regular expression"
7955 If a pattern starts with a circumflex character, it is treated as a regular
7956 expression, and matched against the domain using a regular expression matching
7957 function. The circumflex is treated as part of the regular expression.
7958 Email domains are case-independent, so this regular expression match is by
7959 default case-independent, but you can make it case-dependent by starting it
7960 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
7961 are given in chapter &<<CHAPregexp>>&.
7962
7963 &*Warning*&: Because domain lists are expanded before being processed, you
7964 must escape any backslash and dollar characters in the regular expression, or
7965 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
7966 it is not to be expanded (unless you really do want to build a regular
7967 expression by expansion, of course).
7968 .next
7969 .cindex "lookup" "in domain list"
7970 .cindex "domain list" "matching by lookup"
7971 If a pattern starts with the name of a single-key lookup type followed by a
7972 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
7973 must be a file name in a suitable format for the lookup type. For example, for
7974 &"cdb;"& it must be an absolute path:
7975 .code
7976 domains = cdb;/etc/mail/local_domains.cdb
7977 .endd
7978 The appropriate type of lookup is done on the file using the domain name as the
7979 key. In most cases, the data that is looked up is not used; Exim is interested
7980 only in whether or not the key is present in the file. However, when a lookup
7981 is used for the &%domains%& option on a router
7982 or a &%domains%& condition in an ACL statement, the data is preserved in the
7983 &$domain_data$& variable and can be referred to in other router options or
7984 other statements in the same ACL.
7985
7986 .next
7987 Any of the single-key lookup type names may be preceded by
7988 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
7989 .code
7990 domains = partial-dbm;/partial/domains
7991 .endd
7992 This causes partial matching logic to be invoked; a description of how this
7993 works is given in section &<<SECTpartiallookup>>&.
7994
7995 .next
7996 .cindex "asterisk" "in lookup type"
7997 Any of the single-key lookup types may be followed by an asterisk. This causes
7998 a default lookup for a key consisting of a single asterisk to be done if the
7999 original lookup fails. This is not a useful feature when using a domain list to
8000 select particular domains (because any domain would match), but it might have
8001 value if the result of the lookup is being used via the &$domain_data$&
8002 expansion variable.
8003 .next
8004 If the pattern starts with the name of a query-style lookup type followed by a
8005 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8006 pattern must be an appropriate query for the lookup type, as described in
8007 chapter &<<CHAPfdlookup>>&. For example:
8008 .code
8009 hold_domains = mysql;select domain from holdlist \
8010 where domain = '${quote_mysql:$domain}';
8011 .endd
8012 In most cases, the data that is looked up is not used (so for an SQL query, for
8013 example, it doesn't matter what field you select). Exim is interested only in
8014 whether or not the query succeeds. However, when a lookup is used for the
8015 &%domains%& option on a router, the data is preserved in the &$domain_data$&
8016 variable and can be referred to in other options.
8017 .next
8018 .cindex "domain list" "matching literal domain name"
8019 If none of the above cases apply, a caseless textual comparison is made
8020 between the pattern and the domain.
8021 .endlist
8022
8023 Here is an example that uses several different kinds of pattern:
8024 .code
8025 domainlist funny_domains = \
8026 @ : \
8027 lib.unseen.edu : \
8028 *.foundation.fict.example : \
8029 \N^[1-2]\d{3}\.fict\.example$\N : \
8030 partial-dbm;/opt/data/penguin/book : \
8031 nis;domains.byname : \
8032 nisplus;[name=$domain,status=local],domains.org_dir
8033 .endd
8034 There are obvious processing trade-offs among the various matching modes. Using
8035 an asterisk is faster than a regular expression, and listing a few names
8036 explicitly probably is too. The use of a file or database lookup is expensive,
8037 but may be the only option if hundreds of names are required. Because the
8038 patterns are tested in order, it makes sense to put the most commonly matched
8039 patterns earlier.
8040
8041
8042
8043 .section "Host lists" "SECThostlist"
8044 .cindex "host list" "patterns in"
8045 .cindex "list" "host list"
8046 Host lists are used to control what remote hosts are allowed to do. For
8047 example, some hosts may be allowed to use the local host as a relay, and some
8048 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8049 two different ways, by name or by IP address. In a host list, some types of
8050 pattern are matched to a host name, and some are matched to an IP address.
8051 You need to be particularly careful with this when single-key lookups are
8052 involved, to ensure that the right value is being used as the key.
8053
8054
8055 .section "Special host list patterns" "SECID80"
8056 .cindex "empty item in hosts list"
8057 .cindex "host list" "empty string in"
8058 If a host list item is the empty string, it matches only when no remote host is
8059 involved. This is the case when a message is being received from a local
8060 process using SMTP on the standard input, that is, when a TCP/IP connection is
8061 not used.
8062
8063 .cindex "asterisk" "in host list"
8064 The special pattern &"*"& in a host list matches any host or no host. Neither
8065 the IP address nor the name is actually inspected.
8066
8067
8068
8069 .section "Host list patterns that match by IP address" "SECThoslispatip"
8070 .cindex "host list" "matching IP addresses"
8071 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8072 the incoming address actually appears in the IPv6 host as
8073 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8074 list, it is converted into a traditional IPv4 address first. (Not all operating
8075 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8076 concerns.)
8077
8078 The following types of pattern in a host list check the remote host by
8079 inspecting its IP address:
8080
8081 .ilist
8082 If the pattern is a plain domain name (not a regular expression, not starting
8083 with *, not a lookup of any kind), Exim calls the operating system function
8084 to find the associated IP address(es). Exim uses the newer
8085 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8086 This typically causes a forward DNS lookup of the name. The result is compared
8087 with the IP address of the subject host.
8088
8089 If there is a temporary problem (such as a DNS timeout) with the host name
8090 lookup, a temporary error occurs. For example, if the list is being used in an
8091 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8092 temporary SMTP error code. If no IP address can be found for the host name,
8093 what happens is described in section &<<SECTbehipnot>>& below.
8094
8095 .next
8096 .cindex "@ in a host list"
8097 If the pattern is &"@"&, the primary host name is substituted and used as a
8098 domain name, as just described.
8099
8100 .next
8101 If the pattern is an IP address, it is matched against the IP address of the
8102 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8103 IPv6 addresses can be given in colon-separated format, but the colons have to
8104 be doubled so as not to be taken as item separators when the default list
8105 separator is used. IPv6 addresses are recognized even when Exim is compiled
8106 without IPv6 support. This means that if they appear in a host list on an
8107 IPv4-only host, Exim will not treat them as host names. They are just addresses
8108 that can never match a client host.
8109
8110 .next
8111 .cindex "@[] in a host list"
8112 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8113 the local host. For example, if the local host is an IPv4 host with one
8114 interface address 10.45.23.56, these two ACL statements have the same effect:
8115 .code
8116 accept hosts = 127.0.0.1 : 10.45.23.56
8117 accept hosts = @[]
8118 .endd
8119 .next
8120 .cindex "CIDR notation"
8121 If the pattern is an IP address followed by a slash and a mask length (for
8122 example 10.11.42.0/24), it is matched against the IP address of the subject
8123 host under the given mask. This allows, an entire network of hosts to be
8124 included (or excluded) by a single item. The mask uses CIDR notation; it
8125 specifies the number of address bits that must match, starting from the most
8126 significant end of the address.
8127
8128 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8129 of a range of addresses. It is the number of bits in the network portion of the
8130 address. The above example specifies a 24-bit netmask, so it matches all 256
8131 addresses in the 10.11.42.0 network. An item such as
8132 .code
8133 192.168.23.236/31
8134 .endd
8135 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8136 32 for an IPv4 address is the same as no mask at all; just a single address
8137 matches.
8138
8139 Here is another example which shows an IPv4 and an IPv6 network:
8140 .code
8141 recipient_unqualified_hosts = 192.168.0.0/16: \
8142 3ffe::ffff::836f::::/48
8143 .endd
8144 The doubling of list separator characters applies only when these items
8145 appear inline in a host list. It is not required when indirecting via a file.
8146 For example:
8147 .code
8148 recipient_unqualified_hosts = /opt/exim/unqualnets
8149 .endd
8150 could make use of a file containing
8151 .code
8152 172.16.0.0/12
8153 3ffe:ffff:836f::/48
8154 .endd
8155 to have exactly the same effect as the previous example. When listing IPv6
8156 addresses inline, it is usually more convenient to use the facility for
8157 changing separator characters. This list contains the same two networks:
8158 .code
8159 recipient_unqualified_hosts = <; 172.16.0.0/12; \
8160 3ffe:ffff:836f::/48
8161 .endd
8162 The separator is changed to semicolon by the leading &"<;"& at the start of the
8163 list.
8164 .endlist
8165
8166
8167
8168 .section "Host list patterns for single-key lookups by host address" &&&
8169 "SECThoslispatsikey"
8170 .cindex "host list" "lookup of IP address"
8171 When a host is to be identified by a single-key lookup of its complete IP
8172 address, the pattern takes this form:
8173 .display
8174 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8175 .endd
8176 For example:
8177 .code
8178 hosts_lookup = net-cdb;/hosts-by-ip.db
8179 .endd
8180 The text form of the IP address of the subject host is used as the lookup key.
8181 IPv6 addresses are converted to an unabbreviated form, using lower case
8182 letters, with dots as separators because colon is the key terminator in
8183 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
8184 quoting the keys, but this is a facility that was added later.] The data
8185 returned by the lookup is not used.
8186
8187 .cindex "IP address" "masking"
8188 .cindex "host list" "masked IP address"
8189 Single-key lookups can also be performed using masked IP addresses, using
8190 patterns of this form:
8191 .display
8192 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8193 .endd
8194 For example:
8195 .code
8196 net24-dbm;/networks.db
8197 .endd
8198 The IP address of the subject host is masked using <&'number'&> as the mask
8199 length. A textual string is constructed from the masked value, followed by the
8200 mask, and this is used as the lookup key. For example, if the host's IP address
8201 is 192.168.34.6, the key that is looked up for the above example is
8202 &"192.168.34.0/24"&.
8203
8204 When an IPv6 address is converted to a string, dots are normally used instead
8205 of colons, so that keys in &(lsearch)& files need not contain colons (which
8206 terminate &(lsearch)& keys). This was implemented some time before the ability
8207 to quote keys was made available in &(lsearch)& files. However, the more
8208 recently implemented &(iplsearch)& files do require colons in IPv6 keys
8209 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
8210 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
8211 converted using colons and not dots. In all cases, full, unabbreviated IPv6
8212 addresses are always used.
8213
8214 Ideally, it would be nice to tidy up this anomalous situation by changing to
8215 colons in all cases, given that quoting is now available for &(lsearch)&.
8216 However, this would be an incompatible change that might break some existing
8217 configurations.
8218
8219 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
8220 IPv6 address) is not the same as specifying just &%net-%& without a number. In
8221 the former case the key strings include the mask value, whereas in the latter
8222 case the IP address is used on its own.
8223
8224
8225
8226 .section "Host list patterns that match by host name" "SECThoslispatnam"
8227 .cindex "host" "lookup failures"
8228 .cindex "unknown host name"
8229 .cindex "host list" "matching host name"
8230 There are several types of pattern that require Exim to know the name of the
8231 remote host. These are either wildcard patterns or lookups by name. (If a
8232 complete hostname is given without any wildcarding, it is used to find an IP
8233 address to match against, as described in section &<<SECThoslispatip>>&
8234 above.)
8235
8236 If the remote host name is not already known when Exim encounters one of these
8237 patterns, it has to be found from the IP address.
8238 Although many sites on the Internet are conscientious about maintaining reverse
8239 DNS data for their hosts, there are also many that do not do this.
8240 Consequently, a name cannot always be found, and this may lead to unwanted
8241 effects. Take care when configuring host lists with wildcarded name patterns.
8242 Consider what will happen if a name cannot be found.
8243
8244 Because of the problems of determining host names from IP addresses, matching
8245 against host names is not as common as matching against IP addresses.
8246
8247 By default, in order to find a host name, Exim first does a reverse DNS lookup;
8248 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
8249 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
8250 are done can be changed by setting the &%host_lookup_order%& option. For
8251 security, once Exim has found one or more names, it looks up the IP addresses
8252 for these names and compares them with the IP address that it started with.
8253 Only those names whose IP addresses match are accepted. Any other names are
8254 discarded. If no names are left, Exim behaves as if the host name cannot be
8255 found. In the most common case there is only one name and one IP address.
8256
8257 There are some options that control what happens if a host name cannot be
8258 found. These are described in section &<<SECTbehipnot>>& below.
8259
8260 .cindex "host" "alias for"
8261 .cindex "alias for host"
8262 As a result of aliasing, hosts may have more than one name. When processing any
8263 of the following types of pattern, all the host's names are checked:
8264
8265 .ilist
8266 .cindex "asterisk" "in host list"
8267 If a pattern starts with &"*"& the remainder of the item must match the end of
8268 the host name. For example, &`*.b.c`& matches all hosts whose names end in
8269 &'.b.c'&. This special simple form is provided because this is a very common
8270 requirement. Other kinds of wildcarding require the use of a regular
8271 expression.
8272 .next
8273 .cindex "regular expressions" "in host list"
8274 .cindex "host list" "regular expression in"
8275 If the item starts with &"^"& it is taken to be a regular expression which is
8276 matched against the host name. Host names are case-independent, so this regular
8277 expression match is by default case-independent, but you can make it
8278 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
8279 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
8280 example,
8281 .code
8282 ^(a|b)\.c\.d$
8283 .endd
8284 is a regular expression that matches either of the two hosts &'a.c.d'& or
8285 &'b.c.d'&. When a regular expression is used in a host list, you must take care
8286 that backslash and dollar characters are not misinterpreted as part of the
8287 string expansion. The simplest way to do this is to use &`\N`& to mark that
8288 part of the string as non-expandable. For example:
8289 .code
8290 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
8291 .endd
8292 &*Warning*&: If you want to match a complete host name, you must include the
8293 &`$`& terminating metacharacter in the regular expression, as in the above
8294 example. Without it, a match at the start of the host name is all that is
8295 required.
8296 .endlist
8297
8298
8299
8300
8301 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
8302 .cindex "host" "lookup failures, permanent"
8303 While processing a host list, Exim may need to look up an IP address from a
8304 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
8305 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
8306 behaviour when it fails to find the information it is seeking is the same.
8307
8308 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
8309 apply to temporary DNS errors, whose handling is described in the next section.
8310
8311 .cindex "&`+include_unknown`&"
8312 .cindex "&`+ignore_unknown`&"
8313 Exim parses a host list from left to right. If it encounters a permanent
8314 lookup failure in any item in the host list before it has found a match,
8315 Exim treats it as a failure and the default behavior is as if the host
8316 does not match the list. This may not always be what you want to happen.
8317 To change Exim's behaviour, the special items &`+include_unknown`& or
8318 &`+ignore_unknown`& may appear in the list (at top level &-- they are
8319 not recognized in an indirected file).
8320
8321 .ilist
8322 If any item that follows &`+include_unknown`& requires information that
8323 cannot found, Exim behaves as if the host does match the list. For example,
8324 .code
8325 host_reject_connection = +include_unknown:*.enemy.ex
8326 .endd
8327 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
8328 any hosts whose name it cannot find.
8329
8330 .next
8331 If any item that follows &`+ignore_unknown`& requires information that cannot
8332 be found, Exim ignores that item and proceeds to the rest of the list. For
8333 example:
8334 .code
8335 accept hosts = +ignore_unknown : friend.example : \
8336 192.168.4.5
8337 .endd
8338 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
8339 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
8340 name can be found for 192.168.4.5, it is rejected.
8341 .endlist
8342
8343 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
8344 list. The effect of each one lasts until the next, or until the end of the
8345 list.
8346
8347 .new
8348 .section "Mixing wildcarded host names and addresses in host lists" &&&
8349 "SECTmixwilhos"
8350 .cindex "host list" "mixing names and addresses in"
8351
8352 This section explains the host/ip processing logic with the same concepts
8353 as the previous section, but specifically addresses what happens when a
8354 wildcarded hostname is one of the items in the hostlist.
8355
8356 .ilist
8357 If you have name lookups or wildcarded host names and
8358 IP addresses in the same host list, you should normally put the IP
8359 addresses first. For example, in an ACL you could have:
8360 .code
8361 accept hosts = 10.9.8.7 : *.friend.example
8362 .endd
8363 The reason you normally would order it this way lies in the
8364 left-to-right way that Exim processes lists. It can test IP addresses
8365 without doing any DNS lookups, but when it reaches an item that requires
8366 a host name, it fails if it cannot find a host name to compare with the
8367 pattern. If the above list is given in the opposite order, the
8368 &%accept%& statement fails for a host whose name cannot be found, even
8369 if its IP address is 10.9.8.7.
8370
8371 .next
8372 If you really do want to do the name check first, and still recognize the IP
8373 address, you can rewrite the ACL like this:
8374 .code
8375 accept hosts = *.friend.example
8376 accept hosts = 10.9.8.7
8377 .endd
8378 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
8379 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
8380 &`+ignore_unknown`&, which was discussed in depth in the first example in
8381 this section.
8382 .endlist
8383 .wen
8384
8385
8386 .section "Temporary DNS errors when looking up host information" &&&
8387 "SECTtemdnserr"
8388 .cindex "host" "lookup failures, temporary"
8389 .cindex "&`+include_defer`&"
8390 .cindex "&`+ignore_defer`&"
8391 A temporary DNS lookup failure normally causes a defer action (except when
8392 &%dns_again_means_nonexist%& converts it into a permanent error). However,
8393 host lists can include &`+ignore_defer`& and &`+include_defer`&, analagous to
8394 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
8395 section. These options should be used with care, probably only in non-critical
8396 host lists such as whitelists.
8397
8398
8399
8400 .section "Host list patterns for single-key lookups by host name" &&&
8401 "SECThoslispatnamsk"
8402 .cindex "unknown host name"
8403 .cindex "host list" "matching host name"
8404 If a pattern is of the form
8405 .display
8406 <&'single-key-search-type'&>;<&'search-data'&>
8407 .endd
8408 for example
8409 .code
8410 dbm;/host/accept/list
8411 .endd
8412 a single-key lookup is performed, using the host name as its key. If the
8413 lookup succeeds, the host matches the item. The actual data that is looked up
8414 is not used.
8415
8416 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
8417 keys in the file, not IP addresses. If you want to do lookups based on IP
8418 addresses, you must precede the search type with &"net-"& (see section
8419 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
8420 two items in the same list, one doing an address lookup and one doing a name
8421 lookup, both using the same file.
8422
8423
8424
8425 .section "Host list patterns for query-style lookups" "SECID81"
8426 If a pattern is of the form
8427 .display
8428 <&'query-style-search-type'&>;<&'query'&>
8429 .endd
8430 the query is obeyed, and if it succeeds, the host matches the item. The actual
8431 data that is looked up is not used. The variables &$sender_host_address$& and
8432 &$sender_host_name$& can be used in the query. For example:
8433 .code
8434 hosts_lookup = pgsql;\
8435 select ip from hostlist where ip='$sender_host_address'
8436 .endd
8437 The value of &$sender_host_address$& for an IPv6 address contains colons. You
8438 can use the &%sg%& expansion item to change this if you need to. If you want to
8439 use masked IP addresses in database queries, you can use the &%mask%& expansion
8440 operator.
8441
8442 If the query contains a reference to &$sender_host_name$&, Exim automatically
8443 looks up the host name if it has not already done so. (See section
8444 &<<SECThoslispatnam>>& for comments on finding host names.)
8445
8446 Historical note: prior to release 4.30, Exim would always attempt to find a
8447 host name before running the query, unless the search type was preceded by
8448 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
8449 still recognized for query-style lookups, but its presence or absence has no
8450 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
8451 See section &<<SECThoslispatsikey>>&.)
8452
8453
8454
8455
8456
8457 .section "Address lists" "SECTaddresslist"
8458 .cindex "list" "address list"
8459 .cindex "address list" "empty item"
8460 .cindex "address list" "patterns"
8461 Address lists contain patterns that are matched against mail addresses. There
8462 is one special case to be considered: the sender address of a bounce message is
8463 always empty. You can test for this by providing an empty item in an address
8464 list. For example, you can set up a router to process bounce messages by
8465 using this option setting:
8466 .code
8467 senders = :
8468 .endd
8469 The presence of the colon creates an empty item. If you do not provide any
8470 data, the list is empty and matches nothing. The empty sender can also be
8471 detected by a regular expression that matches an empty string,
8472 and by a query-style lookup that succeeds when &$sender_address$& is empty.
8473
8474 Non-empty items in an address list can be straightforward email addresses. For
8475 example:
8476 .code
8477 senders = jbc@askone.example : hs@anacreon.example
8478 .endd
8479 A certain amount of wildcarding is permitted. If a pattern contains an @
8480 character, but is not a regular expression and does not begin with a
8481 semicolon-terminated lookup type (described below), the local part of the
8482 subject address is compared with the local part of the pattern, which may start
8483 with an asterisk. If the local parts match, the domain is checked in exactly
8484 the same way as for a pattern in a domain list. For example, the domain can be
8485 wildcarded, refer to a named list, or be a lookup:
8486 .code
8487 deny senders = *@*.spamming.site:\
8488 *@+hostile_domains:\
8489 bozo@partial-lsearch;/list/of/dodgy/sites:\
8490 *@dbm;/bad/domains.db
8491 .endd
8492 .cindex "local part" "starting with !"
8493 .cindex "address list" "local part starting with !"
8494 If a local part that begins with an exclamation mark is required, it has to be
8495 specified using a regular expression, because otherwise the exclamation mark is
8496 treated as a sign of negation, as is standard in lists.
8497
8498 If a non-empty pattern that is not a regular expression or a lookup does not
8499 contain an @ character, it is matched against the domain part of the subject
8500 address. The only two formats that are recognized this way are a literal
8501 domain, or a domain pattern that starts with *. In both these cases, the effect
8502 is the same as if &`*@`& preceded the pattern. For example:
8503 .code
8504 deny senders = enemy.domain : *.enemy.domain
8505 .endd
8506
8507 The following kinds of more complicated address list pattern can match any
8508 address, including the empty address that is characteristic of bounce message
8509 senders:
8510
8511 .ilist
8512 .cindex "regular expressions" "in address list"
8513 .cindex "address list" "regular expression in"
8514 If (after expansion) a pattern starts with &"^"&, a regular expression match is
8515 done against the complete address, with the pattern as the regular expression.
8516 You must take care that backslash and dollar characters are not misinterpreted
8517 as part of the string expansion. The simplest way to do this is to use &`\N`&
8518 to mark that part of the string as non-expandable. For example:
8519 .code
8520 deny senders = \N^.*this.*@example\.com$\N : \
8521 \N^\d{8}.+@spamhaus.example$\N : ...
8522 .endd
8523 The &`\N`& sequences are removed by the expansion, so these items do indeed
8524 start with &"^"& by the time they are being interpreted as address patterns.
8525
8526 .next
8527 .cindex "address list" "lookup for complete address"
8528 Complete addresses can be looked up by using a pattern that starts with a
8529 lookup type terminated by a semicolon, followed by the data for the lookup. For
8530 example:
8531 .code
8532 deny senders = cdb;/etc/blocked.senders : \
8533 mysql;select address from blocked where \
8534 address='${quote_mysql:$sender_address}'
8535 .endd
8536 Both query-style and single-key lookup types can be used. For a single-key
8537 lookup type, Exim uses the complete address as the key. However, empty keys are
8538 not supported for single-key lookups, so a match against the empty address
8539 always fails. This restriction does not apply to query-style lookups.
8540
8541 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
8542 cannot be used, and is ignored if specified, with an entry being written to the
8543 panic log.
8544 .cindex "*@ with single-key lookup"
8545 However, you can configure lookup defaults, as described in section
8546 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
8547 default. For example, with this lookup:
8548 .code
8549 accept senders = lsearch*@;/some/file
8550 .endd
8551 the file could contains lines like this:
8552 .code
8553 user1@domain1.example
8554 *@domain2.example
8555 .endd
8556 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
8557 that are tried is:
8558 .code
8559 nimrod@jaeger.example
8560 *@jaeger.example
8561 *
8562 .endd
8563 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
8564 would mean that every address matches, thus rendering the test useless.
8565
8566 &*Warning 2*&: Do not confuse these two kinds of item:
8567 .code
8568 deny recipients = dbm*@;/some/file
8569 deny recipients = *@dbm;/some/file
8570 .endd
8571 The first does a whole address lookup, with defaulting, as just described,
8572 because it starts with a lookup type. The second matches the local part and
8573 domain independently, as described in a bullet point below.
8574 .endlist
8575
8576
8577 The following kinds of address list pattern can match only non-empty addresses.
8578 If the subject address is empty, a match against any of these pattern types
8579 always fails.
8580
8581
8582 .ilist
8583 .cindex "@@ with single-key lookup"
8584 .cindex "address list" "@@ lookup type"
8585 .cindex "address list" "split local part and domain"
8586 If a pattern starts with &"@@"& followed by a single-key lookup item
8587 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
8588 split into a local part and a domain. The domain is looked up in the file. If
8589 it is not found, there is no match. If it is found, the data that is looked up
8590 from the file is treated as a colon-separated list of local part patterns, each
8591 of which is matched against the subject local part in turn.
8592
8593 .cindex "asterisk" "in address list"
8594 The lookup may be a partial one, and/or one involving a search for a default
8595 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
8596 patterns that are looked up can be regular expressions or begin with &"*"&, or
8597 even be further lookups. They may also be independently negated. For example,
8598 with
8599 .code
8600 deny senders = @@dbm;/etc/reject-by-domain
8601 .endd
8602 the data from which the DBM file is built could contain lines like
8603 .code
8604 baddomain.com: !postmaster : *
8605 .endd
8606 to reject all senders except &%postmaster%& from that domain.
8607
8608 .cindex "local part" "starting with !"
8609 If a local part that actually begins with an exclamation mark is required, it
8610 has to be specified using a regular expression. In &(lsearch)& files, an entry
8611 may be split over several lines by indenting the second and subsequent lines,
8612 but the separating colon must still be included at line breaks. White space
8613 surrounding the colons is ignored. For example:
8614 .code
8615 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
8616 spammer3 : spammer4
8617 .endd
8618 As in all colon-separated lists in Exim, a colon can be included in an item by
8619 doubling.
8620
8621 If the last item in the list starts with a right angle-bracket, the remainder
8622 of the item is taken as a new key to look up in order to obtain a continuation
8623 list of local parts. The new key can be any sequence of characters. Thus one
8624 might have entries like
8625 .code
8626 aol.com: spammer1 : spammer 2 : >*
8627 xyz.com: spammer3 : >*
8628 *: ^\d{8}$
8629 .endd
8630 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
8631 local parts for all domains, in addition to the specific local parts listed for
8632 each domain. Of course, using this feature costs another lookup each time a
8633 chain is followed, but the effort needed to maintain the data is reduced.
8634
8635 .cindex "loop" "in lookups"
8636 It is possible to construct loops using this facility, and in order to catch
8637 them, the chains may be no more than fifty items long.
8638
8639 .next
8640 The @@<&'lookup'&> style of item can also be used with a query-style
8641 lookup, but in this case, the chaining facility is not available. The lookup
8642 can only return a single list of local parts.
8643 .endlist
8644
8645 &*Warning*&: There is an important difference between the address list items
8646 in these two examples:
8647 .code
8648 senders = +my_list
8649 senders = *@+my_list
8650 .endd
8651 In the first one, &`my_list`& is a named address list, whereas in the second
8652 example it is a named domain list.
8653
8654
8655
8656
8657 .section "Case of letters in address lists" "SECTcasletadd"
8658 .cindex "case of local parts"
8659 .cindex "address list" "case forcing"
8660 .cindex "case forcing in address lists"
8661 Domains in email addresses are always handled caselessly, but for local parts
8662 case may be significant on some systems (see &%caseful_local_part%& for how
8663 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
8664 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
8665 blocking lists should be done in a case-independent manner. Since most address
8666 lists in Exim are used for this kind of control, Exim attempts to do this by
8667 default.
8668
8669 The domain portion of an address is always lowercased before matching it to an
8670 address list. The local part is lowercased by default, and any string
8671 comparisons that take place are done caselessly. This means that the data in
8672 the address list itself, in files included as plain file names, and in any file
8673 that is looked up using the &"@@"& mechanism, can be in any case. However, the
8674 keys in files that are looked up by a search type other than &(lsearch)& (which
8675 works caselessly) must be in lower case, because these lookups are not
8676 case-independent.
8677
8678 .cindex "&`+caseful`&"
8679 To allow for the possibility of caseful address list matching, if an item in
8680 an address list is the string &"+caseful"&, the original case of the local
8681 part is restored for any comparisons that follow, and string comparisons are no
8682 longer case-independent. This does not affect the domain, which remains in
8683 lower case. However, although independent matches on the domain alone are still
8684 performed caselessly, regular expressions that match against an entire address
8685 become case-sensitive after &"+caseful"& has been seen.
8686
8687
8688
8689 .section "Local part lists" "SECTlocparlis"
8690 .cindex "list" "local part list"
8691 .cindex "local part" "list"
8692 Case-sensitivity in local part lists is handled in the same way as for address
8693 lists, as just described. The &"+caseful"& item can be used if required. In a
8694 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
8695 set false, the subject is lowercased and the matching is initially
8696 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
8697 matching in the local part list, but not elsewhere in the router. If
8698 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
8699 option is case-sensitive from the start.
8700
8701 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
8702 comments are handled in the same way as address lists &-- they are recognized
8703 only if the # is preceded by white space or the start of the line.
8704 Otherwise, local part lists are matched in the same way as domain lists, except
8705 that the special items that refer to the local host (&`@`&, &`@[]`&,
8706 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
8707 Refer to section &<<SECTdomainlist>>& for details of the other available item
8708 types.
8709 .ecindex IIDdohoadli
8710
8711
8712
8713
8714 . ////////////////////////////////////////////////////////////////////////////
8715 . ////////////////////////////////////////////////////////////////////////////
8716
8717 .chapter "String expansions" "CHAPexpand"
8718 .scindex IIDstrexp "expansion" "of strings"
8719 Many strings in Exim's run time configuration are expanded before use. Some of
8720 them are expanded every time they are used; others are expanded only once.
8721
8722 When a string is being expanded it is copied verbatim from left to right except
8723 when a dollar or backslash character is encountered. A dollar specifies the
8724 start of a portion of the string that is interpreted and replaced as described
8725 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
8726 escape character, as described in the following section.
8727
8728 Whether a string is expanded depends upon the context. Usually this is solely
8729 dependent upon the option for which a value is sought; in this documentation,
8730 options for which string expansion is performed are marked with &dagger; after
8731 the data type. ACL rules always expand strings. A couple of expansion
8732 conditions do not expand some of the brace-delimited branches, for security
8733 reasons.
8734
8735
8736
8737 .section "Literal text in expanded strings" "SECTlittext"
8738 .cindex "expansion" "including literal text"
8739 An uninterpreted dollar can be included in an expanded string by putting a
8740 backslash in front of it. A backslash can be used to prevent any special
8741 character being treated specially in an expansion, including backslash itself.
8742 If the string appears in quotes in the configuration file, two backslashes are
8743 required because the quotes themselves cause interpretation of backslashes when
8744 the string is read in (see section &<<SECTstrings>>&).
8745
8746 .cindex "expansion" "non-expandable substrings"
8747 A portion of the string can specified as non-expandable by placing it between
8748 two occurrences of &`\N`&. This is particularly useful for protecting regular
8749 expressions, which often contain backslashes and dollar signs. For example:
8750 .code
8751 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
8752 .endd
8753 On encountering the first &`\N`&, the expander copies subsequent characters
8754 without interpretation until it reaches the next &`\N`& or the end of the
8755 string.
8756
8757
8758
8759 .section "Character escape sequences in expanded strings" "SECID82"
8760 .cindex "expansion" "escape sequences"
8761 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
8762 expanded string is recognized as an escape sequence for the character newline,
8763 carriage return, or tab, respectively. A backslash followed by up to three
8764 octal digits is recognized as an octal encoding for a single character, and a
8765 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
8766 encoding.
8767
8768 These escape sequences are also recognized in quoted strings when they are read
8769 in. Their interpretation in expansions as well is useful for unquoted strings,
8770 and for other cases such as looked-up strings that are then expanded.
8771
8772
8773 .section "Testing string expansions" "SECID83"
8774 .cindex "expansion" "testing"
8775 .cindex "testing" "string expansion"
8776 .oindex "&%-be%&"
8777 Many expansions can be tested by calling Exim with the &%-be%& option. This
8778 takes the command arguments, or lines from the standard input if there are no
8779 arguments, runs them through the string expansion code, and writes the results
8780 to the standard output. Variables based on configuration values are set up, but
8781 since no message is being processed, variables such as &$local_part$& have no
8782 value. Nevertheless the &%-be%& option can be useful for checking out file and
8783 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
8784 and &%nhash%&.
8785
8786 Exim gives up its root privilege when it is called with the &%-be%& option, and
8787 instead runs under the uid and gid it was called with, to prevent users from
8788 using &%-be%& for reading files to which they do not have access.
8789
8790 .oindex "&%-bem%&"
8791 If you want to test expansions that include variables whose values are taken
8792 from a message, there are two other options that can be used. The &%-bem%&
8793 option is like &%-be%& except that it is followed by a file name. The file is
8794 read as a message before doing the test expansions. For example:
8795 .code
8796 exim -bem /tmp/test.message '$h_subject:'
8797 .endd
8798 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
8799 Exim message identifier. For example:
8800 .code
8801 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
8802 .endd
8803 This loads the message from Exim's spool before doing the test expansions, and
8804 is therefore restricted to admin users.
8805
8806
8807 .section "Forced expansion failure" "SECTforexpfai"
8808 .cindex "expansion" "forced failure"
8809 A number of expansions that are described in the following section have
8810 alternative &"true"& and &"false"& substrings, enclosed in brace characters
8811 (which are sometimes called &"curly brackets"&). Which of the two strings is
8812 used depends on some condition that is evaluated as part of the expansion. If,
8813 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
8814 the entire string expansion fails in a way that can be detected by the code
8815 that requested the expansion. This is called &"forced expansion failure"&, and
8816 its consequences depend on the circumstances. In some cases it is no different
8817 from any other expansion failure, but in others a different action may be
8818 taken. Such variations are mentioned in the documentation of the option that is
8819 being expanded.
8820
8821
8822
8823
8824 .section "Expansion items" "SECTexpansionitems"
8825 The following items are recognized in expanded strings. White space may be used
8826 between sub-items that are keywords or substrings enclosed in braces inside an
8827 outer set of braces, to improve readability. &*Warning*&: Within braces,
8828 white space is significant.
8829
8830 .vlist
8831 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
8832 .cindex "expansion" "variables"
8833 Substitute the contents of the named variable, for example:
8834 .code
8835 $local_part
8836 ${domain}
8837 .endd
8838 The second form can be used to separate the name from subsequent alphanumeric
8839 characters. This form (using braces) is available only for variables; it does
8840 &'not'& apply to message headers. The names of the variables are given in
8841 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
8842 given, the expansion fails.
8843
8844 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
8845 .cindex "expansion" "operators"
8846 The string is first itself expanded, and then the operation specified by
8847 <&'op'&> is applied to it. For example:
8848 .code
8849 ${lc:$local_part}
8850 .endd
8851 The string starts with the first character after the colon, which may be
8852 leading white space. A list of operators is given in section &<<SECTexpop>>&
8853 below. The operator notation is used for simple expansion items that have just
8854 one argument, because it reduces the number of braces and therefore makes the
8855 string easier to understand.
8856
8857 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
8858 This item inserts &"basic"& header lines. It is described with the &%header%&
8859 expansion item below.
8860
8861
8862 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
8863 .cindex "expansion" "calling an acl"
8864 .cindex "&%acl%&" "call from expansion"
8865 The name and zero to nine argument strings are first expanded separately. The expanded
8866 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
8867 Any unused are made empty. The variable &$acl_narg$& is set to the number of
8868 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
8869 and may use the variables; if another acl expansion is used the values
8870 are restored after it returns. If the ACL sets
8871 a value using a "message =" modifier and returns accept or deny, the value becomes
8872 the result of the expansion.
8873 If no message is set and the ACL returns accept or deny
8874 the expansion result is an empty string.
8875 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
8876
8877
8878 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
8879 {*&<&'arg'&>&*}...}*&"
8880 .cindex &%dlfunc%&
8881 This expansion dynamically loads and then calls a locally-written C function.
8882 This functionality is available only if Exim is compiled with
8883 .code
8884 EXPAND_DLFUNC=yes
8885 .endd
8886 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
8887 object so that it doesn't reload the same object file in the same Exim process
8888 (but of course Exim does start new processes frequently).
8889
8890 There may be from zero to eight arguments to the function. When compiling
8891 a local function that is to be called in this way, &_local_scan.h_& should be
8892 included. The Exim variables and functions that are defined by that API
8893 are also available for dynamically loaded functions. The function itself
8894 must have the following type:
8895 .code
8896 int dlfunction(uschar **yield, int argc, uschar *argv[])
8897 .endd
8898 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
8899 function should return one of the following values:
8900
8901 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
8902 into the expanded string that is being built.
8903
8904 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
8905 from &'yield'&, if it is set.
8906
8907 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
8908 taken from &'yield'& if it is set.
8909
8910 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
8911
8912 When compiling a function that is to be used in this way with gcc,
8913 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
8914 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
8915
8916 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
8917 {*&<&'string3'&>&*}}*&"
8918 .cindex "expansion" "extracting substrings by key"
8919 .cindex "&%extract%&" "substrings by key"
8920 The key and <&'string1'&> are first expanded separately. Leading and trailing
8921 white space is removed from the key (but not from any of the strings). The key
8922 must not consist entirely of digits. The expanded <&'string1'&> must be of the
8923 form:
8924 .display
8925 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
8926 .endd
8927 .vindex "&$value$&"
8928 where the equals signs and spaces (but not both) are optional. If any of the
8929 values contain white space, they must be enclosed in double quotes, and any
8930 values that are enclosed in double quotes are subject to escape processing as
8931 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
8932 for the value that corresponds to the key. The search is case-insensitive. If
8933 the key is found, <&'string2'&> is expanded, and replaces the whole item;
8934 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
8935 variable &$value$& contains the value that has been extracted. Afterwards, it
8936 is restored to any previous value it might have had.
8937
8938 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
8939 key is not found. If {<&'string2'&>} is also omitted, the value that was
8940 extracted is used. Thus, for example, these two expansions are identical, and
8941 yield &"2001"&:
8942 .code
8943 ${extract{gid}{uid=1984 gid=2001}}
8944 ${extract{gid}{uid=1984 gid=2001}{$value}}
8945 .endd
8946 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
8947 appear, for example:
8948 .code
8949 ${extract{Z}{A=... B=...}{$value} fail }
8950 .endd
8951 This forces an expansion failure (see section &<<SECTforexpfai>>&);
8952 {<&'string2'&>} must be present for &"fail"& to be recognized.
8953
8954
8955 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
8956 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
8957 .cindex "expansion" "extracting substrings by number"
8958 .cindex "&%extract%&" "substrings by number"
8959 The <&'number'&> argument must consist entirely of decimal digits,
8960 apart from leading and trailing white space, which is ignored.
8961 This is what distinguishes this form of &%extract%& from the previous kind. It
8962 behaves in the same way, except that, instead of extracting a named field, it
8963 extracts from <&'string1'&> the field whose number is given as the first
8964 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
8965 <&'string3'&> as before.
8966
8967 The fields in the string are separated by any one of the characters in the
8968 separator string. These may include space or tab characters.
8969 The first field is numbered one. If the number is negative, the fields are
8970 counted from the end of the string, with the rightmost one numbered -1. If the
8971 number given is zero, the entire string is returned. If the modulus of the
8972 number is greater than the number of fields in the string, the result is the
8973 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
8974 provided. For example:
8975 .code
8976 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
8977 .endd
8978 yields &"42"&, and
8979 .code
8980 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
8981 .endd
8982 yields &"99"&. Two successive separators mean that the field between them is
8983 empty (for example, the fifth field above).
8984
8985
8986 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
8987 .cindex "list" "selecting by condition"
8988 .cindex "expansion" "selecting from list by condition"
8989 .vindex "&$item$&"
8990 After expansion, <&'string'&> is interpreted as a list, colon-separated by
8991 default, but the separator can be changed in the usual way. For each item
8992 in this list, its value is place in &$item$&, and then the condition is
8993 evaluated. If the condition is true, &$item$& is added to the output as an
8994 item in a new list; if the condition is false, the item is discarded. The
8995 separator used for the output list is the same as the one used for the
8996 input, but a separator setting is not included in the output. For example:
8997 .code
8998 ${filter{a:b:c}{!eq{$item}{b}}
8999 .endd
9000 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
9001 to what it was before. See also the &*map*& and &*reduce*& expansion items.
9002
9003
9004 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9005 .cindex "hash function" "textual"
9006 .cindex "expansion" "textual hash"
9007 This is a textual hashing function, and was the first to be implemented in
9008 early versions of Exim. In current releases, there are other hashing functions
9009 (numeric, MD5, and SHA-1), which are described below.
9010
9011 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
9012 <&'n'&>. If you are using fixed values for these numbers, that is, if
9013 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
9014 use the simpler operator notation that avoids some of the braces:
9015 .code
9016 ${hash_<n>_<m>:<string>}
9017 .endd
9018 The second number is optional (in both notations). If <&'n'&> is greater than
9019 or equal to the length of the string, the expansion item returns the string.
9020 Otherwise it computes a new string of length <&'n'&> by applying a hashing
9021 function to the string. The new string consists of characters taken from the
9022 first <&'m'&> characters of the string
9023 .code
9024 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
9025 .endd
9026 If <&'m'&> is not present the value 26 is used, so that only lower case
9027 letters appear. For example:
9028 .display
9029 &`$hash{3}{monty}} `& yields &`jmg`&
9030 &`$hash{5}{monty}} `& yields &`monty`&
9031 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
9032 .endd
9033
9034 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
9035 &*$h_*&<&'header&~name'&>&*:*&" &&&
9036 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9037 &*$bh_*&<&'header&~name'&>&*:*&" &&&
9038 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9039 &*$rh_*&<&'header&~name'&>&*:*&"
9040 .cindex "expansion" "header insertion"
9041 .vindex "&$header_$&"
9042 .vindex "&$bheader_$&"
9043 .vindex "&$rheader_$&"
9044 .cindex "header lines" "in expansion strings"
9045 .cindex "header lines" "character sets"
9046 .cindex "header lines" "decoding"
9047 Substitute the contents of the named message header line, for example
9048 .code
9049 $header_reply-to:
9050 .endd
9051 The newline that terminates a header line is not included in the expansion, but
9052 internal newlines (caused by splitting the header line over several physical
9053 lines) may be present.
9054
9055 The difference between &%rheader%&, &%bheader%&, and &%header%& is in the way
9056 the data in the header line is interpreted.
9057
9058 .ilist
9059 .cindex "white space" "in header lines"
9060 &%rheader%& gives the original &"raw"& content of the header line, with no
9061 processing at all, and without the removal of leading and trailing white space.
9062
9063 .next
9064 .cindex "base64 encoding" "in header lines"
9065 &%bheader%& removes leading and trailing white space, and then decodes base64
9066 or quoted-printable MIME &"words"& within the header text, but does no
9067 character set translation. If decoding of what looks superficially like a MIME
9068 &"word"& fails, the raw string is returned. If decoding
9069 .cindex "binary zero" "in header line"
9070 produces a binary zero character, it is replaced by a question mark &-- this is
9071 what Exim does for binary zeros that are actually received in header lines.
9072
9073 .next
9074 &%header%& tries to translate the string as decoded by &%bheader%& to a
9075 standard character set. This is an attempt to produce the same string as would
9076 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
9077 returned. Translation is attempted only on operating systems that support the
9078 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
9079 a system Makefile or in &_Local/Makefile_&.
9080 .endlist ilist
9081
9082 In a filter file, the target character set for &%header%& can be specified by a
9083 command of the following form:
9084 .code
9085 headers charset "UTF-8"
9086 .endd
9087 This command affects all references to &$h_$& (or &$header_$&) expansions in
9088 subsequently obeyed filter commands. In the absence of this command, the target
9089 character set in a filter is taken from the setting of the &%headers_charset%&
9090 option in the runtime configuration. The value of this option defaults to the
9091 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
9092 ISO-8859-1.
9093
9094 Header names follow the syntax of RFC 2822, which states that they may contain
9095 any printing characters except space and colon. Consequently, curly brackets
9096 &'do not'& terminate header names, and should not be used to enclose them as
9097 if they were variables. Attempting to do so causes a syntax error.
9098
9099 Only header lines that are common to all copies of a message are visible to
9100 this mechanism. These are the original header lines that are received with the
9101 message, and any that are added by an ACL statement or by a system
9102 filter. Header lines that are added to a particular copy of a message by a
9103 router or transport are not accessible.
9104
9105 For incoming SMTP messages, no header lines are visible in ACLs that are obeyed
9106 before the DATA ACL, because the header structure is not set up until the
9107 message is received. Header lines that are added in a RCPT ACL (for example)
9108 are saved until the message's incoming header lines are available, at which
9109 point they are added. When a DATA ACL is running, however, header lines added
9110 by earlier ACLs are visible.
9111
9112 Upper case and lower case letters are synonymous in header names. If the
9113 following character is white space, the terminating colon may be omitted, but
9114 this is not recommended, because you may then forget it when it is needed. When
9115 white space terminates the header name, it is included in the expanded string.
9116 If the message does not contain the given header, the expansion item is
9117 replaced by an empty string. (See the &%def%& condition in section
9118 &<<SECTexpcond>>& for a means of testing for the existence of a header.)
9119
9120 If there is more than one header with the same name, they are all concatenated
9121 to form the substitution string, up to a maximum length of 64K. Unless
9122 &%rheader%& is being used, leading and trailing white space is removed from
9123 each header before concatenation, and a completely empty header is ignored. A
9124 newline character is then inserted between non-empty headers, but there is no
9125 newline at the very end. For the &%header%& and &%bheader%& expansion, for
9126 those headers that contain lists of addresses, a comma is also inserted at the
9127 junctions between headers. This does not happen for the &%rheader%& expansion.
9128
9129
9130 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
9131 .cindex "expansion" "hmac hashing"
9132 .cindex &%hmac%&
9133 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
9134 shared secret and some text into a message authentication code, as specified in
9135 RFC 2104. This differs from &`${md5:secret_text...}`& or
9136 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
9137 cryptographic hash, allowing for authentication that is not possible with MD5
9138 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
9139 present. For example:
9140 .code
9141 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
9142 .endd
9143 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
9144 produces:
9145 .code
9146 dd97e3ba5d1a61b5006108f8c8252953
9147 .endd
9148 As an example of how this might be used, you might put in the main part of
9149 an Exim configuration:
9150 .code
9151 SPAMSCAN_SECRET=cohgheeLei2thahw
9152 .endd
9153 In a router or a transport you could then have:
9154 .code
9155 headers_add = \
9156 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
9157 ${hmac{md5}{SPAMSCAN_SECRET}\
9158 {${primary_hostname},${message_exim_id},$h_message-id:}}
9159 .endd
9160 Then given a message, you can check where it was scanned by looking at the
9161 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
9162 this header line is authentic by recomputing the authentication code from the
9163 host name, message ID and the &'Message-id:'& header line. This can be done
9164 using Exim's &%-be%& option, or by other means, for example by using the
9165 &'hmac_md5_hex()'& function in Perl.
9166
9167
9168 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9169 .cindex "expansion" "conditional"
9170 .cindex "&%if%&, expansion item"
9171 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
9172 item; otherwise <&'string2'&> is used. The available conditions are described
9173 in section &<<SECTexpcond>>& below. For example:
9174 .code
9175 ${if eq {$local_part}{postmaster} {yes}{no} }
9176 .endd
9177 The second string need not be present; if it is not and the condition is not
9178 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
9179 be present instead of the second string (without any curly brackets). In this
9180 case, the expansion is forced to fail if the condition is not true (see section
9181 &<<SECTforexpfai>>&).
9182
9183 If both strings are omitted, the result is the string &`true`& if the condition
9184 is true, and the empty string if the condition is false. This makes it less
9185 cumbersome to write custom ACL and router conditions. For example, instead of
9186 .code
9187 condition = ${if >{$acl_m4}{3}{true}{false}}
9188 .endd
9189 you can use
9190 .code
9191 condition = ${if >{$acl_m4}{3}}
9192 .endd
9193
9194 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9195 .cindex "expansion" "string truncation"
9196 .cindex "&%length%& expansion item"
9197 The &%length%& item is used to extract the initial portion of a string. Both
9198 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
9199 you are using a fixed value for the number, that is, if <&'string1'&> does not
9200 change when expanded, you can use the simpler operator notation that avoids
9201 some of the braces:
9202 .code
9203 ${length_<n>:<string>}
9204 .endd
9205 The result of this item is either the first <&'n'&> characters or the whole
9206 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
9207 &%strlen%&, which gives the length of a string.
9208
9209
9210 .vitem "&*${listextract{*&<&'number'&>&*}&&&
9211 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9212 .cindex "expansion" "extracting list elements by number"
9213 .cindex "&%listextract%&" "extract list elements by number"
9214 .cindex "list" "extracting elements by number"
9215 The <&'number'&> argument must consist entirely of decimal digits,
9216 apart from an optional leading minus,
9217 and leading and trailing white space (which is ignored).
9218
9219 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9220 default, but the separator can be changed in the usual way.
9221
9222 The first field of the list is numbered one.
9223 If the number is negative, the fields are
9224 counted from the end of the list, with the rightmost one numbered -1.
9225 The numbered element of the list is extracted and placed in &$value$&,
9226 then <&'string2'&> is expanded as the result.
9227
9228 If the modulus of the
9229 number is zero or greater than the number of fields in the string,
9230 the result is the expansion of <&'string3'&>.
9231
9232 For example:
9233 .code
9234 ${listextract{2}{x:42:99}}
9235 .endd
9236 yields &"42"&, and
9237 .code
9238 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
9239 .endd
9240 yields &"result: 99"&.
9241
9242 If {<&'string3'&>} is omitted, an empty string is used for string3.
9243 If {<&'string2'&>} is also omitted, the value that was
9244 extracted is used.
9245 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
9246
9247
9248 .vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
9249 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9250 This is the first of one of two different types of lookup item, which are both
9251 described in the next item.
9252
9253 .vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
9254 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9255 .cindex "expansion" "lookup in"
9256 .cindex "file" "lookups"
9257 .cindex "lookup" "in expanded string"
9258 The two forms of lookup item specify data lookups in files and databases, as
9259 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
9260 lookups, and the second is used for query-style lookups. The <&'key'&>,
9261 <&'file'&>, and <&'query'&> strings are expanded before use.
9262
9263 If there is any white space in a lookup item which is part of a filter command,
9264 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
9265 other place where white space is significant, the lookup item must be enclosed
9266 in double quotes. The use of data lookups in users' filter files may be locked
9267 out by the system administrator.
9268
9269 .vindex "&$value$&"
9270 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
9271 During its expansion, the variable &$value$& contains the data returned by the
9272 lookup. Afterwards it reverts to the value it had previously (at the outer
9273 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
9274 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
9275 string on failure. If <&'string2'&> is provided, it can itself be a nested
9276 lookup, thus providing a mechanism for looking up a default value when the
9277 original lookup fails.
9278
9279 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
9280 data for the outer lookup while the parameters of the second lookup are
9281 expanded, and also while <&'string2'&> of the second lookup is expanded, should
9282 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
9283 appear, and in this case, if the lookup fails, the entire expansion is forced
9284 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
9285 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
9286 successful lookup, and nothing in the case of failure.
9287
9288 For single-key lookups, the string &"partial"& is permitted to precede the
9289 search type in order to do partial matching, and * or *@ may follow a search
9290 type to request default lookups if the key does not match (see sections
9291 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
9292
9293 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
9294 If a partial search is used, the variables &$1$& and &$2$& contain the wild
9295 and non-wild parts of the key during the expansion of the replacement text.
9296 They return to their previous values at the end of the lookup item.
9297
9298 This example looks up the postmaster alias in the conventional alias file:
9299 .code
9300 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
9301 .endd
9302 This example uses NIS+ to look up the full name of the user corresponding to
9303 the local part of an address, forcing the expansion to fail if it is not found:
9304 .code
9305 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
9306 {$value}fail}
9307 .endd
9308
9309
9310 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9311 .cindex "expansion" "list creation"
9312 .vindex "&$item$&"
9313 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9314 default, but the separator can be changed in the usual way. For each item
9315 in this list, its value is place in &$item$&, and then <&'string2'&> is
9316 expanded and added to the output as an item in a new list. The separator used
9317 for the output list is the same as the one used for the input, but a separator
9318 setting is not included in the output. For example:
9319 .code
9320 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
9321 .endd
9322 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
9323 value of &$item$& is restored to what it was before. See also the &*filter*&
9324 and &*reduce*& expansion items.
9325
9326 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9327 .cindex "expansion" "numeric hash"
9328 .cindex "hash function" "numeric"
9329 The three strings are expanded; the first two must yield numbers. Call them
9330 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9331 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9332 can use the simpler operator notation that avoids some of the braces:
9333 .code
9334 ${nhash_<n>_<m>:<string>}
9335 .endd
9336 The second number is optional (in both notations). If there is only one number,
9337 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
9338 processed by a div/mod hash function that returns two numbers, separated by a
9339 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
9340 example,
9341 .code
9342 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
9343 .endd
9344 returns the string &"6/33"&.
9345
9346
9347
9348 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
9349 .cindex "Perl" "use in expanded string"
9350 .cindex "expansion" "calling Perl from"
9351 This item is available only if Exim has been built to include an embedded Perl
9352 interpreter. The subroutine name and the arguments are first separately
9353 expanded, and then the Perl subroutine is called with those arguments. No
9354 additional arguments need be given; the maximum number permitted, including the
9355 name of the subroutine, is nine.
9356
9357 The return value of the subroutine is inserted into the expanded string, unless
9358 the return value is &%undef%&. In that case, the expansion fails in the same
9359 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
9360 Whatever you return is evaluated in a scalar context. For example, if you
9361 return the name of a Perl vector, the return value is the size of the vector,
9362 not its contents.
9363
9364 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
9365 with the error message that was passed to &%die%&. More details of the embedded
9366 Perl facility are given in chapter &<<CHAPperl>>&.
9367
9368 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
9369 out the use of this expansion item in filter files.
9370
9371
9372 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
9373 .cindex "&%prvs%& expansion item"
9374 The first argument is a complete email address and the second is secret
9375 keystring. The third argument, specifying a key number, is optional. If absent,
9376 it defaults to 0. The result of the expansion is a prvs-signed email address,
9377 to be typically used with the &%return_path%& option on an &(smtp)& transport
9378 as part of a bounce address tag validation (BATV) scheme. For more discussion
9379 and an example, see section &<<SECTverifyPRVS>>&.
9380
9381 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
9382 {*&<&'string'&>&*}}*&"
9383 .cindex "&%prvscheck%& expansion item"
9384 This expansion item is the complement of the &%prvs%& item. It is used for
9385 checking prvs-signed addresses. If the expansion of the first argument does not
9386 yield a syntactically valid prvs-signed address, the whole item expands to the
9387 empty string. When the first argument does expand to a syntactically valid
9388 prvs-signed address, the second argument is expanded, with the prvs-decoded
9389 version of the address and the key number extracted from the address in the
9390 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
9391
9392 These two variables can be used in the expansion of the second argument to
9393 retrieve the secret. The validity of the prvs-signed address is then checked
9394 against the secret. The result is stored in the variable &$prvscheck_result$&,
9395 which is empty for failure or &"1"& for success.
9396
9397 The third argument is optional; if it is missing, it defaults to an empty
9398 string. This argument is now expanded. If the result is an empty string, the
9399 result of the expansion is the decoded version of the address. This is the case
9400 whether or not the signature was valid. Otherwise, the result of the expansion
9401 is the expansion of the third argument.
9402
9403 All three variables can be used in the expansion of the third argument.
9404 However, once the expansion is complete, only &$prvscheck_result$& remains set.
9405 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
9406
9407 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
9408 .cindex "expansion" "inserting an entire file"
9409 .cindex "file" "inserting into expansion"
9410 .cindex "&%readfile%& expansion item"
9411 The file name and end-of-line string are first expanded separately. The file is
9412 then read, and its contents replace the entire item. All newline characters in
9413 the file are replaced by the end-of-line string if it is present. Otherwise,
9414 newlines are left in the string.
9415 String expansion is not applied to the contents of the file. If you want this,
9416 you must wrap the item in an &%expand%& operator. If the file cannot be read,
9417 the string expansion fails.
9418
9419 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
9420 locks out the use of this expansion item in filter files.
9421
9422
9423
9424 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
9425 {*&<&'timeout'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
9426 .cindex "expansion" "inserting from a socket"
9427 .cindex "socket, use of in expansion"
9428 .cindex "&%readsocket%& expansion item"
9429 This item inserts data from a Unix domain or Internet socket into the expanded
9430 string. The minimal way of using it uses just two arguments, as in these
9431 examples:
9432 .code
9433 ${readsocket{/socket/name}{request string}}
9434 ${readsocket{inet:some.host:1234}{request string}}
9435 .endd
9436 For a Unix domain socket, the first substring must be the path to the socket.
9437 For an Internet socket, the first substring must contain &`inet:`& followed by
9438 a host name or IP address, followed by a colon and a port, which can be a
9439 number or the name of a TCP port in &_/etc/services_&. An IP address may
9440 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
9441 example:
9442 .code
9443 ${readsocket{inet:[::1]:1234}{request string}}
9444 .endd
9445 Only a single host name may be given, but if looking it up yields more than
9446 one IP address, they are each tried in turn until a connection is made. For
9447 both kinds of socket, Exim makes a connection, writes the request string
9448 (unless it is an empty string) and reads from the socket until an end-of-file
9449 is read. A timeout of 5 seconds is applied. Additional, optional arguments
9450 extend what can be done. Firstly, you can vary the timeout. For example:
9451 .code
9452 ${readsocket{/socket/name}{request string}{3s}}
9453 .endd
9454 A fourth argument allows you to change any newlines that are in the data
9455 that is read, in the same way as for &%readfile%& (see above). This example
9456 turns them into spaces:
9457 .code
9458 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
9459 .endd
9460 As with all expansions, the substrings are expanded before the processing
9461 happens. Errors in these sub-expansions cause the expansion to fail. In
9462 addition, the following errors can occur:
9463
9464 .ilist
9465 Failure to create a socket file descriptor;
9466 .next
9467 Failure to connect the socket;
9468 .next
9469 Failure to write the request string;
9470 .next
9471 Timeout on reading from the socket.
9472 .endlist
9473
9474 By default, any of these errors causes the expansion to fail. However, if
9475 you supply a fifth substring, it is expanded and used when any of the above
9476 errors occurs. For example:
9477 .code
9478 ${readsocket{/socket/name}{request string}{3s}{\n}\
9479 {socket failure}}
9480 .endd
9481 You can test for the existence of a Unix domain socket by wrapping this
9482 expansion in &`${if exists`&, but there is a race condition between that test
9483 and the actual opening of the socket, so it is safer to use the fifth argument
9484 if you want to be absolutely sure of avoiding an expansion error for a
9485 non-existent Unix domain socket, or a failure to connect to an Internet socket.
9486
9487 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
9488 locks out the use of this expansion item in filter files.
9489
9490
9491 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9492 .cindex "expansion" "reducing a list to a scalar"
9493 .cindex "list" "reducing to a scalar"
9494 .vindex "&$value$&"
9495 .vindex "&$item$&"
9496 This operation reduces a list to a single, scalar string. After expansion,
9497 <&'string1'&> is interpreted as a list, colon-separated by default, but the
9498 separator can be changed in the usual way. Then <&'string2'&> is expanded and
9499 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
9500 list is assigned to &$item$& in turn, and <&'string3'&> is expanded for each of
9501 them. The result of that expansion is assigned to &$value$& before the next
9502 iteration. When the end of the list is reached, the final value of &$value$& is
9503 added to the expansion output. The &*reduce*& expansion item can be used in a
9504 number of ways. For example, to add up a list of numbers:
9505 .code
9506 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
9507 .endd
9508 The result of that expansion would be &`6`&. The maximum of a list of numbers
9509 can be found:
9510 .code
9511 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
9512 .endd
9513 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
9514 restored to what they were before. See also the &*filter*& and &*map*&
9515 expansion items.
9516
9517 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
9518 This item inserts &"raw"& header lines. It is described with the &%header%&
9519 expansion item above.
9520
9521 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
9522 {*&<&'string2'&>&*}}*&"
9523 .cindex "expansion" "running a command"
9524 .cindex "&%run%& expansion item"
9525 The command and its arguments are first expanded separately, and then the
9526 command is run in a separate process, but under the same uid and gid. As in
9527 other command executions from Exim, a shell is not used by default. If you want
9528 a shell, you must explicitly code it.
9529
9530 The standard input for the command exists, but is empty. The standard output
9531 and standard error are set to the same file descriptor.
9532 .cindex "return code" "from &%run%& expansion"
9533 .vindex "&$value$&"
9534 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
9535 and replaces the entire item; during this expansion, the standard output/error
9536 from the command is in the variable &$value$&. If the command fails,
9537 <&'string2'&>, if present, is expanded and used. Once again, during the
9538 expansion, the standard output/error from the command is in the variable
9539 &$value$&.
9540
9541 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
9542 can be the word &"fail"& (not in braces) to force expansion failure if the
9543 command does not succeed. If both strings are omitted, the result is contents
9544 of the standard output/error on success, and nothing on failure.
9545
9546 .vindex "&$run_in_acl$&"
9547 The standard output/error of the command is put in the variable &$value$&.
9548 In this ACL example, the output of a command is logged for the admin to
9549 troubleshoot:
9550 .code
9551 warn condition = ${run{/usr/bin/id}{yes}{no}}
9552 log_message = Output of id: $value
9553 .endd
9554 If the command requires shell idioms, such as the > redirect operator, the
9555 shell must be invoked directly, such as with:
9556 .code
9557 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
9558 .endd
9559
9560 .vindex "&$runrc$&"
9561 The return code from the command is put in the variable &$runrc$&, and this
9562 remains set afterwards, so in a filter file you can do things like this:
9563 .code
9564 if "${run{x y z}{}}$runrc" is 1 then ...
9565 elif $runrc is 2 then ...
9566 ...
9567 endif
9568 .endd
9569 If execution of the command fails (for example, the command does not exist),
9570 the return code is 127 &-- the same code that shells use for non-existent
9571 commands.
9572
9573 &*Warning*&: In a router or transport, you cannot assume the order in which
9574 option values are expanded, except for those preconditions whose order of
9575 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
9576 by the expansion of one option, and use it in another.
9577
9578 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
9579 out the use of this expansion item in filter files.
9580
9581
9582 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
9583 .cindex "expansion" "string substitution"
9584 .cindex "&%sg%& expansion item"
9585 This item works like Perl's substitution operator (s) with the global (/g)
9586 option; hence its name. However, unlike the Perl equivalent, Exim does not
9587 modify the subject string; instead it returns the modified string for insertion
9588 into the overall expansion. The item takes three arguments: the subject string,
9589 a regular expression, and a substitution string. For example:
9590 .code
9591 ${sg{abcdefabcdef}{abc}{xyz}}
9592 .endd
9593 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
9594 if any $ or \ characters are required in the regular expression or in the
9595 substitution string, they have to be escaped. For example:
9596 .code
9597 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
9598 .endd
9599 yields &"defabc"&, and
9600 .code
9601 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
9602 .endd
9603 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
9604 the regular expression from string expansion.
9605
9606
9607
9608 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9609 .cindex "&%substr%& expansion item"
9610 .cindex "substring extraction"
9611 .cindex "expansion" "substring extraction"
9612 The three strings are expanded; the first two must yield numbers. Call them
9613 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9614 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9615 can use the simpler operator notation that avoids some of the braces:
9616 .code
9617 ${substr_<n>_<m>:<string>}
9618 .endd
9619 The second number is optional (in both notations).
9620 If it is absent in the simpler format, the preceding underscore must also be
9621 omitted.
9622
9623 The &%substr%& item can be used to extract more general substrings than
9624 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
9625 length required. For example
9626 .code
9627 ${substr{3}{2}{$local_part}}
9628 .endd
9629 If the starting offset is greater than the string length the result is the
9630 null string; if the length plus starting offset is greater than the string
9631 length, the result is the right-hand part of the string, starting from the
9632 given offset. The first character in the string has offset zero.
9633
9634 The &%substr%& expansion item can take negative offset values to count
9635 from the right-hand end of its operand. The last character is offset -1, the
9636 second-last is offset -2, and so on. Thus, for example,
9637 .code
9638 ${substr{-5}{2}{1234567}}
9639 .endd
9640 yields &"34"&. If the absolute value of a negative offset is greater than the
9641 length of the string, the substring starts at the beginning of the string, and
9642 the length is reduced by the amount of overshoot. Thus, for example,
9643 .code
9644 ${substr{-5}{2}{12}}
9645 .endd
9646 yields an empty string, but
9647 .code
9648 ${substr{-3}{2}{12}}
9649 .endd
9650 yields &"1"&.
9651
9652 When the second number is omitted from &%substr%&, the remainder of the string
9653 is taken if the offset is positive. If it is negative, all characters in the
9654 string preceding the offset point are taken. For example, an offset of -1 and
9655 no length, as in these semantically identical examples:
9656 .code
9657 ${substr_-1:abcde}
9658 ${substr{-1}{abcde}}
9659 .endd
9660 yields all but the last character of the string, that is, &"abcd"&.
9661
9662
9663
9664 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
9665 {*&<&'replacements'&>&*}}*&"
9666 .cindex "expansion" "character translation"
9667 .cindex "&%tr%& expansion item"
9668 This item does single-character translation on its subject string. The second
9669 argument is a list of characters to be translated in the subject string. Each
9670 matching character is replaced by the corresponding character from the
9671 replacement list. For example
9672 .code
9673 ${tr{abcdea}{ac}{13}}
9674 .endd
9675 yields &`1b3de1`&. If there are duplicates in the second character string, the
9676 last occurrence is used. If the third string is shorter than the second, its
9677 last character is replicated. However, if it is empty, no translation takes
9678 place.
9679 .endlist
9680
9681
9682
9683 .section "Expansion operators" "SECTexpop"
9684 .cindex "expansion" "operators"
9685 For expansion items that perform transformations on a single argument string,
9686 the &"operator"& notation is used because it is simpler and uses fewer braces.
9687 The substring is first expanded before the operation is applied to it. The
9688 following operations can be performed:
9689
9690 .vlist
9691 .vitem &*${address:*&<&'string'&>&*}*&
9692 .cindex "expansion" "RFC 2822 address handling"
9693 .cindex "&%address%& expansion item"
9694 The string is interpreted as an RFC 2822 address, as it might appear in a
9695 header line, and the effective address is extracted from it. If the string does
9696 not parse successfully, the result is empty.
9697
9698
9699 .vitem &*${addresses:*&<&'string'&>&*}*&
9700 .cindex "expansion" "RFC 2822 address handling"
9701 .cindex "&%addresses%& expansion item"
9702 The string (after expansion) is interpreted as a list of addresses in RFC
9703 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
9704 operative address (&'local-part@domain'&) is extracted from each item, and the
9705 result of the expansion is a colon-separated list, with appropriate
9706 doubling of colons should any happen to be present in the email addresses.
9707 Syntactically invalid RFC2822 address items are omitted from the output.
9708
9709 It is possible to specify a character other than colon for the output
9710 separator by starting the string with > followed by the new separator
9711 character. For example:
9712 .code
9713 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
9714 .endd
9715 expands to &`ceo@up.stairs&&sec@base.ment`&. Compare the &*address*& (singular)
9716 expansion item, which extracts the working address from a single RFC2822
9717 address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
9718 processing lists.
9719
9720 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
9721 a strict interpretation of header line formatting. Exim parses the bare,
9722 unquoted portion of an email address and if it finds a comma, treats it as an
9723 email address seperator. For the example header line:
9724 .code
9725 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
9726 .endd
9727 The first example below demonstrates that Q-encoded email addresses are parsed
9728 properly if it is given the raw header (in this example, &`$rheader_from:`&).
9729 It does not see the comma because it's still encoded as "=2C". The second
9730 example below is passed the contents of &`$header_from:`&, meaning it gets
9731 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
9732 The third example shows that the presence of a comma is skipped when it is
9733 quoted.
9734 .code
9735 # exim -be '${addresses:From: \
9736 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
9737 user@example.com
9738 # exim -be '${addresses:From: Last, First <user@example.com>}'
9739 Last:user@example.com
9740 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
9741 user@example.com
9742 .endd
9743
9744 .vitem &*${base62:*&<&'digits'&>&*}*&
9745 .cindex "&%base62%& expansion item"
9746 .cindex "expansion" "conversion to base 62"
9747 The string must consist entirely of decimal digits. The number is converted to
9748 base 62 and output as a string of six characters, including leading zeros. In
9749 the few operating environments where Exim uses base 36 instead of base 62 for
9750 its message identifiers (because those systems do not have case-sensitive file
9751 names), base 36 is used by this operator, despite its name. &*Note*&: Just to
9752 be absolutely clear: this is &'not'& base64 encoding.
9753
9754 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
9755 .cindex "&%base62d%& expansion item"
9756 .cindex "expansion" "conversion to base 62"
9757 The string must consist entirely of base-62 digits, or, in operating
9758 environments where Exim uses base 36 instead of base 62 for its message
9759 identifiers, base-36 digits. The number is converted to decimal and output as a
9760 string.
9761
9762
9763 .vitem &*${domain:*&<&'string'&>&*}*&
9764 .cindex "domain" "extraction"
9765 .cindex "expansion" "domain extraction"
9766 The string is interpreted as an RFC 2822 address and the domain is extracted
9767 from it. If the string does not parse successfully, the result is empty.
9768
9769
9770 .vitem &*${escape:*&<&'string'&>&*}*&
9771 .cindex "expansion" "escaping non-printing characters"
9772 .cindex "&%escape%& expansion item"
9773 If the string contains any non-printing characters, they are converted to
9774 escape sequences starting with a backslash. Whether characters with the most
9775 significant bit set (so-called &"8-bit characters"&) count as printing or not
9776 is controlled by the &%print_topbitchars%& option.
9777
9778
9779 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
9780 .cindex "expansion" "expression evaluation"
9781 .cindex "expansion" "arithmetic expression"
9782 .cindex "&%eval%& expansion item"
9783 These items supports simple arithmetic and bitwise logical operations in
9784 expansion strings. The string (after expansion) must be a conventional
9785 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
9786 logical operators, and parentheses. All operations are carried out using
9787 integer arithmetic. The operator priorities are as follows (the same as in the
9788 C programming language):
9789 .table2 70pt 300pt
9790 .irow &'highest:'& "not (~), negate (-)"
9791 .irow "" "multiply (*), divide (/), remainder (%)"
9792 .irow "" "plus (+), minus (-)"
9793 .irow "" "shift-left (<<), shift-right (>>)"
9794 .irow "" "and (&&)"
9795 .irow "" "xor (^)"
9796 .irow &'lowest:'& "or (|)"
9797 .endtable
9798 Binary operators with the same priority are evaluated from left to right. White
9799 space is permitted before or after operators.
9800
9801 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
9802 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
9803 decimal, even if they start with a leading zero; hexadecimal numbers are not
9804 permitted. This can be useful when processing numbers extracted from dates or
9805 times, which often do have leading zeros.
9806
9807 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
9808 or 1024*1024*1024,
9809 respectively. Negative numbers are supported. The result of the computation is
9810 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
9811
9812 .display
9813 &`${eval:1+1} `& yields 2
9814 &`${eval:1+2*3} `& yields 7
9815 &`${eval:(1+2)*3} `& yields 9
9816 &`${eval:2+42%5} `& yields 4
9817 &`${eval:0xc&amp;5} `& yields 4
9818 &`${eval:0xc|5} `& yields 13
9819 &`${eval:0xc^5} `& yields 9
9820 &`${eval:0xc>>1} `& yields 6
9821 &`${eval:0xc<<1} `& yields 24
9822 &`${eval:~255&amp;0x1234} `& yields 4608
9823 &`${eval:-(~255&amp;0x1234)} `& yields -4608
9824 .endd
9825
9826 As a more realistic example, in an ACL you might have
9827 .code
9828 deny message = Too many bad recipients
9829 condition = \
9830 ${if and { \
9831 {>{$rcpt_count}{10}} \
9832 { \
9833 < \
9834 {$recipients_count} \
9835 {${eval:$rcpt_count/2}} \
9836 } \
9837 }{yes}{no}}
9838 .endd
9839 The condition is true if there have been more than 10 RCPT commands and
9840 fewer than half of them have resulted in a valid recipient.
9841
9842
9843 .vitem &*${expand:*&<&'string'&>&*}*&
9844 .cindex "expansion" "re-expansion of substring"
9845 The &%expand%& operator causes a string to be expanded for a second time. For
9846 example,
9847 .code
9848 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
9849 .endd
9850 first looks up a string in a file while expanding the operand for &%expand%&,
9851 and then re-expands what it has found.
9852
9853
9854 .vitem &*${from_utf8:*&<&'string'&>&*}*&
9855 .cindex "Unicode"
9856 .cindex "UTF-8" "conversion from"
9857 .cindex "expansion" "UTF-8 conversion"
9858 .cindex "&%from_utf8%& expansion item"
9859 The world is slowly moving towards Unicode, although there are no standards for
9860 email yet. However, other applications (including some databases) are starting
9861 to store data in Unicode, using UTF-8 encoding. This operator converts from a
9862 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
9863 converted to underscores. The input must be a valid UTF-8 string. If it is not,
9864 the result is an undefined sequence of bytes.
9865
9866 Unicode code points with values less than 256 are compatible with ASCII and
9867 ISO-8859-1 (also known as Latin-1).
9868 For example, character 169 is the copyright symbol in both cases, though the
9869 way it is encoded is different. In UTF-8, more than one byte is needed for
9870 characters with code values greater than 127, whereas ISO-8859-1 is a
9871 single-byte encoding (but thereby limited to 256 characters). This makes
9872 translation from UTF-8 to ISO-8859-1 straightforward.
9873
9874
9875 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
9876 .cindex "hash function" "textual"
9877 .cindex "expansion" "textual hash"
9878 The &%hash%& operator is a simpler interface to the hashing function that can
9879 be used when the two parameters are fixed numbers (as opposed to strings that
9880 change when expanded). The effect is the same as
9881 .code
9882 ${hash{<n>}{<m>}{<string>}}
9883 .endd
9884 See the description of the general &%hash%& item above for details. The
9885 abbreviation &%h%& can be used when &%hash%& is used as an operator.
9886
9887
9888
9889 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
9890 .cindex "base64 encoding" "conversion from hex"
9891 .cindex "expansion" "hex to base64"
9892 .cindex "&%hex2b64%& expansion item"
9893 This operator converts a hex string into one that is base64 encoded. This can
9894 be useful for processing the output of the MD5 and SHA-1 hashing functions.
9895
9896
9897
9898 .vitem &*${hexquote:*&<&'string'&>&*}*&
9899 .cindex "quoting" "hex-encoded unprintable characters"
9900 .cindex "&%hexquote%& expansion item"
9901 This operator converts non-printable characters in a string into a hex
9902 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
9903 as is, and other byte values are converted to &`\xNN`&, for example a
9904 byte value 127 is converted to &`\x7f`&.
9905
9906
9907 .vitem &*${lc:*&<&'string'&>&*}*&
9908 .cindex "case forcing in strings"
9909 .cindex "string" "case forcing"
9910 .cindex "lower casing"
9911 .cindex "expansion" "case forcing"
9912 .cindex "&%lc%& expansion item"
9913 This forces the letters in the string into lower-case, for example:
9914 .code
9915 ${lc:$local_part}
9916 .endd
9917
9918 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
9919 .cindex "expansion" "string truncation"
9920 .cindex "&%length%& expansion item"
9921 The &%length%& operator is a simpler interface to the &%length%& function that
9922 can be used when the parameter is a fixed number (as opposed to a string that
9923 changes when expanded). The effect is the same as
9924 .code
9925 ${length{<number>}{<string>}}
9926 .endd
9927 See the description of the general &%length%& item above for details. Note that
9928 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
9929 when &%length%& is used as an operator.
9930
9931
9932 .vitem &*${listcount:*&<&'string'&>&*}*&
9933 .cindex "expansion" "list item count"
9934 .cindex "list" "item count"
9935 .cindex "list" "count of items"
9936 .cindex "&%listcount%& expansion item"
9937 The string is interpreted as a list and the number of items is returned.
9938
9939
9940 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
9941 .cindex "expansion" "named list"
9942 .cindex "&%listnamed%& expansion item"
9943 The name is interpreted as a named list and the content of the list is returned,
9944 expanding any referenced lists, re-quoting as needed for colon-separation.
9945 If the optional type is given it must be one of "a", "d", "h" or "l"
9946 and selects address-, domain-, host- or localpart- lists to search among respectively.
9947 Otherwise all types are searched in an undefined order and the first
9948 matching list is returned.
9949
9950
9951 .vitem &*${local_part:*&<&'string'&>&*}*&
9952 .cindex "expansion" "local part extraction"
9953 .cindex "&%local_part%& expansion item"
9954 The string is interpreted as an RFC 2822 address and the local part is
9955 extracted from it. If the string does not parse successfully, the result is
9956 empty.
9957
9958
9959 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
9960 .cindex "masked IP address"
9961 .cindex "IP address" "masking"
9962 .cindex "CIDR notation"
9963 .cindex "expansion" "IP address masking"
9964 .cindex "&%mask%& expansion item"
9965 If the form of the string to be operated on is not an IP address followed by a
9966 slash and an integer (that is, a network address in CIDR notation), the
9967 expansion fails. Otherwise, this operator converts the IP address to binary,
9968 masks off the least significant bits according to the bit count, and converts
9969 the result back to text, with mask appended. For example,
9970 .code
9971 ${mask:10.111.131.206/28}
9972 .endd
9973 returns the string &"10.111.131.192/28"&. Since this operation is expected to
9974 be mostly used for looking up masked addresses in files, the result for an IPv6
9975 address uses dots to separate components instead of colons, because colon
9976 terminates a key string in lsearch files. So, for example,
9977 .code
9978 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
9979 .endd
9980 returns the string
9981 .code
9982 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
9983 .endd
9984 Letters in IPv6 addresses are always output in lower case.
9985
9986
9987 .vitem &*${md5:*&<&'string'&>&*}*&
9988 .cindex "MD5 hash"
9989 .cindex "expansion" "MD5 hash"
9990 .cindex "&%md5%& expansion item"
9991 The &%md5%& operator computes the MD5 hash value of the string, and returns it
9992 as a 32-digit hexadecimal number, in which any letters are in lower case.
9993
9994
9995 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
9996 .cindex "expansion" "numeric hash"
9997 .cindex "hash function" "numeric"
9998 The &%nhash%& operator is a simpler interface to the numeric hashing function
9999 that can be used when the two parameters are fixed numbers (as opposed to
10000 strings that change when expanded). The effect is the same as
10001 .code
10002 ${nhash{<n>}{<m>}{<string>}}
10003 .endd
10004 See the description of the general &%nhash%& item above for details.
10005
10006
10007 .vitem &*${quote:*&<&'string'&>&*}*&
10008 .cindex "quoting" "in string expansions"
10009 .cindex "expansion" "quoting"
10010 .cindex "&%quote%& expansion item"
10011 The &%quote%& operator puts its argument into double quotes if it
10012 is an empty string or
10013 contains anything other than letters, digits, underscores, dots, and hyphens.
10014 Any occurrences of double quotes and backslashes are escaped with a backslash.
10015 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
10016 respectively For example,
10017 .code
10018 ${quote:ab"*"cd}
10019 .endd
10020 becomes
10021 .code
10022 "ab\"*\"cd"
10023 .endd
10024 The place where this is useful is when the argument is a substitution from a
10025 variable or a message header.
10026
10027 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
10028 .cindex "&%quote_local_part%& expansion item"
10029 This operator is like &%quote%&, except that it quotes the string only if
10030 required to do so by the rules of RFC 2822 for quoting local parts. For
10031 example, a plus sign would not cause quoting (but it would for &%quote%&).
10032 If you are creating a new email address from the contents of &$local_part$&
10033 (or any other unknown data), you should always use this operator.
10034
10035
10036 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
10037 .cindex "quoting" "lookup-specific"
10038 This operator applies lookup-specific quoting rules to the string. Each
10039 query-style lookup type has its own quoting rules which are described with
10040 the lookups in chapter &<<CHAPfdlookup>>&. For example,
10041 .code
10042 ${quote_ldap:two * two}
10043 .endd
10044 returns
10045 .code
10046 two%20%5C2A%20two
10047 .endd
10048 For single-key lookup types, no quoting is ever necessary and this operator
10049 yields an unchanged string.
10050
10051
10052 .vitem &*${randint:*&<&'n'&>&*}*&
10053 .cindex "random number"
10054 This operator returns a somewhat random number which is less than the
10055 supplied number and is at least 0. The quality of this randomness depends
10056 on how Exim was built; the values are not suitable for keying material.
10057 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
10058 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
10059 for versions of GnuTLS with that function.
10060 Otherwise, the implementation may be arc4random(), random() seeded by
10061 srandomdev() or srandom(), or a custom implementation even weaker than
10062 random().
10063
10064
10065 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
10066 .cindex "expansion" "IP address"
10067 This operator reverses an IP address; for IPv4 addresses, the result is in
10068 dotted-quad decimal form, while for IPv6 addreses the result is in
10069 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
10070 for DNS. For example,
10071 .code
10072 ${reverse_ip:192.0.2.4}
10073 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
10074 .endd
10075 returns
10076 .code
10077 4.2.0.192
10078 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
10079 .endd
10080
10081
10082 .vitem &*${rfc2047:*&<&'string'&>&*}*&
10083 .cindex "expansion" "RFC 2047"
10084 .cindex "RFC 2047" "expansion operator"
10085 .cindex "&%rfc2047%& expansion item"
10086 This operator encodes text according to the rules of RFC 2047. This is an
10087 encoding that is used in header lines to encode non-ASCII characters. It is
10088 assumed that the input string is in the encoding specified by the
10089 &%headers_charset%& option, which defaults to ISO-8859-1. If the string
10090 contains only characters in the range 33&--126, and no instances of the
10091 characters
10092 .code
10093 ? = ( ) < > @ , ; : \ " . [ ] _
10094 .endd
10095 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
10096 string, using as many &"encoded words"& as necessary to encode all the
10097 characters.
10098
10099
10100 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
10101 .cindex "expansion" "RFC 2047"
10102 .cindex "RFC 2047" "decoding"
10103 .cindex "&%rfc2047d%& expansion item"
10104 This operator decodes strings that are encoded as per RFC 2047. Binary zero
10105 bytes are replaced by question marks. Characters are converted into the
10106 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
10107 not recognized unless &%check_rfc2047_length%& is set false.
10108
10109 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
10110 access a header line, RFC 2047 decoding is done automatically. You do not need
10111 to use this operator as well.
10112
10113
10114
10115 .vitem &*${rxquote:*&<&'string'&>&*}*&
10116 .cindex "quoting" "in regular expressions"
10117 .cindex "regular expressions" "quoting"
10118 .cindex "&%rxquote%& expansion item"
10119 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
10120 characters in its argument. This is useful when substituting the values of
10121 variables or headers inside regular expressions.
10122
10123
10124 .vitem &*${sha1:*&<&'string'&>&*}*&
10125 .cindex "SHA-1 hash"
10126 .cindex "expansion" "SHA-1 hashing"
10127 .cindex "&%sha2%& expansion item"
10128 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
10129 it as a 40-digit hexadecimal number, in which any letters are in upper case.
10130
10131
10132 .vitem &*${stat:*&<&'string'&>&*}*&
10133 .cindex "expansion" "statting a file"
10134 .cindex "file" "extracting characteristics"
10135 .cindex "&%stat%& expansion item"
10136 The string, after expansion, must be a file path. A call to the &[stat()]&
10137 function is made for this path. If &[stat()]& fails, an error occurs and the
10138 expansion fails. If it succeeds, the data from the stat replaces the item, as a
10139 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
10140 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
10141 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
10142 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
10143 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
10144 can extract individual fields using the &%extract%& expansion item.
10145
10146 The use of the &%stat%& expansion in users' filter files can be locked out by
10147 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
10148 systems for files larger than 2GB.
10149
10150 .vitem &*${str2b64:*&<&'string'&>&*}*&
10151 .cindex "expansion" "base64 encoding"
10152 .cindex "base64 encoding" "in string expansion"
10153 .cindex "&%str2b64%& expansion item"
10154 This operator converts a string into one that is base64 encoded.
10155
10156
10157
10158 .vitem &*${strlen:*&<&'string'&>&*}*&
10159 .cindex "expansion" "string length"
10160 .cindex "string" "length in expansion"
10161 .cindex "&%strlen%& expansion item"
10162 The item is replace by the length of the expanded string, expressed as a
10163 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
10164
10165
10166 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
10167 .cindex "&%substr%& expansion item"
10168 .cindex "substring extraction"
10169 .cindex "expansion" "substring expansion"
10170 The &%substr%& operator is a simpler interface to the &%substr%& function that
10171 can be used when the two parameters are fixed numbers (as opposed to strings
10172 that change when expanded). The effect is the same as
10173 .code
10174 ${substr{<start>}{<length>}{<string>}}
10175 .endd
10176 See the description of the general &%substr%& item above for details. The
10177 abbreviation &%s%& can be used when &%substr%& is used as an operator.
10178
10179 .vitem &*${time_eval:*&<&'string'&>&*}*&
10180 .cindex "&%time_eval%& expansion item"
10181 .cindex "time interval" "decoding"
10182 This item converts an Exim time interval such as &`2d4h5m`& into a number of
10183 seconds.
10184
10185 .vitem &*${time_interval:*&<&'string'&>&*}*&
10186 .cindex "&%time_interval%& expansion item"
10187 .cindex "time interval" "formatting"
10188 The argument (after sub-expansion) must be a sequence of decimal digits that
10189 represents an interval of time as a number of seconds. It is converted into a
10190 number of larger units and output in Exim's normal time format, for example,
10191 &`1w3d4h2m6s`&.
10192
10193 .vitem &*${uc:*&<&'string'&>&*}*&
10194 .cindex "case forcing in strings"
10195 .cindex "string" "case forcing"
10196 .cindex "upper casing"
10197 .cindex "expansion" "case forcing"
10198 .cindex "&%uc%& expansion item"
10199 This forces the letters in the string into upper-case.
10200
10201 .vitem &*${utf8clean:*&<&'string'&>&*}*&
10202 .cindex "correction of invalid utf-8 sequences in strings"
10203 .cindex "utf-8" "utf-8 sequences"
10204 .cindex "incorrect utf-8"
10205 .cindex "expansion" "utf-8 forcing"
10206 .cindex "&%utf8clean%& expansion item"
10207 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
10208 .endlist
10209
10210
10211
10212
10213
10214
10215 .section "Expansion conditions" "SECTexpcond"
10216 .scindex IIDexpcond "expansion" "conditions"
10217 The following conditions are available for testing by the &%${if%& construct
10218 while expanding strings:
10219
10220 .vlist
10221 .vitem &*!*&<&'condition'&>
10222 .cindex "expansion" "negating a condition"
10223 .cindex "negation" "in expansion condition"
10224 Preceding any condition with an exclamation mark negates the result of the
10225 condition.
10226
10227 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10228 .cindex "numeric comparison"
10229 .cindex "expansion" "numeric comparison"
10230 There are a number of symbolic operators for doing numeric comparisons. They
10231 are:
10232 .display
10233 &`= `& equal
10234 &`== `& equal
10235 &`> `& greater
10236 &`>= `& greater or equal
10237 &`< `& less
10238 &`<= `& less or equal
10239 .endd
10240 For example:
10241 .code
10242 ${if >{$message_size}{10M} ...
10243 .endd
10244 Note that the general negation operator provides for inequality testing. The
10245 two strings must take the form of optionally signed decimal integers,
10246 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
10247 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
10248 As a special case, the numerical value of an empty string is taken as
10249 zero.
10250
10251 In all cases, a relative comparator OP is testing if <&'string1'&> OP
10252 <&'string2'&>; the above example is checking if &$message_size$& is larger than
10253 10M, not if 10M is larger than &$message_size$&.
10254
10255
10256 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
10257 {*&<&'arg2'&>&*}...}*&
10258 .cindex "expansion" "calling an acl"
10259 .cindex "&%acl%&" "expansion condition"
10260 The name and zero to nine argument strings are first expanded separately. The expanded
10261 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
10262 Any unused are made empty. The variable &$acl_narg$& is set to the number of
10263 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
10264 and may use the variables; if another acl expansion is used the values
10265 are restored after it returns. If the ACL sets
10266 a value using a "message =" modifier the variable $value becomes
10267 the result of the expansion, otherwise it is empty.
10268 If the ACL returns accept the condition is true; if deny, false.
10269 If the ACL returns defer the result is a forced-fail.
10270
10271 .vitem &*bool&~{*&<&'string'&>&*}*&
10272 .cindex "expansion" "boolean parsing"
10273 .cindex "&%bool%& expansion condition"
10274 This condition turns a string holding a true or false representation into
10275 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
10276 (case-insensitively); also integer numbers map to true if non-zero,
10277 false if zero.
10278 An empty string is treated as false.
10279 Leading and trailing whitespace is ignored;
10280 thus a string consisting only of whitespace is false.
10281 All other string values will result in expansion failure.
10282
10283 When combined with ACL variables, this expansion condition will let you
10284 make decisions in one place and act on those decisions in another place.
10285 For example:
10286 .code
10287 ${if bool{$acl_m_privileged_sender} ...
10288 .endd
10289
10290
10291 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
10292 .cindex "expansion" "boolean parsing"
10293 .cindex "&%bool_lax%& expansion condition"
10294 Like &%bool%&, this condition turns a string into a boolean state. But
10295 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
10296 loose definition that the Router &%condition%& option uses. The empty string
10297 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
10298 true. Leading and trailing whitespace is ignored.
10299
10300 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
10301
10302 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10303 .cindex "expansion" "encrypted comparison"
10304 .cindex "encrypted strings, comparing"
10305 .cindex "&%crypteq%& expansion condition"
10306 This condition is included in the Exim binary if it is built to support any
10307 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
10308 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
10309 included in the binary.
10310
10311 The &%crypteq%& condition has two arguments. The first is encrypted and
10312 compared against the second, which is already encrypted. The second string may
10313 be in the LDAP form for storing encrypted strings, which starts with the
10314 encryption type in curly brackets, followed by the data. If the second string
10315 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
10316 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
10317 Typically this will be a field from a password file. An example of an encrypted
10318 string in LDAP form is:
10319 .code
10320 {md5}CY9rzUYh03PK3k6DJie09g==
10321 .endd
10322 If such a string appears directly in an expansion, the curly brackets have to
10323 be quoted, because they are part of the expansion syntax. For example:
10324 .code
10325 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
10326 .endd
10327 The following encryption types (whose names are matched case-independently) are
10328 supported:
10329
10330 .ilist
10331 .cindex "MD5 hash"
10332 .cindex "base64 encoding" "in encrypted password"
10333 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
10334 printable characters to compare with the remainder of the second string. If the
10335 length of the comparison string is 24, Exim assumes that it is base64 encoded
10336 (as in the above example). If the length is 32, Exim assumes that it is a
10337 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
10338 comparison fails.
10339
10340 .next
10341 .cindex "SHA-1 hash"
10342 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
10343 printable characters to compare with the remainder of the second string. If the
10344 length of the comparison string is 28, Exim assumes that it is base64 encoded.
10345 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
10346 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
10347
10348 .next
10349 .cindex "&[crypt()]&"
10350 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
10351 only the first eight characters of the password. However, in modern operating
10352 systems this is no longer true, and in many cases the entire password is used,
10353 whatever its length.
10354
10355 .next
10356 .cindex "&[crypt16()]&"
10357 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
10358 use up to 16 characters of the password in some operating systems. Again, in
10359 modern operating systems, more characters may be used.
10360 .endlist
10361 Exim has its own version of &[crypt16()]&, which is just a double call to
10362 &[crypt()]&. For operating systems that have their own version, setting
10363 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
10364 operating system version instead of its own. This option is set by default in
10365 the OS-dependent &_Makefile_& for those operating systems that are known to
10366 support &[crypt16()]&.
10367
10368 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
10369 it was not using the same algorithm as some operating systems' versions. It
10370 turns out that as well as &[crypt16()]& there is a function called
10371 &[bigcrypt()]& in some operating systems. This may or may not use the same
10372 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
10373
10374 However, since there is now a move away from the traditional &[crypt()]&
10375 functions towards using SHA1 and other algorithms, tidying up this area of
10376 Exim is seen as very low priority.
10377
10378 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
10379 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
10380 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
10381 default is &`{crypt}`&. Whatever the default, you can always use either
10382 function by specifying it explicitly in curly brackets.
10383
10384 .vitem &*def:*&<&'variable&~name'&>
10385 .cindex "expansion" "checking for empty variable"
10386 .cindex "&%def%& expansion condition"
10387 The &%def%& condition must be followed by the name of one of the expansion
10388 variables defined in section &<<SECTexpvar>>&. The condition is true if the
10389 variable does not contain the empty string. For example:
10390 .code
10391 ${if def:sender_ident {from $sender_ident}}
10392 .endd
10393 Note that the variable name is given without a leading &%$%& character. If the
10394 variable does not exist, the expansion fails.
10395
10396 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
10397 &~&*def:h_*&<&'header&~name'&>&*:*&"
10398 .cindex "expansion" "checking header line existence"
10399 This condition is true if a message is being processed and the named header
10400 exists in the message. For example,
10401 .code
10402 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
10403 .endd
10404 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
10405 the header name must be terminated by a colon if white space does not follow.
10406
10407 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10408 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10409 .cindex "string" "comparison"
10410 .cindex "expansion" "string comparison"
10411 .cindex "&%eq%& expansion condition"
10412 .cindex "&%eqi%& expansion condition"
10413 The two substrings are first expanded. The condition is true if the two
10414 resulting strings are identical. For &%eq%& the comparison includes the case of
10415 letters, whereas for &%eqi%& the comparison is case-independent.
10416
10417 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
10418 .cindex "expansion" "file existence test"
10419 .cindex "file" "existence test"
10420 .cindex "&%exists%&, expansion condition"
10421 The substring is first expanded and then interpreted as an absolute path. The
10422 condition is true if the named file (or directory) exists. The existence test
10423 is done by calling the &[stat()]& function. The use of the &%exists%& test in
10424 users' filter files may be locked out by the system administrator.
10425
10426 .vitem &*first_delivery*&
10427 .cindex "delivery" "first"
10428 .cindex "first delivery"
10429 .cindex "expansion" "first delivery test"
10430 .cindex "&%first_delivery%& expansion condition"
10431 This condition, which has no data, is true during a message's first delivery
10432 attempt. It is false during any subsequent delivery attempts.
10433
10434
10435 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
10436 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
10437 .cindex "list" "iterative conditions"
10438 .cindex "expansion" "&*forall*& condition"
10439 .cindex "expansion" "&*forany*& condition"
10440 .vindex "&$item$&"
10441 These conditions iterate over a list. The first argument is expanded to form
10442 the list. By default, the list separator is a colon, but it can be changed by
10443 the normal method. The second argument is interpreted as a condition that is to
10444 be applied to each item in the list in turn. During the interpretation of the
10445 condition, the current list item is placed in a variable called &$item$&.
10446 .ilist
10447 For &*forany*&, interpretation stops if the condition is true for any item, and
10448 the result of the whole condition is true. If the condition is false for all
10449 items in the list, the overall condition is false.
10450 .next
10451 For &*forall*&, interpretation stops if the condition is false for any item,
10452 and the result of the whole condition is false. If the condition is true for
10453 all items in the list, the overall condition is true.
10454 .endlist
10455 Note that negation of &*forany*& means that the condition must be false for all
10456 items for the overall condition to succeed, and negation of &*forall*& means
10457 that the condition must be false for at least one item. In this example, the
10458 list separator is changed to a comma:
10459 .code
10460 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
10461 .endd
10462 The value of &$item$& is saved and restored while &*forany*& or &*forall*& is
10463 being processed, to enable these expansion items to be nested.
10464
10465 To scan a named list, expand it with the &*listnamed*& operator.
10466
10467
10468 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10469 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10470 .cindex "string" "comparison"
10471 .cindex "expansion" "string comparison"
10472 .cindex "&%ge%& expansion condition"
10473 .cindex "&%gei%& expansion condition"
10474 The two substrings are first expanded. The condition is true if the first
10475 string is lexically greater than or equal to the second string. For &%ge%& the
10476 comparison includes the case of letters, whereas for &%gei%& the comparison is
10477 case-independent.
10478
10479 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10480 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10481 .cindex "string" "comparison"
10482 .cindex "expansion" "string comparison"
10483 .cindex "&%gt%& expansion condition"
10484 .cindex "&%gti%& expansion condition"
10485 The two substrings are first expanded. The condition is true if the first
10486 string is lexically greater than the second string. For &%gt%& the comparison
10487 includes the case of letters, whereas for &%gti%& the comparison is
10488 case-independent.
10489
10490 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10491 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10492 .cindex "string" "comparison"
10493 .cindex "list" "iterative conditions"
10494 Both strings are expanded; the second string is treated as a list of simple
10495 strings; if the first string is a member of the second, then the condition
10496 is true.
10497
10498 These are simpler to use versions of the more powerful &*forany*& condition.
10499 Examples, and the &*forany*& equivalents:
10500 .code
10501 ${if inlist{needle}{foo:needle:bar}}
10502 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
10503 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
10504 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
10505 .endd
10506
10507 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
10508 &*isip4&~{*&<&'string'&>&*}*& &&&
10509 &*isip6&~{*&<&'string'&>&*}*&
10510 .cindex "IP address" "testing string format"
10511 .cindex "string" "testing for IP address"
10512 .cindex "&%isip%& expansion condition"
10513 .cindex "&%isip4%& expansion condition"
10514 .cindex "&%isip6%& expansion condition"
10515 The substring is first expanded, and then tested to see if it has the form of
10516 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
10517 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
10518
10519 For an IPv4 address, the test is for four dot-separated components, each of
10520 which consists of from one to three digits. For an IPv6 address, up to eight
10521 colon-separated components are permitted, each containing from one to four
10522 hexadecimal digits. There may be fewer than eight components if an empty
10523 component (adjacent colons) is present. Only one empty component is permitted.
10524
10525 &*Note*&: The checks are just on the form of the address; actual numerical
10526 values are not considered. Thus, for example, 999.999.999.999 passes the IPv4
10527 check. The main use of these tests is to distinguish between IP addresses and
10528 host names, or between IPv4 and IPv6 addresses. For example, you could use
10529 .code
10530 ${if isip4{$sender_host_address}...
10531 .endd
10532 to test which IP version an incoming SMTP connection is using.
10533
10534 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
10535 .cindex "LDAP" "use for authentication"
10536 .cindex "expansion" "LDAP authentication test"
10537 .cindex "&%ldapauth%& expansion condition"
10538 This condition supports user authentication using LDAP. See section
10539 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
10540 queries. For this use, the query must contain a user name and password. The
10541 query itself is not used, and can be empty. The condition is true if the
10542 password is not empty, and the user name and password are accepted by the LDAP
10543 server. An empty password is rejected without calling LDAP because LDAP binds
10544 with an empty password are considered anonymous regardless of the username, and
10545 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
10546 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
10547 this can be used.
10548
10549
10550 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10551 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10552 .cindex "string" "comparison"
10553 .cindex "expansion" "string comparison"
10554 .cindex "&%le%& expansion condition"
10555 .cindex "&%lei%& expansion condition"
10556 The two substrings are first expanded. The condition is true if the first
10557 string is lexically less than or equal to the second string. For &%le%& the
10558 comparison includes the case of letters, whereas for &%lei%& the comparison is
10559 case-independent.
10560
10561 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10562 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10563 .cindex "string" "comparison"
10564 .cindex "expansion" "string comparison"
10565 .cindex "&%lt%& expansion condition"
10566 .cindex "&%lti%& expansion condition"
10567 The two substrings are first expanded. The condition is true if the first
10568 string is lexically less than the second string. For &%lt%& the comparison
10569 includes the case of letters, whereas for &%lti%& the comparison is
10570 case-independent.
10571
10572
10573 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10574 .cindex "expansion" "regular expression comparison"
10575 .cindex "regular expressions" "match in expanded string"
10576 .cindex "&%match%& expansion condition"
10577 The two substrings are first expanded. The second is then treated as a regular
10578 expression and applied to the first. Because of the pre-expansion, if the
10579 regular expression contains dollar, or backslash characters, they must be
10580 escaped. Care must also be taken if the regular expression contains braces
10581 (curly brackets). A closing brace must be escaped so that it is not taken as a
10582 premature termination of <&'string2'&>. The easiest approach is to use the
10583 &`\N`& feature to disable expansion of the regular expression.
10584 For example,
10585 .code
10586 ${if match {$local_part}{\N^\d{3}\N} ...
10587 .endd
10588 If the whole expansion string is in double quotes, further escaping of
10589 backslashes is also required.
10590
10591 The condition is true if the regular expression match succeeds.
10592 The regular expression is not required to begin with a circumflex
10593 metacharacter, but if there is no circumflex, the expression is not anchored,
10594 and it may match anywhere in the subject, not just at the start. If you want
10595 the pattern to match at the end of the subject, you must include the &`$`&
10596 metacharacter at an appropriate point.
10597
10598 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
10599 At the start of an &%if%& expansion the values of the numeric variable
10600 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
10601 succeeds causes them to be reset to the substrings of that condition and they
10602 will have these values during the expansion of the success string. At the end
10603 of the &%if%& expansion, the previous values are restored. After testing a
10604 combination of conditions using &%or%&, the subsequent values of the numeric
10605 variables are those of the condition that succeeded.
10606
10607 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10608 .cindex "&%match_address%& expansion condition"
10609 See &*match_local_part*&.
10610
10611 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10612 .cindex "&%match_domain%& expansion condition"
10613 See &*match_local_part*&.
10614
10615 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10616 .cindex "&%match_ip%& expansion condition"
10617 This condition matches an IP address to a list of IP address patterns. It must
10618 be followed by two argument strings. The first (after expansion) must be an IP
10619 address or an empty string. The second (not expanded) is a restricted host
10620 list that can match only an IP address, not a host name. For example:
10621 .code
10622 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
10623 .endd
10624 The specific types of host list item that are permitted in the list are:
10625
10626 .ilist
10627 An IP address, optionally with a CIDR mask.
10628 .next
10629 A single asterisk, which matches any IP address.
10630 .next
10631 An empty item, which matches only if the IP address is empty. This could be
10632 useful for testing for a locally submitted message or one from specific hosts
10633 in a single test such as
10634 . ==== As this is a nested list, any displays it contains must be indented
10635 . ==== as otherwise they are too far to the left. This comment applies to
10636 . ==== the use of xmlto plus fop. There's no problem when formatting with
10637 . ==== sdop, with or without the extra indent.
10638 .code
10639 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
10640 .endd
10641 where the first item in the list is the empty string.
10642 .next
10643 The item @[] matches any of the local host's interface addresses.
10644 .next
10645 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
10646 even if &`net-`& is not specified. There is never any attempt to turn the IP
10647 address into a host name. The most common type of linear search for
10648 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
10649 masks. For example:
10650 .code
10651 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
10652 .endd
10653 It is of course possible to use other kinds of lookup, and in such a case, you
10654 do need to specify the &`net-`& prefix if you want to specify a specific
10655 address mask, for example:
10656 .code
10657 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
10658 .endd
10659 However, unless you are combining a &%match_ip%& condition with others, it is
10660 just as easy to use the fact that a lookup is itself a condition, and write:
10661 .code
10662 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
10663 .endd
10664 .endlist ilist
10665
10666 Note that <&'string2'&> is not itself subject to string expansion, unless
10667 Exim was built with the EXPAND_LISTMATCH_RHS option.
10668
10669 Consult section &<<SECThoslispatip>>& for further details of these patterns.
10670
10671 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10672 .cindex "domain list" "in expansion condition"
10673 .cindex "address list" "in expansion condition"
10674 .cindex "local part" "list, in expansion condition"
10675 .cindex "&%match_local_part%& expansion condition"
10676 This condition, together with &%match_address%& and &%match_domain%&, make it
10677 possible to test domain, address, and local part lists within expansions. Each
10678 condition requires two arguments: an item and a list to match. A trivial
10679 example is:
10680 .code
10681 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
10682 .endd
10683 In each case, the second argument may contain any of the allowable items for a
10684 list of the appropriate type. Also, because the second argument (after
10685 expansion) is a standard form of list, it is possible to refer to a named list.
10686 Thus, you can use conditions like this:
10687 .code
10688 ${if match_domain{$domain}{+local_domains}{...
10689 .endd
10690 .cindex "&`+caseful`&"
10691 For address lists, the matching starts off caselessly, but the &`+caseful`&
10692 item can be used, as in all address lists, to cause subsequent items to
10693 have their local parts matched casefully. Domains are always matched
10694 caselessly.
10695
10696 Note that <&'string2'&> is not itself subject to string expansion, unless
10697 Exim was built with the EXPAND_LISTMATCH_RHS option.
10698
10699 &*Note*&: Host lists are &'not'& supported in this way. This is because
10700 hosts have two identities: a name and an IP address, and it is not clear
10701 how to specify cleanly how such a test would work. However, IP addresses can be
10702 matched using &%match_ip%&.
10703
10704 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
10705 .cindex "PAM authentication"
10706 .cindex "AUTH" "with PAM"
10707 .cindex "Solaris" "PAM support"
10708 .cindex "expansion" "PAM authentication test"
10709 .cindex "&%pam%& expansion condition"
10710 &'Pluggable Authentication Modules'&
10711 (&url(http://www.kernel.org/pub/linux/libs/pam/)) are a facility that is
10712 available in the latest releases of Solaris and in some GNU/Linux
10713 distributions. The Exim support, which is intended for use in conjunction with
10714 the SMTP AUTH command, is available only if Exim is compiled with
10715 .code
10716 SUPPORT_PAM=yes
10717 .endd
10718 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
10719 in some releases of GNU/Linux &%-ldl%& is also needed.
10720
10721 The argument string is first expanded, and the result must be a
10722 colon-separated list of strings. Leading and trailing white space is ignored.
10723 The PAM module is initialized with the service name &"exim"& and the user name
10724 taken from the first item in the colon-separated data string (<&'string1'&>).
10725 The remaining items in the data string are passed over in response to requests
10726 from the authentication function. In the simple case there will only be one
10727 request, for a password, so the data consists of just two strings.
10728
10729 There can be problems if any of the strings are permitted to contain colon
10730 characters. In the usual way, these have to be doubled to avoid being taken as
10731 separators. If the data is being inserted from a variable, the &%sg%& expansion
10732 item can be used to double any existing colons. For example, the configuration
10733 of a LOGIN authenticator might contain this setting:
10734 .code
10735 server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
10736 .endd
10737 For a PLAIN authenticator you could use:
10738 .code
10739 server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
10740 .endd
10741 In some operating systems, PAM authentication can be done only from a process
10742 running as root. Since Exim is running as the Exim user when receiving
10743 messages, this means that PAM cannot be used directly in those systems.
10744 A patched version of the &'pam_unix'& module that comes with the
10745 Linux PAM package is available from &url(http://www.e-admin.de/pam_exim/).
10746 The patched module allows one special uid/gid combination, in addition to root,
10747 to authenticate. If you build the patched module to allow the Exim user and
10748 group, PAM can then be used from an Exim authenticator.
10749
10750
10751 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
10752 .cindex "&'pwcheck'& daemon"
10753 .cindex "Cyrus"
10754 .cindex "expansion" "&'pwcheck'& authentication test"
10755 .cindex "&%pwcheck%& expansion condition"
10756 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
10757 This is one way of making it possible for passwords to be checked by a process
10758 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
10759 deprecated. Its replacement is &'saslauthd'& (see below).
10760
10761 The pwcheck support is not included in Exim by default. You need to specify
10762 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
10763 building Exim. For example:
10764 .code
10765 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
10766 .endd
10767 You do not need to install the full Cyrus software suite in order to use
10768 the pwcheck daemon. You can compile and install just the daemon alone
10769 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
10770 access to the &_/var/pwcheck_& directory.
10771
10772 The &%pwcheck%& condition takes one argument, which must be the user name and
10773 password, separated by a colon. For example, in a LOGIN authenticator
10774 configuration, you might have this:
10775 .code
10776 server_condition = ${if pwcheck{$auth1:$auth2}}
10777 .endd
10778 Again, for a PLAIN authenticator configuration, this would be:
10779 .code
10780 server_condition = ${if pwcheck{$auth2:$auth3}}
10781 .endd
10782 .vitem &*queue_running*&
10783 .cindex "queue runner" "detecting when delivering from"
10784 .cindex "expansion" "queue runner test"
10785 .cindex "&%queue_running%& expansion condition"
10786 This condition, which has no data, is true during delivery attempts that are
10787 initiated by queue runner processes, and false otherwise.
10788
10789
10790 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
10791 .cindex "Radius"
10792 .cindex "expansion" "Radius authentication"
10793 .cindex "&%radius%& expansion condition"
10794 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
10795 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
10796 the Radius client configuration file in order to build Exim with Radius
10797 support.
10798
10799 With just that one setting, Exim expects to be linked with the &%radiusclient%&
10800 library, using the original API. If you are using release 0.4.0 or later of
10801 this library, you need to set
10802 .code
10803 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
10804 .endd
10805 in &_Local/Makefile_& when building Exim. You can also link Exim with the
10806 &%libradius%& library that comes with FreeBSD. To do this, set
10807 .code
10808 RADIUS_LIB_TYPE=RADLIB
10809 .endd
10810 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
10811 You may also have to supply a suitable setting in EXTRALIBS so that the
10812 Radius library can be found when Exim is linked.
10813
10814 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
10815 Radius client library, which calls the Radius server. The condition is true if
10816 the authentication is successful. For example:
10817 .code
10818 server_condition = ${if radius{<arguments>}}
10819 .endd
10820
10821
10822 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
10823 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
10824 .cindex "&'saslauthd'& daemon"
10825 .cindex "Cyrus"
10826 .cindex "expansion" "&'saslauthd'& authentication test"
10827 .cindex "&%saslauthd%& expansion condition"
10828 This condition supports user authentication using the Cyrus &'saslauthd'&
10829 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
10830 Using this daemon is one way of making it possible for passwords to be checked
10831 by a process that is not running as root.
10832
10833 The saslauthd support is not included in Exim by default. You need to specify
10834 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
10835 building Exim. For example:
10836 .code
10837 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
10838 .endd
10839 You do not need to install the full Cyrus software suite in order to use
10840 the saslauthd daemon. You can compile and install just the daemon alone
10841 from the Cyrus SASL library.
10842
10843 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
10844 two are mandatory. For example:
10845 .code
10846 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
10847 .endd
10848 The service and the realm are optional (which is why the arguments are enclosed
10849 in their own set of braces). For details of the meaning of the service and
10850 realm, and how to run the daemon, consult the Cyrus documentation.
10851 .endlist vlist
10852
10853
10854
10855 .section "Combining expansion conditions" "SECID84"
10856 .cindex "expansion" "combining conditions"
10857 Several conditions can be tested at once by combining them using the &%and%&
10858 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
10859 conditions on their own, and precede their lists of sub-conditions. Each
10860 sub-condition must be enclosed in braces within the overall braces that contain
10861 the list. No repetition of &%if%& is used.
10862
10863
10864 .vlist
10865 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
10866 .cindex "&""or""& expansion condition"
10867 .cindex "expansion" "&""or""& of conditions"
10868 The sub-conditions are evaluated from left to right. The condition is true if
10869 any one of the sub-conditions is true.
10870 For example,
10871 .code
10872 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
10873 .endd
10874 When a true sub-condition is found, the following ones are parsed but not
10875 evaluated. If there are several &"match"& sub-conditions the values of the
10876 numeric variables afterwards are taken from the first one that succeeds.
10877
10878 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
10879 .cindex "&""and""& expansion condition"
10880 .cindex "expansion" "&""and""& of conditions"
10881 The sub-conditions are evaluated from left to right. The condition is true if
10882 all of the sub-conditions are true. If there are several &"match"&
10883 sub-conditions, the values of the numeric variables afterwards are taken from
10884 the last one. When a false sub-condition is found, the following ones are
10885 parsed but not evaluated.
10886 .endlist
10887 .ecindex IIDexpcond
10888
10889
10890
10891
10892 .section "Expansion variables" "SECTexpvar"
10893 .cindex "expansion" "variables, list of"
10894 This section contains an alphabetical list of all the expansion variables. Some
10895 of them are available only when Exim is compiled with specific options such as
10896 support for TLS or the content scanning extension.
10897
10898 .vlist
10899 .vitem "&$0$&, &$1$&, etc"
10900 .cindex "numerical variables (&$1$& &$2$& etc)"
10901 When a &%match%& expansion condition succeeds, these variables contain the
10902 captured substrings identified by the regular expression during subsequent
10903 processing of the success string of the containing &%if%& expansion item.
10904 However, they do not retain their values afterwards; in fact, their previous
10905 values are restored at the end of processing an &%if%& item. The numerical
10906 variables may also be set externally by some other matching process which
10907 precedes the expansion of the string. For example, the commands available in
10908 Exim filter files include an &%if%& command with its own regular expression
10909 matching condition.
10910
10911 .vitem "&$acl_c...$&"
10912 Values can be placed in these variables by the &%set%& modifier in an ACL. They
10913 can be given any name that starts with &$acl_c$& and is at least six characters
10914 long, but the sixth character must be either a digit or an underscore. For
10915 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
10916 variables persist throughout the lifetime of an SMTP connection. They can be
10917 used to pass information between ACLs and between different invocations of the
10918 same ACL. When a message is received, the values of these variables are saved
10919 with the message, and can be accessed by filters, routers, and transports
10920 during subsequent delivery.
10921
10922 .vitem "&$acl_m...$&"
10923 These variables are like the &$acl_c...$& variables, except that their values
10924 are reset after a message has been received. Thus, if several messages are
10925 received in one SMTP connection, &$acl_m...$& values are not passed on from one
10926 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
10927 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
10928 message is received, the values of these variables are saved with the message,
10929 and can be accessed by filters, routers, and transports during subsequent
10930 delivery.
10931
10932 .vitem &$acl_verify_message$&
10933 .vindex "&$acl_verify_message$&"
10934 After an address verification has failed, this variable contains the failure
10935 message. It retains its value for use in subsequent modifiers. The message can
10936 be preserved by coding like this:
10937 .code
10938 warn !verify = sender
10939 set acl_m0 = $acl_verify_message
10940 .endd
10941 You can use &$acl_verify_message$& during the expansion of the &%message%& or
10942 &%log_message%& modifiers, to include information about the verification
10943 failure.
10944
10945 .vitem &$address_data$&
10946 .vindex "&$address_data$&"
10947 This variable is set by means of the &%address_data%& option in routers. The
10948 value then remains with the address while it is processed by subsequent routers
10949 and eventually a transport. If the transport is handling multiple addresses,
10950 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
10951 for more details. &*Note*&: The contents of &$address_data$& are visible in
10952 user filter files.
10953
10954 If &$address_data$& is set when the routers are called from an ACL to verify
10955 a recipient address, the final value is still in the variable for subsequent
10956 conditions and modifiers of the ACL statement. If routing the address caused it
10957 to be redirected to just one address, the child address is also routed as part
10958 of the verification, and in this case the final value of &$address_data$& is
10959 from the child's routing.
10960
10961 If &$address_data$& is set when the routers are called from an ACL to verify a
10962 sender address, the final value is also preserved, but this time in
10963 &$sender_address_data$&, to distinguish it from data from a recipient
10964 address.
10965
10966 In both cases (recipient and sender verification), the value does not persist
10967 after the end of the current ACL statement. If you want to preserve
10968 these values for longer, you can save them in ACL variables.
10969
10970 .vitem &$address_file$&
10971 .vindex "&$address_file$&"
10972 When, as a result of aliasing, forwarding, or filtering, a message is directed
10973 to a specific file, this variable holds the name of the file when the transport
10974 is running. At other times, the variable is empty. For example, using the
10975 default configuration, if user &%r2d2%& has a &_.forward_& file containing
10976 .code
10977 /home/r2d2/savemail
10978 .endd
10979 then when the &(address_file)& transport is running, &$address_file$&
10980 contains the text string &`/home/r2d2/savemail`&.
10981 .cindex "Sieve filter" "value of &$address_file$&"
10982 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
10983 then up to the transport configuration to generate an appropriate absolute path
10984 to the relevant file.
10985
10986 .vitem &$address_pipe$&
10987 .vindex "&$address_pipe$&"
10988 When, as a result of aliasing or forwarding, a message is directed to a pipe,
10989 this variable holds the pipe command when the transport is running.
10990
10991 .vitem "&$auth1$& &-- &$auth3$&"
10992 .vindex "&$auth1$&, &$auth2$&, etc"
10993 These variables are used in SMTP authenticators (see chapters
10994 &<<CHAPplaintext>>&&--&<<CHAPspa>>&). Elsewhere, they are empty.
10995
10996 .vitem &$authenticated_id$&
10997 .cindex "authentication" "id"
10998 .vindex "&$authenticated_id$&"
10999 When a server successfully authenticates a client it may be configured to
11000 preserve some of the authentication information in the variable
11001 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
11002 user/password authenticator configuration might preserve the user name for use
11003 in the routers. Note that this is not the same information that is saved in
11004 &$sender_host_authenticated$&.
11005 When a message is submitted locally (that is, not over a TCP connection)
11006 the value of &$authenticated_id$& is normally the login name of the calling
11007 process. However, a trusted user can override this by means of the &%-oMai%&
11008 command line option.
11009
11010 .vitem &$authenticated_fail_id$&
11011 .cindex "authentication" "fail" "id"
11012 .vindex "&$authenticated_fail_id$&"
11013 When an authentication attempt fails, the variable &$authenticated_fail_id$&
11014 will contain the failed authentication id. If more than one authentication
11015 id is attempted, it will contain only the last one. The variable is
11016 available for processing in the ACL's, generally the quit or notquit ACL.
11017 A message to a local recipient could still be accepted without requiring
11018 authentication, which means this variable could also be visible in all of
11019 the ACL's as well.
11020
11021
11022 .vitem &$authenticated_sender$&
11023 .cindex "sender" "authenticated"
11024 .cindex "authentication" "sender"
11025 .cindex "AUTH" "on MAIL command"
11026 .vindex "&$authenticated_sender$&"
11027 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
11028 SMTP MAIL command if it believes the sender is sufficiently trusted, as
11029 described in section &<<SECTauthparamail>>&. Unless the data is the string
11030 &"<>"&, it is set as the authenticated sender of the message, and the value is
11031 available during delivery in the &$authenticated_sender$& variable. If the
11032 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
11033
11034 .vindex "&$qualify_domain$&"
11035 When a message is submitted locally (that is, not over a TCP connection), the
11036 value of &$authenticated_sender$& is an address constructed from the login
11037 name of the calling process and &$qualify_domain$&, except that a trusted user
11038 can override this by means of the &%-oMas%& command line option.
11039
11040
11041 .vitem &$authentication_failed$&
11042 .cindex "authentication" "failure"
11043 .vindex "&$authentication_failed$&"
11044 This variable is set to &"1"& in an Exim server if a client issues an AUTH
11045 command that does not succeed. Otherwise it is set to &"0"&. This makes it
11046 possible to distinguish between &"did not try to authenticate"&
11047 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
11048 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
11049 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
11050 negative response to an AUTH command, including (for example) an attempt to use
11051 an undefined mechanism.
11052
11053 .vitem &$av_failed$&
11054 .cindex "content scanning" "AV scanner failure"
11055 This variable is available when Exim is compiled with the content-scanning
11056 extension. It is set to &"0"& by default, but will be set to &"1"& if any
11057 problem occurs with the virus scanner (specified by &%av_scanner%&) during
11058 the ACL malware condition.
11059
11060 .vitem &$body_linecount$&
11061 .cindex "message body" "line count"
11062 .cindex "body of message" "line count"
11063 .vindex "&$body_linecount$&"
11064 When a message is being received or delivered, this variable contains the
11065 number of lines in the message's body. See also &$message_linecount$&.
11066
11067 .vitem &$body_zerocount$&
11068 .cindex "message body" "binary zero count"
11069 .cindex "body of message" "binary zero count"
11070 .cindex "binary zero" "in message body"
11071 .vindex "&$body_zerocount$&"
11072 When a message is being received or delivered, this variable contains the
11073 number of binary zero bytes (ASCII NULs) in the message's body.
11074
11075 .vitem &$bounce_recipient$&
11076 .vindex "&$bounce_recipient$&"
11077 This is set to the recipient address of a bounce message while Exim is creating
11078 it. It is useful if a customized bounce message text file is in use (see
11079 chapter &<<CHAPemsgcust>>&).
11080
11081 .vitem &$bounce_return_size_limit$&
11082 .vindex "&$bounce_return_size_limit$&"
11083 This contains the value set in the &%bounce_return_size_limit%& option, rounded
11084 up to a multiple of 1000. It is useful when a customized error message text
11085 file is in use (see chapter &<<CHAPemsgcust>>&).
11086
11087 .vitem &$caller_gid$&
11088 .cindex "gid (group id)" "caller"
11089 .vindex "&$caller_gid$&"
11090 The real group id under which the process that called Exim was running. This is
11091 not the same as the group id of the originator of a message (see
11092 &$originator_gid$&). If Exim re-execs itself, this variable in the new
11093 incarnation normally contains the Exim gid.
11094
11095 .vitem &$caller_uid$&
11096 .cindex "uid (user id)" "caller"
11097 .vindex "&$caller_uid$&"
11098 The real user id under which the process that called Exim was running. This is
11099 not the same as the user id of the originator of a message (see
11100 &$originator_uid$&). If Exim re-execs itself, this variable in the new
11101 incarnation normally contains the Exim uid.
11102
11103 .vitem &$compile_date$&
11104 .vindex "&$compile_date$&"
11105 The date on which the Exim binary was compiled.
11106
11107 .vitem &$compile_number$&
11108 .vindex "&$compile_number$&"
11109 The building process for Exim keeps a count of the number
11110 of times it has been compiled. This serves to distinguish different
11111 compilations of the same version of the program.
11112
11113 .vitem &$demime_errorlevel$&
11114 .vindex "&$demime_errorlevel$&"
11115 This variable is available when Exim is compiled with
11116 the content-scanning extension and the obsolete &%demime%& condition. For
11117 details, see section &<<SECTdemimecond>>&.
11118
11119 .vitem &$demime_reason$&
11120 .vindex "&$demime_reason$&"
11121 This variable is available when Exim is compiled with the
11122 content-scanning extension and the obsolete &%demime%& condition. For details,
11123 see section &<<SECTdemimecond>>&.
11124
11125 .vitem &$dnslist_domain$& &&&
11126 &$dnslist_matched$& &&&
11127 &$dnslist_text$& &&&
11128 &$dnslist_value$&
11129 .vindex "&$dnslist_domain$&"
11130 .vindex "&$dnslist_matched$&"
11131 .vindex "&$dnslist_text$&"
11132 .vindex "&$dnslist_value$&"
11133 .cindex "black list (DNS)"
11134 When a DNS (black) list lookup succeeds, these variables are set to contain
11135 the following data from the lookup: the list's domain name, the key that was
11136 looked up, the contents of any associated TXT record, and the value from the
11137 main A record. See section &<<SECID204>>& for more details.
11138
11139 .vitem &$domain$&
11140 .vindex "&$domain$&"
11141 When an address is being routed, or delivered on its own, this variable
11142 contains the domain. Uppercase letters in the domain are converted into lower
11143 case for &$domain$&.
11144
11145 Global address rewriting happens when a message is received, so the value of
11146 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
11147 is set during user filtering, but not during system filtering, because a
11148 message may have many recipients and the system filter is called just once.
11149
11150 When more than one address is being delivered at once (for example, several
11151 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
11152 have the same domain. Transports can be restricted to handling only one domain
11153 at a time if the value of &$domain$& is required at transport time &-- this is
11154 the default for local transports. For further details of the environment in
11155 which local transports are run, see chapter &<<CHAPenvironment>>&.
11156
11157 .oindex "&%delay_warning_condition%&"
11158 At the end of a delivery, if all deferred addresses have the same domain, it is
11159 set in &$domain$& during the expansion of &%delay_warning_condition%&.
11160
11161 The &$domain$& variable is also used in some other circumstances:
11162
11163 .ilist
11164 When an ACL is running for a RCPT command, &$domain$& contains the domain of
11165 the recipient address. The domain of the &'sender'& address is in
11166 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
11167 normally set during the running of the MAIL ACL. However, if the sender address
11168 is verified with a callout during the MAIL ACL, the sender domain is placed in
11169 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
11170 the &(smtp)& transport.
11171
11172 .next
11173 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
11174 &$domain$& contains the domain portion of the address that is being rewritten;
11175 it can be used in the expansion of the replacement address, for example, to
11176 rewrite domains by file lookup.
11177
11178 .next
11179 With one important exception, whenever a domain list is being scanned,
11180 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
11181 a &%sender_domains%& condition in an ACL is being processed, the subject domain
11182 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
11183 that, in a RCPT ACL, the sender domain list can be dependent on the
11184 recipient domain (which is what is in &$domain$& at this time).
11185
11186 .next
11187 .cindex "ETRN" "value of &$domain$&"
11188 .oindex "&%smtp_etrn_command%&"
11189 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
11190 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
11191 .endlist
11192
11193
11194 .vitem &$domain_data$&
11195 .vindex "&$domain_data$&"
11196 When the &%domains%& option on a router matches a domain by
11197 means of a lookup, the data read by the lookup is available during the running
11198 of the router as &$domain_data$&. In addition, if the driver routes the
11199 address to a transport, the value is available in that transport. If the
11200 transport is handling multiple addresses, the value from the first address is
11201 used.
11202
11203 &$domain_data$& is also set when the &%domains%& condition in an ACL matches a
11204 domain by means of a lookup. The data read by the lookup is available during
11205 the rest of the ACL statement. In all other situations, this variable expands
11206 to nothing.
11207
11208 .vitem &$exim_gid$&
11209 .vindex "&$exim_gid$&"
11210 This variable contains the numerical value of the Exim group id.
11211
11212 .vitem &$exim_path$&
11213 .vindex "&$exim_path$&"
11214 This variable contains the path to the Exim binary.
11215
11216 .vitem &$exim_uid$&
11217 .vindex "&$exim_uid$&"
11218 This variable contains the numerical value of the Exim user id.
11219
11220 .vitem &$found_extension$&
11221 .vindex "&$found_extension$&"
11222 This variable is available when Exim is compiled with the
11223 content-scanning extension and the obsolete &%demime%& condition. For details,
11224 see section &<<SECTdemimecond>>&.
11225
11226 .vitem &$header_$&<&'name'&>
11227 This is not strictly an expansion variable. It is expansion syntax for
11228 inserting the message header line with the given name. Note that the name must
11229 be terminated by colon or white space, because it may contain a wide variety of
11230 characters. Note also that braces must &'not'& be used.
11231
11232 .vitem &$headers_added$&
11233 .vindex "&$headers_added$&"
11234 Within an ACL this variable contains the headers added so far by
11235 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
11236 The headers are a newline-separated list.
11237
11238 .vitem &$home$&
11239 .vindex "&$home$&"
11240 When the &%check_local_user%& option is set for a router, the user's home
11241 directory is placed in &$home$& when the check succeeds. In particular, this
11242 means it is set during the running of users' filter files. A router may also
11243 explicitly set a home directory for use by a transport; this can be overridden
11244 by a setting on the transport itself.
11245
11246 When running a filter test via the &%-bf%& option, &$home$& is set to the value
11247 of the environment variable HOME.
11248
11249 .vitem &$host$&
11250 .vindex "&$host$&"
11251 If a router assigns an address to a transport (any transport), and passes a
11252 list of hosts with the address, the value of &$host$& when the transport starts
11253 to run is the name of the first host on the list. Note that this applies both
11254 to local and remote transports.
11255
11256 .cindex "transport" "filter"
11257 .cindex "filter" "transport filter"
11258 For the &(smtp)& transport, if there is more than one host, the value of
11259 &$host$& changes as the transport works its way through the list. In
11260 particular, when the &(smtp)& transport is expanding its options for encryption
11261 using TLS, or for specifying a transport filter (see chapter
11262 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
11263 is connected.
11264
11265 When used in the client part of an authenticator configuration (see chapter
11266 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
11267 client is connected.
11268
11269
11270 .vitem &$host_address$&
11271 .vindex "&$host_address$&"
11272 This variable is set to the remote host's IP address whenever &$host$& is set
11273 for a remote connection. It is also set to the IP address that is being checked
11274 when the &%ignore_target_hosts%& option is being processed.
11275
11276 .vitem &$host_data$&
11277 .vindex "&$host_data$&"
11278 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
11279 result of the lookup is made available in the &$host_data$& variable. This
11280 allows you, for example, to do things like this:
11281 .code
11282 deny hosts = net-lsearch;/some/file
11283 message = $host_data
11284 .endd
11285 .vitem &$host_lookup_deferred$&
11286 .cindex "host name" "lookup, failure of"
11287 .vindex "&$host_lookup_deferred$&"
11288 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
11289 message comes from a remote host and there is an attempt to look up the host's
11290 name from its IP address, and the attempt is not successful, one of these
11291 variables is set to &"1"&.
11292
11293 .ilist
11294 If the lookup receives a definite negative response (for example, a DNS lookup
11295 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
11296
11297 .next
11298 If there is any kind of problem during the lookup, such that Exim cannot
11299 tell whether or not the host name is defined (for example, a timeout for a DNS
11300 lookup), &$host_lookup_deferred$& is set to &"1"&.
11301 .endlist ilist
11302
11303 Looking up a host's name from its IP address consists of more than just a
11304 single reverse lookup. Exim checks that a forward lookup of at least one of the
11305 names it receives from a reverse lookup yields the original IP address. If this
11306 is not the case, Exim does not accept the looked up name(s), and
11307 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
11308 IP address (for example, the existence of a PTR record in the DNS) is not
11309 sufficient on its own for the success of a host name lookup. If the reverse
11310 lookup succeeds, but there is a lookup problem such as a timeout when checking
11311 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
11312 &"1"&. See also &$sender_host_name$&.
11313
11314 .vitem &$host_lookup_failed$&
11315 .vindex "&$host_lookup_failed$&"
11316 See &$host_lookup_deferred$&.
11317
11318
11319 .vitem &$inode$&
11320 .vindex "&$inode$&"
11321 The only time this variable is set is while expanding the &%directory_file%&
11322 option in the &(appendfile)& transport. The variable contains the inode number
11323 of the temporary file which is about to be renamed. It can be used to construct
11324 a unique name for the file.
11325
11326 .vitem &$interface_address$&
11327 .vindex "&$interface_address$&"
11328 This is an obsolete name for &$received_ip_address$&.
11329
11330 .vitem &$interface_port$&
11331 .vindex "&$interface_port$&"
11332 This is an obsolete name for &$received_port$&.
11333
11334 .vitem &$item$&
11335 .vindex "&$item$&"
11336 This variable is used during the expansion of &*forall*& and &*forany*&
11337 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
11338 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
11339 empty.
11340
11341 .vitem &$ldap_dn$&
11342 .vindex "&$ldap_dn$&"
11343 This variable, which is available only when Exim is compiled with LDAP support,
11344 contains the DN from the last entry in the most recently successful LDAP
11345 lookup.
11346
11347 .vitem &$load_average$&
11348 .vindex "&$load_average$&"
11349 This variable contains the system load average, multiplied by 1000 so that it
11350 is an integer. For example, if the load average is 0.21, the value of the
11351 variable is 210. The value is recomputed every time the variable is referenced.
11352
11353 .vitem &$local_part$&
11354 .vindex "&$local_part$&"
11355 When an address is being routed, or delivered on its own, this
11356 variable contains the local part. When a number of addresses are being
11357 delivered together (for example, multiple RCPT commands in an SMTP
11358 session), &$local_part$& is not set.
11359
11360 Global address rewriting happens when a message is received, so the value of
11361 &$local_part$& during routing and delivery is the value after rewriting.
11362 &$local_part$& is set during user filtering, but not during system filtering,
11363 because a message may have many recipients and the system filter is called just
11364 once.
11365
11366 .vindex "&$local_part_prefix$&"
11367 .vindex "&$local_part_suffix$&"
11368 If a local part prefix or suffix has been recognized, it is not included in the
11369 value of &$local_part$& during routing and subsequent delivery. The values of
11370 any prefix or suffix are in &$local_part_prefix$& and
11371 &$local_part_suffix$&, respectively.
11372
11373 When a message is being delivered to a file, pipe, or autoreply transport as a
11374 result of aliasing or forwarding, &$local_part$& is set to the local part of
11375 the parent address, not to the file name or command (see &$address_file$& and
11376 &$address_pipe$&).
11377
11378 When an ACL is running for a RCPT command, &$local_part$& contains the
11379 local part of the recipient address.
11380
11381 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
11382 &$local_part$& contains the local part of the address that is being rewritten;
11383 it can be used in the expansion of the replacement address, for example.
11384
11385 In all cases, all quoting is removed from the local part. For example, for both
11386 the addresses
11387 .code
11388 "abc:xyz"@test.example
11389 abc\:xyz@test.example
11390 .endd
11391 the value of &$local_part$& is
11392 .code
11393 abc:xyz
11394 .endd
11395 If you use &$local_part$& to create another address, you should always wrap it
11396 inside a quoting operator. For example, in a &(redirect)& router you could
11397 have:
11398 .code
11399 data = ${quote_local_part:$local_part}@new.domain.example
11400 .endd
11401 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
11402 to process local parts in a case-dependent manner in a router, you can set the
11403 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
11404
11405 .vitem &$local_part_data$&
11406 .vindex "&$local_part_data$&"
11407 When the &%local_parts%& option on a router matches a local part by means of a
11408 lookup, the data read by the lookup is available during the running of the
11409 router as &$local_part_data$&. In addition, if the driver routes the address
11410 to a transport, the value is available in that transport. If the transport is
11411 handling multiple addresses, the value from the first address is used.
11412
11413 &$local_part_data$& is also set when the &%local_parts%& condition in an ACL
11414 matches a local part by means of a lookup. The data read by the lookup is
11415 available during the rest of the ACL statement. In all other situations, this
11416 variable expands to nothing.
11417
11418 .vitem &$local_part_prefix$&
11419 .vindex "&$local_part_prefix$&"
11420 When an address is being routed or delivered, and a
11421 specific prefix for the local part was recognized, it is available in this
11422 variable, having been removed from &$local_part$&.
11423
11424 .vitem &$local_part_suffix$&
11425 .vindex "&$local_part_suffix$&"
11426 When an address is being routed or delivered, and a
11427 specific suffix for the local part was recognized, it is available in this
11428 variable, having been removed from &$local_part$&.
11429
11430 .vitem &$local_scan_data$&
11431 .vindex "&$local_scan_data$&"
11432 This variable contains the text returned by the &[local_scan()]& function when
11433 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
11434
11435 .vitem &$local_user_gid$&
11436 .vindex "&$local_user_gid$&"
11437 See &$local_user_uid$&.
11438
11439 .vitem &$local_user_uid$&
11440 .vindex "&$local_user_uid$&"
11441 This variable and &$local_user_gid$& are set to the uid and gid after the
11442 &%check_local_user%& router precondition succeeds. This means that their values
11443 are available for the remaining preconditions (&%senders%&, &%require_files%&,
11444 and &%condition%&), for the &%address_data%& expansion, and for any
11445 router-specific expansions. At all other times, the values in these variables
11446 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
11447
11448 .vitem &$localhost_number$&
11449 .vindex "&$localhost_number$&"
11450 This contains the expanded value of the
11451 &%localhost_number%& option. The expansion happens after the main options have
11452 been read.
11453
11454 .vitem &$log_inodes$&
11455 .vindex "&$log_inodes$&"
11456 The number of free inodes in the disk partition where Exim's
11457 log files are being written. The value is recalculated whenever the variable is
11458 referenced. If the relevant file system does not have the concept of inodes,
11459 the value of is -1. See also the &%check_log_inodes%& option.
11460
11461 .vitem &$log_space$&
11462 .vindex "&$log_space$&"
11463 The amount of free space (as a number of kilobytes) in the disk
11464 partition where Exim's log files are being written. The value is recalculated
11465 whenever the variable is referenced. If the operating system does not have the
11466 ability to find the amount of free space (only true for experimental systems),
11467 the space value is -1. See also the &%check_log_space%& option.
11468
11469
11470 .new
11471 .vitem &$lookup_dnssec_authenticated$&
11472 .vindex "&$lookup_dnssec_authenticated$&"
11473 This variable is set after a DNS lookup done by
11474 either a dnslookup router or a dnsdb lookup expansion.
11475 It will be empty if &(DNSSEC)& was not requested,
11476 &"no"& if the result was not labelled as authenticated data
11477 and &"yes"& if it was.
11478 .wen
11479
11480 .vitem &$mailstore_basename$&
11481 .vindex "&$mailstore_basename$&"
11482 This variable is set only when doing deliveries in &"mailstore"& format in the
11483 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
11484 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
11485 contains the basename of the files that are being written, that is, the name
11486 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
11487 variable is empty.
11488
11489 .vitem &$malware_name$&
11490 .vindex "&$malware_name$&"
11491 This variable is available when Exim is compiled with the
11492 content-scanning extension. It is set to the name of the virus that was found
11493 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
11494
11495 .vitem &$max_received_linelength$&
11496 .vindex "&$max_received_linelength$&"
11497 .cindex "maximum" "line length"
11498 .cindex "line length" "maximum"
11499 This variable contains the number of bytes in the longest line that was
11500 received as part of the message, not counting the line termination
11501 character(s).
11502
11503 .vitem &$message_age$&
11504 .cindex "message" "age of"
11505 .vindex "&$message_age$&"
11506 This variable is set at the start of a delivery attempt to contain the number
11507 of seconds since the message was received. It does not change during a single
11508 delivery attempt.
11509
11510 .vitem &$message_body$&
11511 .cindex "body of message" "expansion variable"
11512 .cindex "message body" "in expansion"
11513 .cindex "binary zero" "in message body"
11514 .vindex "&$message_body$&"
11515 .oindex "&%message_body_visible%&"
11516 This variable contains the initial portion of a message's body while it is
11517 being delivered, and is intended mainly for use in filter files. The maximum
11518 number of characters of the body that are put into the variable is set by the
11519 &%message_body_visible%& configuration option; the default is 500.
11520
11521 .oindex "&%message_body_newlines%&"
11522 By default, newlines are converted into spaces in &$message_body$&, to make it
11523 easier to search for phrases that might be split over a line break. However,
11524 this can be disabled by setting &%message_body_newlines%& to be true. Binary
11525 zeros are always converted into spaces.
11526
11527 .vitem &$message_body_end$&
11528 .cindex "body of message" "expansion variable"
11529 .cindex "message body" "in expansion"
11530 .vindex "&$message_body_end$&"
11531 This variable contains the final portion of a message's
11532 body while it is being delivered. The format and maximum size are as for
11533 &$message_body$&.
11534
11535 .vitem &$message_body_size$&
11536 .cindex "body of message" "size"
11537 .cindex "message body" "size"
11538 .vindex "&$message_body_size$&"
11539 When a message is being delivered, this variable contains the size of the body
11540 in bytes. The count starts from the character after the blank line that
11541 separates the body from the header. Newlines are included in the count. See
11542 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
11543
11544 .vitem &$message_exim_id$&
11545 .vindex "&$message_exim_id$&"
11546 When a message is being received or delivered, this variable contains the
11547 unique message id that is generated and used by Exim to identify the message.
11548 An id is not created for a message until after its header has been successfully
11549 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
11550 line; it is the local id that Exim assigns to the message, for example:
11551 &`1BXTIK-0001yO-VA`&.
11552
11553 .vitem &$message_headers$&
11554 .vindex &$message_headers$&
11555 This variable contains a concatenation of all the header lines when a message
11556 is being processed, except for lines added by routers or transports. The header
11557 lines are separated by newline characters. Their contents are decoded in the
11558 same way as a header line that is inserted by &%bheader%&.
11559
11560 .vitem &$message_headers_raw$&
11561 .vindex &$message_headers_raw$&
11562 This variable is like &$message_headers$& except that no processing of the
11563 contents of header lines is done.
11564
11565 .vitem &$message_id$&
11566 This is an old name for &$message_exim_id$&, which is now deprecated.
11567
11568 .vitem &$message_linecount$&
11569 .vindex "&$message_linecount$&"
11570 This variable contains the total number of lines in the header and body of the
11571 message. Compare &$body_linecount$&, which is the count for the body only.
11572 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
11573 number of lines received. Before delivery happens (that is, before filters,
11574 routers, and transports run) the count is increased to include the
11575 &'Received:'& header line that Exim standardly adds, and also any other header
11576 lines that are added by ACLs. The blank line that separates the message header
11577 from the body is not counted.
11578
11579 As with the special case of &$message_size$&, during the expansion of the
11580 appendfile transport's maildir_tag option in maildir format, the value of
11581 &$message_linecount$& is the precise size of the number of newlines in the
11582 file that has been written (minus one for the blank line between the
11583 header and the body).
11584
11585 Here is an example of the use of this variable in a DATA ACL:
11586 .code
11587 deny message = Too many lines in message header
11588 condition = \
11589 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
11590 .endd
11591 In the MAIL and RCPT ACLs, the value is zero because at that stage the
11592 message has not yet been received.
11593
11594 .vitem &$message_size$&
11595 .cindex "size" "of message"
11596 .cindex "message" "size"
11597 .vindex "&$message_size$&"
11598 When a message is being processed, this variable contains its size in bytes. In
11599 most cases, the size includes those headers that were received with the
11600 message, but not those (such as &'Envelope-to:'&) that are added to individual
11601 deliveries as they are written. However, there is one special case: during the
11602 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
11603 doing a delivery in maildir format, the value of &$message_size$& is the
11604 precise size of the file that has been written. See also
11605 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
11606
11607 .cindex "RCPT" "value of &$message_size$&"
11608 While running a per message ACL (mail/rcpt/predata), &$message_size$&
11609 contains the size supplied on the MAIL command, or -1 if no size was given. The
11610 value may not, of course, be truthful.
11611
11612 .vitem &$mime_$&&'xxx'&
11613 A number of variables whose names start with &$mime$& are
11614 available when Exim is compiled with the content-scanning extension. For
11615 details, see section &<<SECTscanmimepart>>&.
11616
11617 .vitem "&$n0$& &-- &$n9$&"
11618 These variables are counters that can be incremented by means
11619 of the &%add%& command in filter files.
11620
11621 .vitem &$original_domain$&
11622 .vindex "&$domain$&"
11623 .vindex "&$original_domain$&"
11624 When a top-level address is being processed for delivery, this contains the
11625 same value as &$domain$&. However, if a &"child"& address (for example,
11626 generated by an alias, forward, or filter file) is being processed, this
11627 variable contains the domain of the original address (lower cased). This
11628 differs from &$parent_domain$& only when there is more than one level of
11629 aliasing or forwarding. When more than one address is being delivered in a
11630 single transport run, &$original_domain$& is not set.
11631
11632 If a new address is created by means of a &%deliver%& command in a system
11633 filter, it is set up with an artificial &"parent"& address. This has the local
11634 part &'system-filter'& and the default qualify domain.
11635
11636 .vitem &$original_local_part$&
11637 .vindex "&$local_part$&"
11638 .vindex "&$original_local_part$&"
11639 When a top-level address is being processed for delivery, this contains the
11640 same value as &$local_part$&, unless a prefix or suffix was removed from the
11641 local part, because &$original_local_part$& always contains the full local
11642 part. When a &"child"& address (for example, generated by an alias, forward, or
11643 filter file) is being processed, this variable contains the full local part of
11644 the original address.
11645
11646 If the router that did the redirection processed the local part
11647 case-insensitively, the value in &$original_local_part$& is in lower case.
11648 This variable differs from &$parent_local_part$& only when there is more than
11649 one level of aliasing or forwarding. When more than one address is being
11650 delivered in a single transport run, &$original_local_part$& is not set.
11651
11652 If a new address is created by means of a &%deliver%& command in a system
11653 filter, it is set up with an artificial &"parent"& address. This has the local
11654 part &'system-filter'& and the default qualify domain.
11655
11656 .vitem &$originator_gid$&
11657 .cindex "gid (group id)" "of originating user"
11658 .cindex "sender" "gid"
11659 .vindex "&$caller_gid$&"
11660 .vindex "&$originator_gid$&"
11661 This variable contains the value of &$caller_gid$& that was set when the
11662 message was received. For messages received via the command line, this is the
11663 gid of the sending user. For messages received by SMTP over TCP/IP, this is
11664 normally the gid of the Exim user.
11665
11666 .vitem &$originator_uid$&
11667 .cindex "uid (user id)" "of originating user"
11668 .cindex "sender" "uid"
11669 .vindex "&$caller_uid$&"
11670 .vindex "&$originaltor_uid$&"
11671 The value of &$caller_uid$& that was set when the message was received. For
11672 messages received via the command line, this is the uid of the sending user.
11673 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
11674 user.
11675
11676 .vitem &$parent_domain$&
11677 .vindex "&$parent_domain$&"
11678 This variable is similar to &$original_domain$& (see
11679 above), except that it refers to the immediately preceding parent address.
11680
11681 .vitem &$parent_local_part$&
11682 .vindex "&$parent_local_part$&"
11683 This variable is similar to &$original_local_part$&
11684 (see above), except that it refers to the immediately preceding parent address.
11685
11686 .vitem &$pid$&
11687 .cindex "pid (process id)" "of current process"
11688 .vindex "&$pid$&"
11689 This variable contains the current process id.
11690
11691 .vitem &$pipe_addresses$&
11692 .cindex "filter" "transport filter"
11693 .cindex "transport" "filter"
11694 .vindex "&$pipe_addresses$&"
11695 This is not an expansion variable, but is mentioned here because the string
11696 &`$pipe_addresses`& is handled specially in the command specification for the
11697 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
11698 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
11699 It cannot be used in general expansion strings, and provokes an &"unknown
11700 variable"& error if encountered.
11701
11702 .vitem &$primary_hostname$&
11703 .vindex "&$primary_hostname$&"
11704 This variable contains the value set by &%primary_hostname%& in the
11705 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
11706 a single-component name, Exim calls &[gethostbyname()]& (or
11707 &[getipnodebyname()]& where available) in an attempt to acquire a fully
11708 qualified host name. See also &$smtp_active_hostname$&.
11709
11710
11711 .vitem &$prvscheck_address$&
11712 This variable is used in conjunction with the &%prvscheck%& expansion item,
11713 which is described in sections &<<SECTexpansionitems>>& and
11714 &<<SECTverifyPRVS>>&.
11715
11716 .vitem &$prvscheck_keynum$&
11717 This variable is used in conjunction with the &%prvscheck%& expansion item,
11718 which is described in sections &<<SECTexpansionitems>>& and
11719 &<<SECTverifyPRVS>>&.
11720
11721 .vitem &$prvscheck_result$&
11722 This variable is used in conjunction with the &%prvscheck%& expansion item,
11723 which is described in sections &<<SECTexpansionitems>>& and
11724 &<<SECTverifyPRVS>>&.
11725
11726 .vitem &$qualify_domain$&
11727 .vindex "&$qualify_domain$&"
11728 The value set for the &%qualify_domain%& option in the configuration file.
11729
11730 .vitem &$qualify_recipient$&
11731 .vindex "&$qualify_recipient$&"
11732 The value set for the &%qualify_recipient%& option in the configuration file,
11733 or if not set, the value of &$qualify_domain$&.
11734
11735 .vitem &$rcpt_count$&
11736 .vindex "&$rcpt_count$&"
11737 When a message is being received by SMTP, this variable contains the number of
11738 RCPT commands received for the current message. If this variable is used in a
11739 RCPT ACL, its value includes the current command.
11740
11741 .vitem &$rcpt_defer_count$&
11742 .vindex "&$rcpt_defer_count$&"
11743 .cindex "4&'xx'& responses" "count of"
11744 When a message is being received by SMTP, this variable contains the number of
11745 RCPT commands in the current message that have previously been rejected with a
11746 temporary (4&'xx'&) response.
11747
11748 .vitem &$rcpt_fail_count$&
11749 .vindex "&$rcpt_fail_count$&"
11750 When a message is being received by SMTP, this variable contains the number of
11751 RCPT commands in the current message that have previously been rejected with a
11752 permanent (5&'xx'&) response.
11753
11754 .vitem &$received_count$&
11755 .vindex "&$received_count$&"
11756 This variable contains the number of &'Received:'& header lines in the message,
11757 including the one added by Exim (so its value is always greater than zero). It
11758 is available in the DATA ACL, the non-SMTP ACL, and while routing and
11759 delivering.
11760
11761 .vitem &$received_for$&
11762 .vindex "&$received_for$&"
11763 If there is only a single recipient address in an incoming message, this
11764 variable contains that address when the &'Received:'& header line is being
11765 built. The value is copied after recipient rewriting has happened, but before
11766 the &[local_scan()]& function is run.
11767
11768 .vitem &$received_ip_address$&
11769 .vindex "&$received_ip_address$&"
11770 As soon as an Exim server starts processing an incoming TCP/IP connection, this
11771 variable is set to the address of the local IP interface, and &$received_port$&
11772 is set to the local port number. (The remote IP address and port are in
11773 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
11774 the port value is -1 unless it has been set using the &%-oMi%& command line
11775 option.
11776
11777 As well as being useful in ACLs (including the &"connect"& ACL), these variable
11778 could be used, for example, to make the file name for a TLS certificate depend
11779 on which interface and/or port is being used for the incoming connection. The
11780 values of &$received_ip_address$& and &$received_port$& are saved with any
11781 messages that are received, thus making these variables available at delivery
11782 time.
11783
11784 &*Note:*& There are no equivalent variables for outgoing connections, because
11785 the values are unknown (unless they are explicitly set by options of the
11786 &(smtp)& transport).
11787
11788 .vitem &$received_port$&
11789 .vindex "&$received_port$&"
11790 See &$received_ip_address$&.
11791
11792 .vitem &$received_protocol$&
11793 .vindex "&$received_protocol$&"
11794 When a message is being processed, this variable contains the name of the
11795 protocol by which it was received. Most of the names used by Exim are defined
11796 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
11797 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
11798 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
11799 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
11800 connection and the client was successfully authenticated.
11801
11802 Exim uses the protocol name &"smtps"& for the case when encryption is
11803 automatically set up on connection without the use of STARTTLS (see
11804 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
11805 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
11806 where the client initially uses EHLO, sets up an encrypted connection using
11807 STARTTLS, and then uses HELO afterwards.
11808
11809 The &%-oMr%& option provides a way of specifying a custom protocol name for
11810 messages that are injected locally by trusted callers. This is commonly used to
11811 identify messages that are being re-injected after some kind of scanning.
11812
11813 .vitem &$received_time$&
11814 .vindex "&$received_time$&"
11815 This variable contains the date and time when the current message was received,
11816 as a number of seconds since the start of the Unix epoch.
11817
11818 .vitem &$recipient_data$&
11819 .vindex "&$recipient_data$&"
11820 This variable is set after an indexing lookup success in an ACL &%recipients%&
11821 condition. It contains the data from the lookup, and the value remains set
11822 until the next &%recipients%& test. Thus, you can do things like this:
11823 .display
11824 &`require recipients = cdb*@;/some/file`&
11825 &`deny `&&'some further test involving'& &`$recipient_data`&
11826 .endd
11827 &*Warning*&: This variable is set only when a lookup is used as an indexing
11828 method in the address list, using the semicolon syntax as in the example above.
11829 The variable is not set for a lookup that is used as part of the string
11830 expansion that all such lists undergo before being interpreted.
11831
11832 .vitem &$recipient_verify_failure$&
11833 .vindex "&$recipient_verify_failure$&"
11834 In an ACL, when a recipient verification fails, this variable contains
11835 information about the failure. It is set to one of the following words:
11836
11837 .ilist
11838 &"qualify"&: The address was unqualified (no domain), and the message
11839 was neither local nor came from an exempted host.
11840
11841 .next
11842 &"route"&: Routing failed.
11843
11844 .next
11845 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
11846 or before the MAIL command (that is, on initial connection, HELO, or
11847 MAIL).
11848
11849 .next
11850 &"recipient"&: The RCPT command in a callout was rejected.
11851 .next
11852
11853 &"postmaster"&: The postmaster check in a callout was rejected.
11854 .endlist
11855
11856 The main use of this variable is expected to be to distinguish between
11857 rejections of MAIL and rejections of RCPT.
11858
11859 .vitem &$recipients$&
11860 .vindex "&$recipients$&"
11861 This variable contains a list of envelope recipients for a message. A comma and
11862 a space separate the addresses in the replacement text. However, the variable
11863 is not generally available, to prevent exposure of Bcc recipients in
11864 unprivileged users' filter files. You can use &$recipients$& only in these
11865 cases:
11866
11867 .olist
11868 In a system filter file.
11869 .next
11870 In the ACLs associated with the DATA command and with non-SMTP messages, that
11871 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
11872 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
11873 &%acl_not_smtp_mime%&.
11874 .next
11875 From within a &[local_scan()]& function.
11876 .endlist
11877
11878
11879 .vitem &$recipients_count$&
11880 .vindex "&$recipients_count$&"
11881 When a message is being processed, this variable contains the number of
11882 envelope recipients that came with the message. Duplicates are not excluded
11883 from the count. While a message is being received over SMTP, the number
11884 increases for each accepted recipient. It can be referenced in an ACL.
11885
11886
11887 .vitem &$regex_match_string$&
11888 .vindex "&$regex_match_string$&"
11889 This variable is set to contain the matching regular expression after a
11890 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
11891
11892
11893 .vitem &$reply_address$&
11894 .vindex "&$reply_address$&"
11895 When a message is being processed, this variable contains the contents of the
11896 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
11897 contents of the &'From:'& header line. Apart from the removal of leading
11898 white space, the value is not processed in any way. In particular, no RFC 2047
11899 decoding or character code translation takes place.
11900
11901 .vitem &$return_path$&
11902 .vindex "&$return_path$&"
11903 When a message is being delivered, this variable contains the return path &--
11904 the sender field that will be sent as part of the envelope. It is not enclosed
11905 in <> characters. At the start of routing an address, &$return_path$& has the
11906 same value as &$sender_address$&, but if, for example, an incoming message to a
11907 mailing list has been expanded by a router which specifies a different address
11908 for bounce messages, &$return_path$& subsequently contains the new bounce
11909 address, whereas &$sender_address$& always contains the original sender address
11910 that was received with the message. In other words, &$sender_address$& contains
11911 the incoming envelope sender, and &$return_path$& contains the outgoing
11912 envelope sender.
11913
11914 .vitem &$return_size_limit$&
11915 .vindex "&$return_size_limit$&"
11916 This is an obsolete name for &$bounce_return_size_limit$&.
11917
11918 .vitem &$router_name$&
11919 .cindex "router" "name"
11920 .cindex "name" "of router"
11921 .vindex "&$router_name$&"
11922 During the running of a router this variable contains its name.
11923
11924 .vitem &$runrc$&
11925 .cindex "return code" "from &%run%& expansion"
11926 .vindex "&$runrc$&"
11927 This variable contains the return code from a command that is run by the
11928 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
11929 assume the order in which option values are expanded, except for those
11930 preconditions whose order of testing is documented. Therefore, you cannot
11931 reliably expect to set &$runrc$& by the expansion of one option, and use it in
11932 another.
11933
11934 .vitem &$self_hostname$&
11935 .oindex "&%self%&" "value of host name"
11936 .vindex "&$self_hostname$&"
11937 When an address is routed to a supposedly remote host that turns out to be the
11938 local host, what happens is controlled by the &%self%& generic router option.
11939 One of its values causes the address to be passed to another router. When this
11940 happens, &$self_hostname$& is set to the name of the local host that the
11941 original router encountered. In other circumstances its contents are null.
11942
11943 .vitem &$sender_address$&
11944 .vindex "&$sender_address$&"
11945 When a message is being processed, this variable contains the sender's address
11946 that was received in the message's envelope. The case of letters in the address
11947 is retained, in both the local part and the domain. For bounce messages, the
11948 value of this variable is the empty string. See also &$return_path$&.
11949
11950 .vitem &$sender_address_data$&
11951 .vindex "&$address_data$&"
11952 .vindex "&$sender_address_data$&"
11953 If &$address_data$& is set when the routers are called from an ACL to verify a
11954 sender address, the final value is preserved in &$sender_address_data$&, to
11955 distinguish it from data from a recipient address. The value does not persist
11956 after the end of the current ACL statement. If you want to preserve it for
11957 longer, you can save it in an ACL variable.
11958
11959 .vitem &$sender_address_domain$&
11960 .vindex "&$sender_address_domain$&"
11961 The domain portion of &$sender_address$&.
11962
11963 .vitem &$sender_address_local_part$&
11964 .vindex "&$sender_address_local_part$&"
11965 The local part portion of &$sender_address$&.
11966
11967 .vitem &$sender_data$&
11968 .vindex "&$sender_data$&"
11969 This variable is set after a lookup success in an ACL &%senders%& condition or
11970 in a router &%senders%& option. It contains the data from the lookup, and the
11971 value remains set until the next &%senders%& test. Thus, you can do things like
11972 this:
11973 .display
11974 &`require senders = cdb*@;/some/file`&
11975 &`deny `&&'some further test involving'& &`$sender_data`&
11976 .endd
11977 &*Warning*&: This variable is set only when a lookup is used as an indexing
11978 method in the address list, using the semicolon syntax as in the example above.
11979 The variable is not set for a lookup that is used as part of the string
11980 expansion that all such lists undergo before being interpreted.
11981
11982 .vitem &$sender_fullhost$&
11983 .vindex "&$sender_fullhost$&"
11984 When a message is received from a remote host, this variable contains the host
11985 name and IP address in a single string. It ends with the IP address in square
11986 brackets, followed by a colon and a port number if the logging of ports is
11987 enabled. The format of the rest of the string depends on whether the host
11988 issued a HELO or EHLO SMTP command, and whether the host name was verified by
11989 looking up its IP address. (Looking up the IP address can be forced by the
11990 &%host_lookup%& option, independent of verification.) A plain host name at the
11991 start of the string is a verified host name; if this is not present,
11992 verification either failed or was not requested. A host name in parentheses is
11993 the argument of a HELO or EHLO command. This is omitted if it is identical to
11994 the verified host name or to the host's IP address in square brackets.
11995
11996 .vitem &$sender_helo_name$&
11997 .vindex "&$sender_helo_name$&"
11998 When a message is received from a remote host that has issued a HELO or EHLO
11999 command, the argument of that command is placed in this variable. It is also
12000 set if HELO or EHLO is used when a message is received using SMTP locally via
12001 the &%-bs%& or &%-bS%& options.
12002
12003 .vitem &$sender_host_address$&
12004 .vindex "&$sender_host_address$&"
12005 When a message is received from a remote host, this variable contains that
12006 host's IP address. For locally submitted messages, it is empty.
12007
12008 .vitem &$sender_host_authenticated$&
12009 .vindex "&$sender_host_authenticated$&"
12010 This variable contains the name (not the public name) of the authenticator
12011 driver that successfully authenticated the client from which the message was
12012 received. It is empty if there was no successful authentication. See also
12013 &$authenticated_id$&.
12014
12015 .vitem &$sender_host_dnssec$&
12016 .vindex "&$sender_host_dnssec$&"
12017 If &$sender_host_name$& has been populated (by reference, &%hosts_lookup%& or
12018 otherwise) then this boolean will have been set true if, and only if, the
12019 resolver library states that the reverse DNS was authenticated data. At all
12020 other times, this variable is false.
12021
12022 It is likely that you will need to coerce DNSSEC support on in the resolver
12023 library, by setting:
12024 .code
12025 dns_dnssec_ok = 1
12026 .endd
12027
12028 Exim does not perform DNSSEC validation itself, instead leaving that to a
12029 validating resolver (eg, unbound, or bind with suitable configuration).
12030
12031 Exim does not (currently) check to see if the forward DNS was also secured
12032 with DNSSEC, only the reverse DNS.
12033
12034 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
12035 mechanism in the list, then this variable will be false.
12036
12037
12038 .vitem &$sender_host_name$&
12039 .vindex "&$sender_host_name$&"
12040 When a message is received from a remote host, this variable contains the
12041 host's name as obtained by looking up its IP address. For messages received by
12042 other means, this variable is empty.
12043
12044 .vindex "&$host_lookup_failed$&"
12045 If the host name has not previously been looked up, a reference to
12046 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
12047 A looked up name is accepted only if it leads back to the original IP address
12048 via a forward lookup. If either the reverse or the forward lookup fails to find
12049 any data, or if the forward lookup does not yield the original IP address,
12050 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
12051
12052 .vindex "&$host_lookup_deferred$&"
12053 However, if either of the lookups cannot be completed (for example, there is a
12054 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
12055 &$host_lookup_failed$& remains set to &"0"&.
12056
12057 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
12058 host name again if there is a subsequent reference to &$sender_host_name$&
12059 in the same Exim process, but it does try again if &$host_lookup_deferred$&
12060 is set to &"1"&.
12061
12062 Exim does not automatically look up every calling host's name. If you want
12063 maximum efficiency, you should arrange your configuration so that it avoids
12064 these lookups altogether. The lookup happens only if one or more of the
12065 following are true:
12066
12067 .ilist
12068 A string containing &$sender_host_name$& is expanded.
12069 .next
12070 The calling host matches the list in &%host_lookup%&. In the default
12071 configuration, this option is set to *, so it must be changed if lookups are
12072 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
12073 .next
12074 Exim needs the host name in order to test an item in a host list. The items
12075 that require this are described in sections &<<SECThoslispatnam>>& and
12076 &<<SECThoslispatnamsk>>&.
12077 .next
12078 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
12079 In this case, the host name is required to compare with the name quoted in any
12080 EHLO or HELO commands that the client issues.
12081 .next
12082 The remote host issues a EHLO or HELO command that quotes one of the
12083 domains in &%helo_lookup_domains%&. The default value of this option is
12084 . ==== As this is a nested list, any displays it contains must be indented
12085 . ==== as otherwise they are too far to the left.
12086 .code
12087 helo_lookup_domains = @ : @[]
12088 .endd
12089 which causes a lookup if a remote host (incorrectly) gives the server's name or
12090 IP address in an EHLO or HELO command.
12091 .endlist
12092
12093
12094 .vitem &$sender_host_port$&
12095 .vindex "&$sender_host_port$&"
12096 When a message is received from a remote host, this variable contains the port
12097 number that was used on the remote host.
12098
12099 .vitem &$sender_ident$&
12100 .vindex "&$sender_ident$&"
12101 When a message is received from a remote host, this variable contains the
12102 identification received in response to an RFC 1413 request. When a message has
12103 been received locally, this variable contains the login name of the user that
12104 called Exim.
12105
12106 .vitem &$sender_rate_$&&'xxx'&
12107 A number of variables whose names begin &$sender_rate_$& are set as part of the
12108 &%ratelimit%& ACL condition. Details are given in section
12109 &<<SECTratelimiting>>&.
12110
12111 .vitem &$sender_rcvhost$&
12112 .cindex "DNS" "reverse lookup"
12113 .cindex "reverse DNS lookup"
12114 .vindex "&$sender_rcvhost$&"
12115 This is provided specifically for use in &'Received:'& headers. It starts with
12116 either the verified host name (as obtained from a reverse DNS lookup) or, if
12117 there is no verified host name, the IP address in square brackets. After that
12118 there may be text in parentheses. When the first item is a verified host name,
12119 the first thing in the parentheses is the IP address in square brackets,
12120 followed by a colon and a port number if port logging is enabled. When the
12121 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
12122 the parentheses.
12123
12124 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
12125 was used and its argument was not identical to the real host name or IP
12126 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
12127 all three items are present in the parentheses, a newline and tab are inserted
12128 into the string, to improve the formatting of the &'Received:'& header.
12129
12130 .vitem &$sender_verify_failure$&
12131 .vindex "&$sender_verify_failure$&"
12132 In an ACL, when a sender verification fails, this variable contains information
12133 about the failure. The details are the same as for
12134 &$recipient_verify_failure$&.
12135
12136 .vitem &$sending_ip_address$&
12137 .vindex "&$sending_ip_address$&"
12138 This variable is set whenever an outgoing SMTP connection to another host has
12139 been set up. It contains the IP address of the local interface that is being
12140 used. This is useful if a host that has more than one IP address wants to take
12141 on different personalities depending on which one is being used. For incoming
12142 connections, see &$received_ip_address$&.
12143
12144 .vitem &$sending_port$&
12145 .vindex "&$sending_port$&"
12146 This variable is set whenever an outgoing SMTP connection to another host has
12147 been set up. It contains the local port that is being used. For incoming
12148 connections, see &$received_port$&.
12149
12150 .vitem &$smtp_active_hostname$&
12151 .vindex "&$smtp_active_hostname$&"
12152 During an incoming SMTP session, this variable contains the value of the active
12153 host name, as specified by the &%smtp_active_hostname%& option. The value of
12154 &$smtp_active_hostname$& is saved with any message that is received, so its
12155 value can be consulted during routing and delivery.
12156
12157 .vitem &$smtp_command$&
12158 .vindex "&$smtp_command$&"
12159 During the processing of an incoming SMTP command, this variable contains the
12160 entire command. This makes it possible to distinguish between HELO and EHLO in
12161 the HELO ACL, and also to distinguish between commands such as these:
12162 .code
12163 MAIL FROM:<>
12164 MAIL FROM: <>
12165 .endd
12166 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
12167 command, the address in &$smtp_command$& is the original address before any
12168 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
12169 the address after SMTP-time rewriting.
12170
12171 .vitem &$smtp_command_argument$&
12172 .cindex "SMTP" "command, argument for"
12173 .vindex "&$smtp_command_argument$&"
12174 While an ACL is running to check an SMTP command, this variable contains the
12175 argument, that is, the text that follows the command name, with leading white
12176 space removed. Following the introduction of &$smtp_command$&, this variable is
12177 somewhat redundant, but is retained for backwards compatibility.
12178
12179 .vitem &$smtp_count_at_connection_start$&
12180 .vindex "&$smtp_count_at_connection_start$&"
12181 This variable is set greater than zero only in processes spawned by the Exim
12182 daemon for handling incoming SMTP connections. The name is deliberately long,
12183 in order to emphasize what the contents are. When the daemon accepts a new
12184 connection, it increments this variable. A copy of the variable is passed to
12185 the child process that handles the connection, but its value is fixed, and
12186 never changes. It is only an approximation of how many incoming connections
12187 there actually are, because many other connections may come and go while a
12188 single connection is being processed. When a child process terminates, the
12189 daemon decrements its copy of the variable.
12190
12191 .vitem "&$sn0$& &-- &$sn9$&"
12192 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
12193 that were current at the end of the system filter file. This allows a system
12194 filter file to set values that can be tested in users' filter files. For
12195 example, a system filter could set a value indicating how likely it is that a
12196 message is junk mail.
12197
12198 .vitem &$spam_$&&'xxx'&
12199 A number of variables whose names start with &$spam$& are available when Exim
12200 is compiled with the content-scanning extension. For details, see section
12201 &<<SECTscanspamass>>&.
12202
12203
12204 .vitem &$spool_directory$&
12205 .vindex "&$spool_directory$&"
12206 The name of Exim's spool directory.
12207
12208 .vitem &$spool_inodes$&
12209 .vindex "&$spool_inodes$&"
12210 The number of free inodes in the disk partition where Exim's spool files are
12211 being written. The value is recalculated whenever the variable is referenced.
12212 If the relevant file system does not have the concept of inodes, the value of
12213 is -1. See also the &%check_spool_inodes%& option.
12214
12215 .vitem &$spool_space$&
12216 .vindex "&$spool_space$&"
12217 The amount of free space (as a number of kilobytes) in the disk partition where
12218 Exim's spool files are being written. The value is recalculated whenever the
12219 variable is referenced. If the operating system does not have the ability to
12220 find the amount of free space (only true for experimental systems), the space
12221 value is -1. For example, to check in an ACL that there is at least 50
12222 megabytes free on the spool, you could write:
12223 .code
12224 condition = ${if > {$spool_space}{50000}}
12225 .endd
12226 See also the &%check_spool_space%& option.
12227
12228
12229 .vitem &$thisaddress$&
12230 .vindex "&$thisaddress$&"
12231 This variable is set only during the processing of the &%foranyaddress%&
12232 command in a filter file. Its use is explained in the description of that
12233 command, which can be found in the separate document entitled &'Exim's
12234 interfaces to mail filtering'&.
12235
12236 .vitem &$tls_in_bits$&
12237 .vindex "&$tls_in_bits$&"
12238 Contains an approximation of the TLS cipher's bit-strength
12239 on the inbound connection; the meaning of
12240 this depends upon the TLS implementation used.
12241 If TLS has not been negotiated, the value will be 0.
12242 The value of this is automatically fed into the Cyrus SASL authenticator
12243 when acting as a server, to specify the "external SSF" (a SASL term).
12244
12245 The deprecated &$tls_bits$& variable refers to the inbound side
12246 except when used in the context of an outbound SMTP delivery, when it refers to
12247 the outbound.
12248
12249 .vitem &$tls_out_bits$&
12250 .vindex "&$tls_out_bits$&"
12251 Contains an approximation of the TLS cipher's bit-strength
12252 on an outbound SMTP connection; the meaning of
12253 this depends upon the TLS implementation used.
12254 If TLS has not been negotiated, the value will be 0.
12255
12256 .vitem &$tls_in_certificate_verified$&
12257 .vindex "&$tls_in_certificate_verified$&"
12258 This variable is set to &"1"& if a TLS certificate was verified when the
12259 message was received, and &"0"& otherwise.
12260
12261 The deprecated &$tls_certificate_verfied$& variable refers to the inbound side
12262 except when used in the context of an outbound SMTP delivery, when it refers to
12263 the outbound.
12264
12265 .vitem &$tls_out_certificate_verified$&
12266 .vindex "&$tls_out_certificate_verified$&"
12267 This variable is set to &"1"& if a TLS certificate was verified when an
12268 outbound SMTP connection was made,
12269 and &"0"& otherwise.
12270
12271 .vitem &$tls_in_cipher$&
12272 .vindex "&$tls_in_cipher$&"
12273 .vindex "&$tls_cipher$&"
12274 When a message is received from a remote host over an encrypted SMTP
12275 connection, this variable is set to the cipher suite that was negotiated, for
12276 example DES-CBC3-SHA. In other circumstances, in particular, for message
12277 received over unencrypted connections, the variable is empty. Testing
12278 &$tls_cipher$& for emptiness is one way of distinguishing between encrypted and
12279 non-encrypted connections during ACL processing.
12280
12281 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
12282 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
12283 becomes the same as &$tls_out_cipher$&.
12284
12285 .vitem &$tls_out_cipher$&
12286 .vindex "&$tls_out_cipher$&"
12287 This variable is
12288 cleared before any outgoing SMTP connection is made,
12289 and then set to the outgoing cipher suite if one is negotiated. See chapter
12290 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
12291 details of the &(smtp)& transport.
12292
12293 .vitem &$tls_in_peerdn$&
12294 .vindex "&$tls_in_peerdn$&"
12295 .vindex "&$tls_peerdn$&"
12296 When a message is received from a remote host over an encrypted SMTP
12297 connection, and Exim is configured to request a certificate from the client,
12298 the value of the Distinguished Name of the certificate is made available in the
12299 &$tls_in_peerdn$& during subsequent processing.
12300
12301 The deprecated &$tls_peerdn$& variable refers to the inbound side
12302 except when used in the context of an outbound SMTP delivery, when it refers to
12303 the outbound.
12304
12305 .vitem &$tls_out_peerdn$&
12306 .vindex "&$tls_out_peerdn$&"
12307 When a message is being delivered to a remote host over an encrypted SMTP
12308 connection, and Exim is configured to request a certificate from the server,
12309 the value of the Distinguished Name of the certificate is made available in the
12310 &$tls_out_peerdn$& during subsequent processing.
12311
12312 .vitem &$tls_in_sni$&
12313 .vindex "&$tls_in_sni$&"
12314 .vindex "&$tls_sni$&"
12315 .cindex "TLS" "Server Name Indication"
12316 When a TLS session is being established, if the client sends the Server
12317 Name Indication extension, the value will be placed in this variable.
12318 If the variable appears in &%tls_certificate%& then this option and
12319 some others, described in &<<SECTtlssni>>&,
12320 will be re-expanded early in the TLS session, to permit
12321 a different certificate to be presented (and optionally a different key to be
12322 used) to the client, based upon the value of the SNI extension.
12323
12324 The deprecated &$tls_sni$& variable refers to the inbound side
12325 except when used in the context of an outbound SMTP delivery, when it refers to
12326 the outbound.
12327
12328 .vitem &$tls_out_sni$&
12329 .vindex "&$tls_out_sni$&"
12330 .cindex "TLS" "Server Name Indication"
12331 During outbound
12332 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
12333 the transport.
12334
12335 .vitem &$tod_bsdinbox$&
12336 .vindex "&$tod_bsdinbox$&"
12337 The time of day and the date, in the format required for BSD-style mailbox
12338 files, for example: Thu Oct 17 17:14:09 1995.
12339
12340 .vitem &$tod_epoch$&
12341 .vindex "&$tod_epoch$&"
12342 The time and date as a number of seconds since the start of the Unix epoch.
12343
12344 .vitem &$tod_epoch_l$&
12345 .vindex "&$tod_epoch_l$&"
12346 The time and date as a number of microseconds since the start of the Unix epoch.
12347
12348 .vitem &$tod_full$&
12349 .vindex "&$tod_full$&"
12350 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
12351 +0100. The timezone is always given as a numerical offset from UTC, with
12352 positive values used for timezones that are ahead (east) of UTC, and negative
12353 values for those that are behind (west).
12354
12355 .vitem &$tod_log$&
12356 .vindex "&$tod_log$&"
12357 The time and date in the format used for writing Exim's log files, for example:
12358 1995-10-12 15:32:29, but without a timezone.
12359
12360 .vitem &$tod_logfile$&
12361 .vindex "&$tod_logfile$&"
12362 This variable contains the date in the format yyyymmdd. This is the format that
12363 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
12364 flag.
12365
12366 .vitem &$tod_zone$&
12367 .vindex "&$tod_zone$&"
12368 This variable contains the numerical value of the local timezone, for example:
12369 -0500.
12370
12371 .vitem &$tod_zulu$&
12372 .vindex "&$tod_zulu$&"
12373 This variable contains the UTC date and time in &"Zulu"& format, as specified
12374 by ISO 8601, for example: 20030221154023Z.
12375
12376 .vitem &$transport_name$&
12377 .cindex "transport" "name"
12378 .cindex "name" "of transport"
12379 .vindex "&$transport_name$&"
12380 During the running of a transport, this variable contains its name.
12381
12382 .vitem &$value$&
12383 .vindex "&$value$&"
12384 This variable contains the result of an expansion lookup, extraction operation,
12385 or external command, as described above. It is also used during a
12386 &*reduce*& expansion.
12387
12388 .vitem &$version_number$&
12389 .vindex "&$version_number$&"
12390 The version number of Exim.
12391
12392 .vitem &$warn_message_delay$&
12393 .vindex "&$warn_message_delay$&"
12394 This variable is set only during the creation of a message warning about a
12395 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
12396
12397 .vitem &$warn_message_recipients$&
12398 .vindex "&$warn_message_recipients$&"
12399 This variable is set only during the creation of a message warning about a
12400 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
12401 .endlist
12402 .ecindex IIDstrexp
12403
12404
12405
12406 . ////////////////////////////////////////////////////////////////////////////
12407 . ////////////////////////////////////////////////////////////////////////////
12408
12409 .chapter "Embedded Perl" "CHAPperl"
12410 .scindex IIDperl "Perl" "calling from Exim"
12411 Exim can be built to include an embedded Perl interpreter. When this is done,
12412 Perl subroutines can be called as part of the string expansion process. To make
12413 use of the Perl support, you need version 5.004 or later of Perl installed on
12414 your system. To include the embedded interpreter in the Exim binary, include
12415 the line
12416 .code
12417 EXIM_PERL = perl.o
12418 .endd
12419 in your &_Local/Makefile_& and then build Exim in the normal way.
12420
12421
12422 .section "Setting up so Perl can be used" "SECID85"
12423 .oindex "&%perl_startup%&"
12424 Access to Perl subroutines is via a global configuration option called
12425 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
12426 no &%perl_startup%& option in the Exim configuration file then no Perl
12427 interpreter is started and there is almost no overhead for Exim (since none of
12428 the Perl library will be paged in unless used). If there is a &%perl_startup%&
12429 option then the associated value is taken to be Perl code which is executed in
12430 a newly created Perl interpreter.
12431
12432 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
12433 need backslashes before any characters to escape special meanings. The option
12434 should usually be something like
12435 .code
12436 perl_startup = do '/etc/exim.pl'
12437 .endd
12438 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
12439 use from Exim. Exim can be configured either to start up a Perl interpreter as
12440 soon as it is entered, or to wait until the first time it is needed. Starting
12441 the interpreter at the beginning ensures that it is done while Exim still has
12442 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
12443 fact used in a particular run. Also, note that this does not mean that Exim is
12444 necessarily running as root when Perl is called at a later time. By default,
12445 the interpreter is started only when it is needed, but this can be changed in
12446 two ways:
12447
12448 .ilist
12449 .oindex "&%perl_at_start%&"
12450 Setting &%perl_at_start%& (a boolean option) in the configuration requests
12451 a startup when Exim is entered.
12452 .next
12453 The command line option &%-ps%& also requests a startup when Exim is entered,
12454 overriding the setting of &%perl_at_start%&.
12455 .endlist
12456
12457 There is also a command line option &%-pd%& (for delay) which suppresses the
12458 initial startup, even if &%perl_at_start%& is set.
12459
12460
12461 .section "Calling Perl subroutines" "SECID86"
12462 When the configuration file includes a &%perl_startup%& option you can make use
12463 of the string expansion item to call the Perl subroutines that are defined
12464 by the &%perl_startup%& code. The operator is used in any of the following
12465 forms:
12466 .code
12467 ${perl{foo}}
12468 ${perl{foo}{argument}}
12469 ${perl{foo}{argument1}{argument2} ... }
12470 .endd
12471 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
12472 arguments may be passed. Passing more than this results in an expansion failure
12473 with an error message of the form
12474 .code
12475 Too many arguments passed to Perl subroutine "foo" (max is 8)
12476 .endd
12477 The return value of the Perl subroutine is evaluated in a scalar context before
12478 it is passed back to Exim to be inserted into the expanded string. If the
12479 return value is &'undef'&, the expansion is forced to fail in the same way as
12480 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
12481 by obeying Perl's &%die%& function, the expansion fails with the error message
12482 that was passed to &%die%&.
12483
12484
12485 .section "Calling Exim functions from Perl" "SECID87"
12486 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
12487 is available to call back into Exim's string expansion function. For example,
12488 the Perl code
12489 .code
12490 my $lp = Exim::expand_string('$local_part');
12491 .endd
12492 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
12493 Note those are single quotes and not double quotes to protect against
12494 &$local_part$& being interpolated as a Perl variable.
12495
12496 If the string expansion is forced to fail by a &"fail"& item, the result of
12497 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
12498 expansion string, the Perl call from the original expansion string fails with
12499 an appropriate error message, in the same way as if &%die%& were used.
12500
12501 .cindex "debugging" "from embedded Perl"
12502 .cindex "log" "writing from embedded Perl"
12503 Two other Exim functions are available for use from within Perl code.
12504 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
12505 debugging is enabled. If you want a newline at the end, you must supply it.
12506 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
12507 timestamp. In this case, you should not supply a terminating newline.
12508
12509
12510 .section "Use of standard output and error by Perl" "SECID88"
12511 .cindex "Perl" "standard output and error"
12512 You should not write to the standard error or output streams from within your
12513 Perl code, as it is not defined how these are set up. In versions of Exim
12514 before 4.50, it is possible for the standard output or error to refer to the
12515 SMTP connection during message reception via the daemon. Writing to this stream
12516 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
12517 error streams are connected to &_/dev/null_& in the daemon. The chaos is
12518 avoided, but the output is lost.
12519
12520 .cindex "Perl" "use of &%warn%&"
12521 The Perl &%warn%& statement writes to the standard error stream by default.
12522 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
12523 you have no control. When Exim starts up the Perl interpreter, it arranges for
12524 output from the &%warn%& statement to be written to the Exim main log. You can
12525 change this by including appropriate Perl magic somewhere in your Perl code.
12526 For example, to discard &%warn%& output completely, you need this:
12527 .code
12528 $SIG{__WARN__} = sub { };
12529 .endd
12530 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
12531 example, the code for the subroutine is empty, so it does nothing, but you can
12532 include any Perl code that you like. The text of the &%warn%& message is passed
12533 as the first subroutine argument.
12534 .ecindex IIDperl
12535
12536
12537 . ////////////////////////////////////////////////////////////////////////////
12538 . ////////////////////////////////////////////////////////////////////////////
12539
12540 .chapter "Starting the daemon and the use of network interfaces" &&&
12541 "CHAPinterfaces" &&&
12542 "Starting the daemon"
12543 .cindex "daemon" "starting"
12544 .cindex "interface" "listening"
12545 .cindex "network interface"
12546 .cindex "interface" "network"
12547 .cindex "IP address" "for listening"
12548 .cindex "daemon" "listening IP addresses"
12549 .cindex "TCP/IP" "setting listening interfaces"
12550 .cindex "TCP/IP" "setting listening ports"
12551 A host that is connected to a TCP/IP network may have one or more physical
12552 hardware network interfaces. Each of these interfaces may be configured as one
12553 or more &"logical"& interfaces, which are the entities that a program actually
12554 works with. Each of these logical interfaces is associated with an IP address.
12555 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
12556 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
12557 knowledge about the host's interfaces for use in three different circumstances:
12558
12559 .olist
12560 When a listening daemon is started, Exim needs to know which interfaces
12561 and ports to listen on.
12562 .next
12563 When Exim is routing an address, it needs to know which IP addresses
12564 are associated with local interfaces. This is required for the correct
12565 processing of MX lists by removing the local host and others with the
12566 same or higher priority values. Also, Exim needs to detect cases
12567 when an address is routed to an IP address that in fact belongs to the
12568 local host. Unless the &%self%& router option or the &%allow_localhost%&
12569 option of the smtp transport is set (as appropriate), this is treated
12570 as an error situation.
12571 .next
12572 When Exim connects to a remote host, it may need to know which interface to use
12573 for the outgoing connection.
12574 .endlist
12575
12576
12577 Exim's default behaviour is likely to be appropriate in the vast majority
12578 of cases. If your host has only one interface, and you want all its IP
12579 addresses to be treated in the same way, and you are using only the
12580 standard SMTP port, you should not need to take any special action. The
12581 rest of this chapter does not apply to you.
12582
12583 In a more complicated situation you may want to listen only on certain
12584 interfaces, or on different ports, and for this reason there are a number of
12585 options that can be used to influence Exim's behaviour. The rest of this
12586 chapter describes how they operate.
12587
12588 When a message is received over TCP/IP, the interface and port that were
12589 actually used are set in &$received_ip_address$& and &$received_port$&.
12590
12591
12592
12593 .section "Starting a listening daemon" "SECID89"
12594 When a listening daemon is started (by means of the &%-bd%& command line
12595 option), the interfaces and ports on which it listens are controlled by the
12596 following options:
12597
12598 .ilist
12599 &%daemon_smtp_ports%& contains a list of default ports. (For backward
12600 compatibility, this option can also be specified in the singular.)
12601 .next
12602 &%local_interfaces%& contains list of interface IP addresses on which to
12603 listen. Each item may optionally also specify a port.
12604 .endlist
12605
12606 The default list separator in both cases is a colon, but this can be changed as
12607 described in section &<<SECTlistconstruct>>&. When IPv6 addresses are involved,
12608 it is usually best to change the separator to avoid having to double all the
12609 colons. For example:
12610 .code
12611 local_interfaces = <; 127.0.0.1 ; \
12612 192.168.23.65 ; \
12613 ::1 ; \
12614 3ffe:ffff:836f::fe86:a061
12615 .endd
12616 There are two different formats for specifying a port along with an IP address
12617 in &%local_interfaces%&:
12618
12619 .olist
12620 The port is added onto the address with a dot separator. For example, to listen
12621 on port 1234 on two different IP addresses:
12622 .code
12623 local_interfaces = <; 192.168.23.65.1234 ; \
12624 3ffe:ffff:836f::fe86:a061.1234
12625 .endd
12626 .next
12627 The IP address is enclosed in square brackets, and the port is added
12628 with a colon separator, for example:
12629 .code
12630 local_interfaces = <; [192.168.23.65]:1234 ; \
12631 [3ffe:ffff:836f::fe86:a061]:1234
12632 .endd
12633 .endlist
12634
12635 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
12636 default setting contains just one port:
12637 .code
12638 daemon_smtp_ports = smtp
12639 .endd
12640 If more than one port is listed, each interface that does not have its own port
12641 specified listens on all of them. Ports that are listed in
12642 &%daemon_smtp_ports%& can be identified either by name (defined in
12643 &_/etc/services_&) or by number. However, when ports are given with individual
12644 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
12645
12646
12647
12648 .section "Special IP listening addresses" "SECID90"
12649 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
12650 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
12651 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
12652 instead of setting up separate listening sockets for each interface. The
12653 default value of &%local_interfaces%& is
12654 .code
12655 local_interfaces = 0.0.0.0
12656 .endd
12657 when Exim is built without IPv6 support; otherwise it is:
12658 .code
12659 local_interfaces = <; ::0 ; 0.0.0.0
12660 .endd
12661 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
12662
12663
12664
12665 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
12666 The &%-oX%& command line option can be used to override the values of
12667 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
12668 instance. Another way of doing this would be to use macros and the &%-D%&
12669 option. However, &%-oX%& can be used by any admin user, whereas modification of
12670 the runtime configuration by &%-D%& is allowed only when the caller is root or
12671 exim.
12672
12673 The value of &%-oX%& is a list of items. The default colon separator can be
12674 changed in the usual way if required. If there are any items that do not
12675 contain dots or colons (that is, are not IP addresses), the value of
12676 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
12677 items that do contain dots or colons, the value of &%local_interfaces%& is
12678 replaced by those items. Thus, for example,
12679 .code
12680 -oX 1225
12681 .endd
12682 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
12683 whereas
12684 .code
12685 -oX 192.168.34.5.1125
12686 .endd
12687 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
12688 (However, since &%local_interfaces%& now contains no items without ports, the
12689 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
12690
12691
12692
12693 .section "Support for the obsolete SSMTP (or SMTPS) protocol" "SECTsupobssmt"
12694 .cindex "ssmtp protocol"
12695 .cindex "smtps protocol"
12696 .cindex "SMTP" "ssmtp protocol"
12697 .cindex "SMTP" "smtps protocol"
12698 Exim supports the obsolete SSMTP protocol (also known as SMTPS) that was used
12699 before the STARTTLS command was standardized for SMTP. Some legacy clients
12700 still use this protocol. If the &%tls_on_connect_ports%& option is set to a
12701 list of port numbers, connections to those ports must use SSMTP. The most
12702 common use of this option is expected to be
12703 .code
12704 tls_on_connect_ports = 465
12705 .endd
12706 because 465 is the usual port number used by the legacy clients. There is also
12707 a command line option &%-tls-on-connect%&, which forces all ports to behave in
12708 this way when a daemon is started.
12709
12710 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
12711 daemon to listen on those ports. You must still specify them in
12712 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
12713 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
12714 connections via the daemon.)
12715
12716
12717
12718
12719 .section "IPv6 address scopes" "SECID92"
12720 .cindex "IPv6" "address scopes"
12721 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
12722 can, in principle, have the same link-local IPv6 address on different
12723 interfaces. Thus, additional information is needed, over and above the IP
12724 address, to distinguish individual interfaces. A convention of using a
12725 percent sign followed by something (often the interface name) has been
12726 adopted in some cases, leading to addresses like this:
12727 .code
12728 fe80::202:b3ff:fe03:45c1%eth0
12729 .endd
12730 To accommodate this usage, a percent sign followed by an arbitrary string is
12731 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
12732 to convert a textual IPv6 address for actual use. This function recognizes the
12733 percent convention in operating systems that support it, and it processes the
12734 address appropriately. Unfortunately, some older libraries have problems with
12735 &[getaddrinfo()]&. If
12736 .code
12737 IPV6_USE_INET_PTON=yes
12738 .endd
12739 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
12740 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
12741 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
12742 function.) Of course, this means that the additional functionality of
12743 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
12744
12745 .section "Disabling IPv6" "SECID93"
12746 .cindex "IPv6" "disabling"
12747 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
12748 run on a host whose kernel does not support IPv6. The binary will fall back to
12749 using IPv4, but it may waste resources looking up AAAA records, and trying to
12750 connect to IPv6 addresses, causing delays to mail delivery. If you set the
12751 .oindex "&%disable_ipv6%&"
12752 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
12753 activities take place. AAAA records are never looked up, and any IPv6 addresses
12754 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
12755 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
12756 to handle IPv6 literal addresses.
12757
12758 On the other hand, when IPv6 is in use, there may be times when you want to
12759 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
12760 option to globally suppress the lookup of AAAA records for specified domains,
12761 and you can use the &%ignore_target_hosts%& generic router option to ignore
12762 IPv6 addresses in an individual router.
12763
12764
12765
12766 .section "Examples of starting a listening daemon" "SECID94"
12767 The default case in an IPv6 environment is
12768 .code
12769 daemon_smtp_ports = smtp
12770 local_interfaces = <; ::0 ; 0.0.0.0
12771 .endd
12772 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
12773 Either one or two sockets may be used, depending on the characteristics of
12774 the TCP/IP stack. (This is complicated and messy; for more information,
12775 read the comments in the &_daemon.c_& source file.)
12776
12777 To specify listening on ports 25 and 26 on all interfaces:
12778 .code
12779 daemon_smtp_ports = 25 : 26
12780 .endd
12781 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
12782 .code
12783 local_interfaces = <; ::0.25 ; ::0.26 \
12784 0.0.0.0.25 ; 0.0.0.0.26
12785 .endd
12786 To listen on the default port on all IPv4 interfaces, and on port 26 on the
12787 IPv4 loopback address only:
12788 .code
12789 local_interfaces = 0.0.0.0 : 127.0.0.1.26
12790 .endd
12791 To specify listening on the default port on specific interfaces only:
12792 .code
12793 local_interfaces = 10.0.0.67 : 192.168.34.67
12794 .endd
12795 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
12796
12797
12798
12799 .section "Recognizing the local host" "SECTreclocipadd"
12800 The &%local_interfaces%& option is also used when Exim needs to determine
12801 whether or not an IP address refers to the local host. That is, the IP
12802 addresses of all the interfaces on which a daemon is listening are always
12803 treated as local.
12804
12805 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
12806 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
12807 available interfaces from the operating system, and extracts the relevant
12808 (that is, IPv4 or IPv6) addresses to use for checking.
12809
12810 Some systems set up large numbers of virtual interfaces in order to provide
12811 many virtual web servers. In this situation, you may want to listen for
12812 email on only a few of the available interfaces, but nevertheless treat all
12813 interfaces as local when routing. You can do this by setting
12814 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
12815 &"all"& wildcard values. These addresses are recognized as local, but are not
12816 used for listening. Consider this example:
12817 .code
12818 local_interfaces = <; 127.0.0.1 ; ::1 ; \
12819 192.168.53.235 ; \
12820 3ffe:2101:12:1:a00:20ff:fe86:a061
12821
12822 extra_local_interfaces = <; ::0 ; 0.0.0.0
12823 .endd
12824 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
12825 address, but all available interface addresses are treated as local when
12826 Exim is routing.
12827
12828 In some environments the local host name may be in an MX list, but with an IP
12829 address that is not assigned to any local interface. In other cases it may be
12830 desirable to treat other host names as if they referred to the local host. Both
12831 these cases can be handled by setting the &%hosts_treat_as_local%& option.
12832 This contains host names rather than IP addresses. When a host is referenced
12833 during routing, either via an MX record or directly, it is treated as the local
12834 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
12835 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
12836
12837
12838
12839 .section "Delivering to a remote host" "SECID95"
12840 Delivery to a remote host is handled by the smtp transport. By default, it
12841 allows the system's TCP/IP functions to choose which interface to use (if
12842 there is more than one) when connecting to a remote host. However, the
12843 &%interface%& option can be set to specify which interface is used. See the
12844 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
12845 details.
12846
12847
12848
12849
12850 . ////////////////////////////////////////////////////////////////////////////
12851 . ////////////////////////////////////////////////////////////////////////////
12852
12853 .chapter "Main configuration" "CHAPmainconfig"
12854 .scindex IIDconfima "configuration file" "main section"
12855 .scindex IIDmaiconf "main configuration"
12856 The first part of the run time configuration file contains three types of item:
12857
12858 .ilist
12859 Macro definitions: These lines start with an upper case letter. See section
12860 &<<SECTmacrodefs>>& for details of macro processing.
12861 .next
12862 Named list definitions: These lines start with one of the words &"domainlist"&,
12863 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
12864 section &<<SECTnamedlists>>&.
12865 .next
12866 Main configuration settings: Each setting occupies one line of the file
12867 (with possible continuations). If any setting is preceded by the word
12868 &"hide"&, the &%-bP%& command line option displays its value to admin users
12869 only. See section &<<SECTcos>>& for a description of the syntax of these option
12870 settings.
12871 .endlist
12872
12873 This chapter specifies all the main configuration options, along with their
12874 types and default values. For ease of finding a particular option, they appear
12875 in alphabetical order in section &<<SECTalomo>>& below. However, because there
12876 are now so many options, they are first listed briefly in functional groups, as
12877 an aid to finding the name of the option you are looking for. Some options are
12878 listed in more than one group.
12879
12880 .section "Miscellaneous" "SECID96"
12881 .table2
12882 .row &%bi_command%& "to run for &%-bi%& command line option"
12883 .row &%disable_ipv6%& "do no IPv6 processing"
12884 .row &%keep_malformed%& "for broken files &-- should not happen"
12885 .row &%localhost_number%& "for unique message ids in clusters"
12886 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
12887 .row &%message_body_visible%& "how much to show in &$message_body$&"
12888 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
12889 .row &%print_topbitchars%& "top-bit characters are printing"
12890 .row &%timezone%& "force time zone"
12891 .endtable
12892
12893
12894 .section "Exim parameters" "SECID97"
12895 .table2
12896 .row &%exim_group%& "override compiled-in value"
12897 .row &%exim_path%& "override compiled-in value"
12898 .row &%exim_user%& "override compiled-in value"
12899 .row &%primary_hostname%& "default from &[uname()]&"
12900 .row &%split_spool_directory%& "use multiple directories"
12901 .row &%spool_directory%& "override compiled-in value"
12902 .endtable
12903
12904
12905
12906 .section "Privilege controls" "SECID98"
12907 .table2
12908 .row &%admin_groups%& "groups that are Exim admin users"
12909 .row &%deliver_drop_privilege%& "drop root for delivery processes"
12910 .row &%local_from_check%& "insert &'Sender:'& if necessary"
12911 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
12912 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
12913 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
12914 .row &%never_users%& "do not run deliveries as these"
12915 .row &%prod_requires_admin%& "forced delivery requires admin user"
12916 .row &%queue_list_requires_admin%& "queue listing requires admin user"
12917 .row &%trusted_groups%& "groups that are trusted"
12918 .row &%trusted_users%& "users that are trusted"
12919 .endtable
12920
12921
12922
12923 .section "Logging" "SECID99"
12924 .table2
12925 .row &%hosts_connection_nolog%& "exemption from connect logging"
12926 .row &%log_file_path%& "override compiled-in value"
12927 .row &%log_selector%& "set/unset optional logging"
12928 .row &%log_timezone%& "add timezone to log lines"
12929 .row &%message_logs%& "create per-message logs"
12930 .row &%preserve_message_logs%& "after message completion"
12931 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
12932 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
12933 .row &%syslog_facility%& "set syslog &""facility""& field"
12934 .row &%syslog_processname%& "set syslog &""ident""& field"
12935 .row &%syslog_timestamp%& "timestamp syslog lines"
12936 .row &%write_rejectlog%& "control use of message log"
12937 .endtable
12938
12939
12940
12941 .section "Frozen messages" "SECID100"
12942 .table2
12943 .row &%auto_thaw%& "sets time for retrying frozen messages"
12944 .row &%freeze_tell%& "send message when freezing"
12945 .row &%move_frozen_messages%& "to another directory"
12946 .row &%timeout_frozen_after%& "keep frozen messages only so long"
12947 .endtable
12948
12949
12950
12951 .section "Data lookups" "SECID101"
12952 .table2
12953 .row &%ibase_servers%& "InterBase servers"
12954 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
12955 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
12956 .row &%ldap_cert_file%& "client cert file for LDAP"
12957 .row &%ldap_cert_key%& "client key file for LDAP"
12958 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
12959 .row &%ldap_default_servers%& "used if no server in query"
12960 .row &%ldap_require_cert%& "action to take without LDAP server cert"
12961 .row &%ldap_start_tls%& "require TLS within LDAP"
12962 .row &%ldap_version%& "set protocol version"
12963 .row &%lookup_open_max%& "lookup files held open"
12964 .row &%mysql_servers%& "default MySQL servers"
12965 .row &%oracle_servers%& "Oracle servers"
12966 .row &%pgsql_servers%& "default PostgreSQL servers"
12967 .row &%sqlite_lock_timeout%& "as it says"
12968 .endtable
12969
12970
12971
12972 .section "Message ids" "SECID102"
12973 .table2
12974 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
12975 .row &%message_id_header_text%& "ditto"
12976 .endtable
12977
12978
12979
12980 .section "Embedded Perl Startup" "SECID103"
12981 .table2
12982 .row &%perl_at_start%& "always start the interpreter"
12983 .row &%perl_startup%& "code to obey when starting Perl"
12984 .endtable
12985
12986
12987
12988 .section "Daemon" "SECID104"
12989 .table2
12990 .row &%daemon_smtp_ports%& "default ports"
12991 .row &%daemon_startup_retries%& "number of times to retry"
12992 .row &%daemon_startup_sleep%& "time to sleep between tries"
12993 .row &%extra_local_interfaces%& "not necessarily listened on"
12994 .row &%local_interfaces%& "on which to listen, with optional ports"
12995 .row &%pid_file_path%& "override compiled-in value"
12996 .row &%queue_run_max%& "maximum simultaneous queue runners"
12997 .endtable
12998
12999
13000
13001 .section "Resource control" "SECID105"
13002 .table2
13003 .row &%check_log_inodes%& "before accepting a message"
13004 .row &%check_log_space%& "before accepting a message"
13005 .row &%check_spool_inodes%& "before accepting a message"
13006 .row &%check_spool_space%& "before accepting a message"
13007 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
13008 .row &%queue_only_load%& "queue incoming if load high"
13009 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
13010 .row &%queue_run_max%& "maximum simultaneous queue runners"
13011 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
13012 .row &%smtp_accept_max%& "simultaneous incoming connections"
13013 .row &%smtp_accept_max_nonmail%& "non-mail commands"
13014 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
13015 .row &%smtp_accept_max_per_connection%& "messages per connection"
13016 .row &%smtp_accept_max_per_host%& "connections from one host"
13017 .row &%smtp_accept_queue%& "queue mail if more connections"
13018 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
13019 connection"
13020 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
13021 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
13022 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
13023 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
13024 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
13025 .endtable
13026
13027
13028
13029 .section "Policy controls" "SECID106"
13030 .table2
13031 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
13032 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
13033 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
13034 .row &%acl_smtp_auth%& "ACL for AUTH"
13035 .row &%acl_smtp_connect%& "ACL for connection"
13036 .row &%acl_smtp_data%& "ACL for DATA"
13037 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
13038 .row &%acl_smtp_etrn%& "ACL for ETRN"
13039 .row &%acl_smtp_expn%& "ACL for EXPN"
13040 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
13041 .row &%acl_smtp_mail%& "ACL for MAIL"
13042 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
13043 .row &%acl_smtp_mime%& "ACL for MIME parts"
13044 .row &%acl_smtp_predata%& "ACL for start of data"
13045 .row &%acl_smtp_quit%& "ACL for QUIT"
13046 .row &%acl_smtp_rcpt%& "ACL for RCPT"
13047 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
13048 .row &%acl_smtp_vrfy%& "ACL for VRFY"
13049 .row &%av_scanner%& "specify virus scanner"
13050 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
13051 words""&"
13052 .row &%dns_csa_search_limit%& "control CSA parent search depth"
13053 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
13054 .row &%header_maxsize%& "total size of message header"
13055 .row &%header_line_maxsize%& "individual header line limit"
13056 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
13057 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
13058 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
13059 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
13060 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
13061 .row &%host_lookup%& "host name looked up for these hosts"
13062 .row &%host_lookup_order%& "order of DNS and local name lookups"
13063 .row &%host_reject_connection%& "reject connection from these hosts"
13064 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
13065 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
13066 .row &%message_size_limit%& "for all messages"
13067 .row &%percent_hack_domains%& "recognize %-hack for these domains"
13068 .row &%spamd_address%& "set interface to SpamAssassin"
13069 .row &%strict_acl_vars%& "object to unset ACL variables"
13070 .endtable
13071
13072
13073
13074 .section "Callout cache" "SECID107"
13075 .table2
13076 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
13077 item"
13078 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
13079 item"
13080 .row &%callout_negative_expire%& "timeout for negative address cache item"
13081 .row &%callout_positive_expire%& "timeout for positive address cache item"
13082 .row &%callout_random_local_part%& "string to use for &""random""& testing"
13083 .endtable
13084
13085
13086
13087 .section "TLS" "SECID108"
13088 .table2
13089 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
13090 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
13091 .row &%openssl_options%& "adjust OpenSSL compatibility options"
13092 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
13093 .row &%tls_certificate%& "location of server certificate"
13094 .row &%tls_crl%& "certificate revocation list"
13095 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
13096 .row &%tls_dhparam%& "DH parameters for server"
13097 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
13098 .row &%tls_privatekey%& "location of server private key"
13099 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
13100 .row &%tls_require_ciphers%& "specify acceptable ciphers"
13101 .row &%tls_try_verify_hosts%& "try to verify client certificate"
13102 .row &%tls_verify_certificates%& "expected client certificates"
13103 .row &%tls_verify_hosts%& "insist on client certificate verify"
13104 .endtable
13105
13106
13107
13108 .section "Local user handling" "SECID109"
13109 .table2
13110 .row &%finduser_retries%& "useful in NIS environments"
13111 .row &%gecos_name%& "used when creating &'Sender:'&"
13112 .row &%gecos_pattern%& "ditto"
13113 .row &%max_username_length%& "for systems that truncate"
13114 .row &%unknown_login%& "used when no login name found"
13115 .row &%unknown_username%& "ditto"
13116 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
13117 .row &%uucp_from_sender%& "ditto"
13118 .endtable
13119
13120
13121
13122 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
13123 .table2
13124 .row &%header_maxsize%& "total size of message header"
13125 .row &%header_line_maxsize%& "individual header line limit"
13126 .row &%message_size_limit%& "applies to all messages"
13127 .row &%percent_hack_domains%& "recognize %-hack for these domains"
13128 .row &%received_header_text%& "expanded to make &'Received:'&"
13129 .row &%received_headers_max%& "for mail loop detection"
13130 .row &%recipients_max%& "limit per message"
13131 .row &%recipients_max_reject%& "permanently reject excess recipients"
13132 .endtable
13133
13134
13135
13136
13137 .section "Non-SMTP incoming messages" "SECID111"
13138 .table2
13139 .row &%receive_timeout%& "for non-SMTP messages"
13140 .endtable
13141
13142
13143
13144
13145
13146 .section "Incoming SMTP messages" "SECID112"
13147 See also the &'Policy controls'& section above.
13148
13149 .table2
13150 .row &%host_lookup%& "host name looked up for these hosts"
13151 .row &%host_lookup_order%& "order of DNS and local name lookups"
13152 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
13153 .row &%rfc1413_hosts%& "make ident calls to these hosts"
13154 .row &%rfc1413_query_timeout%& "zero disables ident calls"
13155 .row &%sender_unqualified_hosts%& "may send unqualified senders"
13156 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
13157 .row &%smtp_accept_max%& "simultaneous incoming connections"
13158 .row &%smtp_accept_max_nonmail%& "non-mail commands"
13159 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
13160 .row &%smtp_accept_max_per_connection%& "messages per connection"
13161 .row &%smtp_accept_max_per_host%& "connections from one host"
13162 .row &%smtp_accept_queue%& "queue mail if more connections"
13163 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
13164 connection"
13165 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
13166 .row &%smtp_active_hostname%& "host name to use in messages"
13167 .row &%smtp_banner%& "text for welcome banner"
13168 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
13169 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
13170 .row &%smtp_enforce_sync%& "of SMTP command/responses"
13171 .row &%smtp_etrn_command%& "what to run for ETRN"
13172 .row &%smtp_etrn_serialize%& "only one at once"
13173 .row &%smtp_load_reserve%& "only reserve hosts if this load"
13174 .row &%smtp_max_unknown_commands%& "before dropping connection"
13175 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
13176 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
13177 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
13178 .row &%smtp_receive_timeout%& "per command or data line"
13179 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
13180 .row &%smtp_return_error_details%& "give detail on rejections"
13181 .endtable
13182
13183
13184
13185 .section "SMTP extensions" "SECID113"
13186 .table2
13187 .row &%accept_8bitmime%& "advertise 8BITMIME"
13188 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
13189 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
13190 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
13191 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
13192 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
13193 .endtable
13194
13195
13196
13197 .section "Processing messages" "SECID114"
13198 .table2
13199 .row &%allow_domain_literals%& "recognize domain literal syntax"
13200 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
13201 .row &%allow_utf8_domains%& "in addresses"
13202 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
13203 words""&"
13204 .row &%delivery_date_remove%& "from incoming messages"
13205 .row &%envelope_to_remove%& "from incoming messages"
13206 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
13207 .row &%headers_charset%& "default for translations"
13208 .row &%qualify_domain%& "default for senders"
13209 .row &%qualify_recipient%& "default for recipients"
13210 .row &%return_path_remove%& "from incoming messages"
13211 .row &%strip_excess_angle_brackets%& "in addresses"
13212 .row &%strip_trailing_dot%& "at end of addresses"
13213 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
13214 .endtable
13215
13216
13217
13218 .section "System filter" "SECID115"
13219 .table2
13220 .row &%system_filter%& "locate system filter"
13221 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
13222 directory"
13223 .row &%system_filter_file_transport%& "transport for delivery to a file"
13224 .row &%system_filter_group%& "group for filter running"
13225 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
13226 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
13227 .row &%system_filter_user%& "user for filter running"
13228 .endtable
13229
13230
13231
13232 .section "Routing and delivery" "SECID116"
13233 .table2
13234 .row &%disable_ipv6%& "do no IPv6 processing"
13235 .row &%dns_again_means_nonexist%& "for broken domains"
13236 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
13237 .row &%dns_dnssec_ok%& "parameter for resolver"
13238 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
13239 .row &%dns_retrans%& "parameter for resolver"
13240 .row &%dns_retry%& "parameter for resolver"
13241 .row &%dns_use_edns0%& "parameter for resolver"
13242 .row &%hold_domains%& "hold delivery for these domains"
13243 .row &%local_interfaces%& "for routing checks"
13244 .row &%queue_domains%& "no immediate delivery for these"
13245 .row &%queue_only%& "no immediate delivery at all"
13246 .row &%queue_only_file%& "no immediate delivery if file exists"
13247 .row &%queue_only_load%& "no immediate delivery if load is high"
13248 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
13249 .row &%queue_only_override%& "allow command line to override"
13250 .row &%queue_run_in_order%& "order of arrival"
13251 .row &%queue_run_max%& "of simultaneous queue runners"
13252 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
13253 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
13254 .row &%remote_sort_domains%& "order of remote deliveries"
13255 .row &%retry_data_expire%& "timeout for retry data"
13256 .row &%retry_interval_max%& "safety net for retry rules"
13257 .endtable
13258
13259
13260
13261 .section "Bounce and warning messages" "SECID117"
13262 .table2
13263 .row &%bounce_message_file%& "content of bounce"
13264 .row &%bounce_message_text%& "content of bounce"
13265 .row &%bounce_return_body%& "include body if returning message"
13266 .row &%bounce_return_message%& "include original message in bounce"
13267 .row &%bounce_return_size_limit%& "limit on returned message"
13268 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
13269 .row &%dsn_from%& "set &'From:'& contents in bounces"
13270 .row &%errors_copy%& "copy bounce messages"
13271 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
13272 .row &%delay_warning%& "time schedule"
13273 .row &%delay_warning_condition%& "condition for warning messages"
13274 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
13275 .row &%smtp_return_error_details%& "give detail on rejections"
13276 .row &%warn_message_file%& "content of warning message"
13277 .endtable
13278
13279
13280
13281 .section "Alphabetical list of main options" "SECTalomo"
13282 Those options that undergo string expansion before use are marked with
13283 &dagger;.
13284
13285 .option accept_8bitmime main boolean true
13286 .cindex "8BITMIME"
13287 .cindex "8-bit characters"
13288 .cindex "log" "selectors"
13289 .cindex "log" "8BITMIME"
13290 This option causes Exim to send 8BITMIME in its response to an SMTP
13291 EHLO command, and to accept the BODY= parameter on MAIL commands.
13292 However, though Exim is 8-bit clean, it is not a protocol converter, and it
13293 takes no steps to do anything special with messages received by this route.
13294
13295 Historically Exim kept this option off by default, but the maintainers
13296 feel that in today's Internet, this causes more problems than it solves.
13297 It now defaults to true.
13298 A more detailed analysis of the issues is provided by Dan Bernstein:
13299 .display
13300 &url(http://cr.yp.to/smtp/8bitmime.html)
13301 .endd
13302
13303 To log received 8BITMIME status use
13304 .code
13305 log_selector = +8bitmime
13306 .endd
13307
13308 .option acl_not_smtp main string&!! unset
13309 .cindex "&ACL;" "for non-SMTP messages"
13310 .cindex "non-SMTP messages" "ACLs for"
13311 This option defines the ACL that is run when a non-SMTP message has been
13312 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
13313 further details.
13314
13315 .option acl_not_smtp_mime main string&!! unset
13316 This option defines the ACL that is run for individual MIME parts of non-SMTP
13317 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
13318 SMTP messages.
13319
13320 .option acl_not_smtp_start main string&!! unset
13321 .cindex "&ACL;" "at start of non-SMTP message"
13322 .cindex "non-SMTP messages" "ACLs for"
13323 This option defines the ACL that is run before Exim starts reading a
13324 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
13325
13326 .option acl_smtp_auth main string&!! unset
13327 .cindex "&ACL;" "setting up for SMTP commands"
13328 .cindex "AUTH" "ACL for"
13329 This option defines the ACL that is run when an SMTP AUTH command is
13330 received. See chapter &<<CHAPACL>>& for further details.
13331
13332 .option acl_smtp_connect main string&!! unset
13333 .cindex "&ACL;" "on SMTP connection"
13334 This option defines the ACL that is run when an SMTP connection is received.
13335 See chapter &<<CHAPACL>>& for further details.
13336
13337 .option acl_smtp_data main string&!! unset
13338 .cindex "DATA" "ACL for"
13339 This option defines the ACL that is run after an SMTP DATA command has been
13340 processed and the message itself has been received, but before the final
13341 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
13342
13343 .option acl_smtp_etrn main string&!! unset
13344 .cindex "ETRN" "ACL for"
13345 This option defines the ACL that is run when an SMTP ETRN command is
13346 received. See chapter &<<CHAPACL>>& for further details.
13347
13348 .option acl_smtp_expn main string&!! unset
13349 .cindex "EXPN" "ACL for"
13350 This option defines the ACL that is run when an SMTP EXPN command is
13351 received. See chapter &<<CHAPACL>>& for further details.
13352
13353 .option acl_smtp_helo main string&!! unset
13354 .cindex "EHLO" "ACL for"
13355 .cindex "HELO" "ACL for"
13356 This option defines the ACL that is run when an SMTP EHLO or HELO
13357 command is received. See chapter &<<CHAPACL>>& for further details.
13358
13359
13360 .option acl_smtp_mail main string&!! unset
13361 .cindex "MAIL" "ACL for"
13362 This option defines the ACL that is run when an SMTP MAIL command is
13363 received. See chapter &<<CHAPACL>>& for further details.
13364
13365 .option acl_smtp_mailauth main string&!! unset
13366 .cindex "AUTH" "on MAIL command"
13367 This option defines the ACL that is run when there is an AUTH parameter on
13368 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
13369 &<<CHAPSMTPAUTH>>& for details of authentication.
13370
13371 .option acl_smtp_mime main string&!! unset
13372 .cindex "MIME content scanning" "ACL for"
13373 This option is available when Exim is built with the content-scanning
13374 extension. It defines the ACL that is run for each MIME part in a message. See
13375 section &<<SECTscanmimepart>>& for details.
13376
13377 .option acl_smtp_predata main string&!! unset
13378 This option defines the ACL that is run when an SMTP DATA command is
13379 received, before the message itself is received. See chapter &<<CHAPACL>>& for
13380 further details.
13381
13382 .option acl_smtp_quit main string&!! unset
13383 .cindex "QUIT, ACL for"
13384 This option defines the ACL that is run when an SMTP QUIT command is
13385 received. See chapter &<<CHAPACL>>& for further details.
13386
13387 .option acl_smtp_rcpt main string&!! unset
13388 .cindex "RCPT" "ACL for"
13389 This option defines the ACL that is run when an SMTP RCPT command is
13390 received. See chapter &<<CHAPACL>>& for further details.
13391
13392 .option acl_smtp_starttls main string&!! unset
13393 .cindex "STARTTLS, ACL for"
13394 This option defines the ACL that is run when an SMTP STARTTLS command is
13395 received. See chapter &<<CHAPACL>>& for further details.
13396
13397 .option acl_smtp_vrfy main string&!! unset
13398 .cindex "VRFY" "ACL for"
13399 This option defines the ACL that is run when an SMTP VRFY command is
13400 received. See chapter &<<CHAPACL>>& for further details.
13401
13402 .option admin_groups main "string list&!!" unset
13403 .cindex "admin user"
13404 This option is expanded just once, at the start of Exim's processing. If the
13405 current group or any of the supplementary groups of an Exim caller is in this
13406 colon-separated list, the caller has admin privileges. If all your system
13407 programmers are in a specific group, for example, you can give them all Exim
13408 admin privileges by putting that group in &%admin_groups%&. However, this does
13409 not permit them to read Exim's spool files (whose group owner is the Exim gid).
13410 To permit this, you have to add individuals to the Exim group.
13411
13412 .option allow_domain_literals main boolean false
13413 .cindex "domain literal"
13414 If this option is set, the RFC 2822 domain literal format is permitted in
13415 email addresses. The option is not set by default, because the domain literal
13416 format is not normally required these days, and few people know about it. It
13417 has, however, been exploited by mail abusers.
13418
13419 Unfortunately, it seems that some DNS black list maintainers are using this
13420 format to report black listing to postmasters. If you want to accept messages
13421 addressed to your hosts by IP address, you need to set
13422 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
13423 domains (defined in the named domain list &%local_domains%& in the default
13424 configuration). This &"magic string"& matches the domain literal form of all
13425 the local host's IP addresses.
13426
13427
13428 .option allow_mx_to_ip main boolean false
13429 .cindex "MX record" "pointing to IP address"
13430 It appears that more and more DNS zone administrators are breaking the rules
13431 and putting domain names that look like IP addresses on the right hand side of
13432 MX records. Exim follows the rules and rejects this, giving an error message
13433 that explains the mis-configuration. However, some other MTAs support this
13434 practice, so to avoid &"Why can't Exim do this?"& complaints,
13435 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
13436 recommended, except when you have no other choice.
13437
13438 .option allow_utf8_domains main boolean false
13439 .cindex "domain" "UTF-8 characters in"
13440 .cindex "UTF-8" "in domain name"
13441 Lots of discussion is going on about internationalized domain names. One
13442 camp is strongly in favour of just using UTF-8 characters, and it seems
13443 that at least two other MTAs permit this. This option allows Exim users to
13444 experiment if they wish.
13445
13446 If it is set true, Exim's domain parsing function allows valid
13447 UTF-8 multicharacters to appear in domain name components, in addition to
13448 letters, digits, and hyphens. However, just setting this option is not
13449 enough; if you want to look up these domain names in the DNS, you must also
13450 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
13451 suitable setting is:
13452 .code
13453 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
13454 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
13455 .endd
13456 Alternatively, you can just disable this feature by setting
13457 .code
13458 dns_check_names_pattern =
13459 .endd
13460 That is, set the option to an empty string so that no check is done.
13461
13462
13463 .option auth_advertise_hosts main "host list&!!" *
13464 .cindex "authentication" "advertising"
13465 .cindex "AUTH" "advertising"
13466 If any server authentication mechanisms are configured, Exim advertises them in
13467 response to an EHLO command only if the calling host matches this list.
13468 Otherwise, Exim does not advertise AUTH.
13469 Exim does not accept AUTH commands from clients to which it has not
13470 advertised the availability of AUTH. The advertising of individual
13471 authentication mechanisms can be controlled by the use of the
13472 &%server_advertise_condition%& generic authenticator option on the individual
13473 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
13474
13475 Certain mail clients (for example, Netscape) require the user to provide a name
13476 and password for authentication if AUTH is advertised, even though it may
13477 not be needed (the host may accept messages from hosts on its local LAN without
13478 authentication, for example). The &%auth_advertise_hosts%& option can be used
13479 to make these clients more friendly by excluding them from the set of hosts to
13480 which Exim advertises AUTH.
13481
13482 .cindex "AUTH" "advertising when encrypted"
13483 If you want to advertise the availability of AUTH only when the connection
13484 is encrypted using TLS, you can make use of the fact that the value of this
13485 option is expanded, with a setting like this:
13486 .code
13487 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
13488 .endd
13489 .vindex "&$tls_in_cipher$&"
13490 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
13491 the expansion is empty, thus matching no hosts. Otherwise, the result of the
13492 expansion is *, which matches all hosts.
13493
13494
13495 .option auto_thaw main time 0s
13496 .cindex "thawing messages"
13497 .cindex "unfreezing messages"
13498 If this option is set to a time greater than zero, a queue runner will try a
13499 new delivery attempt on any frozen message, other than a bounce message, if
13500 this much time has passed since it was frozen. This may result in the message
13501 being re-frozen if nothing has changed since the last attempt. It is a way of
13502 saying &"keep on trying, even though there are big problems"&.
13503
13504 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
13505 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
13506 thought to be very useful any more, and its use should probably be avoided.
13507
13508
13509 .option av_scanner main string "see below"
13510 This option is available if Exim is built with the content-scanning extension.
13511 It specifies which anti-virus scanner to use. The default value is:
13512 .code
13513 sophie:/var/run/sophie
13514 .endd
13515 If the value of &%av_scanner%& starts with a dollar character, it is expanded
13516 before use. See section &<<SECTscanvirus>>& for further details.
13517
13518
13519 .option bi_command main string unset
13520 .oindex "&%-bi%&"
13521 This option supplies the name of a command that is run when Exim is called with
13522 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
13523 just the command name, it is not a complete command line. If an argument is
13524 required, it must come from the &%-oA%& command line option.
13525
13526
13527 .option bounce_message_file main string unset
13528 .cindex "bounce message" "customizing"
13529 .cindex "customizing" "bounce message"
13530 This option defines a template file containing paragraphs of text to be used
13531 for constructing bounce messages. Details of the file's contents are given in
13532 chapter &<<CHAPemsgcust>>&. See also &%warn_message_file%&.
13533
13534
13535 .option bounce_message_text main string unset
13536 When this option is set, its contents are included in the default bounce
13537 message immediately after &"This message was created automatically by mail
13538 delivery software."& It is not used if &%bounce_message_file%& is set.
13539
13540 .option bounce_return_body main boolean true
13541 .cindex "bounce message" "including body"
13542 This option controls whether the body of an incoming message is included in a
13543 bounce message when &%bounce_return_message%& is true. The default setting
13544 causes the entire message, both header and body, to be returned (subject to the
13545 value of &%bounce_return_size_limit%&). If this option is false, only the
13546 message header is included. In the case of a non-SMTP message containing an
13547 error that is detected during reception, only those header lines preceding the
13548 point at which the error was detected are returned.
13549 .cindex "bounce message" "including original"
13550
13551 .option bounce_return_message main boolean true
13552 If this option is set false, none of the original message is included in
13553 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
13554 &%bounce_return_body%&.
13555
13556
13557 .option bounce_return_size_limit main integer 100K
13558 .cindex "size" "of bounce, limit"
13559 .cindex "bounce message" "size limit"
13560 .cindex "limit" "bounce message size"
13561 This option sets a limit in bytes on the size of messages that are returned to
13562 senders as part of bounce messages when &%bounce_return_message%& is true. The
13563 limit should be less than the value of the global &%message_size_limit%& and of
13564 any &%message_size_limit%& settings on transports, to allow for the bounce text
13565 that Exim generates. If this option is set to zero there is no limit.
13566
13567 When the body of any message that is to be included in a bounce message is
13568 greater than the limit, it is truncated, and a comment pointing this out is
13569 added at the top. The actual cutoff may be greater than the value given, owing
13570 to the use of buffering for transferring the message in chunks (typically 8K in
13571 size). The idea is to save bandwidth on those undeliverable 15-megabyte
13572 messages.
13573
13574 .option bounce_sender_authentication main string unset
13575 .cindex "bounce message" "sender authentication"
13576 .cindex "authentication" "bounce message"
13577 .cindex "AUTH" "on bounce message"
13578 This option provides an authenticated sender address that is sent with any
13579 bounce messages generated by Exim that are sent over an authenticated SMTP
13580 connection. A typical setting might be:
13581 .code
13582 bounce_sender_authentication = mailer-daemon@my.domain.example
13583 .endd
13584 which would cause bounce messages to be sent using the SMTP command:
13585 .code
13586 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
13587 .endd
13588 The value of &%bounce_sender_authentication%& must always be a complete email
13589 address.
13590
13591 .option callout_domain_negative_expire main time 3h
13592 .cindex "caching" "callout timeouts"
13593 .cindex "callout" "caching timeouts"
13594 This option specifies the expiry time for negative callout cache data for a
13595 domain. See section &<<SECTcallver>>& for details of callout verification, and
13596 section &<<SECTcallvercache>>& for details of the caching.
13597
13598
13599 .option callout_domain_positive_expire main time 7d
13600 This option specifies the expiry time for positive callout cache data for a
13601 domain. See section &<<SECTcallver>>& for details of callout verification, and
13602 section &<<SECTcallvercache>>& for details of the caching.
13603
13604
13605 .option callout_negative_expire main time 2h
13606 This option specifies the expiry time for negative callout cache data for an
13607 address. See section &<<SECTcallver>>& for details of callout verification, and
13608 section &<<SECTcallvercache>>& for details of the caching.
13609
13610
13611 .option callout_positive_expire main time 24h
13612 This option specifies the expiry time for positive callout cache data for an
13613 address. See section &<<SECTcallver>>& for details of callout verification, and
13614 section &<<SECTcallvercache>>& for details of the caching.
13615
13616
13617 .option callout_random_local_part main string&!! "see below"
13618 This option defines the &"random"& local part that can be used as part of
13619 callout verification. The default value is
13620 .code
13621 $primary_hostname-$tod_epoch-testing
13622 .endd
13623 See section &<<CALLaddparcall>>& for details of how this value is used.
13624
13625
13626 .option check_log_inodes main integer 0
13627 See &%check_spool_space%& below.
13628
13629
13630 .option check_log_space main integer 0
13631 See &%check_spool_space%& below.
13632
13633 .oindex "&%check_rfc2047_length%&"
13634 .cindex "RFC 2047" "disabling length check"
13635 .option check_rfc2047_length main boolean true
13636 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
13637 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
13638 word; strings to be encoded that exceed this length are supposed to use
13639 multiple encoded words. By default, Exim does not recognize encoded words that
13640 exceed the maximum length. However, it seems that some software, in violation
13641 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
13642 set false, Exim recognizes encoded words of any length.
13643
13644
13645 .option check_spool_inodes main integer 0
13646 See &%check_spool_space%& below.
13647
13648
13649 .option check_spool_space main integer 0
13650 .cindex "checking disk space"
13651 .cindex "disk space, checking"
13652 .cindex "spool directory" "checking space"
13653 The four &%check_...%& options allow for checking of disk resources before a
13654 message is accepted.
13655
13656 .vindex "&$log_inodes$&"
13657 .vindex "&$log_space$&"
13658 .vindex "&$spool_inodes$&"
13659 .vindex "&$spool_space$&"
13660 When any of these options are set, they apply to all incoming messages. If you
13661 want to apply different checks to different kinds of message, you can do so by
13662 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
13663 &$spool_space$& in an ACL with appropriate additional conditions.
13664
13665
13666 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
13667 either value is greater than zero, for example:
13668 .code
13669 check_spool_space = 10M
13670 check_spool_inodes = 100
13671 .endd
13672 The spool partition is the one that contains the directory defined by
13673 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
13674 transit.
13675
13676 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
13677 files are written if either is greater than zero. These should be set only if
13678 &%log_file_path%& and &%spool_directory%& refer to different partitions.
13679
13680 If there is less space or fewer inodes than requested, Exim refuses to accept
13681 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
13682 error response to the MAIL command. If ESMTP is in use and there was a
13683 SIZE parameter on the MAIL command, its value is added to the
13684 &%check_spool_space%& value, and the check is performed even if
13685 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
13686
13687 The values for &%check_spool_space%& and &%check_log_space%& are held as a
13688 number of kilobytes. If a non-multiple of 1024 is specified, it is rounded up.
13689
13690 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
13691 failure a message is written to stderr and Exim exits with a non-zero code, as
13692 it obviously cannot send an error message of any kind.
13693
13694 .option daemon_smtp_ports main string &`smtp`&
13695 .cindex "port" "for daemon"
13696 .cindex "TCP/IP" "setting listening ports"
13697 This option specifies one or more default SMTP ports on which the Exim daemon
13698 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
13699 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
13700
13701 .option daemon_startup_retries main integer 9
13702 .cindex "daemon startup, retrying"
13703 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
13704 the daemon at startup when it cannot immediately bind a listening socket
13705 (typically because the socket is already in use): &%daemon_startup_retries%&
13706 defines the number of retries after the first failure, and
13707 &%daemon_startup_sleep%& defines the length of time to wait between retries.
13708
13709 .option daemon_startup_sleep main time 30s
13710 See &%daemon_startup_retries%&.
13711
13712 .option delay_warning main "time list" 24h
13713 .cindex "warning of delay"
13714 .cindex "delay warning, specifying"
13715 When a message is delayed, Exim sends a warning message to the sender at
13716 intervals specified by this option. The data is a colon-separated list of times
13717 after which to send warning messages. If the value of the option is an empty
13718 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
13719 message has been on the queue for longer than the last time, the last interval
13720 between the times is used to compute subsequent warning times. For example,
13721 with
13722 .code
13723 delay_warning = 4h:8h:24h
13724 .endd
13725 the first message is sent after 4 hours, the second after 8 hours, and
13726 the third one after 24 hours. After that, messages are sent every 16 hours,
13727 because that is the interval between the last two times on the list. If you set
13728 just one time, it specifies the repeat interval. For example, with:
13729 .code
13730 delay_warning = 6h
13731 .endd
13732 messages are repeated every six hours. To stop warnings after a given time, set
13733 a very large time at the end of the list. For example:
13734 .code
13735 delay_warning = 2h:12h:99d
13736 .endd
13737 Note that the option is only evaluated at the time a delivery attempt fails,
13738 which depends on retry and queue-runner configuration.
13739 Typically retries will be configured more frequently than warning messages.
13740
13741 .option delay_warning_condition main string&!! "see below"
13742 .vindex "&$domain$&"
13743 The string is expanded at the time a warning message might be sent. If all the
13744 deferred addresses have the same domain, it is set in &$domain$& during the
13745 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
13746 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
13747 &"false"& (the comparison being done caselessly) then the warning message is
13748 not sent. The default is:
13749 .code
13750 delay_warning_condition = ${if or {\
13751 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
13752 { match{$h_precedence:}{(?i)bulk|list|junk} }\
13753 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
13754 } {no}{yes}}
13755 .endd
13756 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
13757 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
13758 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
13759 &"auto-replied"& in an &'Auto-Submitted:'& header.
13760
13761 .option deliver_drop_privilege main boolean false
13762 .cindex "unprivileged delivery"
13763 .cindex "delivery" "unprivileged"
13764 If this option is set true, Exim drops its root privilege at the start of a
13765 delivery process, and runs as the Exim user throughout. This severely restricts
13766 the kinds of local delivery that are possible, but is viable in certain types
13767 of configuration. There is a discussion about the use of root privilege in
13768 chapter &<<CHAPsecurity>>&.
13769
13770 .option deliver_queue_load_max main fixed-point unset
13771 .cindex "load average"
13772 .cindex "queue runner" "abandoning"
13773 When this option is set, a queue run is abandoned if the system load average
13774 becomes greater than the value of the option. The option has no effect on
13775 ancient operating systems on which Exim cannot determine the load average.
13776 See also &%queue_only_load%& and &%smtp_load_reserve%&.
13777
13778
13779 .option delivery_date_remove main boolean true
13780 .cindex "&'Delivery-date:'& header line"
13781 Exim's transports have an option for adding a &'Delivery-date:'& header to a
13782 message when it is delivered, in exactly the same way as &'Return-path:'& is
13783 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
13784 should not be present in incoming messages, and this option causes them to be
13785 removed at the time the message is received, to avoid any problems that might
13786 occur when a delivered message is subsequently sent on to some other recipient.
13787
13788 .option disable_fsync main boolean false
13789 .cindex "&[fsync()]&, disabling"
13790 This option is available only if Exim was built with the compile-time option
13791 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
13792 a runtime configuration generates an &"unknown option"& error. You should not
13793 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
13794 really, really, really understand what you are doing. &'No pre-compiled
13795 distributions of Exim should ever make this option available.'&
13796
13797 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
13798 updated files' data to be written to disc before continuing. Unexpected events
13799 such as crashes and power outages may cause data to be lost or scrambled.
13800 Here be Dragons. &*Beware.*&
13801
13802
13803 .option disable_ipv6 main boolean false
13804 .cindex "IPv6" "disabling"
13805 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
13806 activities take place. AAAA records are never looked up, and any IPv6 addresses
13807 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
13808 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
13809 to handle IPv6 literal addresses.
13810
13811
13812 .option dns_again_means_nonexist main "domain list&!!" unset
13813 .cindex "DNS" "&""try again""& response; overriding"
13814 DNS lookups give a &"try again"& response for the DNS errors
13815 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
13816 keep trying to deliver a message, or to give repeated temporary errors to
13817 incoming mail. Sometimes the effect is caused by a badly set up name server and
13818 may persist for a long time. If a domain which exhibits this problem matches
13819 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
13820 This option should be used with care. You can make it apply to reverse lookups
13821 by a setting such as this:
13822 .code
13823 dns_again_means_nonexist = *.in-addr.arpa
13824 .endd
13825 This option applies to all DNS lookups that Exim does. It also applies when the
13826 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
13827 since these are most likely to be caused by DNS lookup problems. The
13828 &(dnslookup)& router has some options of its own for controlling what happens
13829 when lookups for MX or SRV records give temporary errors. These more specific
13830 options are applied after this global option.
13831
13832 .option dns_check_names_pattern main string "see below"
13833 .cindex "DNS" "pre-check of name syntax"
13834 When this option is set to a non-empty string, it causes Exim to check domain
13835 names for characters that are not allowed in host names before handing them to
13836 the DNS resolver, because some resolvers give temporary errors for names that
13837 contain unusual characters. If a domain name contains any unwanted characters,
13838 a &"not found"& result is forced, and the resolver is not called. The check is
13839 done by matching the domain name against a regular expression, which is the
13840 value of this option. The default pattern is
13841 .code
13842 dns_check_names_pattern = \
13843 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
13844 .endd
13845 which permits only letters, digits, slashes, and hyphens in components, but
13846 they must start and end with a letter or digit. Slashes are not, in fact,
13847 permitted in host names, but they are found in certain NS records (which can be
13848 accessed in Exim by using a &%dnsdb%& lookup). If you set
13849 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
13850 empty string.
13851
13852 .option dns_csa_search_limit main integer 5
13853 This option controls the depth of parental searching for CSA SRV records in the
13854 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
13855
13856 .option dns_csa_use_reverse main boolean true
13857 This option controls whether or not an IP address, given as a CSA domain, is
13858 reversed and looked up in the reverse DNS, as described in more detail in
13859 section &<<SECTverifyCSA>>&.
13860
13861
13862 .option dns_dnssec_ok main integer -1
13863 .cindex "DNS" "resolver options"
13864 .cindex "DNS" "DNSSEC"
13865 If this option is set to a non-negative number then Exim will initialise the
13866 DNS resolver library to either use or not use DNSSEC, overriding the system
13867 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
13868
13869 If the resolver library does not support DNSSEC then this option has no effect.
13870
13871
13872 .option dns_ipv4_lookup main "domain list&!!" unset
13873 .cindex "IPv6" "DNS lookup for AAAA records"
13874 .cindex "DNS" "IPv6 lookup for AAAA records"
13875 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
13876 looks for IPv6 address records (AAAA records) as well as IPv4 address records
13877 (A records) when trying to find IP addresses for hosts, unless the host's
13878 domain matches this list.
13879
13880 This is a fudge to help with name servers that give big delays or otherwise do
13881 not work for the AAAA record type. In due course, when the world's name
13882 servers have all been upgraded, there should be no need for this option.
13883
13884
13885 .option dns_retrans main time 0s
13886 .cindex "DNS" "resolver options"
13887 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
13888 retransmission and retry parameters for DNS lookups. Values of zero (the
13889 defaults) leave the system default settings unchanged. The first value is the
13890 time between retries, and the second is the number of retries. It isn't
13891 totally clear exactly how these settings affect the total time a DNS lookup may
13892 take. I haven't found any documentation about timeouts on DNS lookups; these
13893 parameter values are available in the external resolver interface structure,
13894 but nowhere does it seem to describe how they are used or what you might want
13895 to set in them.
13896
13897
13898 .option dns_retry main integer 0
13899 See &%dns_retrans%& above.
13900
13901
13902 .option dns_use_edns0 main integer -1
13903 .cindex "DNS" "resolver options"
13904 .cindex "DNS" "EDNS0"
13905 If this option is set to a non-negative number then Exim will initialise the
13906 DNS resolver library to either use or not use EDNS0 extensions, overriding
13907 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
13908 on.
13909
13910 If the resolver library does not support EDNS0 then this option has no effect.
13911
13912
13913 .option drop_cr main boolean false
13914 This is an obsolete option that is now a no-op. It used to affect the way Exim
13915 handled CR and LF characters in incoming messages. What happens now is
13916 described in section &<<SECTlineendings>>&.
13917
13918 .option dsn_from main "string&!!" "see below"
13919 .cindex "&'From:'& header line" "in bounces"
13920 .cindex "bounce messages" "&'From:'& line, specifying"
13921 This option can be used to vary the contents of &'From:'& header lines in
13922 bounces and other automatically generated messages (&"Delivery Status
13923 Notifications"& &-- hence the name of the option). The default setting is:
13924 .code
13925 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
13926 .endd
13927 The value is expanded every time it is needed. If the expansion fails, a
13928 panic is logged, and the default value is used.
13929
13930 .option envelope_to_remove main boolean true
13931 .cindex "&'Envelope-to:'& header line"
13932 Exim's transports have an option for adding an &'Envelope-to:'& header to a
13933 message when it is delivered, in exactly the same way as &'Return-path:'& is
13934 handled. &'Envelope-to:'& records the original recipient address from the
13935 messages's envelope that caused the delivery to happen. Such headers should not
13936 be present in incoming messages, and this option causes them to be removed at
13937 the time the message is received, to avoid any problems that might occur when a
13938 delivered message is subsequently sent on to some other recipient.
13939
13940
13941 .option errors_copy main "string list&!!" unset
13942 .cindex "bounce message" "copy to other address"
13943 .cindex "copy of bounce message"
13944 Setting this option causes Exim to send bcc copies of bounce messages that it
13945 generates to other addresses. &*Note*&: This does not apply to bounce messages
13946 coming from elsewhere. The value of the option is a colon-separated list of
13947 items. Each item consists of a pattern, terminated by white space, followed by
13948 a comma-separated list of email addresses. If a pattern contains spaces, it
13949 must be enclosed in double quotes.
13950
13951 Each pattern is processed in the same way as a single item in an address list
13952 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
13953 the bounce message, the message is copied to the addresses on the list. The
13954 items are scanned in order, and once a matching one is found, no further items
13955 are examined. For example:
13956 .code
13957 errors_copy = spqr@mydomain postmaster@mydomain.example :\
13958 rqps@mydomain hostmaster@mydomain.example,\
13959 postmaster@mydomain.example
13960 .endd
13961 .vindex "&$domain$&"
13962 .vindex "&$local_part$&"
13963 The address list is expanded before use. The expansion variables &$local_part$&
13964 and &$domain$& are set from the original recipient of the error message, and if
13965 there was any wildcard matching in the pattern, the expansion
13966 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
13967 variables &$0$&, &$1$&, etc. are set in the normal way.
13968
13969
13970 .option errors_reply_to main string unset
13971 .cindex "bounce message" "&'Reply-to:'& in"
13972 By default, Exim's bounce and delivery warning messages contain the header line
13973 .display
13974 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
13975 .endd
13976 .oindex &%quota_warn_message%&
13977 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
13978 A warning message that is generated by the &%quota_warn_message%& option in an
13979 &(appendfile)& transport may contain its own &'From:'& header line that
13980 overrides the default.
13981
13982 Experience shows that people reply to bounce messages. If the
13983 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
13984 and warning messages. For example:
13985 .code
13986 errors_reply_to = postmaster@my.domain.example
13987 .endd
13988 The value of the option is not expanded. It must specify a valid RFC 2822
13989 address. However, if a warning message that is generated by the
13990 &%quota_warn_message%& option in an &(appendfile)& transport contain its
13991 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
13992 not used.
13993
13994
13995 .option exim_group main string "compile-time configured"
13996 .cindex "gid (group id)" "Exim's own"
13997 .cindex "Exim group"
13998 This option changes the gid under which Exim runs when it gives up root
13999 privilege. The default value is compiled into the binary. The value of this
14000 option is used only when &%exim_user%& is also set. Unless it consists entirely
14001 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
14002 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
14003 security issues.
14004
14005
14006 .option exim_path main string "see below"
14007 .cindex "Exim binary, path name"
14008 This option specifies the path name of the Exim binary, which is used when Exim
14009 needs to re-exec itself. The default is set up to point to the file &'exim'& in
14010 the directory configured at compile time by the BIN_DIRECTORY setting. It
14011 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
14012 other place.
14013 &*Warning*&: Do not use a macro to define the value of this option, because
14014 you will break those Exim utilities that scan the configuration file to find
14015 where the binary is. (They then use the &%-bP%& option to extract option
14016 settings such as the value of &%spool_directory%&.)
14017
14018
14019 .option exim_user main string "compile-time configured"
14020 .cindex "uid (user id)" "Exim's own"
14021 .cindex "Exim user"
14022 This option changes the uid under which Exim runs when it gives up root
14023 privilege. The default value is compiled into the binary. Ownership of the run
14024 time configuration file and the use of the &%-C%& and &%-D%& command line
14025 options is checked against the values in the binary, not what is set here.
14026
14027 Unless it consists entirely of digits, the string is looked up using
14028 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
14029 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
14030 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
14031
14032
14033 .option extra_local_interfaces main "string list" unset
14034 This option defines network interfaces that are to be considered local when
14035 routing, but which are not used for listening by the daemon. See section
14036 &<<SECTreclocipadd>>& for details.
14037
14038
14039 . Allow this long option name to split; give it unsplit as a fifth argument
14040 . for the automatic .oindex that is generated by .option.
14041
14042 .option "extract_addresses_remove_ &~&~arguments" main boolean true &&&
14043 extract_addresses_remove_arguments
14044 .oindex "&%-t%&"
14045 .cindex "command line" "addresses with &%-t%&"
14046 .cindex "Sendmail compatibility" "&%-t%& option"
14047 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
14048 are present on the command line when the &%-t%& option is used to build an
14049 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
14050 line addresses are removed from the recipients list. This is also how Smail
14051 behaves. However, other Sendmail documentation (the O'Reilly book) states that
14052 command line addresses are added to those obtained from the header lines. When
14053 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
14054 argument headers. If it is set false, Exim adds rather than removes argument
14055 addresses.
14056
14057
14058 .option finduser_retries main integer 0
14059 .cindex "NIS, retrying user lookups"
14060 On systems running NIS or other schemes in which user and group information is
14061 distributed from a remote system, there can be times when &[getpwnam()]& and
14062 related functions fail, even when given valid data, because things time out.
14063 Unfortunately these failures cannot be distinguished from genuine &"not found"&
14064 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
14065 many extra times to find a user or a group, waiting for one second between
14066 retries.
14067
14068 .cindex "&_/etc/passwd_&" "multiple reading of"
14069 You should not set this option greater than zero if your user information is in
14070 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
14071 search the file multiple times for non-existent users, and also cause delay.
14072
14073
14074
14075 .option freeze_tell main "string list, comma separated" unset
14076 .cindex "freezing messages" "sending a message when freezing"
14077 On encountering certain errors, or when configured to do so in a system filter,
14078 ACL, or special router, Exim freezes a message. This means that no further
14079 delivery attempts take place until an administrator thaws the message, or the
14080 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
14081 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
14082 warning message whenever it freezes something, unless the message it is
14083 freezing is a locally-generated bounce message. (Without this exception there
14084 is the possibility of looping.) The warning message is sent to the addresses
14085 supplied as the comma-separated value of this option. If several of the
14086 message's addresses cause freezing, only a single message is sent. If the
14087 freezing was automatic, the reason(s) for freezing can be found in the message
14088 log. If you configure freezing in a filter or ACL, you must arrange for any
14089 logging that you require.
14090
14091
14092 .option gecos_name main string&!! unset
14093 .cindex "HP-UX"
14094 .cindex "&""gecos""& field, parsing"
14095 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
14096 password file to hold other information in addition to users' real names. Exim
14097 looks up this field for use when it is creating &'Sender:'& or &'From:'&
14098 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
14099 of the field are used unchanged, except that, if an ampersand is encountered,
14100 it is replaced by the user's login name with the first character forced to
14101 upper case, since this is a convention that is observed on many systems.
14102
14103 When these options are set, &%gecos_pattern%& is treated as a regular
14104 expression that is to be applied to the field (again with && replaced by the
14105 login name), and if it matches, &%gecos_name%& is expanded and used as the
14106 user's name.
14107
14108 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
14109 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
14110 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
14111 name terminates at the first comma, the following can be used:
14112 .code
14113 gecos_pattern = ([^,]*)
14114 gecos_name = $1
14115 .endd
14116
14117 .option gecos_pattern main string unset
14118 See &%gecos_name%& above.
14119
14120
14121 .option gnutls_compat_mode main boolean unset
14122 This option controls whether GnuTLS is used in compatibility mode in an Exim
14123 server. This reduces security slightly, but improves interworking with older
14124 implementations of TLS.
14125
14126
14127 option gnutls_allow_auto_pkcs11 main boolean unset
14128 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
14129 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
14130
14131 See
14132 &url(http://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
14133 for documentation.
14134
14135
14136
14137 .option headers_charset main string "see below"
14138 This option sets a default character set for translating from encoded MIME
14139 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
14140 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
14141 ultimate default is ISO-8859-1. For more details see the description of header
14142 insertions in section &<<SECTexpansionitems>>&.
14143
14144
14145
14146 .option header_maxsize main integer "see below"
14147 .cindex "header section" "maximum size of"
14148 .cindex "limit" "size of message header section"
14149 This option controls the overall maximum size of a message's header
14150 section. The default is the value of HEADER_MAXSIZE in
14151 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
14152 sections are rejected.
14153
14154
14155 .option header_line_maxsize main integer 0
14156 .cindex "header lines" "maximum size of"
14157 .cindex "limit" "size of one header line"
14158 This option limits the length of any individual header line in a message, after
14159 all the continuations have been joined together. Messages with individual
14160 header lines that are longer than the limit are rejected. The default value of
14161 zero means &"no limit"&.
14162
14163
14164
14165
14166 .option helo_accept_junk_hosts main "host list&!!" unset
14167 .cindex "HELO" "accepting junk data"
14168 .cindex "EHLO" "accepting junk data"
14169 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
14170 mail, and gives an error response for invalid data. Unfortunately, there are
14171 some SMTP clients that send syntactic junk. They can be accommodated by setting
14172 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
14173 if you want to do semantic checking.
14174 See also &%helo_allow_chars%& for a way of extending the permitted character
14175 set.
14176
14177
14178 .option helo_allow_chars main string unset
14179 .cindex "HELO" "underscores in"
14180 .cindex "EHLO" "underscores in"
14181 .cindex "underscore in EHLO/HELO"
14182 This option can be set to a string of rogue characters that are permitted in
14183 all EHLO and HELO names in addition to the standard letters, digits,
14184 hyphens, and dots. If you really must allow underscores, you can set
14185 .code
14186 helo_allow_chars = _
14187 .endd
14188 Note that the value is one string, not a list.
14189
14190
14191 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
14192 .cindex "HELO" "forcing reverse lookup"
14193 .cindex "EHLO" "forcing reverse lookup"
14194 If the domain given by a client in a HELO or EHLO command matches this
14195 list, a reverse lookup is done in order to establish the host's true name. The
14196 default forces a lookup if the client host gives the server's name or any of
14197 its IP addresses (in brackets), something that broken clients have been seen to
14198 do.
14199
14200
14201 .option helo_try_verify_hosts main "host list&!!" unset
14202 .cindex "HELO verifying" "optional"
14203 .cindex "EHLO" "verifying, optional"
14204 By default, Exim just checks the syntax of HELO and EHLO commands (see
14205 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
14206 to do more extensive checking of the data supplied by these commands. The ACL
14207 condition &`verify = helo`& is provided to make this possible.
14208 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
14209 to force the check to occur. From release 4.53 onwards, this is no longer
14210 necessary. If the check has not been done before &`verify = helo`& is
14211 encountered, it is done at that time. Consequently, this option is obsolete.
14212 Its specification is retained here for backwards compatibility.
14213
14214 When an EHLO or HELO command is received, if the calling host matches
14215 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
14216 EHLO command either:
14217
14218 .ilist
14219 is an IP literal matching the calling address of the host, or
14220 .next
14221 .cindex "DNS" "reverse lookup"
14222 .cindex "reverse DNS lookup"
14223 matches the host name that Exim obtains by doing a reverse lookup of the
14224 calling host address, or
14225 .next
14226 when looked up using &[gethostbyname()]& (or &[getipnodebyname()]& when
14227 available) yields the calling host address.
14228 .endlist
14229
14230 However, the EHLO or HELO command is not rejected if any of the checks
14231 fail. Processing continues, but the result of the check is remembered, and can
14232 be detected later in an ACL by the &`verify = helo`& condition.
14233
14234 .option helo_verify_hosts main "host list&!!" unset
14235 .cindex "HELO verifying" "mandatory"
14236 .cindex "EHLO" "verifying, mandatory"
14237 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
14238 backwards compatibility. For hosts that match this option, Exim checks the host
14239 name given in the HELO or EHLO in the same way as for
14240 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
14241 rejected with a 550 error, and entries are written to the main and reject logs.
14242 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
14243 error.
14244
14245 .option hold_domains main "domain list&!!" unset
14246 .cindex "domain" "delaying delivery"
14247 .cindex "delivery" "delaying certain domains"
14248 This option allows mail for particular domains to be held on the queue
14249 manually. The option is overridden if a message delivery is forced with the
14250 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
14251 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
14252 item in &%hold_domains%&, no routing or delivery for that address is done, and
14253 it is deferred every time the message is looked at.
14254
14255 This option is intended as a temporary operational measure for delaying the
14256 delivery of mail while some problem is being sorted out, or some new
14257 configuration tested. If you just want to delay the processing of some
14258 domains until a queue run occurs, you should use &%queue_domains%& or
14259 &%queue_smtp_domains%&, not &%hold_domains%&.
14260
14261 A setting of &%hold_domains%& does not override Exim's code for removing
14262 messages from the queue if they have been there longer than the longest retry
14263 time in any retry rule. If you want to hold messages for longer than the normal
14264 retry times, insert a dummy retry rule with a long retry time.
14265
14266
14267 .option host_lookup main "host list&!!" unset
14268 .cindex "host name" "lookup, forcing"
14269 Exim does not look up the name of a calling host from its IP address unless it
14270 is required to compare against some host list, or the host matches
14271 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
14272 option (which normally contains IP addresses rather than host names). The
14273 default configuration file contains
14274 .code
14275 host_lookup = *
14276 .endd
14277 which causes a lookup to happen for all hosts. If the expense of these lookups
14278 is felt to be too great, the setting can be changed or removed.
14279
14280 After a successful reverse lookup, Exim does a forward lookup on the name it
14281 has obtained, to verify that it yields the IP address that it started with. If
14282 this check fails, Exim behaves as if the name lookup failed.
14283
14284 .vindex "&$host_lookup_failed$&"
14285 .vindex "&$sender_host_name$&"
14286 After any kind of failure, the host name (in &$sender_host_name$&) remains
14287 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
14288 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
14289 &`verify = reverse_host_lookup`& in ACLs.
14290
14291
14292 .option host_lookup_order main "string list" &`bydns:byaddr`&
14293 This option specifies the order of different lookup methods when Exim is trying
14294 to find a host name from an IP address. The default is to do a DNS lookup
14295 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
14296 if that fails. You can change the order of these lookups, or omit one entirely,
14297 if you want.
14298
14299 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
14300 multiple PTR records in the DNS and the IP address is not listed in
14301 &_/etc/hosts_&. Different operating systems give different results in this
14302 case. That is why the default tries a DNS lookup first.
14303
14304
14305
14306 .option host_reject_connection main "host list&!!" unset
14307 .cindex "host" "rejecting connections from"
14308 If this option is set, incoming SMTP calls from the hosts listed are rejected
14309 as soon as the connection is made.
14310 This option is obsolete, and retained only for backward compatibility, because
14311 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
14312 connections immediately.
14313
14314 The ability to give an immediate rejection (either by this option or using an
14315 ACL) is provided for use in unusual cases. Many hosts will just try again,
14316 sometimes without much delay. Normally, it is better to use an ACL to reject
14317 incoming messages at a later stage, such as after RCPT commands. See
14318 chapter &<<CHAPACL>>&.
14319
14320
14321 .option hosts_connection_nolog main "host list&!!" unset
14322 .cindex "host" "not logging connections from"
14323 This option defines a list of hosts for which connection logging does not
14324 happen, even though the &%smtp_connection%& log selector is set. For example,
14325 you might want not to log SMTP connections from local processes, or from
14326 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
14327 the daemon; you should therefore strive to restrict its value to a short inline
14328 list of IP addresses and networks. To disable logging SMTP connections from
14329 local processes, you must create a host list with an empty item. For example:
14330 .code
14331 hosts_connection_nolog = :
14332 .endd
14333 If the &%smtp_connection%& log selector is not set, this option has no effect.
14334
14335
14336
14337 .option hosts_treat_as_local main "domain list&!!" unset
14338 .cindex "local host" "domains treated as"
14339 .cindex "host" "treated as local"
14340 If this option is set, any host names that match the domain list are treated as
14341 if they were the local host when Exim is scanning host lists obtained from MX
14342 records
14343 or other sources. Note that the value of this option is a domain list, not a
14344 host list, because it is always used to check host names, not IP addresses.
14345
14346 This option also applies when Exim is matching the special items
14347 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
14348 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
14349 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
14350 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
14351 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
14352 interfaces and recognizing the local host.
14353
14354
14355 .option ibase_servers main "string list" unset
14356 .cindex "InterBase" "server list"
14357 This option provides a list of InterBase servers and associated connection data,
14358 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
14359 The option is available only if Exim has been built with InterBase support.
14360
14361
14362
14363 .option ignore_bounce_errors_after main time 10w
14364 .cindex "bounce message" "discarding"
14365 .cindex "discarding bounce message"
14366 This option affects the processing of bounce messages that cannot be delivered,
14367 that is, those that suffer a permanent delivery failure. (Bounce messages that
14368 suffer temporary delivery failures are of course retried in the usual way.)
14369
14370 After a permanent delivery failure, bounce messages are frozen,
14371 because there is no sender to whom they can be returned. When a frozen bounce
14372 message has been on the queue for more than the given time, it is unfrozen at
14373 the next queue run, and a further delivery is attempted. If delivery fails
14374 again, the bounce message is discarded. This makes it possible to keep failed
14375 bounce messages around for a shorter time than the normal maximum retry time
14376 for frozen messages. For example,
14377 .code
14378 ignore_bounce_errors_after = 12h
14379 .endd
14380 retries failed bounce message deliveries after 12 hours, discarding any further
14381 failures. If the value of this option is set to a zero time period, bounce
14382 failures are discarded immediately. Setting a very long time (as in the default
14383 value) has the effect of disabling this option. For ways of automatically
14384 dealing with other kinds of frozen message, see &%auto_thaw%& and
14385 &%timeout_frozen_after%&.
14386
14387
14388 .option ignore_fromline_hosts main "host list&!!" unset
14389 .cindex "&""From""& line"
14390 .cindex "UUCP" "&""From""& line"
14391 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
14392 the headers of a message. By default this is treated as the start of the
14393 message's body, which means that any following headers are not recognized as
14394 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
14395 match those hosts that insist on sending it. If the sender is actually a local
14396 process rather than a remote host, and is using &%-bs%& to inject the messages,
14397 &%ignore_fromline_local%& must be set to achieve this effect.
14398
14399
14400 .option ignore_fromline_local main boolean false
14401 See &%ignore_fromline_hosts%& above.
14402
14403
14404 .option keep_malformed main time 4d
14405 This option specifies the length of time to keep messages whose spool files
14406 have been corrupted in some way. This should, of course, never happen. At the
14407 next attempt to deliver such a message, it gets removed. The incident is
14408 logged.
14409
14410
14411 .option ldap_ca_cert_dir main string unset
14412 .cindex "LDAP", "TLS CA certificate directory"
14413 This option indicates which directory contains CA certificates for verifying
14414 a TLS certificate presented by an LDAP server.
14415 While Exim does not provide a default value, your SSL library may.
14416 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
14417 and constrained to be a directory.
14418
14419
14420 .option ldap_ca_cert_file main string unset
14421 .cindex "LDAP", "TLS CA certificate file"
14422 This option indicates which file contains CA certificates for verifying
14423 a TLS certificate presented by an LDAP server.
14424 While Exim does not provide a default value, your SSL library may.
14425 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
14426 and constrained to be a file.
14427
14428
14429 .option ldap_cert_file main string unset
14430 .cindex "LDAP" "TLS client certificate file"
14431 This option indicates which file contains an TLS client certificate which
14432 Exim should present to the LDAP server during TLS negotiation.
14433 Should be used together with &%ldap_cert_key%&.
14434
14435
14436 .option ldap_cert_key main string unset
14437 .cindex "LDAP" "TLS client key file"
14438 This option indicates which file contains the secret/private key to use
14439 to prove identity to the LDAP server during TLS negotiation.
14440 Should be used together with &%ldap_cert_file%&, which contains the
14441 identity to be proven.
14442
14443
14444 .option ldap_cipher_suite main string unset
14445 .cindex "LDAP" "TLS cipher suite"
14446 This controls the TLS cipher-suite negotiation during TLS negotiation with
14447 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
14448 cipher-suite options with OpenSSL (as used by LDAP client libraries).
14449
14450
14451 .option ldap_default_servers main "string list" unset
14452 .cindex "LDAP" "default servers"
14453 This option provides a list of LDAP servers which are tried in turn when an
14454 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
14455 details of LDAP queries. This option is available only when Exim has been built
14456 with LDAP support.
14457
14458
14459 .option ldap_require_cert main string unset.
14460 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
14461 This should be one of the values "hard", "demand", "allow", "try" or "never".
14462 A value other than one of these is interpreted as "never".
14463 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
14464 Although Exim does not set a default, the LDAP library probably defaults
14465 to hard/demand.
14466
14467
14468 .option ldap_start_tls main boolean false
14469 .cindex "LDAP" "whether or not to negotiate TLS"
14470 If set, Exim will attempt to negotiate TLS with the LDAP server when
14471 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
14472 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
14473 of SSL-on-connect.
14474 In the event of failure to negotiate TLS, the action taken is controlled
14475 by &%ldap_require_cert%&.
14476
14477
14478 .option ldap_version main integer unset
14479 .cindex "LDAP" "protocol version, forcing"
14480 This option can be used to force Exim to set a specific protocol version for
14481 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
14482 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
14483 the LDAP headers; otherwise it is 2. This option is available only when Exim
14484 has been built with LDAP support.
14485
14486
14487
14488 .option local_from_check main boolean true
14489 .cindex "&'Sender:'& header line" "disabling addition of"
14490 .cindex "&'From:'& header line" "disabling checking of"
14491 When a message is submitted locally (that is, not over a TCP/IP connection) by
14492 an untrusted user, Exim removes any existing &'Sender:'& header line, and
14493 checks that the &'From:'& header line matches the login of the calling user and
14494 the domain specified by &%qualify_domain%&.
14495
14496 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
14497 locally submitted message is automatically qualified by Exim, unless the
14498 &%-bnq%& command line option is used.
14499
14500 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
14501 on the local part. If the &'From:'& header line does not match, Exim adds a
14502 &'Sender:'& header with an address constructed from the calling user's login
14503 and the default qualify domain.
14504
14505 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
14506 and no &'Sender:'& header is ever added. If, in addition, you want to retain
14507 &'Sender:'& header lines supplied by untrusted users, you must also set
14508 &%local_sender_retain%& to be true.
14509
14510 .cindex "envelope sender"
14511 These options affect only the header lines in the message. The envelope sender
14512 is still forced to be the login id at the qualify domain unless
14513 &%untrusted_set_sender%& permits the user to supply an envelope sender.
14514
14515 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
14516 request similar header line checking. See section &<<SECTthesenhea>>&, which
14517 has more details about &'Sender:'& processing.
14518
14519
14520
14521
14522 .option local_from_prefix main string unset
14523 When Exim checks the &'From:'& header line of locally submitted messages for
14524 matching the login id (see &%local_from_check%& above), it can be configured to
14525 ignore certain prefixes and suffixes in the local part of the address. This is
14526 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
14527 appropriate lists, in the same form as the &%local_part_prefix%& and
14528 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
14529 example, if
14530 .code
14531 local_from_prefix = *-
14532 .endd
14533 is set, a &'From:'& line containing
14534 .code
14535 From: anything-user@your.domain.example
14536 .endd
14537 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
14538 matches the actual sender address that is constructed from the login name and
14539 qualify domain.
14540
14541
14542 .option local_from_suffix main string unset
14543 See &%local_from_prefix%& above.
14544
14545
14546 .option local_interfaces main "string list" "see below"
14547 This option controls which network interfaces are used by the daemon for
14548 listening; they are also used to identify the local host when routing. Chapter
14549 &<<CHAPinterfaces>>& contains a full description of this option and the related
14550 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
14551 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
14552 &%local_interfaces%& is
14553 .code
14554 local_interfaces = 0.0.0.0
14555 .endd
14556 when Exim is built without IPv6 support; otherwise it is
14557 .code
14558 local_interfaces = <; ::0 ; 0.0.0.0
14559 .endd
14560
14561 .option local_scan_timeout main time 5m
14562 .cindex "timeout" "for &[local_scan()]& function"
14563 .cindex "&[local_scan()]& function" "timeout"
14564 This timeout applies to the &[local_scan()]& function (see chapter
14565 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
14566 the incoming message is rejected with a temporary error if it is an SMTP
14567 message. For a non-SMTP message, the message is dropped and Exim ends with a
14568 non-zero code. The incident is logged on the main and reject logs.
14569
14570
14571
14572 .option local_sender_retain main boolean false
14573 .cindex "&'Sender:'& header line" "retaining from local submission"
14574 When a message is submitted locally (that is, not over a TCP/IP connection) by
14575 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
14576 do not want this to happen, you must set &%local_sender_retain%&, and you must
14577 also set &%local_from_check%& to be false (Exim will complain if you do not).
14578 See also the ACL modifier &`control = suppress_local_fixups`&. Section
14579 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
14580
14581
14582
14583
14584 .option localhost_number main string&!! unset
14585 .cindex "host" "locally unique number for"
14586 .cindex "message ids" "with multiple hosts"
14587 .vindex "&$localhost_number$&"
14588 Exim's message ids are normally unique only within the local host. If
14589 uniqueness among a set of hosts is required, each host must set a different
14590 value for the &%localhost_number%& option. The string is expanded immediately
14591 after reading the configuration file (so that a number can be computed from the
14592 host name, for example) and the result of the expansion must be a number in the
14593 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
14594 systems). This is available in subsequent string expansions via the variable
14595 &$localhost_number$&. When &%localhost_number is set%&, the final two
14596 characters of the message id, instead of just being a fractional part of the
14597 time, are computed from the time and the local host number as described in
14598 section &<<SECTmessiden>>&.
14599
14600
14601
14602 .option log_file_path main "string list&!!" "set at compile time"
14603 .cindex "log" "file path for"
14604 This option sets the path which is used to determine the names of Exim's log
14605 files, or indicates that logging is to be to syslog, or both. It is expanded
14606 when Exim is entered, so it can, for example, contain a reference to the host
14607 name. If no specific path is set for the log files at compile or run time, they
14608 are written in a sub-directory called &_log_& in Exim's spool directory.
14609 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
14610 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
14611 used. If this string is fixed at your installation (contains no expansion
14612 variables) it is recommended that you do not set this option in the
14613 configuration file, but instead supply the path using LOG_FILE_PATH in
14614 &_Local/Makefile_& so that it is available to Exim for logging errors detected
14615 early on &-- in particular, failure to read the configuration file.
14616
14617
14618 .option log_selector main string unset
14619 .cindex "log" "selectors"
14620 This option can be used to reduce or increase the number of things that Exim
14621 writes to its log files. Its argument is made up of names preceded by plus or
14622 minus characters. For example:
14623 .code
14624 log_selector = +arguments -retry_defer
14625 .endd
14626 A list of possible names and what they control is given in the chapter on
14627 logging, in section &<<SECTlogselector>>&.
14628
14629
14630 .option log_timezone main boolean false
14631 .cindex "log" "timezone for entries"
14632 .vindex "&$tod_log$&"
14633 .vindex "&$tod_zone$&"
14634 By default, the timestamps on log lines are in local time without the
14635 timezone. This means that if your timezone changes twice a year, the timestamps
14636 in log lines are ambiguous for an hour when the clocks go back. One way of
14637 avoiding this problem is to set the timezone to UTC. An alternative is to set
14638 &%log_timezone%& true. This turns on the addition of the timezone offset to
14639 timestamps in log lines. Turning on this option can add quite a lot to the size
14640 of log files because each line is extended by 6 characters. Note that the
14641 &$tod_log$& variable contains the log timestamp without the zone, but there is
14642 another variable called &$tod_zone$& that contains just the timezone offset.
14643
14644
14645 .option lookup_open_max main integer 25
14646 .cindex "too many open files"
14647 .cindex "open files, too many"
14648 .cindex "file" "too many open"
14649 .cindex "lookup" "maximum open files"
14650 .cindex "limit" "open files for lookups"
14651 This option limits the number of simultaneously open files for single-key
14652 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
14653 Exim normally keeps these files open during routing, because often the same
14654 file is required several times. If the limit is reached, Exim closes the least
14655 recently used file. Note that if you are using the &'ndbm'& library, it
14656 actually opens two files for each logical DBM database, though it still counts
14657 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
14658 open files"& errors with NDBM, you need to reduce the value of
14659 &%lookup_open_max%&.
14660
14661
14662 .option max_username_length main integer 0
14663 .cindex "length of login name"
14664 .cindex "user name" "maximum length"
14665 .cindex "limit" "user name length"
14666 Some operating systems are broken in that they truncate long arguments to
14667 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
14668 this option is set greater than zero, any attempt to call &[getpwnam()]& with
14669 an argument that is longer behaves as if &[getpwnam()]& failed.
14670
14671
14672 .option message_body_newlines main bool false
14673 .cindex "message body" "newlines in variables"
14674 .cindex "newline" "in message body variables"
14675 .vindex "&$message_body$&"
14676 .vindex "&$message_body_end$&"
14677 By default, newlines in the message body are replaced by spaces when setting
14678 the &$message_body$& and &$message_body_end$& expansion variables. If this
14679 option is set true, this no longer happens.
14680
14681
14682 .option message_body_visible main integer 500
14683 .cindex "body of message" "visible size"
14684 .cindex "message body" "visible size"
14685 .vindex "&$message_body$&"
14686 .vindex "&$message_body_end$&"
14687 This option specifies how much of a message's body is to be included in the
14688 &$message_body$& and &$message_body_end$& expansion variables.
14689
14690
14691 .option message_id_header_domain main string&!! unset
14692 .cindex "&'Message-ID:'& header line"
14693 If this option is set, the string is expanded and used as the right hand side
14694 (domain) of the &'Message-ID:'& header that Exim creates if a
14695 locally-originated incoming message does not have one. &"Locally-originated"&
14696 means &"not received over TCP/IP."&
14697 Otherwise, the primary host name is used.
14698 Only letters, digits, dot and hyphen are accepted; any other characters are
14699 replaced by hyphens. If the expansion is forced to fail, or if the result is an
14700 empty string, the option is ignored.
14701
14702
14703 .option message_id_header_text main string&!! unset
14704 If this variable is set, the string is expanded and used to augment the text of
14705 the &'Message-id:'& header that Exim creates if a locally-originated incoming
14706 message does not have one. The text of this header is required by RFC 2822 to
14707 take the form of an address. By default, Exim uses its internal message id as
14708 the local part, and the primary host name as the domain. If this option is set,
14709 it is expanded, and provided the expansion is not forced to fail, and does not
14710 yield an empty string, the result is inserted into the header immediately
14711 before the @, separated from the internal message id by a dot. Any characters
14712 that are illegal in an address are automatically converted into hyphens. This
14713 means that variables such as &$tod_log$& can be used, because the spaces and
14714 colons will become hyphens.
14715
14716
14717 .option message_logs main boolean true
14718 .cindex "message logs" "disabling"
14719 .cindex "log" "message log; disabling"
14720 If this option is turned off, per-message log files are not created in the
14721 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
14722 Exim, by reducing the number of files involved in handling a message from a
14723 minimum of four (header spool file, body spool file, delivery journal, and
14724 per-message log) to three. The other major I/O activity is Exim's main log,
14725 which is not affected by this option.
14726
14727
14728 .option message_size_limit main string&!! 50M
14729 .cindex "message" "size limit"
14730 .cindex "limit" "message size"
14731 .cindex "size" "of message, limit"
14732 This option limits the maximum size of message that Exim will process. The
14733 value is expanded for each incoming connection so, for example, it can be made
14734 to depend on the IP address of the remote host for messages arriving via
14735 TCP/IP. After expansion, the value must be a sequence of decimal digits,
14736 optionally followed by K or M.
14737
14738 &*Note*&: This limit cannot be made to depend on a message's sender or any
14739 other properties of an individual message, because it has to be advertised in
14740 the server's response to EHLO. String expansion failure causes a temporary
14741 error. A value of zero means no limit, but its use is not recommended. See also
14742 &%bounce_return_size_limit%&.
14743
14744 Incoming SMTP messages are failed with a 552 error if the limit is
14745 exceeded; locally-generated messages either get a stderr message or a delivery
14746 failure message to the sender, depending on the &%-oe%& setting. Rejection of
14747 an oversized message is logged in both the main and the reject logs. See also
14748 the generic transport option &%message_size_limit%&, which limits the size of
14749 message that an individual transport can process.
14750
14751 If you use a virus-scanner and set this option to to a value larger than the
14752 maximum size that your virus-scanner is configured to support, you may get
14753 failures triggered by large mails. The right size to configure for the
14754 virus-scanner depends upon what data is passed and the options in use but it's
14755 probably safest to just set it to a little larger than this value. Eg, with a
14756 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
14757 some problems may result.
14758
14759 A value of 0 will disable size limit checking; Exim will still advertise the
14760 SIZE extension in an EHLO response, but without a limit, so as to permit
14761 SMTP clients to still indicate the message size along with the MAIL verb.
14762
14763
14764 .option move_frozen_messages main boolean false
14765 .cindex "frozen messages" "moving"
14766 This option, which is available only if Exim has been built with the setting
14767 .code
14768 SUPPORT_MOVE_FROZEN_MESSAGES=yes
14769 .endd
14770 in &_Local/Makefile_&, causes frozen messages and their message logs to be
14771 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
14772 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
14773 standard utilities for handling such moved messages, and they do not show up in
14774 lists generated by &%-bp%& or by the Exim monitor.
14775
14776
14777 .option mua_wrapper main boolean false
14778 Setting this option true causes Exim to run in a very restrictive mode in which
14779 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
14780 contains a full description of this facility.
14781
14782
14783
14784 .option mysql_servers main "string list" unset
14785 .cindex "MySQL" "server list"
14786 This option provides a list of MySQL servers and associated connection data, to
14787 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
14788 option is available only if Exim has been built with MySQL support.
14789
14790
14791 .option never_users main "string list&!!" unset
14792 This option is expanded just once, at the start of Exim's processing. Local
14793 message deliveries are normally run in processes that are setuid to the
14794 recipient, and remote deliveries are normally run under Exim's own uid and gid.
14795 It is usually desirable to prevent any deliveries from running as root, as a
14796 safety precaution.
14797
14798 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
14799 list of users that must not be used for local deliveries. This list is fixed in
14800 the binary and cannot be overridden by the configuration file. By default, it
14801 contains just the single user name &"root"&. The &%never_users%& runtime option
14802 can be used to add more users to the fixed list.
14803
14804 If a message is to be delivered as one of the users on the fixed list or the
14805 &%never_users%& list, an error occurs, and delivery is deferred. A common
14806 example is
14807 .code
14808 never_users = root:daemon:bin
14809 .endd
14810 Including root is redundant if it is also on the fixed list, but it does no
14811 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
14812 transport driver.
14813
14814
14815 .option openssl_options main "string list" "+no_sslv2"
14816 .cindex "OpenSSL "compatibility options"
14817 This option allows an administrator to adjust the SSL options applied
14818 by OpenSSL to connections. It is given as a space-separated list of items,
14819 each one to be +added or -subtracted from the current value.
14820
14821 This option is only available if Exim is built against OpenSSL. The values
14822 available for this option vary according to the age of your OpenSSL install.
14823 The &"all"& value controls a subset of flags which are available, typically
14824 the bug workaround options. The &'SSL_CTX_set_options'& man page will
14825 list the values known on your system and Exim should support all the
14826 &"bug workaround"& options and many of the &"modifying"& options. The Exim
14827 names lose the leading &"SSL_OP_"& and are lower-cased.
14828
14829 Note that adjusting the options can have severe impact upon the security of
14830 SSL as used by Exim. It is possible to disable safety checks and shoot
14831 yourself in the foot in various unpleasant ways. This option should not be
14832 adjusted lightly. An unrecognised item will be detected at startup, by
14833 invoking Exim with the &%-bV%& flag.
14834
14835 Historical note: prior to release 4.80, Exim defaulted this value to
14836 "+dont_insert_empty_fragments", which may still be needed for compatibility
14837 with some clients, but which lowers security by increasing exposure to
14838 some now infamous attacks.
14839
14840 An example:
14841 .code
14842 # Make both old MS and old Eudora happy:
14843 openssl_options = -all +microsoft_big_sslv3_buffer \
14844 +dont_insert_empty_fragments
14845 .endd
14846
14847 Possible options may include:
14848 .ilist
14849 &`all`&
14850 .next
14851 &`allow_unsafe_legacy_renegotiation`&
14852 .next
14853 &`cipher_server_preference`&
14854 .next
14855 &`dont_insert_empty_fragments`&
14856 .next
14857 &`ephemeral_rsa`&
14858 .next
14859 &`legacy_server_connect`&
14860 .next
14861 &`microsoft_big_sslv3_buffer`&
14862 .next
14863 &`microsoft_sess_id_bug`&
14864 .next
14865 &`msie_sslv2_rsa_padding`&
14866 .next
14867 &`netscape_challenge_bug`&
14868 .next
14869 &`netscape_reuse_cipher_change_bug`&
14870 .next
14871 &`no_compression`&
14872 .next
14873 &`no_session_resumption_on_renegotiation`&
14874 .next
14875 &`no_sslv2`&
14876 .next
14877 &`no_sslv3`&
14878 .next
14879 &`no_ticket`&
14880 .next
14881 &`no_tlsv1`&
14882 .next
14883 &`no_tlsv1_1`&
14884 .next
14885 &`no_tlsv1_2`&
14886 .next
14887 &`safari_ecdhe_ecdsa_bug`&
14888 .next
14889 &`single_dh_use`&
14890 .next
14891 &`single_ecdh_use`&
14892 .next
14893 &`ssleay_080_client_dh_bug`&
14894 .next
14895 &`sslref2_reuse_cert_type_bug`&
14896 .next
14897 &`tls_block_padding_bug`&
14898 .next
14899 &`tls_d5_bug`&
14900 .next
14901 &`tls_rollback_bug`&
14902 .endlist
14903
14904 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
14905 all clients connecting using the MacOS SecureTransport TLS facility prior
14906 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
14907 to negotiate TLS then this option value might help, provided that your OpenSSL
14908 release is new enough to contain this work-around. This may be a situation
14909 where you have to upgrade OpenSSL to get buggy clients working.
14910
14911
14912 .option oracle_servers main "string list" unset
14913 .cindex "Oracle" "server list"
14914 This option provides a list of Oracle servers and associated connection data,
14915 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
14916 The option is available only if Exim has been built with Oracle support.
14917
14918
14919 .option percent_hack_domains main "domain list&!!" unset
14920 .cindex "&""percent hack""&"
14921 .cindex "source routing" "in email address"
14922 .cindex "address" "source-routed"
14923 The &"percent hack"& is the convention whereby a local part containing a
14924 percent sign is re-interpreted as a new email address, with the percent
14925 replaced by @. This is sometimes called &"source routing"&, though that term is
14926 also applied to RFC 2822 addresses that begin with an @ character. If this
14927 option is set, Exim implements the percent facility for those domains listed,
14928 but no others. This happens before an incoming SMTP address is tested against
14929 an ACL.
14930
14931 &*Warning*&: The &"percent hack"& has often been abused by people who are
14932 trying to get round relaying restrictions. For this reason, it is best avoided
14933 if at all possible. Unfortunately, a number of less security-conscious MTAs
14934 implement it unconditionally. If you are running Exim on a gateway host, and
14935 routing mail through to internal MTAs without processing the local parts, it is
14936 a good idea to reject recipient addresses with percent characters in their
14937 local parts. Exim's default configuration does this.
14938
14939
14940 .option perl_at_start main boolean false
14941 This option is available only when Exim is built with an embedded Perl
14942 interpreter. See chapter &<<CHAPperl>>& for details of its use.
14943
14944
14945 .option perl_startup main string unset
14946 This option is available only when Exim is built with an embedded Perl
14947 interpreter. See chapter &<<CHAPperl>>& for details of its use.
14948
14949
14950 .option pgsql_servers main "string list" unset
14951 .cindex "PostgreSQL lookup type" "server list"
14952 This option provides a list of PostgreSQL servers and associated connection
14953 data, to be used in conjunction with &(pgsql)& lookups (see section
14954 &<<SECID72>>&). The option is available only if Exim has been built with
14955 PostgreSQL support.
14956
14957
14958 .option pid_file_path main string&!! "set at compile time"
14959 .cindex "daemon" "pid file path"
14960 .cindex "pid file, path for"
14961 This option sets the name of the file to which the Exim daemon writes its
14962 process id. The string is expanded, so it can contain, for example, references
14963 to the host name:
14964 .code
14965 pid_file_path = /var/log/$primary_hostname/exim.pid
14966 .endd
14967 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
14968 spool directory.
14969 The value set by the option can be overridden by the &%-oP%& command line
14970 option. A pid file is not written if a &"non-standard"& daemon is run by means
14971 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
14972
14973
14974 .option pipelining_advertise_hosts main "host list&!!" *
14975 .cindex "PIPELINING" "suppressing advertising"
14976 This option can be used to suppress the advertisement of the SMTP
14977 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
14978 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
14979 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
14980 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
14981 that clients will use it; &"out of order"& commands that are &"expected"& do
14982 not count as protocol errors (see &%smtp_max_synprot_errors%&).
14983
14984
14985 .option preserve_message_logs main boolean false
14986 .cindex "message logs" "preserving"
14987 If this option is set, message log files are not deleted when messages are
14988 completed. Instead, they are moved to a sub-directory of the spool directory
14989 called &_msglog.OLD_&, where they remain available for statistical or debugging
14990 purposes. This is a dangerous option to set on systems with any appreciable
14991 volume of mail. Use with care!
14992
14993
14994 .option primary_hostname main string "see below"
14995 .cindex "name" "of local host"
14996 .cindex "host" "name of local"
14997 .cindex "local host" "name of"
14998 .vindex "&$primary_hostname$&"
14999 This specifies the name of the current host. It is used in the default EHLO or
15000 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
15001 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
15002 The value is also used by default in some SMTP response messages from an Exim
15003 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
15004
15005 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
15006 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
15007 contains only one component, Exim passes it to &[gethostbyname()]& (or
15008 &[getipnodebyname()]& when available) in order to obtain the fully qualified
15009 version. The variable &$primary_hostname$& contains the host name, whether set
15010 explicitly by this option, or defaulted.
15011
15012
15013 .option print_topbitchars main boolean false
15014 .cindex "printing characters"
15015 .cindex "8-bit characters"
15016 By default, Exim considers only those characters whose codes lie in the range
15017 32&--126 to be printing characters. In a number of circumstances (for example,
15018 when writing log entries) non-printing characters are converted into escape
15019 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
15020 is set, code values of 128 and above are also considered to be printing
15021 characters.
15022
15023 This option also affects the header syntax checks performed by the
15024 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
15025 the user's full name when constructing From: and Sender: addresses (as
15026 described in section &<<SECTconstr>>&). Setting this option can cause
15027 Exim to generate eight bit message headers that do not conform to the
15028 standards.
15029
15030
15031 .option process_log_path main string unset
15032 .cindex "process log path"
15033 .cindex "log" "process log"
15034 .cindex "&'exiwhat'&"
15035 This option sets the name of the file to which an Exim process writes its
15036 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
15037 utility script. If this option is unset, the file called &_exim-process.info_&
15038 in Exim's spool directory is used. The ability to specify the name explicitly
15039 can be useful in environments where two different Exims are running, using
15040 different spool directories.
15041
15042
15043 .option prod_requires_admin main boolean true
15044 .oindex "&%-M%&"
15045 .oindex "&%-R%&"
15046 .oindex "&%-q%&"
15047 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
15048 admin user unless &%prod_requires_admin%& is set false. See also
15049 &%queue_list_requires_admin%&.
15050
15051
15052 .option qualify_domain main string "see below"
15053 .cindex "domain" "for qualifying addresses"
15054 .cindex "address" "qualification"
15055 This option specifies the domain name that is added to any envelope sender
15056 addresses that do not have a domain qualification. It also applies to
15057 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
15058 are accepted by default only for locally-generated messages. Qualification is
15059 also applied to addresses in header lines such as &'From:'& and &'To:'& for
15060 locally-generated messages, unless the &%-bnq%& command line option is used.
15061
15062 Messages from external sources must always contain fully qualified addresses,
15063 unless the sending host matches &%sender_unqualified_hosts%& or
15064 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
15065 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
15066 necessary. Internally, Exim always works with fully qualified envelope
15067 addresses. If &%qualify_domain%& is not set, it defaults to the
15068 &%primary_hostname%& value.
15069
15070
15071 .option qualify_recipient main string "see below"
15072 This option allows you to specify a different domain for qualifying recipient
15073 addresses to the one that is used for senders. See &%qualify_domain%& above.
15074
15075
15076
15077 .option queue_domains main "domain list&!!" unset
15078 .cindex "domain" "specifying non-immediate delivery"
15079 .cindex "queueing incoming messages"
15080 .cindex "message" "queueing certain domains"
15081 This option lists domains for which immediate delivery is not required.
15082 A delivery process is started whenever a message is received, but only those
15083 domains that do not match are processed. All other deliveries wait until the
15084 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
15085
15086
15087 .option queue_list_requires_admin main boolean true
15088 .oindex "&%-bp%&"
15089 The &%-bp%& command-line option, which lists the messages that are on the
15090 queue, requires the caller to be an admin user unless
15091 &%queue_list_requires_admin%& is set false. See also &%prod_requires_admin%&.
15092
15093
15094 .option queue_only main boolean false
15095 .cindex "queueing incoming messages"
15096 .cindex "message" "queueing unconditionally"
15097 If &%queue_only%& is set, a delivery process is not automatically started
15098 whenever a message is received. Instead, the message waits on the queue for the
15099 next queue run. Even if &%queue_only%& is false, incoming messages may not get
15100 delivered immediately when certain conditions (such as heavy load) occur.
15101
15102 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
15103 and &%-odi%& command line options override &%queue_only%& unless
15104 &%queue_only_override%& is set false. See also &%queue_only_file%&,
15105 &%queue_only_load%&, and &%smtp_accept_queue%&.
15106
15107
15108 .option queue_only_file main string unset
15109 .cindex "queueing incoming messages"
15110 .cindex "message" "queueing by file existence"
15111 This option can be set to a colon-separated list of absolute path names, each
15112 one optionally preceded by &"smtp"&. When Exim is receiving a message,
15113 it tests for the existence of each listed path using a call to &[stat()]&. For
15114 each path that exists, the corresponding queueing option is set.
15115 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
15116 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
15117 .code
15118 queue_only_file = smtp/some/file
15119 .endd
15120 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
15121 &_/some/file_& exists.
15122
15123
15124 .option queue_only_load main fixed-point unset
15125 .cindex "load average"
15126 .cindex "queueing incoming messages"
15127 .cindex "message" "queueing by load"
15128 If the system load average is higher than this value, incoming messages from
15129 all sources are queued, and no automatic deliveries are started. If this
15130 happens during local or remote SMTP input, all subsequent messages received on
15131 the same SMTP connection are queued by default, whatever happens to the load in
15132 the meantime, but this can be changed by setting &%queue_only_load_latch%&
15133 false.
15134
15135 Deliveries will subsequently be performed by queue runner processes. This
15136 option has no effect on ancient operating systems on which Exim cannot
15137 determine the load average. See also &%deliver_queue_load_max%& and
15138 &%smtp_load_reserve%&.
15139
15140
15141 .option queue_only_load_latch main boolean true
15142 .cindex "load average" "re-evaluating per message"
15143 When this option is true (the default), once one message has been queued
15144 because the load average is higher than the value set by &%queue_only_load%&,
15145 all subsequent messages received on the same SMTP connection are also queued.
15146 This is a deliberate choice; even though the load average may fall below the
15147 threshold, it doesn't seem right to deliver later messages on the same
15148 connection when not delivering earlier ones. However, there are special
15149 circumstances such as very long-lived connections from scanning appliances
15150 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
15151 should be set false. This causes the value of the load average to be
15152 re-evaluated for each message.
15153
15154
15155 .option queue_only_override main boolean true
15156 .cindex "queueing incoming messages"
15157 When this option is true, the &%-od%&&'x'& command line options override the
15158 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
15159 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
15160 to override; they are accepted, but ignored.
15161
15162
15163 .option queue_run_in_order main boolean false
15164 .cindex "queue runner" "processing messages in order"
15165 If this option is set, queue runs happen in order of message arrival instead of
15166 in an arbitrary order. For this to happen, a complete list of the entire queue
15167 must be set up before the deliveries start. When the queue is all held in a
15168 single directory (the default), a single list is created for both the ordered
15169 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
15170 single list is not created when &%queue_run_in_order%& is false. In this case,
15171 the sub-directories are processed one at a time (in a random order), and this
15172 avoids setting up one huge list for the whole queue. Thus, setting
15173 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
15174 when the queue is large, because of the extra work in setting up the single,
15175 large list. In most situations, &%queue_run_in_order%& should not be set.
15176
15177
15178
15179 .option queue_run_max main integer 5
15180 .cindex "queue runner" "maximum number of"
15181 This controls the maximum number of queue runner processes that an Exim daemon
15182 can run simultaneously. This does not mean that it starts them all at once,
15183 but rather that if the maximum number are still running when the time comes to
15184 start another one, it refrains from starting another one. This can happen with
15185 very large queues and/or very sluggish deliveries. This option does not,
15186 however, interlock with other processes, so additional queue runners can be
15187 started by other means, or by killing and restarting the daemon.
15188
15189 Setting this option to zero does not suppress queue runs; rather, it disables
15190 the limit, allowing any number of simultaneous queue runner processes to be
15191 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
15192 the daemon's command line.
15193
15194 .option queue_smtp_domains main "domain list&!!" unset
15195 .cindex "queueing incoming messages"
15196 .cindex "message" "queueing remote deliveries"
15197 When this option is set, a delivery process is started whenever a message is
15198 received, routing is performed, and local deliveries take place.
15199 However, if any SMTP deliveries are required for domains that match
15200 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
15201 message waits on the queue for the next queue run. Since routing of the message
15202 has taken place, Exim knows to which remote hosts it must be delivered, and so
15203 when the queue run happens, multiple messages for the same host are delivered
15204 over a single SMTP connection. The &%-odqs%& command line option causes all
15205 SMTP deliveries to be queued in this way, and is equivalent to setting
15206 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
15207 &%queue_domains%&.
15208
15209
15210 .option receive_timeout main time 0s
15211 .cindex "timeout" "for non-SMTP input"
15212 This option sets the timeout for accepting a non-SMTP message, that is, the
15213 maximum time that Exim waits when reading a message on the standard input. If
15214 the value is zero, it will wait for ever. This setting is overridden by the
15215 &%-or%& command line option. The timeout for incoming SMTP messages is
15216 controlled by &%smtp_receive_timeout%&.
15217
15218 .option received_header_text main string&!! "see below"
15219 .cindex "customizing" "&'Received:'& header"
15220 .cindex "&'Received:'& header line" "customizing"
15221 This string defines the contents of the &'Received:'& message header that is
15222 added to each message, except for the timestamp, which is automatically added
15223 on at the end (preceded by a semicolon). The string is expanded each time it is
15224 used. If the expansion yields an empty string, no &'Received:'& header line is
15225 added to the message. Otherwise, the string should start with the text
15226 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
15227 header lines. The default setting is:
15228
15229 .code
15230 received_header_text = Received: \
15231 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
15232 {${if def:sender_ident \
15233 {from ${quote_local_part:$sender_ident} }}\
15234 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
15235 by $primary_hostname \
15236 ${if def:received_protocol {with $received_protocol}} \
15237 ${if def:tls_in_cipher {($tls_in_cipher)\n\t}}\
15238 (Exim $version_number)\n\t\
15239 ${if def:sender_address \
15240 {(envelope-from <$sender_address>)\n\t}}\
15241 id $message_exim_id\
15242 ${if def:received_for {\n\tfor $received_for}}
15243 .endd
15244
15245 The reference to the TLS cipher is omitted when Exim is built without TLS
15246 support. The use of conditional expansions ensures that this works for both
15247 locally generated messages and messages received from remote hosts, giving
15248 header lines such as the following:
15249 .code
15250 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
15251 by marley.carol.example with esmtp (Exim 4.00)
15252 (envelope-from <bob@carol.example>)
15253 id 16IOWa-00019l-00
15254 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
15255 Received: by scrooge.carol.example with local (Exim 4.00)
15256 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
15257 .endd
15258 Until the body of the message has been received, the timestamp is the time when
15259 the message started to be received. Once the body has arrived, and all policy
15260 checks have taken place, the timestamp is updated to the time at which the
15261 message was accepted.
15262
15263
15264 .option received_headers_max main integer 30
15265 .cindex "loop" "prevention"
15266 .cindex "mail loop prevention"
15267 .cindex "&'Received:'& header line" "counting"
15268 When a message is to be delivered, the number of &'Received:'& headers is
15269 counted, and if it is greater than this parameter, a mail loop is assumed to
15270 have occurred, the delivery is abandoned, and an error message is generated.
15271 This applies to both local and remote deliveries.
15272
15273
15274 .option recipient_unqualified_hosts main "host list&!!" unset
15275 .cindex "unqualified addresses"
15276 .cindex "host" "unqualified addresses from"
15277 This option lists those hosts from which Exim is prepared to accept unqualified
15278 recipient addresses in message envelopes. The addresses are made fully
15279 qualified by the addition of the &%qualify_recipient%& value. This option also
15280 affects message header lines. Exim does not reject unqualified recipient
15281 addresses in headers, but it qualifies them only if the message came from a
15282 host that matches &%recipient_unqualified_hosts%&,
15283 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
15284 option was not set.
15285
15286
15287 .option recipients_max main integer 0
15288 .cindex "limit" "number of recipients"
15289 .cindex "recipient" "maximum number"
15290 If this option is set greater than zero, it specifies the maximum number of
15291 original recipients for any message. Additional recipients that are generated
15292 by aliasing or forwarding do not count. SMTP messages get a 452 response for
15293 all recipients over the limit; earlier recipients are delivered as normal.
15294 Non-SMTP messages with too many recipients are failed, and no deliveries are
15295 done.
15296
15297 .cindex "RCPT" "maximum number of incoming"
15298 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
15299 RCPT commands in a single message.
15300
15301
15302 .option recipients_max_reject main boolean false
15303 If this option is set true, Exim rejects SMTP messages containing too many
15304 recipients by giving 552 errors to the surplus RCPT commands, and a 554
15305 error to the eventual DATA command. Otherwise (the default) it gives a 452
15306 error to the surplus RCPT commands and accepts the message on behalf of the
15307 initial set of recipients. The remote server should then re-send the message
15308 for the remaining recipients at a later time.
15309
15310
15311 .option remote_max_parallel main integer 2
15312 .cindex "delivery" "parallelism for remote"
15313 This option controls parallel delivery of one message to a number of remote
15314 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
15315 does all the remote deliveries for a message one by one. Otherwise, if a single
15316 message has to be delivered to more than one remote host, or if several copies
15317 have to be sent to the same remote host, up to &%remote_max_parallel%&
15318 deliveries are done simultaneously. If more than &%remote_max_parallel%&
15319 deliveries are required, the maximum number of processes are started, and as
15320 each one finishes, another is begun. The order of starting processes is the
15321 same as if sequential delivery were being done, and can be controlled by the
15322 &%remote_sort_domains%& option. If parallel delivery takes place while running
15323 with debugging turned on, the debugging output from each delivery process is
15324 tagged with its process id.
15325
15326 This option controls only the maximum number of parallel deliveries for one
15327 message in one Exim delivery process. Because Exim has no central queue
15328 manager, there is no way of controlling the total number of simultaneous
15329 deliveries if the configuration allows a delivery attempt as soon as a message
15330 is received.
15331
15332 .cindex "number of deliveries"
15333 .cindex "delivery" "maximum number of"
15334 If you want to control the total number of deliveries on the system, you
15335 need to set the &%queue_only%& option. This ensures that all incoming messages
15336 are added to the queue without starting a delivery process. Then set up an Exim
15337 daemon to start queue runner processes at appropriate intervals (probably
15338 fairly often, for example, every minute), and limit the total number of queue
15339 runners by setting the &%queue_run_max%& parameter. Because each queue runner
15340 delivers only one message at a time, the maximum number of deliveries that can
15341 then take place at once is &%queue_run_max%& multiplied by
15342 &%remote_max_parallel%&.
15343
15344 If it is purely remote deliveries you want to control, use
15345 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
15346 doing the SMTP routing before queueing, so that several messages for the same
15347 host will eventually get delivered down the same connection.
15348
15349
15350 .option remote_sort_domains main "domain list&!!" unset
15351 .cindex "sorting remote deliveries"
15352 .cindex "delivery" "sorting remote"
15353 When there are a number of remote deliveries for a message, they are sorted by
15354 domain into the order given by this list. For example,
15355 .code
15356 remote_sort_domains = *.cam.ac.uk:*.uk
15357 .endd
15358 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
15359 then to those in the &%uk%& domain, then to any others.
15360
15361
15362 .option retry_data_expire main time 7d
15363 .cindex "hints database" "data expiry"
15364 This option sets a &"use before"& time on retry information in Exim's hints
15365 database. Any older retry data is ignored. This means that, for example, once a
15366 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
15367 past failures.
15368
15369
15370 .option retry_interval_max main time 24h
15371 .cindex "retry" "limit on interval"
15372 .cindex "limit" "on retry interval"
15373 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
15374 intervals between delivery attempts for messages that cannot be delivered
15375 straight away. This option sets an overall limit to the length of time between
15376 retries. It cannot be set greater than 24 hours; any attempt to do so forces
15377 the default value.
15378
15379
15380 .option return_path_remove main boolean true
15381 .cindex "&'Return-path:'& header line" "removing"
15382 RFC 2821, section 4.4, states that an SMTP server must insert a
15383 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
15384 The &'Return-path:'& header preserves the sender address as received in the
15385 MAIL command. This description implies that this header should not be present
15386 in an incoming message. If &%return_path_remove%& is true, any existing
15387 &'Return-path:'& headers are removed from messages at the time they are
15388 received. Exim's transports have options for adding &'Return-path:'& headers at
15389 the time of delivery. They are normally used only for final local deliveries.
15390
15391
15392 .option return_size_limit main integer 100K
15393 This option is an obsolete synonym for &%bounce_return_size_limit%&.
15394
15395
15396 .option rfc1413_hosts main "host list&!!" *
15397 .cindex "RFC 1413"
15398 .cindex "host" "for RFC 1413 calls"
15399 RFC 1413 identification calls are made to any client host which matches an item
15400 in the list.
15401
15402 .option rfc1413_query_timeout main time 5s
15403 .cindex "RFC 1413" "query timeout"
15404 .cindex "timeout" "for RFC 1413 call"
15405 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
15406 no RFC 1413 calls are ever made.
15407
15408
15409 .option sender_unqualified_hosts main "host list&!!" unset
15410 .cindex "unqualified addresses"
15411 .cindex "host" "unqualified addresses from"
15412 This option lists those hosts from which Exim is prepared to accept unqualified
15413 sender addresses. The addresses are made fully qualified by the addition of
15414 &%qualify_domain%&. This option also affects message header lines. Exim does
15415 not reject unqualified addresses in headers that contain sender addresses, but
15416 it qualifies them only if the message came from a host that matches
15417 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
15418 using TCP/IP), and the &%-bnq%& option was not set.
15419
15420
15421 .option smtp_accept_keepalive main boolean true
15422 .cindex "keepalive" "on incoming connection"
15423 This option controls the setting of the SO_KEEPALIVE option on incoming
15424 TCP/IP socket connections. When set, it causes the kernel to probe idle
15425 connections periodically, by sending packets with &"old"& sequence numbers. The
15426 other end of the connection should send an acknowledgment if the connection is
15427 still okay or a reset if the connection has been aborted. The reason for doing
15428 this is that it has the beneficial effect of freeing up certain types of
15429 connection that can get stuck when the remote host is disconnected without
15430 tidying up the TCP/IP call properly. The keepalive mechanism takes several
15431 hours to detect unreachable hosts.
15432
15433
15434
15435 .option smtp_accept_max main integer 20
15436 .cindex "limit" "incoming SMTP connections"
15437 .cindex "SMTP" "incoming connection count"
15438 .cindex "inetd"
15439 This option specifies the maximum number of simultaneous incoming SMTP calls
15440 that Exim will accept. It applies only to the listening daemon; there is no
15441 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
15442 value is set to zero, no limit is applied. However, it is required to be
15443 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
15444 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
15445
15446 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
15447 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
15448 that limit has not been reached for the client host, &%smtp_accept_reserve%&
15449 and &%smtp_load_reserve%& are then checked before accepting the connection.
15450
15451
15452 .option smtp_accept_max_nonmail main integer 10
15453 .cindex "limit" "non-mail SMTP commands"
15454 .cindex "SMTP" "limiting non-mail commands"
15455 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
15456 the connection if there are too many. This option defines &"too many"&. The
15457 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
15458 client looping sending EHLO, for example. The check is applied only if the
15459 client host matches &%smtp_accept_max_nonmail_hosts%&.
15460
15461 When a new message is expected, one occurrence of RSET is not counted. This
15462 allows a client to send one RSET between messages (this is not necessary,
15463 but some clients do it). Exim also allows one uncounted occurrence of HELO
15464 or EHLO, and one occurrence of STARTTLS between messages. After
15465 starting up a TLS session, another EHLO is expected, and so it too is not
15466 counted. The first occurrence of AUTH in a connection, or immediately
15467 following STARTTLS is not counted. Otherwise, all commands other than
15468 MAIL, RCPT, DATA, and QUIT are counted.
15469
15470
15471 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
15472 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
15473 check by setting this option. The default value makes it apply to all hosts. By
15474 changing the value, you can exclude any badly-behaved hosts that you have to
15475 live with.
15476
15477
15478 . Allow this long option name to split; give it unsplit as a fifth argument
15479 . for the automatic .oindex that is generated by .option.
15480 . We insert " &~&~" which is both pretty nasty visually and results in
15481 . non-searchable text. HowItWorks.txt mentions an option for inserting
15482 . zero-width-space, which would be nicer visually and results in (at least)
15483 . html that Firefox will split on when it's forced to reflow (rather than
15484 . inserting a horizontal scrollbar). However, the text is still not
15485 . searchable. NM changed this occurrence for bug 1197 to no longer allow
15486 . the option name to split.
15487
15488 .option "smtp_accept_max_per_connection" main integer 1000 &&&
15489 smtp_accept_max_per_connection
15490 .cindex "SMTP" "limiting incoming message count"
15491 .cindex "limit" "messages per SMTP connection"
15492 The value of this option limits the number of MAIL commands that Exim is
15493 prepared to accept over a single SMTP connection, whether or not each command
15494 results in the transfer of a message. After the limit is reached, a 421
15495 response is given to subsequent MAIL commands. This limit is a safety
15496 precaution against a client that goes mad (incidents of this type have been
15497 seen).
15498
15499
15500 .option smtp_accept_max_per_host main string&!! unset
15501 .cindex "limit" "SMTP connections from one host"
15502 .cindex "host" "limiting SMTP connections from"
15503 This option restricts the number of simultaneous IP connections from a single
15504 host (strictly, from a single IP address) to the Exim daemon. The option is
15505 expanded, to enable different limits to be applied to different hosts by
15506 reference to &$sender_host_address$&. Once the limit is reached, additional
15507 connection attempts from the same host are rejected with error code 421. This
15508 is entirely independent of &%smtp_accept_reserve%&. The option's default value
15509 of zero imposes no limit. If this option is set greater than zero, it is
15510 required that &%smtp_accept_max%& be non-zero.
15511
15512 &*Warning*&: When setting this option you should not use any expansion
15513 constructions that take an appreciable amount of time. The expansion and test
15514 happen in the main daemon loop, in order to reject additional connections
15515 without forking additional processes (otherwise a denial-of-service attack
15516 could cause a vast number or processes to be created). While the daemon is
15517 doing this processing, it cannot accept any other incoming connections.
15518
15519
15520
15521 .option smtp_accept_queue main integer 0
15522 .cindex "SMTP" "incoming connection count"
15523 .cindex "queueing incoming messages"
15524 .cindex "message" "queueing by SMTP connection count"
15525 If the number of simultaneous incoming SMTP connections being handled via the
15526 listening daemon exceeds this value, messages received by SMTP are just placed
15527 on the queue; no delivery processes are started automatically. The count is
15528 fixed at the start of an SMTP connection. It cannot be updated in the
15529 subprocess that receives messages, and so the queueing or not queueing applies
15530 to all messages received in the same connection.
15531
15532 A value of zero implies no limit, and clearly any non-zero value is useful only
15533 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
15534 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
15535 various &%-od%&&'x'& command line options.
15536
15537
15538 . See the comment on smtp_accept_max_per_connection
15539
15540 .option "smtp_accept_queue_per_connection" main integer 10 &&&
15541 smtp_accept_queue_per_connection
15542 .cindex "queueing incoming messages"
15543 .cindex "message" "queueing by message count"
15544 This option limits the number of delivery processes that Exim starts
15545 automatically when receiving messages via SMTP, whether via the daemon or by
15546 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
15547 and the number of messages received in a single SMTP session exceeds this
15548 number, subsequent messages are placed on the queue, but no delivery processes
15549 are started. This helps to limit the number of Exim processes when a server
15550 restarts after downtime and there is a lot of mail waiting for it on other
15551 systems. On large systems, the default should probably be increased, and on
15552 dial-in client systems it should probably be set to zero (that is, disabled).
15553
15554
15555 .option smtp_accept_reserve main integer 0
15556 .cindex "SMTP" "incoming call count"
15557 .cindex "host" "reserved"
15558 When &%smtp_accept_max%& is set greater than zero, this option specifies a
15559 number of SMTP connections that are reserved for connections from the hosts
15560 that are specified in &%smtp_reserve_hosts%&. The value set in
15561 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
15562 restricted to this number of connections; the option specifies a minimum number
15563 of connection slots for them, not a maximum. It is a guarantee that this group
15564 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
15565 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
15566 individual host.
15567
15568 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
15569 set to 5, once there are 45 active connections (from any hosts), new
15570 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
15571 provided the other criteria for acceptance are met.
15572
15573
15574 .option smtp_active_hostname main string&!! unset
15575 .cindex "host" "name in SMTP responses"
15576 .cindex "SMTP" "host name in responses"
15577 .vindex "&$primary_hostname$&"
15578 This option is provided for multi-homed servers that want to masquerade as
15579 several different hosts. At the start of an incoming SMTP connection, its value
15580 is expanded and used instead of the value of &$primary_hostname$& in SMTP
15581 responses. For example, it is used as domain name in the response to an
15582 incoming HELO or EHLO command.
15583
15584 .vindex "&$smtp_active_hostname$&"
15585 The active hostname is placed in the &$smtp_active_hostname$& variable, which
15586 is saved with any messages that are received. It is therefore available for use
15587 in routers and transports when the message is later delivered.
15588
15589 If this option is unset, or if its expansion is forced to fail, or if the
15590 expansion results in an empty string, the value of &$primary_hostname$& is
15591 used. Other expansion failures cause a message to be written to the main and
15592 panic logs, and the SMTP command receives a temporary error. Typically, the
15593 value of &%smtp_active_hostname%& depends on the incoming interface address.
15594 For example:
15595 .code
15596 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
15597 {cox.mydomain}{box.mydomain}}
15598 .endd
15599
15600 Although &$smtp_active_hostname$& is primarily concerned with incoming
15601 messages, it is also used as the default for HELO commands in callout
15602 verification if there is no remote transport from which to obtain a
15603 &%helo_data%& value.
15604
15605 .option smtp_banner main string&!! "see below"
15606 .cindex "SMTP" "welcome banner"
15607 .cindex "banner for SMTP"
15608 .cindex "welcome banner for SMTP"
15609 .cindex "customizing" "SMTP banner"
15610 This string, which is expanded every time it is used, is output as the initial
15611 positive response to an SMTP connection. The default setting is:
15612 .code
15613 smtp_banner = $smtp_active_hostname ESMTP Exim \
15614 $version_number $tod_full
15615 .endd
15616 Failure to expand the string causes a panic error. If you want to create a
15617 multiline response to the initial SMTP connection, use &"\n"& in the string at
15618 appropriate points, but not at the end. Note that the 220 code is not included
15619 in this string. Exim adds it automatically (several times in the case of a
15620 multiline response).
15621
15622
15623 .option smtp_check_spool_space main boolean true
15624 .cindex "checking disk space"
15625 .cindex "disk space, checking"
15626 .cindex "spool directory" "checking space"
15627 When this option is set, if an incoming SMTP session encounters the SIZE
15628 option on a MAIL command, it checks that there is enough space in the
15629 spool directory's partition to accept a message of that size, while still
15630 leaving free the amount specified by &%check_spool_space%& (even if that value
15631 is zero). If there isn't enough space, a temporary error code is returned.
15632
15633
15634 .option smtp_connect_backlog main integer 20
15635 .cindex "connection backlog"
15636 .cindex "SMTP" "connection backlog"
15637 .cindex "backlog of connections"
15638 This option specifies a maximum number of waiting SMTP connections. Exim passes
15639 this value to the TCP/IP system when it sets up its listener. Once this number
15640 of connections are waiting for the daemon's attention, subsequent connection
15641 attempts are refused at the TCP/IP level. At least, that is what the manuals
15642 say; in some circumstances such connection attempts have been observed to time
15643 out instead. For large systems it is probably a good idea to increase the
15644 value (to 50, say). It also gives some protection against denial-of-service
15645 attacks by SYN flooding.
15646
15647
15648 .option smtp_enforce_sync main boolean true
15649 .cindex "SMTP" "synchronization checking"
15650 .cindex "synchronization checking in SMTP"
15651 The SMTP protocol specification requires the client to wait for a response from
15652 the server at certain points in the dialogue. Without PIPELINING these
15653 synchronization points are after every command; with PIPELINING they are
15654 fewer, but they still exist.
15655
15656 Some spamming sites send out a complete set of SMTP commands without waiting
15657 for any response. Exim protects against this by rejecting a message if the
15658 client has sent further input when it should not have. The error response &"554
15659 SMTP synchronization error"& is sent, and the connection is dropped. Testing
15660 for this error cannot be perfect because of transmission delays (unexpected
15661 input may be on its way but not yet received when Exim checks). However, it
15662 does detect many instances.
15663
15664 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
15665 If you want to disable the check selectively (for example, only for certain
15666 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
15667 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
15668
15669
15670
15671 .option smtp_etrn_command main string&!! unset
15672 .cindex "ETRN" "command to be run"
15673 .vindex "&$domain$&"
15674 If this option is set, the given command is run whenever an SMTP ETRN
15675 command is received from a host that is permitted to issue such commands (see
15676 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
15677 are independently expanded. The expansion variable &$domain$& is set to the
15678 argument of the ETRN command, and no syntax checking is done on it. For
15679 example:
15680 .code
15681 smtp_etrn_command = /etc/etrn_command $domain \
15682 $sender_host_address
15683 .endd
15684 A new process is created to run the command, but Exim does not wait for it to
15685 complete. Consequently, its status cannot be checked. If the command cannot be
15686 run, a line is written to the panic log, but the ETRN caller still receives
15687 a 250 success response. Exim is normally running under its own uid when
15688 receiving SMTP, so it is not possible for it to change the uid before running
15689 the command.
15690
15691
15692 .option smtp_etrn_serialize main boolean true
15693 .cindex "ETRN" "serializing"
15694 When this option is set, it prevents the simultaneous execution of more than
15695 one identical command as a result of ETRN in an SMTP connection. See
15696 section &<<SECTETRN>>& for details.
15697
15698
15699 .option smtp_load_reserve main fixed-point unset
15700 .cindex "load average"
15701 If the system load average ever gets higher than this, incoming SMTP calls are
15702 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
15703 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
15704 the load is over the limit. The option has no effect on ancient operating
15705 systems on which Exim cannot determine the load average. See also
15706 &%deliver_queue_load_max%& and &%queue_only_load%&.
15707
15708
15709
15710 .option smtp_max_synprot_errors main integer 3
15711 .cindex "SMTP" "limiting syntax and protocol errors"
15712 .cindex "limit" "SMTP syntax and protocol errors"
15713 Exim rejects SMTP commands that contain syntax or protocol errors. In
15714 particular, a syntactically invalid email address, as in this command:
15715 .code
15716 RCPT TO:<abc xyz@a.b.c>
15717 .endd
15718 causes immediate rejection of the command, before any other tests are done.
15719 (The ACL cannot be run if there is no valid address to set up for it.) An
15720 example of a protocol error is receiving RCPT before MAIL. If there are
15721 too many syntax or protocol errors in one SMTP session, the connection is
15722 dropped. The limit is set by this option.
15723
15724 .cindex "PIPELINING" "expected errors"
15725 When the PIPELINING extension to SMTP is in use, some protocol errors are
15726 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
15727 Exim assumes that PIPELINING will be used if it advertises it (see
15728 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
15729 not count towards the limit.
15730
15731
15732
15733 .option smtp_max_unknown_commands main integer 3
15734 .cindex "SMTP" "limiting unknown commands"
15735 .cindex "limit" "unknown SMTP commands"
15736 If there are too many unrecognized commands in an incoming SMTP session, an
15737 Exim server drops the connection. This is a defence against some kinds of abuse
15738 that subvert web
15739 clients
15740 into making connections to SMTP ports; in these circumstances, a number of
15741 non-SMTP command lines are sent first.
15742
15743
15744
15745 .option smtp_ratelimit_hosts main "host list&!!" unset
15746 .cindex "SMTP" "rate limiting"
15747 .cindex "limit" "rate of message arrival"
15748 .cindex "RCPT" "rate limiting"
15749 Some sites find it helpful to be able to limit the rate at which certain hosts
15750 can send them messages, and the rate at which an individual message can specify
15751 recipients.
15752
15753 Exim has two rate-limiting facilities. This section describes the older
15754 facility, which can limit rates within a single connection. The newer
15755 &%ratelimit%& ACL condition can limit rates across all connections. See section
15756 &<<SECTratelimiting>>& for details of the newer facility.
15757
15758 When a host matches &%smtp_ratelimit_hosts%&, the values of
15759 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
15760 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
15761 respectively. Each option, if set, must contain a set of four comma-separated
15762 values:
15763
15764 .ilist
15765 A threshold, before which there is no rate limiting.
15766 .next
15767 An initial time delay. Unlike other times in Exim, numbers with decimal
15768 fractional parts are allowed here.
15769 .next
15770 A factor by which to increase the delay each time.
15771 .next
15772 A maximum value for the delay. This should normally be less than 5 minutes,
15773 because after that time, the client is liable to timeout the SMTP command.
15774 .endlist
15775
15776 For example, these settings have been used successfully at the site which
15777 first suggested this feature, for controlling mail from their customers:
15778 .code
15779 smtp_ratelimit_mail = 2,0.5s,1.05,4m
15780 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
15781 .endd
15782 The first setting specifies delays that are applied to MAIL commands after
15783 two have been received over a single connection. The initial delay is 0.5
15784 seconds, increasing by a factor of 1.05 each time. The second setting applies
15785 delays to RCPT commands when more than four occur in a single message.
15786
15787
15788 .option smtp_ratelimit_mail main string unset
15789 See &%smtp_ratelimit_hosts%& above.
15790
15791
15792 .option smtp_ratelimit_rcpt main string unset
15793 See &%smtp_ratelimit_hosts%& above.
15794
15795
15796 .option smtp_receive_timeout main time 5m
15797 .cindex "timeout" "for SMTP input"
15798 .cindex "SMTP" "input timeout"
15799 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
15800 input, including batch SMTP. If a line of input (either an SMTP command or a
15801 data line) is not received within this time, the SMTP connection is dropped and
15802 the message is abandoned.
15803 A line is written to the log containing one of the following messages:
15804 .code
15805 SMTP command timeout on connection from...
15806 SMTP data timeout on connection from...
15807 .endd
15808 The former means that Exim was expecting to read an SMTP command; the latter
15809 means that it was in the DATA phase, reading the contents of a message.
15810
15811
15812 .oindex "&%-os%&"
15813 The value set by this option can be overridden by the
15814 &%-os%& command-line option. A setting of zero time disables the timeout, but
15815 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
15816 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
15817 timeout is controlled by &%receive_timeout%& and &%-or%&.
15818
15819
15820 .option smtp_reserve_hosts main "host list&!!" unset
15821 This option defines hosts for which SMTP connections are reserved; see
15822 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
15823
15824
15825 .option smtp_return_error_details main boolean false
15826 .cindex "SMTP" "details policy failures"
15827 .cindex "policy control" "rejection, returning details"
15828 In the default state, Exim uses bland messages such as
15829 &"Administrative prohibition"& when it rejects SMTP commands for policy
15830 reasons. Many sysadmins like this because it gives away little information
15831 to spammers. However, some other sysadmins who are applying strict checking
15832 policies want to give out much fuller information about failures. Setting
15833 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
15834 example, instead of &"Administrative prohibition"&, it might give:
15835 .code
15836 550-Rejected after DATA: '>' missing at end of address:
15837 550 failing address in "From" header is: <user@dom.ain
15838 .endd
15839
15840 .option spamd_address main string "see below"
15841 This option is available when Exim is compiled with the content-scanning
15842 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
15843 The default value is
15844 .code
15845 127.0.0.1 783
15846 .endd
15847 See section &<<SECTscanspamass>>& for more details.
15848
15849
15850
15851 .option split_spool_directory main boolean false
15852 .cindex "multiple spool directories"
15853 .cindex "spool directory" "split"
15854 .cindex "directories, multiple"
15855 If this option is set, it causes Exim to split its input directory into 62
15856 subdirectories, each with a single alphanumeric character as its name. The
15857 sixth character of the message id is used to allocate messages to
15858 subdirectories; this is the least significant base-62 digit of the time of
15859 arrival of the message.
15860
15861 Splitting up the spool in this way may provide better performance on systems
15862 where there are long mail queues, by reducing the number of files in any one
15863 directory. The msglog directory is also split up in a similar way to the input
15864 directory; however, if &%preserve_message_logs%& is set, all old msglog files
15865 are still placed in the single directory &_msglog.OLD_&.
15866
15867 It is not necessary to take any special action for existing messages when
15868 changing &%split_spool_directory%&. Exim notices messages that are in the
15869 &"wrong"& place, and continues to process them. If the option is turned off
15870 after a period of being on, the subdirectories will eventually empty and be
15871 automatically deleted.
15872
15873 When &%split_spool_directory%& is set, the behaviour of queue runner processes
15874 changes. Instead of creating a list of all messages in the queue, and then
15875 trying to deliver each one in turn, it constructs a list of those in one
15876 sub-directory and tries to deliver them, before moving on to the next
15877 sub-directory. The sub-directories are processed in a random order. This
15878 spreads out the scanning of the input directories, and uses less memory. It is
15879 particularly beneficial when there are lots of messages on the queue. However,
15880 if &%queue_run_in_order%& is set, none of this new processing happens. The
15881 entire queue has to be scanned and sorted before any deliveries can start.
15882
15883
15884 .option spool_directory main string&!! "set at compile time"
15885 .cindex "spool directory" "path to"
15886 This defines the directory in which Exim keeps its spool, that is, the messages
15887 it is waiting to deliver. The default value is taken from the compile-time
15888 configuration setting, if there is one. If not, this option must be set. The
15889 string is expanded, so it can contain, for example, a reference to
15890 &$primary_hostname$&.
15891
15892 If the spool directory name is fixed on your installation, it is recommended
15893 that you set it at build time rather than from this option, particularly if the
15894 log files are being written to the spool directory (see &%log_file_path%&).
15895 Otherwise log files cannot be used for errors that are detected early on, such
15896 as failures in the configuration file.
15897
15898 By using this option to override the compiled-in path, it is possible to run
15899 tests of Exim without using the standard spool.
15900
15901 .option sqlite_lock_timeout main time 5s
15902 .cindex "sqlite lookup type" "lock timeout"
15903 This option controls the timeout that the &(sqlite)& lookup uses when trying to
15904 access an SQLite database. See section &<<SECTsqlite>>& for more details.
15905
15906 .option strict_acl_vars main boolean false
15907 .cindex "&ACL;" "variables, handling unset"
15908 This option controls what happens if a syntactically valid but undefined ACL
15909 variable is referenced. If it is false (the default), an empty string
15910 is substituted; if it is true, an error is generated. See section
15911 &<<SECTaclvariables>>& for details of ACL variables.
15912
15913 .option strip_excess_angle_brackets main boolean false
15914 .cindex "angle brackets, excess"
15915 If this option is set, redundant pairs of angle brackets round &"route-addr"&
15916 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
15917 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
15918 passed on to another MTA, the excess angle brackets are not passed on. If this
15919 option is not set, multiple pairs of angle brackets cause a syntax error.
15920
15921
15922 .option strip_trailing_dot main boolean false
15923 .cindex "trailing dot on domain"
15924 .cindex "dot" "trailing on domain"
15925 If this option is set, a trailing dot at the end of a domain in an address is
15926 ignored. If this is in the envelope and the message is passed on to another
15927 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
15928 domain causes a syntax error.
15929 However, addresses in header lines are checked only when an ACL requests header
15930 syntax checking.
15931
15932
15933 .option syslog_duplication main boolean true
15934 .cindex "syslog" "duplicate log lines; suppressing"
15935 When Exim is logging to syslog, it writes the log lines for its three
15936 separate logs at different syslog priorities so that they can in principle
15937 be separated on the logging hosts. Some installations do not require this
15938 separation, and in those cases, the duplication of certain log lines is a
15939 nuisance. If &%syslog_duplication%& is set false, only one copy of any
15940 particular log line is written to syslog. For lines that normally go to
15941 both the main log and the reject log, the reject log version (possibly
15942 containing message header lines) is written, at LOG_NOTICE priority.
15943 Lines that normally go to both the main and the panic log are written at
15944 the LOG_ALERT priority.
15945
15946
15947 .option syslog_facility main string unset
15948 .cindex "syslog" "facility; setting"
15949 This option sets the syslog &"facility"& name, used when Exim is logging to
15950 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
15951 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
15952 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
15953 details of Exim's logging.
15954
15955
15956
15957 .option syslog_processname main string &`exim`&
15958 .cindex "syslog" "process name; setting"
15959 This option sets the syslog &"ident"& name, used when Exim is logging to
15960 syslog. The value must be no longer than 32 characters. See chapter
15961 &<<CHAPlog>>& for details of Exim's logging.
15962
15963
15964
15965 .option syslog_timestamp main boolean true
15966 .cindex "syslog" "timestamps"
15967 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
15968 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
15969 details of Exim's logging.
15970
15971
15972 .option system_filter main string&!! unset
15973 .cindex "filter" "system filter"
15974 .cindex "system filter" "specifying"
15975 .cindex "Sieve filter" "not available for system filter"
15976 This option specifies an Exim filter file that is applied to all messages at
15977 the start of each delivery attempt, before any routing is done. System filters
15978 must be Exim filters; they cannot be Sieve filters. If the system filter
15979 generates any deliveries to files or pipes, or any new mail messages, the
15980 appropriate &%system_filter_..._transport%& option(s) must be set, to define
15981 which transports are to be used. Details of this facility are given in chapter
15982 &<<CHAPsystemfilter>>&.
15983
15984
15985 .option system_filter_directory_transport main string&!! unset
15986 .vindex "&$address_file$&"
15987 This sets the name of the transport driver that is to be used when the
15988 &%save%& command in a system message filter specifies a path ending in &"/"&,
15989 implying delivery of each message into a separate file in some directory.
15990 During the delivery, the variable &$address_file$& contains the path name.
15991
15992
15993 .option system_filter_file_transport main string&!! unset
15994 .cindex "file" "transport for system filter"
15995 This sets the name of the transport driver that is to be used when the &%save%&
15996 command in a system message filter specifies a path not ending in &"/"&. During
15997 the delivery, the variable &$address_file$& contains the path name.
15998
15999 .option system_filter_group main string unset
16000 .cindex "gid (group id)" "system filter"
16001 This option is used only when &%system_filter_user%& is also set. It sets the
16002 gid under which the system filter is run, overriding any gid that is associated
16003 with the user. The value may be numerical or symbolic.
16004
16005 .option system_filter_pipe_transport main string&!! unset
16006 .cindex "&(pipe)& transport" "for system filter"
16007 .vindex "&$address_pipe$&"
16008 This specifies the transport driver that is to be used when a &%pipe%& command
16009 is used in a system filter. During the delivery, the variable &$address_pipe$&
16010 contains the pipe command.
16011
16012
16013 .option system_filter_reply_transport main string&!! unset
16014 .cindex "&(autoreply)& transport" "for system filter"
16015 This specifies the transport driver that is to be used when a &%mail%& command
16016 is used in a system filter.
16017
16018
16019 .option system_filter_user main string unset
16020 .cindex "uid (user id)" "system filter"
16021 If this option is set to root, the system filter is run in the main Exim
16022 delivery process, as root. Otherwise, the system filter runs in a separate
16023 process, as the given user, defaulting to the Exim run-time user.
16024 Unless the string consists entirely of digits, it
16025 is looked up in the password data. Failure to find the named user causes a
16026 configuration error. The gid is either taken from the password data, or
16027 specified by &%system_filter_group%&. When the uid is specified numerically,
16028 &%system_filter_group%& is required to be set.
16029
16030 If the system filter generates any pipe, file, or reply deliveries, the uid
16031 under which the filter is run is used when transporting them, unless a
16032 transport option overrides.
16033
16034
16035 .option tcp_nodelay main boolean true
16036 .cindex "daemon" "TCP_NODELAY on sockets"
16037 .cindex "Nagle algorithm"
16038 .cindex "TCP_NODELAY on listening sockets"
16039 If this option is set false, it stops the Exim daemon setting the
16040 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
16041 turns off the &"Nagle algorithm"&, which is a way of improving network
16042 performance in interactive (character-by-character) situations. Turning it off
16043 should improve Exim's performance a bit, so that is what happens by default.
16044 However, it appears that some broken clients cannot cope, and time out. Hence
16045 this option. It affects only those sockets that are set up for listening by the
16046 daemon. Sockets created by the smtp transport for delivering mail always set
16047 TCP_NODELAY.
16048
16049
16050 .option timeout_frozen_after main time 0s
16051 .cindex "frozen messages" "timing out"
16052 .cindex "timeout" "frozen messages"
16053 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
16054 message of any kind that has been on the queue for longer than the given time
16055 is automatically cancelled at the next queue run. If the frozen message is a
16056 bounce message, it is just discarded; otherwise, a bounce is sent to the
16057 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
16058 If you want to timeout frozen bounce messages earlier than other kinds of
16059 frozen message, see &%ignore_bounce_errors_after%&.
16060
16061 &*Note:*& the default value of zero means no timeouts; with this setting,
16062 frozen messages remain on the queue forever (except for any frozen bounce
16063 messages that are released by &%ignore_bounce_errors_after%&).
16064
16065
16066 .option timezone main string unset
16067 .cindex "timezone, setting"
16068 The value of &%timezone%& is used to set the environment variable TZ while
16069 running Exim (if it is different on entry). This ensures that all timestamps
16070 created by Exim are in the required timezone. If you want all your timestamps
16071 to be in UTC (aka GMT) you should set
16072 .code
16073 timezone = UTC
16074 .endd
16075 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
16076 or, if that is not set, from the value of the TZ environment variable when Exim
16077 is built. If &%timezone%& is set to the empty string, either at build or run
16078 time, any existing TZ variable is removed from the environment when Exim
16079 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
16080 unfortunately not all, operating systems.
16081
16082
16083 .option tls_advertise_hosts main "host list&!!" unset
16084 .cindex "TLS" "advertising"
16085 .cindex "encryption" "on SMTP connection"
16086 .cindex "SMTP" "encrypted connection"
16087 When Exim is built with support for TLS encrypted connections, the availability
16088 of the STARTTLS command to set up an encrypted session is advertised in
16089 response to EHLO only to those client hosts that match this option. See
16090 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
16091
16092
16093 .option tls_certificate main string&!! unset
16094 .cindex "TLS" "server certificate; location of"
16095 .cindex "certificate" "server, location of"
16096 The value of this option is expanded, and must then be the absolute path to a
16097 file which contains the server's certificates. The server's private key is also
16098 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
16099 &<<CHAPTLS>>& for further details.
16100
16101 &*Note*&: The certificates defined by this option are used only when Exim is
16102 receiving incoming messages as a server. If you want to supply certificates for
16103 use when sending messages as a client, you must set the &%tls_certificate%&
16104 option in the relevant &(smtp)& transport.
16105
16106 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
16107 if the OpenSSL build supports TLS extensions and the TLS client sends the
16108 Server Name Indication extension, then this option and others documented in
16109 &<<SECTtlssni>>& will be re-expanded.
16110
16111 .option tls_crl main string&!! unset
16112 .cindex "TLS" "server certificate revocation list"
16113 .cindex "certificate" "revocation list for server"
16114 This option specifies a certificate revocation list. The expanded value must
16115 be the name of a file that contains a CRL in PEM format.
16116
16117 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
16118
16119
16120 .option tls_dh_max_bits main integer 2236
16121 .cindex "TLS" "D-H bit count"
16122 The number of bits used for Diffie-Hellman key-exchange may be suggested by
16123 the chosen TLS library. That value might prove to be too high for
16124 interoperability. This option provides a maximum clamp on the value
16125 suggested, trading off security for interoperability.
16126
16127 The value must be at least 1024.
16128
16129 The value 2236 was chosen because, at time of adding the option, it was the
16130 hard-coded maximum value supported by the NSS cryptographic library, as used
16131 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
16132
16133 If you prefer more security and are willing to break some clients, raise this
16134 number.
16135
16136 Note that the value passed to GnuTLS for *generating* a new prime may be a
16137 little less than this figure, because GnuTLS is inexact and may produce a
16138 larger prime than requested.
16139
16140
16141 .option tls_dhparam main string&!! unset
16142 .cindex "TLS" "D-H parameters for server"
16143 The value of this option is expanded and indicates the source of DH parameters
16144 to be used by Exim.
16145
16146 If it is a filename starting with a &`/`&, then it names a file from which DH
16147 parameters should be loaded. If the file exists, it should hold a PEM-encoded
16148 PKCS#3 representation of the DH prime. If the file does not exist, for
16149 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
16150 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
16151 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
16152 and treated as though the &%tls_dhparam%& were set to "none".
16153
16154 If this option expands to the string "none", then no DH parameters will be
16155 loaded by Exim.
16156
16157 If this option expands to the string "historic" and Exim is using GnuTLS, then
16158 Exim will attempt to load a file from inside the spool directory. If the file
16159 does not exist, Exim will attempt to create it.
16160 See section &<<SECTgnutlsparam>>& for further details.
16161
16162 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
16163 a default DH prime; the default is the 2048 bit prime described in section
16164 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
16165 in IKE is assigned number 23.
16166
16167 Otherwise, the option must expand to the name used by Exim for any of a number
16168 of DH primes specified in RFC 2409, RFC 3526 and RFC 5114. As names, Exim uses
16169 "ike" followed by the number used by IKE, of "default" which corresponds to
16170 "ike23".
16171
16172 The available primes are:
16173 &`ike1`&, &`ike2`&, &`ike5`&,
16174 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
16175 &`ike22`&, &`ike23`& (aka &`default`&) and &`ike24`&.
16176
16177 Some of these will be too small to be accepted by clients.
16178 Some may be too large to be accepted by clients.
16179
16180 The TLS protocol does not negotiate an acceptable size for this; clients tend
16181 to hard-drop connections if what is offered by the server is unacceptable,
16182 whether too large or too small, and there's no provision for the client to
16183 tell the server what these constraints are. Thus, as a server operator, you
16184 need to make an educated guess as to what is most likely to work for your
16185 userbase.
16186
16187 Some known size constraints suggest that a bit-size in the range 2048 to 2236
16188 is most likely to maximise interoperability. The upper bound comes from
16189 applications using the Mozilla Network Security Services (NSS) library, which
16190 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
16191 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
16192 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
16193 acceptable bound from 1024 to 2048.
16194
16195
16196 .option tls_on_connect_ports main "string list" unset
16197 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
16198 operate the obsolete SSMTP (SMTPS) protocol, where a TLS session is immediately
16199 set up without waiting for the client to issue a STARTTLS command. For
16200 further details, see section &<<SECTsupobssmt>>&.
16201
16202
16203
16204 .option tls_privatekey main string&!! unset
16205 .cindex "TLS" "server private key; location of"
16206 The value of this option is expanded, and must then be the absolute path to a
16207 file which contains the server's private key. If this option is unset, or if
16208 the expansion is forced to fail, or the result is an empty string, the private
16209 key is assumed to be in the same file as the server's certificates. See chapter
16210 &<<CHAPTLS>>& for further details.
16211
16212 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
16213
16214
16215 .option tls_remember_esmtp main boolean false
16216 .cindex "TLS" "esmtp state; remembering"
16217 .cindex "TLS" "broken clients"
16218 If this option is set true, Exim violates the RFCs by remembering that it is in
16219 &"esmtp"& state after successfully negotiating a TLS session. This provides
16220 support for broken clients that fail to send a new EHLO after starting a
16221 TLS session.
16222
16223
16224 .option tls_require_ciphers main string&!! unset
16225 .cindex "TLS" "requiring specific ciphers"
16226 .cindex "cipher" "requiring specific"
16227 This option controls which ciphers can be used for incoming TLS connections.
16228 The &(smtp)& transport has an option of the same name for controlling outgoing
16229 connections. This option is expanded for each connection, so can be varied for
16230 different clients if required. The value of this option must be a list of
16231 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
16232 in somewhat different ways. If GnuTLS is being used, the client controls the
16233 preference order of the available ciphers. Details are given in sections
16234 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
16235
16236
16237 .option tls_try_verify_hosts main "host list&!!" unset
16238 .cindex "TLS" "client certificate verification"
16239 .cindex "certificate" "verification of client"
16240 See &%tls_verify_hosts%& below.
16241
16242
16243 .option tls_verify_certificates main string&!! unset
16244 .cindex "TLS" "client certificate verification"
16245 .cindex "certificate" "verification of client"
16246 The value of this option is expanded, and must then be the absolute path to
16247 a file containing permitted certificates for clients that
16248 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&. Alternatively, if you
16249 are using OpenSSL, you can set &%tls_verify_certificates%& to the name of a
16250 directory containing certificate files. This does not work with GnuTLS; the
16251 option must be set to the name of a single file if you are using GnuTLS.
16252
16253 These certificates should be for the certificate authorities trusted, rather
16254 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
16255 the value is a file then the certificates are sent by Exim as a server to
16256 connecting clients, defining the list of accepted certificate authorities.
16257 Thus the values defined should be considered public data. To avoid this,
16258 use OpenSSL with a directory.
16259
16260 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
16261
16262 A forced expansion failure or setting to an empty string is equivalent to
16263 being unset.
16264
16265
16266 .option tls_verify_hosts main "host list&!!" unset
16267 .cindex "TLS" "client certificate verification"
16268 .cindex "certificate" "verification of client"
16269 This option, along with &%tls_try_verify_hosts%&, controls the checking of
16270 certificates from clients. The expected certificates are defined by
16271 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
16272 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
16273 &%tls_verify_certificates%& is not set.
16274
16275 Any client that matches &%tls_verify_hosts%& is constrained by
16276 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
16277 present one of the listed certificates. If it does not, the connection is
16278 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
16279 the host to use TLS. It can still send SMTP commands through unencrypted
16280 connections. Forcing a client to use TLS has to be done separately using an
16281 ACL to reject inappropriate commands when the connection is not encrypted.
16282
16283 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
16284 matches this option (but not &%tls_verify_hosts%&), Exim requests a
16285 certificate and checks it against &%tls_verify_certificates%&, but does not
16286 abort the connection if there is no certificate or if it does not match. This
16287 state can be detected in an ACL, which makes it possible to implement policies
16288 such as &"accept for relay only if a verified certificate has been received,
16289 but accept for local delivery if encrypted, even without a verified
16290 certificate"&.
16291
16292 Client hosts that match neither of these lists are not asked to present
16293 certificates.
16294
16295
16296 .option trusted_groups main "string list&!!" unset
16297 .cindex "trusted groups"
16298 .cindex "groups" "trusted"
16299 This option is expanded just once, at the start of Exim's processing. If this
16300 option is set, any process that is running in one of the listed groups, or
16301 which has one of them as a supplementary group, is trusted. The groups can be
16302 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
16303 details of what trusted callers are permitted to do. If neither
16304 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
16305 are trusted.
16306
16307 .option trusted_users main "string list&!!" unset
16308 .cindex "trusted users"
16309 .cindex "user" "trusted"
16310 This option is expanded just once, at the start of Exim's processing. If this
16311 option is set, any process that is running as one of the listed users is
16312 trusted. The users can be specified numerically or by name. See section
16313 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
16314 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
16315 Exim user are trusted.
16316
16317 .option unknown_login main string&!! unset
16318 .cindex "uid (user id)" "unknown caller"
16319 .vindex "&$caller_uid$&"
16320 This is a specialized feature for use in unusual configurations. By default, if
16321 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
16322 gives up. The &%unknown_login%& option can be used to set a login name to be
16323 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
16324 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
16325 is used for the user's real name (gecos field), unless this has been set by the
16326 &%-F%& option.
16327
16328 .option unknown_username main string unset
16329 See &%unknown_login%&.
16330
16331 .option untrusted_set_sender main "address list&!!" unset
16332 .cindex "trusted users"
16333 .cindex "sender" "setting by untrusted user"
16334 .cindex "untrusted user setting sender"
16335 .cindex "user" "untrusted setting sender"
16336 .cindex "envelope sender"
16337 When an untrusted user submits a message to Exim using the standard input, Exim
16338 normally creates an envelope sender address from the user's login and the
16339 default qualification domain. Data from the &%-f%& option (for setting envelope
16340 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
16341 is used) is ignored.
16342
16343 However, untrusted users are permitted to set an empty envelope sender address,
16344 to declare that a message should never generate any bounces. For example:
16345 .code
16346 exim -f '<>' user@domain.example
16347 .endd
16348 .vindex "&$sender_ident$&"
16349 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
16350 other envelope sender addresses in a controlled way. When it is set, untrusted
16351 users are allowed to set envelope sender addresses that match any of the
16352 patterns in the list. Like all address lists, the string is expanded. The
16353 identity of the user is in &$sender_ident$&, so you can, for example, restrict
16354 users to setting senders that start with their login ids
16355 followed by a hyphen
16356 by a setting like this:
16357 .code
16358 untrusted_set_sender = ^$sender_ident-
16359 .endd
16360 If you want to allow untrusted users to set envelope sender addresses without
16361 restriction, you can use
16362 .code
16363 untrusted_set_sender = *
16364 .endd
16365 The &%untrusted_set_sender%& option applies to all forms of local input, but
16366 only to the setting of the envelope sender. It does not permit untrusted users
16367 to use the other options which trusted user can use to override message
16368 parameters. Furthermore, it does not stop Exim from removing an existing
16369 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
16370 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
16371 overriding these actions. The handling of the &'Sender:'& header is also
16372 described in section &<<SECTthesenhea>>&.
16373
16374 The log line for a message's arrival shows the envelope sender following
16375 &"<="&. For local messages, the user's login always follows, after &"U="&. In
16376 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
16377 envelope sender address, the user's login is shown in parentheses after the
16378 sender address.
16379
16380
16381 .option uucp_from_pattern main string "see below"
16382 .cindex "&""From""& line"
16383 .cindex "UUCP" "&""From""& line"
16384 Some applications that pass messages to an MTA via a command line interface use
16385 an initial line starting with &"From&~"& to pass the envelope sender. In
16386 particular, this is used by UUCP software. Exim recognizes such a line by means
16387 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
16388 matches, the sender address is constructed by expanding the contents of
16389 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
16390 default pattern recognizes lines in the following two forms:
16391 .code
16392 From ph10 Fri Jan 5 12:35 GMT 1996
16393 From ph10 Fri, 7 Jan 97 14:00:00 GMT
16394 .endd
16395 The pattern can be seen by running
16396 .code
16397 exim -bP uucp_from_pattern
16398 .endd
16399 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
16400 year in the second case. The first word after &"From&~"& is matched in the
16401 regular expression by a parenthesized subpattern. The default value for
16402 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
16403 (&"ph10"& in the example above) as the message's sender. See also
16404 &%ignore_fromline_hosts%&.
16405
16406
16407 .option uucp_from_sender main string&!! &`$1`&
16408 See &%uucp_from_pattern%& above.
16409
16410
16411 .option warn_message_file main string unset
16412 .cindex "warning of delay" "customizing the message"
16413 .cindex "customizing" "warning message"
16414 This option defines a template file containing paragraphs of text to be used
16415 for constructing the warning message which is sent by Exim when a message has
16416 been on the queue for a specified amount of time, as specified by
16417 &%delay_warning%&. Details of the file's contents are given in chapter
16418 &<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
16419
16420
16421 .option write_rejectlog main boolean true
16422 .cindex "reject log" "disabling"
16423 If this option is set false, Exim no longer writes anything to the reject log.
16424 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
16425 .ecindex IIDconfima
16426 .ecindex IIDmaiconf
16427
16428
16429
16430
16431 . ////////////////////////////////////////////////////////////////////////////
16432 . ////////////////////////////////////////////////////////////////////////////
16433
16434 .chapter "Generic options for routers" "CHAProutergeneric"
16435 .scindex IIDgenoprou1 "options" "generic; for routers"
16436 .scindex IIDgenoprou2 "generic options" "router"
16437 This chapter describes the generic options that apply to all routers.
16438 Those that are preconditions are marked with &Dagger; in the &"use"& field.
16439
16440 For a general description of how a router operates, see sections
16441 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
16442 which the preconditions are tested. The order of expansion of the options that
16443 provide data for a transport is: &%errors_to%&, &%headers_add%&,
16444 &%headers_remove%&, &%transport%&.
16445
16446
16447
16448 .option address_data routers string&!! unset
16449 .cindex "router" "data attached to address"
16450 The string is expanded just before the router is run, that is, after all the
16451 precondition tests have succeeded. If the expansion is forced to fail, the
16452 router declines, the value of &%address_data%& remains unchanged, and the
16453 &%more%& option controls what happens next. Other expansion failures cause
16454 delivery of the address to be deferred.
16455
16456 .vindex "&$address_data$&"
16457 When the expansion succeeds, the value is retained with the address, and can be
16458 accessed using the variable &$address_data$& in the current router, subsequent
16459 routers, and the eventual transport.
16460
16461 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
16462 that runs a user's filter file, the contents of &$address_data$& are accessible
16463 in the filter. This is not normally a problem, because such data is usually
16464 either not confidential or it &"belongs"& to the current user, but if you do
16465 put confidential data into &$address_data$& you need to remember this point.
16466
16467 Even if the router declines or passes, the value of &$address_data$& remains
16468 with the address, though it can be changed by another &%address_data%& setting
16469 on a subsequent router. If a router generates child addresses, the value of
16470 &$address_data$& propagates to them. This also applies to the special kind of
16471 &"child"& that is generated by a router with the &%unseen%& option.
16472
16473 The idea of &%address_data%& is that you can use it to look up a lot of data
16474 for the address once, and then pick out parts of the data later. For example,
16475 you could use a single LDAP lookup to return a string of the form
16476 .code
16477 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
16478 .endd
16479 In the transport you could pick out the mailbox by a setting such as
16480 .code
16481 file = ${extract{mailbox}{$address_data}}
16482 .endd
16483 This makes the configuration file less messy, and also reduces the number of
16484 lookups (though Exim does cache lookups).
16485
16486 .vindex "&$sender_address_data$&"
16487 .vindex "&$address_data$&"
16488 The &%address_data%& facility is also useful as a means of passing information
16489 from one router to another, and from a router to a transport. In addition, if
16490 &$address_data$& is set by a router when verifying a recipient address from an
16491 ACL, it remains available for use in the rest of the ACL statement. After
16492 verifying a sender, the value is transferred to &$sender_address_data$&.
16493
16494
16495
16496 .option address_test routers&!? boolean true
16497 .oindex "&%-bt%&"
16498 .cindex "router" "skipping when address testing"
16499 If this option is set false, the router is skipped when routing is being tested
16500 by means of the &%-bt%& command line option. This can be a convenience when
16501 your first router sends messages to an external scanner, because it saves you
16502 having to set the &"already scanned"& indicator when testing real address
16503 routing.
16504
16505
16506
16507 .option cannot_route_message routers string&!! unset
16508 .cindex "router" "customizing &""cannot route""& message"
16509 .cindex "customizing" "&""cannot route""& message"
16510 This option specifies a text message that is used when an address cannot be
16511 routed because Exim has run out of routers. The default message is
16512 &"Unrouteable address"&. This option is useful only on routers that have
16513 &%more%& set false, or on the very last router in a configuration, because the
16514 value that is used is taken from the last router that is considered. This
16515 includes a router that is skipped because its preconditions are not met, as
16516 well as a router that declines. For example, using the default configuration,
16517 you could put:
16518 .code
16519 cannot_route_message = Remote domain not found in DNS
16520 .endd
16521 on the first router, which is a &(dnslookup)& router with &%more%& set false,
16522 and
16523 .code
16524 cannot_route_message = Unknown local user
16525 .endd
16526 on the final router that checks for local users. If string expansion fails for
16527 this option, the default message is used. Unless the expansion failure was
16528 explicitly forced, a message about the failure is written to the main and panic
16529 logs, in addition to the normal message about the routing failure.
16530
16531
16532 .option caseful_local_part routers boolean false
16533 .cindex "case of local parts"
16534 .cindex "router" "case of local parts"
16535 By default, routers handle the local parts of addresses in a case-insensitive
16536 manner, though the actual case is preserved for transmission with the message.
16537 If you want the case of letters to be significant in a router, you must set
16538 this option true. For individual router options that contain address or local
16539 part lists (for example, &%local_parts%&), case-sensitive matching can be
16540 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
16541 more details.
16542
16543 .vindex "&$local_part$&"
16544 .vindex "&$original_local_part$&"
16545 .vindex "&$parent_local_part$&"
16546 The value of the &$local_part$& variable is forced to lower case while a
16547 router is running unless &%caseful_local_part%& is set. When a router assigns
16548 an address to a transport, the value of &$local_part$& when the transport runs
16549 is the same as it was in the router. Similarly, when a router generates child
16550 addresses by aliasing or forwarding, the values of &$original_local_part$&
16551 and &$parent_local_part$& are those that were used by the redirecting router.
16552
16553 This option applies to the processing of an address by a router. When a
16554 recipient address is being processed in an ACL, there is a separate &%control%&
16555 modifier that can be used to specify case-sensitive processing within the ACL
16556 (see section &<<SECTcontrols>>&).
16557
16558
16559
16560 .option check_local_user routers&!? boolean false
16561 .cindex "local user, checking in router"
16562 .cindex "router" "checking for local user"
16563 .cindex "&_/etc/passwd_&"
16564 .vindex "&$home$&"
16565 When this option is true, Exim checks that the local part of the recipient
16566 address (with affixes removed if relevant) is the name of an account on the
16567 local system. The check is done by calling the &[getpwnam()]& function rather
16568 than trying to read &_/etc/passwd_& directly. This means that other methods of
16569 holding password data (such as NIS) are supported. If the local part is a local
16570 user, &$home$& is set from the password data, and can be tested in other
16571 preconditions that are evaluated after this one (the order of evaluation is
16572 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
16573 overridden by &%router_home_directory%&. If the local part is not a local user,
16574 the router is skipped.
16575
16576 If you want to check that the local part is either the name of a local user
16577 or matches something else, you cannot combine &%check_local_user%& with a
16578 setting of &%local_parts%&, because that specifies the logical &'and'& of the
16579 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
16580 setting to achieve this. For example:
16581 .code
16582 local_parts = passwd;$local_part : lsearch;/etc/other/users
16583 .endd
16584 Note, however, that the side effects of &%check_local_user%& (such as setting
16585 up a home directory) do not occur when a &(passwd)& lookup is used in a
16586 &%local_parts%& (or any other) precondition.
16587
16588
16589
16590 .option condition routers&!? string&!! unset
16591 .cindex "router" "customized precondition"
16592 This option specifies a general precondition test that has to succeed for the
16593 router to be called. The &%condition%& option is the last precondition to be
16594 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
16595 result is a forced failure, or an empty string, or one of the strings &"0"& or
16596 &"no"& or &"false"& (checked without regard to the case of the letters), the
16597 router is skipped, and the address is offered to the next one.
16598
16599 If the result is any other value, the router is run (as this is the last
16600 precondition to be evaluated, all the other preconditions must be true).
16601
16602 This option is unusual in that multiple &%condition%& options may be present.
16603 All &%condition%& options must succeed.
16604
16605 The &%condition%& option provides a means of applying custom conditions to the
16606 running of routers. Note that in the case of a simple conditional expansion,
16607 the default expansion values are exactly what is wanted. For example:
16608 .code
16609 condition = ${if >{$message_age}{600}}
16610 .endd
16611 Because of the default behaviour of the string expansion, this is equivalent to
16612 .code
16613 condition = ${if >{$message_age}{600}{true}{}}
16614 .endd
16615
16616 A multiple condition example, which succeeds:
16617 .code
16618 condition = ${if >{$message_age}{600}}
16619 condition = ${if !eq{${lc:$local_part}}{postmaster}}
16620 condition = foobar
16621 .endd
16622
16623 If the expansion fails (other than forced failure) delivery is deferred. Some
16624 of the other precondition options are common special cases that could in fact
16625 be specified using &%condition%&.
16626
16627
16628 .option debug_print routers string&!! unset
16629 .cindex "testing" "variables in drivers"
16630 If this option is set and debugging is enabled (see the &%-d%& command line
16631 option) or in address-testing mode (see the &%-bt%& command line option),
16632 the string is expanded and included in the debugging output.
16633 If expansion of the string fails, the error message is written to the debugging
16634 output, and Exim carries on processing.
16635 This option is provided to help with checking out the values of variables and
16636 so on when debugging router configurations. For example, if a &%condition%&
16637 option appears not to be working, &%debug_print%& can be used to output the
16638 variables it references. The output happens after checks for &%domains%&,
16639 &%local_parts%&, and &%check_local_user%& but before any other preconditions
16640 are tested. A newline is added to the text if it does not end with one.
16641 The variable &$router_name$& contains the name of the router.
16642
16643
16644
16645 .option disable_logging routers boolean false
16646 If this option is set true, nothing is logged for any routing errors
16647 or for any deliveries caused by this router. You should not set this option
16648 unless you really, really know what you are doing. See also the generic
16649 transport option of the same name.
16650
16651
16652 .option domains routers&!? "domain list&!!" unset
16653 .cindex "router" "restricting to specific domains"
16654 .vindex "&$domain_data$&"
16655 If this option is set, the router is skipped unless the current domain matches
16656 the list. If the match is achieved by means of a file lookup, the data that the
16657 lookup returned for the domain is placed in &$domain_data$& for use in string
16658 expansions of the driver's private options. See section &<<SECTrouprecon>>& for
16659 a list of the order in which preconditions are evaluated.
16660
16661
16662
16663 .option driver routers string unset
16664 This option must always be set. It specifies which of the available routers is
16665 to be used.
16666
16667
16668
16669 .option errors_to routers string&!! unset
16670 .cindex "envelope sender"
16671 .cindex "router" "changing address for errors"
16672 If a router successfully handles an address, it may assign the address to a
16673 transport for delivery or it may generate child addresses. In both cases, if
16674 there is a delivery problem during later processing, the resulting bounce
16675 message is sent to the address that results from expanding this string,
16676 provided that the address verifies successfully. The &%errors_to%& option is
16677 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
16678
16679 The &%errors_to%& setting associated with an address can be overridden if it
16680 subsequently passes through other routers that have their own &%errors_to%&
16681 settings, or if the message is delivered by a transport with a &%return_path%&
16682 setting.
16683
16684 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
16685 the expansion fails to verify, the errors address associated with the incoming
16686 address is used. At top level, this is the envelope sender. A non-forced
16687 expansion failure causes delivery to be deferred.
16688
16689 If an address for which &%errors_to%& has been set ends up being delivered over
16690 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
16691 any bounces that are generated by other MTAs on the delivery route are also
16692 sent there. You can set &%errors_to%& to the empty string by either of these
16693 settings:
16694 .code
16695 errors_to =
16696 errors_to = ""
16697 .endd
16698 An expansion item that yields an empty string has the same effect. If you do
16699 this, a locally detected delivery error for addresses processed by this router
16700 no longer gives rise to a bounce message; the error is discarded. If the
16701 address is delivered to a remote host, the return path is set to &`<>`&, unless
16702 overridden by the &%return_path%& option on the transport.
16703
16704 .vindex "&$address_data$&"
16705 If for some reason you want to discard local errors, but use a non-empty
16706 MAIL command for remote delivery, you can preserve the original return
16707 path in &$address_data$& in the router, and reinstate it in the transport by
16708 setting &%return_path%&.
16709
16710 The most common use of &%errors_to%& is to direct mailing list bounces to the
16711 manager of the list, as described in section &<<SECTmailinglists>>&, or to
16712 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
16713
16714
16715
16716 .option expn routers&!? boolean true
16717 .cindex "address" "testing"
16718 .cindex "testing" "addresses"
16719 .cindex "EXPN" "router skipping"
16720 .cindex "router" "skipping for EXPN"
16721 If this option is turned off, the router is skipped when testing an address
16722 as a result of processing an SMTP EXPN command. You might, for example,
16723 want to turn it off on a router for users' &_.forward_& files, while leaving it
16724 on for the system alias file.
16725 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16726 are evaluated.
16727
16728 The use of the SMTP EXPN command is controlled by an ACL (see chapter
16729 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
16730 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
16731
16732
16733
16734 .option fail_verify routers boolean false
16735 .cindex "router" "forcing verification failure"
16736 Setting this option has the effect of setting both &%fail_verify_sender%& and
16737 &%fail_verify_recipient%& to the same value.
16738
16739
16740
16741 .option fail_verify_recipient routers boolean false
16742 If this option is true and an address is accepted by this router when
16743 verifying a recipient, verification fails.
16744
16745
16746
16747 .option fail_verify_sender routers boolean false
16748 If this option is true and an address is accepted by this router when
16749 verifying a sender, verification fails.
16750
16751
16752
16753 .option fallback_hosts routers "string list" unset
16754 .cindex "router" "fallback hosts"
16755 .cindex "fallback" "hosts specified on router"
16756 String expansion is not applied to this option. The argument must be a
16757 colon-separated list of host names or IP addresses. The list separator can be
16758 changed (see section &<<SECTlistconstruct>>&), and a port can be specified with
16759 each name or address. In fact, the format of each item is exactly the same as
16760 defined for the list of hosts in a &(manualroute)& router (see section
16761 &<<SECTformatonehostitem>>&).
16762
16763 If a router queues an address for a remote transport, this host list is
16764 associated with the address, and used instead of the transport's fallback host
16765 list. If &%hosts_randomize%& is set on the transport, the order of the list is
16766 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
16767 transport for further details.
16768
16769
16770 .option group routers string&!! "see below"
16771 .cindex "gid (group id)" "local delivery"
16772 .cindex "local transports" "uid and gid"
16773 .cindex "transport" "local"
16774 .cindex "router" "setting group"
16775 When a router queues an address for a transport, and the transport does not
16776 specify a group, the group given here is used when running the delivery
16777 process.
16778 The group may be specified numerically or by name. If expansion fails, the
16779 error is logged and delivery is deferred.
16780 The default is unset, unless &%check_local_user%& is set, when the default
16781 is taken from the password information. See also &%initgroups%& and &%user%&
16782 and the discussion in chapter &<<CHAPenvironment>>&.
16783
16784
16785
16786 .option headers_add routers list&!! unset
16787 .cindex "header lines" "adding"
16788 .cindex "router" "adding header lines"
16789 This option specifies a list of text headers, newline-separated,
16790 that is associated with any addresses that are accepted by the router.
16791 Each item is separately expanded, at routing time. However, this
16792 option has no effect when an address is just being verified. The way in which
16793 the text is used to add header lines at transport time is described in section
16794 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
16795 message is in the process of being transported. This means that references to
16796 header lines in string expansions in the transport's configuration do not
16797 &"see"& the added header lines.
16798
16799 The &%headers_add%& option is expanded after &%errors_to%&, but before
16800 &%headers_remove%& and &%transport%&. If an item is empty, or if
16801 an item expansion is forced to fail, the item has no effect. Other expansion
16802 failures are treated as configuration errors.
16803
16804 Unlike most options, &%headers_add%& can be specified multiple times
16805 for a router; all listed headers are added.
16806
16807 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
16808 router that has the &%one_time%& option set.
16809
16810 .cindex "duplicate addresses"
16811 .oindex "&%unseen%&"
16812 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
16813 additions are deleted when the address is passed on to subsequent routers.
16814 For a &%redirect%& router, if a generated address is the same as the incoming
16815 address, this can lead to duplicate addresses with different header
16816 modifications. Exim does not do duplicate deliveries (except, in certain
16817 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
16818 which of the duplicates is discarded, so this ambiguous situation should be
16819 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
16820
16821
16822
16823 .option headers_remove routers list&!! unset
16824 .cindex "header lines" "removing"
16825 .cindex "router" "removing header lines"
16826 This option specifies a list of text headers, colon-separated,
16827 that is associated with any addresses that are accepted by the router.
16828 Each item is separately expanded, at routing time. However, this
16829 option has no effect when an address is just being verified. The way in which
16830 the text is used to remove header lines at transport time is described in
16831 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
16832 the message is in the process of being transported. This means that references
16833 to header lines in string expansions in the transport's configuration still
16834 &"see"& the original header lines.
16835
16836 The &%headers_remove%& option is expanded after &%errors_to%& and
16837 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
16838 the item has no effect. Other expansion failures are treated as configuration
16839 errors.
16840
16841 Unlike most options, &%headers_remove%& can be specified multiple times
16842 for a router; all listed headers are removed.
16843
16844 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
16845 router that has the &%one_time%& option set.
16846
16847 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
16848 removal requests are deleted when the address is passed on to subsequent
16849 routers, and this can lead to problems with duplicates -- see the similar
16850 warning for &%headers_add%& above.
16851
16852
16853 .option ignore_target_hosts routers "host list&!!" unset
16854 .cindex "IP address" "discarding"
16855 .cindex "router" "discarding IP addresses"
16856 Although this option is a host list, it should normally contain IP address
16857 entries rather than names. If any host that is looked up by the router has an
16858 IP address that matches an item in this list, Exim behaves as if that IP
16859 address did not exist. This option allows you to cope with rogue DNS entries
16860 like
16861 .code
16862 remote.domain.example. A 127.0.0.1
16863 .endd
16864 by setting
16865 .code
16866 ignore_target_hosts = 127.0.0.1
16867 .endd
16868 on the relevant router. If all the hosts found by a &(dnslookup)& router are
16869 discarded in this way, the router declines. In a conventional configuration, an
16870 attempt to mail to such a domain would normally provoke the &"unrouteable
16871 domain"& error, and an attempt to verify an address in the domain would fail.
16872 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
16873 router declines if presented with one of the listed addresses.
16874
16875 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
16876 means of the first or the second of the following settings, respectively:
16877 .code
16878 ignore_target_hosts = 0.0.0.0/0
16879 ignore_target_hosts = <; 0::0/0
16880 .endd
16881 The pattern in the first line matches all IPv4 addresses, whereas the pattern
16882 in the second line matches all IPv6 addresses.
16883
16884 This option may also be useful for ignoring link-local and site-local IPv6
16885 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
16886 is expanded before use as a list, it is possible to make it dependent on the
16887 domain that is being routed.
16888
16889 .vindex "&$host_address$&"
16890 During its expansion, &$host_address$& is set to the IP address that is being
16891 checked.
16892
16893 .option initgroups routers boolean false
16894 .cindex "additional groups"
16895 .cindex "groups" "additional"
16896 .cindex "local transports" "uid and gid"
16897 .cindex "transport" "local"
16898 If the router queues an address for a transport, and this option is true, and
16899 the uid supplied by the router is not overridden by the transport, the
16900 &[initgroups()]& function is called when running the transport to ensure that
16901 any additional groups associated with the uid are set up. See also &%group%&
16902 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
16903
16904
16905
16906 .option local_part_prefix routers&!? "string list" unset
16907 .cindex "router" "prefix for local part"
16908 .cindex "prefix" "for local part, used in router"
16909 If this option is set, the router is skipped unless the local part starts with
16910 one of the given strings, or &%local_part_prefix_optional%& is true. See
16911 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
16912 evaluated.
16913
16914 The list is scanned from left to right, and the first prefix that matches is
16915 used. A limited form of wildcard is available; if the prefix begins with an
16916 asterisk, it matches the longest possible sequence of arbitrary characters at
16917 the start of the local part. An asterisk should therefore always be followed by
16918 some character that does not occur in normal local parts.
16919 .cindex "multiple mailboxes"
16920 .cindex "mailbox" "multiple"
16921 Wildcarding can be used to set up multiple user mailboxes, as described in
16922 section &<<SECTmulbox>>&.
16923
16924 .vindex "&$local_part$&"
16925 .vindex "&$local_part_prefix$&"
16926 During the testing of the &%local_parts%& option, and while the router is
16927 running, the prefix is removed from the local part, and is available in the
16928 expansion variable &$local_part_prefix$&. When a message is being delivered, if
16929 the router accepts the address, this remains true during subsequent delivery by
16930 a transport. In particular, the local part that is transmitted in the RCPT
16931 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
16932 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
16933 the relevant transport.
16934
16935 When an address is being verified, &%local_part_prefix%& affects only the
16936 behaviour of the router. If the callout feature of verification is in use, this
16937 means that the full address, including the prefix, will be used during the
16938 callout.
16939
16940 The prefix facility is commonly used to handle local parts of the form
16941 &%owner-something%&. Another common use is to support local parts of the form
16942 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
16943 to tell a user their forwarding is broken &-- by placing a router like this one
16944 immediately before the router that handles &_.forward_& files:
16945 .code
16946 real_localuser:
16947 driver = accept
16948 local_part_prefix = real-
16949 check_local_user
16950 transport = local_delivery
16951 .endd
16952 For security, it would probably be a good idea to restrict the use of this
16953 router to locally-generated messages, using a condition such as this:
16954 .code
16955 condition = ${if match {$sender_host_address}\
16956 {\N^(|127\.0\.0\.1)$\N}}
16957 .endd
16958
16959 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
16960 both conditions must be met if not optional. Care must be taken if wildcards
16961 are used in both a prefix and a suffix on the same router. Different
16962 separator characters must be used to avoid ambiguity.
16963
16964
16965 .option local_part_prefix_optional routers boolean false
16966 See &%local_part_prefix%& above.
16967
16968
16969
16970 .option local_part_suffix routers&!? "string list" unset
16971 .cindex "router" "suffix for local part"
16972 .cindex "suffix for local part" "used in router"
16973 This option operates in the same way as &%local_part_prefix%&, except that the
16974 local part must end (rather than start) with the given string, the
16975 &%local_part_suffix_optional%& option determines whether the suffix is
16976 mandatory, and the wildcard * character, if present, must be the last
16977 character of the suffix. This option facility is commonly used to handle local
16978 parts of the form &%something-request%& and multiple user mailboxes of the form
16979 &%username-foo%&.
16980
16981
16982 .option local_part_suffix_optional routers boolean false
16983 See &%local_part_suffix%& above.
16984
16985
16986
16987 .option local_parts routers&!? "local part list&!!" unset
16988 .cindex "router" "restricting to specific local parts"
16989 .cindex "local part" "checking in router"
16990 The router is run only if the local part of the address matches the list.
16991 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16992 are evaluated, and
16993 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
16994 string is expanded, it is possible to make it depend on the domain, for
16995 example:
16996 .code
16997 local_parts = dbm;/usr/local/specials/$domain
16998 .endd
16999 .vindex "&$local_part_data$&"
17000 If the match is achieved by a lookup, the data that the lookup returned
17001 for the local part is placed in the variable &$local_part_data$& for use in
17002 expansions of the router's private options. You might use this option, for
17003 example, if you have a large number of local virtual domains, and you want to
17004 send all postmaster mail to the same place without having to set up an alias in
17005 each virtual domain:
17006 .code
17007 postmaster:
17008 driver = redirect
17009 local_parts = postmaster
17010 data = postmaster@real.domain.example
17011 .endd
17012
17013
17014 .option log_as_local routers boolean "see below"
17015 .cindex "log" "delivery line"
17016 .cindex "delivery" "log line format"
17017 Exim has two logging styles for delivery, the idea being to make local
17018 deliveries stand out more visibly from remote ones. In the &"local"& style, the
17019 recipient address is given just as the local part, without a domain. The use of
17020 this style is controlled by this option. It defaults to true for the &(accept)&
17021 router, and false for all the others. This option applies only when a
17022 router assigns an address to a transport. It has no effect on routers that
17023 redirect addresses.
17024
17025
17026
17027 .option more routers boolean&!! true
17028 The result of string expansion for this option must be a valid boolean value,
17029 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
17030 result causes an error, and delivery is deferred. If the expansion is forced to
17031 fail, the default value for the option (true) is used. Other failures cause
17032 delivery to be deferred.
17033
17034 If this option is set false, and the router declines to handle the address, no
17035 further routers are tried, routing fails, and the address is bounced.
17036 .oindex "&%self%&"
17037 However, if the router explicitly passes an address to the following router by
17038 means of the setting
17039 .code
17040 self = pass
17041 .endd
17042 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
17043 does not affect the behaviour if one of the precondition tests fails. In that
17044 case, the address is always passed to the next router.
17045
17046 Note that &%address_data%& is not considered to be a precondition. If its
17047 expansion is forced to fail, the router declines, and the value of &%more%&
17048 controls what happens next.
17049
17050
17051 .option pass_on_timeout routers boolean false
17052 .cindex "timeout" "of router"
17053 .cindex "router" "timeout"
17054 If a router times out during a host lookup, it normally causes deferral of the
17055 address. If &%pass_on_timeout%& is set, the address is passed on to the next
17056 router, overriding &%no_more%&. This may be helpful for systems that are
17057 intermittently connected to the Internet, or those that want to pass to a smart
17058 host any messages that cannot immediately be delivered.
17059
17060 There are occasional other temporary errors that can occur while doing DNS
17061 lookups. They are treated in the same way as a timeout, and this option
17062 applies to all of them.
17063
17064
17065
17066 .option pass_router routers string unset
17067 .cindex "router" "go to after &""pass""&"
17068 Routers that recognize the generic &%self%& option (&(dnslookup)&,
17069 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
17070 routing to continue, and overriding a false setting of &%more%&. When one of
17071 these routers returns &"pass"&, the address is normally handed on to the next
17072 router in sequence. This can be changed by setting &%pass_router%& to the name
17073 of another router. However (unlike &%redirect_router%&) the named router must
17074 be below the current router, to avoid loops. Note that this option applies only
17075 to the special case of &"pass"&. It does not apply when a router returns
17076 &"decline"& because it cannot handle an address.
17077
17078
17079
17080 .option redirect_router routers string unset
17081 .cindex "router" "start at after redirection"
17082 Sometimes an administrator knows that it is pointless to reprocess addresses
17083 generated from alias or forward files with the same router again. For
17084 example, if an alias file translates real names into login ids there is no
17085 point searching the alias file a second time, especially if it is a large file.
17086
17087 The &%redirect_router%& option can be set to the name of any router instance.
17088 It causes the routing of any generated addresses to start at the named router
17089 instead of at the first router. This option has no effect if the router in
17090 which it is set does not generate new addresses.
17091
17092
17093
17094 .option require_files routers&!? "string list&!!" unset
17095 .cindex "file" "requiring for router"
17096 .cindex "router" "requiring file existence"
17097 This option provides a general mechanism for predicating the running of a
17098 router on the existence or non-existence of certain files or directories.
17099 Before running a router, as one of its precondition tests, Exim works its way
17100 through the &%require_files%& list, expanding each item separately.
17101
17102 Because the list is split before expansion, any colons in expansion items must
17103 be doubled, or the facility for using a different list separator must be used.
17104 If any expansion is forced to fail, the item is ignored. Other expansion
17105 failures cause routing of the address to be deferred.
17106
17107 If any expanded string is empty, it is ignored. Otherwise, except as described
17108 below, each string must be a fully qualified file path, optionally preceded by
17109 &"!"&. The paths are passed to the &[stat()]& function to test for the
17110 existence of the files or directories. The router is skipped if any paths not
17111 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
17112
17113 .cindex "NFS"
17114 If &[stat()]& cannot determine whether a file exists or not, delivery of
17115 the message is deferred. This can happen when NFS-mounted filesystems are
17116 unavailable.
17117
17118 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
17119 options, so you cannot use it to check for the existence of a file in which to
17120 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
17121 full list of the order in which preconditions are evaluated.) However, as
17122 these options are all expanded, you can use the &%exists%& expansion condition
17123 to make such tests. The &%require_files%& option is intended for checking files
17124 that the router may be going to use internally, or which are needed by a
17125 transport (for example &_.procmailrc_&).
17126
17127 During delivery, the &[stat()]& function is run as root, but there is a
17128 facility for some checking of the accessibility of a file by another user.
17129 This is not a proper permissions check, but just a &"rough"& check that
17130 operates as follows:
17131
17132 If an item in a &%require_files%& list does not contain any forward slash
17133 characters, it is taken to be the user (and optional group, separated by a
17134 comma) to be checked for subsequent files in the list. If no group is specified
17135 but the user is specified symbolically, the gid associated with the uid is
17136 used. For example:
17137 .code
17138 require_files = mail:/some/file
17139 require_files = $local_part:$home/.procmailrc
17140 .endd
17141 If a user or group name in a &%require_files%& list does not exist, the
17142 &%require_files%& condition fails.
17143
17144 Exim performs the check by scanning along the components of the file path, and
17145 checking the access for the given uid and gid. It checks for &"x"& access on
17146 directories, and &"r"& access on the final file. Note that this means that file
17147 access control lists, if the operating system has them, are ignored.
17148
17149 &*Warning 1*&: When the router is being run to verify addresses for an
17150 incoming SMTP message, Exim is not running as root, but under its own uid. This
17151 may affect the result of a &%require_files%& check. In particular, &[stat()]&
17152 may yield the error EACCES (&"Permission denied"&). This means that the Exim
17153 user is not permitted to read one of the directories on the file's path.
17154
17155 &*Warning 2*&: Even when Exim is running as root while delivering a message,
17156 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
17157 without root access. In this case, if a check for access by a particular user
17158 is requested, Exim creates a subprocess that runs as that user, and tries the
17159 check again in that process.
17160
17161 The default action for handling an unresolved EACCES is to consider it to
17162 be caused by a configuration error, and routing is deferred because the
17163 existence or non-existence of the file cannot be determined. However, in some
17164 circumstances it may be desirable to treat this condition as if the file did
17165 not exist. If the file name (or the exclamation mark that precedes the file
17166 name for non-existence) is preceded by a plus sign, the EACCES error is treated
17167 as if the file did not exist. For example:
17168 .code
17169 require_files = +/some/file
17170 .endd
17171 If the router is not an essential part of verification (for example, it
17172 handles users' &_.forward_& files), another solution is to set the &%verify%&
17173 option false so that the router is skipped when verifying.
17174
17175
17176
17177 .option retry_use_local_part routers boolean "see below"
17178 .cindex "hints database" "retry keys"
17179 .cindex "local part" "in retry keys"
17180 When a delivery suffers a temporary routing failure, a retry record is created
17181 in Exim's hints database. For addresses whose routing depends only on the
17182 domain, the key for the retry record should not involve the local part, but for
17183 other addresses, both the domain and the local part should be included.
17184 Usually, remote routing is of the former kind, and local routing is of the
17185 latter kind.
17186
17187 This option controls whether the local part is used to form the key for retry
17188 hints for addresses that suffer temporary errors while being handled by this
17189 router. The default value is true for any router that has &%check_local_user%&
17190 set, and false otherwise. Note that this option does not apply to hints keys
17191 for transport delays; they are controlled by a generic transport option of the
17192 same name.
17193
17194 The setting of &%retry_use_local_part%& applies only to the router on which it
17195 appears. If the router generates child addresses, they are routed
17196 independently; this setting does not become attached to them.
17197
17198
17199
17200 .option router_home_directory routers string&!! unset
17201 .cindex "router" "home directory for"
17202 .cindex "home directory" "for router"
17203 .vindex "&$home$&"
17204 This option sets a home directory for use while the router is running. (Compare
17205 &%transport_home_directory%&, which sets a home directory for later
17206 transporting.) In particular, if used on a &(redirect)& router, this option
17207 sets a value for &$home$& while a filter is running. The value is expanded;
17208 forced expansion failure causes the option to be ignored &-- other failures
17209 cause the router to defer.
17210
17211 Expansion of &%router_home_directory%& happens immediately after the
17212 &%check_local_user%& test (if configured), before any further expansions take
17213 place.
17214 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17215 are evaluated.)
17216 While the router is running, &%router_home_directory%& overrides the value of
17217 &$home$& that came from &%check_local_user%&.
17218
17219 When a router accepts an address and assigns it to a local transport (including
17220 the cases when a &(redirect)& router generates a pipe, file, or autoreply
17221 delivery), the home directory setting for the transport is taken from the first
17222 of these values that is set:
17223
17224 .ilist
17225 The &%home_directory%& option on the transport;
17226 .next
17227 The &%transport_home_directory%& option on the router;
17228 .next
17229 The password data if &%check_local_user%& is set on the router;
17230 .next
17231 The &%router_home_directory%& option on the router.
17232 .endlist
17233
17234 In other words, &%router_home_directory%& overrides the password data for the
17235 router, but not for the transport.
17236
17237
17238
17239 .option self routers string freeze
17240 .cindex "MX record" "pointing to local host"
17241 .cindex "local host" "MX pointing to"
17242 This option applies to those routers that use a recipient address to find a
17243 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
17244 and &(manualroute)& routers.
17245 Certain configurations of the &(queryprogram)& router can also specify a list
17246 of remote hosts.
17247 Usually such routers are configured to send the message to a remote host via an
17248 &(smtp)& transport. The &%self%& option specifies what happens when the first
17249 host on the list turns out to be the local host.
17250 The way in which Exim checks for the local host is described in section
17251 &<<SECTreclocipadd>>&.
17252
17253 Normally this situation indicates either an error in Exim's configuration (for
17254 example, the router should be configured not to process this domain), or an
17255 error in the DNS (for example, the MX should not point to this host). For this
17256 reason, the default action is to log the incident, defer the address, and
17257 freeze the message. The following alternatives are provided for use in special
17258 cases:
17259
17260 .vlist
17261 .vitem &%defer%&
17262 Delivery of the message is tried again later, but the message is not frozen.
17263
17264 .vitem "&%reroute%&: <&'domain'&>"
17265 The domain is changed to the given domain, and the address is passed back to
17266 be reprocessed by the routers. No rewriting of headers takes place. This
17267 behaviour is essentially a redirection.
17268
17269 .vitem "&%reroute: rewrite:%& <&'domain'&>"
17270 The domain is changed to the given domain, and the address is passed back to be
17271 reprocessed by the routers. Any headers that contain the original domain are
17272 rewritten.
17273
17274 .vitem &%pass%&
17275 .oindex "&%more%&"
17276 .vindex "&$self_hostname$&"
17277 The router passes the address to the next router, or to the router named in the
17278 &%pass_router%& option if it is set. This overrides &%no_more%&. During
17279 subsequent routing and delivery, the variable &$self_hostname$& contains the
17280 name of the local host that the router encountered. This can be used to
17281 distinguish between different cases for hosts with multiple names. The
17282 combination
17283 .code
17284 self = pass
17285 no_more
17286 .endd
17287 ensures that only those addresses that routed to the local host are passed on.
17288 Without &%no_more%&, addresses that were declined for other reasons would also
17289 be passed to the next router.
17290
17291 .vitem &%fail%&
17292 Delivery fails and an error report is generated.
17293
17294 .vitem &%send%&
17295 .cindex "local host" "sending to"
17296 The anomaly is ignored and the address is queued for the transport. This
17297 setting should be used with extreme caution. For an &(smtp)& transport, it
17298 makes sense only in cases where the program that is listening on the SMTP port
17299 is not this version of Exim. That is, it must be some other MTA, or Exim with a
17300 different configuration file that handles the domain in another way.
17301 .endlist
17302
17303
17304
17305 .option senders routers&!? "address list&!!" unset
17306 .cindex "router" "checking senders"
17307 If this option is set, the router is skipped unless the message's sender
17308 address matches something on the list.
17309 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17310 are evaluated.
17311
17312 There are issues concerning verification when the running of routers is
17313 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
17314 setting, it sets the sender to the null string. When using the &%-bt%& option
17315 to check a configuration file, it is necessary also to use the &%-f%& option to
17316 set an appropriate sender. For incoming mail, the sender is unset when
17317 verifying the sender, but is available when verifying any recipients. If the
17318 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
17319 matters.
17320
17321
17322 .option translate_ip_address routers string&!! unset
17323 .cindex "IP address" "translating"
17324 .cindex "packet radio"
17325 .cindex "router" "IP address translation"
17326 There exist some rare networking situations (for example, packet radio) where
17327 it is helpful to be able to translate IP addresses generated by normal routing
17328 mechanisms into other IP addresses, thus performing a kind of manual IP
17329 routing. This should be done only if the normal IP routing of the TCP/IP stack
17330 is inadequate or broken. Because this is an extremely uncommon requirement, the
17331 code to support this option is not included in the Exim binary unless
17332 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
17333
17334 .vindex "&$host_address$&"
17335 The &%translate_ip_address%& string is expanded for every IP address generated
17336 by the router, with the generated address set in &$host_address$&. If the
17337 expansion is forced to fail, no action is taken.
17338 For any other expansion error, delivery of the message is deferred.
17339 If the result of the expansion is an IP address, that replaces the original
17340 address; otherwise the result is assumed to be a host name &-- this is looked
17341 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
17342 produce one or more replacement IP addresses. For example, to subvert all IP
17343 addresses in some specific networks, this could be added to a router:
17344 .code
17345 translate_ip_address = \
17346 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
17347 {$value}fail}}
17348 .endd
17349 The file would contain lines like
17350 .code
17351 10.2.3.128/26 some.host
17352 10.8.4.34/26 10.44.8.15
17353 .endd
17354 You should not make use of this facility unless you really understand what you
17355 are doing.
17356
17357
17358
17359 .option transport routers string&!! unset
17360 This option specifies the transport to be used when a router accepts an address
17361 and sets it up for delivery. A transport is never needed if a router is used
17362 only for verification. The value of the option is expanded at routing time,
17363 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
17364 and result must be the name of one of the configured transports. If it is not,
17365 delivery is deferred.
17366
17367 The &%transport%& option is not used by the &(redirect)& router, but it does
17368 have some private options that set up transports for pipe and file deliveries
17369 (see chapter &<<CHAPredirect>>&).
17370
17371
17372
17373 .option transport_current_directory routers string&!! unset
17374 .cindex "current directory for local transport"
17375 This option associates a current directory with any address that is routed
17376 to a local transport. This can happen either because a transport is
17377 explicitly configured for the router, or because it generates a delivery to a
17378 file or a pipe. During the delivery process (that is, at transport time), this
17379 option string is expanded and is set as the current directory, unless
17380 overridden by a setting on the transport.
17381 If the expansion fails for any reason, including forced failure, an error is
17382 logged, and delivery is deferred.
17383 See chapter &<<CHAPenvironment>>& for details of the local delivery
17384 environment.
17385
17386
17387
17388
17389 .option transport_home_directory routers string&!! "see below"
17390 .cindex "home directory" "for local transport"
17391 This option associates a home directory with any address that is routed to a
17392 local transport. This can happen either because a transport is explicitly
17393 configured for the router, or because it generates a delivery to a file or a
17394 pipe. During the delivery process (that is, at transport time), the option
17395 string is expanded and is set as the home directory, unless overridden by a
17396 setting of &%home_directory%& on the transport.
17397 If the expansion fails for any reason, including forced failure, an error is
17398 logged, and delivery is deferred.
17399
17400 If the transport does not specify a home directory, and
17401 &%transport_home_directory%& is not set for the router, the home directory for
17402 the transport is taken from the password data if &%check_local_user%& is set for
17403 the router. Otherwise it is taken from &%router_home_directory%& if that option
17404 is set; if not, no home directory is set for the transport.
17405
17406 See chapter &<<CHAPenvironment>>& for further details of the local delivery
17407 environment.
17408
17409
17410
17411
17412 .option unseen routers boolean&!! false
17413 .cindex "router" "carrying on after success"
17414 The result of string expansion for this option must be a valid boolean value,
17415 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
17416 result causes an error, and delivery is deferred. If the expansion is forced to
17417 fail, the default value for the option (false) is used. Other failures cause
17418 delivery to be deferred.
17419
17420 When this option is set true, routing does not cease if the router accepts the
17421 address. Instead, a copy of the incoming address is passed to the next router,
17422 overriding a false setting of &%more%&. There is little point in setting
17423 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
17424 the value of &%unseen%& contains expansion items (and therefore, presumably, is
17425 sometimes true and sometimes false).
17426
17427 .cindex "copy of message (&%unseen%& option)"
17428 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
17429 qualifier in filter files. It can be used to cause copies of messages to be
17430 delivered to some other destination, while also carrying out a normal delivery.
17431 In effect, the current address is made into a &"parent"& that has two children
17432 &-- one that is delivered as specified by this router, and a clone that goes on
17433 to be routed further. For this reason, &%unseen%& may not be combined with the
17434 &%one_time%& option in a &(redirect)& router.
17435
17436 &*Warning*&: Header lines added to the address (or specified for removal) by
17437 this router or by previous routers affect the &"unseen"& copy of the message
17438 only. The clone that continues to be processed by further routers starts with
17439 no added headers and none specified for removal. For a &%redirect%& router, if
17440 a generated address is the same as the incoming address, this can lead to
17441 duplicate addresses with different header modifications. Exim does not do
17442 duplicate deliveries (except, in certain circumstances, to pipes -- see section
17443 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
17444 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
17445 &%redirect%& router may be of help.
17446
17447 Unlike the handling of header modifications, any data that was set by the
17448 &%address_data%& option in the current or previous routers &'is'& passed on to
17449 subsequent routers.
17450
17451
17452 .option user routers string&!! "see below"
17453 .cindex "uid (user id)" "local delivery"
17454 .cindex "local transports" "uid and gid"
17455 .cindex "transport" "local"
17456 .cindex "router" "user for filter processing"
17457 .cindex "filter" "user for processing"
17458 When a router queues an address for a transport, and the transport does not
17459 specify a user, the user given here is used when running the delivery process.
17460 The user may be specified numerically or by name. If expansion fails, the
17461 error is logged and delivery is deferred.
17462 This user is also used by the &(redirect)& router when running a filter file.
17463 The default is unset, except when &%check_local_user%& is set. In this case,
17464 the default is taken from the password information. If the user is specified as
17465 a name, and &%group%& is not set, the group associated with the user is used.
17466 See also &%initgroups%& and &%group%& and the discussion in chapter
17467 &<<CHAPenvironment>>&.
17468
17469
17470
17471 .option verify routers&!? boolean true
17472 Setting this option has the effect of setting &%verify_sender%& and
17473 &%verify_recipient%& to the same value.
17474
17475
17476 .option verify_only routers&!? boolean false
17477 .cindex "EXPN" "with &%verify_only%&"
17478 .oindex "&%-bv%&"
17479 .cindex "router" "used only when verifying"
17480 If this option is set, the router is used only when verifying an address,
17481 delivering in cutthrough mode or
17482 testing with the &%-bv%& option, not when actually doing a delivery, testing
17483 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
17484 restricted to verifying only senders or recipients by means of
17485 &%verify_sender%& and &%verify_recipient%&.
17486
17487 &*Warning*&: When the router is being run to verify addresses for an incoming
17488 SMTP message, Exim is not running as root, but under its own uid. If the router
17489 accesses any files, you need to make sure that they are accessible to the Exim
17490 user or group.
17491
17492
17493 .option verify_recipient routers&!? boolean true
17494 If this option is false, the router is skipped when verifying recipient
17495 addresses,
17496 delivering in cutthrough mode
17497 or testing recipient verification using &%-bv%&.
17498 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17499 are evaluated.
17500
17501
17502 .option verify_sender routers&!? boolean true
17503 If this option is false, the router is skipped when verifying sender addresses
17504 or testing sender verification using &%-bvs%&.
17505 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17506 are evaluated.
17507 .ecindex IIDgenoprou1
17508 .ecindex IIDgenoprou2
17509
17510
17511
17512
17513
17514
17515 . ////////////////////////////////////////////////////////////////////////////
17516 . ////////////////////////////////////////////////////////////////////////////
17517
17518 .chapter "The accept router" "CHID4"
17519 .cindex "&(accept)& router"
17520 .cindex "routers" "&(accept)&"
17521 The &(accept)& router has no private options of its own. Unless it is being
17522 used purely for verification (see &%verify_only%&) a transport is required to
17523 be defined by the generic &%transport%& option. If the preconditions that are
17524 specified by generic options are met, the router accepts the address and queues
17525 it for the given transport. The most common use of this router is for setting
17526 up deliveries to local mailboxes. For example:
17527 .code
17528 localusers:
17529 driver = accept
17530 domains = mydomain.example
17531 check_local_user
17532 transport = local_delivery
17533 .endd
17534 The &%domains%& condition in this example checks the domain of the address, and
17535 &%check_local_user%& checks that the local part is the login of a local user.
17536 When both preconditions are met, the &(accept)& router runs, and queues the
17537 address for the &(local_delivery)& transport.
17538
17539
17540
17541
17542
17543
17544 . ////////////////////////////////////////////////////////////////////////////
17545 . ////////////////////////////////////////////////////////////////////////////
17546
17547 .chapter "The dnslookup router" "CHAPdnslookup"
17548 .scindex IIDdnsrou1 "&(dnslookup)& router"
17549 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
17550 The &(dnslookup)& router looks up the hosts that handle mail for the
17551 recipient's domain in the DNS. A transport must always be set for this router,
17552 unless &%verify_only%& is set.
17553
17554 If SRV support is configured (see &%check_srv%& below), Exim first searches for
17555 SRV records. If none are found, or if SRV support is not configured,
17556 MX records are looked up. If no MX records exist, address records are sought.
17557 However, &%mx_domains%& can be set to disable the direct use of address
17558 records.
17559
17560 MX records of equal priority are sorted by Exim into a random order. Exim then
17561 looks for address records for the host names obtained from MX or SRV records.
17562 When a host has more than one IP address, they are sorted into a random order,
17563 except that IPv6 addresses are always sorted before IPv4 addresses. If all the
17564 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
17565 generic option, the router declines.
17566
17567 Unless they have the highest priority (lowest MX value), MX records that point
17568 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
17569 are discarded, together with any other MX records of equal or lower priority.
17570
17571 .cindex "MX record" "pointing to local host"
17572 .cindex "local host" "MX pointing to"
17573 .oindex "&%self%&" "in &(dnslookup)& router"
17574 If the host pointed to by the highest priority MX record, or looked up as an
17575 address record, is the local host, or matches &%hosts_treat_as_local%&, what
17576 happens is controlled by the generic &%self%& option.
17577
17578
17579 .section "Problems with DNS lookups" "SECTprowitdnsloo"
17580 There have been problems with DNS servers when SRV records are looked up.
17581 Some mis-behaving servers return a DNS error or timeout when a non-existent
17582 SRV record is sought. Similar problems have in the past been reported for
17583 MX records. The global &%dns_again_means_nonexist%& option can help with this
17584 problem, but it is heavy-handed because it is a global option.
17585
17586 For this reason, there are two options, &%srv_fail_domains%& and
17587 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
17588 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
17589 an attempt to look up an SRV or MX record causes one of these results, and the
17590 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
17591 such record"&. In the case of an SRV lookup, this means that the router
17592 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
17593 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
17594 case routing fails.
17595
17596
17597 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
17598 .cindex "&(dnslookup)& router" "declines"
17599 There are a few cases where a &(dnslookup)& router will decline to accept
17600 an address; if such a router is expected to handle "all remaining non-local
17601 domains", then it is important to set &%no_more%&.
17602
17603 Reasons for a &(dnslookup)& router to decline currently include:
17604 .ilist
17605 The domain does not exist in DNS
17606 .next
17607 The domain exists but the MX record's host part is just "."; this is a common
17608 convention (borrowed from SRV) used to indicate that there is no such service
17609 for this domain and to not fall back to trying A/AAAA records.
17610 .next
17611 Ditto, but for SRV records, when &%check_srv%& is set on this router.
17612 .next
17613 MX record points to a non-existent host.
17614 .next
17615 MX record points to an IP address and the main section option
17616 &%allow_mx_to_ip%& is not set.
17617 .next
17618 MX records exist and point to valid hosts, but all hosts resolve only to
17619 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
17620 .next
17621 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
17622 &%dns_check_names_pattern%& for handling one variant of this)
17623 .next
17624 &%check_secondary_mx%& is set on this router but the local host can
17625 not be found in the MX records (see below)
17626 .endlist
17627
17628
17629
17630
17631 .section "Private options for dnslookup" "SECID118"
17632 .cindex "options" "&(dnslookup)& router"
17633 The private options for the &(dnslookup)& router are as follows:
17634
17635 .option check_secondary_mx dnslookup boolean false
17636 .cindex "MX record" "checking for secondary"
17637 If this option is set, the router declines unless the local host is found in
17638 (and removed from) the list of hosts obtained by MX lookup. This can be used to
17639 process domains for which the local host is a secondary mail exchanger
17640 differently to other domains. The way in which Exim decides whether a host is
17641 the local host is described in section &<<SECTreclocipadd>>&.
17642
17643
17644 .option check_srv dnslookup string&!! unset
17645 .cindex "SRV record" "enabling use of"
17646 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
17647 addition to MX and address records. The support is disabled by default. To
17648 enable SRV support, set the &%check_srv%& option to the name of the service
17649 required. For example,
17650 .code
17651 check_srv = smtp
17652 .endd
17653 looks for SRV records that refer to the normal smtp service. The option is
17654 expanded, so the service name can vary from message to message or address
17655 to address. This might be helpful if SRV records are being used for a
17656 submission service. If the expansion is forced to fail, the &%check_srv%&
17657 option is ignored, and the router proceeds to look for MX records in the
17658 normal way.
17659
17660 When the expansion succeeds, the router searches first for SRV records for
17661 the given service (it assumes TCP protocol). A single SRV record with a
17662 host name that consists of just a single dot indicates &"no such service for
17663 this domain"&; if this is encountered, the router declines. If other kinds of
17664 SRV record are found, they are used to construct a host list for delivery
17665 according to the rules of RFC 2782. MX records are not sought in this case.
17666
17667 When no SRV records are found, MX records (and address records) are sought in
17668 the traditional way. In other words, SRV records take precedence over MX
17669 records, just as MX records take precedence over address records. Note that
17670 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
17671 defined it. It is apparently believed that MX records are sufficient for email
17672 and that SRV records should not be used for this purpose. However, SRV records
17673 have an additional &"weight"& feature which some people might find useful when
17674 trying to split an SMTP load between hosts of different power.
17675
17676 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
17677 when there is a DNS lookup error.
17678
17679
17680
17681 .new
17682 .option dnssec_request_domains dnslookup "domain list&!!" unset
17683 .cindex "MX record" "security"
17684 .cindex "DNSSEC" "MX lookup"
17685 .cindex "security" "MX lookup"
17686 .cindex "DNS" "DNSSEC"
17687 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
17688 the dnssec request bit set.
17689 This applies to all of the SRV, MX A6, AAAA, A lookup sequence.
17690
17691 See also the &$lookup_dnssec_authenticated$& variable.
17692 .wen
17693
17694
17695
17696 .new
17697 .option dnssec_require_domains dnslookup "domain list&!!" unset
17698 .cindex "MX record" "security"
17699 .cindex "DNSSEC" "MX lookup"
17700 .cindex "security" "MX lookup"
17701 .cindex "DNS" "DNSSEC"
17702 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
17703 the dnssec request bit set. Any returns not having the Authenticated Data bit
17704 (AD bit) set wil be ignored and logged as a host-lookup failure.
17705 This applies to all of the SRV, MX A6, AAAA, A lookup sequence.
17706 .wen
17707
17708
17709
17710 .option mx_domains dnslookup "domain list&!!" unset
17711 .cindex "MX record" "required to exist"
17712 .cindex "SRV record" "required to exist"
17713 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
17714 record in order to be recognized. (The name of this option could be improved.)
17715 For example, if all the mail hosts in &'fict.example'& are known to have MX
17716 records, except for those in &'discworld.fict.example'&, you could use this
17717 setting:
17718 .code
17719 mx_domains = ! *.discworld.fict.example : *.fict.example
17720 .endd
17721 This specifies that messages addressed to a domain that matches the list but
17722 has no MX record should be bounced immediately instead of being routed using
17723 the address record.
17724
17725
17726 .option mx_fail_domains dnslookup "domain list&!!" unset
17727 If the DNS lookup for MX records for one of the domains in this list causes a
17728 DNS lookup error, Exim behaves as if no MX records were found. See section
17729 &<<SECTprowitdnsloo>>& for more discussion.
17730
17731
17732
17733
17734 .option qualify_single dnslookup boolean true
17735 .cindex "DNS" "resolver options"
17736 .cindex "DNS" "qualifying single-component names"
17737 When this option is true, the resolver option RES_DEFNAMES is set for DNS
17738 lookups. Typically, but not standardly, this causes the resolver to qualify
17739 single-component names with the default domain. For example, on a machine
17740 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
17741 &'thesaurus.ref.example'& inside the resolver. For details of what your
17742 resolver actually does, consult your man pages for &'resolver'& and
17743 &'resolv.conf'&.
17744
17745
17746
17747 .option rewrite_headers dnslookup boolean true
17748 .cindex "rewriting" "header lines"
17749 .cindex "header lines" "rewriting"
17750 If the domain name in the address that is being processed is not fully
17751 qualified, it may be expanded to its full form by a DNS lookup. For example, if
17752 an address is specified as &'dormouse@teaparty'&, the domain might be
17753 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
17754 occur as a result of setting the &%widen_domains%& option. If
17755 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
17756 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
17757 header lines of the message are rewritten with the full domain name.
17758
17759 This option should be turned off only when it is known that no message is
17760 ever going to be sent outside an environment where the abbreviation makes
17761 sense.
17762
17763 When an MX record is looked up in the DNS and matches a wildcard record, name
17764 servers normally return a record containing the name that has been looked up,
17765 making it impossible to detect whether a wildcard was present or not. However,
17766 some name servers have recently been seen to return the wildcard entry. If the
17767 name returned by a DNS lookup begins with an asterisk, it is not used for
17768 header rewriting.
17769
17770
17771 .option same_domain_copy_routing dnslookup boolean false
17772 .cindex "address" "copying routing"
17773 Addresses with the same domain are normally routed by the &(dnslookup)& router
17774 to the same list of hosts. However, this cannot be presumed, because the router
17775 options and preconditions may refer to the local part of the address. By
17776 default, therefore, Exim routes each address in a message independently. DNS
17777 servers run caches, so repeated DNS lookups are not normally expensive, and in
17778 any case, personal messages rarely have more than a few recipients.
17779
17780 If you are running mailing lists with large numbers of subscribers at the same
17781 domain, and you are using a &(dnslookup)& router which is independent of the
17782 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
17783 lookups for identical domains in one message. In this case, when &(dnslookup)&
17784 routes an address to a remote transport, any other unrouted addresses in the
17785 message that have the same domain are automatically given the same routing
17786 without processing them independently,
17787 provided the following conditions are met:
17788
17789 .ilist
17790 No router that processed the address specified &%headers_add%& or
17791 &%headers_remove%&.
17792 .next
17793 The router did not change the address in any way, for example, by &"widening"&
17794 the domain.
17795 .endlist
17796
17797
17798
17799
17800 .option search_parents dnslookup boolean false
17801 .cindex "DNS" "resolver options"
17802 When this option is true, the resolver option RES_DNSRCH is set for DNS
17803 lookups. This is different from the &%qualify_single%& option in that it
17804 applies to domains containing dots. Typically, but not standardly, it causes
17805 the resolver to search for the name in the current domain and in parent
17806 domains. For example, on a machine in the &'fict.example'& domain, if looking
17807 up &'teaparty.wonderland'& failed, the resolver would try
17808 &'teaparty.wonderland.fict.example'&. For details of what your resolver
17809 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
17810
17811 Setting this option true can cause problems in domains that have a wildcard MX
17812 record, because any domain that does not have its own MX record matches the
17813 local wildcard.
17814
17815
17816
17817 .option srv_fail_domains dnslookup "domain list&!!" unset
17818 If the DNS lookup for SRV records for one of the domains in this list causes a
17819 DNS lookup error, Exim behaves as if no SRV records were found. See section
17820 &<<SECTprowitdnsloo>>& for more discussion.
17821
17822
17823
17824
17825 .option widen_domains dnslookup "string list" unset
17826 .cindex "domain" "partial; widening"
17827 If a DNS lookup fails and this option is set, each of its strings in turn is
17828 added onto the end of the domain, and the lookup is tried again. For example,
17829 if
17830 .code
17831 widen_domains = fict.example:ref.example
17832 .endd
17833 is set and a lookup of &'klingon.dictionary'& fails,
17834 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
17835 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
17836 and &%search_parents%& options can cause some widening to be undertaken inside
17837 the DNS resolver. &%widen_domains%& is not applied to sender addresses
17838 when verifying, unless &%rewrite_headers%& is false (not the default).
17839
17840
17841 .section "Effect of qualify_single and search_parents" "SECID119"
17842 When a domain from an envelope recipient is changed by the resolver as a result
17843 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
17844 corresponding address in the message's header lines unless &%rewrite_headers%&
17845 is set false. Exim then re-routes the address, using the full domain.
17846
17847 These two options affect only the DNS lookup that takes place inside the router
17848 for the domain of the address that is being routed. They do not affect lookups
17849 such as that implied by
17850 .code
17851 domains = @mx_any
17852 .endd
17853 that may happen while processing a router precondition before the router is
17854 entered. No widening ever takes place for these lookups.
17855 .ecindex IIDdnsrou1
17856 .ecindex IIDdnsrou2
17857
17858
17859
17860
17861
17862
17863
17864
17865
17866 . ////////////////////////////////////////////////////////////////////////////
17867 . ////////////////////////////////////////////////////////////////////////////
17868
17869 .chapter "The ipliteral router" "CHID5"
17870 .cindex "&(ipliteral)& router"
17871 .cindex "domain literal" "routing"
17872 .cindex "routers" "&(ipliteral)&"
17873 This router has no private options. Unless it is being used purely for
17874 verification (see &%verify_only%&) a transport is required to be defined by the
17875 generic &%transport%& option. The router accepts the address if its domain part
17876 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
17877 router handles the address
17878 .code
17879 root@[192.168.1.1]
17880 .endd
17881 by setting up delivery to the host with that IP address. IPv4 domain literals
17882 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
17883 are similar, but the address is preceded by &`ipv6:`&. For example:
17884 .code
17885 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
17886 .endd
17887 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
17888 grounds that sooner or later somebody will try it.
17889
17890 .oindex "&%self%&" "in &(ipliteral)& router"
17891 If the IP address matches something in &%ignore_target_hosts%&, the router
17892 declines. If an IP literal turns out to refer to the local host, the generic
17893 &%self%& option determines what happens.
17894
17895 The RFCs require support for domain literals; however, their use is
17896 controversial in today's Internet. If you want to use this router, you must
17897 also set the main configuration option &%allow_domain_literals%&. Otherwise,
17898 Exim will not recognize the domain literal syntax in addresses.
17899
17900
17901
17902 . ////////////////////////////////////////////////////////////////////////////
17903 . ////////////////////////////////////////////////////////////////////////////
17904
17905 .chapter "The iplookup router" "CHID6"
17906 .cindex "&(iplookup)& router"
17907 .cindex "routers" "&(iplookup)&"
17908 The &(iplookup)& router was written to fulfil a specific requirement in
17909 Cambridge University (which in fact no longer exists). For this reason, it is
17910 not included in the binary of Exim by default. If you want to include it, you
17911 must set
17912 .code
17913 ROUTER_IPLOOKUP=yes
17914 .endd
17915 in your &_Local/Makefile_& configuration file.
17916
17917 The &(iplookup)& router routes an address by sending it over a TCP or UDP
17918 connection to one or more specific hosts. The host can then return the same or
17919 a different address &-- in effect rewriting the recipient address in the
17920 message's envelope. The new address is then passed on to subsequent routers. If
17921 this process fails, the address can be passed on to other routers, or delivery
17922 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
17923 must not be specified for it.
17924
17925 .cindex "options" "&(iplookup)& router"
17926 .option hosts iplookup string unset
17927 This option must be supplied. Its value is a colon-separated list of host
17928 names. The hosts are looked up using &[gethostbyname()]&
17929 (or &[getipnodebyname()]& when available)
17930 and are tried in order until one responds to the query. If none respond, what
17931 happens is controlled by &%optional%&.
17932
17933
17934 .option optional iplookup boolean false
17935 If &%optional%& is true, if no response is obtained from any host, the address
17936 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
17937 delivery to the address is deferred.
17938
17939
17940 .option port iplookup integer 0
17941 .cindex "port" "&(iplookup)& router"
17942 This option must be supplied. It specifies the port number for the TCP or UDP
17943 call.
17944
17945
17946 .option protocol iplookup string udp
17947 This option can be set to &"udp"& or &"tcp"& to specify which of the two
17948 protocols is to be used.
17949
17950
17951 .option query iplookup string&!! "see below"
17952 This defines the content of the query that is sent to the remote hosts. The
17953 default value is:
17954 .code
17955 $local_part@$domain $local_part@$domain
17956 .endd
17957 The repetition serves as a way of checking that a response is to the correct
17958 query in the default case (see &%response_pattern%& below).
17959
17960
17961 .option reroute iplookup string&!! unset
17962 If this option is not set, the rerouted address is precisely the byte string
17963 returned by the remote host, up to the first white space, if any. If set, the
17964 string is expanded to form the rerouted address. It can include parts matched
17965 in the response by &%response_pattern%& by means of numeric variables such as
17966 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
17967 whether or not a pattern is in use. In all cases, the rerouted address must end
17968 up in the form &'local_part@domain'&.
17969
17970
17971 .option response_pattern iplookup string unset
17972 This option can be set to a regular expression that is applied to the string
17973 returned from the remote host. If the pattern does not match the response, the
17974 router declines. If &%response_pattern%& is not set, no checking of the
17975 response is done, unless the query was defaulted, in which case there is a
17976 check that the text returned after the first white space is the original
17977 address. This checks that the answer that has been received is in response to
17978 the correct question. For example, if the response is just a new domain, the
17979 following could be used:
17980 .code
17981 response_pattern = ^([^@]+)$
17982 reroute = $local_part@$1
17983 .endd
17984
17985 .option timeout iplookup time 5s
17986 This specifies the amount of time to wait for a response from the remote
17987 machine. The same timeout is used for the &[connect()]& function for a TCP
17988 call. It does not apply to UDP.
17989
17990
17991
17992
17993 . ////////////////////////////////////////////////////////////////////////////
17994 . ////////////////////////////////////////////////////////////////////////////
17995
17996 .chapter "The manualroute router" "CHID7"
17997 .scindex IIDmanrou1 "&(manualroute)& router"
17998 .scindex IIDmanrou2 "routers" "&(manualroute)&"
17999 .cindex "domain" "manually routing"
18000 The &(manualroute)& router is so-called because it provides a way of manually
18001 routing an address according to its domain. It is mainly used when you want to
18002 route addresses to remote hosts according to your own rules, bypassing the
18003 normal DNS routing that looks up MX records. However, &(manualroute)& can also
18004 route to local transports, a facility that may be useful if you want to save
18005 messages for dial-in hosts in local files.
18006
18007 The &(manualroute)& router compares a list of domain patterns with the domain
18008 it is trying to route. If there is no match, the router declines. Each pattern
18009 has associated with it a list of hosts and some other optional data, which may
18010 include a transport. The combination of a pattern and its data is called a
18011 &"routing rule"&. For patterns that do not have an associated transport, the
18012 generic &%transport%& option must specify a transport, unless the router is
18013 being used purely for verification (see &%verify_only%&).
18014
18015 .vindex "&$host$&"
18016 In the case of verification, matching the domain pattern is sufficient for the
18017 router to accept the address. When actually routing an address for delivery,
18018 an address that matches a domain pattern is queued for the associated
18019 transport. If the transport is not a local one, a host list must be associated
18020 with the pattern; IP addresses are looked up for the hosts, and these are
18021 passed to the transport along with the mail address. For local transports, a
18022 host list is optional. If it is present, it is passed in &$host$& as a single
18023 text string.
18024
18025 The list of routing rules can be provided as an inline string in
18026 &%route_list%&, or the data can be obtained by looking up the domain in a file
18027 or database by setting &%route_data%&. Only one of these settings may appear in
18028 any one instance of &(manualroute)&. The format of routing rules is described
18029 below, following the list of private options.
18030
18031
18032 .section "Private options for manualroute" "SECTprioptman"
18033
18034 .cindex "options" "&(manualroute)& router"
18035 The private options for the &(manualroute)& router are as follows:
18036
18037 .option host_all_ignored manualroute string defer
18038 See &%host_find_failed%&.
18039
18040 .option host_find_failed manualroute string freeze
18041 This option controls what happens when &(manualroute)& tries to find an IP
18042 address for a host, and the host does not exist. The option can be set to one
18043 of the following values:
18044 .code
18045 decline
18046 defer
18047 fail
18048 freeze
18049 ignore
18050 pass
18051 .endd
18052 The default (&"freeze"&) assumes that this state is a serious configuration
18053 error. The difference between &"pass"& and &"decline"& is that the former
18054 forces the address to be passed to the next router (or the router defined by
18055 &%pass_router%&),
18056 .oindex "&%more%&"
18057 overriding &%no_more%&, whereas the latter passes the address to the next
18058 router only if &%more%& is true.
18059
18060 The value &"ignore"& causes Exim to completely ignore a host whose IP address
18061 cannot be found. If all the hosts in the list are ignored, the behaviour is
18062 controlled by the &%host_all_ignored%& option. This takes the same values
18063 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
18064
18065 The &%host_find_failed%& option applies only to a definite &"does not exist"&
18066 state; if a host lookup gets a temporary error, delivery is deferred unless the
18067 generic &%pass_on_timeout%& option is set.
18068
18069
18070 .option hosts_randomize manualroute boolean false
18071 .cindex "randomized host list"
18072 .cindex "host" "list of; randomized"
18073 If this option is set, the order of the items in a host list in a routing rule
18074 is randomized each time the list is used, unless an option in the routing rule
18075 overrides (see below). Randomizing the order of a host list can be used to do
18076 crude load sharing. However, if more than one mail address is routed by the
18077 same router to the same host list, the host lists are considered to be the same
18078 (even though they may be randomized into different orders) for the purpose of
18079 deciding whether to batch the deliveries into a single SMTP transaction.
18080
18081 When &%hosts_randomize%& is true, a host list may be split
18082 into groups whose order is separately randomized. This makes it possible to
18083 set up MX-like behaviour. The boundaries between groups are indicated by an
18084 item that is just &`+`& in the host list. For example:
18085 .code
18086 route_list = * host1:host2:host3:+:host4:host5
18087 .endd
18088 The order of the first three hosts and the order of the last two hosts is
18089 randomized for each use, but the first three always end up before the last two.
18090 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
18091 randomized host list is passed to an &(smtp)& transport that also has
18092 &%hosts_randomize set%&, the list is not re-randomized.
18093
18094
18095 .option route_data manualroute string&!! unset
18096 If this option is set, it must expand to yield the data part of a routing rule.
18097 Typically, the expansion string includes a lookup based on the domain. For
18098 example:
18099 .code
18100 route_data = ${lookup{$domain}dbm{/etc/routes}}
18101 .endd
18102 If the expansion is forced to fail, or the result is an empty string, the
18103 router declines. Other kinds of expansion failure cause delivery to be
18104 deferred.
18105
18106
18107 .option route_list manualroute "string list" unset
18108 This string is a list of routing rules, in the form defined below. Note that,
18109 unlike most string lists, the items are separated by semicolons. This is so
18110 that they may contain colon-separated host lists.
18111
18112
18113 .option same_domain_copy_routing manualroute boolean false
18114 .cindex "address" "copying routing"
18115 Addresses with the same domain are normally routed by the &(manualroute)&
18116 router to the same list of hosts. However, this cannot be presumed, because the
18117 router options and preconditions may refer to the local part of the address. By
18118 default, therefore, Exim routes each address in a message independently. DNS
18119 servers run caches, so repeated DNS lookups are not normally expensive, and in
18120 any case, personal messages rarely have more than a few recipients.
18121
18122 If you are running mailing lists with large numbers of subscribers at the same
18123 domain, and you are using a &(manualroute)& router which is independent of the
18124 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
18125 lookups for identical domains in one message. In this case, when
18126 &(manualroute)& routes an address to a remote transport, any other unrouted
18127 addresses in the message that have the same domain are automatically given the
18128 same routing without processing them independently. However, this is only done
18129 if &%headers_add%& and &%headers_remove%& are unset.
18130
18131
18132
18133
18134 .section "Routing rules in route_list" "SECID120"
18135 The value of &%route_list%& is a string consisting of a sequence of routing
18136 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
18137 entered as two semicolons. Alternatively, the list separator can be changed as
18138 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
18139 Empty rules are ignored. The format of each rule is
18140 .display
18141 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
18142 .endd
18143 The following example contains two rules, each with a simple domain pattern and
18144 no options:
18145 .code
18146 route_list = \
18147 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
18148 thes.ref.example mail-3.ref.example:mail-4.ref.example
18149 .endd
18150 The three parts of a rule are separated by white space. The pattern and the
18151 list of hosts can be enclosed in quotes if necessary, and if they are, the
18152 usual quoting rules apply. Each rule in a &%route_list%& must start with a
18153 single domain pattern, which is the only mandatory item in the rule. The
18154 pattern is in the same format as one item in a domain list (see section
18155 &<<SECTdomainlist>>&),
18156 except that it may not be the name of an interpolated file.
18157 That is, it may be wildcarded, or a regular expression, or a file or database
18158 lookup (with semicolons doubled, because of the use of semicolon as a separator
18159 in a &%route_list%&).
18160
18161 The rules in &%route_list%& are searched in order until one of the patterns
18162 matches the domain that is being routed. The list of hosts and then options are
18163 then used as described below. If there is no match, the router declines. When
18164 &%route_list%& is set, &%route_data%& must not be set.
18165
18166
18167
18168 .section "Routing rules in route_data" "SECID121"
18169 The use of &%route_list%& is convenient when there are only a small number of
18170 routing rules. For larger numbers, it is easier to use a file or database to
18171 hold the routing information, and use the &%route_data%& option instead.
18172 The value of &%route_data%& is a list of hosts, followed by (optional) options.
18173 Most commonly, &%route_data%& is set as a string that contains an
18174 expansion lookup. For example, suppose we place two routing rules in a file
18175 like this:
18176 .code
18177 dict.ref.example: mail-1.ref.example:mail-2.ref.example
18178 thes.ref.example: mail-3.ref.example:mail-4.ref.example
18179 .endd
18180 This data can be accessed by setting
18181 .code
18182 route_data = ${lookup{$domain}lsearch{/the/file/name}}
18183 .endd
18184 Failure of the lookup results in an empty string, causing the router to
18185 decline. However, you do not have to use a lookup in &%route_data%&. The only
18186 requirement is that the result of expanding the string is a list of hosts,
18187 possibly followed by options, separated by white space. The list of hosts must
18188 be enclosed in quotes if it contains white space.
18189
18190
18191
18192
18193 .section "Format of the list of hosts" "SECID122"
18194 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
18195 always separately expanded before use. If the expansion fails, the router
18196 declines. The result of the expansion must be a colon-separated list of names
18197 and/or IP addresses, optionally also including ports. The format of each item
18198 in the list is described in the next section. The list separator can be changed
18199 as described in section &<<SECTlistconstruct>>&.
18200
18201 If the list of hosts was obtained from a &%route_list%& item, the following
18202 variables are set during its expansion:
18203
18204 .ilist
18205 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
18206 If the domain was matched against a regular expression, the numeric variables
18207 &$1$&, &$2$&, etc. may be set. For example:
18208 .code
18209 route_list = ^domain(\d+) host-$1.text.example
18210 .endd
18211 .next
18212 &$0$& is always set to the entire domain.
18213 .next
18214 &$1$& is also set when partial matching is done in a file lookup.
18215
18216 .next
18217 .vindex "&$value$&"
18218 If the pattern that matched the domain was a lookup item, the data that was
18219 looked up is available in the expansion variable &$value$&. For example:
18220 .code
18221 route_list = lsearch;;/some/file.routes $value
18222 .endd
18223 .endlist
18224
18225 Note the doubling of the semicolon in the pattern that is necessary because
18226 semicolon is the default route list separator.
18227
18228
18229
18230 .section "Format of one host item" "SECTformatonehostitem"
18231 Each item in the list of hosts is either a host name or an IP address,
18232 optionally with an attached port number. When no port is given, an IP address
18233 is not enclosed in brackets. When a port is specified, it overrides the port
18234 specification on the transport. The port is separated from the name or address
18235 by a colon. This leads to some complications:
18236
18237 .ilist
18238 Because colon is the default separator for the list of hosts, either
18239 the colon that specifies a port must be doubled, or the list separator must
18240 be changed. The following two examples have the same effect:
18241 .code
18242 route_list = * "host1.tld::1225 : host2.tld::1226"
18243 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
18244 .endd
18245 .next
18246 When IPv6 addresses are involved, it gets worse, because they contain
18247 colons of their own. To make this case easier, it is permitted to
18248 enclose an IP address (either v4 or v6) in square brackets if a port
18249 number follows. For example:
18250 .code
18251 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
18252 .endd
18253 .endlist
18254
18255 .section "How the list of hosts is used" "SECThostshowused"
18256 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
18257 the hosts is tried, in the order specified, when carrying out the SMTP
18258 delivery. However, the order can be changed by setting the &%hosts_randomize%&
18259 option, either on the router (see section &<<SECTprioptman>>& above), or on the
18260 transport.
18261
18262 Hosts may be listed by name or by IP address. An unadorned name in the list of
18263 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
18264 interpreted as an indirection to a sublist of hosts obtained by looking up MX
18265 records in the DNS. For example:
18266 .code
18267 route_list = * x.y.z:p.q.r/MX:e.f.g
18268 .endd
18269 If this feature is used with a port specifier, the port must come last. For
18270 example:
18271 .code
18272 route_list = * dom1.tld/mx::1225
18273 .endd
18274 If the &%hosts_randomize%& option is set, the order of the items in the list is
18275 randomized before any lookups are done. Exim then scans the list; for any name
18276 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
18277 be an interface on the local host and the item is not the first in the list,
18278 Exim discards it and any subsequent items. If it is the first item, what
18279 happens is controlled by the
18280 .oindex "&%self%&" "in &(manualroute)& router"
18281 &%self%& option of the router.
18282
18283 A name on the list that is followed by &`/MX`& is replaced with the list of
18284 hosts obtained by looking up MX records for the name. This is always a DNS
18285 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
18286 below) are not relevant here. The order of these hosts is determined by the
18287 preference values in the MX records, according to the usual rules. Because
18288 randomizing happens before the MX lookup, it does not affect the order that is
18289 defined by MX preferences.
18290
18291 If the local host is present in the sublist obtained from MX records, but is
18292 not the most preferred host in that list, it and any equally or less
18293 preferred hosts are removed before the sublist is inserted into the main list.
18294
18295 If the local host is the most preferred host in the MX list, what happens
18296 depends on where in the original list of hosts the &`/MX`& item appears. If it
18297 is not the first item (that is, there are previous hosts in the main list),
18298 Exim discards this name and any subsequent items in the main list.
18299
18300 If the MX item is first in the list of hosts, and the local host is the
18301 most preferred host, what happens is controlled by the &%self%& option of the
18302 router.
18303
18304 DNS failures when lookup up the MX records are treated in the same way as DNS
18305 failures when looking up IP addresses: &%pass_on_timeout%& and
18306 &%host_find_failed%& are used when relevant.
18307
18308 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
18309 whether obtained from an MX lookup or not.
18310
18311
18312
18313 .section "How the options are used" "SECThowoptused"
18314 The options are a sequence of words; in practice no more than three are ever
18315 present. One of the words can be the name of a transport; this overrides the
18316 &%transport%& option on the router for this particular routing rule only. The
18317 other words (if present) control randomization of the list of hosts on a
18318 per-rule basis, and how the IP addresses of the hosts are to be found when
18319 routing to a remote transport. These options are as follows:
18320
18321 .ilist
18322 &%randomize%&: randomize the order of the hosts in this list, overriding the
18323 setting of &%hosts_randomize%& for this routing rule only.
18324 .next
18325 &%no_randomize%&: do not randomize the order of the hosts in this list,
18326 overriding the setting of &%hosts_randomize%& for this routing rule only.
18327 .next
18328 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
18329 find IP addresses. This function may ultimately cause a DNS lookup, but it may
18330 also look in &_/etc/hosts_& or other sources of information.
18331 .next
18332 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
18333 no address records are found. If there is a temporary DNS error (such as a
18334 timeout), delivery is deferred.
18335 .endlist
18336
18337 For example:
18338 .code
18339 route_list = domain1 host1:host2:host3 randomize bydns;\
18340 domain2 host4:host5
18341 .endd
18342 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
18343 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
18344 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
18345 or &[gethostbyname()]&, and the result of the lookup is the result of that
18346 call.
18347
18348 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
18349 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
18350 instead of TRY_AGAIN. That is why the default action is to try a DNS
18351 lookup first. Only if that gives a definite &"no such host"& is the local
18352 function called.
18353
18354
18355
18356 If no IP address for a host can be found, what happens is controlled by the
18357 &%host_find_failed%& option.
18358
18359 .vindex "&$host$&"
18360 When an address is routed to a local transport, IP addresses are not looked up.
18361 The host list is passed to the transport in the &$host$& variable.
18362
18363
18364
18365 .section "Manualroute examples" "SECID123"
18366 In some of the examples that follow, the presence of the &%remote_smtp%&
18367 transport, as defined in the default configuration file, is assumed:
18368
18369 .ilist
18370 .cindex "smart host" "example router"
18371 The &(manualroute)& router can be used to forward all external mail to a
18372 &'smart host'&. If you have set up, in the main part of the configuration, a
18373 named domain list that contains your local domains, for example:
18374 .code
18375 domainlist local_domains = my.domain.example
18376 .endd
18377 You can arrange for all other domains to be routed to a smart host by making
18378 your first router something like this:
18379 .code
18380 smart_route:
18381 driver = manualroute
18382 domains = !+local_domains
18383 transport = remote_smtp
18384 route_list = * smarthost.ref.example
18385 .endd
18386 This causes all non-local addresses to be sent to the single host
18387 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
18388 they are tried in order
18389 (but you can use &%hosts_randomize%& to vary the order each time).
18390 Another way of configuring the same thing is this:
18391 .code
18392 smart_route:
18393 driver = manualroute
18394 transport = remote_smtp
18395 route_list = !+local_domains smarthost.ref.example
18396 .endd
18397 There is no difference in behaviour between these two routers as they stand.
18398 However, they behave differently if &%no_more%& is added to them. In the first
18399 example, the router is skipped if the domain does not match the &%domains%&
18400 precondition; the following router is always tried. If the router runs, it
18401 always matches the domain and so can never decline. Therefore, &%no_more%&
18402 would have no effect. In the second case, the router is never skipped; it
18403 always runs. However, if it doesn't match the domain, it declines. In this case
18404 &%no_more%& would prevent subsequent routers from running.
18405
18406 .next
18407 .cindex "mail hub example"
18408 A &'mail hub'& is a host which receives mail for a number of domains via MX
18409 records in the DNS and delivers it via its own private routing mechanism. Often
18410 the final destinations are behind a firewall, with the mail hub being the one
18411 machine that can connect to machines both inside and outside the firewall. The
18412 &(manualroute)& router is usually used on a mail hub to route incoming messages
18413 to the correct hosts. For a small number of domains, the routing can be inline,
18414 using the &%route_list%& option, but for a larger number a file or database
18415 lookup is easier to manage.
18416
18417 If the domain names are in fact the names of the machines to which the mail is
18418 to be sent by the mail hub, the configuration can be quite simple. For
18419 example:
18420 .code
18421 hub_route:
18422 driver = manualroute
18423 transport = remote_smtp
18424 route_list = *.rhodes.tvs.example $domain
18425 .endd
18426 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
18427 whose names are the same as the mail domains. A similar approach can be taken
18428 if the host name can be obtained from the domain name by a string manipulation
18429 that the expansion facilities can handle. Otherwise, a lookup based on the
18430 domain can be used to find the host:
18431 .code
18432 through_firewall:
18433 driver = manualroute
18434 transport = remote_smtp
18435 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
18436 .endd
18437 The result of the lookup must be the name or IP address of the host (or
18438 hosts) to which the address is to be routed. If the lookup fails, the route
18439 data is empty, causing the router to decline. The address then passes to the
18440 next router.
18441
18442 .next
18443 .cindex "batched SMTP output example"
18444 .cindex "SMTP" "batched outgoing; example"
18445 You can use &(manualroute)& to deliver messages to pipes or files in batched
18446 SMTP format for onward transportation by some other means. This is one way of
18447 storing mail for a dial-up host when it is not connected. The route list entry
18448 can be as simple as a single domain name in a configuration like this:
18449 .code
18450 save_in_file:
18451 driver = manualroute
18452 transport = batchsmtp_appendfile
18453 route_list = saved.domain.example
18454 .endd
18455 though often a pattern is used to pick up more than one domain. If there are
18456 several domains or groups of domains with different transport requirements,
18457 different transports can be listed in the routing information:
18458 .code
18459 save_in_file:
18460 driver = manualroute
18461 route_list = \
18462 *.saved.domain1.example $domain batch_appendfile; \
18463 *.saved.domain2.example \
18464 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
18465 batch_pipe
18466 .endd
18467 .vindex "&$domain$&"
18468 .vindex "&$host$&"
18469 The first of these just passes the domain in the &$host$& variable, which
18470 doesn't achieve much (since it is also in &$domain$&), but the second does a
18471 file lookup to find a value to pass, causing the router to decline to handle
18472 the address if the lookup fails.
18473
18474 .next
18475 .cindex "UUCP" "example of router for"
18476 Routing mail directly to UUCP software is a specific case of the use of
18477 &(manualroute)& in a gateway to another mail environment. This is an example of
18478 one way it can be done:
18479 .code
18480 # Transport
18481 uucp:
18482 driver = pipe
18483 user = nobody
18484 command = /usr/local/bin/uux -r - \
18485 ${substr_-5:$host}!rmail ${local_part}
18486 return_fail_output = true
18487
18488 # Router
18489 uucphost:
18490 transport = uucp
18491 driver = manualroute
18492 route_data = \
18493 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
18494 .endd
18495 The file &_/usr/local/exim/uucphosts_& contains entries like
18496 .code
18497 darksite.ethereal.example: darksite.UUCP
18498 .endd
18499 It can be set up more simply without adding and removing &".UUCP"& but this way
18500 makes clear the distinction between the domain name
18501 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
18502 .endlist
18503 .ecindex IIDmanrou1
18504 .ecindex IIDmanrou2
18505
18506
18507
18508
18509
18510
18511
18512
18513 . ////////////////////////////////////////////////////////////////////////////
18514 . ////////////////////////////////////////////////////////////////////////////
18515
18516 .chapter "The queryprogram router" "CHAPdriverlast"
18517 .scindex IIDquerou1 "&(queryprogram)& router"
18518 .scindex IIDquerou2 "routers" "&(queryprogram)&"
18519 .cindex "routing" "by external program"
18520 The &(queryprogram)& router routes an address by running an external command
18521 and acting on its output. This is an expensive way to route, and is intended
18522 mainly for use in lightly-loaded systems, or for performing experiments.
18523 However, if it is possible to use the precondition options (&%domains%&,
18524 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
18525 be used in special cases, even on a busy host. There are the following private
18526 options:
18527 .cindex "options" "&(queryprogram)& router"
18528
18529 .option command queryprogram string&!! unset
18530 This option must be set. It specifies the command that is to be run. The
18531 command is split up into a command name and arguments, and then each is
18532 expanded separately (exactly as for a &(pipe)& transport, described in chapter
18533 &<<CHAPpipetransport>>&).
18534
18535
18536 .option command_group queryprogram string unset
18537 .cindex "gid (group id)" "in &(queryprogram)& router"
18538 This option specifies a gid to be set when running the command while routing an
18539 address for deliver. It must be set if &%command_user%& specifies a numerical
18540 uid. If it begins with a digit, it is interpreted as the numerical value of the
18541 gid. Otherwise it is looked up using &[getgrnam()]&.
18542
18543
18544 .option command_user queryprogram string unset
18545 .cindex "uid (user id)" "for &(queryprogram)&"
18546 This option must be set. It specifies the uid which is set when running the
18547 command while routing an address for delivery. If the value begins with a digit,
18548 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
18549 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
18550 not set, a value for the gid also.
18551
18552 &*Warning:*& Changing uid and gid is possible only when Exim is running as
18553 root, which it does during a normal delivery in a conventional configuration.
18554 However, when an address is being verified during message reception, Exim is
18555 usually running as the Exim user, not as root. If the &(queryprogram)& router
18556 is called from a non-root process, Exim cannot change uid or gid before running
18557 the command. In this circumstance the command runs under the current uid and
18558 gid.
18559
18560
18561 .option current_directory queryprogram string /
18562 This option specifies an absolute path which is made the current directory
18563 before running the command.
18564
18565
18566 .option timeout queryprogram time 1h
18567 If the command does not complete within the timeout period, its process group
18568 is killed and the message is frozen. A value of zero time specifies no
18569 timeout.
18570
18571
18572 The standard output of the command is connected to a pipe, which is read when
18573 the command terminates. It should consist of a single line of output,
18574 containing up to five fields, separated by white space. The maximum length of
18575 the line is 1023 characters. Longer lines are silently truncated. The first
18576 field is one of the following words (case-insensitive):
18577
18578 .ilist
18579 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
18580 below).
18581 .next
18582 &'Decline'&: the router declines; pass the address to the next router, unless
18583 &%no_more%& is set.
18584 .next
18585 &'Fail'&: routing failed; do not pass the address to any more routers. Any
18586 subsequent text on the line is an error message. If the router is run as part
18587 of address verification during an incoming SMTP message, the message is
18588 included in the SMTP response.
18589 .next
18590 &'Defer'&: routing could not be completed at this time; try again later. Any
18591 subsequent text on the line is an error message which is logged. It is not
18592 included in any SMTP response.
18593 .next
18594 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
18595 .next
18596 &'Pass'&: pass the address to the next router (or the router specified by
18597 &%pass_router%&), overriding &%no_more%&.
18598 .next
18599 &'Redirect'&: the message is redirected. The remainder of the line is a list of
18600 new addresses, which are routed independently, starting with the first router,
18601 or the router specified by &%redirect_router%&, if set.
18602 .endlist
18603
18604 When the first word is &'accept'&, the remainder of the line consists of a
18605 number of keyed data values, as follows (split into two lines here, to fit on
18606 the page):
18607 .code
18608 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
18609 LOOKUP=byname|bydns DATA=<text>
18610 .endd
18611 The data items can be given in any order, and all are optional. If no transport
18612 is included, the transport specified by the generic &%transport%& option is
18613 used. The list of hosts and the lookup type are needed only if the transport is
18614 an &(smtp)& transport that does not itself supply a list of hosts.
18615
18616 The format of the list of hosts is the same as for the &(manualroute)& router.
18617 As well as host names and IP addresses with optional port numbers, as described
18618 in section &<<SECTformatonehostitem>>&, it may contain names followed by
18619 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
18620 (see section &<<SECThostshowused>>&).
18621
18622 If the lookup type is not specified, Exim behaves as follows when trying to
18623 find an IP address for each host: First, a DNS lookup is done. If this yields
18624 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
18625 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
18626 result of the lookup is the result of that call.
18627
18628 .vindex "&$address_data$&"
18629 If the DATA field is set, its value is placed in the &$address_data$&
18630 variable. For example, this return line
18631 .code
18632 accept hosts=x1.y.example:x2.y.example data="rule1"
18633 .endd
18634 routes the address to the default transport, passing a list of two hosts. When
18635 the transport runs, the string &"rule1"& is in &$address_data$&.
18636 .ecindex IIDquerou1
18637 .ecindex IIDquerou2
18638
18639
18640
18641
18642 . ////////////////////////////////////////////////////////////////////////////
18643 . ////////////////////////////////////////////////////////////////////////////
18644
18645 .chapter "The redirect router" "CHAPredirect"
18646 .scindex IIDredrou1 "&(redirect)& router"
18647 .scindex IIDredrou2 "routers" "&(redirect)&"
18648 .cindex "alias file" "in a &(redirect)& router"
18649 .cindex "address redirection" "&(redirect)& router"
18650 The &(redirect)& router handles several kinds of address redirection. Its most
18651 common uses are for resolving local part aliases from a central alias file
18652 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
18653 files, but it has many other potential uses. The incoming address can be
18654 redirected in several different ways:
18655
18656 .ilist
18657 It can be replaced by one or more new addresses which are themselves routed
18658 independently.
18659 .next
18660 It can be routed to be delivered to a given file or directory.
18661 .next
18662 It can be routed to be delivered to a specified pipe command.
18663 .next
18664 It can cause an automatic reply to be generated.
18665 .next
18666 It can be forced to fail, optionally with a custom error message.
18667 .next
18668 It can be temporarily deferred, optionally with a custom message.
18669 .next
18670 It can be discarded.
18671 .endlist
18672
18673 The generic &%transport%& option must not be set for &(redirect)& routers.
18674 However, there are some private options which define transports for delivery to
18675 files and pipes, and for generating autoreplies. See the &%file_transport%&,
18676 &%pipe_transport%& and &%reply_transport%& descriptions below.
18677
18678
18679
18680 .section "Redirection data" "SECID124"
18681 The router operates by interpreting a text string which it obtains either by
18682 expanding the contents of the &%data%& option, or by reading the entire
18683 contents of a file whose name is given in the &%file%& option. These two
18684 options are mutually exclusive. The first is commonly used for handling system
18685 aliases, in a configuration like this:
18686 .code
18687 system_aliases:
18688 driver = redirect
18689 data = ${lookup{$local_part}lsearch{/etc/aliases}}
18690 .endd
18691 If the lookup fails, the expanded string in this example is empty. When the
18692 expansion of &%data%& results in an empty string, the router declines. A forced
18693 expansion failure also causes the router to decline; other expansion failures
18694 cause delivery to be deferred.
18695
18696 A configuration using &%file%& is commonly used for handling users'
18697 &_.forward_& files, like this:
18698 .code
18699 userforward:
18700 driver = redirect
18701 check_local_user
18702 file = $home/.forward
18703 no_verify
18704 .endd
18705 If the file does not exist, or causes no action to be taken (for example, it is
18706 empty or consists only of comments), the router declines. &*Warning*&: This
18707 is not the case when the file contains syntactically valid items that happen to
18708 yield empty addresses, for example, items containing only RFC 2822 address
18709 comments.
18710
18711
18712
18713 .section "Forward files and address verification" "SECID125"
18714 .cindex "address redirection" "while verifying"
18715 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
18716 &_.forward_& files, as in the example above. There are two reasons for this:
18717
18718 .ilist
18719 When Exim is receiving an incoming SMTP message from a remote host, it is
18720 running under the Exim uid, not as root. Exim is unable to change uid to read
18721 the file as the user, and it may not be able to read it as the Exim user. So in
18722 practice the router may not be able to operate.
18723 .next
18724 However, even when the router can operate, the existence of a &_.forward_& file
18725 is unimportant when verifying an address. What should be checked is whether the
18726 local part is a valid user name or not. Cutting out the redirection processing
18727 saves some resources.
18728 .endlist
18729
18730
18731
18732
18733
18734
18735 .section "Interpreting redirection data" "SECID126"
18736 .cindex "Sieve filter" "specifying in redirection data"
18737 .cindex "filter" "specifying in redirection data"
18738 The contents of the data string, whether obtained from &%data%& or &%file%&,
18739 can be interpreted in two different ways:
18740
18741 .ilist
18742 If the &%allow_filter%& option is set true, and the data begins with the text
18743 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
18744 &'filtering'& instructions in the form of an Exim or Sieve filter file,
18745 respectively. Details of the syntax and semantics of filter files are described
18746 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
18747 document is intended for use by end users.
18748 .next
18749 Otherwise, the data must be a comma-separated list of redirection items, as
18750 described in the next section.
18751 .endlist
18752
18753 When a message is redirected to a file (a &"mail folder"&), the file name given
18754 in a non-filter redirection list must always be an absolute path. A filter may
18755 generate a relative path &-- how this is handled depends on the transport's
18756 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
18757 for the &(appendfile)& transport.
18758
18759
18760
18761 .section "Items in a non-filter redirection list" "SECTitenonfilred"
18762 .cindex "address redirection" "non-filter list items"
18763 When the redirection data is not an Exim or Sieve filter, for example, if it
18764 comes from a conventional alias or forward file, it consists of a list of
18765 addresses, file names, pipe commands, or certain special items (see section
18766 &<<SECTspecitredli>>& below). The special items can be individually enabled or
18767 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
18768 depending on their default values. The items in the list are separated by
18769 commas or newlines.
18770 If a comma is required in an item, the entire item must be enclosed in double
18771 quotes.
18772
18773 Lines starting with a # character are comments, and are ignored, and # may
18774 also appear following a comma, in which case everything between the # and the
18775 next newline character is ignored.
18776
18777 If an item is entirely enclosed in double quotes, these are removed. Otherwise
18778 double quotes are retained because some forms of mail address require their use
18779 (but never to enclose the entire address). In the following description,
18780 &"item"& refers to what remains after any surrounding double quotes have been
18781 removed.
18782
18783 .vindex "&$local_part$&"
18784 &*Warning*&: If you use an Exim expansion to construct a redirection address,
18785 and the expansion contains a reference to &$local_part$&, you should make use
18786 of the &%quote_local_part%& expansion operator, in case the local part contains
18787 special characters. For example, to redirect all mail for the domain
18788 &'obsolete.example'&, retaining the existing local part, you could use this
18789 setting:
18790 .code
18791 data = ${quote_local_part:$local_part}@newdomain.example
18792 .endd
18793
18794
18795 .section "Redirecting to a local mailbox" "SECTredlocmai"
18796 .cindex "routing" "loops in"
18797 .cindex "loop" "while routing, avoidance of"
18798 .cindex "address redirection" "to local mailbox"
18799 A redirection item may safely be the same as the address currently under
18800 consideration. This does not cause a routing loop, because a router is
18801 automatically skipped if any ancestor of the address that is being processed
18802 is the same as the current address and was processed by the current router.
18803 Such an address is therefore passed to the following routers, so it is handled
18804 as if there were no redirection. When making this loop-avoidance test, the
18805 complete local part, including any prefix or suffix, is used.
18806
18807 .cindex "address redirection" "local part without domain"
18808 Specifying the same local part without a domain is a common usage in personal
18809 filter files when the user wants to have messages delivered to the local
18810 mailbox and also forwarded elsewhere. For example, the user whose login is
18811 &'cleo'& might have a &_.forward_& file containing this:
18812 .code
18813 cleo, cleopatra@egypt.example
18814 .endd
18815 .cindex "backslash in alias file"
18816 .cindex "alias file" "backslash in"
18817 For compatibility with other MTAs, such unqualified local parts may be
18818 preceded by &"\"&, but this is not a requirement for loop prevention. However,
18819 it does make a difference if more than one domain is being handled
18820 synonymously.
18821
18822 If an item begins with &"\"& and the rest of the item parses as a valid RFC
18823 2822 address that does not include a domain, the item is qualified using the
18824 domain of the incoming address. In the absence of a leading &"\"&, unqualified
18825 addresses are qualified using the value in &%qualify_recipient%&, but you can
18826 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
18827
18828 Care must be taken if there are alias names for local users.
18829 Consider an MTA handling a single local domain where the system alias file
18830 contains:
18831 .code
18832 Sam.Reman: spqr
18833 .endd
18834 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
18835 messages in the local mailbox, and also forward copies elsewhere. He creates
18836 this forward file:
18837 .code
18838 Sam.Reman, spqr@reme.elsewhere.example
18839 .endd
18840 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
18841 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
18842 second time round, because it has previously routed it,
18843 and the following routers presumably cannot handle the alias. The forward file
18844 should really contain
18845 .code
18846 spqr, spqr@reme.elsewhere.example
18847 .endd
18848 but because this is such a common error, the &%check_ancestor%& option (see
18849 below) exists to provide a way to get round it. This is normally set on a
18850 &(redirect)& router that is handling users' &_.forward_& files.
18851
18852
18853
18854 .section "Special items in redirection lists" "SECTspecitredli"
18855 In addition to addresses, the following types of item may appear in redirection
18856 lists (that is, in non-filter redirection data):
18857
18858 .ilist
18859 .cindex "pipe" "in redirection list"
18860 .cindex "address redirection" "to pipe"
18861 An item is treated as a pipe command if it begins with &"|"& and does not parse
18862 as a valid RFC 2822 address that includes a domain. A transport for running the
18863 command must be specified by the &%pipe_transport%& option.
18864 Normally, either the router or the transport specifies a user and a group under
18865 which to run the delivery. The default is to use the Exim user and group.
18866
18867 Single or double quotes can be used for enclosing the individual arguments of
18868 the pipe command; no interpretation of escapes is done for single quotes. If
18869 the command contains a comma character, it is necessary to put the whole item
18870 in double quotes, for example:
18871 .code
18872 "|/some/command ready,steady,go"
18873 .endd
18874 since items in redirection lists are terminated by commas. Do not, however,
18875 quote just the command. An item such as
18876 .code
18877 |"/some/command ready,steady,go"
18878 .endd
18879 is interpreted as a pipe with a rather strange command name, and no arguments.
18880
18881 Note that the above example assumes that the text comes from a lookup source
18882 of some sort, so that the quotes are part of the data. If composing a
18883 redirect router with a &%data%& option directly specifying this command, the
18884 quotes will be used by the configuration parser to define the extent of one
18885 string, but will not be passed down into the redirect router itself. There
18886 are two main approaches to get around this: escape quotes to be part of the
18887 data itself, or avoid using this mechanism and instead create a custom
18888 transport with the &%command%& option set and reference that transport from
18889 an &%accept%& router.
18890
18891 .next
18892 .cindex "file" "in redirection list"
18893 .cindex "address redirection" "to file"
18894 An item is interpreted as a path name if it begins with &"/"& and does not
18895 parse as a valid RFC 2822 address that includes a domain. For example,
18896 .code
18897 /home/world/minbari
18898 .endd
18899 is treated as a file name, but
18900 .code
18901 /s=molari/o=babylon/@x400gate.way
18902 .endd
18903 is treated as an address. For a file name, a transport must be specified using
18904 the &%file_transport%& option. However, if the generated path name ends with a
18905 forward slash character, it is interpreted as a directory name rather than a
18906 file name, and &%directory_transport%& is used instead.
18907
18908 Normally, either the router or the transport specifies a user and a group under
18909 which to run the delivery. The default is to use the Exim user and group.
18910
18911 .cindex "&_/dev/null_&"
18912 However, if a redirection item is the path &_/dev/null_&, delivery to it is
18913 bypassed at a high level, and the log entry shows &"**bypassed**"&
18914 instead of a transport name. In this case the user and group are not used.
18915
18916 .next
18917 .cindex "included address list"
18918 .cindex "address redirection" "included external list"
18919 If an item is of the form
18920 .code
18921 :include:<path name>
18922 .endd
18923 a list of further items is taken from the given file and included at that
18924 point. &*Note*&: Such a file can not be a filter file; it is just an
18925 out-of-line addition to the list. The items in the included list are separated
18926 by commas or newlines and are not subject to expansion. If this is the first
18927 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
18928 the alias name. This example is incorrect:
18929 .code
18930 list1 :include:/opt/lists/list1
18931 .endd
18932 It must be given as
18933 .code
18934 list1: :include:/opt/lists/list1
18935 .endd
18936 .next
18937 .cindex "address redirection" "to black hole"
18938 Sometimes you want to throw away mail to a particular local part. Making the
18939 &%data%& option expand to an empty string does not work, because that causes
18940 the router to decline. Instead, the alias item
18941 .cindex "black hole"
18942 .cindex "abandoning mail"
18943 &':blackhole:'& can be used. It does what its name implies. No delivery is
18944 done, and no error message is generated. This has the same effect as specifing
18945 &_/dev/null_& as a destination, but it can be independently disabled.
18946
18947 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
18948 delivery is done for the original local part, even if other redirection items
18949 are present. If you are generating a multi-item list (for example, by reading a
18950 database) and need the ability to provide a no-op item, you must use
18951 &_/dev/null_&.
18952
18953 .next
18954 .cindex "delivery" "forcing failure"
18955 .cindex "delivery" "forcing deferral"
18956 .cindex "failing delivery" "forcing"
18957 .cindex "deferred delivery, forcing"
18958 .cindex "customizing" "failure message"
18959 An attempt to deliver a particular address can be deferred or forced to fail by
18960 redirection items of the form
18961 .code
18962 :defer:
18963 :fail:
18964 .endd
18965 respectively. When a redirection list contains such an item, it applies
18966 to the entire redirection; any other items in the list are ignored. Any
18967 text following &':fail:'& or &':defer:'& is placed in the error text
18968 associated with the failure. For example, an alias file might contain:
18969 .code
18970 X.Employee: :fail: Gone away, no forwarding address
18971 .endd
18972 In the case of an address that is being verified from an ACL or as the subject
18973 of a
18974 .cindex "VRFY" "error text, display of"
18975 VRFY command, the text is included in the SMTP error response by
18976 default.
18977 .cindex "EXPN" "error text, display of"
18978 The text is not included in the response to an EXPN command. In non-SMTP cases
18979 the text is included in the error message that Exim generates.
18980
18981 .cindex "SMTP" "error codes"
18982 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
18983 &':fail:'&. However, if the message starts with three digits followed by a
18984 space, optionally followed by an extended code of the form &'n.n.n'&, also
18985 followed by a space, and the very first digit is the same as the default error
18986 code, the code from the message is used instead. If the very first digit is
18987 incorrect, a panic error is logged, and the default code is used. You can
18988 suppress the use of the supplied code in a redirect router by setting the
18989 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
18990 ignored.
18991
18992 .vindex "&$acl_verify_message$&"
18993 In an ACL, an explicitly provided message overrides the default, but the
18994 default message is available in the variable &$acl_verify_message$& and can
18995 therefore be included in a custom message if this is desired.
18996
18997 Normally the error text is the rest of the redirection list &-- a comma does
18998 not terminate it &-- but a newline does act as a terminator. Newlines are not
18999 normally present in alias expansions. In &(lsearch)& lookups they are removed
19000 as part of the continuation process, but they may exist in other kinds of
19001 lookup and in &':include:'& files.
19002
19003 During routing for message delivery (as opposed to verification), a redirection
19004 containing &':fail:'& causes an immediate failure of the incoming address,
19005 whereas &':defer:'& causes the message to remain on the queue so that a
19006 subsequent delivery attempt can happen at a later time. If an address is
19007 deferred for too long, it will ultimately fail, because the normal retry
19008 rules still apply.
19009
19010 .next
19011 .cindex "alias file" "exception to default"
19012 Sometimes it is useful to use a single-key search type with a default (see
19013 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
19014 for exceptions to the default. These can be handled by aliasing them to
19015 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
19016 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
19017 results in an empty redirection list has the same effect.
19018 .endlist
19019
19020
19021 .section "Duplicate addresses" "SECTdupaddr"
19022 .cindex "duplicate addresses"
19023 .cindex "address duplicate, discarding"
19024 .cindex "pipe" "duplicated"
19025 Exim removes duplicate addresses from the list to which it is delivering, so as
19026 to deliver just one copy to each address. This does not apply to deliveries
19027 routed to pipes by different immediate parent addresses, but an indirect
19028 aliasing scheme of the type
19029 .code
19030 pipe: |/some/command $local_part
19031 localpart1: pipe
19032 localpart2: pipe
19033 .endd
19034 does not work with a message that is addressed to both local parts, because
19035 when the second is aliased to the intermediate local part &"pipe"& it gets
19036 discarded as being the same as a previously handled address. However, a scheme
19037 such as
19038 .code
19039 localpart1: |/some/command $local_part
19040 localpart2: |/some/command $local_part
19041 .endd
19042 does result in two different pipe deliveries, because the immediate parents of
19043 the pipes are distinct.
19044
19045
19046
19047 .section "Repeated redirection expansion" "SECID128"
19048 .cindex "repeated redirection expansion"
19049 .cindex "address redirection" "repeated for each delivery attempt"
19050 When a message cannot be delivered to all of its recipients immediately,
19051 leading to two or more delivery attempts, redirection expansion is carried out
19052 afresh each time for those addresses whose children were not all previously
19053 delivered. If redirection is being used as a mailing list, this can lead to new
19054 members of the list receiving copies of old messages. The &%one_time%& option
19055 can be used to avoid this.
19056
19057
19058 .section "Errors in redirection lists" "SECID129"
19059 .cindex "address redirection" "errors"
19060 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
19061 error is skipped, and an entry is written to the main log. This may be useful
19062 for mailing lists that are automatically managed. Otherwise, if an error is
19063 detected while generating the list of new addresses, the original address is
19064 deferred. See also &%syntax_errors_to%&.
19065
19066
19067
19068 .section "Private options for the redirect router" "SECID130"
19069
19070 .cindex "options" "&(redirect)& router"
19071 The private options for the &(redirect)& router are as follows:
19072
19073
19074 .option allow_defer redirect boolean false
19075 Setting this option allows the use of &':defer:'& in non-filter redirection
19076 data, or the &%defer%& command in an Exim filter file.
19077
19078
19079 .option allow_fail redirect boolean false
19080 .cindex "failing delivery" "from filter"
19081 If this option is true, the &':fail:'& item can be used in a redirection list,
19082 and the &%fail%& command may be used in an Exim filter file.
19083
19084
19085 .option allow_filter redirect boolean false
19086 .cindex "filter" "enabling use of"
19087 .cindex "Sieve filter" "enabling use of"
19088 Setting this option allows Exim to interpret redirection data that starts with
19089 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
19090 are some features of Exim filter files that some administrators may wish to
19091 lock out; see the &%forbid_filter_%&&'xxx'& options below.
19092
19093 It is also possible to lock out Exim filters or Sieve filters while allowing
19094 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
19095
19096
19097 The filter is run using the uid and gid set by the generic &%user%& and
19098 &%group%& options. These take their defaults from the password data if
19099 &%check_local_user%& is set, so in the normal case of users' personal filter
19100 files, the filter is run as the relevant user. When &%allow_filter%& is set
19101 true, Exim insists that either &%check_local_user%& or &%user%& is set.
19102
19103
19104
19105 .option allow_freeze redirect boolean false
19106 .cindex "freezing messages" "allowing in filter"
19107 Setting this option allows the use of the &%freeze%& command in an Exim filter.
19108 This command is more normally encountered in system filters, and is disabled by
19109 default for redirection filters because it isn't something you usually want to
19110 let ordinary users do.
19111
19112
19113
19114 .option check_ancestor redirect boolean false
19115 This option is concerned with handling generated addresses that are the same
19116 as some address in the list of redirection ancestors of the current address.
19117 Although it is turned off by default in the code, it is set in the default
19118 configuration file for handling users' &_.forward_& files. It is recommended
19119 for this use of the &(redirect)& router.
19120
19121 When &%check_ancestor%& is set, if a generated address (including the domain)
19122 is the same as any ancestor of the current address, it is replaced by a copy of
19123 the current address. This helps in the case where local part A is aliased to B,
19124 and B has a &_.forward_& file pointing back to A. For example, within a single
19125 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
19126 &_&~jb/.forward_& contains:
19127 .code
19128 \Joe.Bloggs, <other item(s)>
19129 .endd
19130 Without the &%check_ancestor%& setting, either local part (&"jb"& or
19131 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
19132 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
19133 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
19134 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
19135 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
19136 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
19137 original address. See also the &%repeat_use%& option below.
19138
19139
19140 .option check_group redirect boolean "see below"
19141 When the &%file%& option is used, the group owner of the file is checked only
19142 when this option is set. The permitted groups are those listed in the
19143 &%owngroups%& option, together with the user's default group if
19144 &%check_local_user%& is set. If the file has the wrong group, routing is
19145 deferred. The default setting for this option is true if &%check_local_user%&
19146 is set and the &%modemask%& option permits the group write bit, or if the
19147 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
19148
19149
19150
19151 .option check_owner redirect boolean "see below"
19152 When the &%file%& option is used, the owner of the file is checked only when
19153 this option is set. If &%check_local_user%& is set, the local user is
19154 permitted; otherwise the owner must be one of those listed in the &%owners%&
19155 option. The default value for this option is true if &%check_local_user%& or
19156 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
19157
19158
19159 .option data redirect string&!! unset
19160 This option is mutually exclusive with &%file%&. One or other of them must be
19161 set, but not both. The contents of &%data%& are expanded, and then used as the
19162 list of forwarding items, or as a set of filtering instructions. If the
19163 expansion is forced to fail, or the result is an empty string or a string that
19164 has no effect (consists entirely of comments), the router declines.
19165
19166 When filtering instructions are used, the string must begin with &"#Exim
19167 filter"&, and all comments in the string, including this initial one, must be
19168 terminated with newline characters. For example:
19169 .code
19170 data = #Exim filter\n\
19171 if $h_to: contains Exim then save $home/mail/exim endif
19172 .endd
19173 If you are reading the data from a database where newlines cannot be included,
19174 you can use the &${sg}$& expansion item to turn the escape string of your
19175 choice into a newline.
19176
19177
19178 .option directory_transport redirect string&!! unset
19179 A &(redirect)& router sets up a direct delivery to a directory when a path name
19180 ending with a slash is specified as a new &"address"&. The transport used is
19181 specified by this option, which, after expansion, must be the name of a
19182 configured transport. This should normally be an &(appendfile)& transport.
19183
19184
19185 .option file redirect string&!! unset
19186 This option specifies the name of a file that contains the redirection data. It
19187 is mutually exclusive with the &%data%& option. The string is expanded before
19188 use; if the expansion is forced to fail, the router declines. Other expansion
19189 failures cause delivery to be deferred. The result of a successful expansion
19190 must be an absolute path. The entire file is read and used as the redirection
19191 data. If the data is an empty string or a string that has no effect (consists
19192 entirely of comments), the router declines.
19193
19194 .cindex "NFS" "checking for file existence"
19195 If the attempt to open the file fails with a &"does not exist"& error, Exim
19196 runs a check on the containing directory,
19197 unless &%ignore_enotdir%& is true (see below).
19198 If the directory does not appear to exist, delivery is deferred. This can
19199 happen when users' &_.forward_& files are in NFS-mounted directories, and there
19200 is a mount problem. If the containing directory does exist, but the file does
19201 not, the router declines.
19202
19203
19204 .option file_transport redirect string&!! unset
19205 .vindex "&$address_file$&"
19206 A &(redirect)& router sets up a direct delivery to a file when a path name not
19207 ending in a slash is specified as a new &"address"&. The transport used is
19208 specified by this option, which, after expansion, must be the name of a
19209 configured transport. This should normally be an &(appendfile)& transport. When
19210 it is running, the file name is in &$address_file$&.
19211
19212
19213 .option filter_prepend_home redirect boolean true
19214 When this option is true, if a &(save)& command in an Exim filter specifies a
19215 relative path, and &$home$& is defined, it is automatically prepended to the
19216 relative path. If this option is set false, this action does not happen. The
19217 relative path is then passed to the transport unmodified.
19218
19219
19220 .option forbid_blackhole redirect boolean false
19221 If this option is true, the &':blackhole:'& item may not appear in a
19222 redirection list.
19223
19224
19225 .option forbid_exim_filter redirect boolean false
19226 If this option is set true, only Sieve filters are permitted when
19227 &%allow_filter%& is true.
19228
19229
19230
19231
19232 .option forbid_file redirect boolean false
19233 .cindex "delivery" "to file; forbidding"
19234 .cindex "Sieve filter" "forbidding delivery to a file"
19235 .cindex "Sieve filter" "&""keep""& facility; disabling"
19236 If this option is true, this router may not generate a new address that
19237 specifies delivery to a local file or directory, either from a filter or from a
19238 conventional forward file. This option is forced to be true if &%one_time%& is
19239 set. It applies to Sieve filters as well as to Exim filters, but if true, it
19240 locks out the Sieve's &"keep"& facility.
19241
19242
19243 .option forbid_filter_dlfunc redirect boolean false
19244 .cindex "filter" "locking out certain features"
19245 If this option is true, string expansions in Exim filters are not allowed to
19246 make use of the &%dlfunc%& expansion facility to run dynamically loaded
19247 functions.
19248
19249 .option forbid_filter_existstest redirect boolean false
19250 .cindex "expansion" "statting a file"
19251 If this option is true, string expansions in Exim filters are not allowed to
19252 make use of the &%exists%& condition or the &%stat%& expansion item.
19253
19254 .option forbid_filter_logwrite redirect boolean false
19255 If this option is true, use of the logging facility in Exim filters is not
19256 permitted. Logging is in any case available only if the filter is being run
19257 under some unprivileged uid (which is normally the case for ordinary users'
19258 &_.forward_& files).
19259
19260
19261 .option forbid_filter_lookup redirect boolean false
19262 If this option is true, string expansions in Exim filter files are not allowed
19263 to make use of &%lookup%& items.
19264
19265
19266 .option forbid_filter_perl redirect boolean false
19267 This option has an effect only if Exim is built with embedded Perl support. If
19268 it is true, string expansions in Exim filter files are not allowed to make use
19269 of the embedded Perl support.
19270
19271
19272 .option forbid_filter_readfile redirect boolean false
19273 If this option is true, string expansions in Exim filter files are not allowed
19274 to make use of &%readfile%& items.
19275
19276
19277 .option forbid_filter_readsocket redirect boolean false
19278 If this option is true, string expansions in Exim filter files are not allowed
19279 to make use of &%readsocket%& items.
19280
19281
19282 .option forbid_filter_reply redirect boolean false
19283 If this option is true, this router may not generate an automatic reply
19284 message. Automatic replies can be generated only from Exim or Sieve filter
19285 files, not from traditional forward files. This option is forced to be true if
19286 &%one_time%& is set.
19287
19288
19289 .option forbid_filter_run redirect boolean false
19290 If this option is true, string expansions in Exim filter files are not allowed
19291 to make use of &%run%& items.
19292
19293
19294 .option forbid_include redirect boolean false
19295 If this option is true, items of the form
19296 .code
19297 :include:<path name>
19298 .endd
19299 are not permitted in non-filter redirection lists.
19300
19301
19302 .option forbid_pipe redirect boolean false
19303 .cindex "delivery" "to pipe; forbidding"
19304 If this option is true, this router may not generate a new address which
19305 specifies delivery to a pipe, either from an Exim filter or from a conventional
19306 forward file. This option is forced to be true if &%one_time%& is set.
19307
19308
19309 .option forbid_sieve_filter redirect boolean false
19310 If this option is set true, only Exim filters are permitted when
19311 &%allow_filter%& is true.
19312
19313
19314 .cindex "SMTP" "error codes"
19315 .option forbid_smtp_code redirect boolean false
19316 If this option is set true, any SMTP error codes that are present at the start
19317 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
19318 the default codes (451 and 550, respectively) are always used.
19319
19320
19321
19322
19323 .option hide_child_in_errmsg redirect boolean false
19324 .cindex "bounce message" "redirection details; suppressing"
19325 If this option is true, it prevents Exim from quoting a child address if it
19326 generates a bounce or delay message for it. Instead it says &"an address
19327 generated from <&'the top level address'&>"&. Of course, this applies only to
19328 bounces generated locally. If a message is forwarded to another host, &'its'&
19329 bounce may well quote the generated address.
19330
19331
19332 .option ignore_eacces redirect boolean false
19333 .cindex "EACCES"
19334 If this option is set and an attempt to open a redirection file yields the
19335 EACCES error (permission denied), the &(redirect)& router behaves as if the
19336 file did not exist.
19337
19338
19339 .option ignore_enotdir redirect boolean false
19340 .cindex "ENOTDIR"
19341 If this option is set and an attempt to open a redirection file yields the
19342 ENOTDIR error (something on the path is not a directory), the &(redirect)&
19343 router behaves as if the file did not exist.
19344
19345 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
19346 router that has the &%file%& option set discovers that the file does not exist
19347 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
19348 against unmounted NFS directories. If the parent can not be statted, delivery
19349 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
19350 is set, because that option tells Exim to ignore &"something on the path is not
19351 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
19352 that some operating systems give ENOENT where others give ENOTDIR.
19353
19354
19355
19356 .option include_directory redirect string unset
19357 If this option is set, the path names of any &':include:'& items in a
19358 redirection list must start with this directory.
19359
19360
19361 .option modemask redirect "octal integer" 022
19362 This specifies mode bits which must not be set for a file specified by the
19363 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
19364
19365
19366 .option one_time redirect boolean false
19367 .cindex "one-time aliasing/forwarding expansion"
19368 .cindex "alias file" "one-time expansion"
19369 .cindex "forward file" "one-time expansion"
19370 .cindex "mailing lists" "one-time expansion"
19371 .cindex "address redirection" "one-time expansion"
19372 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
19373 files each time it tries to deliver a message causes a problem when one or more
19374 of the generated addresses fails be delivered at the first attempt. The problem
19375 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
19376 but of what happens when the redirection list changes during the time that the
19377 message is on Exim's queue. This is particularly true in the case of mailing
19378 lists, where new subscribers might receive copies of messages that were posted
19379 before they subscribed.
19380
19381 If &%one_time%& is set and any addresses generated by the router fail to
19382 deliver at the first attempt, the failing addresses are added to the message as
19383 &"top level"& addresses, and the parent address that generated them is marked
19384 &"delivered"&. Thus, redirection does not happen again at the next delivery
19385 attempt.
19386
19387 &*Warning 1*&: Any header line addition or removal that is specified by this
19388 router would be lost if delivery did not succeed at the first attempt. For this
19389 reason, the &%headers_add%& and &%headers_remove%& generic options are not
19390 permitted when &%one_time%& is set.
19391
19392 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
19393 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
19394 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
19395
19396 &*Warning 3*&: The &%unseen%& generic router option may not be set with
19397 &%one_time%&.
19398
19399 The original top-level address is remembered with each of the generated
19400 addresses, and is output in any log messages. However, any intermediate parent
19401 addresses are not recorded. This makes a difference to the log only if
19402 &%all_parents%& log selector is set. It is expected that &%one_time%& will
19403 typically be used for mailing lists, where there is normally just one level of
19404 expansion.
19405
19406
19407 .option owners redirect "string list" unset
19408 .cindex "ownership" "alias file"
19409 .cindex "ownership" "forward file"
19410 .cindex "alias file" "ownership"
19411 .cindex "forward file" "ownership"
19412 This specifies a list of permitted owners for the file specified by &%file%&.
19413 This list is in addition to the local user when &%check_local_user%& is set.
19414 See &%check_owner%& above.
19415
19416
19417 .option owngroups redirect "string list" unset
19418 This specifies a list of permitted groups for the file specified by &%file%&.
19419 The list is in addition to the local user's primary group when
19420 &%check_local_user%& is set. See &%check_group%& above.
19421
19422
19423 .option pipe_transport redirect string&!! unset
19424 .vindex "&$address_pipe$&"
19425 A &(redirect)& router sets up a direct delivery to a pipe when a string
19426 starting with a vertical bar character is specified as a new &"address"&. The
19427 transport used is specified by this option, which, after expansion, must be the
19428 name of a configured transport. This should normally be a &(pipe)& transport.
19429 When the transport is run, the pipe command is in &$address_pipe$&.
19430
19431
19432 .option qualify_domain redirect string&!! unset
19433 .vindex "&$qualify_recipient$&"
19434 If this option is set, and an unqualified address (one without a domain) is
19435 generated, and that address would normally be qualified by the global setting
19436 in &%qualify_recipient%&, it is instead qualified with the domain specified by
19437 expanding this string. If the expansion fails, the router declines. If you want
19438 to revert to the default, you can have the expansion generate
19439 &$qualify_recipient$&.
19440
19441 This option applies to all unqualified addresses generated by Exim filters,
19442 but for traditional &_.forward_& files, it applies only to addresses that are
19443 not preceded by a backslash. Sieve filters cannot generate unqualified
19444 addresses.
19445
19446 .option qualify_preserve_domain redirect boolean false
19447 .cindex "domain" "in redirection; preserving"
19448 .cindex "preserving domain in redirection"
19449 .cindex "address redirection" "domain; preserving"
19450 If this option is set, the router's local &%qualify_domain%& option must not be
19451 set (a configuration error occurs if it is). If an unqualified address (one
19452 without a domain) is generated, it is qualified with the domain of the parent
19453 address (the immediately preceding ancestor) instead of the global
19454 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
19455 this applies whether or not the address is preceded by a backslash.
19456
19457
19458 .option repeat_use redirect boolean true
19459 If this option is set false, the router is skipped for a child address that has
19460 any ancestor that was routed by this router. This test happens before any of
19461 the other preconditions are tested. Exim's default anti-looping rules skip
19462 only when the ancestor is the same as the current address. See also
19463 &%check_ancestor%& above and the generic &%redirect_router%& option.
19464
19465
19466 .option reply_transport redirect string&!! unset
19467 A &(redirect)& router sets up an automatic reply when a &%mail%& or
19468 &%vacation%& command is used in a filter file. The transport used is specified
19469 by this option, which, after expansion, must be the name of a configured
19470 transport. This should normally be an &(autoreply)& transport. Other transports
19471 are unlikely to do anything sensible or useful.
19472
19473
19474 .option rewrite redirect boolean true
19475 .cindex "address redirection" "disabling rewriting"
19476 If this option is set false, addresses generated by the router are not
19477 subject to address rewriting. Otherwise, they are treated like new addresses
19478 and are rewritten according to the global rewriting rules.
19479
19480
19481 .option sieve_subaddress redirect string&!! unset
19482 The value of this option is passed to a Sieve filter to specify the
19483 :subaddress part of an address.
19484
19485 .option sieve_useraddress redirect string&!! unset
19486 The value of this option is passed to a Sieve filter to specify the :user part
19487 of an address. However, if it is unset, the entire original local part
19488 (including any prefix or suffix) is used for :user.
19489
19490
19491 .option sieve_vacation_directory redirect string&!! unset
19492 .cindex "Sieve filter" "vacation directory"
19493 To enable the &"vacation"& extension for Sieve filters, you must set
19494 &%sieve_vacation_directory%& to the directory where vacation databases are held
19495 (do not put anything else in that directory), and ensure that the
19496 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
19497 needs their own directory; Exim will create it if necessary.
19498
19499
19500
19501 .option skip_syntax_errors redirect boolean false
19502 .cindex "forward file" "broken"
19503 .cindex "address redirection" "broken files"
19504 .cindex "alias file" "broken"
19505 .cindex "broken alias or forward files"
19506 .cindex "ignoring faulty addresses"
19507 .cindex "skipping faulty addresses"
19508 .cindex "error" "skipping bad syntax"
19509 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
19510 non-filter redirection data are skipped, and each failing address is logged. If
19511 &%syntax_errors_to%& is set, a message is sent to the address it defines,
19512 giving details of the failures. If &%syntax_errors_text%& is set, its contents
19513 are expanded and placed at the head of the error message generated by
19514 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
19515 be the same address as the generic &%errors_to%& option. The
19516 &%skip_syntax_errors%& option is often used when handling mailing lists.
19517
19518 If all the addresses in a redirection list are skipped because of syntax
19519 errors, the router declines to handle the original address, and it is passed to
19520 the following routers.
19521
19522 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
19523 error in the filter causes filtering to be abandoned without any action being
19524 taken. The incident is logged, and the router declines to handle the address,
19525 so it is passed to the following routers.
19526
19527 .cindex "Sieve filter" "syntax errors in"
19528 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
19529 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
19530 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
19531
19532 &%skip_syntax_errors%& can be used to specify that errors in users' forward
19533 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
19534 option, used with an address that does not get redirected, can be used to
19535 notify users of these errors, by means of a router like this:
19536 .code
19537 userforward:
19538 driver = redirect
19539 allow_filter
19540 check_local_user
19541 file = $home/.forward
19542 file_transport = address_file
19543 pipe_transport = address_pipe
19544 reply_transport = address_reply
19545 no_verify
19546 skip_syntax_errors
19547 syntax_errors_to = real-$local_part@$domain
19548 syntax_errors_text = \
19549 This is an automatically generated message. An error has\n\
19550 been found in your .forward file. Details of the error are\n\
19551 reported below. While this error persists, you will receive\n\
19552 a copy of this message for every message that is addressed\n\
19553 to you. If your .forward file is a filter file, or if it is\n\
19554 a non-filter file containing no valid forwarding addresses,\n\
19555 a copy of each incoming message will be put in your normal\n\
19556 mailbox. If a non-filter file contains at least one valid\n\
19557 forwarding address, forwarding to the valid addresses will\n\
19558 happen, and those will be the only deliveries that occur.
19559 .endd
19560 You also need a router to ensure that local addresses that are prefixed by
19561 &`real-`& are recognized, but not forwarded or filtered. For example, you could
19562 put this immediately before the &(userforward)& router:
19563 .code
19564 real_localuser:
19565 driver = accept
19566 check_local_user
19567 local_part_prefix = real-
19568 transport = local_delivery
19569 .endd
19570 For security, it would probably be a good idea to restrict the use of this
19571 router to locally-generated messages, using a condition such as this:
19572 .code
19573 condition = ${if match {$sender_host_address}\
19574 {\N^(|127\.0\.0\.1)$\N}}
19575 .endd
19576
19577
19578 .option syntax_errors_text redirect string&!! unset
19579 See &%skip_syntax_errors%& above.
19580
19581
19582 .option syntax_errors_to redirect string unset
19583 See &%skip_syntax_errors%& above.
19584 .ecindex IIDredrou1
19585 .ecindex IIDredrou2
19586
19587
19588
19589
19590
19591
19592 . ////////////////////////////////////////////////////////////////////////////
19593 . ////////////////////////////////////////////////////////////////////////////
19594
19595 .chapter "Environment for running local transports" "CHAPenvironment" &&&
19596 "Environment for local transports"
19597 .scindex IIDenvlotra1 "local transports" "environment for"
19598 .scindex IIDenvlotra2 "environment for local transports"
19599 .scindex IIDenvlotra3 "transport" "local; environment for"
19600 Local transports handle deliveries to files and pipes. (The &(autoreply)&
19601 transport can be thought of as similar to a pipe.) Exim always runs transports
19602 in subprocesses, under specified uids and gids. Typical deliveries to local
19603 mailboxes run under the uid and gid of the local user.
19604
19605 Exim also sets a specific current directory while running the transport; for
19606 some transports a home directory setting is also relevant. The &(pipe)&
19607 transport is the only one that sets up environment variables; see section
19608 &<<SECTpipeenv>>& for details.
19609
19610 The values used for the uid, gid, and the directories may come from several
19611 different places. In many cases, the router that handles the address associates
19612 settings with that address as a result of its &%check_local_user%&, &%group%&,
19613 or &%user%& options. However, values may also be given in the transport's own
19614 configuration, and these override anything that comes from the router.
19615
19616
19617
19618 .section "Concurrent deliveries" "SECID131"
19619 .cindex "concurrent deliveries"
19620 .cindex "simultaneous deliveries"
19621 If two different messages for the same local recipient arrive more or less
19622 simultaneously, the two delivery processes are likely to run concurrently. When
19623 the &(appendfile)& transport is used to write to a file, Exim applies locking
19624 rules to stop concurrent processes from writing to the same file at the same
19625 time.
19626
19627 However, when you use a &(pipe)& transport, it is up to you to arrange any
19628 locking that is needed. Here is a silly example:
19629 .code
19630 my_transport:
19631 driver = pipe
19632 command = /bin/sh -c 'cat >>/some/file'
19633 .endd
19634 This is supposed to write the message at the end of the file. However, if two
19635 messages arrive at the same time, the file will be scrambled. You can use the
19636 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
19637 file using the same algorithm that Exim itself uses.
19638
19639
19640
19641
19642 .section "Uids and gids" "SECTenvuidgid"
19643 .cindex "local transports" "uid and gid"
19644 .cindex "transport" "local; uid and gid"
19645 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
19646 overrides any group that the router set in the address, even if &%user%& is not
19647 set for the transport. This makes it possible, for example, to run local mail
19648 delivery under the uid of the recipient (set by the router), but in a special
19649 group (set by the transport). For example:
19650 .code
19651 # Routers ...
19652 # User/group are set by check_local_user in this router
19653 local_users:
19654 driver = accept
19655 check_local_user
19656 transport = group_delivery
19657
19658 # Transports ...
19659 # This transport overrides the group
19660 group_delivery:
19661 driver = appendfile
19662 file = /var/spool/mail/$local_part
19663 group = mail
19664 .endd
19665 If &%user%& is set for a transport, its value overrides what is set in the
19666 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
19667 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
19668 set.
19669
19670 .oindex "&%initgroups%&"
19671 When the uid is taken from the transport's configuration, the &[initgroups()]&
19672 function is called for the groups associated with that uid if the
19673 &%initgroups%& option is set for the transport. When the uid is not specified
19674 by the transport, but is associated with the address by a router, the option
19675 for calling &[initgroups()]& is taken from the router configuration.
19676
19677 .cindex "&(pipe)& transport" "uid for"
19678 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
19679 is set and &%user%& is not set, the uid of the process that called Exim to
19680 receive the message is used, and if &%group%& is not set, the corresponding
19681 original gid is also used.
19682
19683 This is the detailed preference order for obtaining a gid; the first of the
19684 following that is set is used:
19685
19686 .ilist
19687 A &%group%& setting of the transport;
19688 .next
19689 A &%group%& setting of the router;
19690 .next
19691 A gid associated with a user setting of the router, either as a result of
19692 &%check_local_user%& or an explicit non-numeric &%user%& setting;
19693 .next
19694 The group associated with a non-numeric &%user%& setting of the transport;
19695 .next
19696 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
19697 the uid is the creator's uid;
19698 .next
19699 The Exim gid if the Exim uid is being used as a default.
19700 .endlist
19701
19702 If, for example, the user is specified numerically on the router and there are
19703 no group settings, no gid is available. In this situation, an error occurs.
19704 This is different for the uid, for which there always is an ultimate default.
19705 The first of the following that is set is used:
19706
19707 .ilist
19708 A &%user%& setting of the transport;
19709 .next
19710 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
19711 .next
19712 A &%user%& setting of the router;
19713 .next
19714 A &%check_local_user%& setting of the router;
19715 .next
19716 The Exim uid.
19717 .endlist
19718
19719 Of course, an error will still occur if the uid that is chosen is on the
19720 &%never_users%& list.
19721
19722
19723
19724
19725
19726 .section "Current and home directories" "SECID132"
19727 .cindex "current directory for local transport"
19728 .cindex "home directory" "for local transport"
19729 .cindex "transport" "local; home directory for"
19730 .cindex "transport" "local; current directory for"
19731 Routers may set current and home directories for local transports by means of
19732 the &%transport_current_directory%& and &%transport_home_directory%& options.
19733 However, if the transport's &%current_directory%& or &%home_directory%& options
19734 are set, they override the router's values. In detail, the home directory
19735 for a local transport is taken from the first of these values that is set:
19736
19737 .ilist
19738 The &%home_directory%& option on the transport;
19739 .next
19740 The &%transport_home_directory%& option on the router;
19741 .next
19742 The password data if &%check_local_user%& is set on the router;
19743 .next
19744 The &%router_home_directory%& option on the router.
19745 .endlist
19746
19747 The current directory is taken from the first of these values that is set:
19748
19749 .ilist
19750 The &%current_directory%& option on the transport;
19751 .next
19752 The &%transport_current_directory%& option on the router.
19753 .endlist
19754
19755
19756 If neither the router nor the transport sets a current directory, Exim uses the
19757 value of the home directory, if it is set. Otherwise it sets the current
19758 directory to &_/_& before running a local transport.
19759
19760
19761
19762 .section "Expansion variables derived from the address" "SECID133"
19763 .vindex "&$domain$&"
19764 .vindex "&$local_part$&"
19765 .vindex "&$original_domain$&"
19766 Normally a local delivery is handling a single address, and in that case the
19767 variables such as &$domain$& and &$local_part$& are set during local
19768 deliveries. However, in some circumstances more than one address may be handled
19769 at once (for example, while writing batch SMTP for onward transmission by some
19770 other means). In this case, the variables associated with the local part are
19771 never set, &$domain$& is set only if all the addresses have the same domain,
19772 and &$original_domain$& is never set.
19773 .ecindex IIDenvlotra1
19774 .ecindex IIDenvlotra2
19775 .ecindex IIDenvlotra3
19776
19777
19778
19779
19780
19781
19782
19783 . ////////////////////////////////////////////////////////////////////////////
19784 . ////////////////////////////////////////////////////////////////////////////
19785
19786 .chapter "Generic options for transports" "CHAPtransportgeneric"
19787 .scindex IIDgenoptra1 "generic options" "transport"
19788 .scindex IIDgenoptra2 "options" "generic; for transports"
19789 .scindex IIDgenoptra3 "transport" "generic options for"
19790 The following generic options apply to all transports:
19791
19792
19793 .option body_only transports boolean false
19794 .cindex "transport" "body only"
19795 .cindex "message" "transporting body only"
19796 .cindex "body of message" "transporting"
19797 If this option is set, the message's headers are not transported. It is
19798 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
19799 or &(pipe)& transports, the settings of &%message_prefix%& and
19800 &%message_suffix%& should be checked, because this option does not
19801 automatically suppress them.
19802
19803
19804 .option current_directory transports string&!! unset
19805 .cindex "transport" "current directory for"
19806 This specifies the current directory that is to be set while running the
19807 transport, overriding any value that may have been set by the router.
19808 If the expansion fails for any reason, including forced failure, an error is
19809 logged, and delivery is deferred.
19810
19811
19812 .option disable_logging transports boolean false
19813 If this option is set true, nothing is logged for any
19814 deliveries by the transport or for any
19815 transport errors. You should not set this option unless you really, really know
19816 what you are doing.
19817
19818
19819 .option debug_print transports string&!! unset
19820 .cindex "testing" "variables in drivers"
19821 If this option is set and debugging is enabled (see the &%-d%& command line
19822 option), the string is expanded and included in the debugging output when the
19823 transport is run.
19824 If expansion of the string fails, the error message is written to the debugging
19825 output, and Exim carries on processing.
19826 This facility is provided to help with checking out the values of variables and
19827 so on when debugging driver configurations. For example, if a &%headers_add%&
19828 option is not working properly, &%debug_print%& could be used to output the
19829 variables it references. A newline is added to the text if it does not end with
19830 one.
19831 The variables &$transport_name$& and &$router_name$& contain the name of the
19832 transport and the router that called it.
19833
19834 .option delivery_date_add transports boolean false
19835 .cindex "&'Delivery-date:'& header line"
19836 If this option is true, a &'Delivery-date:'& header is added to the message.
19837 This gives the actual time the delivery was made. As this is not a standard
19838 header, Exim has a configuration option (&%delivery_date_remove%&) which
19839 requests its removal from incoming messages, so that delivered messages can
19840 safely be resent to other recipients.
19841
19842
19843 .option driver transports string unset
19844 This specifies which of the available transport drivers is to be used.
19845 There is no default, and this option must be set for every transport.
19846
19847
19848 .option envelope_to_add transports boolean false
19849 .cindex "&'Envelope-to:'& header line"
19850 If this option is true, an &'Envelope-to:'& header is added to the message.
19851 This gives the original address(es) in the incoming envelope that caused this
19852 delivery to happen. More than one address may be present if the transport is
19853 configured to handle several addresses at once, or if more than one original
19854 address was redirected to the same final address. As this is not a standard
19855 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
19856 its removal from incoming messages, so that delivered messages can safely be
19857 resent to other recipients.
19858
19859
19860 .option group transports string&!! "Exim group"
19861 .cindex "transport" "group; specifying"
19862 This option specifies a gid for running the transport process, overriding any
19863 value that the router supplies, and also overriding any value associated with
19864 &%user%& (see below).
19865
19866
19867 .option headers_add transports list&!! unset
19868 .cindex "header lines" "adding in transport"
19869 .cindex "transport" "header lines; adding"
19870 This option specifies a list of text headers, newline-separated,
19871 which are (separately) expanded and added to the header
19872 portion of a message as it is transported, as described in section
19873 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
19874 routers. If the result of the expansion is an empty string, or if the expansion
19875 is forced to fail, no action is taken. Other expansion failures are treated as
19876 errors and cause the delivery to be deferred.
19877
19878 Unlike most options, &%headers_add%& can be specified multiple times
19879 for a transport; all listed headers are added.
19880
19881
19882 .option headers_only transports boolean false
19883 .cindex "transport" "header lines only"
19884 .cindex "message" "transporting headers only"
19885 .cindex "header lines" "transporting"
19886 If this option is set, the message's body is not transported. It is mutually
19887 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
19888 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
19889 checked, since this option does not automatically suppress them.
19890
19891
19892 .option headers_remove transports list&!! unset
19893 .cindex "header lines" "removing"
19894 .cindex "transport" "header lines; removing"
19895 This option specifies a list of header names, colon-separated;
19896 these headers are omitted from the message as it is transported, as described
19897 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
19898 routers.
19899 Each list item is separately expanded.
19900 If the result of the expansion is an empty string, or if the expansion
19901 is forced to fail, no action is taken. Other expansion failures are treated as
19902 errors and cause the delivery to be deferred.
19903
19904 Unlike most options, &%headers_remove%& can be specified multiple times
19905 for a router; all listed headers are removed.
19906
19907
19908
19909 .option headers_rewrite transports string unset
19910 .cindex "transport" "header lines; rewriting"
19911 .cindex "rewriting" "at transport time"
19912 This option allows addresses in header lines to be rewritten at transport time,
19913 that is, as the message is being copied to its destination. The contents of the
19914 option are a colon-separated list of rewriting rules. Each rule is in exactly
19915 the same form as one of the general rewriting rules that are applied when a
19916 message is received. These are described in chapter &<<CHAPrewrite>>&. For
19917 example,
19918 .code
19919 headers_rewrite = a@b c@d f : \
19920 x@y w@z
19921 .endd
19922 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
19923 &'w@z'& in all address-bearing header lines. The rules are applied to the
19924 header lines just before they are written out at transport time, so they affect
19925 only those copies of the message that pass through the transport. However, only
19926 the message's original header lines, and any that were added by a system
19927 filter, are rewritten. If a router or transport adds header lines, they are not
19928 affected by this option. These rewriting rules are &'not'& applied to the
19929 envelope. You can change the return path using &%return_path%&, but you cannot
19930 change envelope recipients at this time.
19931
19932
19933 .option home_directory transports string&!! unset
19934 .cindex "transport" "home directory for"
19935 .vindex "&$home$&"
19936 This option specifies a home directory setting for a local transport,
19937 overriding any value that may be set by the router. The home directory is
19938 placed in &$home$& while expanding the transport's private options. It is also
19939 used as the current directory if no current directory is set by the
19940 &%current_directory%& option on the transport or the
19941 &%transport_current_directory%& option on the router. If the expansion fails
19942 for any reason, including forced failure, an error is logged, and delivery is
19943 deferred.
19944
19945
19946 .option initgroups transports boolean false
19947 .cindex "additional groups"
19948 .cindex "groups" "additional"
19949 .cindex "transport" "group; additional"
19950 If this option is true and the uid for the delivery process is provided by the
19951 transport, the &[initgroups()]& function is called when running the transport
19952 to ensure that any additional groups associated with the uid are set up.
19953
19954
19955 .option message_size_limit transports string&!! 0
19956 .cindex "limit" "message size per transport"
19957 .cindex "size" "of message, limit"
19958 .cindex "transport" "message size; limiting"
19959 This option controls the size of messages passed through the transport. It is
19960 expanded before use; the result of the expansion must be a sequence of decimal
19961 digits, optionally followed by K or M. If the expansion fails for any reason,
19962 including forced failure, or if the result is not of the required form,
19963 delivery is deferred. If the value is greater than zero and the size of a
19964 message exceeds this limit, the address is failed. If there is any chance that
19965 the resulting bounce message could be routed to the same transport, you should
19966 ensure that &%return_size_limit%& is less than the transport's
19967 &%message_size_limit%&, as otherwise the bounce message will fail to get
19968 delivered.
19969
19970
19971
19972 .option rcpt_include_affixes transports boolean false
19973 .cindex "prefix" "for local part, including in envelope"
19974 .cindex "suffix for local part" "including in envelope"
19975 .cindex "local part" "prefix"
19976 .cindex "local part" "suffix"
19977 When this option is false (the default), and an address that has had any
19978 affixes (prefixes or suffixes) removed from the local part is delivered by any
19979 form of SMTP or LMTP, the affixes are not included. For example, if a router
19980 that contains
19981 .code
19982 local_part_prefix = *-
19983 .endd
19984 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
19985 is delivered with
19986 .code
19987 RCPT TO:<xyz@some.domain>
19988 .endd
19989 This is also the case when an ACL-time callout is being used to verify a
19990 recipient address. However, if &%rcpt_include_affixes%& is set true, the
19991 whole local part is included in the RCPT command. This option applies to BSMTP
19992 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
19993 &(lmtp)& and &(smtp)& transports.
19994
19995
19996 .option retry_use_local_part transports boolean "see below"
19997 .cindex "hints database" "retry keys"
19998 When a delivery suffers a temporary failure, a retry record is created
19999 in Exim's hints database. For remote deliveries, the key for the retry record
20000 is based on the name and/or IP address of the failing remote host. For local
20001 deliveries, the key is normally the entire address, including both the local
20002 part and the domain. This is suitable for most common cases of local delivery
20003 temporary failure &-- for example, exceeding a mailbox quota should delay only
20004 deliveries to that mailbox, not to the whole domain.
20005
20006 However, in some special cases you may want to treat a temporary local delivery
20007 as a failure associated with the domain, and not with a particular local part.
20008 (For example, if you are storing all mail for some domain in files.) You can do
20009 this by setting &%retry_use_local_part%& false.
20010
20011 For all the local transports, its default value is true. For remote transports,
20012 the default value is false for tidiness, but changing the value has no effect
20013 on a remote transport in the current implementation.
20014
20015
20016 .option return_path transports string&!! unset
20017 .cindex "envelope sender"
20018 .cindex "transport" "return path; changing"
20019 .cindex "return path" "changing in transport"
20020 If this option is set, the string is expanded at transport time and replaces
20021 the existing return path (envelope sender) value in the copy of the message
20022 that is being delivered. An empty return path is permitted. This feature is
20023 designed for remote deliveries, where the value of this option is used in the
20024 SMTP MAIL command. If you set &%return_path%& for a local transport, the
20025 only effect is to change the address that is placed in the &'Return-path:'&
20026 header line, if one is added to the message (see the next option).
20027
20028 &*Note:*& A changed return path is not logged unless you add
20029 &%return_path_on_delivery%& to the log selector.
20030
20031 .vindex "&$return_path$&"
20032 The expansion can refer to the existing value via &$return_path$&. This is
20033 either the message's envelope sender, or an address set by the
20034 &%errors_to%& option on a router. If the expansion is forced to fail, no
20035 replacement occurs; if it fails for another reason, delivery is deferred. This
20036 option can be used to support VERP (Variable Envelope Return Paths) &-- see
20037 section &<<SECTverp>>&.
20038
20039 &*Note*&: If a delivery error is detected locally, including the case when a
20040 remote server rejects a message at SMTP time, the bounce message is not sent to
20041 the value of this option. It is sent to the previously set errors address.
20042 This defaults to the incoming sender address, but can be changed by setting
20043 &%errors_to%& in a router.
20044
20045
20046
20047 .option return_path_add transports boolean false
20048 .cindex "&'Return-path:'& header line"
20049 If this option is true, a &'Return-path:'& header is added to the message.
20050 Although the return path is normally available in the prefix line of BSD
20051 mailboxes, this is commonly not displayed by MUAs, and so the user does not
20052 have easy access to it.
20053
20054 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
20055 the delivery SMTP server makes the final delivery"&. This implies that this
20056 header should not be present in incoming messages. Exim has a configuration
20057 option, &%return_path_remove%&, which requests removal of this header from
20058 incoming messages, so that delivered messages can safely be resent to other
20059 recipients.
20060
20061
20062 .option shadow_condition transports string&!! unset
20063 See &%shadow_transport%& below.
20064
20065
20066 .option shadow_transport transports string unset
20067 .cindex "shadow transport"
20068 .cindex "transport" "shadow"
20069 A local transport may set the &%shadow_transport%& option to the name of
20070 another local transport. Shadow remote transports are not supported.
20071
20072 Whenever a delivery to the main transport succeeds, and either
20073 &%shadow_condition%& is unset, or its expansion does not result in the empty
20074 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
20075 passed to the shadow transport, with the same delivery address or addresses. If
20076 expansion fails, no action is taken except that non-forced expansion failures
20077 cause a log line to be written.
20078
20079 The result of the shadow transport is discarded and does not affect the
20080 subsequent processing of the message. Only a single level of shadowing is
20081 provided; the &%shadow_transport%& option is ignored on any transport when it
20082 is running as a shadow. Options concerned with output from pipes are also
20083 ignored. The log line for the successful delivery has an item added on the end,
20084 of the form
20085 .code
20086 ST=<shadow transport name>
20087 .endd
20088 If the shadow transport did not succeed, the error message is put in
20089 parentheses afterwards. Shadow transports can be used for a number of different
20090 purposes, including keeping more detailed log information than Exim normally
20091 provides, and implementing automatic acknowledgment policies based on message
20092 headers that some sites insist on.
20093
20094
20095 .option transport_filter transports string&!! unset
20096 .cindex "transport" "filter"
20097 .cindex "filter" "transport filter"
20098 This option sets up a filtering (in the Unix shell sense) process for messages
20099 at transport time. It should not be confused with mail filtering as set up by
20100 individual users or via a system filter.
20101
20102 When the message is about to be written out, the command specified by
20103 &%transport_filter%& is started up in a separate, parallel process, and
20104 the entire message, including the header lines, is passed to it on its standard
20105 input (this in fact is done from a third process, to avoid deadlock). The
20106 command must be specified as an absolute path.
20107
20108 The lines of the message that are written to the transport filter are
20109 terminated by newline (&"\n"&). The message is passed to the filter before any
20110 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
20111 lines beginning with a dot, and also before any processing implied by the
20112 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
20113 &(pipe)& transports.
20114
20115 The standard error for the filter process is set to the same destination as its
20116 standard output; this is read and written to the message's ultimate
20117 destination. The process that writes the message to the filter, the
20118 filter itself, and the original process that reads the result and delivers it
20119 are all run in parallel, like a shell pipeline.
20120
20121 The filter can perform any transformations it likes, but of course should take
20122 care not to break RFC 2822 syntax. Exim does not check the result, except to
20123 test for a final newline when SMTP is in use. All messages transmitted over
20124 SMTP must end with a newline, so Exim supplies one if it is missing.
20125
20126 .cindex "content scanning" "per user"
20127 A transport filter can be used to provide content-scanning on a per-user basis
20128 at delivery time if the only required effect of the scan is to modify the
20129 message. For example, a content scan could insert a new header line containing
20130 a spam score. This could be interpreted by a filter in the user's MUA. It is
20131 not possible to discard a message at this stage.
20132
20133 .cindex "SMTP" "SIZE"
20134 A problem might arise if the filter increases the size of a message that is
20135 being sent down an SMTP connection. If the receiving SMTP server has indicated
20136 support for the SIZE parameter, Exim will have sent the size of the message
20137 at the start of the SMTP session. If what is actually sent is substantially
20138 more, the server might reject the message. This can be worked round by setting
20139 the &%size_addition%& option on the &(smtp)& transport, either to allow for
20140 additions to the message, or to disable the use of SIZE altogether.
20141
20142 .vindex "&$pipe_addresses$&"
20143 The value of the &%transport_filter%& option is the command string for starting
20144 the filter, which is run directly from Exim, not under a shell. The string is
20145 parsed by Exim in the same way as a command string for the &(pipe)& transport:
20146 Exim breaks it up into arguments and then expands each argument separately (see
20147 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
20148 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
20149 of arguments, one for each address that applies to this delivery. (This isn't
20150 an ideal name for this feature here, but as it was already implemented for the
20151 &(pipe)& transport, it seemed sensible not to change it.)
20152
20153 .vindex "&$host$&"
20154 .vindex "&$host_address$&"
20155 The expansion variables &$host$& and &$host_address$& are available when the
20156 transport is a remote one. They contain the name and IP address of the host to
20157 which the message is being sent. For example:
20158 .code
20159 transport_filter = /some/directory/transport-filter.pl \
20160 $host $host_address $sender_address $pipe_addresses
20161 .endd
20162
20163 Two problems arise if you want to use more complicated expansion items to
20164 generate transport filter commands, both of which due to the fact that the
20165 command is split up &'before'& expansion.
20166 .ilist
20167 If an expansion item contains white space, you must quote it, so that it is all
20168 part of the same command item. If the entire option setting is one such
20169 expansion item, you have to take care what kind of quoting you use. For
20170 example:
20171 .code
20172 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
20173 .endd
20174 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
20175 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
20176 stripped by Exim when it read the option's value. When the value is used, if
20177 the single quotes were missing, the line would be split into two items,
20178 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
20179 Exim tried to expand the first one.
20180 .next
20181 Except for the special case of &$pipe_addresses$& that is mentioned above, an
20182 expansion cannot generate multiple arguments, or a command name followed by
20183 arguments. Consider this example:
20184 .code
20185 transport_filter = ${lookup{$host}lsearch{/a/file}\
20186 {$value}{/bin/cat}}
20187 .endd
20188 The result of the lookup is interpreted as the name of the command, even
20189 if it contains white space. The simplest way round this is to use a shell:
20190 .code
20191 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
20192 {$value}{/bin/cat}}
20193 .endd
20194 .endlist
20195
20196 The filter process is run under the same uid and gid as the normal delivery.
20197 For remote deliveries this is the Exim uid/gid by default. The command should
20198 normally yield a zero return code. Transport filters are not supposed to fail.
20199 A non-zero code is taken to mean that the transport filter encountered some
20200 serious problem. Delivery of the message is deferred; the message remains on
20201 the queue and is tried again later. It is not possible to cause a message to be
20202 bounced from a transport filter.
20203
20204 If a transport filter is set on an autoreply transport, the original message is
20205 passed through the filter as it is being copied into the newly generated
20206 message, which happens if the &%return_message%& option is set.
20207
20208
20209 .option transport_filter_timeout transports time 5m
20210 .cindex "transport" "filter, timeout"
20211 When Exim is reading the output of a transport filter, it applies a timeout
20212 that can be set by this option. Exceeding the timeout is normally treated as a
20213 temporary delivery failure. However, if a transport filter is used with a
20214 &(pipe)& transport, a timeout in the transport filter is treated in the same
20215 way as a timeout in the pipe command itself. By default, a timeout is a hard
20216 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
20217 becomes a temporary error.
20218
20219
20220 .option user transports string&!! "Exim user"
20221 .cindex "uid (user id)" "local delivery"
20222 .cindex "transport" "user, specifying"
20223 This option specifies the user under whose uid the delivery process is to be
20224 run, overriding any uid that may have been set by the router. If the user is
20225 given as a name, the uid is looked up from the password data, and the
20226 associated group is taken as the value of the gid to be used if the &%group%&
20227 option is not set.
20228
20229 For deliveries that use local transports, a user and group are normally
20230 specified explicitly or implicitly (for example, as a result of
20231 &%check_local_user%&) by the router or transport.
20232
20233 .cindex "hints database" "access by remote transport"
20234 For remote transports, you should leave this option unset unless you really are
20235 sure you know what you are doing. When a remote transport is running, it needs
20236 to be able to access Exim's hints databases, because each host may have its own
20237 retry data.
20238 .ecindex IIDgenoptra1
20239 .ecindex IIDgenoptra2
20240 .ecindex IIDgenoptra3
20241
20242
20243
20244
20245
20246
20247 . ////////////////////////////////////////////////////////////////////////////
20248 . ////////////////////////////////////////////////////////////////////////////
20249
20250 .chapter "Address batching in local transports" "CHAPbatching" &&&
20251 "Address batching"
20252 .cindex "transport" "local; address batching in"
20253 The only remote transport (&(smtp)&) is normally configured to handle more than
20254 one address at a time, so that when several addresses are routed to the same
20255 remote host, just one copy of the message is sent. Local transports, however,
20256 normally handle one address at a time. That is, a separate instance of the
20257 transport is run for each address that is routed to the transport. A separate
20258 copy of the message is delivered each time.
20259
20260 .cindex "batched local delivery"
20261 .oindex "&%batch_max%&"
20262 .oindex "&%batch_id%&"
20263 In special cases, it may be desirable to handle several addresses at once in a
20264 local transport, for example:
20265
20266 .ilist
20267 In an &(appendfile)& transport, when storing messages in files for later
20268 delivery by some other means, a single copy of the message with multiple
20269 recipients saves space.
20270 .next
20271 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
20272 a single copy saves time, and is the normal way LMTP is expected to work.
20273 .next
20274 In a &(pipe)& transport, when passing the message
20275 to a scanner program or
20276 to some other delivery mechanism such as UUCP, multiple recipients may be
20277 acceptable.
20278 .endlist
20279
20280 These three local transports all have the same options for controlling multiple
20281 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
20282 repeating the information for each transport, these options are described here.
20283
20284 The &%batch_max%& option specifies the maximum number of addresses that can be
20285 delivered together in a single run of the transport. Its default value is one
20286 (no batching). When more than one address is routed to a transport that has a
20287 &%batch_max%& value greater than one, the addresses are delivered in a batch
20288 (that is, in a single run of the transport with multiple recipients), subject
20289 to certain conditions:
20290
20291 .ilist
20292 .vindex "&$local_part$&"
20293 If any of the transport's options contain a reference to &$local_part$&, no
20294 batching is possible.
20295 .next
20296 .vindex "&$domain$&"
20297 If any of the transport's options contain a reference to &$domain$&, only
20298 addresses with the same domain are batched.
20299 .next
20300 .cindex "customizing" "batching condition"
20301 If &%batch_id%& is set, it is expanded for each address, and only those
20302 addresses with the same expanded value are batched. This allows you to specify
20303 customized batching conditions. Failure of the expansion for any reason,
20304 including forced failure, disables batching, but it does not stop the delivery
20305 from taking place.
20306 .next
20307 Batched addresses must also have the same errors address (where to send
20308 delivery errors), the same header additions and removals, the same user and
20309 group for the transport, and if a host list is present, the first host must
20310 be the same.
20311 .endlist
20312
20313 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
20314 both when the file or pipe command is specified in the transport, and when it
20315 is specified by a &(redirect)& router, but all the batched addresses must of
20316 course be routed to the same file or pipe command. These two transports have an
20317 option called &%use_bsmtp%&, which causes them to deliver the message in
20318 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
20319 &%check_string%& and &%escape_string%& options are forced to the values
20320 .code
20321 check_string = "."
20322 escape_string = ".."
20323 .endd
20324 when batched SMTP is in use. A full description of the batch SMTP mechanism is
20325 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
20326 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
20327
20328 .cindex "&'Envelope-to:'& header line"
20329 If the generic &%envelope_to_add%& option is set for a batching transport, the
20330 &'Envelope-to:'& header that is added to the message contains all the addresses
20331 that are being processed together. If you are using a batching &(appendfile)&
20332 transport without &%use_bsmtp%&, the only way to preserve the recipient
20333 addresses is to set the &%envelope_to_add%& option.
20334
20335 .cindex "&(pipe)& transport" "with multiple addresses"
20336 .vindex "&$pipe_addresses$&"
20337 If you are using a &(pipe)& transport without BSMTP, and setting the
20338 transport's &%command%& option, you can include &$pipe_addresses$& as part of
20339 the command. This is not a true variable; it is a bit of magic that causes each
20340 of the recipient addresses to be inserted into the command as a separate
20341 argument. This provides a way of accessing all the addresses that are being
20342 delivered in the batch. &*Note:*& This is not possible for pipe commands that
20343 are specified by a &(redirect)& router.
20344
20345
20346
20347
20348 . ////////////////////////////////////////////////////////////////////////////
20349 . ////////////////////////////////////////////////////////////////////////////
20350
20351 .chapter "The appendfile transport" "CHAPappendfile"
20352 .scindex IIDapptra1 "&(appendfile)& transport"
20353 .scindex IIDapptra2 "transports" "&(appendfile)&"
20354 .cindex "directory creation"
20355 .cindex "creating directories"
20356 The &(appendfile)& transport delivers a message by appending it to an existing
20357 file, or by creating an entirely new file in a specified directory. Single
20358 files to which messages are appended can be in the traditional Unix mailbox
20359 format, or optionally in the MBX format supported by the Pine MUA and
20360 University of Washington IMAP daemon, &'inter alia'&. When each message is
20361 being delivered as a separate file, &"maildir"& format can optionally be used
20362 to give added protection against failures that happen part-way through the
20363 delivery. A third form of separate-file delivery known as &"mailstore"& is also
20364 supported. For all file formats, Exim attempts to create as many levels of
20365 directory as necessary, provided that &%create_directory%& is set.
20366
20367 The code for the optional formats is not included in the Exim binary by
20368 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
20369 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
20370 included.
20371
20372 .cindex "quota" "system"
20373 Exim recognizes system quota errors, and generates an appropriate message. Exim
20374 also supports its own quota control within the transport, for use when the
20375 system facility is unavailable or cannot be used for some reason.
20376
20377 If there is an error while appending to a file (for example, quota exceeded or
20378 partition filled), Exim attempts to reset the file's length and last
20379 modification time back to what they were before. If there is an error while
20380 creating an entirely new file, the new file is removed.
20381
20382 Before appending to a file, a number of security checks are made, and the
20383 file is locked. A detailed description is given below, after the list of
20384 private options.
20385
20386 The &(appendfile)& transport is most commonly used for local deliveries to
20387 users' mailboxes. However, it can also be used as a pseudo-remote transport for
20388 putting messages into files for remote delivery by some means other than Exim.
20389 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
20390 option).
20391
20392
20393
20394 .section "The file and directory options" "SECTfildiropt"
20395 The &%file%& option specifies a single file, to which the message is appended;
20396 the &%directory%& option specifies a directory, in which a new file containing
20397 the message is created. Only one of these two options can be set, and for
20398 normal deliveries to mailboxes, one of them &'must'& be set.
20399
20400 .vindex "&$address_file$&"
20401 .vindex "&$local_part$&"
20402 However, &(appendfile)& is also used for delivering messages to files or
20403 directories whose names (or parts of names) are obtained from alias,
20404 forwarding, or filtering operations (for example, a &%save%& command in a
20405 user's Exim filter). When such a transport is running, &$local_part$& contains
20406 the local part that was aliased or forwarded, and &$address_file$& contains the
20407 name (or partial name) of the file or directory generated by the redirection
20408 operation. There are two cases:
20409
20410 .ilist
20411 If neither &%file%& nor &%directory%& is set, the redirection operation
20412 must specify an absolute path (one that begins with &`/`&). This is the most
20413 common case when users with local accounts use filtering to sort mail into
20414 different folders. See for example, the &(address_file)& transport in the
20415 default configuration. If the path ends with a slash, it is assumed to be the
20416 name of a directory. A delivery to a directory can also be forced by setting
20417 &%maildir_format%& or &%mailstore_format%&.
20418 .next
20419 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
20420 used to determine the file or directory name for the delivery. Normally, the
20421 contents of &$address_file$& are used in some way in the string expansion.
20422 .endlist
20423
20424
20425 .cindex "Sieve filter" "configuring &(appendfile)&"
20426 .cindex "Sieve filter" "relative mailbox path handling"
20427 As an example of the second case, consider an environment where users do not
20428 have home directories. They may be permitted to use Exim filter commands of the
20429 form:
20430 .code
20431 save folder23
20432 .endd
20433 or Sieve filter commands of the form:
20434 .code
20435 require "fileinto";
20436 fileinto "folder23";
20437 .endd
20438 In this situation, the expansion of &%file%& or &%directory%& in the transport
20439 must transform the relative path into an appropriate absolute file name. In the
20440 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
20441 is used as a result of a &"keep"& action in the filter. This example shows one
20442 way of handling this requirement:
20443 .code
20444 file = ${if eq{$address_file}{inbox} \
20445 {/var/mail/$local_part} \
20446 {${if eq{${substr_0_1:$address_file}}{/} \
20447 {$address_file} \
20448 {$home/mail/$address_file} \
20449 }} \
20450 }
20451 .endd
20452 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
20453 location, absolute paths are used without change, and other folders are in the
20454 &_mail_& directory within the home directory.
20455
20456 &*Note 1*&: While processing an Exim filter, a relative path such as
20457 &_folder23_& is turned into an absolute path if a home directory is known to
20458 the router. In particular, this is the case if &%check_local_user%& is set. If
20459 you want to prevent this happening at routing time, you can set
20460 &%router_home_directory%& empty. This forces the router to pass the relative
20461 path to the transport.
20462
20463 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
20464 the &%file%& or &%directory%& option is still used if it is set.
20465
20466
20467
20468
20469 .section "Private options for appendfile" "SECID134"
20470 .cindex "options" "&(appendfile)& transport"
20471
20472
20473
20474 .option allow_fifo appendfile boolean false
20475 .cindex "fifo (named pipe)"
20476 .cindex "named pipe (fifo)"
20477 .cindex "pipe" "named (fifo)"
20478 Setting this option permits delivery to named pipes (FIFOs) as well as to
20479 regular files. If no process is reading the named pipe at delivery time, the
20480 delivery is deferred.
20481
20482
20483 .option allow_symlink appendfile boolean false
20484 .cindex "symbolic link" "to mailbox"
20485 .cindex "mailbox" "symbolic link"
20486 By default, &(appendfile)& will not deliver if the path name for the file is
20487 that of a symbolic link. Setting this option relaxes that constraint, but there
20488 are security issues involved in the use of symbolic links. Be sure you know
20489 what you are doing if you set this. Details of exactly what this option affects
20490 are included in the discussion which follows this list of options.
20491
20492
20493 .option batch_id appendfile string&!! unset
20494 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
20495 However, batching is automatically disabled for &(appendfile)& deliveries that
20496 happen as a result of forwarding or aliasing or other redirection directly to a
20497 file.
20498
20499
20500 .option batch_max appendfile integer 1
20501 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
20502
20503
20504 .option check_group appendfile boolean false
20505 When this option is set, the group owner of the file defined by the &%file%&
20506 option is checked to see that it is the same as the group under which the
20507 delivery process is running. The default setting is false because the default
20508 file mode is 0600, which means that the group is irrelevant.
20509
20510
20511 .option check_owner appendfile boolean true
20512 When this option is set, the owner of the file defined by the &%file%& option
20513 is checked to ensure that it is the same as the user under which the delivery
20514 process is running.
20515
20516
20517 .option check_string appendfile string "see below"
20518 .cindex "&""From""& line"
20519 As &(appendfile)& writes the message, the start of each line is tested for
20520 matching &%check_string%&, and if it does, the initial matching characters are
20521 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
20522 a literal string, not a regular expression, and the case of any letters it
20523 contains is significant.
20524
20525 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
20526 are forced to &"."& and &".."& respectively, and any settings in the
20527 configuration are ignored. Otherwise, they default to &"From&~"& and
20528 &">From&~"& when the &%file%& option is set, and unset when any of the
20529 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
20530
20531 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
20532 suitable for traditional &"BSD"& mailboxes, where a line beginning with
20533 &"From&~"& indicates the start of a new message. All four options need changing
20534 if another format is used. For example, to deliver to mailboxes in MMDF format:
20535 .cindex "MMDF format mailbox"
20536 .cindex "mailbox" "MMDF format"
20537 .code
20538 check_string = "\1\1\1\1\n"
20539 escape_string = "\1\1\1\1 \n"
20540 message_prefix = "\1\1\1\1\n"
20541 message_suffix = "\1\1\1\1\n"
20542 .endd
20543 .option create_directory appendfile boolean true
20544 .cindex "directory creation"
20545 When this option is true, Exim attempts to create any missing superior
20546 directories for the file that it is about to write. A created directory's mode
20547 is given by the &%directory_mode%& option.
20548
20549 The group ownership of a newly created directory is highly dependent on the
20550 operating system (and possibly the file system) that is being used. For
20551 example, in Solaris, if the parent directory has the setgid bit set, its group
20552 is propagated to the child; if not, the currently set group is used. However,
20553 in FreeBSD, the parent's group is always used.
20554
20555
20556
20557 .option create_file appendfile string anywhere
20558 This option constrains the location of files and directories that are created
20559 by this transport. It applies to files defined by the &%file%& option and
20560 directories defined by the &%directory%& option. In the case of maildir
20561 delivery, it applies to the top level directory, not the maildir directories
20562 beneath.
20563
20564 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
20565 &"belowhome"&. In the second and third cases, a home directory must have been
20566 set for the transport. This option is not useful when an explicit file name is
20567 given for normal mailbox deliveries. It is intended for the case when file
20568 names are generated from users' &_.forward_& files. These are usually handled
20569 by an &(appendfile)& transport called &%address_file%&. See also
20570 &%file_must_exist%&.
20571
20572
20573 .option directory appendfile string&!! unset
20574 This option is mutually exclusive with the &%file%& option, but one of &%file%&
20575 or &%directory%& must be set, unless the delivery is the direct result of a
20576 redirection (see section &<<SECTfildiropt>>&).
20577
20578 When &%directory%& is set, the string is expanded, and the message is delivered
20579 into a new file or files in or below the given directory, instead of being
20580 appended to a single mailbox file. A number of different formats are provided
20581 (see &%maildir_format%& and &%mailstore_format%&), and see section
20582 &<<SECTopdir>>& for further details of this form of delivery.
20583
20584
20585 .option directory_file appendfile string&!! "see below"
20586 .cindex "base62"
20587 .vindex "&$inode$&"
20588 When &%directory%& is set, but neither &%maildir_format%& nor
20589 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
20590 whose name is obtained by expanding this string. The default value is:
20591 .code
20592 q${base62:$tod_epoch}-$inode
20593 .endd
20594 This generates a unique name from the current time, in base 62 form, and the
20595 inode of the file. The variable &$inode$& is available only when expanding this
20596 option.
20597
20598
20599 .option directory_mode appendfile "octal integer" 0700
20600 If &(appendfile)& creates any directories as a result of the
20601 &%create_directory%& option, their mode is specified by this option.
20602
20603
20604 .option escape_string appendfile string "see description"
20605 See &%check_string%& above.
20606
20607
20608 .option file appendfile string&!! unset
20609 This option is mutually exclusive with the &%directory%& option, but one of
20610 &%file%& or &%directory%& must be set, unless the delivery is the direct result
20611 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
20612 specifies a single file, to which the message is appended. One or more of
20613 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
20614 &%file%&.
20615
20616 .cindex "NFS" "lock file"
20617 .cindex "locking files"
20618 .cindex "lock files"
20619 If you are using more than one host to deliver over NFS into the same
20620 mailboxes, you should always use lock files.
20621
20622 The string value is expanded for each delivery, and must yield an absolute
20623 path. The most common settings of this option are variations on one of these
20624 examples:
20625 .code
20626 file = /var/spool/mail/$local_part
20627 file = /home/$local_part/inbox
20628 file = $home/inbox
20629 .endd
20630 .cindex "&""sticky""& bit"
20631 In the first example, all deliveries are done into the same directory. If Exim
20632 is configured to use lock files (see &%use_lockfile%& below) it must be able to
20633 create a file in the directory, so the &"sticky"& bit must be turned on for
20634 deliveries to be possible, or alternatively the &%group%& option can be used to
20635 run the delivery under a group id which has write access to the directory.
20636
20637
20638
20639 .option file_format appendfile string unset
20640 .cindex "file" "mailbox; checking existing format"
20641 This option requests the transport to check the format of an existing file
20642 before adding to it. The check consists of matching a specific string at the
20643 start of the file. The value of the option consists of an even number of
20644 colon-separated strings. The first of each pair is the test string, and the
20645 second is the name of a transport. If the transport associated with a matched
20646 string is not the current transport, control is passed over to the other
20647 transport. For example, suppose the standard &(local_delivery)& transport has
20648 this added to it:
20649 .code
20650 file_format = "From : local_delivery :\
20651 \1\1\1\1\n : local_mmdf_delivery"
20652 .endd
20653 Mailboxes that begin with &"From"& are still handled by this transport, but if
20654 a mailbox begins with four binary ones followed by a newline, control is passed
20655 to a transport called &%local_mmdf_delivery%&, which presumably is configured
20656 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
20657 is assumed to match the current transport. If the start of a mailbox doesn't
20658 match any string, or if the transport named for a given string is not defined,
20659 delivery is deferred.
20660
20661
20662 .option file_must_exist appendfile boolean false
20663 If this option is true, the file specified by the &%file%& option must exist.
20664 A temporary error occurs if it does not, causing delivery to be deferred.
20665 If this option is false, the file is created if it does not exist.
20666
20667
20668 .option lock_fcntl_timeout appendfile time 0s
20669 .cindex "timeout" "mailbox locking"
20670 .cindex "mailbox" "locking, blocking and non-blocking"
20671 .cindex "locking files"
20672 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
20673 when locking an open mailbox file. If the call fails, the delivery process
20674 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
20675 Non-blocking calls are used so that the file is not kept open during the wait
20676 for the lock; the reason for this is to make it as safe as possible for
20677 deliveries over NFS in the case when processes might be accessing an NFS
20678 mailbox without using a lock file. This should not be done, but
20679 misunderstandings and hence misconfigurations are not unknown.
20680
20681 On a busy system, however, the performance of a non-blocking lock approach is
20682 not as good as using a blocking lock with a timeout. In this case, the waiting
20683 is done inside the system call, and Exim's delivery process acquires the lock
20684 and can proceed as soon as the previous lock holder releases it.
20685
20686 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
20687 timeout, are used. There may still be some retrying: the maximum number of
20688 retries is
20689 .code
20690 (lock_retries * lock_interval) / lock_fcntl_timeout
20691 .endd
20692 rounded up to the next whole number. In other words, the total time during
20693 which &(appendfile)& is trying to get a lock is roughly the same, unless
20694 &%lock_fcntl_timeout%& is set very large.
20695
20696 You should consider setting this option if you are getting a lot of delayed
20697 local deliveries because of errors of the form
20698 .code
20699 failed to lock mailbox /some/file (fcntl)
20700 .endd
20701
20702 .option lock_flock_timeout appendfile time 0s
20703 This timeout applies to file locking when using &[flock()]& (see
20704 &%use_flock%&); the timeout operates in a similar manner to
20705 &%lock_fcntl_timeout%&.
20706
20707
20708 .option lock_interval appendfile time 3s
20709 This specifies the time to wait between attempts to lock the file. See below
20710 for details of locking.
20711
20712
20713 .option lock_retries appendfile integer 10
20714 This specifies the maximum number of attempts to lock the file. A value of zero
20715 is treated as 1. See below for details of locking.
20716
20717
20718 .option lockfile_mode appendfile "octal integer" 0600
20719 This specifies the mode of the created lock file, when a lock file is being
20720 used (see &%use_lockfile%& and &%use_mbx_lock%&).
20721
20722
20723 .option lockfile_timeout appendfile time 30m
20724 .cindex "timeout" "mailbox locking"
20725 When a lock file is being used (see &%use_lockfile%&), if a lock file already
20726 exists and is older than this value, it is assumed to have been left behind by
20727 accident, and Exim attempts to remove it.
20728
20729
20730 .option mailbox_filecount appendfile string&!! unset
20731 .cindex "mailbox" "specifying size of"
20732 .cindex "size" "of mailbox"
20733 If this option is set, it is expanded, and the result is taken as the current
20734 number of files in the mailbox. It must be a decimal number, optionally
20735 followed by K or M. This provides a way of obtaining this information from an
20736 external source that maintains the data.
20737
20738
20739 .option mailbox_size appendfile string&!! unset
20740 .cindex "mailbox" "specifying size of"
20741 .cindex "size" "of mailbox"
20742 If this option is set, it is expanded, and the result is taken as the current
20743 size the mailbox. It must be a decimal number, optionally followed by K or M.
20744 This provides a way of obtaining this information from an external source that
20745 maintains the data. This is likely to be helpful for maildir deliveries where
20746 it is computationally expensive to compute the size of a mailbox.
20747
20748
20749
20750 .option maildir_format appendfile boolean false
20751 .cindex "maildir format" "specifying"
20752 If this option is set with the &%directory%& option, the delivery is into a new
20753 file, in the &"maildir"& format that is used by other mail software. When the
20754 transport is activated directly from a &(redirect)& router (for example, the
20755 &(address_file)& transport in the default configuration), setting
20756 &%maildir_format%& causes the path received from the router to be treated as a
20757 directory, whether or not it ends with &`/`&. This option is available only if
20758 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
20759 &<<SECTmaildirdelivery>>& below for further details.
20760
20761
20762 .option maildir_quota_directory_regex appendfile string "See below"
20763 .cindex "maildir format" "quota; directories included in"
20764 .cindex "quota" "maildir; directories included in"
20765 This option is relevant only when &%maildir_use_size_file%& is set. It defines
20766 a regular expression for specifying directories, relative to the quota
20767 directory (see &%quota_directory%&), that should be included in the quota
20768 calculation. The default value is:
20769 .code
20770 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
20771 .endd
20772 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
20773 (directories whose names begin with a dot). If you want to exclude the
20774 &_Trash_&
20775 folder from the count (as some sites do), you need to change this setting to
20776 .code
20777 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
20778 .endd
20779 This uses a negative lookahead in the regular expression to exclude the
20780 directory whose name is &_.Trash_&. When a directory is excluded from quota
20781 calculations, quota processing is bypassed for any messages that are delivered
20782 directly into that directory.
20783
20784
20785 .option maildir_retries appendfile integer 10
20786 This option specifies the number of times to retry when writing a file in
20787 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
20788
20789
20790 .option maildir_tag appendfile string&!! unset
20791 This option applies only to deliveries in maildir format, and is described in
20792 section &<<SECTmaildirdelivery>>& below.
20793
20794
20795 .option maildir_use_size_file appendfile&!! boolean false
20796 .cindex "maildir format" "&_maildirsize_& file"
20797 The result of string expansion for this option must be a valid boolean value.
20798 If it is true, it enables support for &_maildirsize_& files. Exim
20799 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
20800 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
20801 value is zero. See &%maildir_quota_directory_regex%& above and section
20802 &<<SECTmaildirdelivery>>& below for further details.
20803
20804 .option maildirfolder_create_regex appendfile string unset
20805 .cindex "maildir format" "&_maildirfolder_& file"
20806 .cindex "&_maildirfolder_&, creating"
20807 The value of this option is a regular expression. If it is unset, it has no
20808 effect. Otherwise, before a maildir delivery takes place, the pattern is
20809 matched against the name of the maildir directory, that is, the directory
20810 containing the &_new_& and &_tmp_& subdirectories that will be used for the
20811 delivery. If there is a match, Exim checks for the existence of a file called
20812 &_maildirfolder_& in the directory, and creates it if it does not exist.
20813 See section &<<SECTmaildirdelivery>>& for more details.
20814
20815
20816 .option mailstore_format appendfile boolean false
20817 .cindex "mailstore format" "specifying"
20818 If this option is set with the &%directory%& option, the delivery is into two
20819 new files in &"mailstore"& format. The option is available only if
20820 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
20821 below for further details.
20822
20823
20824 .option mailstore_prefix appendfile string&!! unset
20825 This option applies only to deliveries in mailstore format, and is described in
20826 section &<<SECTopdir>>& below.
20827
20828
20829 .option mailstore_suffix appendfile string&!! unset
20830 This option applies only to deliveries in mailstore format, and is described in
20831 section &<<SECTopdir>>& below.
20832
20833
20834 .option mbx_format appendfile boolean false
20835 .cindex "locking files"
20836 .cindex "file" "locking"
20837 .cindex "file" "MBX format"
20838 .cindex "MBX format, specifying"
20839 This option is available only if Exim has been compiled with SUPPORT_MBX
20840 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
20841 the message is appended to the mailbox file in MBX format instead of
20842 traditional Unix format. This format is supported by Pine4 and its associated
20843 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
20844
20845 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
20846 automatically changed by the use of &%mbx_format%&. They should normally be set
20847 empty when using MBX format, so this option almost always appears in this
20848 combination:
20849 .code
20850 mbx_format = true
20851 message_prefix =
20852 message_suffix =
20853 .endd
20854 If none of the locking options are mentioned in the configuration,
20855 &%use_mbx_lock%& is assumed and the other locking options default to false. It
20856 is possible to specify the other kinds of locking with &%mbx_format%&, but
20857 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
20858 interworks with &'c-client'&, providing for shared access to the mailbox. It
20859 should not be used if any program that does not use this form of locking is
20860 going to access the mailbox, nor should it be used if the mailbox file is NFS
20861 mounted, because it works only when the mailbox is accessed from a single host.
20862
20863 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
20864 the standard version of &'c-client'&, because as long as it has a mailbox open
20865 (this means for the whole of a Pine or IMAP session), Exim will not be able to
20866 append messages to it.
20867
20868
20869 .option message_prefix appendfile string&!! "see below"
20870 .cindex "&""From""& line"
20871 The string specified here is expanded and output at the start of every message.
20872 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
20873 in which case it is:
20874 .code
20875 message_prefix = "From ${if def:return_path{$return_path}\
20876 {MAILER-DAEMON}} $tod_bsdinbox\n"
20877 .endd
20878 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
20879 &`\n`& to &`\r\n`& in &%message_prefix%&.
20880
20881 .option message_suffix appendfile string&!! "see below"
20882 The string specified here is expanded and output at the end of every message.
20883 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
20884 in which case it is a single newline character. The suffix can be suppressed by
20885 setting
20886 .code
20887 message_suffix =
20888 .endd
20889 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
20890 &`\n`& to &`\r\n`& in &%message_suffix%&.
20891
20892 .option mode appendfile "octal integer" 0600
20893 If the output file is created, it is given this mode. If it already exists and
20894 has wider permissions, they are reduced to this mode. If it has narrower
20895 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
20896 if the delivery is the result of a &%save%& command in a filter file specifying
20897 a particular mode, the mode of the output file is always forced to take that
20898 value, and this option is ignored.
20899
20900
20901 .option mode_fail_narrower appendfile boolean true
20902 This option applies in the case when an existing mailbox file has a narrower
20903 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
20904 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
20905 continues with the delivery attempt, using the existing mode of the file.
20906
20907
20908 .option notify_comsat appendfile boolean false
20909 If this option is true, the &'comsat'& daemon is notified after every
20910 successful delivery to a user mailbox. This is the daemon that notifies logged
20911 on users about incoming mail.
20912
20913
20914 .option quota appendfile string&!! unset
20915 .cindex "quota" "imposed by Exim"
20916 This option imposes a limit on the size of the file to which Exim is appending,
20917 or to the total space used in the directory tree when the &%directory%& option
20918 is set. In the latter case, computation of the space used is expensive, because
20919 all the files in the directory (and any sub-directories) have to be
20920 individually inspected and their sizes summed. (See &%quota_size_regex%& and
20921 &%maildir_use_size_file%& for ways to avoid this in environments where users
20922 have no shell access to their mailboxes).
20923
20924 As there is no interlock against two simultaneous deliveries into a
20925 multi-file mailbox, it is possible for the quota to be overrun in this case.
20926 For single-file mailboxes, of course, an interlock is a necessity.
20927
20928 A file's size is taken as its &'used'& value. Because of blocking effects, this
20929 may be a lot less than the actual amount of disk space allocated to the file.
20930 If the sizes of a number of files are being added up, the rounding effect can
20931 become quite noticeable, especially on systems that have large block sizes.
20932 Nevertheless, it seems best to stick to the &'used'& figure, because this is
20933 the obvious value which users understand most easily.
20934
20935 The value of the option is expanded, and must then be a numerical value
20936 (decimal point allowed), optionally followed by one of the letters K, M, or G,
20937 for kilobytes, megabytes, or gigabytes. If Exim is running on a system with
20938 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
20939 be handled.
20940
20941 &*Note*&: A value of zero is interpreted as &"no quota"&.
20942
20943 The expansion happens while Exim is running as root, before it changes uid for
20944 the delivery. This means that files that are inaccessible to the end user can
20945 be used to hold quota values that are looked up in the expansion. When delivery
20946 fails because this quota is exceeded, the handling of the error is as for
20947 system quota failures.
20948
20949 By default, Exim's quota checking mimics system quotas, and restricts the
20950 mailbox to the specified maximum size, though the value is not accurate to the
20951 last byte, owing to separator lines and additional headers that may get added
20952 during message delivery. When a mailbox is nearly full, large messages may get
20953 refused even though small ones are accepted, because the size of the current
20954 message is added to the quota when the check is made. This behaviour can be
20955 changed by setting &%quota_is_inclusive%& false. When this is done, the check
20956 for exceeding the quota does not include the current message. Thus, deliveries
20957 continue until the quota has been exceeded; thereafter, no further messages are
20958 delivered. See also &%quota_warn_threshold%&.
20959
20960
20961 .option quota_directory appendfile string&!! unset
20962 This option defines the directory to check for quota purposes when delivering
20963 into individual files. The default is the delivery directory, or, if a file
20964 called &_maildirfolder_& exists in a maildir directory, the parent of the
20965 delivery directory.
20966
20967
20968 .option quota_filecount appendfile string&!! 0
20969 This option applies when the &%directory%& option is set. It limits the total
20970 number of files in the directory (compare the inode limit in system quotas). It
20971 can only be used if &%quota%& is also set. The value is expanded; an expansion
20972 failure causes delivery to be deferred. A value of zero is interpreted as
20973 &"no quota"&.
20974
20975
20976 .option quota_is_inclusive appendfile boolean true
20977 See &%quota%& above.
20978
20979
20980 .option quota_size_regex appendfile string unset
20981 This option applies when one of the delivery modes that writes a separate file
20982 for each message is being used. When Exim wants to find the size of one of
20983 these files in order to test the quota, it first checks &%quota_size_regex%&.
20984 If this is set to a regular expression that matches the file name, and it
20985 captures one string, that string is interpreted as a representation of the
20986 file's size. The value of &%quota_size_regex%& is not expanded.
20987
20988 This feature is useful only when users have no shell access to their mailboxes
20989 &-- otherwise they could defeat the quota simply by renaming the files. This
20990 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
20991 the file length to the file name. For example:
20992 .code
20993 maildir_tag = ,S=$message_size
20994 quota_size_regex = ,S=(\d+)
20995 .endd
20996 An alternative to &$message_size$& is &$message_linecount$&, which contains the
20997 number of lines in the message.
20998
20999 The regular expression should not assume that the length is at the end of the
21000 file name (even though &%maildir_tag%& puts it there) because maildir MUAs
21001 sometimes add other information onto the ends of message file names.
21002
21003 Section &<<SECID136>>& contains further information.
21004
21005
21006 .option quota_warn_message appendfile string&!! "see below"
21007 See below for the use of this option. If it is not set when
21008 &%quota_warn_threshold%& is set, it defaults to
21009 .code
21010 quota_warn_message = "\
21011 To: $local_part@$domain\n\
21012 Subject: Your mailbox\n\n\
21013 This message is automatically created \
21014 by mail delivery software.\n\n\
21015 The size of your mailbox has exceeded \
21016 a warning threshold that is\n\
21017 set by the system administrator.\n"
21018 .endd
21019
21020
21021 .option quota_warn_threshold appendfile string&!! 0
21022 .cindex "quota" "warning threshold"
21023 .cindex "mailbox" "size warning"
21024 .cindex "size" "of mailbox"
21025 This option is expanded in the same way as &%quota%& (see above). If the
21026 resulting value is greater than zero, and delivery of the message causes the
21027 size of the file or total space in the directory tree to cross the given
21028 threshold, a warning message is sent. If &%quota%& is also set, the threshold
21029 may be specified as a percentage of it by following the value with a percent
21030 sign. For example:
21031 .code
21032 quota = 10M
21033 quota_warn_threshold = 75%
21034 .endd
21035 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
21036 percent sign is ignored.
21037
21038 The warning message itself is specified by the &%quota_warn_message%& option,
21039 and it must start with a &'To:'& header line containing the recipient(s) of the
21040 warning message. These do not necessarily have to include the recipient(s) of
21041 the original message. A &'Subject:'& line should also normally be supplied. You
21042 can include any other header lines that you want. If you do not include a
21043 &'From:'& line, the default is:
21044 .code
21045 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
21046 .endd
21047 .oindex &%errors_reply_to%&
21048 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
21049 option.
21050
21051 The &%quota%& option does not have to be set in order to use this option; they
21052 are independent of one another except when the threshold is specified as a
21053 percentage.
21054
21055
21056 .option use_bsmtp appendfile boolean false
21057 .cindex "envelope sender"
21058 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
21059 format, with the envelope sender and recipient(s) included as SMTP commands. If
21060 you want to include a leading HELO command with such messages, you can do
21061 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
21062 for details of batch SMTP.
21063
21064
21065 .option use_crlf appendfile boolean false
21066 .cindex "carriage return"
21067 .cindex "linefeed"
21068 This option causes lines to be terminated with the two-character CRLF sequence
21069 (carriage return, linefeed) instead of just a linefeed character. In the case
21070 of batched SMTP, the byte sequence written to the file is then an exact image
21071 of what would be sent down a real SMTP connection.
21072
21073 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
21074 (which are used to supply the traditional &"From&~"& and blank line separators
21075 in Berkeley-style mailboxes) are written verbatim, so must contain their own
21076 carriage return characters if these are needed. In cases where these options
21077 have non-empty defaults, the values end with a single linefeed, so they must be
21078 changed to end with &`\r\n`& if &%use_crlf%& is set.
21079
21080
21081 .option use_fcntl_lock appendfile boolean "see below"
21082 This option controls the use of the &[fcntl()]& function to lock a file for
21083 exclusive use when a message is being appended. It is set by default unless
21084 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
21085 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
21086 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
21087
21088
21089 .option use_flock_lock appendfile boolean false
21090 This option is provided to support the use of &[flock()]& for file locking, for
21091 the few situations where it is needed. Most modern operating systems support
21092 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
21093 each other. Exim uses &[fcntl()]& locking by default.
21094
21095 This option is required only if you are using an operating system where
21096 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
21097 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
21098 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
21099
21100 .cindex "Solaris" "&[flock()]& support"
21101 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
21102 have it (and some, I think, provide a not quite right version built on top of
21103 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
21104 the ability to use it, and any attempt to do so will cause a configuration
21105 error.
21106
21107 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
21108 is just being mapped onto &[fcntl()]& by the OS).
21109
21110
21111 .option use_lockfile appendfile boolean "see below"
21112 If this option is turned off, Exim does not attempt to create a lock file when
21113 appending to a mailbox file. In this situation, the only locking is by
21114 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
21115 sure that every MUA that is ever going to look at your users' mailboxes uses
21116 &[fcntl()]& rather than a lock file, and even then only when you are not
21117 delivering over NFS from more than one host.
21118
21119 .cindex "NFS" "lock file"
21120 In order to append to an NFS file safely from more than one host, it is
21121 necessary to take out a lock &'before'& opening the file, and the lock file
21122 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
21123 file corruption.
21124
21125 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
21126 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
21127 except when &%mbx_format%& is set.
21128
21129
21130 .option use_mbx_lock appendfile boolean "see below"
21131 This option is available only if Exim has been compiled with SUPPORT_MBX
21132 set in &_Local/Makefile_&. Setting the option specifies that special MBX
21133 locking rules be used. It is set by default if &%mbx_format%& is set and none
21134 of the locking options are mentioned in the configuration. The locking rules
21135 are the same as are used by the &'c-client'& library that underlies Pine and
21136 the IMAP4 and POP daemons that come with it (see the discussion below). The
21137 rules allow for shared access to the mailbox. However, this kind of locking
21138 does not work when the mailbox is NFS mounted.
21139
21140 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
21141 &%use_flock_lock%& to control what kind of locking is used in implementing the
21142 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
21143 without &%use_fcntl_lock%& or &%use_flock_lock%&.
21144
21145
21146
21147
21148 .section "Operational details for appending" "SECTopappend"
21149 .cindex "appending to a file"
21150 .cindex "file" "appending"
21151 Before appending to a file, the following preparations are made:
21152
21153 .ilist
21154 If the name of the file is &_/dev/null_&, no action is taken, and a success
21155 return is given.
21156
21157 .next
21158 .cindex "directory creation"
21159 If any directories on the file's path are missing, Exim creates them if the
21160 &%create_directory%& option is set. A created directory's mode is given by the
21161 &%directory_mode%& option.
21162
21163 .next
21164 If &%file_format%& is set, the format of an existing file is checked. If this
21165 indicates that a different transport should be used, control is passed to that
21166 transport.
21167
21168 .next
21169 .cindex "file" "locking"
21170 .cindex "locking files"
21171 .cindex "NFS" "lock file"
21172 If &%use_lockfile%& is set, a lock file is built in a way that will work
21173 reliably over NFS, as follows:
21174
21175 .olist
21176 Create a &"hitching post"& file whose name is that of the lock file with the
21177 current time, primary host name, and process id added, by opening for writing
21178 as a new file. If this fails with an access error, delivery is deferred.
21179 .next
21180 Close the hitching post file, and hard link it to the lock file name.
21181 .next
21182 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
21183 Unlink the hitching post name.
21184 .next
21185 Otherwise, use &[stat()]& to get information about the hitching post file, and
21186 then unlink hitching post name. If the number of links is exactly two, creation
21187 of the lock file succeeded but something (for example, an NFS server crash and
21188 restart) caused this fact not to be communicated to the &[link()]& call.
21189 .next
21190 If creation of the lock file failed, wait for &%lock_interval%& and try again,
21191 up to &%lock_retries%& times. However, since any program that writes to a
21192 mailbox should complete its task very quickly, it is reasonable to time out old
21193 lock files that are normally the result of user agent and system crashes. If an
21194 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
21195 it before trying again.
21196 .endlist olist
21197
21198 .next
21199 A call is made to &[lstat()]& to discover whether the main file exists, and if
21200 so, what its characteristics are. If &[lstat()]& fails for any reason other
21201 than non-existence, delivery is deferred.
21202
21203 .next
21204 .cindex "symbolic link" "to mailbox"
21205 .cindex "mailbox" "symbolic link"
21206 If the file does exist and is a symbolic link, delivery is deferred, unless the
21207 &%allow_symlink%& option is set, in which case the ownership of the link is
21208 checked, and then &[stat()]& is called to find out about the real file, which
21209 is then subjected to the checks below. The check on the top-level link
21210 ownership prevents one user creating a link for another's mailbox in a sticky
21211 directory, though allowing symbolic links in this case is definitely not a good
21212 idea. If there is a chain of symbolic links, the intermediate ones are not
21213 checked.
21214
21215 .next
21216 If the file already exists but is not a regular file, or if the file's owner
21217 and group (if the group is being checked &-- see &%check_group%& above) are
21218 different from the user and group under which the delivery is running,
21219 delivery is deferred.
21220
21221 .next
21222 If the file's permissions are more generous than specified, they are reduced.
21223 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
21224 is set false, in which case the delivery is tried using the existing
21225 permissions.
21226
21227 .next
21228 The file's inode number is saved, and the file is then opened for appending.
21229 If this fails because the file has vanished, &(appendfile)& behaves as if it
21230 hadn't existed (see below). For any other failures, delivery is deferred.
21231
21232 .next
21233 If the file is opened successfully, check that the inode number hasn't
21234 changed, that it is still a regular file, and that the owner and permissions
21235 have not changed. If anything is wrong, defer delivery and freeze the message.
21236
21237 .next
21238 If the file did not exist originally, defer delivery if the &%file_must_exist%&
21239 option is set. Otherwise, check that the file is being created in a permitted
21240 directory if the &%create_file%& option is set (deferring on failure), and then
21241 open for writing as a new file, with the O_EXCL and O_CREAT options,
21242 except when dealing with a symbolic link (the &%allow_symlink%& option must be
21243 set). In this case, which can happen if the link points to a non-existent file,
21244 the file is opened for writing using O_CREAT but not O_EXCL, because
21245 that prevents link following.
21246
21247 .next
21248 .cindex "loop" "while file testing"
21249 If opening fails because the file exists, obey the tests given above for
21250 existing files. However, to avoid looping in a situation where the file is
21251 being continuously created and destroyed, the exists/not-exists loop is broken
21252 after 10 repetitions, and the message is then frozen.
21253
21254 .next
21255 If opening fails with any other error, defer delivery.
21256
21257 .next
21258 .cindex "file" "locking"
21259 .cindex "locking files"
21260 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
21261 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
21262 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
21263 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
21264 file, and an exclusive lock on the file whose name is
21265 .code
21266 /tmp/.<device-number>.<inode-number>
21267 .endd
21268 using the device and inode numbers of the open mailbox file, in accordance with
21269 the MBX locking rules. This file is created with a mode that is specified by
21270 the &%lockfile_mode%& option.
21271
21272 If Exim fails to lock the file, there are two possible courses of action,
21273 depending on the value of the locking timeout. This is obtained from
21274 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
21275
21276 If the timeout value is zero, the file is closed, Exim waits for
21277 &%lock_interval%&, and then goes back and re-opens the file as above and tries
21278 to lock it again. This happens up to &%lock_retries%& times, after which the
21279 delivery is deferred.
21280
21281 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
21282 &[flock()]& are used (with the given timeout), so there has already been some
21283 waiting involved by the time locking fails. Nevertheless, Exim does not give up
21284 immediately. It retries up to
21285 .code
21286 (lock_retries * lock_interval) / <timeout>
21287 .endd
21288 times (rounded up).
21289 .endlist
21290
21291 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
21292 and/or &[flock()]& locks) and then deletes the lock file if one was created.
21293
21294
21295 .section "Operational details for delivery to a new file" "SECTopdir"
21296 .cindex "delivery" "to single file"
21297 .cindex "&""From""& line"
21298 When the &%directory%& option is set instead of &%file%&, each message is
21299 delivered into a newly-created file or set of files. When &(appendfile)& is
21300 activated directly from a &(redirect)& router, neither &%file%& nor
21301 &%directory%& is normally set, because the path for delivery is supplied by the
21302 router. (See for example, the &(address_file)& transport in the default
21303 configuration.) In this case, delivery is to a new file if either the path name
21304 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
21305
21306 No locking is required while writing the message to a new file, so the various
21307 locking options of the transport are ignored. The &"From"& line that by default
21308 separates messages in a single file is not normally needed, nor is the escaping
21309 of message lines that start with &"From"&, and there is no need to ensure a
21310 newline at the end of each message. Consequently, the default values for
21311 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
21312 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
21313
21314 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
21315 the files in the delivery directory by default. However, you can specify a
21316 different directory by setting &%quota_directory%&. Also, for maildir
21317 deliveries (see below) the &_maildirfolder_& convention is honoured.
21318
21319
21320 .cindex "maildir format"
21321 .cindex "mailstore format"
21322 There are three different ways in which delivery to individual files can be
21323 done, controlled by the settings of the &%maildir_format%& and
21324 &%mailstore_format%& options. Note that code to support maildir or mailstore
21325 formats is not included in the binary unless SUPPORT_MAILDIR or
21326 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
21327
21328 .cindex "directory creation"
21329 In all three cases an attempt is made to create the directory and any necessary
21330 sub-directories if they do not exist, provided that the &%create_directory%&
21331 option is set (the default). The location of a created directory can be
21332 constrained by setting &%create_file%&. A created directory's mode is given by
21333 the &%directory_mode%& option. If creation fails, or if the
21334 &%create_directory%& option is not set when creation is required, delivery is
21335 deferred.
21336
21337
21338
21339 .section "Maildir delivery" "SECTmaildirdelivery"
21340 .cindex "maildir format" "description of"
21341 If the &%maildir_format%& option is true, Exim delivers each message by writing
21342 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
21343 directory that is defined by the &%directory%& option (the &"delivery
21344 directory"&). If the delivery is successful, the file is renamed into the
21345 &_new_& subdirectory.
21346
21347 In the file name, <&'stime'&> is the current time of day in seconds, and
21348 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
21349 Exim checks that the time-of-day clock has moved on by at least one microsecond
21350 before terminating the delivery process. This guarantees uniqueness for the
21351 file name. However, as a precaution, Exim calls &[stat()]& for the file before
21352 opening it. If any response other than ENOENT (does not exist) is given,
21353 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
21354
21355 Before Exim carries out a maildir delivery, it ensures that subdirectories
21356 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
21357 do not exist, Exim tries to create them and any superior directories in their
21358 path, subject to the &%create_directory%& and &%create_file%& options. If the
21359 &%maildirfolder_create_regex%& option is set, and the regular expression it
21360 contains matches the delivery directory, Exim also ensures that a file called
21361 &_maildirfolder_& exists in the delivery directory. If a missing directory or
21362 &_maildirfolder_& file cannot be created, delivery is deferred.
21363
21364 These features make it possible to use Exim to create all the necessary files
21365 and directories in a maildir mailbox, including subdirectories for maildir++
21366 folders. Consider this example:
21367 .code
21368 maildir_format = true
21369 directory = /var/mail/$local_part\
21370 ${if eq{$local_part_suffix}{}{}\
21371 {/.${substr_1:$local_part_suffix}}}
21372 maildirfolder_create_regex = /\.[^/]+$
21373 .endd
21374 If &$local_part_suffix$& is empty (there was no suffix for the local part),
21375 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
21376 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
21377 not match this name, so Exim will not look for or create the file
21378 &_/var/mail/pimbo/maildirfolder_&, though it will create
21379 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
21380
21381 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
21382 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
21383 does match &%maildirfolder_create_regex%&. In this case, Exim will create
21384 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
21385 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
21386
21387 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
21388 not inadvertently match the toplevel maildir directory, because a
21389 &_maildirfolder_& file at top level would completely break quota calculations.
21390
21391 .cindex "quota" "in maildir delivery"
21392 .cindex "maildir++"
21393 If Exim is required to check a &%quota%& setting before a maildir delivery, and
21394 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
21395 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
21396 Exim assumes the directory is a maildir++ folder directory, which is one level
21397 down from the user's top level mailbox directory. This causes it to start at
21398 the parent directory instead of the current directory when calculating the
21399 amount of space used.
21400
21401 One problem with delivering into a multi-file mailbox is that it is
21402 computationally expensive to compute the size of the mailbox for quota
21403 checking. Various approaches have been taken to reduce the amount of work
21404 needed. The next two sections describe two of them. A third alternative is to
21405 use some external process for maintaining the size data, and use the expansion
21406 of the &%mailbox_size%& option as a way of importing it into Exim.
21407
21408
21409
21410
21411 .section "Using tags to record message sizes" "SECID135"
21412 If &%maildir_tag%& is set, the string is expanded for each delivery.
21413 When the maildir file is renamed into the &_new_& sub-directory, the
21414 tag is added to its name. However, if adding the tag takes the length of the
21415 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
21416 the tag is dropped and the maildir file is created with no tag.
21417
21418
21419 .vindex "&$message_size$&"
21420 Tags can be used to encode the size of files in their names; see
21421 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
21422 happens after the message has been written. The value of the &$message_size$&
21423 variable is set to the number of bytes actually written. If the expansion is
21424 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
21425 be deferred. The expanded tag may contain any printing characters except &"/"&.
21426 Non-printing characters in the string are ignored; if the resulting string is
21427 empty, it is ignored. If it starts with an alphanumeric character, a leading
21428 colon is inserted; this default has not proven to be the path that popular
21429 maildir implementations have chosen (but changing it in Exim would break
21430 backwards compatibility).
21431
21432 For one common implementation, you might set:
21433 .code
21434 maildir_tag = ,S=${message_size}
21435 .endd
21436 but you should check the documentation of the other software to be sure.
21437
21438 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
21439 as this allows Exim to extract the size from your tag, instead of having to
21440 &[stat()]& each message file.
21441
21442
21443 .section "Using a maildirsize file" "SECID136"
21444 .cindex "quota" "in maildir delivery"
21445 .cindex "maildir format" "&_maildirsize_& file"
21446 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
21447 storing quota and message size information in a file called &_maildirsize_&
21448 within the toplevel maildir directory. If this file does not exist, Exim
21449 creates it, setting the quota from the &%quota%& option of the transport. If
21450 the maildir directory itself does not exist, it is created before any attempt
21451 to write a &_maildirsize_& file.
21452
21453 The &_maildirsize_& file is used to hold information about the sizes of
21454 messages in the maildir, thus speeding up quota calculations. The quota value
21455 in the file is just a cache; if the quota is changed in the transport, the new
21456 value overrides the cached value when the next message is delivered. The cache
21457 is maintained for the benefit of other programs that access the maildir and
21458 need to know the quota.
21459
21460 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
21461 file is maintained (with a zero quota setting), but no quota is imposed.
21462
21463 A regular expression is available for controlling which directories in the
21464 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
21465 See the description of the &%maildir_quota_directory_regex%& option above for
21466 details.
21467
21468
21469 .section "Mailstore delivery" "SECID137"
21470 .cindex "mailstore format" "description of"
21471 If the &%mailstore_format%& option is true, each message is written as two
21472 files in the given directory. A unique base name is constructed from the
21473 message id and the current delivery process, and the files that are written use
21474 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
21475 contains the message's envelope, and the &_.msg_& file contains the message
21476 itself. The base name is placed in the variable &$mailstore_basename$&.
21477
21478 During delivery, the envelope is first written to a file with the suffix
21479 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
21480 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
21481 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
21482 file before accessing either of them. An alternative approach is to wait for
21483 the absence of a &_.tmp_& file.
21484
21485 The envelope file starts with any text defined by the &%mailstore_prefix%&
21486 option, expanded and terminated by a newline if there isn't one. Then follows
21487 the sender address on one line, then all the recipient addresses, one per line.
21488 There can be more than one recipient only if the &%batch_max%& option is set
21489 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
21490 appended to the file, followed by a newline if it does not end with one.
21491
21492 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
21493 failure, it is ignored. Other expansion errors are treated as serious
21494 configuration errors, and delivery is deferred. The variable
21495 &$mailstore_basename$& is available for use during these expansions.
21496
21497
21498 .section "Non-special new file delivery" "SECID138"
21499 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
21500 file is created directly in the named directory. For example, when delivering
21501 messages into files in batched SMTP format for later delivery to some host (see
21502 section &<<SECTbatchSMTP>>&), a setting such as
21503 .code
21504 directory = /var/bsmtp/$host
21505 .endd
21506 might be used. A message is written to a file with a temporary name, which is
21507 then renamed when the delivery is complete. The final name is obtained by
21508 expanding the contents of the &%directory_file%& option.
21509 .ecindex IIDapptra1
21510 .ecindex IIDapptra2
21511
21512
21513
21514
21515
21516
21517 . ////////////////////////////////////////////////////////////////////////////
21518 . ////////////////////////////////////////////////////////////////////////////
21519
21520 .chapter "The autoreply transport" "CHID8"
21521 .scindex IIDauttra1 "transports" "&(autoreply)&"
21522 .scindex IIDauttra2 "&(autoreply)& transport"
21523 The &(autoreply)& transport is not a true transport in that it does not cause
21524 the message to be transmitted. Instead, it generates a new mail message as an
21525 automatic reply to the incoming message. &'References:'& and
21526 &'Auto-Submitted:'& header lines are included. These are constructed according
21527 to the rules in RFCs 2822 and 3834, respectively.
21528
21529 If the router that passes the message to this transport does not have the
21530 &%unseen%& option set, the original message (for the current recipient) is not
21531 delivered anywhere. However, when the &%unseen%& option is set on the router
21532 that passes the message to this transport, routing of the address continues, so
21533 another router can set up a normal message delivery.
21534
21535
21536 The &(autoreply)& transport is usually run as the result of mail filtering, a
21537 &"vacation"& message being the standard example. However, it can also be run
21538 directly from a router like any other transport. To reduce the possibility of
21539 message cascades, messages created by the &(autoreply)& transport always have
21540 empty envelope sender addresses, like bounce messages.
21541
21542 The parameters of the message to be sent can be specified in the configuration
21543 by options described below. However, these are used only when the address
21544 passed to the transport does not contain its own reply information. When the
21545 transport is run as a consequence of a
21546 &%mail%&
21547 or &%vacation%& command in a filter file, the parameters of the message are
21548 supplied by the filter, and passed with the address. The transport's options
21549 that define the message are then ignored (so they are not usually set in this
21550 case). The message is specified entirely by the filter or by the transport; it
21551 is never built from a mixture of options. However, the &%file_optional%&,
21552 &%mode%&, and &%return_message%& options apply in all cases.
21553
21554 &(Autoreply)& is implemented as a local transport. When used as a result of a
21555 command in a user's filter file, &(autoreply)& normally runs under the uid and
21556 gid of the user, and with appropriate current and home directories (see chapter
21557 &<<CHAPenvironment>>&).
21558
21559 There is a subtle difference between routing a message to a &(pipe)& transport
21560 that generates some text to be returned to the sender, and routing it to an
21561 &(autoreply)& transport. This difference is noticeable only if more than one
21562 address from the same message is so handled. In the case of a pipe, the
21563 separate outputs from the different addresses are gathered up and returned to
21564 the sender in a single message, whereas if &(autoreply)& is used, a separate
21565 message is generated for each address that is passed to it.
21566
21567 Non-printing characters are not permitted in the header lines generated for the
21568 message that &(autoreply)& creates, with the exception of newlines that are
21569 immediately followed by white space. If any non-printing characters are found,
21570 the transport defers.
21571 Whether characters with the top bit set count as printing characters or not is
21572 controlled by the &%print_topbitchars%& global option.
21573
21574 If any of the generic options for manipulating headers (for example,
21575 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
21576 of the original message that is included in the generated message when
21577 &%return_message%& is set. They do not apply to the generated message itself.
21578
21579 .vindex "&$sender_address$&"
21580 If the &(autoreply)& transport receives return code 2 from Exim when it submits
21581 the message, indicating that there were no recipients, it does not treat this
21582 as an error. This means that autoreplies sent to &$sender_address$& when this
21583 is empty (because the incoming message is a bounce message) do not cause
21584 problems. They are just discarded.
21585
21586
21587
21588 .section "Private options for autoreply" "SECID139"
21589 .cindex "options" "&(autoreply)& transport"
21590
21591 .option bcc autoreply string&!! unset
21592 This specifies the addresses that are to receive &"blind carbon copies"& of the
21593 message when the message is specified by the transport.
21594
21595
21596 .option cc autoreply string&!! unset
21597 This specifies recipients of the message and the contents of the &'Cc:'& header
21598 when the message is specified by the transport.
21599
21600
21601 .option file autoreply string&!! unset
21602 The contents of the file are sent as the body of the message when the message
21603 is specified by the transport. If both &%file%& and &%text%& are set, the text
21604 string comes first.
21605
21606
21607 .option file_expand autoreply boolean false
21608 If this is set, the contents of the file named by the &%file%& option are
21609 subjected to string expansion as they are added to the message.
21610
21611
21612 .option file_optional autoreply boolean false
21613 If this option is true, no error is generated if the file named by the &%file%&
21614 option or passed with the address does not exist or cannot be read.
21615
21616
21617 .option from autoreply string&!! unset
21618 This specifies the contents of the &'From:'& header when the message is
21619 specified by the transport.
21620
21621
21622 .option headers autoreply string&!! unset
21623 This specifies additional RFC 2822 headers that are to be added to the message
21624 when the message is specified by the transport. Several can be given by using
21625 &"\n"& to separate them. There is no check on the format.
21626
21627
21628 .option log autoreply string&!! unset
21629 This option names a file in which a record of every message sent is logged when
21630 the message is specified by the transport.
21631
21632
21633 .option mode autoreply "octal integer" 0600
21634 If either the log file or the &"once"& file has to be created, this mode is
21635 used.
21636
21637
21638 .option never_mail autoreply "address list&!!" unset
21639 If any run of the transport creates a message with a recipient that matches any
21640 item in the list, that recipient is quietly discarded. If all recipients are
21641 discarded, no message is created. This applies both when the recipients are
21642 generated by a filter and when they are specified in the transport.
21643
21644
21645
21646 .option once autoreply string&!! unset
21647 This option names a file or DBM database in which a record of each &'To:'&
21648 recipient is kept when the message is specified by the transport. &*Note*&:
21649 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
21650
21651 If &%once%& is unset, or is set to an empty string, the message is always sent.
21652 By default, if &%once%& is set to a non-empty file name, the message
21653 is not sent if a potential recipient is already listed in the database.
21654 However, if the &%once_repeat%& option specifies a time greater than zero, the
21655 message is sent if that much time has elapsed since a message was last sent to
21656 this recipient. A setting of zero time for &%once_repeat%& (the default)
21657 prevents a message from being sent a second time &-- in this case, zero means
21658 infinity.
21659
21660 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
21661 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
21662 greater than zero, it changes the way Exim implements the &%once%& option.
21663 Instead of using a DBM file to record every recipient it sends to, it uses a
21664 regular file, whose size will never get larger than the given value.
21665
21666 In the file, Exim keeps a linear list of recipient addresses and the times at
21667 which they were sent messages. If the file is full when a new address needs to
21668 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
21669 means that a given recipient may receive multiple messages, but at
21670 unpredictable intervals that depend on the rate of turnover of addresses in the
21671 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
21672
21673
21674 .option once_file_size autoreply integer 0
21675 See &%once%& above.
21676
21677
21678 .option once_repeat autoreply time&!! 0s
21679 See &%once%& above.
21680 After expansion, the value of this option must be a valid time value.
21681
21682
21683 .option reply_to autoreply string&!! unset
21684 This specifies the contents of the &'Reply-To:'& header when the message is
21685 specified by the transport.
21686
21687
21688 .option return_message autoreply boolean false
21689 If this is set, a copy of the original message is returned with the new
21690 message, subject to the maximum size set in the &%return_size_limit%& global
21691 configuration option.
21692
21693
21694 .option subject autoreply string&!! unset
21695 This specifies the contents of the &'Subject:'& header when the message is
21696 specified by the transport. It is tempting to quote the original subject in
21697 automatic responses. For example:
21698 .code
21699 subject = Re: $h_subject:
21700 .endd
21701 There is a danger in doing this, however. It may allow a third party to
21702 subscribe your users to an opt-in mailing list, provided that the list accepts
21703 bounce messages as subscription confirmations. Well-managed lists require a
21704 non-bounce message to confirm a subscription, so the danger is relatively
21705 small.
21706
21707
21708
21709 .option text autoreply string&!! unset
21710 This specifies a single string to be used as the body of the message when the
21711 message is specified by the transport. If both &%text%& and &%file%& are set,
21712 the text comes first.
21713
21714
21715 .option to autoreply string&!! unset
21716 This specifies recipients of the message and the contents of the &'To:'& header
21717 when the message is specified by the transport.
21718 .ecindex IIDauttra1
21719 .ecindex IIDauttra2
21720
21721
21722
21723
21724 . ////////////////////////////////////////////////////////////////////////////
21725 . ////////////////////////////////////////////////////////////////////////////
21726
21727 .chapter "The lmtp transport" "CHAPLMTP"
21728 .cindex "transports" "&(lmtp)&"
21729 .cindex "&(lmtp)& transport"
21730 .cindex "LMTP" "over a pipe"
21731 .cindex "LMTP" "over a socket"
21732 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
21733 specified command
21734 or by interacting with a Unix domain socket.
21735 This transport is something of a cross between the &(pipe)& and &(smtp)&
21736 transports. Exim also has support for using LMTP over TCP/IP; this is
21737 implemented as an option for the &(smtp)& transport. Because LMTP is expected
21738 to be of minority interest, the default build-time configure in &_src/EDITME_&
21739 has it commented out. You need to ensure that
21740 .code
21741 TRANSPORT_LMTP=yes
21742 .endd
21743 .cindex "options" "&(lmtp)& transport"
21744 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
21745 included in the Exim binary. The private options of the &(lmtp)& transport are
21746 as follows:
21747
21748 .option batch_id lmtp string&!! unset
21749 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21750
21751
21752 .option batch_max lmtp integer 1
21753 This limits the number of addresses that can be handled in a single delivery.
21754 Most LMTP servers can handle several addresses at once, so it is normally a
21755 good idea to increase this value. See the description of local delivery
21756 batching in chapter &<<CHAPbatching>>&.
21757
21758
21759 .option command lmtp string&!! unset
21760 This option must be set if &%socket%& is not set. The string is a command which
21761 is run in a separate process. It is split up into a command name and list of
21762 arguments, each of which is separately expanded (so expansion cannot change the
21763 number of arguments). The command is run directly, not via a shell. The message
21764 is passed to the new process using the standard input and output to operate the
21765 LMTP protocol.
21766
21767 .option ignore_quota lmtp boolean false
21768 .cindex "LMTP" "ignoring quota errors"
21769 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
21770 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
21771 in its response to the LHLO command.
21772
21773 .option socket lmtp string&!! unset
21774 This option must be set if &%command%& is not set. The result of expansion must
21775 be the name of a Unix domain socket. The transport connects to the socket and
21776 delivers the message to it using the LMTP protocol.
21777
21778
21779 .option timeout lmtp time 5m
21780 The transport is aborted if the created process or Unix domain socket does not
21781 respond to LMTP commands or message input within this timeout. Delivery
21782 is deferred, and will be tried again later. Here is an example of a typical
21783 LMTP transport:
21784 .code
21785 lmtp:
21786 driver = lmtp
21787 command = /some/local/lmtp/delivery/program
21788 batch_max = 20
21789 user = exim
21790 .endd
21791 This delivers up to 20 addresses at a time, in a mixture of domains if
21792 necessary, running as the user &'exim'&.
21793
21794
21795
21796 . ////////////////////////////////////////////////////////////////////////////
21797 . ////////////////////////////////////////////////////////////////////////////
21798
21799 .chapter "The pipe transport" "CHAPpipetransport"
21800 .scindex IIDpiptra1 "transports" "&(pipe)&"
21801 .scindex IIDpiptra2 "&(pipe)& transport"
21802 The &(pipe)& transport is used to deliver messages via a pipe to a command
21803 running in another process. One example is the use of &(pipe)& as a
21804 pseudo-remote transport for passing messages to some other delivery mechanism
21805 (such as UUCP). Another is the use by individual users to automatically process
21806 their incoming messages. The &(pipe)& transport can be used in one of the
21807 following ways:
21808
21809 .ilist
21810 .vindex "&$local_part$&"
21811 A router routes one address to a transport in the normal way, and the
21812 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
21813 contains the local part of the address (as usual), and the command that is run
21814 is specified by the &%command%& option on the transport.
21815 .next
21816 .vindex "&$pipe_addresses$&"
21817 If the &%batch_max%& option is set greater than 1 (the default is 1), the
21818 transport can handle more than one address in a single run. In this case, when
21819 more than one address is routed to the transport, &$local_part$& is not set
21820 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
21821 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
21822 that are routed to the transport.
21823 .next
21824 .vindex "&$address_pipe$&"
21825 A router redirects an address directly to a pipe command (for example, from an
21826 alias or forward file). In this case, &$address_pipe$& contains the text of the
21827 pipe command, and the &%command%& option on the transport is ignored unless
21828 &%force_command%& is set. If only one address is being transported
21829 (&%batch_max%& is not greater than one, or only one address was redirected to
21830 this pipe command), &$local_part$& contains the local part that was redirected.
21831 .endlist
21832
21833
21834 The &(pipe)& transport is a non-interactive delivery method. Exim can also
21835 deliver messages over pipes using the LMTP interactive protocol. This is
21836 implemented by the &(lmtp)& transport.
21837
21838 In the case when &(pipe)& is run as a consequence of an entry in a local user's
21839 &_.forward_& file, the command runs under the uid and gid of that user. In
21840 other cases, the uid and gid have to be specified explicitly, either on the
21841 transport or on the router that handles the address. Current and &"home"&
21842 directories are also controllable. See chapter &<<CHAPenvironment>>& for
21843 details of the local delivery environment and chapter &<<CHAPbatching>>&
21844 for a discussion of local delivery batching.
21845
21846
21847 .section "Concurrent delivery" "SECID140"
21848 If two messages arrive at almost the same time, and both are routed to a pipe
21849 delivery, the two pipe transports may be run concurrently. You must ensure that
21850 any pipe commands you set up are robust against this happening. If the commands
21851 write to a file, the &%exim_lock%& utility might be of use.
21852
21853
21854
21855
21856 .section "Returned status and data" "SECID141"
21857 .cindex "&(pipe)& transport" "returned data"
21858 If the command exits with a non-zero return code, the delivery is deemed to
21859 have failed, unless either the &%ignore_status%& option is set (in which case
21860 the return code is treated as zero), or the return code is one of those listed
21861 in the &%temp_errors%& option, which are interpreted as meaning &"try again
21862 later"&. In this case, delivery is deferred. Details of a permanent failure are
21863 logged, but are not included in the bounce message, which merely contains
21864 &"local delivery failed"&.
21865
21866 If the command exits on a signal and the &%freeze_signal%& option is set then
21867 the message will be frozen in the queue. If that option is not set, a bounce
21868 will be sent as normal.
21869
21870 If the return code is greater than 128 and the command being run is a shell
21871 script, it normally means that the script was terminated by a signal whose
21872 value is the return code minus 128. The &%freeze_signal%& option does not
21873 apply in this case.
21874
21875 If Exim is unable to run the command (that is, if &[execve()]& fails), the
21876 return code is set to 127. This is the value that a shell returns if it is
21877 asked to run a non-existent command. The wording for the log line suggests that
21878 a non-existent command may be the problem.
21879
21880 The &%return_output%& option can affect the result of a pipe delivery. If it is
21881 set and the command produces any output on its standard output or standard
21882 error streams, the command is considered to have failed, even if it gave a zero
21883 return code or if &%ignore_status%& is set. The output from the command is
21884 included as part of the bounce message. The &%return_fail_output%& option is
21885 similar, except that output is returned only when the command exits with a
21886 failure return code, that is, a value other than zero or a code that matches
21887 &%temp_errors%&.
21888
21889
21890
21891 .section "How the command is run" "SECThowcommandrun"
21892 .cindex "&(pipe)& transport" "path for command"
21893 The command line is (by default) broken down into a command name and arguments
21894 by the &(pipe)& transport itself. The &%allow_commands%& and
21895 &%restrict_to_path%& options can be used to restrict the commands that may be
21896 run.
21897
21898 .cindex "quoting" "in pipe command"
21899 Unquoted arguments are delimited by white space. If an argument appears in
21900 double quotes, backslash is interpreted as an escape character in the usual
21901 way. If an argument appears in single quotes, no escaping is done.
21902
21903 String expansion is applied to the command line except when it comes from a
21904 traditional &_.forward_& file (commands from a filter file are expanded). The
21905 expansion is applied to each argument in turn rather than to the whole line.
21906 For this reason, any string expansion item that contains white space must be
21907 quoted so as to be contained within a single argument. A setting such as
21908 .code
21909 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
21910 .endd
21911 will not work, because the expansion item gets split between several
21912 arguments. You have to write
21913 .code
21914 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
21915 .endd
21916 to ensure that it is all in one argument. The expansion is done in this way,
21917 argument by argument, so that the number of arguments cannot be changed as a
21918 result of expansion, and quotes or backslashes in inserted variables do not
21919 interact with external quoting. However, this leads to problems if you want to
21920 generate multiple arguments (or the command name plus arguments) from a single
21921 expansion. In this situation, the simplest solution is to use a shell. For
21922 example:
21923 .code
21924 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
21925 .endd
21926
21927 .cindex "transport" "filter"
21928 .cindex "filter" "transport filter"
21929 .vindex "&$pipe_addresses$&"
21930 Special handling takes place when an argument consists of precisely the text
21931 &`$pipe_addresses`&. This is not a general expansion variable; the only
21932 place this string is recognized is when it appears as an argument for a pipe or
21933 transport filter command. It causes each address that is being handled to be
21934 inserted in the argument list at that point &'as a separate argument'&. This
21935 avoids any problems with spaces or shell metacharacters, and is of use when a
21936 &(pipe)& transport is handling groups of addresses in a batch.
21937
21938 If &%force_command%& is enabled on the transport, Special handling takes place
21939 for an argument that consists of precisely the text &`$address_pipe`&. It
21940 is handled similarly to &$pipe_addresses$& above. It is expanded and each
21941 argument is inserted in the argument list at that point
21942 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
21943 the only item in the argument; in fact, if it were then &%force_command%&
21944 should behave as a no-op. Rather, it should be used to adjust the command
21945 run while preserving the argument vector separation.
21946
21947 After splitting up into arguments and expansion, the resulting command is run
21948 in a subprocess directly from the transport, &'not'& under a shell. The
21949 message that is being delivered is supplied on the standard input, and the
21950 standard output and standard error are both connected to a single pipe that is
21951 read by Exim. The &%max_output%& option controls how much output the command
21952 may produce, and the &%return_output%& and &%return_fail_output%& options
21953 control what is done with it.
21954
21955 Not running the command under a shell (by default) lessens the security risks
21956 in cases when a command from a user's filter file is built out of data that was
21957 taken from an incoming message. If a shell is required, it can of course be
21958 explicitly specified as the command to be run. However, there are circumstances
21959 where existing commands (for example, in &_.forward_& files) expect to be run
21960 under a shell and cannot easily be modified. To allow for these cases, there is
21961 an option called &%use_shell%&, which changes the way the &(pipe)& transport
21962 works. Instead of breaking up the command line as just described, it expands it
21963 as a single string and passes the result to &_/bin/sh_&. The
21964 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
21965 with &%use_shell%&, and the whole mechanism is inherently less secure.
21966
21967
21968
21969 .section "Environment variables" "SECTpipeenv"
21970 .cindex "&(pipe)& transport" "environment for command"
21971 .cindex "environment for pipe transport"
21972 The environment variables listed below are set up when the command is invoked.
21973 This list is a compromise for maximum compatibility with other MTAs. Note that
21974 the &%environment%& option can be used to add additional variables to this
21975 environment.
21976 .display
21977 &`DOMAIN `& the domain of the address
21978 &`HOME `& the home directory, if set
21979 &`HOST `& the host name when called from a router (see below)
21980 &`LOCAL_PART `& see below
21981 &`LOCAL_PART_PREFIX `& see below
21982 &`LOCAL_PART_SUFFIX `& see below
21983 &`LOGNAME `& see below
21984 &`MESSAGE_ID `& Exim's local ID for the message
21985 &`PATH `& as specified by the &%path%& option below
21986 &`QUALIFY_DOMAIN `& the sender qualification domain
21987 &`RECIPIENT `& the complete recipient address
21988 &`SENDER `& the sender of the message (empty if a bounce)
21989 &`SHELL `& &`/bin/sh`&
21990 &`TZ `& the value of the &%timezone%& option, if set
21991 &`USER `& see below
21992 .endd
21993 When a &(pipe)& transport is called directly from (for example) an &(accept)&
21994 router, LOCAL_PART is set to the local part of the address. When it is
21995 called as a result of a forward or alias expansion, LOCAL_PART is set to
21996 the local part of the address that was expanded. In both cases, any affixes are
21997 removed from the local part, and made available in LOCAL_PART_PREFIX and
21998 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
21999 same value as LOCAL_PART for compatibility with other MTAs.
22000
22001 .cindex "HOST"
22002 HOST is set only when a &(pipe)& transport is called from a router that
22003 associates hosts with an address, typically when using &(pipe)& as a
22004 pseudo-remote transport. HOST is set to the first host name specified by
22005 the router.
22006
22007 .cindex "HOME"
22008 If the transport's generic &%home_directory%& option is set, its value is used
22009 for the HOME environment variable. Otherwise, a home directory may be set
22010 by the router's &%transport_home_directory%& option, which defaults to the
22011 user's home directory if &%check_local_user%& is set.
22012
22013
22014 .section "Private options for pipe" "SECID142"
22015 .cindex "options" "&(pipe)& transport"
22016
22017
22018
22019 .option allow_commands pipe "string list&!!" unset
22020 .cindex "&(pipe)& transport" "permitted commands"
22021 The string is expanded, and is then interpreted as a colon-separated list of
22022 permitted commands. If &%restrict_to_path%& is not set, the only commands
22023 permitted are those in the &%allow_commands%& list. They need not be absolute
22024 paths; the &%path%& option is still used for relative paths. If
22025 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
22026 in the &%allow_commands%& list, or a name without any slashes that is found on
22027 the path. In other words, if neither &%allow_commands%& nor
22028 &%restrict_to_path%& is set, there is no restriction on the command, but
22029 otherwise only commands that are permitted by one or the other are allowed. For
22030 example, if
22031 .code
22032 allow_commands = /usr/bin/vacation
22033 .endd
22034 and &%restrict_to_path%& is not set, the only permitted command is
22035 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
22036 &%use_shell%& is set.
22037
22038
22039 .option batch_id pipe string&!! unset
22040 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22041
22042
22043 .option batch_max pipe integer 1
22044 This limits the number of addresses that can be handled in a single delivery.
22045 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22046
22047
22048 .option check_string pipe string unset
22049 As &(pipe)& writes the message, the start of each line is tested for matching
22050 &%check_string%&, and if it does, the initial matching characters are replaced
22051 by the contents of &%escape_string%&, provided both are set. The value of
22052 &%check_string%& is a literal string, not a regular expression, and the case of
22053 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
22054 of &%check_string%& and &%escape_string%& are forced to values that implement
22055 the SMTP escaping protocol. Any settings made in the configuration file are
22056 ignored.
22057
22058
22059 .option command pipe string&!! unset
22060 This option need not be set when &(pipe)& is being used to deliver to pipes
22061 obtained directly from address redirections. In other cases, the option must be
22062 set, to provide a command to be run. It need not yield an absolute path (see
22063 the &%path%& option below). The command is split up into separate arguments by
22064 Exim, and each argument is separately expanded, as described in section
22065 &<<SECThowcommandrun>>& above.
22066
22067
22068 .option environment pipe string&!! unset
22069 .cindex "&(pipe)& transport" "environment for command"
22070 .cindex "environment for &(pipe)& transport"
22071 This option is used to add additional variables to the environment in which the
22072 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
22073 a string which is expanded, and then interpreted as a colon-separated list of
22074 environment settings of the form <&'name'&>=<&'value'&>.
22075
22076
22077 .option escape_string pipe string unset
22078 See &%check_string%& above.
22079
22080
22081 .option freeze_exec_fail pipe boolean false
22082 .cindex "exec failure"
22083 .cindex "failure of exec"
22084 .cindex "&(pipe)& transport" "failure of exec"
22085 Failure to exec the command in a pipe transport is by default treated like
22086 any other failure while running the command. However, if &%freeze_exec_fail%&
22087 is set, failure to exec is treated specially, and causes the message to be
22088 frozen, whatever the setting of &%ignore_status%&.
22089
22090
22091 .option freeze_signal pipe boolean false
22092 .cindex "signal exit"
22093 .cindex "&(pipe)& transport", "signal exit"
22094 Normally if the process run by a command in a pipe transport exits on a signal,
22095 a bounce message is sent. If &%freeze_signal%& is set, the message will be
22096 frozen in Exim's queue instead.
22097
22098
22099 .option force_command pipe boolean false
22100 .cindex "force command"
22101 .cindex "&(pipe)& transport", "force command"
22102 Normally when a router redirects an address directly to a pipe command
22103 the &%command%& option on the transport is ignored. If &%force_command%&
22104 is set, the &%command%& option will used. This is especially
22105 useful for forcing a wrapper or additional argument to be added to the
22106 command. For example:
22107 .code
22108 command = /usr/bin/remote_exec myhost -- $address_pipe
22109 force_command
22110 .endd
22111
22112 Note that &$address_pipe$& is handled specially in &%command%& when
22113 &%force_command%& is set, expanding out to the original argument vector as
22114 separate items, similarly to a Unix shell &`"$@"`& construct.
22115
22116 .option ignore_status pipe boolean false
22117 If this option is true, the status returned by the subprocess that is set up to
22118 run the command is ignored, and Exim behaves as if zero had been returned.
22119 Otherwise, a non-zero status or termination by signal causes an error return
22120 from the transport unless the status value is one of those listed in
22121 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
22122
22123 &*Note*&: This option does not apply to timeouts, which do not return a status.
22124 See the &%timeout_defer%& option for how timeouts are handled.
22125
22126 .option log_defer_output pipe boolean false
22127 .cindex "&(pipe)& transport" "logging output"
22128 If this option is set, and the status returned by the command is
22129 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
22130 and any output was produced, the first line of it is written to the main log.
22131
22132
22133 .option log_fail_output pipe boolean false
22134 If this option is set, and the command returns any output, and also ends with a
22135 return code that is neither zero nor one of the return codes listed in
22136 &%temp_errors%& (that is, the delivery failed), the first line of output is
22137 written to the main log. This option and &%log_output%& are mutually exclusive.
22138 Only one of them may be set.
22139
22140
22141
22142 .option log_output pipe boolean false
22143 If this option is set and the command returns any output, the first line of
22144 output is written to the main log, whatever the return code. This option and
22145 &%log_fail_output%& are mutually exclusive. Only one of them may be set.
22146
22147
22148
22149 .option max_output pipe integer 20K
22150 This specifies the maximum amount of output that the command may produce on its
22151 standard output and standard error file combined. If the limit is exceeded, the
22152 process running the command is killed. This is intended as a safety measure to
22153 catch runaway processes. The limit is applied independently of the settings of
22154 the options that control what is done with such output (for example,
22155 &%return_output%&). Because of buffering effects, the amount of output may
22156 exceed the limit by a small amount before Exim notices.
22157
22158
22159 .option message_prefix pipe string&!! "see below"
22160 The string specified here is expanded and output at the start of every message.
22161 The default is unset if &%use_bsmtp%& is set. Otherwise it is
22162 .code
22163 message_prefix = \
22164 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
22165 ${tod_bsdinbox}\n
22166 .endd
22167 .cindex "Cyrus"
22168 .cindex "&%tmail%&"
22169 .cindex "&""From""& line"
22170 This is required by the commonly used &_/usr/bin/vacation_& program.
22171 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
22172 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
22173 setting
22174 .code
22175 message_prefix =
22176 .endd
22177 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
22178 &`\n`& to &`\r\n`& in &%message_prefix%&.
22179
22180
22181 .option message_suffix pipe string&!! "see below"
22182 The string specified here is expanded and output at the end of every message.
22183 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
22184 The suffix can be suppressed by setting
22185 .code
22186 message_suffix =
22187 .endd
22188 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
22189 &`\n`& to &`\r\n`& in &%message_suffix%&.
22190
22191
22192 .option path pipe string "see below"
22193 This option specifies the string that is set up in the PATH environment
22194 variable of the subprocess. The default is:
22195 .code
22196 /bin:/usr/bin
22197 .endd
22198 If the &%command%& option does not yield an absolute path name, the command is
22199 sought in the PATH directories, in the usual way. &*Warning*&: This does not
22200 apply to a command specified as a transport filter.
22201
22202
22203 .option permit_coredump pipe boolean false
22204 Normally Exim inhibits core-dumps during delivery. If you have a need to get
22205 a core-dump of a pipe command, enable this command. This enables core-dumps
22206 during delivery and affects both the Exim binary and the pipe command run.
22207 It is recommended that this option remain off unless and until you have a need
22208 for it and that this only be enabled when needed, as the risk of excessive
22209 resource consumption can be quite high. Note also that Exim is typically
22210 installed as a setuid binary and most operating systems will inhibit coredumps
22211 of these by default, so further OS-specific action may be required.
22212
22213
22214 .option pipe_as_creator pipe boolean false
22215 .cindex "uid (user id)" "local delivery"
22216 If the generic &%user%& option is not set and this option is true, the delivery
22217 process is run under the uid that was in force when Exim was originally called
22218 to accept the message. If the group id is not otherwise set (via the generic
22219 &%group%& option), the gid that was in force when Exim was originally called to
22220 accept the message is used.
22221
22222
22223 .option restrict_to_path pipe boolean false
22224 When this option is set, any command name not listed in &%allow_commands%& must
22225 contain no slashes. The command is searched for only in the directories listed
22226 in the &%path%& option. This option is intended for use in the case when a pipe
22227 command has been generated from a user's &_.forward_& file. This is usually
22228 handled by a &(pipe)& transport called &%address_pipe%&.
22229
22230
22231 .option return_fail_output pipe boolean false
22232 If this option is true, and the command produced any output and ended with a
22233 return code other than zero or one of the codes listed in &%temp_errors%& (that
22234 is, the delivery failed), the output is returned in the bounce message.
22235 However, if the message has a null sender (that is, it is itself a bounce
22236 message), output from the command is discarded. This option and
22237 &%return_output%& are mutually exclusive. Only one of them may be set.
22238
22239
22240
22241 .option return_output pipe boolean false
22242 If this option is true, and the command produced any output, the delivery is
22243 deemed to have failed whatever the return code from the command, and the output
22244 is returned in the bounce message. Otherwise, the output is just discarded.
22245 However, if the message has a null sender (that is, it is a bounce message),
22246 output from the command is always discarded, whatever the setting of this
22247 option. This option and &%return_fail_output%& are mutually exclusive. Only one
22248 of them may be set.
22249
22250
22251
22252 .option temp_errors pipe "string list" "see below"
22253 .cindex "&(pipe)& transport" "temporary failure"
22254 This option contains either a colon-separated list of numbers, or a single
22255 asterisk. If &%ignore_status%& is false
22256 and &%return_output%& is not set,
22257 and the command exits with a non-zero return code, the failure is treated as
22258 temporary and the delivery is deferred if the return code matches one of the
22259 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
22260 codes are treated as permanent errors. The default setting contains the codes
22261 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
22262 compiled on a system that does not define these macros, it assumes values of 75
22263 and 73, respectively.
22264
22265
22266 .option timeout pipe time 1h
22267 If the command fails to complete within this time, it is killed. This normally
22268 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
22269 specifies no timeout. In order to ensure that any subprocesses created by the
22270 command are also killed, Exim makes the initial process a process group leader,
22271 and kills the whole process group on a timeout. However, this can be defeated
22272 if one of the processes starts a new process group.
22273
22274 .option timeout_defer pipe boolean false
22275 A timeout in a &(pipe)& transport, either in the command that the transport
22276 runs, or in a transport filter that is associated with it, is by default
22277 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
22278 is set true, both kinds of timeout become temporary errors, causing the
22279 delivery to be deferred.
22280
22281 .option umask pipe "octal integer" 022
22282 This specifies the umask setting for the subprocess that runs the command.
22283
22284
22285 .option use_bsmtp pipe boolean false
22286 .cindex "envelope sender"
22287 If this option is set true, the &(pipe)& transport writes messages in &"batch
22288 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
22289 commands. If you want to include a leading HELO command with such messages,
22290 you can do so by setting the &%message_prefix%& option. See section
22291 &<<SECTbatchSMTP>>& for details of batch SMTP.
22292
22293 .option use_classresources pipe boolean false
22294 .cindex "class resources (BSD)"
22295 This option is available only when Exim is running on FreeBSD, NetBSD, or
22296 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
22297 resource limits when a &(pipe)& transport is run to perform a delivery. The
22298 limits for the uid under which the pipe is to run are obtained from the login
22299 class database.
22300
22301
22302 .option use_crlf pipe boolean false
22303 .cindex "carriage return"
22304 .cindex "linefeed"
22305 This option causes lines to be terminated with the two-character CRLF sequence
22306 (carriage return, linefeed) instead of just a linefeed character. In the case
22307 of batched SMTP, the byte sequence written to the pipe is then an exact image
22308 of what would be sent down a real SMTP connection.
22309
22310 The contents of the &%message_prefix%& and &%message_suffix%& options are
22311 written verbatim, so must contain their own carriage return characters if these
22312 are needed. When &%use_bsmtp%& is not set, the default values for both
22313 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
22314 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
22315
22316
22317 .option use_shell pipe boolean false
22318 .vindex "&$pipe_addresses$&"
22319 If this option is set, it causes the command to be passed to &_/bin/sh_&
22320 instead of being run directly from the transport, as described in section
22321 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
22322 where the command is expected to be run under a shell and cannot easily be
22323 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
22324 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
22325 command is expanded as a single string, and handed to &_/bin/sh_& as data for
22326 its &%-c%& option.
22327
22328
22329
22330 .section "Using an external local delivery agent" "SECID143"
22331 .cindex "local delivery" "using an external agent"
22332 .cindex "&'procmail'&"
22333 .cindex "external local delivery"
22334 .cindex "delivery" "&'procmail'&"
22335 .cindex "delivery" "by external agent"
22336 The &(pipe)& transport can be used to pass all messages that require local
22337 delivery to a separate local delivery agent such as &%procmail%&. When doing
22338 this, care must be taken to ensure that the pipe is run under an appropriate
22339 uid and gid. In some configurations one wants this to be a uid that is trusted
22340 by the delivery agent to supply the correct sender of the message. It may be
22341 necessary to recompile or reconfigure the delivery agent so that it trusts an
22342 appropriate user. The following is an example transport and router
22343 configuration for &%procmail%&:
22344 .code
22345 # transport
22346 procmail_pipe:
22347 driver = pipe
22348 command = /usr/local/bin/procmail -d $local_part
22349 return_path_add
22350 delivery_date_add
22351 envelope_to_add
22352 check_string = "From "
22353 escape_string = ">From "
22354 umask = 077
22355 user = $local_part
22356 group = mail
22357
22358 # router
22359 procmail:
22360 driver = accept
22361 check_local_user
22362 transport = procmail_pipe
22363 .endd
22364 In this example, the pipe is run as the local user, but with the group set to
22365 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
22366 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
22367 user to supply a correct sender address. If you do not specify either a
22368 &%group%& or a &%user%& option, the pipe command is run as the local user. The
22369 home directory is the user's home directory by default.
22370
22371 &*Note*&: The command that the pipe transport runs does &'not'& begin with
22372 .code
22373 IFS=" "
22374 .endd
22375 as shown in some &%procmail%& documentation, because Exim does not by default
22376 use a shell to run pipe commands.
22377
22378 .cindex "Cyrus"
22379 The next example shows a transport and a router for a system where local
22380 deliveries are handled by the Cyrus IMAP server.
22381 .code
22382 # transport
22383 local_delivery_cyrus:
22384 driver = pipe
22385 command = /usr/cyrus/bin/deliver \
22386 -m ${substr_1:$local_part_suffix} -- $local_part
22387 user = cyrus
22388 group = mail
22389 return_output
22390 log_output
22391 message_prefix =
22392 message_suffix =
22393
22394 # router
22395 local_user_cyrus:
22396 driver = accept
22397 check_local_user
22398 local_part_suffix = .*
22399 transport = local_delivery_cyrus
22400 .endd
22401 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
22402 &%return_output%& to cause any text written by Cyrus to be returned to the
22403 sender.
22404 .ecindex IIDpiptra1
22405 .ecindex IIDpiptra2
22406
22407
22408 . ////////////////////////////////////////////////////////////////////////////
22409 . ////////////////////////////////////////////////////////////////////////////
22410
22411 .chapter "The smtp transport" "CHAPsmtptrans"
22412 .scindex IIDsmttra1 "transports" "&(smtp)&"
22413 .scindex IIDsmttra2 "&(smtp)& transport"
22414 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
22415 or LMTP protocol. The list of hosts to try can either be taken from the address
22416 that is being processed (having been set up by the router), or specified
22417 explicitly for the transport. Timeout and retry processing (see chapter
22418 &<<CHAPretry>>&) is applied to each IP address independently.
22419
22420
22421 .section "Multiple messages on a single connection" "SECID144"
22422 The sending of multiple messages over a single TCP/IP connection can arise in
22423 two ways:
22424
22425 .ilist
22426 If a message contains more than &%max_rcpt%& (see below) addresses that are
22427 routed to the same host, more than one copy of the message has to be sent to
22428 that host. In this situation, multiple copies may be sent in a single run of
22429 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
22430 does when it has too many addresses to send in one message also depends on the
22431 value of the global &%remote_max_parallel%& option. Details are given in
22432 section &<<SECToutSMTPTCP>>&.)
22433 .next
22434 .cindex "hints database" "remembering routing"
22435 When a message has been successfully delivered over a TCP/IP connection, Exim
22436 looks in its hints database to see if there are any other messages awaiting a
22437 connection to the same host. If there are, a new delivery process is started
22438 for one of them, and the current TCP/IP connection is passed on to it. The new
22439 process may in turn send multiple copies and possibly create yet another
22440 process.
22441 .endlist
22442
22443
22444 For each copy sent over the same TCP/IP connection, a sequence counter is
22445 incremented, and if it ever gets to the value of &%connection_max_messages%&,
22446 no further messages are sent over that connection.
22447
22448
22449
22450 .section "Use of the $host and $host_address variables" "SECID145"
22451 .vindex "&$host$&"
22452 .vindex "&$host_address$&"
22453 At the start of a run of the &(smtp)& transport, the values of &$host$& and
22454 &$host_address$& are the name and IP address of the first host on the host list
22455 passed by the router. However, when the transport is about to connect to a
22456 specific host, and while it is connected to that host, &$host$& and
22457 &$host_address$& are set to the values for that host. These are the values
22458 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
22459 &%serialize_hosts%&, and the various TLS options are expanded.
22460
22461
22462 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
22463 .vindex &$tls_bits$&
22464 .vindex &$tls_cipher$&
22465 .vindex &$tls_peerdn$&
22466 .vindex &$tls_sni$&
22467 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
22468 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
22469 are the values that were set when the message was received.
22470 These are the values that are used for options that are expanded before any
22471 SMTP connections are made. Just before each connection is made, these four
22472 variables are emptied. If TLS is subsequently started, they are set to the
22473 appropriate values for the outgoing connection, and these are the values that
22474 are in force when any authenticators are run and when the
22475 &%authenticated_sender%& option is expanded.
22476
22477 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
22478 and will be removed in a future release.
22479
22480
22481 .section "Private options for smtp" "SECID146"
22482 .cindex "options" "&(smtp)& transport"
22483 The private options of the &(smtp)& transport are as follows:
22484
22485
22486 .option address_retry_include_sender smtp boolean true
22487 .cindex "4&'xx'& responses" "retrying after"
22488 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
22489 is the combination of sender and recipient that is delayed in subsequent queue
22490 runs until the retry time is reached. You can delay the recipient without
22491 reference to the sender (which is what earlier versions of Exim did), by
22492 setting &%address_retry_include_sender%& false. However, this can lead to
22493 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
22494
22495 .option allow_localhost smtp boolean false
22496 .cindex "local host" "sending to"
22497 .cindex "fallback" "hosts specified on transport"
22498 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
22499 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
22500 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
22501 the delivery anyway. This should be used only in special cases when the
22502 configuration ensures that no looping will result (for example, a differently
22503 configured Exim is listening on the port to which the message is sent).
22504
22505
22506 .option authenticated_sender smtp string&!! unset
22507 .cindex "Cyrus"
22508 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
22509 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
22510 overriding any existing authenticated sender value. If the string expansion is
22511 forced to fail, the option is ignored. Other expansion failures cause delivery
22512 to be deferred. If the result of expansion is an empty string, that is also
22513 ignored.
22514
22515 The expansion happens after the outgoing connection has been made and TLS
22516 started, if required. This means that the &$host$&, &$host_address$&,
22517 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
22518 particular connection.
22519
22520 If the SMTP session is not authenticated, the expansion of
22521 &%authenticated_sender%& still happens (and can cause the delivery to be
22522 deferred if it fails), but no AUTH= item is added to MAIL commands
22523 unless &%authenticated_sender_force%& is true.
22524
22525 This option allows you to use the &(smtp)& transport in LMTP mode to
22526 deliver mail to Cyrus IMAP and provide the proper local part as the
22527 &"authenticated sender"&, via a setting such as:
22528 .code
22529 authenticated_sender = $local_part
22530 .endd
22531 This removes the need for IMAP subfolders to be assigned special ACLs to
22532 allow direct delivery to those subfolders.
22533
22534 Because of expected uses such as that just described for Cyrus (when no
22535 domain is involved), there is no checking on the syntax of the provided
22536 value.
22537
22538
22539 .option authenticated_sender_force smtp boolean false
22540 If this option is set true, the &%authenticated_sender%& option's value
22541 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
22542 authenticated as a client.
22543
22544
22545 .option command_timeout smtp time 5m
22546 This sets a timeout for receiving a response to an SMTP command that has been
22547 sent out. It is also used when waiting for the initial banner line from the
22548 remote host. Its value must not be zero.
22549
22550
22551 .option connect_timeout smtp time 5m
22552 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
22553 to a remote host. A setting of zero allows the system timeout (typically
22554 several minutes) to act. To have any effect, the value of this option must be
22555 less than the system timeout. However, it has been observed that on some
22556 systems there is no system timeout, which is why the default value for this
22557 option is 5 minutes, a value recommended by RFC 1123.
22558
22559
22560 .option connection_max_messages smtp integer 500
22561 .cindex "SMTP" "passed connection"
22562 .cindex "SMTP" "multiple deliveries"
22563 .cindex "multiple SMTP deliveries"
22564 This controls the maximum number of separate message deliveries that are sent
22565 over a single TCP/IP connection. If the value is zero, there is no limit.
22566 For testing purposes, this value can be overridden by the &%-oB%& command line
22567 option.
22568
22569
22570 .option data_timeout smtp time 5m
22571 This sets a timeout for the transmission of each block in the data portion of
22572 the message. As a result, the overall timeout for a message depends on the size
22573 of the message. Its value must not be zero. See also &%final_timeout%&.
22574
22575
22576 .option delay_after_cutoff smtp boolean true
22577 This option controls what happens when all remote IP addresses for a given
22578 domain have been inaccessible for so long that they have passed their retry
22579 cutoff times.
22580
22581 In the default state, if the next retry time has not been reached for any of
22582 them, the address is bounced without trying any deliveries. In other words,
22583 Exim delays retrying an IP address after the final cutoff time until a new
22584 retry time is reached, and can therefore bounce an address without ever trying
22585 a delivery, when machines have been down for a long time. Some people are
22586 unhappy at this prospect, so...
22587
22588 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
22589 addresses are past their final cutoff time, Exim tries to deliver to those
22590 IP addresses that have not been tried since the message arrived. If there are
22591 none, of if they all fail, the address is bounced. In other words, it does not
22592 delay when a new message arrives, but immediately tries those expired IP
22593 addresses that haven't been tried since the message arrived. If there is a
22594 continuous stream of messages for the dead hosts, unsetting
22595 &%delay_after_cutoff%& means that there will be many more attempts to deliver
22596 to them.
22597
22598
22599 .option dns_qualify_single smtp boolean true
22600 If the &%hosts%& or &%fallback_hosts%& option is being used,
22601 and the &%gethostbyname%& option is false,
22602 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
22603 in chapter &<<CHAPdnslookup>>& for more details.
22604
22605
22606 .option dns_search_parents smtp boolean false
22607 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
22608 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
22609 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
22610 details.
22611
22612
22613 .option dscp smtp string&!! unset
22614 .cindex "DCSP" "outbound"
22615 This option causes the DSCP value associated with a socket to be set to one
22616 of a number of fixed strings or to numeric value.
22617 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
22618 Common values include &`throughput`&, &`mincost`&, and on newer systems
22619 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
22620
22621 The outbound packets from Exim will be marked with this value in the header
22622 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
22623 that these values will have any effect, not be stripped by networking
22624 equipment, or do much of anything without cooperation with your Network
22625 Engineer and those of all network operators between the source and destination.
22626
22627
22628 .option fallback_hosts smtp "string list" unset
22629 .cindex "fallback" "hosts specified on transport"
22630 String expansion is not applied to this option. The argument must be a
22631 colon-separated list of host names or IP addresses, optionally also including
22632 port numbers, though the separator can be changed, as described in section
22633 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
22634 item in a &%route_list%& setting for the &(manualroute)& router, as described
22635 in section &<<SECTformatonehostitem>>&.
22636
22637 Fallback hosts can also be specified on routers, which associate them with the
22638 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
22639 &%fallback_hosts%& specified on the transport is used only if the address does
22640 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
22641 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
22642 However, &%hosts_randomize%& does apply to fallback host lists.
22643
22644 If Exim is unable to deliver to any of the hosts for a particular address, and
22645 the errors are not permanent rejections, the address is put on a separate
22646 transport queue with its host list replaced by the fallback hosts, unless the
22647 address was routed via MX records and the current host was in the original MX
22648 list. In that situation, the fallback host list is not used.
22649
22650 Once normal deliveries are complete, the fallback queue is delivered by
22651 re-running the same transports with the new host lists. If several failing
22652 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
22653 copy of the message is sent.
22654
22655 The resolution of the host names on the fallback list is controlled by the
22656 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
22657 both to cases when the host list comes with the address and when it is taken
22658 from &%hosts%&. This option provides a &"use a smart host only if delivery
22659 fails"& facility.
22660
22661
22662 .option final_timeout smtp time 10m
22663 This is the timeout that applies while waiting for the response to the final
22664 line containing just &"."& that terminates a message. Its value must not be
22665 zero.
22666
22667 .option gethostbyname smtp boolean false
22668 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
22669 being used, names are looked up using &[gethostbyname()]&
22670 (or &[getipnodebyname()]& when available)
22671 instead of using the DNS. Of course, that function may in fact use the DNS, but
22672 it may also consult other sources of information such as &_/etc/hosts_&.
22673
22674 .option gnutls_compat_mode smtp boolean unset
22675 This option controls whether GnuTLS is used in compatibility mode in an Exim
22676 server. This reduces security slightly, but improves interworking with older
22677 implementations of TLS.
22678
22679 .option helo_data smtp string&!! "see below"
22680 .cindex "HELO" "argument, setting"
22681 .cindex "EHLO" "argument, setting"
22682 .cindex "LHLO argument setting"
22683 The value of this option is expanded after a connection to a another host has
22684 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
22685 command that starts the outgoing SMTP or LMTP session. The default value of the
22686 option is:
22687 .code
22688 $primary_hostname
22689 .endd
22690 During the expansion, the variables &$host$& and &$host_address$& are set to
22691 the identity of the remote host, and the variables &$sending_ip_address$& and
22692 &$sending_port$& are set to the local IP address and port number that are being
22693 used. These variables can be used to generate different values for different
22694 servers or different local IP addresses. For example, if you want the string
22695 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
22696 interface address, you could use this:
22697 .code
22698 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
22699 {$primary_hostname}}
22700 .endd
22701 The use of &%helo_data%& applies both to sending messages and when doing
22702 callouts.
22703
22704 .option hosts smtp "string list&!!" unset
22705 Hosts are associated with an address by a router such as &(dnslookup)&, which
22706 finds the hosts by looking up the address domain in the DNS, or by
22707 &(manualroute)&, which has lists of hosts in its configuration. However,
22708 email addresses can be passed to the &(smtp)& transport by any router, and not
22709 all of them can provide an associated list of hosts.
22710
22711 The &%hosts%& option specifies a list of hosts to be used if the address being
22712 processed does not have any hosts associated with it. The hosts specified by
22713 &%hosts%& are also used, whether or not the address has its own hosts, if
22714 &%hosts_override%& is set.
22715
22716 The string is first expanded, before being interpreted as a colon-separated
22717 list of host names or IP addresses, possibly including port numbers. The
22718 separator may be changed to something other than colon, as described in section
22719 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
22720 item in a &%route_list%& setting for the &(manualroute)& router, as described
22721 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
22722 of the &(manualroute)& router is not available here.
22723
22724 If the expansion fails, delivery is deferred. Unless the failure was caused by
22725 the inability to complete a lookup, the error is logged to the panic log as
22726 well as the main log. Host names are looked up either by searching directly for
22727 address records in the DNS or by calling &[gethostbyname()]& (or
22728 &[getipnodebyname()]& when available), depending on the setting of the
22729 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
22730 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
22731 address are used.
22732
22733 During delivery, the hosts are tried in order, subject to their retry status,
22734 unless &%hosts_randomize%& is set.
22735
22736
22737 .option hosts_avoid_esmtp smtp "host list&!!" unset
22738 .cindex "ESMTP, avoiding use of"
22739 .cindex "HELO" "forcing use of"
22740 .cindex "EHLO" "avoiding use of"
22741 .cindex "PIPELINING" "avoiding the use of"
22742 This option is for use with broken hosts that announce ESMTP facilities (for
22743 example, PIPELINING) and then fail to implement them properly. When a host
22744 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
22745 start of the SMTP session. This means that it cannot use any of the ESMTP
22746 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
22747
22748
22749 .option hosts_avoid_pipelining smtp "host list&!!" unset
22750 .cindex "PIPELINING" "avoiding the use of"
22751 Exim will not use the SMTP PIPELINING extension when delivering to any host
22752 that matches this list, even if the server host advertises PIPELINING support.
22753
22754
22755 .option hosts_avoid_tls smtp "host list&!!" unset
22756 .cindex "TLS" "avoiding for certain hosts"
22757 Exim will not try to start a TLS session when delivering to any host that
22758 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
22759
22760 .option hosts_verify_avoid_tls smtp "host list&!!" *
22761 .cindex "TLS" "avoiding for certain hosts"
22762 Exim will not try to start a TLS session for a verify callout,
22763 or when delivering in cutthrough mode,
22764 to any host that matches this list.
22765 Note that the default is to not use TLS.
22766
22767
22768 .option hosts_max_try smtp integer 5
22769 .cindex "host" "maximum number to try"
22770 .cindex "limit" "number of hosts tried"
22771 .cindex "limit" "number of MX tried"
22772 .cindex "MX record" "maximum tried"
22773 This option limits the number of IP addresses that are tried for any one
22774 delivery in cases where there are temporary delivery errors. Section
22775 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
22776
22777
22778 .option hosts_max_try_hardlimit smtp integer 50
22779 This is an additional check on the maximum number of IP addresses that Exim
22780 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
22781 why it exists.
22782
22783
22784
22785 .option hosts_nopass_tls smtp "host list&!!" unset
22786 .cindex "TLS" "passing connection"
22787 .cindex "multiple SMTP deliveries"
22788 .cindex "TLS" "multiple message deliveries"
22789 For any host that matches this list, a connection on which a TLS session has
22790 been started will not be passed to a new delivery process for sending another
22791 message on the same connection. See section &<<SECTmulmessam>>& for an
22792 explanation of when this might be needed.
22793
22794
22795 .option hosts_override smtp boolean false
22796 If this option is set and the &%hosts%& option is also set, any hosts that are
22797 attached to the address are ignored, and instead the hosts specified by the
22798 &%hosts%& option are always used. This option does not apply to
22799 &%fallback_hosts%&.
22800
22801
22802 .option hosts_randomize smtp boolean false
22803 .cindex "randomized host list"
22804 .cindex "host" "list of; randomized"
22805 .cindex "fallback" "randomized hosts"
22806 If this option is set, and either the list of hosts is taken from the
22807 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
22808 were not obtained from MX records (this includes fallback hosts from the
22809 router), and were not randomized by the router, the order of trying the hosts
22810 is randomized each time the transport runs. Randomizing the order of a host
22811 list can be used to do crude load sharing.
22812
22813 When &%hosts_randomize%& is true, a host list may be split into groups whose
22814 order is separately randomized. This makes it possible to set up MX-like
22815 behaviour. The boundaries between groups are indicated by an item that is just
22816 &`+`& in the host list. For example:
22817 .code
22818 hosts = host1:host2:host3:+:host4:host5
22819 .endd
22820 The order of the first three hosts and the order of the last two hosts is
22821 randomized for each use, but the first three always end up before the last two.
22822 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
22823
22824 .option hosts_require_auth smtp "host list&!!" unset
22825 .cindex "authentication" "required by client"
22826 This option provides a list of servers for which authentication must succeed
22827 before Exim will try to transfer a message. If authentication fails for
22828 servers which are not in this list, Exim tries to send unauthenticated. If
22829 authentication fails for one of these servers, delivery is deferred. This
22830 temporary error is detectable in the retry rules, so it can be turned into a
22831 hard failure if required. See also &%hosts_try_auth%&, and chapter
22832 &<<CHAPSMTPAUTH>>& for details of authentication.
22833
22834
22835 .option hosts_require_tls smtp "host list&!!" unset
22836 .cindex "TLS" "requiring for certain servers"
22837 Exim will insist on using a TLS session when delivering to any host that
22838 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
22839 &*Note*&: This option affects outgoing mail only. To insist on TLS for
22840 incoming messages, use an appropriate ACL.
22841
22842 .option hosts_try_auth smtp "host list&!!" unset
22843 .cindex "authentication" "optional in client"
22844 This option provides a list of servers to which, provided they announce
22845 authentication support, Exim will attempt to authenticate as a client when it
22846 connects. If authentication fails, Exim will try to transfer the message
22847 unauthenticated. See also &%hosts_require_auth%&, and chapter
22848 &<<CHAPSMTPAUTH>>& for details of authentication.
22849
22850 .option interface smtp "string list&!!" unset
22851 .cindex "bind IP address"
22852 .cindex "IP address" "binding"
22853 .vindex "&$host$&"
22854 .vindex "&$host_address$&"
22855 This option specifies which interface to bind to when making an outgoing SMTP
22856 call. The value is an IP address, not an interface name such as
22857 &`eth0`&. Do not confuse this with the interface address that was used when a
22858 message was received, which is in &$received_ip_address$&, formerly known as
22859 &$interface_address$&. The name was changed to minimize confusion with the
22860 outgoing interface address. There is no variable that contains an outgoing
22861 interface address because, unless it is set by this option, its value is
22862 unknown.
22863
22864 During the expansion of the &%interface%& option the variables &$host$& and
22865 &$host_address$& refer to the host to which a connection is about to be made
22866 during the expansion of the string. Forced expansion failure, or an empty
22867 string result causes the option to be ignored. Otherwise, after expansion, the
22868 string must be a list of IP addresses, colon-separated by default, but the
22869 separator can be changed in the usual way. For example:
22870 .code
22871 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
22872 .endd
22873 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
22874 connection. If none of them are the correct type, the option is ignored. If
22875 &%interface%& is not set, or is ignored, the system's IP functions choose which
22876 interface to use if the host has more than one.
22877
22878
22879 .option keepalive smtp boolean true
22880 .cindex "keepalive" "on outgoing connection"
22881 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
22882 connections. When set, it causes the kernel to probe idle connections
22883 periodically, by sending packets with &"old"& sequence numbers. The other end
22884 of the connection should send a acknowledgment if the connection is still okay
22885 or a reset if the connection has been aborted. The reason for doing this is
22886 that it has the beneficial effect of freeing up certain types of connection
22887 that can get stuck when the remote host is disconnected without tidying up the
22888 TCP/IP call properly. The keepalive mechanism takes several hours to detect
22889 unreachable hosts.
22890
22891
22892 .option lmtp_ignore_quota smtp boolean false
22893 .cindex "LMTP" "ignoring quota errors"
22894 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
22895 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
22896 has advertised support for IGNOREQUOTA in its response to the LHLO command.
22897
22898 .option max_rcpt smtp integer 100
22899 .cindex "RCPT" "maximum number of outgoing"
22900 This option limits the number of RCPT commands that are sent in a single
22901 SMTP message transaction. Each set of addresses is treated independently, and
22902 so can cause parallel connections to the same host if &%remote_max_parallel%&
22903 permits this.
22904
22905
22906 .option multi_domain smtp boolean true
22907 .vindex "&$domain$&"
22908 When this option is set, the &(smtp)& transport can handle a number of
22909 addresses containing a mixture of different domains provided they all resolve
22910 to the same list of hosts. Turning the option off restricts the transport to
22911 handling only one domain at a time. This is useful if you want to use
22912 &$domain$& in an expansion for the transport, because it is set only when there
22913 is a single domain involved in a remote delivery.
22914
22915
22916 .option port smtp string&!! "see below"
22917 .cindex "port" "sending TCP/IP"
22918 .cindex "TCP/IP" "setting outgoing port"
22919 This option specifies the TCP/IP port on the server to which Exim connects.
22920 &*Note:*& Do not confuse this with the port that was used when a message was
22921 received, which is in &$received_port$&, formerly known as &$interface_port$&.
22922 The name was changed to minimize confusion with the outgoing port. There is no
22923 variable that contains an outgoing port.
22924
22925 If the value of this option begins with a digit it is taken as a port number;
22926 otherwise it is looked up using &[getservbyname()]&. The default value is
22927 normally &"smtp"&, but if &%protocol%& is set to &"lmtp"&, the default is
22928 &"lmtp"&. If the expansion fails, or if a port number cannot be found, delivery
22929 is deferred.
22930
22931
22932
22933 .option protocol smtp string smtp
22934 .cindex "LMTP" "over TCP/IP"
22935 .cindex "ssmtp protocol" "outbound"
22936 .cindex "TLS" "SSL-on-connect outbound"
22937 .vindex "&$port$&"
22938 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
22939 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
22940 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
22941 deliveries into closed message stores. Exim also has support for running LMTP
22942 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
22943
22944 If this option is set to &"smtps"&, the default vaule for the &%port%& option
22945 changes to &"smtps"&, and the transport initiates TLS immediately after
22946 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
22947 The Internet standards bodies strongly discourage use of this mode.
22948
22949
22950 .option retry_include_ip_address smtp boolean true
22951 Exim normally includes both the host name and the IP address in the key it
22952 constructs for indexing retry data after a temporary delivery failure. This
22953 means that when one of several IP addresses for a host is failing, it gets
22954 tried periodically (controlled by the retry rules), but use of the other IP
22955 addresses is not affected.
22956
22957 However, in some dialup environments hosts are assigned a different IP address
22958 each time they connect. In this situation the use of the IP address as part of
22959 the retry key leads to undesirable behaviour. Setting this option false causes
22960 Exim to use only the host name. This should normally be done on a separate
22961 instance of the &(smtp)& transport, set up specially to handle the dialup
22962 hosts.
22963
22964
22965 .option serialize_hosts smtp "host list&!!" unset
22966 .cindex "serializing connections"
22967 .cindex "host" "serializing connections"
22968 Because Exim operates in a distributed manner, if several messages for the same
22969 host arrive at around the same time, more than one simultaneous connection to
22970 the remote host can occur. This is not usually a problem except when there is a
22971 slow link between the hosts. In that situation it may be helpful to restrict
22972 Exim to one connection at a time. This can be done by setting
22973 &%serialize_hosts%& to match the relevant hosts.
22974
22975 .cindex "hints database" "serializing deliveries to a host"
22976 Exim implements serialization by means of a hints database in which a record is
22977 written whenever a process connects to one of the restricted hosts. The record
22978 is deleted when the connection is completed. Obviously there is scope for
22979 records to get left lying around if there is a system or program crash. To
22980 guard against this, Exim ignores any records that are more than six hours old.
22981
22982 If you set up this kind of serialization, you should also arrange to delete the
22983 relevant hints database whenever your system reboots. The names of the files
22984 start with &_misc_& and they are kept in the &_spool/db_& directory. There
22985 may be one or two files, depending on the type of DBM in use. The same files
22986 are used for ETRN serialization.
22987
22988
22989 .option size_addition smtp integer 1024
22990 .cindex "SMTP" "SIZE"
22991 .cindex "message" "size issue for transport filter"
22992 .cindex "size" "of message"
22993 .cindex "transport" "filter"
22994 .cindex "filter" "transport filter"
22995 If a remote SMTP server indicates that it supports the SIZE option of the
22996 MAIL command, Exim uses this to pass over the message size at the start of
22997 an SMTP transaction. It adds the value of &%size_addition%& to the value it
22998 sends, to allow for headers and other text that may be added during delivery by
22999 configuration options or in a transport filter. It may be necessary to increase
23000 this if a lot of text is added to messages.
23001
23002 Alternatively, if the value of &%size_addition%& is set negative, it disables
23003 the use of the SIZE option altogether.
23004
23005
23006 .option tls_certificate smtp string&!! unset
23007 .cindex "TLS" "client certificate, location of"
23008 .cindex "certificate" "client, location of"
23009 .vindex "&$host$&"
23010 .vindex "&$host_address$&"
23011 The value of this option must be the absolute path to a file which contains the
23012 client's certificate, for possible use when sending a message over an encrypted
23013 connection. The values of &$host$& and &$host_address$& are set to the name and
23014 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
23015 details of TLS.
23016
23017 &*Note*&: This option must be set if you want Exim to be able to use a TLS
23018 certificate when sending messages as a client. The global option of the same
23019 name specifies the certificate for Exim as a server; it is not automatically
23020 assumed that the same certificate should be used when Exim is operating as a
23021 client.
23022
23023
23024 .option tls_crl smtp string&!! unset
23025 .cindex "TLS" "client certificate revocation list"
23026 .cindex "certificate" "revocation list for client"
23027 This option specifies a certificate revocation list. The expanded value must
23028 be the name of a file that contains a CRL in PEM format.
23029
23030
23031 .option tls_dh_min_bits smtp integer 1024
23032 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
23033 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
23034 key agreement is negotiated, the server will provide a large prime number
23035 for use. This option establishes the minimum acceptable size of that number.
23036 If the parameter offered by the server is too small, then the TLS handshake
23037 will fail.
23038
23039 Only supported when using GnuTLS.
23040
23041
23042 .option tls_privatekey smtp string&!! unset
23043 .cindex "TLS" "client private key, location of"
23044 .vindex "&$host$&"
23045 .vindex "&$host_address$&"
23046 The value of this option must be the absolute path to a file which contains the
23047 client's private key. This is used when sending a message over an encrypted
23048 connection using a client certificate. The values of &$host$& and
23049 &$host_address$& are set to the name and address of the server during the
23050 expansion. If this option is unset, or the expansion is forced to fail, or the
23051 result is an empty string, the private key is assumed to be in the same file as
23052 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
23053
23054
23055 .option tls_require_ciphers smtp string&!! unset
23056 .cindex "TLS" "requiring specific ciphers"
23057 .cindex "cipher" "requiring specific"
23058 .vindex "&$host$&"
23059 .vindex "&$host_address$&"
23060 The value of this option must be a list of permitted cipher suites, for use
23061 when setting up an outgoing encrypted connection. (There is a global option of
23062 the same name for controlling incoming connections.) The values of &$host$& and
23063 &$host_address$& are set to the name and address of the server during the
23064 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
23065 is used in different ways by OpenSSL and GnuTLS (see sections
23066 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
23067 ciphers is a preference order.
23068
23069
23070
23071 .option tls_sni smtp string&!! unset
23072 .cindex "TLS" "Server Name Indication"
23073 .vindex "&$tls_sni$&"
23074 If this option is set then it sets the $tls_out_sni variable and causes any
23075 TLS session to pass this value as the Server Name Indication extension to
23076 the remote side, which can be used by the remote side to select an appropriate
23077 certificate and private key for the session.
23078
23079 See &<<SECTtlssni>>& for more information.
23080
23081 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
23082 TLS extensions.
23083
23084
23085
23086
23087 .option tls_tempfail_tryclear smtp boolean true
23088 .cindex "4&'xx'& responses" "to STARTTLS"
23089 When the server host is not in &%hosts_require_tls%&, and there is a problem in
23090 setting up a TLS session, this option determines whether or not Exim should try
23091 to deliver the message unencrypted. If it is set false, delivery to the
23092 current host is deferred; if there are other hosts, they are tried. If this
23093 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
23094 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
23095 TLS negotiation fails, Exim closes the current connection (because it is in an
23096 unknown state), opens a new one to the same host, and then tries the delivery
23097 in clear.
23098
23099
23100 .option tls_try_verify_hosts smtp "host list&!! unset
23101 .cindex "TLS" "server certificate verification"
23102 .cindex "certificate" "verification of server"
23103 This option gives a list of hosts for which, on encrypted connections,
23104 certificate verification will be tried but need not succeed.
23105 The &%tls_verify_certificates%& option must also be set.
23106
23107
23108 .option tls_verify_certificates smtp string&!! unset
23109 .cindex "TLS" "server certificate verification"
23110 .cindex "certificate" "verification of server"
23111 .vindex "&$host$&"
23112 .vindex "&$host_address$&"
23113 The value of this option must be the absolute path to a file containing
23114 permitted server certificates, for use when setting up an encrypted connection.
23115 Alternatively, if you are using OpenSSL, you can set
23116 &%tls_verify_certificates%& to the name of a directory containing certificate
23117 files. This does not work with GnuTLS; the option must be set to the name of a
23118 single file if you are using GnuTLS. The values of &$host$& and
23119 &$host_address$& are set to the name and address of the server during the
23120 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
23121
23122 For back-compatability,
23123 if neither tls_verify_hosts nor tls_try_verify_hosts are set
23124 and certificate verification fails the TLS connection is closed.
23125
23126
23127 .option tls_verify_hosts smtp "host list&!! unset
23128 .cindex "TLS" "server certificate verification"
23129 .cindex "certificate" "verification of server"
23130 This option gives a list of hosts for which. on encrypted connections,
23131 certificate verification must succeed.
23132 The &%tls_verify_certificates%& option must also be set.
23133 If both this option and &%tls_try_verify_hosts%& are unset
23134 operation is as if this option selected all hosts.
23135
23136
23137
23138
23139 .section "How the limits for the number of hosts to try are used" &&&
23140 "SECTvalhosmax"
23141 .cindex "host" "maximum number to try"
23142 .cindex "limit" "hosts; maximum number tried"
23143 There are two options that are concerned with the number of hosts that are
23144 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
23145 &%hosts_max_try_hardlimit%&.
23146
23147
23148 The &%hosts_max_try%& option limits the number of hosts that are tried
23149 for a single delivery. However, despite the term &"host"& in its name, the
23150 option actually applies to each IP address independently. In other words, a
23151 multihomed host is treated as several independent hosts, just as it is for
23152 retrying.
23153
23154 Many of the larger ISPs have multiple MX records which often point to
23155 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
23156 created as a result of routing one of these domains.
23157
23158 Trying every single IP address on such a long list does not seem sensible; if
23159 several at the top of the list fail, it is reasonable to assume there is some
23160 problem that is likely to affect all of them. Roughly speaking, the value of
23161 &%hosts_max_try%& is the maximum number that are tried before deferring the
23162 delivery. However, the logic cannot be quite that simple.
23163
23164 Firstly, IP addresses that are skipped because their retry times have not
23165 arrived do not count, and in addition, addresses that are past their retry
23166 limits are also not counted, even when they are tried. This means that when
23167 some IP addresses are past their retry limits, more than the value of
23168 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
23169 that all IP addresses are considered before timing out an email address (but
23170 see below for an exception).
23171
23172 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
23173 list to see if there is a subsequent host with a different (higher valued) MX.
23174 If there is, that host is considered next, and the current IP address is used
23175 but not counted. This behaviour helps in the case of a domain with a retry rule
23176 that hardly ever delays any hosts, as is now explained:
23177
23178 Consider the case of a long list of hosts with one MX value, and a few with a
23179 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
23180 hosts at the top of the list are tried at first. With the default retry rule,
23181 which specifies increasing retry times, the higher MX hosts are eventually
23182 tried when those at the top of the list are skipped because they have not
23183 reached their retry times.
23184
23185 However, it is common practice to put a fixed short retry time on domains for
23186 large ISPs, on the grounds that their servers are rarely down for very long.
23187 Unfortunately, these are exactly the domains that tend to resolve to long lists
23188 of hosts. The short retry time means that the lowest MX hosts are tried every
23189 time. The attempts may be in a different order because of random sorting, but
23190 without the special MX check, the higher MX hosts would never be tried until
23191 all the lower MX hosts had timed out (which might be several days), because
23192 there are always some lower MX hosts that have reached their retry times. With
23193 the special check, Exim considers at least one IP address from each MX value at
23194 every delivery attempt, even if the &%hosts_max_try%& limit has already been
23195 reached.
23196
23197 The above logic means that &%hosts_max_try%& is not a hard limit, and in
23198 particular, Exim normally eventually tries all the IP addresses before timing
23199 out an email address. When &%hosts_max_try%& was implemented, this seemed a
23200 reasonable thing to do. Recently, however, some lunatic DNS configurations have
23201 been set up with hundreds of IP addresses for some domains. It can
23202 take a very long time indeed for an address to time out in these cases.
23203
23204 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
23205 Exim never tries more than this number of IP addresses; if it hits this limit
23206 and they are all timed out, the email address is bounced, even though not all
23207 possible IP addresses have been tried.
23208 .ecindex IIDsmttra1
23209 .ecindex IIDsmttra2
23210
23211
23212
23213
23214
23215 . ////////////////////////////////////////////////////////////////////////////
23216 . ////////////////////////////////////////////////////////////////////////////
23217
23218 .chapter "Address rewriting" "CHAPrewrite"
23219 .scindex IIDaddrew "rewriting" "addresses"
23220 There are some circumstances in which Exim automatically rewrites domains in
23221 addresses. The two most common are when an address is given without a domain
23222 (referred to as an &"unqualified address"&) or when an address contains an
23223 abbreviated domain that is expanded by DNS lookup.
23224
23225 Unqualified envelope addresses are accepted only for locally submitted
23226 messages, or for messages that are received from hosts matching
23227 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
23228 appropriate. Unqualified addresses in header lines are qualified if they are in
23229 locally submitted messages, or messages from hosts that are permitted to send
23230 unqualified envelope addresses. Otherwise, unqualified addresses in header
23231 lines are neither qualified nor rewritten.
23232
23233 One situation in which Exim does &'not'& automatically rewrite a domain is
23234 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
23235 such a domain should be rewritten using the &"canonical"& name, and some MTAs
23236 do this. The new RFCs do not contain this suggestion.
23237
23238
23239 .section "Explicitly configured address rewriting" "SECID147"
23240 This chapter describes the rewriting rules that can be used in the
23241 main rewrite section of the configuration file, and also in the generic
23242 &%headers_rewrite%& option that can be set on any transport.
23243
23244 Some people believe that configured address rewriting is a Mortal Sin.
23245 Others believe that life is not possible without it. Exim provides the
23246 facility; you do not have to use it.
23247
23248 The main rewriting rules that appear in the &"rewrite"& section of the
23249 configuration file are applied to addresses in incoming messages, both envelope
23250 addresses and addresses in header lines. Each rule specifies the types of
23251 address to which it applies.
23252
23253 Whether or not addresses in header lines are rewritten depends on the origin of
23254 the headers and the type of rewriting. Global rewriting, that is, rewriting
23255 rules from the rewrite section of the configuration file, is applied only to
23256 those headers that were received with the message. Header lines that are added
23257 by ACLs or by a system filter or by individual routers or transports (which
23258 are specific to individual recipient addresses) are not rewritten by the global
23259 rules.
23260
23261 Rewriting at transport time, by means of the &%headers_rewrite%& option,
23262 applies all headers except those added by routers and transports. That is, as
23263 well as the headers that were received with the message, it also applies to
23264 headers that were added by an ACL or a system filter.
23265
23266
23267 In general, rewriting addresses from your own system or domain has some
23268 legitimacy. Rewriting other addresses should be done only with great care and
23269 in special circumstances. The author of Exim believes that rewriting should be
23270 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
23271 Although it can sometimes be used as a routing tool, this is very strongly
23272 discouraged.
23273
23274 There are two commonly encountered circumstances where rewriting is used, as
23275 illustrated by these examples:
23276
23277 .ilist
23278 The company whose domain is &'hitch.fict.example'& has a number of hosts that
23279 exchange mail with each other behind a firewall, but there is only a single
23280 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
23281 &'hitch.fict.example'& when sending mail off-site.
23282 .next
23283 A host rewrites the local parts of its own users so that, for example,
23284 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
23285 .endlist
23286
23287
23288
23289 .section "When does rewriting happen?" "SECID148"
23290 .cindex "rewriting" "timing of"
23291 .cindex "&ACL;" "rewriting addresses in"
23292 Configured address rewriting can take place at several different stages of a
23293 message's processing.
23294
23295 .vindex "&$sender_address$&"
23296 At the start of an ACL for MAIL, the sender address may have been rewritten
23297 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
23298 ordinary rewrite rules have yet been applied. If, however, the sender address
23299 is verified in the ACL, it is rewritten before verification, and remains
23300 rewritten thereafter. The subsequent value of &$sender_address$& is the
23301 rewritten address. This also applies if sender verification happens in a
23302 RCPT ACL. Otherwise, when the sender address is not verified, it is
23303 rewritten as soon as a message's header lines have been received.
23304
23305 .vindex "&$domain$&"
23306 .vindex "&$local_part$&"
23307 Similarly, at the start of an ACL for RCPT, the current recipient's address
23308 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
23309 rewrite rules have yet been applied to it. However, the behaviour is different
23310 from the sender address when a recipient is verified. The address is rewritten
23311 for the verification, but the rewriting is not remembered at this stage. The
23312 value of &$local_part$& and &$domain$& after verification are always the same
23313 as they were before (that is, they contain the unrewritten &-- except for
23314 SMTP-time rewriting &-- address).
23315
23316 As soon as a message's header lines have been received, all the envelope
23317 recipient addresses are permanently rewritten, and rewriting is also applied to
23318 the addresses in the header lines (if configured). This happens before adding
23319 any header lines that were specified in MAIL or RCPT ACLs, and
23320 .cindex "&[local_scan()]& function" "address rewriting; timing of"
23321 before the DATA ACL and &[local_scan()]& functions are run.
23322
23323 When an address is being routed, either for delivery or for verification,
23324 rewriting is applied immediately to child addresses that are generated by
23325 redirection, unless &%no_rewrite%& is set on the router.
23326
23327 .cindex "envelope sender" "rewriting at transport time"
23328 .cindex "rewriting" "at transport time"
23329 .cindex "header lines" "rewriting at transport time"
23330 At transport time, additional rewriting of addresses in header lines can be
23331 specified by setting the generic &%headers_rewrite%& option on a transport.
23332 This option contains rules that are identical in form to those in the rewrite
23333 section of the configuration file. They are applied to the original message
23334 header lines and any that were added by ACLs or a system filter. They are not
23335 applied to header lines that are added by routers or the transport.
23336
23337 The outgoing envelope sender can be rewritten by means of the &%return_path%&
23338 transport option. However, it is not possible to rewrite envelope recipients at
23339 transport time.
23340
23341
23342
23343
23344 .section "Testing the rewriting rules that apply on input" "SECID149"
23345 .cindex "rewriting" "testing"
23346 .cindex "testing" "rewriting"
23347 Exim's input rewriting configuration appears in a part of the run time
23348 configuration file headed by &"begin rewrite"&. It can be tested by the
23349 &%-brw%& command line option. This takes an address (which can be a full RFC
23350 2822 address) as its argument. The output is a list of how the address would be
23351 transformed by the rewriting rules for each of the different places it might
23352 appear in an incoming message, that is, for each different header and for the
23353 envelope sender and recipient fields. For example,
23354 .code
23355 exim -brw ph10@exim.workshop.example
23356 .endd
23357 might produce the output
23358 .code
23359 sender: Philip.Hazel@exim.workshop.example
23360 from: Philip.Hazel@exim.workshop.example
23361 to: ph10@exim.workshop.example
23362 cc: ph10@exim.workshop.example
23363 bcc: ph10@exim.workshop.example
23364 reply-to: Philip.Hazel@exim.workshop.example
23365 env-from: Philip.Hazel@exim.workshop.example
23366 env-to: ph10@exim.workshop.example
23367 .endd
23368 which shows that rewriting has been set up for that address when used in any of
23369 the source fields, but not when it appears as a recipient address. At the
23370 present time, there is no equivalent way of testing rewriting rules that are
23371 set for a particular transport.
23372
23373
23374 .section "Rewriting rules" "SECID150"
23375 .cindex "rewriting" "rules"
23376 The rewrite section of the configuration file consists of lines of rewriting
23377 rules in the form
23378 .display
23379 <&'source pattern'&> <&'replacement'&> <&'flags'&>
23380 .endd
23381 Rewriting rules that are specified for the &%headers_rewrite%& generic
23382 transport option are given as a colon-separated list. Each item in the list
23383 takes the same form as a line in the main rewriting configuration (except that
23384 any colons must be doubled, of course).
23385
23386 The formats of source patterns and replacement strings are described below.
23387 Each is terminated by white space, unless enclosed in double quotes, in which
23388 case normal quoting conventions apply inside the quotes. The flags are single
23389 characters which may appear in any order. Spaces and tabs between them are
23390 ignored.
23391
23392 For each address that could potentially be rewritten, the rules are scanned in
23393 order, and replacements for the address from earlier rules can themselves be
23394 replaced by later rules (but see the &"q"& and &"R"& flags).
23395
23396 The order in which addresses are rewritten is undefined, may change between
23397 releases, and must not be relied on, with one exception: when a message is
23398 received, the envelope sender is always rewritten first, before any header
23399 lines are rewritten. For example, the replacement string for a rewrite of an
23400 address in &'To:'& must not assume that the message's address in &'From:'& has
23401 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
23402 that the envelope sender has already been rewritten.
23403
23404 .vindex "&$domain$&"
23405 .vindex "&$local_part$&"
23406 The variables &$local_part$& and &$domain$& can be used in the replacement
23407 string to refer to the address that is being rewritten. Note that lookup-driven
23408 rewriting can be done by a rule of the form
23409 .code
23410 *@* ${lookup ...
23411 .endd
23412 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
23413 refer to the address that is being rewritten.
23414
23415
23416 .section "Rewriting patterns" "SECID151"
23417 .cindex "rewriting" "patterns"
23418 .cindex "address list" "in a rewriting pattern"
23419 The source pattern in a rewriting rule is any item which may appear in an
23420 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
23421 single-item address list, which means that it is expanded before being tested
23422 against the address. As always, if you use a regular expression as a pattern,
23423 you must take care to escape dollar and backslash characters, or use the &`\N`&
23424 facility to suppress string expansion within the regular expression.
23425
23426 Domains in patterns should be given in lower case. Local parts in patterns are
23427 case-sensitive. If you want to do case-insensitive matching of local parts, you
23428 can use a regular expression that starts with &`^(?i)`&.
23429
23430 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
23431 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
23432 depending on the type of match which occurred. These can be used in the
23433 replacement string to insert portions of the incoming address. &$0$& always
23434 refers to the complete incoming address. When a regular expression is used, the
23435 numerical variables are set from its capturing subexpressions. For other types
23436 of pattern they are set as follows:
23437
23438 .ilist
23439 If a local part or domain starts with an asterisk, the numerical variables
23440 refer to the character strings matched by asterisks, with &$1$& associated with
23441 the first asterisk, and &$2$& with the second, if present. For example, if the
23442 pattern
23443 .code
23444 *queen@*.fict.example
23445 .endd
23446 is matched against the address &'hearts-queen@wonderland.fict.example'& then
23447 .code
23448 $0 = hearts-queen@wonderland.fict.example
23449 $1 = hearts-
23450 $2 = wonderland
23451 .endd
23452 Note that if the local part does not start with an asterisk, but the domain
23453 does, it is &$1$& that contains the wild part of the domain.
23454
23455 .next
23456 If the domain part of the pattern is a partial lookup, the wild and fixed parts
23457 of the domain are placed in the next available numerical variables. Suppose,
23458 for example, that the address &'foo@bar.baz.example'& is processed by a
23459 rewriting rule of the form
23460 .display
23461 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
23462 .endd
23463 and the key in the file that matches the domain is &`*.baz.example`&. Then
23464 .code
23465 $1 = foo
23466 $2 = bar
23467 $3 = baz.example
23468 .endd
23469 If the address &'foo@baz.example'& is looked up, this matches the same
23470 wildcard file entry, and in this case &$2$& is set to the empty string, but
23471 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
23472 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
23473 whole domain. For non-partial domain lookups, no numerical variables are set.
23474 .endlist
23475
23476
23477 .section "Rewriting replacements" "SECID152"
23478 .cindex "rewriting" "replacements"
23479 If the replacement string for a rule is a single asterisk, addresses that
23480 match the pattern and the flags are &'not'& rewritten, and no subsequent
23481 rewriting rules are scanned. For example,
23482 .code
23483 hatta@lookingglass.fict.example * f
23484 .endd
23485 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
23486 &'From:'& headers.
23487
23488 .vindex "&$domain$&"
23489 .vindex "&$local_part$&"
23490 If the replacement string is not a single asterisk, it is expanded, and must
23491 yield a fully qualified address. Within the expansion, the variables
23492 &$local_part$& and &$domain$& refer to the address that is being rewritten.
23493 Any letters they contain retain their original case &-- they are not lower
23494 cased. The numerical variables are set up according to the type of pattern that
23495 matched the address, as described above. If the expansion is forced to fail by
23496 the presence of &"fail"& in a conditional or lookup item, rewriting by the
23497 current rule is abandoned, but subsequent rules may take effect. Any other
23498 expansion failure causes the entire rewriting operation to be abandoned, and an
23499 entry written to the panic log.
23500
23501
23502
23503 .section "Rewriting flags" "SECID153"
23504 There are three different kinds of flag that may appear on rewriting rules:
23505
23506 .ilist
23507 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
23508 c, f, h, r, s, t.
23509 .next
23510 A flag that specifies rewriting at SMTP time: S.
23511 .next
23512 Flags that control the rewriting process: Q, q, R, w.
23513 .endlist
23514
23515 For rules that are part of the &%headers_rewrite%& generic transport option,
23516 E, F, T, and S are not permitted.
23517
23518
23519
23520 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
23521 "SECID154"
23522 .cindex "rewriting" "flags"
23523 If none of the following flag letters, nor the &"S"& flag (see section
23524 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
23525 and to both the sender and recipient fields of the envelope, whereas a
23526 transport-time rewriting rule just applies to all headers. Otherwise, the
23527 rewriting rule is skipped unless the relevant addresses are being processed.
23528 .display
23529 &`E`& rewrite all envelope fields
23530 &`F`& rewrite the envelope From field
23531 &`T`& rewrite the envelope To field
23532 &`b`& rewrite the &'Bcc:'& header
23533 &`c`& rewrite the &'Cc:'& header
23534 &`f`& rewrite the &'From:'& header
23535 &`h`& rewrite all headers
23536 &`r`& rewrite the &'Reply-To:'& header
23537 &`s`& rewrite the &'Sender:'& header
23538 &`t`& rewrite the &'To:'& header
23539 .endd
23540 "All headers" means all of the headers listed above that can be selected
23541 individually, plus their &'Resent-'& versions. It does not include
23542 other headers such as &'Subject:'& etc.
23543
23544 You should be particularly careful about rewriting &'Sender:'& headers, and
23545 restrict this to special known cases in your own domains.
23546
23547
23548 .section "The SMTP-time rewriting flag" "SECTrewriteS"
23549 .cindex "SMTP" "rewriting malformed addresses"
23550 .cindex "RCPT" "rewriting argument of"
23551 .cindex "MAIL" "rewriting argument of"
23552 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
23553 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
23554 before any other processing; even before syntax checking. The pattern is
23555 required to be a regular expression, and it is matched against the whole of the
23556 data for the command, including any surrounding angle brackets.
23557
23558 .vindex "&$domain$&"
23559 .vindex "&$local_part$&"
23560 This form of rewrite rule allows for the handling of addresses that are not
23561 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
23562 input). Because the input is not required to be a syntactically valid address,
23563 the variables &$local_part$& and &$domain$& are not available during the
23564 expansion of the replacement string. The result of rewriting replaces the
23565 original address in the MAIL or RCPT command.
23566
23567
23568 .section "Flags controlling the rewriting process" "SECID155"
23569 There are four flags which control the way the rewriting process works. These
23570 take effect only when a rule is invoked, that is, when the address is of the
23571 correct type (matches the flags) and matches the pattern:
23572
23573 .ilist
23574 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
23575 unqualified local part. It is qualified with &%qualify_recipient%&. In the
23576 absence of &"Q"& the rewritten address must always include a domain.
23577 .next
23578 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
23579 even if no rewriting actually takes place because of a &"fail"& in the
23580 expansion. The &"q"& flag is not effective if the address is of the wrong type
23581 (does not match the flags) or does not match the pattern.
23582 .next
23583 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
23584 address, up to ten times. It can be combined with the &"q"& flag, to stop
23585 rewriting once it fails to match (after at least one successful rewrite).
23586 .next
23587 .cindex "rewriting" "whole addresses"
23588 When an address in a header is rewritten, the rewriting normally applies only
23589 to the working part of the address, with any comments and RFC 2822 &"phrase"&
23590 left unchanged. For example, rewriting might change
23591 .code
23592 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
23593 .endd
23594 into
23595 .code
23596 From: Ford Prefect <prefectf@hitch.fict.example>
23597 .endd
23598 .cindex "RFC 2047"
23599 Sometimes there is a need to replace the whole address item, and this can be
23600 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
23601 causes an address in a header line to be rewritten, the entire address is
23602 replaced, not just the working part. The replacement must be a complete RFC
23603 2822 address, including the angle brackets if necessary. If text outside angle
23604 brackets contains a character whose value is greater than 126 or less than 32
23605 (except for tab), the text is encoded according to RFC 2047. The character set
23606 is taken from &%headers_charset%&, which defaults to ISO-8859-1.
23607
23608 When the &"w"& flag is set on a rule that causes an envelope address to be
23609 rewritten, all but the working part of the replacement address is discarded.
23610 .endlist
23611
23612
23613 .section "Rewriting examples" "SECID156"
23614 Here is an example of the two common rewriting paradigms:
23615 .code
23616 *@*.hitch.fict.example $1@hitch.fict.example
23617 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
23618 {$value}fail}@hitch.fict.example bctfrF
23619 .endd
23620 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
23621 the string expansion to fail if the lookup does not succeed. In this context it
23622 has the effect of leaving the original address unchanged, but Exim goes on to
23623 consider subsequent rewriting rules, if any, because the &"q"& flag is not
23624 present in that rule. An alternative to &"fail"& would be to supply &$1$&
23625 explicitly, which would cause the rewritten address to be the same as before,
23626 at the cost of a small bit of processing. Not supplying either of these is an
23627 error, since the rewritten address would then contain no local part.
23628
23629 The first example above replaces the domain with a superior, more general
23630 domain. This may not be desirable for certain local parts. If the rule
23631 .code
23632 root@*.hitch.fict.example *
23633 .endd
23634 were inserted before the first rule, rewriting would be suppressed for the
23635 local part &'root'& at any domain ending in &'hitch.fict.example'&.
23636
23637 Rewriting can be made conditional on a number of tests, by making use of
23638 &${if$& in the expansion item. For example, to apply a rewriting rule only to
23639 messages that originate outside the local host:
23640 .code
23641 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
23642 {$1@hitch.fict.example}fail}"
23643 .endd
23644 The replacement string is quoted in this example because it contains white
23645 space.
23646
23647 .cindex "rewriting" "bang paths"
23648 .cindex "bang paths" "rewriting"
23649 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
23650 an address it treats it as an unqualified local part which it qualifies with
23651 the local qualification domain (if the source of the message is local or if the
23652 remote host is permitted to send unqualified addresses). Rewriting can
23653 sometimes be used to handle simple bang paths with a fixed number of
23654 components. For example, the rule
23655 .code
23656 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
23657 .endd
23658 rewrites a two-component bang path &'host.name!user'& as the domain address
23659 &'user@host.name'&. However, there is a security implication in using this as
23660 a global rewriting rule for envelope addresses. It can provide a backdoor
23661 method for using your system as a relay, because the incoming addresses appear
23662 to be local. If the bang path addresses are received via SMTP, it is safer to
23663 use the &"S"& flag to rewrite them as they are received, so that relay checking
23664 can be done on the rewritten addresses.
23665 .ecindex IIDaddrew
23666
23667
23668
23669
23670
23671 . ////////////////////////////////////////////////////////////////////////////
23672 . ////////////////////////////////////////////////////////////////////////////
23673
23674 .chapter "Retry configuration" "CHAPretry"
23675 .scindex IIDretconf1 "retry" "configuration, description of"
23676 .scindex IIDregconf2 "configuration file" "retry section"
23677 The &"retry"& section of the runtime configuration file contains a list of
23678 retry rules that control how often Exim tries to deliver messages that cannot
23679 be delivered at the first attempt. If there are no retry rules (the section is
23680 empty or not present), there are no retries. In this situation, temporary
23681 errors are treated as permanent. The default configuration contains a single,
23682 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
23683 line option can be used to test which retry rule will be used for a given
23684 address, domain and error.
23685
23686 The most common cause of retries is temporary failure to deliver to a remote
23687 host because the host is down, or inaccessible because of a network problem.
23688 Exim's retry processing in this case is applied on a per-host (strictly, per IP
23689 address) basis, not on a per-message basis. Thus, if one message has recently
23690 been delayed, delivery of a new message to the same host is not immediately
23691 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
23692 log selector is set, the message
23693 .cindex "retry" "time not reached"
23694 &"retry time not reached"& is written to the main log whenever a delivery is
23695 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
23696 the handling of errors during remote deliveries.
23697
23698 Retry processing applies to routing as well as to delivering, except as covered
23699 in the next paragraph. The retry rules do not distinguish between these
23700 actions. It is not possible, for example, to specify different behaviour for
23701 failures to route the domain &'snark.fict.example'& and failures to deliver to
23702 the host &'snark.fict.example'&. I didn't think anyone would ever need this
23703 added complication, so did not implement it. However, although they share the
23704 same retry rule, the actual retry times for routing and transporting a given
23705 domain are maintained independently.
23706
23707 When a delivery is not part of a queue run (typically an immediate delivery on
23708 receipt of a message), the routers are always run, and local deliveries are
23709 always attempted, even if retry times are set for them. This makes for better
23710 behaviour if one particular message is causing problems (for example, causing
23711 quota overflow, or provoking an error in a filter file). If such a delivery
23712 suffers a temporary failure, the retry data is updated as normal, and
23713 subsequent delivery attempts from queue runs occur only when the retry time for
23714 the local address is reached.
23715
23716 .section "Changing retry rules" "SECID157"
23717 If you change the retry rules in your configuration, you should consider
23718 whether or not to delete the retry data that is stored in Exim's spool area in
23719 files with names like &_db/retry_&. Deleting any of Exim's hints files is
23720 always safe; that is why they are called &"hints"&.
23721
23722 The hints retry data contains suggested retry times based on the previous
23723 rules. In the case of a long-running problem with a remote host, it might
23724 record the fact that the host has timed out. If your new rules increase the
23725 timeout time for such a host, you should definitely remove the old retry data
23726 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
23727 messages that it should now be retaining.
23728
23729
23730
23731 .section "Format of retry rules" "SECID158"
23732 .cindex "retry" "rules"
23733 Each retry rule occupies one line and consists of three or four parts,
23734 separated by white space: a pattern, an error name, an optional list of sender
23735 addresses, and a list of retry parameters. The pattern and sender lists must be
23736 enclosed in double quotes if they contain white space. The rules are searched
23737 in order until one is found where the pattern, error name, and sender list (if
23738 present) match the failing host or address, the error that occurred, and the
23739 message's sender, respectively.
23740
23741
23742 The pattern is any single item that may appear in an address list (see section
23743 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
23744 which means that it is expanded before being tested against the address that
23745 has been delayed. A negated address list item is permitted. Address
23746 list processing treats a plain domain name as if it were preceded by &"*@"&,
23747 which makes it possible for many retry rules to start with just a domain. For
23748 example,
23749 .code
23750 lookingglass.fict.example * F,24h,30m;
23751 .endd
23752 provides a rule for any address in the &'lookingglass.fict.example'& domain,
23753 whereas
23754 .code
23755 alice@lookingglass.fict.example * F,24h,30m;
23756 .endd
23757 applies only to temporary failures involving the local part &%alice%&.
23758 In practice, almost all rules start with a domain name pattern without a local
23759 part.
23760
23761 .cindex "regular expressions" "in retry rules"
23762 &*Warning*&: If you use a regular expression in a retry rule pattern, it
23763 must match a complete address, not just a domain, because that is how regular
23764 expressions work in address lists.
23765 .display
23766 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
23767 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
23768 .endd
23769
23770
23771 .section "Choosing which retry rule to use for address errors" "SECID159"
23772 When Exim is looking for a retry rule after a routing attempt has failed (for
23773 example, after a DNS timeout), each line in the retry configuration is tested
23774 against the complete address only if &%retry_use_local_part%& is set for the
23775 router. Otherwise, only the domain is used, except when matching against a
23776 regular expression, when the local part of the address is replaced with &"*"&.
23777 A domain on its own can match a domain pattern, or a pattern that starts with
23778 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
23779 &%check_local_user%& is true, and false for other routers.
23780
23781 Similarly, when Exim is looking for a retry rule after a local delivery has
23782 failed (for example, after a mailbox full error), each line in the retry
23783 configuration is tested against the complete address only if
23784 &%retry_use_local_part%& is set for the transport (it defaults true for all
23785 local transports).
23786
23787 .cindex "4&'xx'& responses" "retry rules for"
23788 However, when Exim is looking for a retry rule after a remote delivery attempt
23789 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
23790 whole address is always used as the key when searching the retry rules. The
23791 rule that is found is used to create a retry time for the combination of the
23792 failing address and the message's sender. It is the combination of sender and
23793 recipient that is delayed in subsequent queue runs until its retry time is
23794 reached. You can delay the recipient without regard to the sender by setting
23795 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
23796 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
23797 commands.
23798
23799
23800
23801 .section "Choosing which retry rule to use for host and message errors" &&&
23802 "SECID160"
23803 For a temporary error that is not related to an individual address (for
23804 example, a connection timeout), each line in the retry configuration is checked
23805 twice. First, the name of the remote host is used as a domain name (preceded by
23806 &"*@"& when matching a regular expression). If this does not match the line,
23807 the domain from the email address is tried in a similar fashion. For example,
23808 suppose the MX records for &'a.b.c.example'& are
23809 .code
23810 a.b.c.example MX 5 x.y.z.example
23811 MX 6 p.q.r.example
23812 MX 7 m.n.o.example
23813 .endd
23814 and the retry rules are
23815 .code
23816 p.q.r.example * F,24h,30m;
23817 a.b.c.example * F,4d,45m;
23818 .endd
23819 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
23820 first rule matches neither the host nor the domain, so Exim looks at the second
23821 rule. This does not match the host, but it does match the domain, so it is used
23822 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
23823 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
23824 first retry rule is used, because it matches the host.
23825
23826 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
23827 first rule to determine retry times, but for all the other hosts for the domain
23828 &'a.b.c.example'&, the second rule is used. The second rule is also used if
23829 routing to &'a.b.c.example'& suffers a temporary failure.
23830
23831 &*Note*&: The host name is used when matching the patterns, not its IP address.
23832 However, if a message is routed directly to an IP address without the use of a
23833 host name, for example, if a &(manualroute)& router contains a setting such as:
23834 .code
23835 route_list = *.a.example 192.168.34.23
23836 .endd
23837 then the &"host name"& that is used when searching for a retry rule is the
23838 textual form of the IP address.
23839
23840 .section "Retry rules for specific errors" "SECID161"
23841 .cindex "retry" "specific errors; specifying"
23842 The second field in a retry rule is the name of a particular error, or an
23843 asterisk, which matches any error. The errors that can be tested for are:
23844
23845 .vlist
23846 .vitem &%auth_failed%&
23847 Authentication failed when trying to send to a host in the
23848 &%hosts_require_auth%& list in an &(smtp)& transport.
23849
23850 .vitem &%data_4xx%&
23851 A 4&'xx'& error was received for an outgoing DATA command, either immediately
23852 after the command, or after sending the message's data.
23853
23854 .vitem &%mail_4xx%&
23855 A 4&'xx'& error was received for an outgoing MAIL command.
23856
23857 .vitem &%rcpt_4xx%&
23858 A 4&'xx'& error was received for an outgoing RCPT command.
23859 .endlist
23860
23861 For the three 4&'xx'& errors, either the first or both of the x's can be given
23862 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
23863 recognize 452 errors given to RCPT commands for addresses in a certain domain,
23864 and have retries every ten minutes with a one-hour timeout, you could set up a
23865 retry rule of this form:
23866 .code
23867 the.domain.name rcpt_452 F,1h,10m
23868 .endd
23869 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
23870 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
23871
23872 .vlist
23873 .vitem &%lost_connection%&
23874 A server unexpectedly closed the SMTP connection. There may, of course,
23875 legitimate reasons for this (host died, network died), but if it repeats a lot
23876 for the same host, it indicates something odd.
23877
23878 .vitem &%refused_MX%&
23879 A connection to a host obtained from an MX record was refused.
23880
23881 .vitem &%refused_A%&
23882 A connection to a host not obtained from an MX record was refused.
23883
23884 .vitem &%refused%&
23885 A connection was refused.
23886
23887 .vitem &%timeout_connect_MX%&
23888 A connection attempt to a host obtained from an MX record timed out.
23889
23890 .vitem &%timeout_connect_A%&
23891 A connection attempt to a host not obtained from an MX record timed out.
23892
23893 .vitem &%timeout_connect%&
23894 A connection attempt timed out.
23895
23896 .vitem &%timeout_MX%&
23897 There was a timeout while connecting or during an SMTP session with a host
23898 obtained from an MX record.
23899
23900 .vitem &%timeout_A%&
23901 There was a timeout while connecting or during an SMTP session with a host not
23902 obtained from an MX record.
23903
23904 .vitem &%timeout%&
23905 There was a timeout while connecting or during an SMTP session.
23906
23907 .vitem &%tls_required%&
23908 The server was required to use TLS (it matched &%hosts_require_tls%& in the
23909 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
23910 to STARTTLS, or there was a problem setting up the TLS connection.
23911
23912 .vitem &%quota%&
23913 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
23914 transport.
23915
23916 .vitem &%quota_%&<&'time'&>
23917 .cindex "quota" "error testing in retry rule"
23918 .cindex "retry" "quota error testing"
23919 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
23920 transport, and the mailbox has not been accessed for <&'time'&>. For example,
23921 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
23922 for four days.
23923 .endlist
23924
23925 .cindex "mailbox" "time of last read"
23926 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
23927 timeouts when the mailbox is full and is not being read by its owner. Ideally,
23928 it should be based on the last time that the user accessed the mailbox.
23929 However, it is not always possible to determine this. Exim uses the following
23930 heuristic rules:
23931
23932 .ilist
23933 If the mailbox is a single file, the time of last access (the &"atime"&) is
23934 used. As no new messages are being delivered (because the mailbox is over
23935 quota), Exim does not access the file, so this is the time of last user access.
23936 .next
23937 .cindex "maildir format" "time of last read"
23938 For a maildir delivery, the time of last modification of the &_new_&
23939 subdirectory is used. As the mailbox is over quota, no new files are created in
23940 the &_new_& subdirectory, because no new messages are being delivered. Any
23941 change to the &_new_& subdirectory is therefore assumed to be the result of an
23942 MUA moving a new message to the &_cur_& directory when it is first read. The
23943 time that is used is therefore the last time that the user read a new message.
23944 .next
23945 For other kinds of multi-file mailbox, the time of last access cannot be
23946 obtained, so a retry rule that uses this type of error field is never matched.
23947 .endlist
23948
23949 The quota errors apply both to system-enforced quotas and to Exim's own quota
23950 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
23951 when a local delivery is deferred because a partition is full (the ENOSPC
23952 error).
23953
23954
23955
23956 .section "Retry rules for specified senders" "SECID162"
23957 .cindex "retry" "rules; sender-specific"
23958 You can specify retry rules that apply only when the failing message has a
23959 specific sender. In particular, this can be used to define retry rules that
23960 apply only to bounce messages. The third item in a retry rule can be of this
23961 form:
23962 .display
23963 &`senders=`&<&'address list'&>
23964 .endd
23965 The retry timings themselves are then the fourth item. For example:
23966 .code
23967 * rcpt_4xx senders=: F,1h,30m
23968 .endd
23969 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
23970 host. If the address list contains white space, it must be enclosed in quotes.
23971 For example:
23972 .code
23973 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
23974 .endd
23975 &*Warning*&: This facility can be unhelpful if it is used for host errors
23976 (which do not depend on the recipient). The reason is that the sender is used
23977 only to match the retry rule. Once the rule has been found for a host error,
23978 its contents are used to set a retry time for the host, and this will apply to
23979 all messages, not just those with specific senders.
23980
23981 When testing retry rules using &%-brt%&, you can supply a sender using the
23982 &%-f%& command line option, like this:
23983 .code
23984 exim -f "" -brt user@dom.ain
23985 .endd
23986 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
23987 list is never matched.
23988
23989
23990
23991
23992
23993 .section "Retry parameters" "SECID163"
23994 .cindex "retry" "parameters in rules"
23995 The third (or fourth, if a senders list is present) field in a retry rule is a
23996 sequence of retry parameter sets, separated by semicolons. Each set consists of
23997 .display
23998 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
23999 .endd
24000 The letter identifies the algorithm for computing a new retry time; the cutoff
24001 time is the time beyond which this algorithm no longer applies, and the
24002 arguments vary the algorithm's action. The cutoff time is measured from the
24003 time that the first failure for the domain (combined with the local part if
24004 relevant) was detected, not from the time the message was received.
24005
24006 .cindex "retry" "algorithms"
24007 .cindex "retry" "fixed intervals"
24008 .cindex "retry" "increasing intervals"
24009 .cindex "retry" "random intervals"
24010 The available algorithms are:
24011
24012 .ilist
24013 &'F'&: retry at fixed intervals. There is a single time parameter specifying
24014 the interval.
24015 .next
24016 &'G'&: retry at geometrically increasing intervals. The first argument
24017 specifies a starting value for the interval, and the second a multiplier, which
24018 is used to increase the size of the interval at each retry.
24019 .next
24020 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
24021 retry, the previous interval is multiplied by the factor in order to get a
24022 maximum for the next interval. The minimum interval is the first argument of
24023 the parameter, and an actual interval is chosen randomly between them. Such a
24024 rule has been found to be helpful in cluster configurations when all the
24025 members of the cluster restart at once, and may therefore synchronize their
24026 queue processing times.
24027 .endlist
24028
24029 When computing the next retry time, the algorithm definitions are scanned in
24030 order until one whose cutoff time has not yet passed is reached. This is then
24031 used to compute a new retry time that is later than the current time. In the
24032 case of fixed interval retries, this simply means adding the interval to the
24033 current time. For geometrically increasing intervals, retry intervals are
24034 computed from the rule's parameters until one that is greater than the previous
24035 interval is found. The main configuration variable
24036 .cindex "limit" "retry interval"
24037 .cindex "retry" "interval, maximum"
24038 .oindex "&%retry_interval_max%&"
24039 &%retry_interval_max%& limits the maximum interval between retries. It
24040 cannot be set greater than &`24h`&, which is its default value.
24041
24042 A single remote domain may have a number of hosts associated with it, and each
24043 host may have more than one IP address. Retry algorithms are selected on the
24044 basis of the domain name, but are applied to each IP address independently. If,
24045 for example, a host has two IP addresses and one is unusable, Exim will
24046 generate retry times for it and will not try to use it until its next retry
24047 time comes. Thus the good IP address is likely to be tried first most of the
24048 time.
24049
24050 .cindex "hints database" "use for retrying"
24051 Retry times are hints rather than promises. Exim does not make any attempt to
24052 run deliveries exactly at the computed times. Instead, a queue runner process
24053 starts delivery processes for delayed messages periodically, and these attempt
24054 new deliveries only for those addresses that have passed their next retry time.
24055 If a new message arrives for a deferred address, an immediate delivery attempt
24056 occurs only if the address has passed its retry time. In the absence of new
24057 messages, the minimum time between retries is the interval between queue runner
24058 processes. There is not much point in setting retry times of five minutes if
24059 your queue runners happen only once an hour, unless there are a significant
24060 number of incoming messages (which might be the case on a system that is
24061 sending everything to a smart host, for example).
24062
24063 The data in the retry hints database can be inspected by using the
24064 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
24065 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
24066 &'exinext'& utility script can be used to find out what the next retry times
24067 are for the hosts associated with a particular mail domain, and also for local
24068 deliveries that have been deferred.
24069
24070
24071 .section "Retry rule examples" "SECID164"
24072 Here are some example retry rules:
24073 .code
24074 alice@wonderland.fict.example quota_5d F,7d,3h
24075 wonderland.fict.example quota_5d
24076 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
24077 lookingglass.fict.example * F,24h,30m;
24078 * refused_A F,2h,20m;
24079 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
24080 .endd
24081 The first rule sets up special handling for mail to
24082 &'alice@wonderland.fict.example'& when there is an over-quota error and the
24083 mailbox has not been read for at least 5 days. Retries continue every three
24084 hours for 7 days. The second rule handles over-quota errors for all other local
24085 parts at &'wonderland.fict.example'&; the absence of a local part has the same
24086 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
24087 fail are bounced immediately if the mailbox has not been read for at least 5
24088 days.
24089
24090 The third rule handles all other errors at &'wonderland.fict.example'&; retries
24091 happen every 15 minutes for an hour, then with geometrically increasing
24092 intervals until two days have passed since a delivery first failed. After the
24093 first hour there is a delay of one hour, then two hours, then four hours, and
24094 so on (this is a rather extreme example).
24095
24096 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
24097 They happen every 30 minutes for 24 hours only. The remaining two rules handle
24098 all other domains, with special action for connection refusal from hosts that
24099 were not obtained from an MX record.
24100
24101 The final rule in a retry configuration should always have asterisks in the
24102 first two fields so as to provide a general catch-all for any addresses that do
24103 not have their own special handling. This example tries every 15 minutes for 2
24104 hours, then with intervals starting at one hour and increasing by a factor of
24105 1.5 up to 16 hours, then every 8 hours up to 5 days.
24106
24107
24108
24109 .section "Timeout of retry data" "SECID165"
24110 .cindex "timeout" "of retry data"
24111 .oindex "&%retry_data_expire%&"
24112 .cindex "hints database" "data expiry"
24113 .cindex "retry" "timeout of data"
24114 Exim timestamps the data that it writes to its retry hints database. When it
24115 consults the data during a delivery it ignores any that is older than the value
24116 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
24117 been tried for 7 days, Exim will try to deliver to it immediately a message
24118 arrives, and if that fails, it will calculate a retry time as if it were
24119 failing for the first time.
24120
24121 This improves the behaviour for messages routed to rarely-used hosts such as MX
24122 backups. If such a host was down at one time, and happens to be down again when
24123 Exim tries a month later, using the old retry data would imply that it had been
24124 down all the time, which is not a justified assumption.
24125
24126 If a host really is permanently dead, this behaviour causes a burst of retries
24127 every now and again, but only if messages routed to it are rare. If there is a
24128 message at least once every 7 days the retry data never expires.
24129
24130
24131
24132
24133 .section "Long-term failures" "SECID166"
24134 .cindex "delivery failure, long-term"
24135 .cindex "retry" "after long-term failure"
24136 Special processing happens when an email address has been failing for so long
24137 that the cutoff time for the last algorithm is reached. For example, using the
24138 default retry rule:
24139 .code
24140 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
24141 .endd
24142 the cutoff time is four days. Reaching the retry cutoff is independent of how
24143 long any specific message has been failing; it is the length of continuous
24144 failure for the recipient address that counts.
24145
24146 When the cutoff time is reached for a local delivery, or for all the IP
24147 addresses associated with a remote delivery, a subsequent delivery failure
24148 causes Exim to give up on the address, and a bounce message is generated.
24149 In order to cater for new messages that use the failing address, a next retry
24150 time is still computed from the final algorithm, and is used as follows:
24151
24152 For local deliveries, one delivery attempt is always made for any subsequent
24153 messages. If this delivery fails, the address fails immediately. The
24154 post-cutoff retry time is not used.
24155
24156 If the delivery is remote, there are two possibilities, controlled by the
24157 .oindex "&%delay_after_cutoff%&"
24158 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
24159 default. Until the post-cutoff retry time for one of the IP addresses is
24160 reached, the failing email address is bounced immediately, without a delivery
24161 attempt taking place. After that time, one new delivery attempt is made to
24162 those IP addresses that are past their retry times, and if that still fails,
24163 the address is bounced and new retry times are computed.
24164
24165 In other words, when all the hosts for a given email address have been failing
24166 for a long time, Exim bounces rather then defers until one of the hosts' retry
24167 times is reached. Then it tries once, and bounces if that attempt fails. This
24168 behaviour ensures that few resources are wasted in repeatedly trying to deliver
24169 to a broken destination, but if the host does recover, Exim will eventually
24170 notice.
24171
24172 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
24173 addresses are past their final cutoff time, Exim tries to deliver to those IP
24174 addresses that have not been tried since the message arrived. If there are
24175 no suitable IP addresses, or if they all fail, the address is bounced. In other
24176 words, it does not delay when a new message arrives, but tries the expired
24177 addresses immediately, unless they have been tried since the message arrived.
24178 If there is a continuous stream of messages for the failing domains, setting
24179 &%delay_after_cutoff%& false means that there will be many more attempts to
24180 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
24181 true.
24182
24183 .section "Deliveries that work intermittently" "SECID167"
24184 .cindex "retry" "intermittently working deliveries"
24185 Some additional logic is needed to cope with cases where a host is
24186 intermittently available, or when a message has some attribute that prevents
24187 its delivery when others to the same address get through. In this situation,
24188 because some messages are successfully delivered, the &"retry clock"& for the
24189 host or address keeps getting reset by the successful deliveries, and so
24190 failing messages remain on the queue for ever because the cutoff time is never
24191 reached.
24192
24193 Two exceptional actions are applied to prevent this happening. The first
24194 applies to errors that are related to a message rather than a remote host.
24195 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
24196 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
24197 commands, and quota failures. For this type of error, if a message's arrival
24198 time is earlier than the &"first failed"& time for the error, the earlier time
24199 is used when scanning the retry rules to decide when to try next and when to
24200 time out the address.
24201
24202 The exceptional second action applies in all cases. If a message has been on
24203 the queue for longer than the cutoff time of any applicable retry rule for a
24204 given address, a delivery is attempted for that address, even if it is not yet
24205 time, and if this delivery fails, the address is timed out. A new retry time is
24206 not computed in this case, so that other messages for the same address are
24207 considered immediately.
24208 .ecindex IIDretconf1
24209 .ecindex IIDregconf2
24210
24211
24212
24213
24214
24215
24216 . ////////////////////////////////////////////////////////////////////////////
24217 . ////////////////////////////////////////////////////////////////////////////
24218
24219 .chapter "SMTP authentication" "CHAPSMTPAUTH"
24220 .scindex IIDauthconf1 "SMTP" "authentication configuration"
24221 .scindex IIDauthconf2 "authentication"
24222 The &"authenticators"& section of Exim's run time configuration is concerned
24223 with SMTP authentication. This facility is an extension to the SMTP protocol,
24224 described in RFC 2554, which allows a client SMTP host to authenticate itself
24225 to a server. This is a common way for a server to recognize clients that are
24226 permitted to use it as a relay. SMTP authentication is not of relevance to the
24227 transfer of mail between servers that have no managerial connection with each
24228 other.
24229
24230 .cindex "AUTH" "description of"
24231 Very briefly, the way SMTP authentication works is as follows:
24232
24233 .ilist
24234 The server advertises a number of authentication &'mechanisms'& in response to
24235 the client's EHLO command.
24236 .next
24237 The client issues an AUTH command, naming a specific mechanism. The command
24238 may, optionally, contain some authentication data.
24239 .next
24240 The server may issue one or more &'challenges'&, to which the client must send
24241 appropriate responses. In simple authentication mechanisms, the challenges are
24242 just prompts for user names and passwords. The server does not have to issue
24243 any challenges &-- in some mechanisms the relevant data may all be transmitted
24244 with the AUTH command.
24245 .next
24246 The server either accepts or denies authentication.
24247 .next
24248 If authentication succeeds, the client may optionally make use of the AUTH
24249 option on the MAIL command to pass an authenticated sender in subsequent
24250 mail transactions. Authentication lasts for the remainder of the SMTP
24251 connection.
24252 .next
24253 If authentication fails, the client may give up, or it may try a different
24254 authentication mechanism, or it may try transferring mail over the
24255 unauthenticated connection.
24256 .endlist
24257
24258 If you are setting up a client, and want to know which authentication
24259 mechanisms the server supports, you can use Telnet to connect to port 25 (the
24260 SMTP port) on the server, and issue an EHLO command. The response to this
24261 includes the list of supported mechanisms. For example:
24262 .display
24263 &`$ `&&*&`telnet server.example 25`&*&
24264 &`Trying 192.168.34.25...`&
24265 &`Connected to server.example.`&
24266 &`Escape character is &#x0027;^]&#x0027;.`&
24267 &`220 server.example ESMTP Exim 4.20 ...`&
24268 &*&`ehlo client.example`&*&
24269 &`250-server.example Hello client.example [10.8.4.5]`&
24270 &`250-SIZE 52428800`&
24271 &`250-PIPELINING`&
24272 &`250-AUTH PLAIN`&
24273 &`250 HELP`&
24274 .endd
24275 The second-last line of this example output shows that the server supports
24276 authentication using the PLAIN mechanism. In Exim, the different authentication
24277 mechanisms are configured by specifying &'authenticator'& drivers. Like the
24278 routers and transports, which authenticators are included in the binary is
24279 controlled by build-time definitions. The following are currently available,
24280 included by setting
24281 .code
24282 AUTH_CRAM_MD5=yes
24283 AUTH_CYRUS_SASL=yes
24284 AUTH_DOVECOT=yes
24285 AUTH_GSASL=yes
24286 AUTH_HEIMDAL_GSSAPI=yes
24287 AUTH_PLAINTEXT=yes
24288 AUTH_SPA=yes
24289 .endd
24290 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
24291 authentication mechanism (RFC 2195), and the second provides an interface to
24292 the Cyrus SASL authentication library.
24293 The third is an interface to Dovecot's authentication system, delegating the
24294 work via a socket interface.
24295 The fourth provides an interface to the GNU SASL authentication library, which
24296 provides mechanisms but typically not data sources.
24297 The fifth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
24298 supporting setting a server keytab.
24299 The sixth can be configured to support
24300 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
24301 not formally documented, but used by several MUAs. The seventh authenticator
24302 supports Microsoft's &'Secure Password Authentication'& mechanism.
24303
24304 The authenticators are configured using the same syntax as other drivers (see
24305 section &<<SECTfordricon>>&). If no authenticators are required, no
24306 authentication section need be present in the configuration file. Each
24307 authenticator can in principle have both server and client functions. When Exim
24308 is receiving SMTP mail, it is acting as a server; when it is sending out
24309 messages over SMTP, it is acting as a client. Authenticator configuration
24310 options are provided for use in both these circumstances.
24311
24312 To make it clear which options apply to which situation, the prefixes
24313 &%server_%& and &%client_%& are used on option names that are specific to
24314 either the server or the client function, respectively. Server and client
24315 functions are disabled if none of their options are set. If an authenticator is
24316 to be used for both server and client functions, a single definition, using
24317 both sets of options, is required. For example:
24318 .code
24319 cram:
24320 driver = cram_md5
24321 public_name = CRAM-MD5
24322 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
24323 client_name = ph10
24324 client_secret = secret2
24325 .endd
24326 The &%server_%& option is used when Exim is acting as a server, and the
24327 &%client_%& options when it is acting as a client.
24328
24329 Descriptions of the individual authenticators are given in subsequent chapters.
24330 The remainder of this chapter covers the generic options for the
24331 authenticators, followed by general discussion of the way authentication works
24332 in Exim.
24333
24334 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
24335 per-mechanism basis. Please read carefully to determine which variables hold
24336 account labels such as usercodes and which hold passwords or other
24337 authenticating data.
24338
24339 Note that some mechanisms support two different identifiers for accounts: the
24340 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
24341 and &'authz'& are commonly encountered. The American spelling is standard here.
24342 Conceptually, authentication data such as passwords are tied to the identifier
24343 used to authenticate; servers may have rules to permit one user to act as a
24344 second user, so that after login the session is treated as though that second
24345 user had logged in. That second user is the &'authorization id'&. A robust
24346 configuration might confirm that the &'authz'& field is empty or matches the
24347 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
24348 as verified data, the &'authz'& as an unverified request which the server might
24349 choose to honour.
24350
24351 A &'realm'& is a text string, typically a domain name, presented by a server
24352 to a client to help it select an account and credentials to use. In some
24353 mechanisms, the client and server provably agree on the realm, but clients
24354 typically can not treat the realm as secure data to be blindly trusted.
24355
24356
24357
24358 .section "Generic options for authenticators" "SECID168"
24359 .cindex "authentication" "generic options"
24360 .cindex "options" "generic; for authenticators"
24361
24362 .option client_condition authenticators string&!! unset
24363 When Exim is authenticating as a client, it skips any authenticator whose
24364 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
24365 used, for example, to skip plain text authenticators when the connection is not
24366 encrypted by a setting such as:
24367 .code
24368 client_condition = ${if !eq{$tls_out_cipher}{}}
24369 .endd
24370
24371
24372 .option client_set_id authenticators string&!! unset
24373 When client authentication succeeds, this condition is expanded; the
24374 result is used in the log lines for outbound messasges.
24375 Typically it will be the user name used for authentication.
24376
24377
24378 .option driver authenticators string unset
24379 This option must always be set. It specifies which of the available
24380 authenticators is to be used.
24381
24382
24383 .option public_name authenticators string unset
24384 This option specifies the name of the authentication mechanism that the driver
24385 implements, and by which it is known to the outside world. These names should
24386 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
24387 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
24388 defaults to the driver's instance name.
24389
24390
24391 .option server_advertise_condition authenticators string&!! unset
24392 When a server is about to advertise an authentication mechanism, the condition
24393 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
24394 mechanism is not advertised.
24395 If the expansion fails, the mechanism is not advertised. If the failure was not
24396 forced, and was not caused by a lookup defer, the incident is logged.
24397 See section &<<SECTauthexiser>>& below for further discussion.
24398
24399
24400 .option server_condition authenticators string&!! unset
24401 This option must be set for a &%plaintext%& server authenticator, where it
24402 is used directly to control authentication. See section &<<SECTplainserver>>&
24403 for details.
24404
24405 For the &(gsasl)& authenticator, this option is required for various
24406 mechanisms; see chapter &<<CHAPgsasl>>& for details.
24407
24408 For the other authenticators, &%server_condition%& can be used as an additional
24409 authentication or authorization mechanism that is applied after the other
24410 authenticator conditions succeed. If it is set, it is expanded when the
24411 authenticator would otherwise return a success code. If the expansion is forced
24412 to fail, authentication fails. Any other expansion failure causes a temporary
24413 error code to be returned. If the result of a successful expansion is an empty
24414 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
24415 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
24416 other result, a temporary error code is returned, with the expanded string as
24417 the error text.
24418
24419
24420 .option server_debug_print authenticators string&!! unset
24421 If this option is set and authentication debugging is enabled (see the &%-d%&
24422 command line option), the string is expanded and included in the debugging
24423 output when the authenticator is run as a server. This can help with checking
24424 out the values of variables.
24425 If expansion of the string fails, the error message is written to the debugging
24426 output, and Exim carries on processing.
24427
24428
24429 .option server_set_id authenticators string&!! unset
24430 .vindex "&$authenticated_id$&"
24431 When an Exim server successfully authenticates a client, this string is
24432 expanded using data from the authentication, and preserved for any incoming
24433 messages in the variable &$authenticated_id$&. It is also included in the log
24434 lines for incoming messages. For example, a user/password authenticator
24435 configuration might preserve the user name that was used to authenticate, and
24436 refer to it subsequently during delivery of the message.
24437 If expansion fails, the option is ignored.
24438
24439
24440 .option server_mail_auth_condition authenticators string&!! unset
24441 This option allows a server to discard authenticated sender addresses supplied
24442 as part of MAIL commands in SMTP connections that are authenticated by the
24443 driver on which &%server_mail_auth_condition%& is set. The option is not used
24444 as part of the authentication process; instead its (unexpanded) value is
24445 remembered for later use.
24446 How it is used is described in the following section.
24447
24448
24449
24450
24451
24452 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
24453 .cindex "authentication" "sender; authenticated"
24454 .cindex "AUTH" "on MAIL command"
24455 When a client supplied an AUTH= item on a MAIL command, Exim applies
24456 the following checks before accepting it as the authenticated sender of the
24457 message:
24458
24459 .ilist
24460 If the connection is not using extended SMTP (that is, HELO was used rather
24461 than EHLO), the use of AUTH= is a syntax error.
24462 .next
24463 If the value of the AUTH= parameter is &"<>"&, it is ignored.
24464 .next
24465 .vindex "&$authenticated_sender$&"
24466 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
24467 running, the value of &$authenticated_sender$& is set to the value obtained
24468 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
24469 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
24470 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
24471 given for the MAIL command.
24472 .next
24473 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
24474 is accepted and placed in &$authenticated_sender$& only if the client has
24475 authenticated.
24476 .next
24477 If the AUTH= value was accepted by either of the two previous rules, and
24478 the client has authenticated, and the authenticator has a setting for the
24479 &%server_mail_auth_condition%&, the condition is checked at this point. The
24480 valued that was saved from the authenticator is expanded. If the expansion
24481 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
24482 &$authenticated_sender$& is deleted. If the expansion yields any other value,
24483 the value of &$authenticated_sender$& is retained and passed on with the
24484 message.
24485 .endlist
24486
24487
24488 When &$authenticated_sender$& is set for a message, it is passed on to other
24489 hosts to which Exim authenticates as a client. Do not confuse this value with
24490 &$authenticated_id$&, which is a string obtained from the authentication
24491 process, and which is not usually a complete email address.
24492
24493 .vindex "&$sender_address$&"
24494 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
24495 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
24496 therefore make use of &$authenticated_sender$&. The converse is not true: the
24497 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
24498 ACL is run.
24499
24500
24501
24502 .section "Authentication on an Exim server" "SECTauthexiser"
24503 .cindex "authentication" "on an Exim server"
24504 When Exim receives an EHLO command, it advertises the public names of those
24505 authenticators that are configured as servers, subject to the following
24506 conditions:
24507
24508 .ilist
24509 The client host must match &%auth_advertise_hosts%& (default *).
24510 .next
24511 It the &%server_advertise_condition%& option is set, its expansion must not
24512 yield the empty string, &"0"&, &"no"&, or &"false"&.
24513 .endlist
24514
24515 The order in which the authenticators are defined controls the order in which
24516 the mechanisms are advertised.
24517
24518 Some mail clients (for example, some versions of Netscape) require the user to
24519 provide a name and password for authentication whenever AUTH is advertised,
24520 even though authentication may not in fact be needed (for example, Exim may be
24521 set up to allow unconditional relaying from the client by an IP address check).
24522 You can make such clients more friendly by not advertising AUTH to them.
24523 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
24524 that runs for RCPT) to relay without authentication, you should set
24525 .code
24526 auth_advertise_hosts = ! 10.9.8.0/24
24527 .endd
24528 so that no authentication mechanisms are advertised to them.
24529
24530 The &%server_advertise_condition%& controls the advertisement of individual
24531 authentication mechanisms. For example, it can be used to restrict the
24532 advertisement of a particular mechanism to encrypted connections, by a setting
24533 such as:
24534 .code
24535 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
24536 .endd
24537 .vindex "&$tls_in_cipher$&"
24538 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
24539 yields &"yes"&, which allows the advertisement to happen.
24540
24541 When an Exim server receives an AUTH command from a client, it rejects it
24542 immediately if AUTH was not advertised in response to an earlier EHLO
24543 command. This is the case if
24544
24545 .ilist
24546 The client host does not match &%auth_advertise_hosts%&; or
24547 .next
24548 No authenticators are configured with server options; or
24549 .next
24550 Expansion of &%server_advertise_condition%& blocked the advertising of all the
24551 server authenticators.
24552 .endlist
24553
24554
24555 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
24556 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
24557 AUTH is accepted from any client host.
24558
24559 If AUTH is not rejected by the ACL, Exim searches its configuration for a
24560 server authentication mechanism that was advertised in response to EHLO and
24561 that matches the one named in the AUTH command. If it finds one, it runs
24562 the appropriate authentication protocol, and authentication either succeeds or
24563 fails. If there is no matching advertised mechanism, the AUTH command is
24564 rejected with a 504 error.
24565
24566 .vindex "&$received_protocol$&"
24567 .vindex "&$sender_host_authenticated$&"
24568 When a message is received from an authenticated host, the value of
24569 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
24570 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
24571 public name) of the authenticator driver that successfully authenticated the
24572 client from which the message was received. This variable is empty if there was
24573 no successful authentication.
24574
24575
24576
24577
24578 .section "Testing server authentication" "SECID169"
24579 .cindex "authentication" "testing a server"
24580 .cindex "AUTH" "testing a server"
24581 .cindex "base64 encoding" "creating authentication test data"
24582 Exim's &%-bh%& option can be useful for testing server authentication
24583 configurations. The data for the AUTH command has to be sent using base64
24584 encoding. A quick way to produce such data for testing is the following Perl
24585 script:
24586 .code
24587 use MIME::Base64;
24588 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
24589 .endd
24590 .cindex "binary zero" "in authentication data"
24591 This interprets its argument as a Perl string, and then encodes it. The
24592 interpretation as a Perl string allows binary zeros, which are required for
24593 some kinds of authentication, to be included in the data. For example, a
24594 command line to run this script on such data might be
24595 .code
24596 encode '\0user\0password'
24597 .endd
24598 Note the use of single quotes to prevent the shell interpreting the
24599 backslashes, so that they can be interpreted by Perl to specify characters
24600 whose code value is zero.
24601
24602 &*Warning 1*&: If either of the user or password strings starts with an octal
24603 digit, you must use three zeros instead of one after the leading backslash. If
24604 you do not, the octal digit that starts your string will be incorrectly
24605 interpreted as part of the code for the first character.
24606
24607 &*Warning 2*&: If there are characters in the strings that Perl interprets
24608 specially, you must use a Perl escape to prevent them being misinterpreted. For
24609 example, a command such as
24610 .code
24611 encode '\0user@domain.com\0pas$$word'
24612 .endd
24613 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
24614
24615 If you have the &%mimencode%& command installed, another way to do produce
24616 base64-encoded strings is to run the command
24617 .code
24618 echo -e -n `\0user\0password' | mimencode
24619 .endd
24620 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
24621 in the argument, and the &%-n%& option specifies no newline at the end of its
24622 output. However, not all versions of &%echo%& recognize these options, so you
24623 should check your version before relying on this suggestion.
24624
24625
24626
24627 .section "Authentication by an Exim client" "SECID170"
24628 .cindex "authentication" "on an Exim client"
24629 The &(smtp)& transport has two options called &%hosts_require_auth%& and
24630 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
24631 announces support for authentication, and the host matches an entry in either
24632 of these options, Exim (as a client) tries to authenticate as follows:
24633
24634 .ilist
24635 For each authenticator that is configured as a client, in the order in which
24636 they are defined in the configuration, it searches the authentication
24637 mechanisms announced by the server for one whose name matches the public name
24638 of the authenticator.
24639 .next
24640 .vindex "&$host$&"
24641 .vindex "&$host_address$&"
24642 When it finds one that matches, it runs the authenticator's client code. The
24643 variables &$host$& and &$host_address$& are available for any string expansions
24644 that the client might do. They are set to the server's name and IP address. If
24645 any expansion is forced to fail, the authentication attempt is abandoned, and
24646 Exim moves on to the next authenticator. Otherwise an expansion failure causes
24647 delivery to be deferred.
24648 .next
24649 If the result of the authentication attempt is a temporary error or a timeout,
24650 Exim abandons trying to send the message to the host for the moment. It will
24651 try again later. If there are any backup hosts available, they are tried in the
24652 usual way.
24653 .next
24654 If the response to authentication is a permanent error (5&'xx'& code), Exim
24655 carries on searching the list of authenticators and tries another one if
24656 possible. If all authentication attempts give permanent errors, or if there are
24657 no attempts because no mechanisms match (or option expansions force failure),
24658 what happens depends on whether the host matches &%hosts_require_auth%& or
24659 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
24660 delivery is deferred. The error can be detected in the retry rules, and thereby
24661 turned into a permanent error if you wish. In the second case, Exim tries to
24662 deliver the message unauthenticated.
24663 .endlist
24664
24665 .cindex "AUTH" "on MAIL command"
24666 When Exim has authenticated itself to a remote server, it adds the AUTH
24667 parameter to the MAIL commands it sends, if it has an authenticated sender for
24668 the message. If the message came from a remote host, the authenticated sender
24669 is the one that was receiving on an incoming MAIL command, provided that the
24670 incoming connection was authenticated and the &%server_mail_auth%& condition
24671 allowed the authenticated sender to be retained. If a local process calls Exim
24672 to send a message, the sender address that is built from the login name and
24673 &%qualify_domain%& is treated as authenticated. However, if the
24674 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
24675 the authenticated sender that was received with the message.
24676 .ecindex IIDauthconf1
24677 .ecindex IIDauthconf2
24678
24679
24680
24681
24682
24683
24684 . ////////////////////////////////////////////////////////////////////////////
24685 . ////////////////////////////////////////////////////////////////////////////
24686
24687 .chapter "The plaintext authenticator" "CHAPplaintext"
24688 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
24689 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
24690 The &(plaintext)& authenticator can be configured to support the PLAIN and
24691 LOGIN authentication mechanisms, both of which transfer authentication data as
24692 plain (unencrypted) text (though base64 encoded). The use of plain text is a
24693 security risk; you are strongly advised to insist on the use of SMTP encryption
24694 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
24695 use unencrypted plain text, you should not use the same passwords for SMTP
24696 connections as you do for login accounts.
24697
24698 .section "Plaintext options" "SECID171"
24699 .cindex "options" "&(plaintext)& authenticator (server)"
24700 When configured as a server, &(plaintext)& uses the following options:
24701
24702 .option server_condition authenticators string&!! unset
24703 This is actually a global authentication option, but it must be set in order to
24704 configure the &(plaintext)& driver as a server. Its use is described below.
24705
24706 .option server_prompts plaintext string&!! unset
24707 The contents of this option, after expansion, must be a colon-separated list of
24708 prompt strings. If expansion fails, a temporary authentication rejection is
24709 given.
24710
24711 .section "Using plaintext in a server" "SECTplainserver"
24712 .cindex "AUTH" "in &(plaintext)& authenticator"
24713 .cindex "binary zero" "in &(plaintext)& authenticator"
24714 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
24715 "in &(plaintext)& authenticator"
24716 .vindex "&$auth1$&, &$auth2$&, etc"
24717 .cindex "base64 encoding" "in &(plaintext)& authenticator"
24718
24719 When running as a server, &(plaintext)& performs the authentication test by
24720 expanding a string. The data sent by the client with the AUTH command, or in
24721 response to subsequent prompts, is base64 encoded, and so may contain any byte
24722 values when decoded. If any data is supplied with the command, it is treated as
24723 a list of strings, separated by NULs (binary zeros), the first three of which
24724 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
24725 (neither LOGIN nor PLAIN uses more than three strings).
24726
24727 For compatibility with previous releases of Exim, the values are also placed in
24728 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
24729 variables for this purpose is now deprecated, as it can lead to confusion in
24730 string expansions that also use them for other things.
24731
24732 If there are more strings in &%server_prompts%& than the number of strings
24733 supplied with the AUTH command, the remaining prompts are used to obtain more
24734 data. Each response from the client may be a list of NUL-separated strings.
24735
24736 .vindex "&$authenticated_id$&"
24737 Once a sufficient number of data strings have been received,
24738 &%server_condition%& is expanded. If the expansion is forced to fail,
24739 authentication fails. Any other expansion failure causes a temporary error code
24740 to be returned. If the result of a successful expansion is an empty string,
24741 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
24742 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
24743 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
24744 For any other result, a temporary error code is returned, with the expanded
24745 string as the error text
24746
24747 &*Warning*&: If you use a lookup in the expansion to find the user's
24748 password, be sure to make the authentication fail if the user is unknown.
24749 There are good and bad examples at the end of the next section.
24750
24751
24752
24753 .section "The PLAIN authentication mechanism" "SECID172"
24754 .cindex "PLAIN authentication mechanism"
24755 .cindex "authentication" "PLAIN mechanism"
24756 .cindex "binary zero" "in &(plaintext)& authenticator"
24757 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
24758 sent as one item of data (that is, one combined string containing two NUL
24759 separators). The data is sent either as part of the AUTH command, or
24760 subsequently in response to an empty prompt from the server.
24761
24762 The second and third strings are a user name and a corresponding password.
24763 Using a single fixed user name and password as an example, this could be
24764 configured as follows:
24765 .code
24766 fixed_plain:
24767 driver = plaintext
24768 public_name = PLAIN
24769 server_prompts = :
24770 server_condition = \
24771 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
24772 server_set_id = $auth2
24773 .endd
24774 Note that the default result strings from &%if%& (&"true"& or an empty string)
24775 are exactly what we want here, so they need not be specified. Obviously, if the
24776 password contains expansion-significant characters such as dollar, backslash,
24777 or closing brace, they have to be escaped.
24778
24779 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
24780 the end of a string list are ignored). If all the data comes as part of the
24781 AUTH command, as is commonly the case, the prompt is not used. This
24782 authenticator is advertised in the response to EHLO as
24783 .code
24784 250-AUTH PLAIN
24785 .endd
24786 and a client host can authenticate itself by sending the command
24787 .code
24788 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
24789 .endd
24790 As this contains three strings (more than the number of prompts), no further
24791 data is required from the client. Alternatively, the client may just send
24792 .code
24793 AUTH PLAIN
24794 .endd
24795 to initiate authentication, in which case the server replies with an empty
24796 prompt. The client must respond with the combined data string.
24797
24798 The data string is base64 encoded, as required by the RFC. This example,
24799 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
24800 represents a zero byte. This is split up into three strings, the first of which
24801 is empty. The &%server_condition%& option in the authenticator checks that the
24802 second two are &`username`& and &`mysecret`& respectively.
24803
24804 Having just one fixed user name and password, as in this example, is not very
24805 realistic, though for a small organization with only a handful of
24806 authenticating clients it could make sense.
24807
24808 A more sophisticated instance of this authenticator could use the user name in
24809 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
24810 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
24811 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
24812 This is an incorrect example:
24813 .code
24814 server_condition = \
24815 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
24816 .endd
24817 The expansion uses the user name (&$auth2$&) as the key to look up a password,
24818 which it then compares to the supplied password (&$auth3$&). Why is this example
24819 incorrect? It works fine for existing users, but consider what happens if a
24820 non-existent user name is given. The lookup fails, but as no success/failure
24821 strings are given for the lookup, it yields an empty string. Thus, to defeat
24822 the authentication, all a client has to do is to supply a non-existent user
24823 name and an empty password. The correct way of writing this test is:
24824 .code
24825 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
24826 {${if eq{$value}{$auth3}}} {false}}
24827 .endd
24828 In this case, if the lookup succeeds, the result is checked; if the lookup
24829 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
24830 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
24831 always fails if its second argument is empty. However, the second way of
24832 writing the test makes the logic clearer.
24833
24834
24835 .section "The LOGIN authentication mechanism" "SECID173"
24836 .cindex "LOGIN authentication mechanism"
24837 .cindex "authentication" "LOGIN mechanism"
24838 The LOGIN authentication mechanism is not documented in any RFC, but is in use
24839 in a number of programs. No data is sent with the AUTH command. Instead, a
24840 user name and password are supplied separately, in response to prompts. The
24841 plaintext authenticator can be configured to support this as in this example:
24842 .code
24843 fixed_login:
24844 driver = plaintext
24845 public_name = LOGIN
24846 server_prompts = User Name : Password
24847 server_condition = \
24848 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
24849 server_set_id = $auth1
24850 .endd
24851 Because of the way plaintext operates, this authenticator accepts data supplied
24852 with the AUTH command (in contravention of the specification of LOGIN), but
24853 if the client does not supply it (as is the case for LOGIN clients), the prompt
24854 strings are used to obtain two data items.
24855
24856 Some clients are very particular about the precise text of the prompts. For
24857 example, Outlook Express is reported to recognize only &"Username:"& and
24858 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
24859 strings. It uses the &%ldapauth%& expansion condition to check the user
24860 name and password by binding to an LDAP server:
24861 .code
24862 login:
24863 driver = plaintext
24864 public_name = LOGIN
24865 server_prompts = Username:: : Password::
24866 server_condition = ${if and{{ \
24867 !eq{}{$auth1} }{ \
24868 ldapauth{\
24869 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
24870 pass=${quote:$auth2} \
24871 ldap://ldap.example.org/} }} }
24872 server_set_id = uid=$auth1,ou=people,o=example.org
24873 .endd
24874 We have to check that the username is not empty before using it, because LDAP
24875 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
24876 operator to correctly quote the DN for authentication. However, the basic
24877 &%quote%& operator, rather than any of the LDAP quoting operators, is the
24878 correct one to use for the password, because quoting is needed only to make
24879 the password conform to the Exim syntax. At the LDAP level, the password is an
24880 uninterpreted string.
24881
24882
24883 .section "Support for different kinds of authentication" "SECID174"
24884 A number of string expansion features are provided for the purpose of
24885 interfacing to different ways of user authentication. These include checking
24886 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
24887 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
24888 &<<SECTexpcond>>&.
24889
24890
24891
24892
24893 .section "Using plaintext in a client" "SECID175"
24894 .cindex "options" "&(plaintext)& authenticator (client)"
24895 The &(plaintext)& authenticator has two client options:
24896
24897 .option client_ignore_invalid_base64 plaintext boolean false
24898 If the client receives a server prompt that is not a valid base64 string,
24899 authentication is abandoned by default. However, if this option is set true,
24900 the error in the challenge is ignored and the client sends the response as
24901 usual.
24902
24903 .option client_send plaintext string&!! unset
24904 The string is a colon-separated list of authentication data strings. Each
24905 string is independently expanded before being sent to the server. The first
24906 string is sent with the AUTH command; any more strings are sent in response
24907 to prompts from the server. Before each string is expanded, the value of the
24908 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
24909 with &$auth1$& for the first prompt. Up to three prompts are stored in this
24910 way. Thus, the prompt that is received in response to sending the first string
24911 (with the AUTH command) can be used in the expansion of the second string, and
24912 so on. If an invalid base64 string is received when
24913 &%client_ignore_invalid_base64%& is set, an empty string is put in the
24914 &$auth$&<&'n'&> variable.
24915
24916 &*Note*&: You cannot use expansion to create multiple strings, because
24917 splitting takes priority and happens first.
24918
24919 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
24920 the data, further processing is applied to each string before it is sent. If
24921 there are any single circumflex characters in the string, they are converted to
24922 NULs. Should an actual circumflex be required as data, it must be doubled in
24923 the string.
24924
24925 This is an example of a client configuration that implements the PLAIN
24926 authentication mechanism with a fixed user name and password:
24927 .code
24928 fixed_plain:
24929 driver = plaintext
24930 public_name = PLAIN
24931 client_send = ^username^mysecret
24932 .endd
24933 The lack of colons means that the entire text is sent with the AUTH
24934 command, with the circumflex characters converted to NULs. A similar example
24935 that uses the LOGIN mechanism is:
24936 .code
24937 fixed_login:
24938 driver = plaintext
24939 public_name = LOGIN
24940 client_send = : username : mysecret
24941 .endd
24942 The initial colon means that the first string is empty, so no data is sent with
24943 the AUTH command itself. The remaining strings are sent in response to
24944 prompts.
24945 .ecindex IIDplaiauth1
24946 .ecindex IIDplaiauth2
24947
24948
24949
24950
24951 . ////////////////////////////////////////////////////////////////////////////
24952 . ////////////////////////////////////////////////////////////////////////////
24953
24954 .chapter "The cram_md5 authenticator" "CHID9"
24955 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
24956 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
24957 .cindex "CRAM-MD5 authentication mechanism"
24958 .cindex "authentication" "CRAM-MD5 mechanism"
24959 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
24960 sends a challenge string to the client, and the response consists of a user
24961 name and the CRAM-MD5 digest of the challenge string combined with a secret
24962 string (password) which is known to both server and client. Thus, the secret
24963 is not sent over the network as plain text, which makes this authenticator more
24964 secure than &(plaintext)&. However, the downside is that the secret has to be
24965 available in plain text at either end.
24966
24967
24968 .section "Using cram_md5 as a server" "SECID176"
24969 .cindex "options" "&(cram_md5)& authenticator (server)"
24970 This authenticator has one server option, which must be set to configure the
24971 authenticator as a server:
24972
24973 .option server_secret cram_md5 string&!! unset
24974 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
24975 When the server receives the client's response, the user name is placed in
24976 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
24977 obtain the password for that user. The server then computes the CRAM-MD5 digest
24978 that the client should have sent, and checks that it received the correct
24979 string. If the expansion of &%server_secret%& is forced to fail, authentication
24980 fails. If the expansion fails for some other reason, a temporary error code is
24981 returned to the client.
24982
24983 For compatibility with previous releases of Exim, the user name is also placed
24984 in &$1$&. However, the use of this variables for this purpose is now
24985 deprecated, as it can lead to confusion in string expansions that also use
24986 numeric variables for other things.
24987
24988 For example, the following authenticator checks that the user name given by the
24989 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
24990 user name, authentication fails.
24991 .code
24992 fixed_cram:
24993 driver = cram_md5
24994 public_name = CRAM-MD5
24995 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
24996 server_set_id = $auth1
24997 .endd
24998 .vindex "&$authenticated_id$&"
24999 If authentication succeeds, the setting of &%server_set_id%& preserves the user
25000 name in &$authenticated_id$&. A more typical configuration might look up the
25001 secret string in a file, using the user name as the key. For example:
25002 .code
25003 lookup_cram:
25004 driver = cram_md5
25005 public_name = CRAM-MD5
25006 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
25007 {$value}fail}
25008 server_set_id = $auth1
25009 .endd
25010 Note that this expansion explicitly forces failure if the lookup fails
25011 because &$auth1$& contains an unknown user name.
25012
25013 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
25014 using the relevant libraries, you need to know the realm to specify in the
25015 lookup and then ask for the &"userPassword"& attribute for that user in that
25016 realm, with:
25017 .code
25018 cyrusless_crammd5:
25019 driver = cram_md5
25020 public_name = CRAM-MD5
25021 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
25022 dbmjz{/etc/sasldb2}}
25023 server_set_id = $auth1
25024 .endd
25025
25026 .section "Using cram_md5 as a client" "SECID177"
25027 .cindex "options" "&(cram_md5)& authenticator (client)"
25028 When used as a client, the &(cram_md5)& authenticator has two options:
25029
25030
25031
25032 .option client_name cram_md5 string&!! "the primary host name"
25033 This string is expanded, and the result used as the user name data when
25034 computing the response to the server's challenge.
25035
25036
25037 .option client_secret cram_md5 string&!! unset
25038 This option must be set for the authenticator to work as a client. Its value is
25039 expanded and the result used as the secret string when computing the response.
25040
25041
25042 .vindex "&$host$&"
25043 .vindex "&$host_address$&"
25044 Different user names and secrets can be used for different servers by referring
25045 to &$host$& or &$host_address$& in the options. Forced failure of either
25046 expansion string is treated as an indication that this authenticator is not
25047 prepared to handle this case. Exim moves on to the next configured client
25048 authenticator. Any other expansion failure causes Exim to give up trying to
25049 send the message to the current server.
25050
25051 A simple example configuration of a &(cram_md5)& authenticator, using fixed
25052 strings, is:
25053 .code
25054 fixed_cram:
25055 driver = cram_md5
25056 public_name = CRAM-MD5
25057 client_name = ph10
25058 client_secret = secret
25059 .endd
25060 .ecindex IIDcramauth1
25061 .ecindex IIDcramauth2
25062
25063
25064
25065 . ////////////////////////////////////////////////////////////////////////////
25066 . ////////////////////////////////////////////////////////////////////////////
25067
25068 .chapter "The cyrus_sasl authenticator" "CHID10"
25069 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
25070 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
25071 .cindex "Cyrus" "SASL library"
25072 .cindex "Kerberos"
25073 The code for this authenticator was provided by Matthew Byng-Maddick of A L
25074 Digital Ltd (&url(http://www.aldigital.co.uk)).
25075
25076 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
25077 library implementation of the RFC 2222 (&"Simple Authentication and Security
25078 Layer"&). This library supports a number of authentication mechanisms,
25079 including PLAIN and LOGIN, but also several others that Exim does not support
25080 directly. In particular, there is support for Kerberos authentication.
25081
25082 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
25083 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
25084 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
25085 name of the driver to determine which mechanism to support.
25086
25087 Where access to some kind of secret file is required, for example in GSSAPI
25088 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
25089 user, and that the Cyrus SASL library has no way of escalating privileges
25090 by default. You may also find you need to set environment variables,
25091 depending on the driver you are using.
25092
25093 The application name provided by Exim is &"exim"&, so various SASL options may
25094 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
25095 Kerberos, note that because of limitations in the GSSAPI interface,
25096 changing the server keytab might need to be communicated down to the Kerberos
25097 layer independently. The mechanism for doing so is dependent upon the Kerberos
25098 implementation.
25099
25100 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
25101 may be set to point to an alternative keytab file. Exim will pass this
25102 variable through from its own inherited environment when started as root or the
25103 Exim user. The keytab file needs to be readable by the Exim user.
25104 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
25105 environment variable. In practice, for those releases, the Cyrus authenticator
25106 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
25107 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
25108
25109
25110 .section "Using cyrus_sasl as a server" "SECID178"
25111 The &(cyrus_sasl)& authenticator has four private options. It puts the username
25112 (on a successful authentication) into &$auth1$&. For compatibility with
25113 previous releases of Exim, the username is also placed in &$1$&. However, the
25114 use of this variable for this purpose is now deprecated, as it can lead to
25115 confusion in string expansions that also use numeric variables for other
25116 things.
25117
25118
25119 .option server_hostname cyrus_sasl string&!! "see below"
25120 This option selects the hostname that is used when communicating with the
25121 library. The default value is &`$primary_hostname`&. It is up to the underlying
25122 SASL plug-in what it does with this data.
25123
25124
25125 .option server_mech cyrus_sasl string "see below"
25126 This option selects the authentication mechanism this driver should use. The
25127 default is the value of the generic &%public_name%& option. This option allows
25128 you to use a different underlying mechanism from the advertised name. For
25129 example:
25130 .code
25131 sasl:
25132 driver = cyrus_sasl
25133 public_name = X-ANYTHING
25134 server_mech = CRAM-MD5
25135 server_set_id = $auth1
25136 .endd
25137
25138 .option server_realm cyrus_sasl string&!! unset
25139 This specifies the SASL realm that the server claims to be in.
25140
25141
25142 .option server_service cyrus_sasl string &`smtp`&
25143 This is the SASL service that the server claims to implement.
25144
25145
25146 For straightforward cases, you do not need to set any of the authenticator's
25147 private options. All you need to do is to specify an appropriate mechanism as
25148 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
25149 PLAIN, you could have two authenticators as follows:
25150 .code
25151 sasl_cram_md5:
25152 driver = cyrus_sasl
25153 public_name = CRAM-MD5
25154 server_set_id = $auth1
25155
25156 sasl_plain:
25157 driver = cyrus_sasl
25158 public_name = PLAIN
25159 server_set_id = $auth2
25160 .endd
25161 Cyrus SASL does implement the LOGIN authentication method, even though it is
25162 not a standard method. It is disabled by default in the source distribution,
25163 but it is present in many binary distributions.
25164 .ecindex IIDcyrauth1
25165 .ecindex IIDcyrauth2
25166
25167
25168
25169
25170 . ////////////////////////////////////////////////////////////////////////////
25171 . ////////////////////////////////////////////////////////////////////////////
25172 .chapter "The dovecot authenticator" "CHAPdovecot"
25173 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
25174 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
25175 This authenticator is an interface to the authentication facility of the
25176 Dovecot POP/IMAP server, which can support a number of authentication methods.
25177 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
25178 to use the same mechanisms for SMTP authentication. This is a server
25179 authenticator only. There is only one option:
25180
25181 .option server_socket dovecot string unset
25182
25183 This option must specify the socket that is the interface to Dovecot
25184 authentication. The &%public_name%& option must specify an authentication
25185 mechanism that Dovecot is configured to support. You can have several
25186 authenticators for different mechanisms. For example:
25187 .code
25188 dovecot_plain:
25189 driver = dovecot
25190 public_name = PLAIN
25191 server_socket = /var/run/dovecot/auth-client
25192 server_set_id = $auth2
25193
25194 dovecot_ntlm:
25195 driver = dovecot
25196 public_name = NTLM
25197 server_socket = /var/run/dovecot/auth-client
25198 server_set_id = $auth1
25199 .endd
25200 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
25201 &$received_ip_address$& (that is, the connection is local), the &"secured"&
25202 option is passed in the Dovecot authentication command. If, for a TLS
25203 connection, a client certificate has been verified, the &"valid-client-cert"&
25204 option is passed. When authentication succeeds, the identity of the user
25205 who authenticated is placed in &$auth1$&.
25206 .ecindex IIDdcotauth1
25207 .ecindex IIDdcotauth2
25208
25209
25210 . ////////////////////////////////////////////////////////////////////////////
25211 . ////////////////////////////////////////////////////////////////////////////
25212 .chapter "The gsasl authenticator" "CHAPgsasl"
25213 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
25214 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
25215 .cindex "authentication" "GNU SASL"
25216 .cindex "authentication" "SASL"
25217 .cindex "authentication" "EXTERNAL"
25218 .cindex "authentication" "ANONYMOUS"
25219 .cindex "authentication" "PLAIN"
25220 .cindex "authentication" "LOGIN"
25221 .cindex "authentication" "DIGEST-MD5"
25222 .cindex "authentication" "CRAM-MD5"
25223 .cindex "authentication" "SCRAM-SHA-1"
25224 The &(gsasl)& authenticator provides server integration for the GNU SASL
25225 library and the mechanisms it provides. This is new as of the 4.80 release
25226 and there are a few areas where the library does not let Exim smoothly
25227 scale to handle future authentication mechanisms, so no guarantee can be
25228 made that any particular new authentication mechanism will be supported
25229 without code changes in Exim.
25230
25231
25232 .option server_channelbinding gsasl boolean false
25233 Some authentication mechanisms are able to use external context at both ends
25234 of the session to bind the authentication to that context, and fail the
25235 authentication process if that context differs. Specifically, some TLS
25236 ciphersuites can provide identifying information about the cryptographic
25237 context.
25238
25239 This means that certificate identity and verification becomes a non-issue,
25240 as a man-in-the-middle attack will cause the correct client and server to
25241 see different identifiers and authentication will fail.
25242
25243 This is currently only supported when using the GnuTLS library. This is
25244 only usable by mechanisms which support "channel binding"; at time of
25245 writing, that's the SCRAM family.
25246
25247 This defaults off to ensure smooth upgrade across Exim releases, in case
25248 this option causes some clients to start failing. Some future release
25249 of Exim may switch the default to be true.
25250
25251
25252 .option server_hostname gsasl string&!! "see below"
25253 This option selects the hostname that is used when communicating with the
25254 library. The default value is &`$primary_hostname`&.
25255 Some mechanisms will use this data.
25256
25257
25258 .option server_mech gsasl string "see below"
25259 This option selects the authentication mechanism this driver should use. The
25260 default is the value of the generic &%public_name%& option. This option allows
25261 you to use a different underlying mechanism from the advertised name. For
25262 example:
25263 .code
25264 sasl:
25265 driver = gsasl
25266 public_name = X-ANYTHING
25267 server_mech = CRAM-MD5
25268 server_set_id = $auth1
25269 .endd
25270
25271
25272 .option server_password gsasl string&!! unset
25273 Various mechanisms need access to the cleartext password on the server, so
25274 that proof-of-possession can be demonstrated on the wire, without sending
25275 the password itself.
25276
25277 The data available for lookup varies per mechanism.
25278 In all cases, &$auth1$& is set to the &'authentication id'&.
25279 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
25280 if available, else the empty string.
25281 The &$auth3$& variable will always be the &'realm'& if available,
25282 else the empty string.
25283
25284 A forced failure will cause authentication to defer.
25285
25286 If using this option, it may make sense to set the &%server_condition%&
25287 option to be simply "true".
25288
25289
25290 .option server_realm gsasl string&!! unset
25291 This specifies the SASL realm that the server claims to be in.
25292 Some mechanisms will use this data.
25293
25294
25295 .option server_scram_iter gsasl string&!! unset
25296 This option provides data for the SCRAM family of mechanisms.
25297 &$auth1$& is not available at evaluation time.
25298 (This may change, as we receive feedback on use)
25299
25300
25301 .option server_scram_salt gsasl string&!! unset
25302 This option provides data for the SCRAM family of mechanisms.
25303 &$auth1$& is not available at evaluation time.
25304 (This may change, as we receive feedback on use)
25305
25306
25307 .option server_service gsasl string &`smtp`&
25308 This is the SASL service that the server claims to implement.
25309 Some mechanisms will use this data.
25310
25311
25312 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
25313 .vindex "&$auth1$&, &$auth2$&, etc"
25314 These may be set when evaluating specific options, as detailed above.
25315 They will also be set when evaluating &%server_condition%&.
25316
25317 Unless otherwise stated below, the &(gsasl)& integration will use the following
25318 meanings for these variables:
25319
25320 .ilist
25321 .vindex "&$auth1$&"
25322 &$auth1$&: the &'authentication id'&
25323 .next
25324 .vindex "&$auth2$&"
25325 &$auth2$&: the &'authorization id'&
25326 .next
25327 .vindex "&$auth3$&"
25328 &$auth3$&: the &'realm'&
25329 .endlist
25330
25331 On a per-mechanism basis:
25332
25333 .ilist
25334 .cindex "authentication" "EXTERNAL"
25335 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
25336 the &%server_condition%& option must be present.
25337 .next
25338 .cindex "authentication" "ANONYMOUS"
25339 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
25340 the &%server_condition%& option must be present.
25341 .next
25342 .cindex "authentication" "GSSAPI"
25343 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
25344 &$auth2$& will be set to the &'authorization id'&,
25345 the &%server_condition%& option must be present.
25346 .endlist
25347
25348 An &'anonymous token'& is something passed along as an unauthenticated
25349 identifier; this is analogous to FTP anonymous authentication passing an
25350 email address, or software-identifier@, as the "password".
25351
25352
25353 An example showing the password having the realm specified in the callback
25354 and demonstrating a Cyrus SASL to GSASL migration approach is:
25355 .code
25356 gsasl_cyrusless_crammd5:
25357 driver = gsasl
25358 public_name = CRAM-MD5
25359 server_realm = imap.example.org
25360 server_password = ${lookup{$auth1:$auth3:userPassword}\
25361 dbmjz{/etc/sasldb2}{$value}fail}
25362 server_set_id = ${quote:$auth1}
25363 server_condition = yes
25364 .endd
25365
25366
25367 . ////////////////////////////////////////////////////////////////////////////
25368 . ////////////////////////////////////////////////////////////////////////////
25369
25370 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
25371 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
25372 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
25373 .cindex "authentication" "GSSAPI"
25374 .cindex "authentication" "Kerberos"
25375 The &(heimdal_gssapi)& authenticator provides server integration for the
25376 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
25377 reliably.
25378
25379 .option server_hostname heimdal_gssapi string&!! "see below"
25380 This option selects the hostname that is used, with &%server_service%&,
25381 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
25382 identifier. The default value is &`$primary_hostname`&.
25383
25384 .option server_keytab heimdal_gssapi string&!! unset
25385 If set, then Heimdal will not use the system default keytab (typically
25386 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
25387 The value should be a pathname, with no &"file:"& prefix.
25388
25389 .option server_service heimdal_gssapi string&!! "smtp"
25390 This option specifies the service identifier used, in conjunction with
25391 &%server_hostname%&, for building the identifer for finding credentials
25392 from the keytab.
25393
25394
25395 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
25396 Beware that these variables will typically include a realm, thus will appear
25397 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
25398 not verified, so a malicious client can set it to anything.
25399
25400 The &$auth1$& field should be safely trustable as a value from the Key
25401 Distribution Center. Note that these are not quite email addresses.
25402 Each identifier is for a role, and so the left-hand-side may include a
25403 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
25404
25405 .vindex "&$auth1$&, &$auth2$&, etc"
25406 .ilist
25407 .vindex "&$auth1$&"
25408 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
25409 .next
25410 .vindex "&$auth2$&"
25411 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
25412 authentication. If that was empty, this will also be set to the
25413 GSS Display Name.
25414 .endlist
25415
25416
25417 . ////////////////////////////////////////////////////////////////////////////
25418 . ////////////////////////////////////////////////////////////////////////////
25419
25420 .chapter "The spa authenticator" "CHAPspa"
25421 .scindex IIDspaauth1 "&(spa)& authenticator"
25422 .scindex IIDspaauth2 "authenticators" "&(spa)&"
25423 .cindex "authentication" "Microsoft Secure Password"
25424 .cindex "authentication" "NTLM"
25425 .cindex "Microsoft Secure Password Authentication"
25426 .cindex "NTLM authentication"
25427 The &(spa)& authenticator provides client support for Microsoft's &'Secure
25428 Password Authentication'& mechanism,
25429 which is also sometimes known as NTLM (NT LanMan). The code for client side of
25430 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
25431 taken from the Samba project (&url(http://www.samba.org)). The code for the
25432 server side was subsequently contributed by Tom Kistner. The mechanism works as
25433 follows:
25434
25435 .ilist
25436 After the AUTH command has been accepted, the client sends an SPA
25437 authentication request based on the user name and optional domain.
25438 .next
25439 The server sends back a challenge.
25440 .next
25441 The client builds a challenge response which makes use of the user's password
25442 and sends it to the server, which then accepts or rejects it.
25443 .endlist
25444
25445 Encryption is used to protect the password in transit.
25446
25447
25448
25449 .section "Using spa as a server" "SECID179"
25450 .cindex "options" "&(spa)& authenticator (server)"
25451 The &(spa)& authenticator has just one server option:
25452
25453 .option server_password spa string&!! unset
25454 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
25455 This option is expanded, and the result must be the cleartext password for the
25456 authenticating user, whose name is at this point in &$auth1$&. For
25457 compatibility with previous releases of Exim, the user name is also placed in
25458 &$1$&. However, the use of this variable for this purpose is now deprecated, as
25459 it can lead to confusion in string expansions that also use numeric variables
25460 for other things. For example:
25461 .code
25462 spa:
25463 driver = spa
25464 public_name = NTLM
25465 server_password = \
25466 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
25467 .endd
25468 If the expansion is forced to fail, authentication fails. Any other expansion
25469 failure causes a temporary error code to be returned.
25470
25471
25472
25473
25474
25475 .section "Using spa as a client" "SECID180"
25476 .cindex "options" "&(spa)& authenticator (client)"
25477 The &(spa)& authenticator has the following client options:
25478
25479
25480
25481 .option client_domain spa string&!! unset
25482 This option specifies an optional domain for the authentication.
25483
25484
25485 .option client_password spa string&!! unset
25486 This option specifies the user's password, and must be set.
25487
25488
25489 .option client_username spa string&!! unset
25490 This option specifies the user name, and must be set. Here is an example of a
25491 configuration of this authenticator for use with the mail servers at
25492 &'msn.com'&:
25493 .code
25494 msn:
25495 driver = spa
25496 public_name = MSN
25497 client_username = msn/msn_username
25498 client_password = msn_plaintext_password
25499 client_domain = DOMAIN_OR_UNSET
25500 .endd
25501 .ecindex IIDspaauth1
25502 .ecindex IIDspaauth2
25503
25504
25505
25506
25507
25508 . ////////////////////////////////////////////////////////////////////////////
25509 . ////////////////////////////////////////////////////////////////////////////
25510
25511 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
25512 "Encrypted SMTP connections"
25513 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
25514 .scindex IIDencsmtp2 "SMTP" "encryption"
25515 .cindex "TLS" "on SMTP connection"
25516 .cindex "OpenSSL"
25517 .cindex "GnuTLS"
25518 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
25519 Sockets Layer), is implemented by making use of the OpenSSL library or the
25520 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
25521 cryptographic code in the Exim distribution itself for implementing TLS. In
25522 order to use this feature you must install OpenSSL or GnuTLS, and then build a
25523 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
25524 You also need to understand the basic concepts of encryption at a managerial
25525 level, and in particular, the way that public keys, private keys, and
25526 certificates are used.
25527
25528 RFC 3207 defines how SMTP connections can make use of encryption. Once a
25529 connection is established, the client issues a STARTTLS command. If the
25530 server accepts this, the client and the server negotiate an encryption
25531 mechanism. If the negotiation succeeds, the data that subsequently passes
25532 between them is encrypted.
25533
25534 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
25535 and if so, what cipher suite is in use, whether the client supplied a
25536 certificate, and whether or not that certificate was verified. This makes it
25537 possible for an Exim server to deny or accept certain commands based on the
25538 encryption state.
25539
25540 &*Warning*&: Certain types of firewall and certain anti-virus products can
25541 disrupt TLS connections. You need to turn off SMTP scanning for these products
25542 in order to get TLS to work.
25543
25544
25545
25546 .section "Support for the legacy &""ssmtp""& (aka &""smtps""&) protocol" &&&
25547 "SECID284"
25548 .cindex "ssmtp protocol"
25549 .cindex "smtps protocol"
25550 .cindex "SMTP" "ssmtp protocol"
25551 .cindex "SMTP" "smtps protocol"
25552 Early implementations of encrypted SMTP used a different TCP port from normal
25553 SMTP, and expected an encryption negotiation to start immediately, instead of
25554 waiting for a STARTTLS command from the client using the standard SMTP
25555 port. The protocol was called &"ssmtp"& or &"smtps"&, and port 465 was
25556 allocated for this purpose.
25557
25558 This approach was abandoned when encrypted SMTP was standardized, but there are
25559 still some legacy clients that use it. Exim supports these clients by means of
25560 the &%tls_on_connect_ports%& global option. Its value must be a list of port
25561 numbers; the most common use is expected to be:
25562 .code
25563 tls_on_connect_ports = 465
25564 .endd
25565 The port numbers specified by this option apply to all SMTP connections, both
25566 via the daemon and via &'inetd'&. You still need to specify all the ports that
25567 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
25568 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
25569 an extra port &-- rather, it specifies different behaviour on a port that is
25570 defined elsewhere.
25571
25572 There is also a &%-tls-on-connect%& command line option. This overrides
25573 &%tls_on_connect_ports%&; it forces the legacy behaviour for all ports.
25574
25575
25576
25577
25578
25579
25580 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
25581 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
25582 The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
25583 followed later, when the first versions of GnuTLS were released. To build Exim
25584 to use GnuTLS, you need to set
25585 .code
25586 USE_GNUTLS=yes
25587 .endd
25588 in Local/Makefile, in addition to
25589 .code
25590 SUPPORT_TLS=yes
25591 .endd
25592 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
25593 include files and libraries for GnuTLS can be found.
25594
25595 There are some differences in usage when using GnuTLS instead of OpenSSL:
25596
25597 .ilist
25598 The &%tls_verify_certificates%& option must contain the name of a file, not the
25599 name of a directory (for OpenSSL it can be either).
25600 .next
25601 The default value for &%tls_dhparam%& differs for historical reasons.
25602 .next
25603 .vindex "&$tls_in_peerdn$&"
25604 .vindex "&$tls_out_peerdn$&"
25605 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
25606 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
25607 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
25608 .next
25609 OpenSSL identifies cipher suites using hyphens as separators, for example:
25610 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
25611 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
25612 in a cipher list. To make life simpler, Exim changes underscores to hyphens
25613 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
25614 to handle its own older variants) when processing lists of cipher suites in the
25615 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
25616 option).
25617 .next
25618 The &%tls_require_ciphers%& options operate differently, as described in the
25619 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
25620 .next
25621 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
25622 When using OpenSSL, this option is ignored.
25623 (If an API is found to let OpenSSL be configured in this way,
25624 let the Exim Maintainers know and we'll likely use it).
25625 .next
25626 Some other recently added features may only be available in one or the other.
25627 This should be documented with the feature. If the documentation does not
25628 explicitly state that the feature is infeasible in the other TLS
25629 implementation, then patches are welcome.
25630 .endlist
25631
25632
25633 .section "GnuTLS parameter computation" "SECTgnutlsparam"
25634 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
25635 an explicit path; if the latter, then the text about generation still applies,
25636 but not the chosen filename.
25637 By default, as of Exim 4.80 a hard-coded D-H prime is used.
25638 See the documentation of &%tls_dhparam%& for more information.
25639
25640 GnuTLS uses D-H parameters that may take a substantial amount of time
25641 to compute. It is unreasonable to re-compute them for every TLS session.
25642 Therefore, Exim keeps this data in a file in its spool directory, called
25643 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
25644 of bits requested.
25645 The file is owned by the Exim user and is readable only by
25646 its owner. Every Exim process that start up GnuTLS reads the D-H
25647 parameters from this file. If the file does not exist, the first Exim process
25648 that needs it computes the data and writes it to a temporary file which is
25649 renamed once it is complete. It does not matter if several Exim processes do
25650 this simultaneously (apart from wasting a few resources). Once a file is in
25651 place, new Exim processes immediately start using it.
25652
25653 For maximum security, the parameters that are stored in this file should be
25654 recalculated periodically, the frequency depending on your paranoia level.
25655 If you are avoiding using the fixed D-H primes published in RFCs, then you
25656 are concerned about some advanced attacks and will wish to do this; if you do
25657 not regenerate then you might as well stick to the standard primes.
25658
25659 Arranging this is easy in principle; just delete the file when you want new
25660 values to be computed. However, there may be a problem. The calculation of new
25661 parameters needs random numbers, and these are obtained from &_/dev/random_&.
25662 If the system is not very active, &_/dev/random_& may delay returning data
25663 until enough randomness (entropy) is available. This may cause Exim to hang for
25664 a substantial amount of time, causing timeouts on incoming connections.
25665
25666 The solution is to generate the parameters externally to Exim. They are stored
25667 in &_gnutls-params-N_& in PEM format, which means that they can be
25668 generated externally using the &(certtool)& command that is part of GnuTLS.
25669
25670 To replace the parameters with new ones, instead of deleting the file
25671 and letting Exim re-create it, you can generate new parameters using
25672 &(certtool)& and, when this has been done, replace Exim's cache file by
25673 renaming. The relevant commands are something like this:
25674 .code
25675 # ls
25676 [ look for file; assume gnutls-params-2236 is the most recent ]
25677 # rm -f new-params
25678 # touch new-params
25679 # chown exim:exim new-params
25680 # chmod 0600 new-params
25681 # certtool --generate-dh-params --bits 2236 >>new-params
25682 # openssl dhparam -noout -text -in new-params | head
25683 [ check the first line, make sure it's not more than 2236;
25684 if it is, then go back to the start ("rm") and repeat
25685 until the size generated is at most the size requested ]
25686 # chmod 0400 new-params
25687 # mv new-params gnutls-params-2236
25688 .endd
25689 If Exim never has to generate the parameters itself, the possibility of
25690 stalling is removed.
25691
25692 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
25693 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
25694 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
25695 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
25696 and Exim does so. This attempt to remove Exim from TLS policy decisions
25697 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
25698 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
25699 which applies to all D-H usage, client or server. If the value returned by
25700 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
25701 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
25702 limit, which is still much higher than Exim historically used.
25703
25704 The filename and bits used will change as the GnuTLS maintainers change the
25705 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
25706 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
25707 2432 bits, while NSS is limited to 2236 bits.
25708
25709 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
25710 increase the chance of the generated prime actually being within acceptable
25711 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
25712 procedure above. There is no sane procedure available to Exim to double-check
25713 the size of the generated prime, so it might still be too large.
25714
25715
25716 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
25717 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
25718 .oindex "&%tls_require_ciphers%&" "OpenSSL"
25719 There is a function in the OpenSSL library that can be passed a list of cipher
25720 suites before the cipher negotiation takes place. This specifies which ciphers
25721 are acceptable. The list is colon separated and may contain names like
25722 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
25723 directly to this function call.
25724 Many systems will install the OpenSSL manual-pages, so you may have
25725 &'ciphers(1)'& available to you.
25726 The following quotation from the OpenSSL
25727 documentation specifies what forms of item are allowed in the cipher string:
25728
25729 .ilist
25730 It can consist of a single cipher suite such as RC4-SHA.
25731 .next
25732 It can represent a list of cipher suites containing a certain algorithm,
25733 or cipher suites of a certain type. For example SHA1 represents all
25734 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
25735 SSL v3 algorithms.
25736 .next
25737 Lists of cipher suites can be combined in a single cipher string using
25738 the + character. This is used as a logical and operation. For example
25739 SHA1+DES represents all cipher suites containing the SHA1 and the DES
25740 algorithms.
25741 .endlist
25742
25743 Each cipher string can be optionally preceded by one of the characters &`!`&,
25744 &`-`& or &`+`&.
25745 .ilist
25746 If &`!`& is used, the ciphers are permanently deleted from the list. The
25747 ciphers deleted can never reappear in the list even if they are explicitly
25748 stated.
25749 .next
25750 If &`-`& is used, the ciphers are deleted from the list, but some or all
25751 of the ciphers can be added again by later options.
25752 .next
25753 If &`+`& is used, the ciphers are moved to the end of the list. This
25754 option does not add any new ciphers; it just moves matching existing ones.
25755 .endlist
25756
25757 If none of these characters is present, the string is interpreted as
25758 a list of ciphers to be appended to the current preference list. If the list
25759 includes any ciphers already present they will be ignored: that is, they will
25760 not be moved to the end of the list.
25761 .endlist
25762
25763 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
25764 string:
25765 .code
25766 # note single-quotes to get ! past any shell history expansion
25767 $ openssl ciphers 'HIGH:!MD5:!SHA1'
25768 .endd
25769
25770 This example will let the library defaults be permitted on the MX port, where
25771 there's probably no identity verification anyway, but ups the ante on the
25772 submission ports where the administrator might have some influence on the
25773 choice of clients used:
25774 .code
25775 # OpenSSL variant; see man ciphers(1)
25776 tls_require_ciphers = ${if =={$received_port}{25}\
25777 {DEFAULT}\
25778 {HIGH:!MD5:!SHA1}}
25779 .endd
25780
25781
25782
25783 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
25784 "SECTreqciphgnu"
25785 .cindex "GnuTLS" "specifying parameters for"
25786 .cindex "TLS" "specifying ciphers (GnuTLS)"
25787 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
25788 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
25789 .cindex "TLS" "specifying protocols (GnuTLS)"
25790 .cindex "TLS" "specifying priority string (GnuTLS)"
25791 .oindex "&%tls_require_ciphers%&" "GnuTLS"
25792 The GnuTLS library allows the caller to provide a "priority string", documented
25793 as part of the &[gnutls_priority_init]& function. This is very similar to the
25794 ciphersuite specification in OpenSSL.
25795
25796 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string.
25797
25798 The &%tls_require_ciphers%& option is available both as an global option,
25799 controlling how Exim behaves as a server, and also as an option of the
25800 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
25801 the value is string expanded. The resulting string is not an Exim list and
25802 the string is given to the GnuTLS library, so that Exim does not need to be
25803 aware of future feature enhancements of GnuTLS.
25804
25805 Documentation of the strings accepted may be found in the GnuTLS manual, under
25806 "Priority strings". This is online as
25807 &url(http://www.gnutls.org/manual/html_node/Priority-Strings.html),
25808 but beware that this relates to GnuTLS 3, which may be newer than the version
25809 installed on your system. If you are using GnuTLS 3,
25810 &url(http://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string, then the example code)
25811 on that site can be used to test a given string.
25812
25813 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
25814 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
25815 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
25816
25817 This example will let the library defaults be permitted on the MX port, where
25818 there's probably no identity verification anyway, and lowers security further
25819 by increasing compatibility; but this ups the ante on the submission ports
25820 where the administrator might have some influence on the choice of clients
25821 used:
25822 .code
25823 # GnuTLS variant
25824 tls_require_ciphers = ${if =={$received_port}{25}\
25825 {NORMAL:%COMPAT}\
25826 {SECURE128}}
25827 .endd
25828
25829
25830 .section "Configuring an Exim server to use TLS" "SECID182"
25831 .cindex "TLS" "configuring an Exim server"
25832 When Exim has been built with TLS support, it advertises the availability of
25833 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
25834 but not to any others. The default value of this option is unset, which means
25835 that STARTTLS is not advertised at all. This default is chosen because you
25836 need to set some other options in order to make TLS available, and also it is
25837 sensible for systems that want to use TLS only as a client.
25838
25839 If a client issues a STARTTLS command and there is some configuration
25840 problem in the server, the command is rejected with a 454 error. If the client
25841 persists in trying to issue SMTP commands, all except QUIT are rejected
25842 with the error
25843 .code
25844 554 Security failure
25845 .endd
25846 If a STARTTLS command is issued within an existing TLS session, it is
25847 rejected with a 554 error code.
25848
25849 To enable TLS operations on a server, you must set &%tls_advertise_hosts%& to
25850 match some hosts. You can, of course, set it to * to match all hosts.
25851 However, this is not all you need to do. TLS sessions to a server won't work
25852 without some further configuration at the server end.
25853
25854 It is rumoured that all existing clients that support TLS/SSL use RSA
25855 encryption. To make this work you need to set, in the server,
25856 .code
25857 tls_certificate = /some/file/name
25858 tls_privatekey = /some/file/name
25859 .endd
25860 These options are, in fact, expanded strings, so you can make them depend on
25861 the identity of the client that is connected if you wish. The first file
25862 contains the server's X509 certificate, and the second contains the private key
25863 that goes with it. These files need to be readable by the Exim user, and must
25864 always be given as full path names. They can be the same file if both the
25865 certificate and the key are contained within it. If &%tls_privatekey%& is not
25866 set, or if its expansion is forced to fail or results in an empty string, this
25867 is assumed to be the case. The certificate file may also contain intermediate
25868 certificates that need to be sent to the client to enable it to authenticate
25869 the server's certificate.
25870
25871 If you do not understand about certificates and keys, please try to find a
25872 source of this background information, which is not Exim-specific. (There are a
25873 few comments below in section &<<SECTcerandall>>&.)
25874
25875 &*Note*&: These options do not apply when Exim is operating as a client &--
25876 they apply only in the case of a server. If you need to use a certificate in an
25877 Exim client, you must set the options of the same names in an &(smtp)&
25878 transport.
25879
25880 With just these options, an Exim server will be able to use TLS. It does not
25881 require the client to have a certificate (but see below for how to insist on
25882 this). There is one other option that may be needed in other situations. If
25883 .code
25884 tls_dhparam = /some/file/name
25885 .endd
25886 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
25887 with the parameters contained in the file.
25888 Set this to &`none`& to disable use of DH entirely, by making no prime
25889 available:
25890 .code
25891 tls_dhparam = none
25892 .endd
25893 This may also be set to a string identifying a standard prime to be used for
25894 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
25895 used is &`ike23`&. There are a few standard primes available, see the
25896 documentation for &%tls_dhparam%& for the complete list.
25897
25898 See the command
25899 .code
25900 openssl dhparam
25901 .endd
25902 for a way of generating file data.
25903
25904 The strings supplied for these three options are expanded every time a client
25905 host connects. It is therefore possible to use different certificates and keys
25906 for different hosts, if you so wish, by making use of the client's IP address
25907 in &$sender_host_address$& to control the expansion. If a string expansion is
25908 forced to fail, Exim behaves as if the option is not set.
25909
25910 .cindex "cipher" "logging"
25911 .cindex "log" "TLS cipher"
25912 .vindex "&$tls_in_cipher$&"
25913 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
25914 an incoming TLS connection. It is included in the &'Received:'& header of an
25915 incoming message (by default &-- you can, of course, change this), and it is
25916 also included in the log line that records a message's arrival, keyed by
25917 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
25918 condition can be used to test for specific cipher suites in ACLs.
25919
25920 Once TLS has been established, the ACLs that run for subsequent SMTP commands
25921 can check the name of the cipher suite and vary their actions accordingly. The
25922 cipher suite names vary, depending on which TLS library is being used. For
25923 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
25924 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
25925 documentation for more details.
25926
25927 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
25928 (again depending on the &%tls_cipher%& log selector).
25929
25930
25931 .section "Requesting and verifying client certificates" "SECID183"
25932 .cindex "certificate" "verification of client"
25933 .cindex "TLS" "client certificate verification"
25934 If you want an Exim server to request a certificate when negotiating a TLS
25935 session with a client, you must set either &%tls_verify_hosts%& or
25936 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
25937 apply to all TLS connections. For any host that matches one of these options,
25938 Exim requests a certificate as part of the setup of the TLS session. The
25939 contents of the certificate are verified by comparing it with a list of
25940 expected certificates. These must be available in a file or,
25941 for OpenSSL only (not GnuTLS), a directory, identified by
25942 &%tls_verify_certificates%&.
25943
25944 A file can contain multiple certificates, concatenated end to end. If a
25945 directory is used
25946 (OpenSSL only),
25947 each certificate must be in a separate file, with a name (or a symbolic link)
25948 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
25949 certificate. You can compute the relevant hash by running the command
25950 .code
25951 openssl x509 -hash -noout -in /cert/file
25952 .endd
25953 where &_/cert/file_& contains a single certificate.
25954
25955 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
25956 what happens if the client does not supply a certificate, or if the certificate
25957 does not match any of the certificates in the collection named by
25958 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
25959 attempt to set up a TLS session is aborted, and the incoming connection is
25960 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
25961 session continues. ACLs that run for subsequent SMTP commands can detect the
25962 fact that no certificate was verified, and vary their actions accordingly. For
25963 example, you can insist on a certificate before accepting a message for
25964 relaying, but not when the message is destined for local delivery.
25965
25966 .vindex "&$tls_in_peerdn$&"
25967 When a client supplies a certificate (whether it verifies or not), the value of
25968 the Distinguished Name of the certificate is made available in the variable
25969 &$tls_in_peerdn$& during subsequent processing of the message.
25970
25971 .cindex "log" "distinguished name"
25972 Because it is often a long text string, it is not included in the log line or
25973 &'Received:'& header by default. You can arrange for it to be logged, keyed by
25974 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
25975 &%received_header_text%& to change the &'Received:'& header. When no
25976 certificate is supplied, &$tls_in_peerdn$& is empty.
25977
25978
25979 .section "Revoked certificates" "SECID184"
25980 .cindex "TLS" "revoked certificates"
25981 .cindex "revocation list"
25982 .cindex "certificate" "revocation list"
25983 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
25984 certificates are revoked. If you have such a list, you can pass it to an Exim
25985 server using the global option called &%tls_crl%& and to an Exim client using
25986 an identically named option for the &(smtp)& transport. In each case, the value
25987 of the option is expanded and must then be the name of a file that contains a
25988 CRL in PEM format.
25989
25990
25991 .section "Configuring an Exim client to use TLS" "SECID185"
25992 .cindex "cipher" "logging"
25993 .cindex "log" "TLS cipher"
25994 .cindex "log" "distinguished name"
25995 .cindex "TLS" "configuring an Exim client"
25996 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
25997 deliveries as well as to incoming, the latter one causing logging of the
25998 server certificate's DN. The remaining client configuration for TLS is all
25999 within the &(smtp)& transport.
26000
26001 It is not necessary to set any options to have TLS work in the &(smtp)&
26002 transport. If Exim is built with TLS support, and TLS is advertised by a
26003 server, the &(smtp)& transport always tries to start a TLS session. However,
26004 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
26005 transport) to a list of server hosts for which TLS should not be used.
26006
26007 If you do not want Exim to attempt to send messages unencrypted when an attempt
26008 to set up an encrypted connection fails in any way, you can set
26009 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
26010 those hosts, delivery is always deferred if an encrypted connection cannot be
26011 set up. If there are any other hosts for the address, they are tried in the
26012 usual way.
26013
26014 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
26015 the message unencrypted. It always does this if the response to STARTTLS is
26016 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
26017 session after a success response code, what happens is controlled by the
26018 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
26019 delivery to this host is deferred, and other hosts (if available) are tried. If
26020 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
26021 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
26022 negotiation fails, Exim closes the current connection (because it is in an
26023 unknown state), opens a new one to the same host, and then tries the delivery
26024 unencrypted.
26025
26026 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
26027 transport provide the client with a certificate, which is passed to the server
26028 if it requests it. If the server is Exim, it will request a certificate only if
26029 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
26030
26031 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
26032 must name a file or,
26033 for OpenSSL only (not GnuTLS), a directory, that contains a collection of
26034 expected server certificates. The client verifies the server's certificate
26035 against this collection, taking into account any revoked certificates that are
26036 in the list defined by &%tls_crl%&.
26037 Failure to verify fails the TLS connection unless either of the
26038 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
26039
26040 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
26041 certificate verification to the listed servers. Verification either must
26042 or need not succeed respectively.
26043
26044 If
26045 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
26046 list of permitted cipher suites. If either of these checks fails, delivery to
26047 the current host is abandoned, and the &(smtp)& transport tries to deliver to
26048 alternative hosts, if any.
26049
26050 &*Note*&:
26051 These options must be set in the &(smtp)& transport for Exim to use TLS when it
26052 is operating as a client. Exim does not assume that a server certificate (set
26053 by the global options of the same name) should also be used when operating as a
26054 client.
26055
26056 .vindex "&$host$&"
26057 .vindex "&$host_address$&"
26058 All the TLS options in the &(smtp)& transport are expanded before use, with
26059 &$host$& and &$host_address$& containing the name and address of the server to
26060 which the client is connected. Forced failure of an expansion causes Exim to
26061 behave as if the relevant option were unset.
26062
26063 .vindex &$tls_out_bits$&
26064 .vindex &$tls_out_cipher$&
26065 .vindex &$tls_out_peerdn$&
26066 .vindex &$tls_out_sni$&
26067 Before an SMTP connection is established, the
26068 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
26069 variables are emptied. (Until the first connection, they contain the values
26070 that were set when the message was received.) If STARTTLS is subsequently
26071 successfully obeyed, these variables are set to the relevant values for the
26072 outgoing connection.
26073
26074
26075
26076 .section "Use of TLS Server Name Indication" "SECTtlssni"
26077 .cindex "TLS" "Server Name Indication"
26078 .vindex "&$tls_in_sni$&"
26079 .oindex "&%tls_in_sni%&"
26080 With TLS1.0 or above, there is an extension mechanism by which extra
26081 information can be included at various points in the protocol. One of these
26082 extensions, documented in RFC 6066 (and before that RFC 4366) is
26083 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
26084 client in the initial handshake, so that the server can examine the servername
26085 within and possibly choose to use different certificates and keys (and more)
26086 for this session.
26087
26088 This is analagous to HTTP's &"Host:"& header, and is the main mechanism by
26089 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
26090 address.
26091
26092 With SMTP to MX, there are the same problems here as in choosing the identity
26093 against which to validate a certificate: you can't rely on insecure DNS to
26094 provide the identity which you then cryptographically verify. So this will
26095 be of limited use in that environment.
26096
26097 With SMTP to Submission, there is a well-defined hostname which clients are
26098 connecting to and can validate certificates against. Thus clients &*can*&
26099 choose to include this information in the TLS negotiation. If this becomes
26100 wide-spread, then hosters can choose to present different certificates to
26101 different clients. Or even negotiate different cipher suites.
26102
26103 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
26104 if not empty, will be sent on a TLS session as part of the handshake. There's
26105 nothing more to it. Choosing a sensible value not derived insecurely is the
26106 only point of caution. The &$tls_out_sni$& variable will be set to this string
26107 for the lifetime of the client connection (including during authentication).
26108
26109 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
26110 received from a client.
26111 It can be logged with the &%log_selector%& item &`+tls_sni`&.
26112
26113 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
26114 option (prior to expansion) then the following options will be re-expanded
26115 during TLS session handshake, to permit alternative values to be chosen:
26116
26117 .ilist
26118 .vindex "&%tls_certificate%&"
26119 &%tls_certificate%&
26120 .next
26121 .vindex "&%tls_crl%&"
26122 &%tls_crl%&
26123 .next
26124 .vindex "&%tls_privatekey%&"
26125 &%tls_privatekey%&
26126 .next
26127 .vindex "&%tls_verify_certificates%&"
26128 &%tls_verify_certificates%&
26129 .endlist
26130
26131 Great care should be taken to deal with matters of case, various injection
26132 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
26133 can always be referenced; it is important to remember that &$tls_sni$& is
26134 arbitrary unverified data provided prior to authentication.
26135
26136 The Exim developers are proceeding cautiously and so far no other TLS options
26137 are re-expanded.
26138
26139 When Exim is built againt OpenSSL, OpenSSL must have been built with support
26140 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
26141 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
26142 see &`-servername`& in the output, then OpenSSL has support.
26143
26144 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
26145 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
26146 built, then you have SNI support).
26147
26148
26149
26150 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
26151 "SECTmulmessam"
26152 .cindex "multiple SMTP deliveries with TLS"
26153 .cindex "TLS" "multiple message deliveries"
26154 Exim sends multiple messages down the same TCP/IP connection by starting up
26155 an entirely new delivery process for each message, passing the socket from
26156 one process to the next. This implementation does not fit well with the use
26157 of TLS, because there is quite a lot of state information associated with a TLS
26158 connection, not just a socket identification. Passing all the state information
26159 to a new process is not feasible. Consequently, Exim shuts down an existing TLS
26160 session before passing the socket to a new process. The new process may then
26161 try to start a new TLS session, and if successful, may try to re-authenticate
26162 if AUTH is in use, before sending the next message.
26163
26164 The RFC is not clear as to whether or not an SMTP session continues in clear
26165 after TLS has been shut down, or whether TLS may be restarted again later, as
26166 just described. However, if the server is Exim, this shutdown and
26167 reinitialization works. It is not known which (if any) other servers operate
26168 successfully if the client closes a TLS session and continues with unencrypted
26169 SMTP, but there are certainly some that do not work. For such servers, Exim
26170 should not pass the socket to another process, because the failure of the
26171 subsequent attempt to use it would cause Exim to record a temporary host error,
26172 and delay other deliveries to that host.
26173
26174 To test for this case, Exim sends an EHLO command to the server after
26175 closing down the TLS session. If this fails in any way, the connection is
26176 closed instead of being passed to a new delivery process, but no retry
26177 information is recorded.
26178
26179 There is also a manual override; you can set &%hosts_nopass_tls%& on the
26180 &(smtp)& transport to match those hosts for which Exim should not pass
26181 connections to new processes if TLS has been used.
26182
26183
26184
26185
26186 .section "Certificates and all that" "SECTcerandall"
26187 .cindex "certificate" "references to discussion"
26188 In order to understand fully how TLS works, you need to know about
26189 certificates, certificate signing, and certificate authorities. This is not the
26190 place to give a tutorial, especially as I do not know very much about it
26191 myself. Some helpful introduction can be found in the FAQ for the SSL addition
26192 to Apache, currently at
26193 .display
26194 &url(http://www.modssl.org/docs/2.7/ssl_faq.html#ToC24)
26195 .endd
26196 Other parts of the &'modssl'& documentation are also helpful, and have
26197 links to further files.
26198 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
26199 0-201-61598-3), contains both introductory and more in-depth descriptions.
26200 Some sample programs taken from the book are available from
26201 .display
26202 &url(http://www.rtfm.com/openssl-examples/)
26203 .endd
26204
26205
26206 .section "Certificate chains" "SECID186"
26207 The file named by &%tls_certificate%& may contain more than one
26208 certificate. This is useful in the case where the certificate that is being
26209 sent is validated by an intermediate certificate which the other end does
26210 not have. Multiple certificates must be in the correct order in the file.
26211 First the host's certificate itself, then the first intermediate
26212 certificate to validate the issuer of the host certificate, then the next
26213 intermediate certificate to validate the issuer of the first intermediate
26214 certificate, and so on, until finally (optionally) the root certificate.
26215 The root certificate must already be trusted by the recipient for
26216 validation to succeed, of course, but if it's not preinstalled, sending the
26217 root certificate along with the rest makes it available for the user to
26218 install if the receiving end is a client MUA that can interact with a user.
26219
26220 Note that certificates using MD5 are unlikely to work on today's Internet;
26221 even if your libraries allow loading them for use in Exim when acting as a
26222 server, increasingly clients will not accept such certificates. The error
26223 diagnostics in such a case can be frustratingly vague.
26224
26225
26226
26227 .section "Self-signed certificates" "SECID187"
26228 .cindex "certificate" "self-signed"
26229 You can create a self-signed certificate using the &'req'& command provided
26230 with OpenSSL, like this:
26231 . ==== Do not shorten the duration here without reading and considering
26232 . ==== the text below. Please leave it at 9999 days.
26233 .code
26234 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
26235 -days 9999 -nodes
26236 .endd
26237 &_file1_& and &_file2_& can be the same file; the key and the certificate are
26238 delimited and so can be identified independently. The &%-days%& option
26239 specifies a period for which the certificate is valid. The &%-nodes%& option is
26240 important: if you do not set it, the key is encrypted with a passphrase
26241 that you are prompted for, and any use that is made of the key causes more
26242 prompting for the passphrase. This is not helpful if you are going to use
26243 this certificate and key in an MTA, where prompting is not possible.
26244
26245 . ==== I expect to still be working 26 years from now. The less technical
26246 . ==== debt I create, in terms of storing up trouble for my later years, the
26247 . ==== happier I will be then. We really have reached the point where we
26248 . ==== should start, at the very least, provoking thought and making folks
26249 . ==== pause before proceeding, instead of leaving all the fixes until two
26250 . ==== years before 2^31 seconds after the 1970 Unix epoch.
26251 . ==== -pdp, 2012
26252 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
26253 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
26254 the above command might produce a date in the past. Think carefully about
26255 the lifetime of the systems you're deploying, and either reduce the duration
26256 of the certificate or reconsider your platform deployment. (At time of
26257 writing, reducing the duration is the most likely choice, but the inexorable
26258 progression of time takes us steadily towards an era where this will not
26259 be a sensible resolution).
26260
26261 A self-signed certificate made in this way is sufficient for testing, and
26262 may be adequate for all your requirements if you are mainly interested in
26263 encrypting transfers, and not in secure identification.
26264
26265 However, many clients require that the certificate presented by the server be a
26266 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
26267 certificate. In this situation, the self-signed certificate described above
26268 must be installed on the client host as a trusted root &'certification
26269 authority'& (CA), and the certificate used by Exim must be a user certificate
26270 signed with that self-signed certificate.
26271
26272 For information on creating self-signed CA certificates and using them to sign
26273 user certificates, see the &'General implementation overview'& chapter of the
26274 Open-source PKI book, available online at
26275 &url(http://ospkibook.sourceforge.net/).
26276 .ecindex IIDencsmtp1
26277 .ecindex IIDencsmtp2
26278
26279
26280
26281 . ////////////////////////////////////////////////////////////////////////////
26282 . ////////////////////////////////////////////////////////////////////////////
26283
26284 .chapter "Access control lists" "CHAPACL"
26285 .scindex IIDacl "&ACL;" "description"
26286 .cindex "control of incoming mail"
26287 .cindex "message" "controlling incoming"
26288 .cindex "policy control" "access control lists"
26289 Access Control Lists (ACLs) are defined in a separate section of the run time
26290 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
26291 name, terminated by a colon. Here is a complete ACL section that contains just
26292 one very small ACL:
26293 .code
26294 begin acl
26295 small_acl:
26296 accept hosts = one.host.only
26297 .endd
26298 You can have as many lists as you like in the ACL section, and the order in
26299 which they appear does not matter. The lists are self-terminating.
26300
26301 The majority of ACLs are used to control Exim's behaviour when it receives
26302 certain SMTP commands. This applies both to incoming TCP/IP connections, and
26303 when a local process submits a message using SMTP by specifying the &%-bs%&
26304 option. The most common use is for controlling which recipients are accepted
26305 in incoming messages. In addition, you can define an ACL that is used to check
26306 local non-SMTP messages. The default configuration file contains an example of
26307 a realistic ACL for checking RCPT commands. This is discussed in chapter
26308 &<<CHAPdefconfil>>&.
26309
26310
26311 .section "Testing ACLs" "SECID188"
26312 The &%-bh%& command line option provides a way of testing your ACL
26313 configuration locally by running a fake SMTP session with which you interact.
26314 The host &'relay-test.mail-abuse.org'& provides a service for checking your
26315 relaying configuration (see section &<<SECTcheralcon>>& for more details).
26316
26317
26318
26319 .section "Specifying when ACLs are used" "SECID189"
26320 .cindex "&ACL;" "options for specifying"
26321 In order to cause an ACL to be used, you have to name it in one of the relevant
26322 options in the main part of the configuration. These options are:
26323 .cindex "AUTH" "ACL for"
26324 .cindex "DATA" "ACLs for"
26325 .cindex "ETRN" "ACL for"
26326 .cindex "EXPN" "ACL for"
26327 .cindex "HELO" "ACL for"
26328 .cindex "EHLO" "ACL for"
26329 .cindex "MAIL" "ACL for"
26330 .cindex "QUIT, ACL for"
26331 .cindex "RCPT" "ACL for"
26332 .cindex "STARTTLS, ACL for"
26333 .cindex "VRFY" "ACL for"
26334 .cindex "SMTP" "connection, ACL for"
26335 .cindex "non-SMTP messages" "ACLs for"
26336 .cindex "MIME content scanning" "ACL for"
26337
26338 .table2 140pt
26339 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
26340 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
26341 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
26342 .irow &%acl_smtp_auth%& "ACL for AUTH"
26343 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
26344 .irow &%acl_smtp_data%& "ACL after DATA is complete"
26345 .irow &%acl_smtp_etrn%& "ACL for ETRN"
26346 .irow &%acl_smtp_expn%& "ACL for EXPN"
26347 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
26348 .irow &%acl_smtp_mail%& "ACL for MAIL"
26349 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
26350 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
26351 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
26352 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
26353 .irow &%acl_smtp_quit%& "ACL for QUIT"
26354 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
26355 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
26356 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
26357 .endtable
26358
26359 For example, if you set
26360 .code
26361 acl_smtp_rcpt = small_acl
26362 .endd
26363 the little ACL defined above is used whenever Exim receives a RCPT command
26364 in an SMTP dialogue. The majority of policy tests on incoming messages can be
26365 done when RCPT commands arrive. A rejection of RCPT should cause the
26366 sending MTA to give up on the recipient address contained in the RCPT
26367 command, whereas rejection at other times may cause the client MTA to keep on
26368 trying to deliver the message. It is therefore recommended that you do as much
26369 testing as possible at RCPT time.
26370
26371
26372 .section "The non-SMTP ACLs" "SECID190"
26373 .cindex "non-SMTP messages" "ACLs for"
26374 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
26375 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
26376 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
26377 the state of the SMTP connection such as encryption and authentication) are not
26378 relevant and are forbidden in these ACLs. However, the sender and recipients
26379 are known, so the &%senders%& and &%sender_domains%& conditions and the
26380 &$sender_address$& and &$recipients$& variables can be used. Variables such as
26381 &$authenticated_sender$& are also available. You can specify added header lines
26382 in any of these ACLs.
26383
26384 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
26385 non-SMTP message, before any of the message has been read. (This is the
26386 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
26387 batched SMTP input, it runs after the DATA command has been reached. The
26388 result of this ACL is ignored; it cannot be used to reject a message. If you
26389 really need to, you could set a value in an ACL variable here and reject based
26390 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
26391 controls, and in particular, it can be used to set
26392 .code
26393 control = suppress_local_fixups
26394 .endd
26395 This cannot be used in the other non-SMTP ACLs because by the time they are
26396 run, it is too late.
26397
26398 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
26399 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
26400
26401 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
26402 kind of rejection is treated as permanent, because there is no way of sending a
26403 temporary error for these kinds of message.
26404
26405
26406 .section "The SMTP connect ACL" "SECID191"
26407 .cindex "SMTP" "connection, ACL for"
26408 .oindex &%smtp_banner%&
26409 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
26410 session, after the test specified by &%host_reject_connection%& (which is now
26411 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
26412 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
26413 the message override the banner message that is otherwise specified by the
26414 &%smtp_banner%& option.
26415
26416
26417 .section "The EHLO/HELO ACL" "SECID192"
26418 .cindex "EHLO" "ACL for"
26419 .cindex "HELO" "ACL for"
26420 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
26421 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
26422 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
26423 Note that a client may issue more than one EHLO or HELO command in an SMTP
26424 session, and indeed is required to issue a new EHLO or HELO after successfully
26425 setting up encryption following a STARTTLS command.
26426
26427 If the command is accepted by an &%accept%& verb that has a &%message%&
26428 modifier, the message may not contain more than one line (it will be truncated
26429 at the first newline and a panic logged if it does). Such a message cannot
26430 affect the EHLO options that are listed on the second and subsequent lines of
26431 an EHLO response.
26432
26433
26434 .section "The DATA ACLs" "SECID193"
26435 .cindex "DATA" "ACLs for"
26436 Two ACLs are associated with the DATA command, because it is two-stage
26437 command, with two responses being sent to the client.
26438 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
26439 is obeyed. This gives you control after all the RCPT commands, but before
26440 the message itself is received. It offers the opportunity to give a negative
26441 response to the DATA command before the data is transmitted. Header lines
26442 added by MAIL or RCPT ACLs are not visible at this time, but any that
26443 are defined here are visible when the &%acl_smtp_data%& ACL is run.
26444
26445 You cannot test the contents of the message, for example, to verify addresses
26446 in the headers, at RCPT time or when the DATA command is received. Such
26447 tests have to appear in the ACL that is run after the message itself has been
26448 received, before the final response to the DATA command is sent. This is
26449 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
26450 associated with the DATA command.
26451
26452 For both of these ACLs, it is not possible to reject individual recipients. An
26453 error response rejects the entire message. Unfortunately, it is known that some
26454 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
26455 before or after the data) correctly &-- they keep the message on their queues
26456 and try again later, but that is their problem, though it does waste some of
26457 your resources.
26458
26459 The &%acl_smtp_data%& ACL is run after both the &%acl_smtp_dkim%& and
26460 the &%acl_smtp_mime%& ACLs.
26461
26462 .section "The SMTP DKIM ACL" "SECTDKIMACL"
26463 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
26464 enabled (which is the default).
26465
26466 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
26467 received, and is executed for each DKIM signature found in a message. If not
26468 otherwise specified, the default action is to accept.
26469
26470 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
26471
26472 For details on the operation of DKIM, see chapter &<<CHAPdkim>>&.
26473
26474
26475 .section "The SMTP MIME ACL" "SECID194"
26476 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
26477 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
26478
26479 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
26480
26481
26482 .section "The QUIT ACL" "SECTQUITACL"
26483 .cindex "QUIT, ACL for"
26484 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
26485 does not affect the response code to QUIT, which is always 221. Thus, the ACL
26486 does not in fact control any access. For this reason, the only verbs that are
26487 permitted are &%accept%& and &%warn%&.
26488
26489 This ACL can be used for tasks such as custom logging at the end of an SMTP
26490 session. For example, you can use ACL variables in other ACLs to count
26491 messages, recipients, etc., and log the totals at QUIT time using one or
26492 more &%logwrite%& modifiers on a &%warn%& verb.
26493
26494 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
26495 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
26496
26497 You do not need to have a final &%accept%&, but if you do, you can use a
26498 &%message%& modifier to specify custom text that is sent as part of the 221
26499 response to QUIT.
26500
26501 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
26502 failure (for example, failure to open a log file, or when Exim is bombing out
26503 because it has detected an unrecoverable error), all SMTP commands from the
26504 client are given temporary error responses until QUIT is received or the
26505 connection is closed. In these special cases, the QUIT ACL does not run.
26506
26507
26508 .section "The not-QUIT ACL" "SECTNOTQUITACL"
26509 .vindex &$acl_smtp_notquit$&
26510 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
26511 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
26512 trouble, such as being unable to write to its log files, this ACL is not run,
26513 because it might try to do things (such as write to log files) that make the
26514 situation even worse.
26515
26516 Like the QUIT ACL, this ACL is provided to make it possible to do customized
26517 logging or to gather statistics, and its outcome is ignored. The &%delay%&
26518 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
26519 and &%warn%&.
26520
26521 .vindex &$smtp_notquit_reason$&
26522 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
26523 to a string that indicates the reason for the termination of the SMTP
26524 connection. The possible values are:
26525 .table2
26526 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
26527 .irow &`bad-commands`& "Too many unknown or non-mail commands"
26528 .irow &`command-timeout`& "Timeout while reading SMTP commands"
26529 .irow &`connection-lost`& "The SMTP connection has been lost"
26530 .irow &`data-timeout`& "Timeout while reading message data"
26531 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
26532 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
26533 .irow &`signal-exit`& "SIGTERM or SIGINT"
26534 .irow &`synchronization-error`& "SMTP synchronization error"
26535 .irow &`tls-failed`& "TLS failed to start"
26536 .endtable
26537 In most cases when an SMTP connection is closed without having received QUIT,
26538 Exim sends an SMTP response message before actually closing the connection.
26539 With the exception of the &`acl-drop`& case, the default message can be
26540 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
26541 &%drop%& verb in another ACL, it is the message from the other ACL that is
26542 used.
26543
26544
26545 .section "Finding an ACL to use" "SECID195"
26546 .cindex "&ACL;" "finding which to use"
26547 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
26548 you can use different ACLs in different circumstances. For example,
26549 .code
26550 acl_smtp_rcpt = ${if ={25}{$interface_port} \
26551 {acl_check_rcpt} {acl_check_rcpt_submit} }
26552 .endd
26553 In the default configuration file there are some example settings for
26554 providing an RFC 4409 message submission service on port 587 and a
26555 non-standard &"smtps"& service on port 465. You can use a string
26556 expansion like this to choose an ACL for MUAs on these ports which is
26557 more appropriate for this purpose than the default ACL on port 25.
26558
26559 The expanded string does not have to be the name of an ACL in the
26560 configuration file; there are other possibilities. Having expanded the
26561 string, Exim searches for an ACL as follows:
26562
26563 .ilist
26564 If the string begins with a slash, Exim uses it as a file name, and reads its
26565 contents as an ACL. The lines are processed in the same way as lines in the
26566 Exim configuration file. In particular, continuation lines are supported, blank
26567 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
26568 If the file does not exist or cannot be read, an error occurs (typically
26569 causing a temporary failure of whatever caused the ACL to be run). For example:
26570 .code
26571 acl_smtp_data = /etc/acls/\
26572 ${lookup{$sender_host_address}lsearch\
26573 {/etc/acllist}{$value}{default}}
26574 .endd
26575 This looks up an ACL file to use on the basis of the host's IP address, falling
26576 back to a default if the lookup fails. If an ACL is successfully read from a
26577 file, it is retained in memory for the duration of the Exim process, so that it
26578 can be re-used without having to re-read the file.
26579 .next
26580 If the string does not start with a slash, and does not contain any spaces,
26581 Exim searches the ACL section of the configuration for an ACL whose name
26582 matches the string.
26583 .next
26584 If no named ACL is found, or if the string contains spaces, Exim parses
26585 the string as an inline ACL. This can save typing in cases where you just
26586 want to have something like
26587 .code
26588 acl_smtp_vrfy = accept
26589 .endd
26590 in order to allow free use of the VRFY command. Such a string may contain
26591 newlines; it is processed in the same way as an ACL that is read from a file.
26592 .endlist
26593
26594
26595
26596
26597 .section "ACL return codes" "SECID196"
26598 .cindex "&ACL;" "return codes"
26599 Except for the QUIT ACL, which does not affect the SMTP return code (see
26600 section &<<SECTQUITACL>>& above), the result of running an ACL is either
26601 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
26602 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
26603 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
26604 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
26605 This also causes a 4&'xx'& return code.
26606
26607 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
26608 &"deny"&, because there is no mechanism for passing temporary errors to the
26609 submitters of non-SMTP messages.
26610
26611
26612 ACLs that are relevant to message reception may also return &"discard"&. This
26613 has the effect of &"accept"&, but causes either the entire message or an
26614 individual recipient address to be discarded. In other words, it is a
26615 blackholing facility. Use it with care.
26616
26617 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
26618 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
26619 RCPT ACL is to discard just the one recipient address. If there are no
26620 recipients left when the message's data is received, the DATA ACL is not
26621 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
26622 remaining recipients. The &"discard"& return is not permitted for the
26623 &%acl_smtp_predata%& ACL.
26624
26625
26626 .cindex "&[local_scan()]& function" "when all recipients discarded"
26627 The &[local_scan()]& function is always run, even if there are no remaining
26628 recipients; it may create new recipients.
26629
26630
26631
26632 .section "Unset ACL options" "SECID197"
26633 .cindex "&ACL;" "unset options"
26634 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
26635 all the same. &*Note*&: These defaults apply only when the relevant ACL is
26636 not defined at all. For any defined ACL, the default action when control
26637 reaches the end of the ACL statements is &"deny"&.
26638
26639 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
26640 these two are ACLs that are used only for their side effects. They cannot be
26641 used to accept or reject anything.
26642
26643 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
26644 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
26645 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
26646 when the ACL is not defined is &"accept"&.
26647
26648 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
26649 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
26650 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
26651 messages over an SMTP connection. For an example, see the ACL in the default
26652 configuration file.
26653
26654
26655
26656
26657 .section "Data for message ACLs" "SECID198"
26658 .cindex "&ACL;" "data for message ACL"
26659 .vindex &$domain$&
26660 .vindex &$local_part$&
26661 .vindex &$sender_address$&
26662 .vindex &$sender_host_address$&
26663 .vindex &$smtp_command$&
26664 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
26665 that contain information about the host and the message's sender (for example,
26666 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
26667 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
26668 &$local_part$& are set from the argument address. The entire SMTP command
26669 is available in &$smtp_command$&.
26670
26671 When an ACL for the AUTH parameter of MAIL is running, the variables that
26672 contain information about the host are set, but &$sender_address$& is not yet
26673 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
26674 how it is used.
26675
26676 .vindex "&$message_size$&"
26677 The &$message_size$& variable is set to the value of the SIZE parameter on
26678 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
26679 that parameter is not given. The value is updated to the true message size by
26680 the time the final DATA ACL is run (after the message data has been
26681 received).
26682
26683 .vindex "&$rcpt_count$&"
26684 .vindex "&$recipients_count$&"
26685 The &$rcpt_count$& variable increases by one for each RCPT command received.
26686 The &$recipients_count$& variable increases by one each time a RCPT command is
26687 accepted, so while an ACL for RCPT is being processed, it contains the number
26688 of previously accepted recipients. At DATA time (for both the DATA ACLs),
26689 &$rcpt_count$& contains the total number of RCPT commands, and
26690 &$recipients_count$& contains the total number of accepted recipients.
26691
26692
26693
26694
26695
26696 .section "Data for non-message ACLs" "SECTdatfornon"
26697 .cindex "&ACL;" "data for non-message ACL"
26698 .vindex &$smtp_command_argument$&
26699 .vindex &$smtp_command$&
26700 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
26701 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
26702 and the entire SMTP command is available in &$smtp_command$&.
26703 These variables can be tested using a &%condition%& condition. For example,
26704 here is an ACL for use with AUTH, which insists that either the session is
26705 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
26706 does not permit authentication methods that use cleartext passwords on
26707 unencrypted connections.
26708 .code
26709 acl_check_auth:
26710 accept encrypted = *
26711 accept condition = ${if eq{${uc:$smtp_command_argument}}\
26712 {CRAM-MD5}}
26713 deny message = TLS encryption or CRAM-MD5 required
26714 .endd
26715 (Another way of applying this restriction is to arrange for the authenticators
26716 that use cleartext passwords not to be advertised when the connection is not
26717 encrypted. You can use the generic &%server_advertise_condition%& authenticator
26718 option to do this.)
26719
26720
26721
26722 .section "Format of an ACL" "SECID199"
26723 .cindex "&ACL;" "format of"
26724 .cindex "&ACL;" "verbs, definition of"
26725 An individual ACL consists of a number of statements. Each statement starts
26726 with a verb, optionally followed by a number of conditions and &"modifiers"&.
26727 Modifiers can change the way the verb operates, define error and log messages,
26728 set variables, insert delays, and vary the processing of accepted messages.
26729
26730 If all the conditions are met, the verb is obeyed. The same condition may be
26731 used (with different arguments) more than once in the same statement. This
26732 provides a means of specifying an &"and"& conjunction between conditions. For
26733 example:
26734 .code
26735 deny dnslists = list1.example
26736 dnslists = list2.example
26737 .endd
26738 If there are no conditions, the verb is always obeyed. Exim stops evaluating
26739 the conditions and modifiers when it reaches a condition that fails. What
26740 happens then depends on the verb (and in one case, on a special modifier). Not
26741 all the conditions make sense at every testing point. For example, you cannot
26742 test a sender address in the ACL that is run for a VRFY command.
26743
26744
26745 .section "ACL verbs" "SECID200"
26746 The ACL verbs are as follows:
26747
26748 .ilist
26749 .cindex "&%accept%& ACL verb"
26750 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
26751 of the conditions are not met, what happens depends on whether &%endpass%&
26752 appears among the conditions (for syntax see below). If the failing condition
26753 is before &%endpass%&, control is passed to the next ACL statement; if it is
26754 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
26755 check a RCPT command:
26756 .code
26757 accept domains = +local_domains
26758 endpass
26759 verify = recipient
26760 .endd
26761 If the recipient domain does not match the &%domains%& condition, control
26762 passes to the next statement. If it does match, the recipient is verified, and
26763 the command is accepted if verification succeeds. However, if verification
26764 fails, the ACL yields &"deny"&, because the failing condition is after
26765 &%endpass%&.
26766
26767 The &%endpass%& feature has turned out to be confusing to many people, so its
26768 use is not recommended nowadays. It is always possible to rewrite an ACL so
26769 that &%endpass%& is not needed, and it is no longer used in the default
26770 configuration.
26771
26772 .cindex "&%message%& ACL modifier" "with &%accept%&"
26773 If a &%message%& modifier appears on an &%accept%& statement, its action
26774 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
26775 (when an &%accept%& verb either accepts or passes control to the next
26776 statement), &%message%& can be used to vary the message that is sent when an
26777 SMTP command is accepted. For example, in a RCPT ACL you could have:
26778 .display
26779 &`accept `&<&'some conditions'&>
26780 &` message = OK, I will allow you through today`&
26781 .endd
26782 You can specify an SMTP response code, optionally followed by an &"extended
26783 response code"& at the start of the message, but the first digit must be the
26784 same as would be sent by default, which is 2 for an &%accept%& verb.
26785
26786 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
26787 an error message that is used when access is denied. This behaviour is retained
26788 for backward compatibility, but current &"best practice"& is to avoid the use
26789 of &%endpass%&.
26790
26791
26792 .next
26793 .cindex "&%defer%& ACL verb"
26794 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
26795 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
26796 &%defer%& is the same as &%deny%&, because there is no way of sending a
26797 temporary error. For a RCPT command, &%defer%& is much the same as using a
26798 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
26799 be used in any ACL, and even for a recipient it might be a simpler approach.
26800
26801
26802 .next
26803 .cindex "&%deny%& ACL verb"
26804 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
26805 the conditions are not met, control is passed to the next ACL statement. For
26806 example,
26807 .code
26808 deny dnslists = blackholes.mail-abuse.org
26809 .endd
26810 rejects commands from hosts that are on a DNS black list.
26811
26812
26813 .next
26814 .cindex "&%discard%& ACL verb"
26815 &%discard%&: This verb behaves like &%accept%&, except that it returns
26816 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
26817 that are concerned with receiving messages. When all the conditions are true,
26818 the sending entity receives a &"success"& response. However, &%discard%& causes
26819 recipients to be discarded. If it is used in an ACL for RCPT, just the one
26820 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
26821 message's recipients are discarded. Recipients that are discarded before DATA
26822 do not appear in the log line when the &%received_recipients%& log selector is set.
26823
26824 If the &%log_message%& modifier is set when &%discard%& operates,
26825 its contents are added to the line that is automatically written to the log.
26826 The &%message%& modifier operates exactly as it does for &%accept%&.
26827
26828
26829 .next
26830 .cindex "&%drop%& ACL verb"
26831 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
26832 forcibly closed after the 5&'xx'& error message has been sent. For example:
26833 .code
26834 drop message = I don't take more than 20 RCPTs
26835 condition = ${if > {$rcpt_count}{20}}
26836 .endd
26837 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
26838 The connection is always dropped after sending a 550 response.
26839
26840 .next
26841 .cindex "&%require%& ACL verb"
26842 &%require%&: If all the conditions are met, control is passed to the next ACL
26843 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
26844 example, when checking a RCPT command,
26845 .code
26846 require message = Sender did not verify
26847 verify = sender
26848 .endd
26849 passes control to subsequent statements only if the message's sender can be
26850 verified. Otherwise, it rejects the command. Note the positioning of the
26851 &%message%& modifier, before the &%verify%& condition. The reason for this is
26852 discussed in section &<<SECTcondmodproc>>&.
26853
26854 .next
26855 .cindex "&%warn%& ACL verb"
26856 &%warn%&: If all the conditions are true, a line specified by the
26857 &%log_message%& modifier is written to Exim's main log. Control always passes
26858 to the next ACL statement. If any condition is false, the log line is not
26859 written. If an identical log line is requested several times in the same
26860 message, only one copy is actually written to the log. If you want to force
26861 duplicates to be written, use the &%logwrite%& modifier instead.
26862
26863 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
26864 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
26865 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
26866 first failing condition. There is more about adding header lines in section
26867 &<<SECTaddheadacl>>&.
26868
26869 If any condition on a &%warn%& statement cannot be completed (that is, there is
26870 some sort of defer), the log line specified by &%log_message%& is not written.
26871 This does not include the case of a forced failure from a lookup, which
26872 is considered to be a successful completion. After a defer, no further
26873 conditions or modifiers in the &%warn%& statement are processed. The incident
26874 is logged, and the ACL continues to be processed, from the next statement
26875 onwards.
26876
26877
26878 .vindex "&$acl_verify_message$&"
26879 When one of the &%warn%& conditions is an address verification that fails, the
26880 text of the verification failure message is in &$acl_verify_message$&. If you
26881 want this logged, you must set it up explicitly. For example:
26882 .code
26883 warn !verify = sender
26884 log_message = sender verify failed: $acl_verify_message
26885 .endd
26886 .endlist
26887
26888 At the end of each ACL there is an implicit unconditional &%deny%&.
26889
26890 As you can see from the examples above, the conditions and modifiers are
26891 written one to a line, with the first one on the same line as the verb, and
26892 subsequent ones on following lines. If you have a very long condition, you can
26893 continue it onto several physical lines by the usual backslash continuation
26894 mechanism. It is conventional to align the conditions vertically.
26895
26896
26897
26898 .section "ACL variables" "SECTaclvariables"
26899 .cindex "&ACL;" "variables"
26900 There are some special variables that can be set during ACL processing. They
26901 can be used to pass information between different ACLs, different invocations
26902 of the same ACL in the same SMTP connection, and between ACLs and the routers,
26903 transports, and filters that are used to deliver a message. The names of these
26904 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
26905 an underscore, but the remainder of the name can be any sequence of
26906 alphanumeric characters and underscores that you choose. There is no limit on
26907 the number of ACL variables. The two sets act as follows:
26908 .ilist
26909 The values of those variables whose names begin with &$acl_c$& persist
26910 throughout an SMTP connection. They are never reset. Thus, a value that is set
26911 while receiving one message is still available when receiving the next message
26912 on the same SMTP connection.
26913 .next
26914 The values of those variables whose names begin with &$acl_m$& persist only
26915 while a message is being received. They are reset afterwards. They are also
26916 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
26917 .endlist
26918
26919 When a message is accepted, the current values of all the ACL variables are
26920 preserved with the message and are subsequently made available at delivery
26921 time. The ACL variables are set by a modifier called &%set%&. For example:
26922 .code
26923 accept hosts = whatever
26924 set acl_m4 = some value
26925 accept authenticated = *
26926 set acl_c_auth = yes
26927 .endd
26928 &*Note*&: A leading dollar sign is not used when naming a variable that is to
26929 be set. If you want to set a variable without taking any action, you can use a
26930 &%warn%& verb without any other modifiers or conditions.
26931
26932 .oindex &%strict_acl_vars%&
26933 What happens if a syntactically valid but undefined ACL variable is
26934 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
26935 false (the default), an empty string is substituted; if it is true, an
26936 error is generated.
26937
26938 Versions of Exim before 4.64 have a limited set of numbered variables, but
26939 their names are compatible, so there is no problem with upgrading.
26940
26941
26942 .section "Condition and modifier processing" "SECTcondmodproc"
26943 .cindex "&ACL;" "conditions; processing"
26944 .cindex "&ACL;" "modifiers; processing"
26945 An exclamation mark preceding a condition negates its result. For example:
26946 .code
26947 deny domains = *.dom.example
26948 !verify = recipient
26949 .endd
26950 causes the ACL to return &"deny"& if the recipient domain ends in
26951 &'dom.example'& and the recipient address cannot be verified. Sometimes
26952 negation can be used on the right-hand side of a condition. For example, these
26953 two statements are equivalent:
26954 .code
26955 deny hosts = !192.168.3.4
26956 deny !hosts = 192.168.3.4
26957 .endd
26958 However, for many conditions (&%verify%& being a good example), only left-hand
26959 side negation of the whole condition is possible.
26960
26961 The arguments of conditions and modifiers are expanded. A forced failure
26962 of an expansion causes a condition to be ignored, that is, it behaves as if the
26963 condition is true. Consider these two statements:
26964 .code
26965 accept senders = ${lookup{$host_name}lsearch\
26966 {/some/file}{$value}fail}
26967 accept senders = ${lookup{$host_name}lsearch\
26968 {/some/file}{$value}{}}
26969 .endd
26970 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
26971 the returned list is searched, but if the lookup fails the behaviour is
26972 different in the two cases. The &%fail%& in the first statement causes the
26973 condition to be ignored, leaving no further conditions. The &%accept%& verb
26974 therefore succeeds. The second statement, however, generates an empty list when
26975 the lookup fails. No sender can match an empty list, so the condition fails,
26976 and therefore the &%accept%& also fails.
26977
26978 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
26979 specify actions that are taken as the conditions for a statement are checked;
26980 others specify text for messages that are used when access is denied or a
26981 warning is generated. The &%control%& modifier affects the way an incoming
26982 message is handled.
26983
26984 The positioning of the modifiers in an ACL statement is important, because the
26985 processing of a verb ceases as soon as its outcome is known. Only those
26986 modifiers that have already been encountered will take effect. For example,
26987 consider this use of the &%message%& modifier:
26988 .code
26989 require message = Can't verify sender
26990 verify = sender
26991 message = Can't verify recipient
26992 verify = recipient
26993 message = This message cannot be used
26994 .endd
26995 If sender verification fails, Exim knows that the result of the statement is
26996 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
26997 so its text is used as the error message. If sender verification succeeds, but
26998 recipient verification fails, the second message is used. If recipient
26999 verification succeeds, the third message becomes &"current"&, but is never used
27000 because there are no more conditions to cause failure.
27001
27002 For the &%deny%& verb, on the other hand, it is always the last &%message%&
27003 modifier that is used, because all the conditions must be true for rejection to
27004 happen. Specifying more than one &%message%& modifier does not make sense, and
27005 the message can even be specified after all the conditions. For example:
27006 .code
27007 deny hosts = ...
27008 !senders = *@my.domain.example
27009 message = Invalid sender from client host
27010 .endd
27011 The &"deny"& result does not happen until the end of the statement is reached,
27012 by which time Exim has set up the message.
27013
27014
27015
27016 .section "ACL modifiers" "SECTACLmodi"
27017 .cindex "&ACL;" "modifiers; list of"
27018 The ACL modifiers are as follows:
27019
27020 .vlist
27021 .vitem &*add_header*&&~=&~<&'text'&>
27022 This modifier specifies one or more header lines that are to be added to an
27023 incoming message, assuming, of course, that the message is ultimately
27024 accepted. For details, see section &<<SECTaddheadacl>>&.
27025
27026 .vitem &*continue*&&~=&~<&'text'&>
27027 .cindex "&%continue%& ACL modifier"
27028 .cindex "database" "updating in ACL"
27029 This modifier does nothing of itself, and processing of the ACL always
27030 continues with the next condition or modifier. The value of &%continue%& is in
27031 the side effects of expanding its argument. Typically this could be used to
27032 update a database. It is really just a syntactic tidiness, to avoid having to
27033 write rather ugly lines like this:
27034 .display
27035 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
27036 .endd
27037 Instead, all you need is
27038 .display
27039 &`continue = `&<&'some expansion'&>
27040 .endd
27041
27042 .vitem &*control*&&~=&~<&'text'&>
27043 .cindex "&%control%& ACL modifier"
27044 This modifier affects the subsequent processing of the SMTP connection or of an
27045 incoming message that is accepted. The effect of the first type of control
27046 lasts for the duration of the connection, whereas the effect of the second type
27047 lasts only until the current message has been received. The message-specific
27048 controls always apply to the whole message, not to individual recipients,
27049 even if the &%control%& modifier appears in a RCPT ACL.
27050
27051 As there are now quite a few controls that can be applied, they are described
27052 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
27053 in several different ways. For example:
27054
27055 . ==== As this is a nested list, any displays it contains must be indented
27056 . ==== as otherwise they are too far to the left. That comment applies only
27057 . ==== when xmlto and fop are used; formatting with sdop gets it right either
27058 . ==== way.
27059
27060 .ilist
27061 It can be at the end of an &%accept%& statement:
27062 .code
27063 accept ...some conditions
27064 control = queue_only
27065 .endd
27066 In this case, the control is applied when this statement yields &"accept"&, in
27067 other words, when the conditions are all true.
27068
27069 .next
27070 It can be in the middle of an &%accept%& statement:
27071 .code
27072 accept ...some conditions...
27073 control = queue_only
27074 ...some more conditions...
27075 .endd
27076 If the first set of conditions are true, the control is applied, even if the
27077 statement does not accept because one of the second set of conditions is false.
27078 In this case, some subsequent statement must yield &"accept"& for the control
27079 to be relevant.
27080
27081 .next
27082 It can be used with &%warn%& to apply the control, leaving the
27083 decision about accepting or denying to a subsequent verb. For
27084 example:
27085 .code
27086 warn ...some conditions...
27087 control = freeze
27088 accept ...
27089 .endd
27090 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
27091 &%logwrite%&, so it does not add anything to the message and does not write a
27092 log entry.
27093
27094 .next
27095 If you want to apply a control unconditionally, you can use it with a
27096 &%require%& verb. For example:
27097 .code
27098 require control = no_multiline_responses
27099 .endd
27100 .endlist
27101
27102 .vitem &*delay*&&~=&~<&'time'&>
27103 .cindex "&%delay%& ACL modifier"
27104 .oindex "&%-bh%&"
27105 This modifier may appear in any ACL except notquit. It causes Exim to wait for
27106 the time interval before proceeding. However, when testing Exim using the
27107 &%-bh%& option, the delay is not actually imposed (an appropriate message is
27108 output instead). The time is given in the usual Exim notation, and the delay
27109 happens as soon as the modifier is processed. In an SMTP session, pending
27110 output is flushed before the delay is imposed.
27111
27112 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
27113 example:
27114 .code
27115 deny ...some conditions...
27116 delay = 30s
27117 .endd
27118 The delay happens if all the conditions are true, before the statement returns
27119 &"deny"&. Compare this with:
27120 .code
27121 deny delay = 30s
27122 ...some conditions...
27123 .endd
27124 which waits for 30s before processing the conditions. The &%delay%& modifier
27125 can also be used with &%warn%& and together with &%control%&:
27126 .code
27127 warn ...some conditions...
27128 delay = 2m
27129 control = freeze
27130 accept ...
27131 .endd
27132
27133 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
27134 responses to several commands are no longer buffered and sent in one packet (as
27135 they would normally be) because all output is flushed before imposing the
27136 delay. This optimization is disabled so that a number of small delays do not
27137 appear to the client as one large aggregated delay that might provoke an
27138 unwanted timeout. You can, however, disable output flushing for &%delay%& by
27139 using a &%control%& modifier to set &%no_delay_flush%&.
27140
27141
27142 .vitem &*endpass*&
27143 .cindex "&%endpass%& ACL modifier"
27144 This modifier, which has no argument, is recognized only in &%accept%& and
27145 &%discard%& statements. It marks the boundary between the conditions whose
27146 failure causes control to pass to the next statement, and the conditions whose
27147 failure causes the ACL to return &"deny"&. This concept has proved to be
27148 confusing to some people, so the use of &%endpass%& is no longer recommended as
27149 &"best practice"&. See the description of &%accept%& above for more details.
27150
27151
27152 .vitem &*log_message*&&~=&~<&'text'&>
27153 .cindex "&%log_message%& ACL modifier"
27154 This modifier sets up a message that is used as part of the log message if the
27155 ACL denies access or a &%warn%& statement's conditions are true. For example:
27156 .code
27157 require log_message = wrong cipher suite $tls_in_cipher
27158 encrypted = DES-CBC3-SHA
27159 .endd
27160 &%log_message%& is also used when recipients are discarded by &%discard%&. For
27161 example:
27162 .display
27163 &`discard `&<&'some conditions'&>
27164 &` log_message = Discarded $local_part@$domain because...`&
27165 .endd
27166 When access is denied, &%log_message%& adds to any underlying error message
27167 that may exist because of a condition failure. For example, while verifying a
27168 recipient address, a &':fail:'& redirection might have already set up a
27169 message.
27170
27171 The message may be defined before the conditions to which it applies, because
27172 the string expansion does not happen until Exim decides that access is to be
27173 denied. This means that any variables that are set by the condition are
27174 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
27175 variables are set after a DNS black list lookup succeeds. If the expansion of
27176 &%log_message%& fails, or if the result is an empty string, the modifier is
27177 ignored.
27178
27179 .vindex "&$acl_verify_message$&"
27180 If you want to use a &%warn%& statement to log the result of an address
27181 verification, you can use &$acl_verify_message$& to include the verification
27182 error message.
27183
27184 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
27185 the start of the logged message. If the same warning log message is requested
27186 more than once while receiving a single email message, only one copy is
27187 actually logged. If you want to log multiple copies, use &%logwrite%& instead
27188 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
27189 is logged for a successful &%warn%& statement.
27190
27191 If &%log_message%& is not present and there is no underlying error message (for
27192 example, from the failure of address verification), but &%message%& is present,
27193 the &%message%& text is used for logging rejections. However, if any text for
27194 logging contains newlines, only the first line is logged. In the absence of
27195 both &%log_message%& and &%message%&, a default built-in message is used for
27196 logging rejections.
27197
27198
27199 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
27200 .cindex "&%log_reject_target%& ACL modifier"
27201 .cindex "logging in ACL" "specifying which log"
27202 This modifier makes it possible to specify which logs are used for messages
27203 about ACL rejections. Its argument is a colon-separated list of words that can
27204 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
27205 may be empty, in which case a rejection is not logged at all. For example, this
27206 ACL fragment writes no logging information when access is denied:
27207 .display
27208 &`deny `&<&'some conditions'&>
27209 &` log_reject_target =`&
27210 .endd
27211 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
27212 permanent and temporary rejections. Its effect lasts for the rest of the
27213 current ACL.
27214
27215
27216 .vitem &*logwrite*&&~=&~<&'text'&>
27217 .cindex "&%logwrite%& ACL modifier"
27218 .cindex "logging in ACL" "immediate"
27219 This modifier writes a message to a log file as soon as it is encountered when
27220 processing an ACL. (Compare &%log_message%&, which, except in the case of
27221 &%warn%& and &%discard%&, is used only if the ACL statement denies
27222 access.) The &%logwrite%& modifier can be used to log special incidents in
27223 ACLs. For example:
27224 .display
27225 &`accept `&<&'some special conditions'&>
27226 &` control = freeze`&
27227 &` logwrite = froze message because ...`&
27228 .endd
27229 By default, the message is written to the main log. However, it may begin
27230 with a colon, followed by a comma-separated list of log names, and then
27231 another colon, to specify exactly which logs are to be written. For
27232 example:
27233 .code
27234 logwrite = :main,reject: text for main and reject logs
27235 logwrite = :panic: text for panic log only
27236 .endd
27237
27238
27239 .vitem &*message*&&~=&~<&'text'&>
27240 .cindex "&%message%& ACL modifier"
27241 This modifier sets up a text string that is expanded and used as a response
27242 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
27243 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
27244 there is some complication if &%endpass%& is involved; see the description of
27245 &%accept%& for details.)
27246
27247 The expansion of the message happens at the time Exim decides that the ACL is
27248 to end, not at the time it processes &%message%&. If the expansion fails, or
27249 generates an empty string, the modifier is ignored. Here is an example where
27250 &%message%& must be specified first, because the ACL ends with a rejection if
27251 the &%hosts%& condition fails:
27252 .code
27253 require message = Host not recognized
27254 hosts = 10.0.0.0/8
27255 .endd
27256 (Once a condition has failed, no further conditions or modifiers are
27257 processed.)
27258
27259 .cindex "SMTP" "error codes"
27260 .oindex "&%smtp_banner%&
27261 For ACLs that are triggered by SMTP commands, the message is returned as part
27262 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
27263 is meaningful only for SMTP, as no message is returned when a non-SMTP message
27264 is accepted. In the case of the connect ACL, accepting with a message modifier
27265 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
27266 accept message may not contain more than one line (otherwise it will be
27267 truncated at the first newline and a panic logged), and it cannot affect the
27268 EHLO options.
27269
27270 When SMTP is involved, the message may begin with an overriding response code,
27271 consisting of three digits optionally followed by an &"extended response code"&
27272 of the form &'n.n.n'&, each code being followed by a space. For example:
27273 .code
27274 deny message = 599 1.2.3 Host not welcome
27275 hosts = 192.168.34.0/24
27276 .endd
27277 The first digit of the supplied response code must be the same as would be sent
27278 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
27279 access, but for the predata ACL, note that the default success code is 354, not
27280 2&'xx'&.
27281
27282 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
27283 the message modifier cannot override the 221 response code.
27284
27285 The text in a &%message%& modifier is literal; any quotes are taken as
27286 literals, but because the string is expanded, backslash escapes are processed
27287 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
27288 response.
27289
27290 .vindex "&$acl_verify_message$&"
27291 If &%message%& is used on a statement that verifies an address, the message
27292 specified overrides any message that is generated by the verification process.
27293 However, the original message is available in the variable
27294 &$acl_verify_message$&, so you can incorporate it into your message if you
27295 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
27296 routers to be passed back as part of the SMTP response, you should either not
27297 use a &%message%& modifier, or make use of &$acl_verify_message$&.
27298
27299 For compatibility with previous releases of Exim, a &%message%& modifier that
27300 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
27301 modifier, but this usage is now deprecated. However, &%message%& acts only when
27302 all the conditions are true, wherever it appears in an ACL command, whereas
27303 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
27304 &%warn%& in an ACL that is not concerned with receiving a message, it has no
27305 effect.
27306
27307
27308 .vitem &*remove_header*&&~=&~<&'text'&>
27309 This modifier specifies one or more header names in a colon-separated list
27310 that are to be removed from an incoming message, assuming, of course, that
27311 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
27312
27313
27314 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
27315 .cindex "&%set%& ACL modifier"
27316 This modifier puts a value into one of the ACL variables (see section
27317 &<<SECTaclvariables>>&).
27318
27319
27320 .vitem &*udpsend*&&~=&~<&'parameters'&>
27321 This modifier sends a UDP packet, for purposes such as statistics
27322 collection or behaviour monitoring. The parameters are expanded, and
27323 the result of the expansion must be a colon-separated list consisting
27324 of a destination server, port number, and the packet contents. The
27325 server can be specified as a host name or IPv4 or IPv6 address. The
27326 separator can be changed with the usual angle bracket syntax. For
27327 example, you might want to collect information on which hosts connect
27328 when:
27329 .code
27330 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
27331 $tod_zulu $sender_host_address
27332 .endd
27333 .endlist
27334
27335
27336
27337
27338 .section "Use of the control modifier" "SECTcontrols"
27339 .cindex "&%control%& ACL modifier"
27340 The &%control%& modifier supports the following settings:
27341
27342 .vlist
27343 .vitem &*control&~=&~allow_auth_unadvertised*&
27344 This modifier allows a client host to use the SMTP AUTH command even when it
27345 has not been advertised in response to EHLO. Furthermore, because there are
27346 apparently some really broken clients that do this, Exim will accept AUTH after
27347 HELO (rather than EHLO) when this control is set. It should be used only if you
27348 really need it, and you should limit its use to those broken clients that do
27349 not work without it. For example:
27350 .code
27351 warn hosts = 192.168.34.25
27352 control = allow_auth_unadvertised
27353 .endd
27354 Normally, when an Exim server receives an AUTH command, it checks the name of
27355 the authentication mechanism that is given in the command to ensure that it
27356 matches an advertised mechanism. When this control is set, the check that a
27357 mechanism has been advertised is bypassed. Any configured mechanism can be used
27358 by the client. This control is permitted only in the connection and HELO ACLs.
27359
27360
27361 .vitem &*control&~=&~caseful_local_part*& &&&
27362 &*control&~=&~caselower_local_part*&
27363 .cindex "&ACL;" "case of local part in"
27364 .cindex "case of local parts"
27365 .vindex "&$local_part$&"
27366 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
27367 (that is, during RCPT processing). By default, the contents of &$local_part$&
27368 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
27369 any uppercase letters in the original local part are restored in &$local_part$&
27370 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
27371 is encountered.
27372
27373 These controls affect only the current recipient. Moreover, they apply only to
27374 local part handling that takes place directly in the ACL (for example, as a key
27375 in lookups). If a test to verify the recipient is obeyed, the case-related
27376 handling of the local part during the verification is controlled by the router
27377 configuration (see the &%caseful_local_part%& generic router option).
27378
27379 This facility could be used, for example, to add a spam score to local parts
27380 containing upper case letters. For example, using &$acl_m4$& to accumulate the
27381 spam score:
27382 .code
27383 warn control = caseful_local_part
27384 set acl_m4 = ${eval:\
27385 $acl_m4 + \
27386 ${if match{$local_part}{[A-Z]}{1}{0}}\
27387 }
27388 control = caselower_local_part
27389 .endd
27390 Notice that we put back the lower cased version afterwards, assuming that
27391 is what is wanted for subsequent tests.
27392
27393
27394 .vitem &*control&~=&~cutthrough_delivery*&
27395 .cindex "&ACL;" "cutthrough routing"
27396 .cindex "cutthrough" "requesting"
27397 This option requests delivery be attempted while the item is being received.
27398 It is usable in the RCPT ACL and valid only for single-recipient mails forwarded
27399 from one SMTP connection to another. If a recipient-verify callout connection is
27400 requested in the same ACL it is held open and used for the data, otherwise one is made
27401 after the ACL completes.
27402
27403 Note that routers are used in verify mode,
27404 and cannot depend on content of received headers.
27405 Note also that headers cannot be
27406 modified by any of the post-data ACLs (DATA, MIME and DKIM).
27407 Headers may be modified by routers (subject to the above) and transports.
27408
27409 Cutthrough delivery is not supported via transport-filters or when DKIM signing
27410 of outgoing messages is done, because it sends data to the ultimate destination
27411 before the entire message has been received from the source.
27412
27413 Should the ultimate destination system positively accept or reject the mail,
27414 a corresponding indication is given to the source system and nothing is queued.
27415 If there is a temporary error the item is queued for later delivery in the
27416 usual fashion. If the item is successfully delivered in cutthrough mode the log line
27417 is tagged with ">>" rather than "=>" and appears before the acceptance "<="
27418 line.
27419
27420 Delivery in this mode avoids the generation of a bounce mail to a (possibly faked)
27421 sender when the destination system is doing content-scan based rejection.
27422
27423
27424 .vitem &*control&~=&~debug/*&<&'options'&>
27425 .cindex "&ACL;" "enabling debug logging"
27426 .cindex "debugging" "enabling from an ACL"
27427 This control turns on debug logging, almost as though Exim had been invoked
27428 with &`-d`&, with the output going to a new logfile, by default called
27429 &'debuglog'&. The filename can be adjusted with the &'tag'& option, which
27430 may access any variables already defined. The logging may be adjusted with
27431 the &'opts'& option, which takes the same values as the &`-d`& command-line
27432 option. Some examples (which depend on variables that don't exist in all
27433 contexts):
27434 .code
27435 control = debug
27436 control = debug/tag=.$sender_host_address
27437 control = debug/opts=+expand+acl
27438 control = debug/tag=.$message_exim_id/opts=+expand
27439 .endd
27440
27441
27442 .vitem &*control&~=&~dkim_disable_verify*&
27443 .cindex "disable DKIM verify"
27444 .cindex "DKIM" "disable verify"
27445 This control turns off DKIM verification processing entirely. For details on
27446 the operation and configuration of DKIM, see chapter &<<CHAPdkim>>&.
27447
27448
27449 .vitem &*control&~=&~dscp/*&<&'value'&>
27450 .cindex "&ACL;" "setting DSCP value"
27451 .cindex "DSCP" "inbound"
27452 This option causes the DSCP value associated with the socket for the inbound
27453 connection to be adjusted to a given value, given as one of a number of fixed
27454 strings or to numeric value.
27455 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
27456 Common values include &`throughput`&, &`mincost`&, and on newer systems
27457 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
27458
27459 The outbound packets from Exim will be marked with this value in the header
27460 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
27461 that these values will have any effect, not be stripped by networking
27462 equipment, or do much of anything without cooperation with your Network
27463 Engineer and those of all network operators between the source and destination.
27464
27465
27466 .vitem &*control&~=&~enforce_sync*& &&&
27467 &*control&~=&~no_enforce_sync*&
27468 .cindex "SMTP" "synchronization checking"
27469 .cindex "synchronization checking in SMTP"
27470 These controls make it possible to be selective about when SMTP synchronization
27471 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
27472 state of the switch (it is true by default). See the description of this option
27473 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
27474
27475 The effect of these two controls lasts for the remainder of the SMTP
27476 connection. They can appear in any ACL except the one for the non-SMTP
27477 messages. The most straightforward place to put them is in the ACL defined by
27478 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
27479 before the first synchronization check. The expected use is to turn off the
27480 synchronization checks for badly-behaved hosts that you nevertheless need to
27481 work with.
27482
27483
27484 .vitem &*control&~=&~fakedefer/*&<&'message'&>
27485 .cindex "fake defer"
27486 .cindex "defer, fake"
27487 This control works in exactly the same way as &%fakereject%& (described below)
27488 except that it causes an SMTP 450 response after the message data instead of a
27489 550 response. You must take care when using &%fakedefer%& because it causes the
27490 messages to be duplicated when the sender retries. Therefore, you should not
27491 use &%fakedefer%& if the message is to be delivered normally.
27492
27493 .vitem &*control&~=&~fakereject/*&<&'message'&>
27494 .cindex "fake rejection"
27495 .cindex "rejection, fake"
27496 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
27497 words, only when an SMTP message is being received. If Exim accepts the
27498 message, instead the final 250 response, a 550 rejection message is sent.
27499 However, Exim proceeds to deliver the message as normal. The control applies
27500 only to the current message, not to any subsequent ones that may be received in
27501 the same SMTP connection.
27502
27503 The text for the 550 response is taken from the &%control%& modifier. If no
27504 message is supplied, the following is used:
27505 .code
27506 550-Your message has been rejected but is being
27507 550-kept for evaluation.
27508 550-If it was a legitimate message, it may still be
27509 550 delivered to the target recipient(s).
27510 .endd
27511 This facility should be used with extreme caution.
27512
27513 .vitem &*control&~=&~freeze*&
27514 .cindex "frozen messages" "forcing in ACL"
27515 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
27516 other words, only when a message is being received. If the message is accepted,
27517 it is placed on Exim's queue and frozen. The control applies only to the
27518 current message, not to any subsequent ones that may be received in the same
27519 SMTP connection.
27520
27521 This modifier can optionally be followed by &`/no_tell`&. If the global option
27522 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
27523 is told about the freezing), provided all the &*control=freeze*& modifiers that
27524 are obeyed for the current message have the &`/no_tell`& option.
27525
27526 .vitem &*control&~=&~no_delay_flush*&
27527 .cindex "SMTP" "output flushing, disabling for delay"
27528 Exim normally flushes SMTP output before implementing a delay in an ACL, to
27529 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
27530 use. This control, as long as it is encountered before the &%delay%& modifier,
27531 disables such output flushing.
27532
27533 .vitem &*control&~=&~no_callout_flush*&
27534 .cindex "SMTP" "output flushing, disabling for callout"
27535 Exim normally flushes SMTP output before performing a callout in an ACL, to
27536 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
27537 use. This control, as long as it is encountered before the &%verify%& condition
27538 that causes the callout, disables such output flushing.
27539
27540 .vitem &*control&~=&~no_mbox_unspool*&
27541 This control is available when Exim is compiled with the content scanning
27542 extension. Content scanning may require a copy of the current message, or parts
27543 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
27544 or spam scanner. Normally, such copies are deleted when they are no longer
27545 needed. If this control is set, the copies are not deleted. The control applies
27546 only to the current message, not to any subsequent ones that may be received in
27547 the same SMTP connection. It is provided for debugging purposes and is unlikely
27548 to be useful in production.
27549
27550 .vitem &*control&~=&~no_multiline_responses*&
27551 .cindex "multiline responses, suppressing"
27552 This control is permitted for any ACL except the one for non-SMTP messages.
27553 It seems that there are broken clients in use that cannot handle multiline
27554 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
27555
27556 If this control is set, multiline SMTP responses from ACL rejections are
27557 suppressed. One way of doing this would have been to put out these responses as
27558 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
27559 (&"use multiline responses for more"& it says &-- ha!), and some of the
27560 responses might get close to that. So this facility, which is after all only a
27561 sop to broken clients, is implemented by doing two very easy things:
27562
27563 .ilist
27564 Extra information that is normally output as part of a rejection caused by
27565 sender verification failure is omitted. Only the final line (typically &"sender
27566 verification failed"&) is sent.
27567 .next
27568 If a &%message%& modifier supplies a multiline response, only the first
27569 line is output.
27570 .endlist
27571
27572 The setting of the switch can, of course, be made conditional on the
27573 calling host. Its effect lasts until the end of the SMTP connection.
27574
27575 .vitem &*control&~=&~no_pipelining*&
27576 .cindex "PIPELINING" "suppressing advertising"
27577 This control turns off the advertising of the PIPELINING extension to SMTP in
27578 the current session. To be useful, it must be obeyed before Exim sends its
27579 response to an EHLO command. Therefore, it should normally appear in an ACL
27580 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
27581 &%pipelining_advertise_hosts%&.
27582
27583 .vitem &*control&~=&~queue_only*&
27584 .oindex "&%queue_only%&"
27585 .cindex "queueing incoming messages"
27586 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
27587 other words, only when a message is being received. If the message is accepted,
27588 it is placed on Exim's queue and left there for delivery by a subsequent queue
27589 runner. No immediate delivery process is started. In other words, it has the
27590 effect as the &%queue_only%& global option. However, the control applies only
27591 to the current message, not to any subsequent ones that may be received in the
27592 same SMTP connection.
27593
27594 .vitem &*control&~=&~submission/*&<&'options'&>
27595 .cindex "message" "submission"
27596 .cindex "submission mode"
27597 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
27598 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
27599 the current message is a submission from a local MUA. In this case, Exim
27600 operates in &"submission mode"&, and applies certain fixups to the message if
27601 necessary. For example, it adds a &'Date:'& header line if one is not present.
27602 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
27603 late (the message has already been created).
27604
27605 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
27606 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
27607 submission mode; the available options for this control are described there.
27608 The control applies only to the current message, not to any subsequent ones
27609 that may be received in the same SMTP connection.
27610
27611 .vitem &*control&~=&~suppress_local_fixups*&
27612 .cindex "submission fixups, suppressing"
27613 This control applies to locally submitted (non TCP/IP) messages, and is the
27614 complement of &`control = submission`&. It disables the fixups that are
27615 normally applied to locally-submitted messages. Specifically:
27616
27617 .ilist
27618 Any &'Sender:'& header line is left alone (in this respect, it is a
27619 dynamic version of &%local_sender_retain%&).
27620 .next
27621 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
27622 .next
27623 There is no check that &'From:'& corresponds to the actual sender.
27624 .endlist ilist
27625
27626 This control may be useful when a remotely-originated message is accepted,
27627 passed to some scanning program, and then re-submitted for delivery. It can be
27628 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
27629 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
27630 data is read.
27631
27632 &*Note:*& This control applies only to the current message, not to any others
27633 that are being submitted at the same time using &%-bs%& or &%-bS%&.
27634 .endlist vlist
27635
27636
27637 .section "Summary of message fixup control" "SECTsummesfix"
27638 All four possibilities for message fixups can be specified:
27639
27640 .ilist
27641 Locally submitted, fixups applied: the default.
27642 .next
27643 Locally submitted, no fixups applied: use
27644 &`control = suppress_local_fixups`&.
27645 .next
27646 Remotely submitted, no fixups applied: the default.
27647 .next
27648 Remotely submitted, fixups applied: use &`control = submission`&.
27649 .endlist
27650
27651
27652
27653 .section "Adding header lines in ACLs" "SECTaddheadacl"
27654 .cindex "header lines" "adding in an ACL"
27655 .cindex "header lines" "position of added lines"
27656 .cindex "&%add_header%& ACL modifier"
27657 The &%add_header%& modifier can be used to add one or more extra header lines
27658 to an incoming message, as in this example:
27659 .code
27660 warn dnslists = sbl.spamhaus.org : \
27661 dialup.mail-abuse.org
27662 add_header = X-blacklisted-at: $dnslist_domain
27663 .endd
27664 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
27665 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
27666 receiving a message). The message must ultimately be accepted for
27667 &%add_header%& to have any significant effect. You can use &%add_header%& with
27668 any ACL verb, including &%deny%& (though this is potentially useful only in a
27669 RCPT ACL).
27670
27671 Headers will not be added to the message if the modifier is used in
27672 DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing.
27673
27674 Leading and trailing newlines are removed from
27675 the data for the &%add_header%& modifier; if it then
27676 contains one or more newlines that
27677 are not followed by a space or a tab, it is assumed to contain multiple header
27678 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
27679 front of any line that is not a valid header line.
27680
27681 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
27682 They are added to the message before processing the DATA and MIME ACLs.
27683 However, if an identical header line is requested more than once, only one copy
27684 is actually added to the message. Further header lines may be accumulated
27685 during the DATA and MIME ACLs, after which they are added to the message, again
27686 with duplicates suppressed. Thus, it is possible to add two identical header
27687 lines to an SMTP message, but only if one is added before DATA and one after.
27688 In the case of non-SMTP messages, new headers are accumulated during the
27689 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
27690 message is rejected after DATA or by the non-SMTP ACL, all added header lines
27691 are included in the entry that is written to the reject log.
27692
27693 .cindex "header lines" "added; visibility of"
27694 Header lines are not visible in string expansions
27695 of message headers
27696 until they are added to the
27697 message. It follows that header lines defined in the MAIL, RCPT, and predata
27698 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
27699 header lines that are added by the DATA or MIME ACLs are not visible in those
27700 ACLs. Because of this restriction, you cannot use header lines as a way of
27701 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
27702 this, you can use ACL variables, as described in section
27703 &<<SECTaclvariables>>&.
27704
27705 The list of headers yet to be added is given by the &%$headers_added%& variable.
27706
27707 The &%add_header%& modifier acts immediately as it is encountered during the
27708 processing of an ACL. Notice the difference between these two cases:
27709 .display
27710 &`accept add_header = ADDED: some text`&
27711 &` `&<&'some condition'&>
27712
27713 &`accept `&<&'some condition'&>
27714 &` add_header = ADDED: some text`&
27715 .endd
27716 In the first case, the header line is always added, whether or not the
27717 condition is true. In the second case, the header line is added only if the
27718 condition is true. Multiple occurrences of &%add_header%& may occur in the same
27719 ACL statement. All those that are encountered before a condition fails are
27720 honoured.
27721
27722 .cindex "&%warn%& ACL verb"
27723 For compatibility with previous versions of Exim, a &%message%& modifier for a
27724 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
27725 effect only if all the conditions are true, even if it appears before some of
27726 them. Furthermore, only the last occurrence of &%message%& is honoured. This
27727 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
27728 are present on a &%warn%& verb, both are processed according to their
27729 specifications.
27730
27731 By default, new header lines are added to a message at the end of the existing
27732 header lines. However, you can specify that any particular header line should
27733 be added right at the start (before all the &'Received:'& lines), immediately
27734 after the first block of &'Received:'& lines, or immediately before any line
27735 that is not a &'Received:'& or &'Resent-something:'& header.
27736
27737 This is done by specifying &":at_start:"&, &":after_received:"&, or
27738 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
27739 header line, respectively. (Header text cannot start with a colon, as there has
27740 to be a header name first.) For example:
27741 .code
27742 warn add_header = \
27743 :after_received:X-My-Header: something or other...
27744 .endd
27745 If more than one header line is supplied in a single &%add_header%& modifier,
27746 each one is treated independently and can therefore be placed differently. If
27747 you add more than one line at the start, or after the Received: block, they end
27748 up in reverse order.
27749
27750 &*Warning*&: This facility currently applies only to header lines that are
27751 added in an ACL. It does NOT work for header lines that are added in a
27752 system filter or in a router or transport.
27753
27754
27755
27756 .section "Removing header lines in ACLs" "SECTremoveheadacl"
27757 .cindex "header lines" "removing in an ACL"
27758 .cindex "header lines" "position of removed lines"
27759 .cindex "&%remove_header%& ACL modifier"
27760 The &%remove_header%& modifier can be used to remove one or more header lines
27761 from an incoming message, as in this example:
27762 .code
27763 warn message = Remove internal headers
27764 remove_header = x-route-mail1 : x-route-mail2
27765 .endd
27766 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
27767 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
27768 receiving a message). The message must ultimately be accepted for
27769 &%remove_header%& to have any significant effect. You can use &%remove_header%&
27770 with any ACL verb, including &%deny%&, though this is really not useful for
27771 any verb that doesn't result in a delivered message.
27772
27773 Headers will not be removed to the message if the modifier is used in
27774 DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing.
27775
27776 More than one header can be removed at the same time by using a colon separated
27777 list of header names. The header matching is case insensitive. Wildcards are
27778 not permitted, nor is list expansion performed, so you cannot use hostlists to
27779 create a list of headers, however both connection and message variable expansion
27780 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
27781 .code
27782 warn hosts = +internal_hosts
27783 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
27784 warn message = Remove internal headers
27785 remove_header = $acl_c_ihdrs
27786 .endd
27787 Removed header lines are accumulated during the MAIL, RCPT, and predata ACLs.
27788 They are removed from the message before processing the DATA and MIME ACLs.
27789 There is no harm in attempting to remove the same header twice nor is removing
27790 a non-existent header. Further header lines to be removed may be accumulated
27791 during the DATA and MIME ACLs, after which they are removed from the message,
27792 if present. In the case of non-SMTP messages, headers to be removed are
27793 accumulated during the non-SMTP ACLs, and are removed from the message after
27794 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
27795 ACL, there really is no effect because there is no logging of what headers
27796 would have been removed.
27797
27798 .cindex "header lines" "removed; visibility of"
27799 Header lines are not visible in string expansions until the DATA phase when it
27800 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
27801 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
27802 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
27803 this restriction, you cannot use header lines as a way of controlling data
27804 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
27805 you should instead use ACL variables, as described in section
27806 &<<SECTaclvariables>>&.
27807
27808 The &%remove_header%& modifier acts immediately as it is encountered during the
27809 processing of an ACL. Notice the difference between these two cases:
27810 .display
27811 &`accept remove_header = X-Internal`&
27812 &` `&<&'some condition'&>
27813
27814 &`accept `&<&'some condition'&>
27815 &` remove_header = X-Internal`&
27816 .endd
27817 In the first case, the header line is always removed, whether or not the
27818 condition is true. In the second case, the header line is removed only if the
27819 condition is true. Multiple occurrences of &%remove_header%& may occur in the
27820 same ACL statement. All those that are encountered before a condition fails
27821 are honoured.
27822
27823 &*Warning*&: This facility currently applies only to header lines that are
27824 present during ACL processing. It does NOT remove header lines that are added
27825 in a system filter or in a router or transport.
27826
27827
27828
27829
27830 .section "ACL conditions" "SECTaclconditions"
27831 .cindex "&ACL;" "conditions; list of"
27832 Some of the conditions listed in this section are available only when Exim is
27833 compiled with the content-scanning extension. They are included here briefly
27834 for completeness. More detailed descriptions can be found in the discussion on
27835 content scanning in chapter &<<CHAPexiscan>>&.
27836
27837 Not all conditions are relevant in all circumstances. For example, testing
27838 senders and recipients does not make sense in an ACL that is being run as the
27839 result of the arrival of an ETRN command, and checks on message headers can be
27840 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
27841 can use the same condition (with different parameters) more than once in the
27842 same ACL statement. This provides a way of specifying an &"and"& conjunction.
27843 The conditions are as follows:
27844
27845
27846 .vlist
27847 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
27848 .cindex "&ACL;" "nested"
27849 .cindex "&ACL;" "indirect"
27850 .cindex "&ACL;" "arguments"
27851 .cindex "&%acl%& ACL condition"
27852 The possible values of the argument are the same as for the
27853 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
27854 &"accept"& the condition is true; if it returns &"deny"& the condition is
27855 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
27856 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
27857 condition false. This means that further processing of the &%warn%& verb
27858 ceases, but processing of the ACL continues.
27859
27860 If the argument is a named ACL, up to nine space-separated optional values
27861 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
27862 and $acl_narg is set to the count of values.
27863 Previous values of these variables are restored after the call returns.
27864 The name and values are expanded separately.
27865
27866 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
27867 the connection is dropped. If it returns &"discard"&, the verb must be
27868 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
27869 conditions are tested.
27870
27871 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
27872 loops. This condition allows you to use different ACLs in different
27873 circumstances. For example, different ACLs can be used to handle RCPT commands
27874 for different local users or different local domains.
27875
27876 .vitem &*authenticated&~=&~*&<&'string&~list'&>
27877 .cindex "&%authenticated%& ACL condition"
27878 .cindex "authentication" "ACL checking"
27879 .cindex "&ACL;" "testing for authentication"
27880 If the SMTP connection is not authenticated, the condition is false. Otherwise,
27881 the name of the authenticator is tested against the list. To test for
27882 authentication by any authenticator, you can set
27883 .code
27884 authenticated = *
27885 .endd
27886
27887 .vitem &*condition&~=&~*&<&'string'&>
27888 .cindex "&%condition%& ACL condition"
27889 .cindex "customizing" "ACL condition"
27890 .cindex "&ACL;" "customized test"
27891 .cindex "&ACL;" "testing, customized"
27892 This feature allows you to make up custom conditions. If the result of
27893 expanding the string is an empty string, the number zero, or one of the strings
27894 &"no"& or &"false"&, the condition is false. If the result is any non-zero
27895 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
27896 any other value, some error is assumed to have occurred, and the ACL returns
27897 &"defer"&. However, if the expansion is forced to fail, the condition is
27898 ignored. The effect is to treat it as true, whether it is positive or
27899 negative.
27900
27901 .vitem &*decode&~=&~*&<&'location'&>
27902 .cindex "&%decode%& ACL condition"
27903 This condition is available only when Exim is compiled with the
27904 content-scanning extension, and it is allowed only in the ACL defined by
27905 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
27906 If all goes well, the condition is true. It is false only if there are
27907 problems such as a syntax error or a memory shortage. For more details, see
27908 chapter &<<CHAPexiscan>>&.
27909
27910 .vitem &*demime&~=&~*&<&'extension&~list'&>
27911 .cindex "&%demime%& ACL condition"
27912 This condition is available only when Exim is compiled with the
27913 content-scanning extension. Its use is described in section
27914 &<<SECTdemimecond>>&.
27915
27916 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
27917 .cindex "&%dnslists%& ACL condition"
27918 .cindex "DNS list" "in ACL"
27919 .cindex "black list (DNS)"
27920 .cindex "&ACL;" "testing a DNS list"
27921 This condition checks for entries in DNS black lists. These are also known as
27922 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
27923 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
27924 different variants of this condition to describe briefly here. See sections
27925 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
27926
27927 .vitem &*domains&~=&~*&<&'domain&~list'&>
27928 .cindex "&%domains%& ACL condition"
27929 .cindex "domain" "ACL checking"
27930 .cindex "&ACL;" "testing a recipient domain"
27931 .vindex "&$domain_data$&"
27932 This condition is relevant only after a RCPT command. It checks that the domain
27933 of the recipient address is in the domain list. If percent-hack processing is
27934 enabled, it is done before this test is done. If the check succeeds with a
27935 lookup, the result of the lookup is placed in &$domain_data$& until the next
27936 &%domains%& test.
27937
27938 &*Note carefully*& (because many people seem to fall foul of this): you cannot
27939 use &%domains%& in a DATA ACL.
27940
27941
27942 .vitem &*encrypted&~=&~*&<&'string&~list'&>
27943 .cindex "&%encrypted%& ACL condition"
27944 .cindex "encryption" "checking in an ACL"
27945 .cindex "&ACL;" "testing for encryption"
27946 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
27947 name of the cipher suite in use is tested against the list. To test for
27948 encryption without testing for any specific cipher suite(s), set
27949 .code
27950 encrypted = *
27951 .endd
27952
27953
27954 .vitem &*hosts&~=&~*&<&'host&~list'&>
27955 .cindex "&%hosts%& ACL condition"
27956 .cindex "host" "ACL checking"
27957 .cindex "&ACL;" "testing the client host"
27958 This condition tests that the calling host matches the host list. If you have
27959 name lookups or wildcarded host names and IP addresses in the same host list,
27960 you should normally put the IP addresses first. For example, you could have:
27961 .code
27962 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
27963 .endd
27964 The lookup in this example uses the host name for its key. This is implied by
27965 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
27966 and it wouldn't matter which way round you had these two items.)
27967
27968 The reason for the problem with host names lies in the left-to-right way that
27969 Exim processes lists. It can test IP addresses without doing any DNS lookups,
27970 but when it reaches an item that requires a host name, it fails if it cannot
27971 find a host name to compare with the pattern. If the above list is given in the
27972 opposite order, the &%accept%& statement fails for a host whose name cannot be
27973 found, even if its IP address is 10.9.8.7.
27974
27975 If you really do want to do the name check first, and still recognize the IP
27976 address even if the name lookup fails, you can rewrite the ACL like this:
27977 .code
27978 accept hosts = dbm;/etc/friendly/hosts
27979 accept hosts = 10.9.8.7
27980 .endd
27981 The default action on failing to find the host name is to assume that the host
27982 is not in the list, so the first &%accept%& statement fails. The second
27983 statement can then check the IP address.
27984
27985 .vindex "&$host_data$&"
27986 If a &%hosts%& condition is satisfied by means of a lookup, the result
27987 of the lookup is made available in the &$host_data$& variable. This
27988 allows you, for example, to set up a statement like this:
27989 .code
27990 deny hosts = net-lsearch;/some/file
27991 message = $host_data
27992 .endd
27993 which gives a custom error message for each denied host.
27994
27995 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
27996 .cindex "&%local_parts%& ACL condition"
27997 .cindex "local part" "ACL checking"
27998 .cindex "&ACL;" "testing a local part"
27999 .vindex "&$local_part_data$&"
28000 This condition is relevant only after a RCPT command. It checks that the local
28001 part of the recipient address is in the list. If percent-hack processing is
28002 enabled, it is done before this test. If the check succeeds with a lookup, the
28003 result of the lookup is placed in &$local_part_data$&, which remains set until
28004 the next &%local_parts%& test.
28005
28006 .vitem &*malware&~=&~*&<&'option'&>
28007 .cindex "&%malware%& ACL condition"
28008 .cindex "&ACL;" "virus scanning"
28009 .cindex "&ACL;" "scanning for viruses"
28010 This condition is available only when Exim is compiled with the
28011 content-scanning extension. It causes the incoming message to be scanned for
28012 viruses. For details, see chapter &<<CHAPexiscan>>&.
28013
28014 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
28015 .cindex "&%mime_regex%& ACL condition"
28016 .cindex "&ACL;" "testing by regex matching"
28017 This condition is available only when Exim is compiled with the
28018 content-scanning extension, and it is allowed only in the ACL defined by
28019 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
28020 with any of the regular expressions. For details, see chapter
28021 &<<CHAPexiscan>>&.
28022
28023 .vitem &*ratelimit&~=&~*&<&'parameters'&>
28024 .cindex "rate limiting"
28025 This condition can be used to limit the rate at which a user or host submits
28026 messages. Details are given in section &<<SECTratelimiting>>&.
28027
28028 .vitem &*recipients&~=&~*&<&'address&~list'&>
28029 .cindex "&%recipients%& ACL condition"
28030 .cindex "recipient" "ACL checking"
28031 .cindex "&ACL;" "testing a recipient"
28032 This condition is relevant only after a RCPT command. It checks the entire
28033 recipient address against a list of recipients.
28034
28035 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
28036 .cindex "&%regex%& ACL condition"
28037 .cindex "&ACL;" "testing by regex matching"
28038 This condition is available only when Exim is compiled with the
28039 content-scanning extension, and is available only in the DATA, MIME, and
28040 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
28041 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
28042
28043 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
28044 .cindex "&%sender_domains%& ACL condition"
28045 .cindex "sender" "ACL checking"
28046 .cindex "&ACL;" "testing a sender domain"
28047 .vindex "&$domain$&"
28048 .vindex "&$sender_address_domain$&"
28049 This condition tests the domain of the sender of the message against the given
28050 domain list. &*Note*&: The domain of the sender address is in
28051 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
28052 of this condition. This is an exception to the general rule for testing domain
28053 lists. It is done this way so that, if this condition is used in an ACL for a
28054 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
28055 influence the sender checking.
28056
28057 &*Warning*&: It is a bad idea to use this condition on its own as a control on
28058 relaying, because sender addresses are easily, and commonly, forged.
28059
28060 .vitem &*senders&~=&~*&<&'address&~list'&>
28061 .cindex "&%senders%& ACL condition"
28062 .cindex "sender" "ACL checking"
28063 .cindex "&ACL;" "testing a sender"
28064 This condition tests the sender of the message against the given list. To test
28065 for a bounce message, which has an empty sender, set
28066 .code
28067 senders = :
28068 .endd
28069 &*Warning*&: It is a bad idea to use this condition on its own as a control on
28070 relaying, because sender addresses are easily, and commonly, forged.
28071
28072 .vitem &*spam&~=&~*&<&'username'&>
28073 .cindex "&%spam%& ACL condition"
28074 .cindex "&ACL;" "scanning for spam"
28075 This condition is available only when Exim is compiled with the
28076 content-scanning extension. It causes the incoming message to be scanned by
28077 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
28078
28079 .vitem &*verify&~=&~certificate*&
28080 .cindex "&%verify%& ACL condition"
28081 .cindex "TLS" "client certificate verification"
28082 .cindex "certificate" "verification of client"
28083 .cindex "&ACL;" "certificate verification"
28084 .cindex "&ACL;" "testing a TLS certificate"
28085 This condition is true in an SMTP session if the session is encrypted, and a
28086 certificate was received from the client, and the certificate was verified. The
28087 server requests a certificate only if the client matches &%tls_verify_hosts%&
28088 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
28089
28090 .vitem &*verify&~=&~csa*&
28091 .cindex "CSA verification"
28092 This condition checks whether the sending host (the client) is authorized to
28093 send email. Details of how this works are given in section
28094 &<<SECTverifyCSA>>&.
28095
28096 .new
28097 .vitem &*verify&~=&~header_names_ascii*&
28098 .cindex "&%verify%& ACL condition"
28099 .cindex "&ACL;" "verifying header names only ASCII"
28100 .cindex "header lines" "verifying header names only ASCII"
28101 .cindex "verifying" "header names only ASCII"
28102 This condition is relevant only in an ACL that is run after a message has been
28103 received, that is, in an ACL specified by &%acl_smtp_data%& or
28104 &%acl_not_smtp%&. It checks all header names (not the content) to make sure
28105 there are no non-ASCII characters, also excluding control characters. The
28106 allowable characters are decimal ASCII values 33 through 126.
28107
28108 Exim itself will handle headers with non-ASCII characters, but it can cause
28109 problems for downstream applications, so this option will allow their
28110 detection and rejection in the DATA ACL's.
28111 .wen
28112
28113 .vitem &*verify&~=&~header_sender/*&<&'options'&>
28114 .cindex "&%verify%& ACL condition"
28115 .cindex "&ACL;" "verifying sender in the header"
28116 .cindex "header lines" "verifying the sender in"
28117 .cindex "sender" "verifying in header"
28118 .cindex "verifying" "sender in header"
28119 This condition is relevant only in an ACL that is run after a message has been
28120 received, that is, in an ACL specified by &%acl_smtp_data%& or
28121 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
28122 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
28123 is loosely thought of as a &"sender"& address (hence the name of the test).
28124 However, an address that appears in one of these headers need not be an address
28125 that accepts bounce messages; only sender addresses in envelopes are required
28126 to accept bounces. Therefore, if you use the callout option on this check, you
28127 might want to arrange for a non-empty address in the MAIL command.
28128
28129 Details of address verification and the options are given later, starting at
28130 section &<<SECTaddressverification>>& (callouts are described in section
28131 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
28132 condition to restrict it to bounce messages only:
28133 .code
28134 deny senders = :
28135 message = A valid sender header is required for bounces
28136 !verify = header_sender
28137 .endd
28138
28139 .vitem &*verify&~=&~header_syntax*&
28140 .cindex "&%verify%& ACL condition"
28141 .cindex "&ACL;" "verifying header syntax"
28142 .cindex "header lines" "verifying syntax"
28143 .cindex "verifying" "header syntax"
28144 This condition is relevant only in an ACL that is run after a message has been
28145 received, that is, in an ACL specified by &%acl_smtp_data%& or
28146 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
28147 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
28148 and &'Bcc:'&). Unqualified addresses (local parts without domains) are
28149 permitted only in locally generated messages and from hosts that match
28150 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
28151 appropriate.
28152
28153 Note that this condition is a syntax check only. However, a common spamming
28154 ploy used to be to send syntactically invalid headers such as
28155 .code
28156 To: @
28157 .endd
28158 and this condition can be used to reject such messages, though they are not as
28159 common as they used to be.
28160
28161 .vitem &*verify&~=&~helo*&
28162 .cindex "&%verify%& ACL condition"
28163 .cindex "&ACL;" "verifying HELO/EHLO"
28164 .cindex "HELO" "verifying"
28165 .cindex "EHLO" "verifying"
28166 .cindex "verifying" "EHLO"
28167 .cindex "verifying" "HELO"
28168 This condition is true if a HELO or EHLO command has been received from the
28169 client host, and its contents have been verified. If there has been no previous
28170 attempt to verify the HELO/EHLO contents, it is carried out when this
28171 condition is encountered. See the description of the &%helo_verify_hosts%& and
28172 &%helo_try_verify_hosts%& options for details of how to request verification
28173 independently of this condition.
28174
28175 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
28176 option), this condition is always true.
28177
28178
28179 .vitem &*verify&~=&~not_blind*&
28180 .cindex "verifying" "not blind"
28181 .cindex "bcc recipients, verifying none"
28182 This condition checks that there are no blind (bcc) recipients in the message.
28183 Every envelope recipient must appear either in a &'To:'& header line or in a
28184 &'Cc:'& header line for this condition to be true. Local parts are checked
28185 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
28186 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
28187 used only in a DATA or non-SMTP ACL.
28188
28189 There are, of course, many legitimate messages that make use of blind (bcc)
28190 recipients. This check should not be used on its own for blocking messages.
28191
28192
28193 .vitem &*verify&~=&~recipient/*&<&'options'&>
28194 .cindex "&%verify%& ACL condition"
28195 .cindex "&ACL;" "verifying recipient"
28196 .cindex "recipient" "verifying"
28197 .cindex "verifying" "recipient"
28198 .vindex "&$address_data$&"
28199 This condition is relevant only after a RCPT command. It verifies the current
28200 recipient. Details of address verification are given later, starting at section
28201 &<<SECTaddressverification>>&. After a recipient has been verified, the value
28202 of &$address_data$& is the last value that was set while routing the address.
28203 This applies even if the verification fails. When an address that is being
28204 verified is redirected to a single address, verification continues with the new
28205 address, and in that case, the subsequent value of &$address_data$& is the
28206 value for the child address.
28207
28208 .vitem &*verify&~=&~reverse_host_lookup*&
28209 .cindex "&%verify%& ACL condition"
28210 .cindex "&ACL;" "verifying host reverse lookup"
28211 .cindex "host" "verifying reverse lookup"
28212 This condition ensures that a verified host name has been looked up from the IP
28213 address of the client host. (This may have happened already if the host name
28214 was needed for checking a host list, or if the host matched &%host_lookup%&.)
28215 Verification ensures that the host name obtained from a reverse DNS lookup, or
28216 one of its aliases, does, when it is itself looked up in the DNS, yield the
28217 original IP address.
28218
28219 If this condition is used for a locally generated message (that is, when there
28220 is no client host involved), it always succeeds.
28221
28222 .vitem &*verify&~=&~sender/*&<&'options'&>
28223 .cindex "&%verify%& ACL condition"
28224 .cindex "&ACL;" "verifying sender"
28225 .cindex "sender" "verifying"
28226 .cindex "verifying" "sender"
28227 This condition is relevant only after a MAIL or RCPT command, or after a
28228 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
28229 the message's sender is empty (that is, this is a bounce message), the
28230 condition is true. Otherwise, the sender address is verified.
28231
28232 .vindex "&$address_data$&"
28233 .vindex "&$sender_address_data$&"
28234 If there is data in the &$address_data$& variable at the end of routing, its
28235 value is placed in &$sender_address_data$& at the end of verification. This
28236 value can be used in subsequent conditions and modifiers in the same ACL
28237 statement. It does not persist after the end of the current statement. If you
28238 want to preserve the value for longer, you can save it in an ACL variable.
28239
28240 Details of verification are given later, starting at section
28241 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
28242 to avoid doing it more than once per message.
28243
28244 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
28245 .cindex "&%verify%& ACL condition"
28246 This is a variation of the previous option, in which a modified address is
28247 verified as a sender.
28248 .endlist
28249
28250
28251
28252 .section "Using DNS lists" "SECTmorednslists"
28253 .cindex "DNS list" "in ACL"
28254 .cindex "black list (DNS)"
28255 .cindex "&ACL;" "testing a DNS list"
28256 In its simplest form, the &%dnslists%& condition tests whether the calling host
28257 is on at least one of a number of DNS lists by looking up the inverted IP
28258 address in one or more DNS domains. (Note that DNS list domains are not mail
28259 domains, so the &`+`& syntax for named lists doesn't work - it is used for
28260 special options instead.) For example, if the calling host's IP
28261 address is 192.168.62.43, and the ACL statement is
28262 .code
28263 deny dnslists = blackholes.mail-abuse.org : \
28264 dialups.mail-abuse.org
28265 .endd
28266 the following records are looked up:
28267 .code
28268 43.62.168.192.blackholes.mail-abuse.org
28269 43.62.168.192.dialups.mail-abuse.org
28270 .endd
28271 As soon as Exim finds an existing DNS record, processing of the list stops.
28272 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
28273 to test that a host is on more than one list (an &"and"& conjunction), you can
28274 use two separate conditions:
28275 .code
28276 deny dnslists = blackholes.mail-abuse.org
28277 dnslists = dialups.mail-abuse.org
28278 .endd
28279 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
28280 behaves as if the host does not match the list item, that is, as if the DNS
28281 record does not exist. If there are further items in the DNS list, they are
28282 processed.
28283
28284 This is usually the required action when &%dnslists%& is used with &%deny%&
28285 (which is the most common usage), because it prevents a DNS failure from
28286 blocking mail. However, you can change this behaviour by putting one of the
28287 following special items in the list:
28288 .display
28289 &`+include_unknown `& behave as if the item is on the list
28290 &`+exclude_unknown `& behave as if the item is not on the list (default)
28291 &`+defer_unknown `& give a temporary error
28292 .endd
28293 .cindex "&`+include_unknown`&"
28294 .cindex "&`+exclude_unknown`&"
28295 .cindex "&`+defer_unknown`&"
28296 Each of these applies to any subsequent items on the list. For example:
28297 .code
28298 deny dnslists = +defer_unknown : foo.bar.example
28299 .endd
28300 Testing the list of domains stops as soon as a match is found. If you want to
28301 warn for one list and block for another, you can use two different statements:
28302 .code
28303 deny dnslists = blackholes.mail-abuse.org
28304 warn message = X-Warn: sending host is on dialups list
28305 dnslists = dialups.mail-abuse.org
28306 .endd
28307 DNS list lookups are cached by Exim for the duration of the SMTP session,
28308 so a lookup based on the IP address is done at most once for any incoming
28309 connection. Exim does not share information between multiple incoming
28310 connections (but your local name server cache should be active).
28311
28312
28313
28314 .section "Specifying the IP address for a DNS list lookup" "SECID201"
28315 .cindex "DNS list" "keyed by explicit IP address"
28316 By default, the IP address that is used in a DNS list lookup is the IP address
28317 of the calling host. However, you can specify another IP address by listing it
28318 after the domain name, introduced by a slash. For example:
28319 .code
28320 deny dnslists = black.list.tld/192.168.1.2
28321 .endd
28322 This feature is not very helpful with explicit IP addresses; it is intended for
28323 use with IP addresses that are looked up, for example, the IP addresses of the
28324 MX hosts or nameservers of an email sender address. For an example, see section
28325 &<<SECTmulkeyfor>>& below.
28326
28327
28328
28329
28330 .section "DNS lists keyed on domain names" "SECID202"
28331 .cindex "DNS list" "keyed by domain name"
28332 There are some lists that are keyed on domain names rather than inverted IP
28333 addresses (see for example the &'domain based zones'& link at
28334 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
28335 with these lists. You can change the name that is looked up in a DNS list by
28336 listing it after the domain name, introduced by a slash. For example,
28337 .code
28338 deny message = Sender's domain is listed at $dnslist_domain
28339 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
28340 .endd
28341 This particular example is useful only in ACLs that are obeyed after the
28342 RCPT or DATA commands, when a sender address is available. If (for
28343 example) the message's sender is &'user@tld.example'& the name that is looked
28344 up by this example is
28345 .code
28346 tld.example.dsn.rfc-ignorant.org
28347 .endd
28348 A single &%dnslists%& condition can contain entries for both names and IP
28349 addresses. For example:
28350 .code
28351 deny dnslists = sbl.spamhaus.org : \
28352 dsn.rfc-ignorant.org/$sender_address_domain
28353 .endd
28354 The first item checks the sending host's IP address; the second checks a domain
28355 name. The whole condition is true if either of the DNS lookups succeeds.
28356
28357
28358
28359
28360 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
28361 .cindex "DNS list" "multiple keys for"
28362 The syntax described above for looking up explicitly-defined values (either
28363 names or IP addresses) in a DNS blacklist is a simplification. After the domain
28364 name for the DNS list, what follows the slash can in fact be a list of items.
28365 As with all lists in Exim, the default separator is a colon. However, because
28366 this is a sublist within the list of DNS blacklist domains, it is necessary
28367 either to double the separators like this:
28368 .code
28369 dnslists = black.list.tld/name.1::name.2
28370 .endd
28371 or to change the separator character, like this:
28372 .code
28373 dnslists = black.list.tld/<;name.1;name.2
28374 .endd
28375 If an item in the list is an IP address, it is inverted before the DNS
28376 blacklist domain is appended. If it is not an IP address, no inversion
28377 occurs. Consider this condition:
28378 .code
28379 dnslists = black.list.tld/<;192.168.1.2;a.domain
28380 .endd
28381 The DNS lookups that occur are:
28382 .code
28383 2.1.168.192.black.list.tld
28384 a.domain.black.list.tld
28385 .endd
28386 Once a DNS record has been found (that matches a specific IP return
28387 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
28388 are done. If there is a temporary DNS error, the rest of the sublist of domains
28389 or IP addresses is tried. A temporary error for the whole dnslists item occurs
28390 only if no other DNS lookup in this sublist succeeds. In other words, a
28391 successful lookup for any of the items in the sublist overrides a temporary
28392 error for a previous item.
28393
28394 The ability to supply a list of items after the slash is in some sense just a
28395 syntactic convenience. These two examples have the same effect:
28396 .code
28397 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
28398 dnslists = black.list.tld/a.domain::b.domain
28399 .endd
28400 However, when the data for the list is obtained from a lookup, the second form
28401 is usually much more convenient. Consider this example:
28402 .code
28403 deny message = The mail servers for the domain \
28404 $sender_address_domain \
28405 are listed at $dnslist_domain ($dnslist_value); \
28406 see $dnslist_text.
28407 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
28408 ${lookup dnsdb {>|mxh=\
28409 $sender_address_domain} }} }
28410 .endd
28411 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
28412 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
28413 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
28414 of expanding the condition might be something like this:
28415 .code
28416 dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|...
28417 .endd
28418 Thus, this example checks whether or not the IP addresses of the sender
28419 domain's mail servers are on the Spamhaus black list.
28420
28421 The key that was used for a successful DNS list lookup is put into the variable
28422 &$dnslist_matched$& (see section &<<SECID204>>&).
28423
28424
28425
28426
28427 .section "Data returned by DNS lists" "SECID203"
28428 .cindex "DNS list" "data returned from"
28429 DNS lists are constructed using address records in the DNS. The original RBL
28430 just used the address 127.0.0.1 on the right hand side of each record, but the
28431 RBL+ list and some other lists use a number of values with different meanings.
28432 The values used on the RBL+ list are:
28433 .display
28434 127.1.0.1 RBL
28435 127.1.0.2 DUL
28436 127.1.0.3 DUL and RBL
28437 127.1.0.4 RSS
28438 127.1.0.5 RSS and RBL
28439 127.1.0.6 RSS and DUL
28440 127.1.0.7 RSS and DUL and RBL
28441 .endd
28442 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
28443 different values. Some DNS lists may return more than one address record;
28444 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
28445
28446
28447 .section "Variables set from DNS lists" "SECID204"
28448 .cindex "expansion" "variables, set from DNS list"
28449 .cindex "DNS list" "variables set from"
28450 .vindex "&$dnslist_domain$&"
28451 .vindex "&$dnslist_matched$&"
28452 .vindex "&$dnslist_text$&"
28453 .vindex "&$dnslist_value$&"
28454 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
28455 the name of the overall domain that matched (for example,
28456 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
28457 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
28458 the DNS record. When the key is an IP address, it is not reversed in
28459 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
28460 cases, for example:
28461 .code
28462 deny dnslists = spamhaus.example
28463 .endd
28464 the key is also available in another variable (in this case,
28465 &$sender_host_address$&). In more complicated cases, however, this is not true.
28466 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
28467 might generate a dnslists lookup like this:
28468 .code
28469 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
28470 .endd
28471 If this condition succeeds, the value in &$dnslist_matched$& might be
28472 &`192.168.6.7`& (for example).
28473
28474 If more than one address record is returned by the DNS lookup, all the IP
28475 addresses are included in &$dnslist_value$&, separated by commas and spaces.
28476 The variable &$dnslist_text$& contains the contents of any associated TXT
28477 record. For lists such as RBL+ the TXT record for a merged entry is often not
28478 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
28479 information.
28480
28481 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
28482 &-- although these appear before the condition in the ACL, they are not
28483 expanded until after it has failed. For example:
28484 .code
28485 deny hosts = !+local_networks
28486 message = $sender_host_address is listed \
28487 at $dnslist_domain
28488 dnslists = rbl-plus.mail-abuse.example
28489 .endd
28490
28491
28492
28493 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
28494 .cindex "DNS list" "matching specific returned data"
28495 You can add an equals sign and an IP address after a &%dnslists%& domain name
28496 in order to restrict its action to DNS records with a matching right hand side.
28497 For example,
28498 .code
28499 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
28500 .endd
28501 rejects only those hosts that yield 127.0.0.2. Without this additional data,
28502 any address record is considered to be a match. For the moment, we assume
28503 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
28504 describes how multiple records are handled.
28505
28506 More than one IP address may be given for checking, using a comma as a
28507 separator. These are alternatives &-- if any one of them matches, the
28508 &%dnslists%& condition is true. For example:
28509 .code
28510 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
28511 .endd
28512 If you want to specify a constraining address list and also specify names or IP
28513 addresses to be looked up, the constraining address list must be specified
28514 first. For example:
28515 .code
28516 deny dnslists = dsn.rfc-ignorant.org\
28517 =127.0.0.2/$sender_address_domain
28518 .endd
28519
28520 If the character &`&&`& is used instead of &`=`&, the comparison for each
28521 listed IP address is done by a bitwise &"and"& instead of by an equality test.
28522 In other words, the listed addresses are used as bit masks. The comparison is
28523 true if all the bits in the mask are present in the address that is being
28524 tested. For example:
28525 .code
28526 dnslists = a.b.c&0.0.0.3
28527 .endd
28528 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
28529 want to test whether one bit or another bit is present (as opposed to both
28530 being present), you must use multiple values. For example:
28531 .code
28532 dnslists = a.b.c&0.0.0.1,0.0.0.2
28533 .endd
28534 matches if the final component of the address is an odd number or two times
28535 an odd number.
28536
28537
28538
28539 .section "Negated DNS matching conditions" "SECID205"
28540 You can supply a negative list of IP addresses as part of a &%dnslists%&
28541 condition. Whereas
28542 .code
28543 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
28544 .endd
28545 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
28546 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
28547 .code
28548 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
28549 .endd
28550 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
28551 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
28552 words, the result of the test is inverted if an exclamation mark appears before
28553 the &`=`& (or the &`&&`&) sign.
28554
28555 &*Note*&: This kind of negation is not the same as negation in a domain,
28556 host, or address list (which is why the syntax is different).
28557
28558 If you are using just one list, the negation syntax does not gain you much. The
28559 previous example is precisely equivalent to
28560 .code
28561 deny dnslists = a.b.c
28562 !dnslists = a.b.c=127.0.0.2,127.0.0.3
28563 .endd
28564 However, if you are using multiple lists, the negation syntax is clearer.
28565 Consider this example:
28566 .code
28567 deny dnslists = sbl.spamhaus.org : \
28568 list.dsbl.org : \
28569 dnsbl.njabl.org!=127.0.0.3 : \
28570 relays.ordb.org
28571 .endd
28572 Using only positive lists, this would have to be:
28573 .code
28574 deny dnslists = sbl.spamhaus.org : \
28575 list.dsbl.org
28576 deny dnslists = dnsbl.njabl.org
28577 !dnslists = dnsbl.njabl.org=127.0.0.3
28578 deny dnslists = relays.ordb.org
28579 .endd
28580 which is less clear, and harder to maintain.
28581
28582
28583
28584
28585 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
28586 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
28587 thereby providing more than one IP address. When an item in a &%dnslists%& list
28588 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
28589 the match to specific results from the DNS lookup, there are two ways in which
28590 the checking can be handled. For example, consider the condition:
28591 .code
28592 dnslists = a.b.c=127.0.0.1
28593 .endd
28594 What happens if the DNS lookup for the incoming IP address yields both
28595 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
28596 condition true because at least one given value was found, or is it false
28597 because at least one of the found values was not listed? And how does this
28598 affect negated conditions? Both possibilities are provided for with the help of
28599 additional separators &`==`& and &`=&&`&.
28600
28601 .ilist
28602 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
28603 IP addresses matches one of the listed addresses. For the example above, the
28604 condition is true because 127.0.0.1 matches.
28605 .next
28606 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
28607 looked up IP addresses matches one of the listed addresses. If the condition is
28608 changed to:
28609 .code
28610 dnslists = a.b.c==127.0.0.1
28611 .endd
28612 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
28613 false because 127.0.0.2 is not listed. You would need to have:
28614 .code
28615 dnslists = a.b.c==127.0.0.1,127.0.0.2
28616 .endd
28617 for the condition to be true.
28618 .endlist
28619
28620 When &`!`& is used to negate IP address matching, it inverts the result, giving
28621 the precise opposite of the behaviour above. Thus:
28622 .ilist
28623 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
28624 addresses matches one of the listed addresses. Consider:
28625 .code
28626 dnslists = a.b.c!&0.0.0.1
28627 .endd
28628 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
28629 false because 127.0.0.1 matches.
28630 .next
28631 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
28632 looked up IP address that does not match. Consider:
28633 .code
28634 dnslists = a.b.c!=&0.0.0.1
28635 .endd
28636 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
28637 true, because 127.0.0.2 does not match. You would need to have:
28638 .code
28639 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
28640 .endd
28641 for the condition to be false.
28642 .endlist
28643 When the DNS lookup yields only a single IP address, there is no difference
28644 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
28645
28646
28647
28648
28649 .section "Detailed information from merged DNS lists" "SECTmordetinf"
28650 .cindex "DNS list" "information from merged"
28651 When the facility for restricting the matching IP values in a DNS list is used,
28652 the text from the TXT record that is set in &$dnslist_text$& may not reflect
28653 the true reason for rejection. This happens when lists are merged and the IP
28654 address in the A record is used to distinguish them; unfortunately there is
28655 only one TXT record. One way round this is not to use merged lists, but that
28656 can be inefficient because it requires multiple DNS lookups where one would do
28657 in the vast majority of cases when the host of interest is not on any of the
28658 lists.
28659
28660 A less inefficient way of solving this problem is available. If
28661 two domain names, comma-separated, are given, the second is used first to
28662 do an initial check, making use of any IP value restrictions that are set.
28663 If there is a match, the first domain is used, without any IP value
28664 restrictions, to get the TXT record. As a byproduct of this, there is also
28665 a check that the IP being tested is indeed on the first list. The first
28666 domain is the one that is put in &$dnslist_domain$&. For example:
28667 .code
28668 reject message = \
28669 rejected because $sender_host_address is blacklisted \
28670 at $dnslist_domain\n$dnslist_text
28671 dnslists = \
28672 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
28673 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
28674 .endd
28675 For the first blacklist item, this starts by doing a lookup in
28676 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
28677 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
28678 value, and as long as something is found, it looks for the corresponding TXT
28679 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
28680 The second blacklist item is processed similarly.
28681
28682 If you are interested in more than one merged list, the same list must be
28683 given several times, but because the results of the DNS lookups are cached,
28684 the DNS calls themselves are not repeated. For example:
28685 .code
28686 reject dnslists = \
28687 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
28688 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
28689 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
28690 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
28691 .endd
28692 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
28693 values matches (or if no record is found), this is the only lookup that is
28694 done. Only if there is a match is one of the more specific lists consulted.
28695
28696
28697
28698 .section "DNS lists and IPv6" "SECTmorednslistslast"
28699 .cindex "IPv6" "DNS black lists"
28700 .cindex "DNS list" "IPv6 usage"
28701 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
28702 nibble by nibble. For example, if the calling host's IP address is
28703 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
28704 .code
28705 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
28706 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
28707 .endd
28708 (split over two lines here to fit on the page). Unfortunately, some of the DNS
28709 lists contain wildcard records, intended for IPv4, that interact badly with
28710 IPv6. For example, the DNS entry
28711 .code
28712 *.3.some.list.example. A 127.0.0.1
28713 .endd
28714 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
28715 Unfortunately, it also matches the entire 3::/4 IPv6 network.
28716
28717 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
28718 &%condition%& condition, as in this example:
28719 .code
28720 deny condition = ${if isip4{$sender_host_address}}
28721 dnslists = some.list.example
28722 .endd
28723
28724 If an explicit key is being used for a DNS lookup and it may be an IPv6
28725 address you should specify alternate list separators for both the outer
28726 (DNS list name) list and inner (lookup keys) list:
28727 .code
28728 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
28729 .endd
28730
28731 .section "Rate limiting incoming messages" "SECTratelimiting"
28732 .cindex "rate limiting" "client sending"
28733 .cindex "limiting client sending rates"
28734 .oindex "&%smtp_ratelimit_*%&"
28735 The &%ratelimit%& ACL condition can be used to measure and control the rate at
28736 which clients can send email. This is more powerful than the
28737 &%smtp_ratelimit_*%& options, because those options control the rate of
28738 commands in a single SMTP session only, whereas the &%ratelimit%& condition
28739 works across all connections (concurrent and sequential) from the same client
28740 host. The syntax of the &%ratelimit%& condition is:
28741 .display
28742 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
28743 .endd
28744 If the average client sending rate is less than &'m'& messages per time
28745 period &'p'& then the condition is false; otherwise it is true.
28746
28747 As a side-effect, the &%ratelimit%& condition sets the expansion variable
28748 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
28749 configured value of &'m'&, and &$sender_rate_period$& to the configured value
28750 of &'p'&.
28751
28752 The parameter &'p'& is the smoothing time constant, in the form of an Exim
28753 time interval, for example, &`8h`& for eight hours. A larger time constant
28754 means that it takes Exim longer to forget a client's past behaviour. The
28755 parameter &'m'& is the maximum number of messages that a client is permitted to
28756 send in each time interval. It also specifies the number of messages permitted
28757 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
28758 constant, you can allow a client to send more messages in a burst without
28759 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
28760 both small, messages must be sent at an even rate.
28761
28762 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
28763 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
28764 when deploying the &%ratelimit%& ACL condition. The script prints usage
28765 instructions when it is run with no arguments.
28766
28767 The key is used to look up the data for calculating the client's average
28768 sending rate. This data is stored in Exim's spool directory, alongside the
28769 retry and other hints databases. The default key is &$sender_host_address$&,
28770 which means Exim computes the sending rate of each client host IP address.
28771 By changing the key you can change how Exim identifies clients for the purpose
28772 of ratelimiting. For example, to limit the sending rate of each authenticated
28773 user, independent of the computer they are sending from, set the key to
28774 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
28775 example, &$authenticated_id$& is only meaningful if the client has
28776 authenticated (which you can check with the &%authenticated%& ACL condition).
28777
28778 The lookup key does not have to identify clients: If you want to limit the
28779 rate at which a recipient receives messages, you can use the key
28780 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
28781 ACL.
28782
28783 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
28784 specifies what Exim measures the rate of, for example messages or recipients
28785 or bytes. You can adjust the measurement using the &%unique=%& and/or
28786 &%count=%& options. You can also control when Exim updates the recorded rate
28787 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
28788 separated by a slash, like the other parameters. They may appear in any order.
28789
28790 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
28791 any options that alter the meaning of the stored data. The limit &'m'& is not
28792 stored, so you can alter the configured maximum rate and Exim will still
28793 remember clients' past behaviour. If you change the &%per_*%& mode or add or
28794 remove the &%unique=%& option, the lookup key changes so Exim will forget past
28795 behaviour. The lookup key is not affected by changes to the update mode and
28796 the &%count=%& option.
28797
28798
28799 .section "Ratelimit options for what is being measured" "ratoptmea"
28800 .cindex "rate limiting" "per_* options"
28801 The &%per_conn%& option limits the client's connection rate. It is not
28802 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
28803 &%acl_not_smtp_start%& ACLs.
28804
28805 The &%per_mail%& option limits the client's rate of sending messages. This is
28806 the default if none of the &%per_*%& options is specified. It can be used in
28807 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
28808 &%acl_smtp_data%&, or &%acl_not_smtp%&.
28809
28810 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
28811 the same ACLs as the &%per_mail%& option, though it is best to use this option
28812 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
28813 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
28814 in its MAIL command, which may be inaccurate or completely missing. You can
28815 follow the limit &'m'& in the configuration with K, M, or G to specify limits
28816 in kilobytes, megabytes, or gigabytes, respectively.
28817
28818 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
28819 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
28820 &%acl_smtp_mime%&, &%acl_smtp_data%&, or &%acl_smtp_rcpt%& ACLs. In
28821 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
28822 ACLs the rate is updated with the total recipient count in one go. Note that
28823 in either case the rate limiting engine will see a message with many
28824 recipients as a large high-speed burst.
28825
28826 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
28827 number of different recipients that the client has sent messages to in the
28828 last time period. That is, if the client repeatedly sends messages to the same
28829 recipient, its measured rate is not increased. This option can only be used in
28830 &%acl_smtp_rcpt%&.
28831
28832 The &%per_cmd%& option causes Exim to recompute the rate every time the
28833 condition is processed. This can be used to limit the rate of any SMTP
28834 command. If it is used in multiple ACLs it can limit the aggregate rate of
28835 multiple different commands.
28836
28837 The &%count=%& option can be used to alter how much Exim adds to the client's
28838 measured rate. For example, the &%per_byte%& option is equivalent to
28839 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
28840 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
28841 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
28842
28843 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
28844
28845
28846 .section "Ratelimit update modes" "ratoptupd"
28847 .cindex "rate limiting" "reading data without updating"
28848 You can specify one of three options with the &%ratelimit%& condition to
28849 control when its database is updated. This section describes the &%readonly%&
28850 mode, and the next section describes the &%strict%& and &%leaky%& modes.
28851
28852 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
28853 previously-computed rate to check against the limit.
28854
28855 For example, you can test the client's sending rate and deny it access (when
28856 it is too fast) in the connect ACL. If the client passes this check then it
28857 can go on to send a message, in which case its recorded rate will be updated
28858 in the MAIL ACL. Subsequent connections from the same client will check this
28859 new rate.
28860 .code
28861 acl_check_connect:
28862 deny ratelimit = 100 / 5m / readonly
28863 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
28864 (max $sender_rate_limit)
28865 # ...
28866 acl_check_mail:
28867 warn ratelimit = 100 / 5m / strict
28868 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
28869 (max $sender_rate_limit)
28870 .endd
28871
28872 If Exim encounters multiple &%ratelimit%& conditions with the same key when
28873 processing a message then it may increase the client's measured rate more than
28874 it should. For example, this will happen if you check the &%per_rcpt%& option
28875 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
28876 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
28877 multiple update problems by using the &%readonly%& option on later ratelimit
28878 checks.
28879
28880 The &%per_*%& options described above do not make sense in some ACLs. If you
28881 use a &%per_*%& option in an ACL where it is not normally permitted then the
28882 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
28883 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
28884 next section) so you must specify the &%readonly%& option explicitly.
28885
28886
28887 .section "Ratelimit options for handling fast clients" "ratoptfast"
28888 .cindex "rate limiting" "strict and leaky modes"
28889 If a client's average rate is greater than the maximum, the rate limiting
28890 engine can react in two possible ways, depending on the presence of the
28891 &%strict%& or &%leaky%& update modes. This is independent of the other
28892 counter-measures (such as rejecting the message) that may be specified by the
28893 rest of the ACL.
28894
28895 The &%leaky%& (default) option means that the client's recorded rate is not
28896 updated if it is above the limit. The effect of this is that Exim measures the
28897 client's average rate of successfully sent email, which cannot be greater than
28898 the maximum allowed. If the client is over the limit it may suffer some
28899 counter-measures (as specified in the ACL), but it will still be able to send
28900 email at the configured maximum rate, whatever the rate of its attempts. This
28901 is generally the better choice if you have clients that retry automatically.
28902 For example, it does not prevent a sender with an over-aggressive retry rate
28903 from getting any email through.
28904
28905 The &%strict%& option means that the client's recorded rate is always
28906 updated. The effect of this is that Exim measures the client's average rate
28907 of attempts to send email, which can be much higher than the maximum it is
28908 actually allowed. If the client is over the limit it may be subjected to
28909 counter-measures by the ACL. It must slow down and allow sufficient time to
28910 pass that its computed rate falls below the maximum before it can send email
28911 again. The time (the number of smoothing periods) it must wait and not
28912 attempt to send mail can be calculated with this formula:
28913 .code
28914 ln(peakrate/maxrate)
28915 .endd
28916
28917
28918 .section "Limiting the rate of different events" "ratoptuniq"
28919 .cindex "rate limiting" "counting unique events"
28920 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
28921 rate of different events. For example, the &%per_addr%& option uses this
28922 mechanism to count the number of different recipients that the client has
28923 sent messages to in the last time period; it is equivalent to
28924 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
28925 measure the rate that a client uses different sender addresses with the
28926 options &`per_mail/unique=$sender_address`&.
28927
28928 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
28929 has seen for that key. The whole set is thrown away when it is older than the
28930 rate smoothing period &'p'&, so each different event is counted at most once
28931 per period. In the &%leaky%& update mode, an event that causes the client to
28932 go over the limit is not added to the set, in the same way that the client's
28933 recorded rate is not updated in the same situation.
28934
28935 When you combine the &%unique=%& and &%readonly%& options, the specific
28936 &%unique=%& value is ignored, and Exim just retrieves the client's stored
28937 rate.
28938
28939 The &%unique=%& mechanism needs more space in the ratelimit database than the
28940 other &%ratelimit%& options in order to store the event set. The number of
28941 unique values is potentially as large as the rate limit, so the extra space
28942 required increases with larger limits.
28943
28944 The uniqueification is not perfect: there is a small probability that Exim
28945 will think a new event has happened before. If the sender's rate is less than
28946 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
28947 the measured rate can go above the limit, in which case Exim may under-count
28948 events by a significant margin. Fortunately, if the rate is high enough (2.7
28949 times the limit) that the false positive rate goes above 9%, then Exim will
28950 throw away the over-full event set before the measured rate falls below the
28951 limit. Therefore the only harm should be that exceptionally high sending rates
28952 are logged incorrectly; any countermeasures you configure will be as effective
28953 as intended.
28954
28955
28956 .section "Using rate limiting" "useratlim"
28957 Exim's other ACL facilities are used to define what counter-measures are taken
28958 when the rate limit is exceeded. This might be anything from logging a warning
28959 (for example, while measuring existing sending rates in order to define
28960 policy), through time delays to slow down fast senders, up to rejecting the
28961 message. For example:
28962 .code
28963 # Log all senders' rates
28964 warn ratelimit = 0 / 1h / strict
28965 log_message = Sender rate $sender_rate / $sender_rate_period
28966
28967 # Slow down fast senders; note the need to truncate $sender_rate
28968 # at the decimal point.
28969 warn ratelimit = 100 / 1h / per_rcpt / strict
28970 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
28971 $sender_rate_limit }s
28972
28973 # Keep authenticated users under control
28974 deny authenticated = *
28975 ratelimit = 100 / 1d / strict / $authenticated_id
28976
28977 # System-wide rate limit
28978 defer message = Sorry, too busy. Try again later.
28979 ratelimit = 10 / 1s / $primary_hostname
28980
28981 # Restrict incoming rate from each host, with a default
28982 # set using a macro and special cases looked up in a table.
28983 defer message = Sender rate exceeds $sender_rate_limit \
28984 messages per $sender_rate_period
28985 ratelimit = ${lookup {$sender_host_address} \
28986 cdb {DB/ratelimits.cdb} \
28987 {$value} {RATELIMIT} }
28988 .endd
28989 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
28990 especially with the &%per_rcpt%& option, you may suffer from a performance
28991 bottleneck caused by locking on the ratelimit hints database. Apart from
28992 making your ACLs less complicated, you can reduce the problem by using a
28993 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
28994 this means that Exim will lose its hints data after a reboot (including retry
28995 hints, the callout cache, and ratelimit data).
28996
28997
28998
28999 .section "Address verification" "SECTaddressverification"
29000 .cindex "verifying address" "options for"
29001 .cindex "policy control" "address verification"
29002 Several of the &%verify%& conditions described in section
29003 &<<SECTaclconditions>>& cause addresses to be verified. Section
29004 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
29005 The verification conditions can be followed by options that modify the
29006 verification process. The options are separated from the keyword and from each
29007 other by slashes, and some of them contain parameters. For example:
29008 .code
29009 verify = sender/callout
29010 verify = recipient/defer_ok/callout=10s,defer_ok
29011 .endd
29012 The first stage of address verification, which always happens, is to run the
29013 address through the routers, in &"verify mode"&. Routers can detect the
29014 difference between verification and routing for delivery, and their actions can
29015 be varied by a number of generic options such as &%verify%& and &%verify_only%&
29016 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
29017 The available options are as follows:
29018
29019 .ilist
29020 If the &%callout%& option is specified, successful routing to one or more
29021 remote hosts is followed by a &"callout"& to those hosts as an additional
29022 check. Callouts and their sub-options are discussed in the next section.
29023 .next
29024 If there is a defer error while doing verification routing, the ACL
29025 normally returns &"defer"&. However, if you include &%defer_ok%& in the
29026 options, the condition is forced to be true instead. Note that this is a main
29027 verification option as well as a suboption for callouts.
29028 .next
29029 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
29030 discusses the reporting of sender address verification failures.
29031 .next
29032 The &%success_on_redirect%& option causes verification always to succeed
29033 immediately after a successful redirection. By default, if a redirection
29034 generates just one address, that address is also verified. See further
29035 discussion in section &<<SECTredirwhilveri>>&.
29036 .endlist
29037
29038 .cindex "verifying address" "differentiating failures"
29039 .vindex "&$recipient_verify_failure$&"
29040 .vindex "&$sender_verify_failure$&"
29041 .vindex "&$acl_verify_message$&"
29042 After an address verification failure, &$acl_verify_message$& contains the
29043 error message that is associated with the failure. It can be preserved by
29044 coding like this:
29045 .code
29046 warn !verify = sender
29047 set acl_m0 = $acl_verify_message
29048 .endd
29049 If you are writing your own custom rejection message or log message when
29050 denying access, you can use this variable to include information about the
29051 verification failure.
29052
29053 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
29054 appropriate) contains one of the following words:
29055
29056 .ilist
29057 &%qualify%&: The address was unqualified (no domain), and the message
29058 was neither local nor came from an exempted host.
29059 .next
29060 &%route%&: Routing failed.
29061 .next
29062 &%mail%&: Routing succeeded, and a callout was attempted; rejection
29063 occurred at or before the MAIL command (that is, on initial
29064 connection, HELO, or MAIL).
29065 .next
29066 &%recipient%&: The RCPT command in a callout was rejected.
29067 .next
29068 &%postmaster%&: The postmaster check in a callout was rejected.
29069 .endlist
29070
29071 The main use of these variables is expected to be to distinguish between
29072 rejections of MAIL and rejections of RCPT in callouts.
29073
29074
29075
29076
29077 .section "Callout verification" "SECTcallver"
29078 .cindex "verifying address" "by callout"
29079 .cindex "callout" "verification"
29080 .cindex "SMTP" "callout verification"
29081 For non-local addresses, routing verifies the domain, but is unable to do any
29082 checking of the local part. There are situations where some means of verifying
29083 the local part is desirable. One way this can be done is to make an SMTP
29084 &'callback'& to a delivery host for the sender address or a &'callforward'& to
29085 a subsequent host for a recipient address, to see if the host accepts the
29086 address. We use the term &'callout'& to cover both cases. Note that for a
29087 sender address, the callback is not to the client host that is trying to
29088 deliver the message, but to one of the hosts that accepts incoming mail for the
29089 sender's domain.
29090
29091 Exim does not do callouts by default. If you want them to happen, you must
29092 request them by setting appropriate options on the &%verify%& condition, as
29093 described below. This facility should be used with care, because it can add a
29094 lot of resource usage to the cost of verifying an address. However, Exim does
29095 cache the results of callouts, which helps to reduce the cost. Details of
29096 caching are in section &<<SECTcallvercache>>&.
29097
29098 Recipient callouts are usually used only between hosts that are controlled by
29099 the same administration. For example, a corporate gateway host could use
29100 callouts to check for valid recipients on an internal mailserver. A successful
29101 callout does not guarantee that a real delivery to the address would succeed;
29102 on the other hand, a failing callout does guarantee that a delivery would fail.
29103
29104 If the &%callout%& option is present on a condition that verifies an address, a
29105 second stage of verification occurs if the address is successfully routed to
29106 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
29107 &(manualroute)& router, where the router specifies the hosts. However, if a
29108 router that does not set up hosts routes to an &(smtp)& transport with a
29109 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
29110 &%hosts_override%& set, its hosts are always used, whether or not the router
29111 supplies a host list.
29112 Callouts are only supported on &(smtp)& transports.
29113
29114 The port that is used is taken from the transport, if it is specified and is a
29115 remote transport. (For routers that do verification only, no transport need be
29116 specified.) Otherwise, the default SMTP port is used. If a remote transport
29117 specifies an outgoing interface, this is used; otherwise the interface is not
29118 specified. Likewise, the text that is used for the HELO command is taken from
29119 the transport's &%helo_data%& option; if there is no transport, the value of
29120 &$smtp_active_hostname$& is used.
29121
29122 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
29123 test whether a bounce message could be delivered to the sender address. The
29124 following SMTP commands are sent:
29125 .display
29126 &`HELO `&<&'local host name'&>
29127 &`MAIL FROM:<>`&
29128 &`RCPT TO:`&<&'the address to be tested'&>
29129 &`QUIT`&
29130 .endd
29131 LHLO is used instead of HELO if the transport's &%protocol%& option is
29132 set to &"lmtp"&.
29133
29134 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
29135 settings.
29136
29137 A recipient callout check is similar. By default, it also uses an empty address
29138 for the sender. This default is chosen because most hosts do not make use of
29139 the sender address when verifying a recipient. Using the same address means
29140 that a single cache entry can be used for each recipient. Some sites, however,
29141 do make use of the sender address when verifying. These are catered for by the
29142 &%use_sender%& and &%use_postmaster%& options, described in the next section.
29143
29144 If the response to the RCPT command is a 2&'xx'& code, the verification
29145 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
29146 Exim tries the next host, if any. If there is a problem with all the remote
29147 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
29148 &%callout%& option is given, in which case the condition is forced to succeed.
29149
29150 .cindex "SMTP" "output flushing, disabling for callout"
29151 A callout may take a little time. For this reason, Exim normally flushes SMTP
29152 output before performing a callout in an ACL, to avoid unexpected timeouts in
29153 clients when the SMTP PIPELINING extension is in use. The flushing can be
29154 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
29155
29156
29157
29158
29159 .section "Additional parameters for callouts" "CALLaddparcall"
29160 .cindex "callout" "additional parameters for"
29161 The &%callout%& option can be followed by an equals sign and a number of
29162 optional parameters, separated by commas. For example:
29163 .code
29164 verify = recipient/callout=10s,defer_ok
29165 .endd
29166 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
29167 separate verify options, is retained for backwards compatibility, but is now
29168 deprecated. The additional parameters for &%callout%& are as follows:
29169
29170
29171 .vlist
29172 .vitem <&'a&~time&~interval'&>
29173 .cindex "callout" "timeout, specifying"
29174 This specifies the timeout that applies for the callout attempt to each host.
29175 For example:
29176 .code
29177 verify = sender/callout=5s
29178 .endd
29179 The default is 30 seconds. The timeout is used for each response from the
29180 remote host. It is also used for the initial connection, unless overridden by
29181 the &%connect%& parameter.
29182
29183
29184 .vitem &*connect&~=&~*&<&'time&~interval'&>
29185 .cindex "callout" "connection timeout, specifying"
29186 This parameter makes it possible to set a different (usually smaller) timeout
29187 for making the SMTP connection. For example:
29188 .code
29189 verify = sender/callout=5s,connect=1s
29190 .endd
29191 If not specified, this timeout defaults to the general timeout value.
29192
29193 .vitem &*defer_ok*&
29194 .cindex "callout" "defer, action on"
29195 When this parameter is present, failure to contact any host, or any other kind
29196 of temporary error, is treated as success by the ACL. However, the cache is not
29197 updated in this circumstance.
29198
29199 .vitem &*fullpostmaster*&
29200 .cindex "callout" "full postmaster check"
29201 This operates like the &%postmaster%& option (see below), but if the check for
29202 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
29203 accordance with the specification in RFC 2821. The RFC states that the
29204 unqualified address &'postmaster'& should be accepted.
29205
29206
29207 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
29208 .cindex "callout" "sender when verifying header"
29209 When verifying addresses in header lines using the &%header_sender%&
29210 verification option, Exim behaves by default as if the addresses are envelope
29211 sender addresses from a message. Callout verification therefore tests to see
29212 whether a bounce message could be delivered, by using an empty address in the
29213 MAIL command. However, it is arguable that these addresses might never be used
29214 as envelope senders, and could therefore justifiably reject bounce messages
29215 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
29216 address to use in the MAIL command. For example:
29217 .code
29218 require verify = header_sender/callout=mailfrom=abcd@x.y.z
29219 .endd
29220 This parameter is available only for the &%header_sender%& verification option.
29221
29222
29223 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
29224 .cindex "callout" "overall timeout, specifying"
29225 This parameter sets an overall timeout for performing a callout verification.
29226 For example:
29227 .code
29228 verify = sender/callout=5s,maxwait=30s
29229 .endd
29230 This timeout defaults to four times the callout timeout for individual SMTP
29231 commands. The overall timeout applies when there is more than one host that can
29232 be tried. The timeout is checked before trying the next host. This prevents
29233 very long delays if there are a large number of hosts and all are timing out
29234 (for example, when network connections are timing out).
29235
29236
29237 .vitem &*no_cache*&
29238 .cindex "callout" "cache, suppressing"
29239 .cindex "caching callout, suppressing"
29240 When this parameter is given, the callout cache is neither read nor updated.
29241
29242 .vitem &*postmaster*&
29243 .cindex "callout" "postmaster; checking"
29244 When this parameter is set, a successful callout check is followed by a similar
29245 check for the local part &'postmaster'& at the same domain. If this address is
29246 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
29247 the postmaster check is recorded in a cache record; if it is a failure, this is
29248 used to fail subsequent callouts for the domain without a connection being
29249 made, until the cache record expires.
29250
29251 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
29252 The postmaster check uses an empty sender in the MAIL command by default.
29253 You can use this parameter to do a postmaster check using a different address.
29254 For example:
29255 .code
29256 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
29257 .endd
29258 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
29259 one overrides. The &%postmaster%& parameter is equivalent to this example:
29260 .code
29261 require verify = sender/callout=postmaster_mailfrom=
29262 .endd
29263 &*Warning*&: The caching arrangements for postmaster checking do not take
29264 account of the sender address. It is assumed that either the empty address or
29265 a fixed non-empty address will be used. All that Exim remembers is that the
29266 postmaster check for the domain succeeded or failed.
29267
29268
29269 .vitem &*random*&
29270 .cindex "callout" "&""random""& check"
29271 When this parameter is set, before doing the normal callout check, Exim does a
29272 check for a &"random"& local part at the same domain. The local part is not
29273 really random &-- it is defined by the expansion of the option
29274 &%callout_random_local_part%&, which defaults to
29275 .code
29276 $primary_hostname-$tod_epoch-testing
29277 .endd
29278 The idea here is to try to determine whether the remote host accepts all local
29279 parts without checking. If it does, there is no point in doing callouts for
29280 specific local parts. If the &"random"& check succeeds, the result is saved in
29281 a cache record, and used to force the current and subsequent callout checks to
29282 succeed without a connection being made, until the cache record expires.
29283
29284 .vitem &*use_postmaster*&
29285 .cindex "callout" "sender for recipient check"
29286 This parameter applies to recipient callouts only. For example:
29287 .code
29288 deny !verify = recipient/callout=use_postmaster
29289 .endd
29290 .vindex "&$qualify_domain$&"
29291 It causes a non-empty postmaster address to be used in the MAIL command when
29292 performing the callout for the recipient, and also for a &"random"& check if
29293 that is configured. The local part of the address is &`postmaster`& and the
29294 domain is the contents of &$qualify_domain$&.
29295
29296 .vitem &*use_sender*&
29297 This option applies to recipient callouts only. For example:
29298 .code
29299 require verify = recipient/callout=use_sender
29300 .endd
29301 It causes the message's actual sender address to be used in the MAIL
29302 command when performing the callout, instead of an empty address. There is no
29303 need to use this option unless you know that the called hosts make use of the
29304 sender when checking recipients. If used indiscriminately, it reduces the
29305 usefulness of callout caching.
29306 .endlist
29307
29308 If you use any of the parameters that set a non-empty sender for the MAIL
29309 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
29310 &%use_sender%&), you should think about possible loops. Recipient checking is
29311 usually done between two hosts that are under the same management, and the host
29312 that receives the callouts is not normally configured to do callouts itself.
29313 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
29314 these circumstances.
29315
29316 However, if you use a non-empty sender address for a callout to an arbitrary
29317 host, there is the likelihood that the remote host will itself initiate a
29318 callout check back to your host. As it is checking what appears to be a message
29319 sender, it is likely to use an empty address in MAIL, thus avoiding a
29320 callout loop. However, to be on the safe side it would be best to set up your
29321 own ACLs so that they do not do sender verification checks when the recipient
29322 is the address you use for header sender or postmaster callout checking.
29323
29324 Another issue to think about when using non-empty senders for callouts is
29325 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
29326 by the sender/recipient combination; thus, for any given recipient, many more
29327 actual callouts are performed than when an empty sender or postmaster is used.
29328
29329
29330
29331
29332 .section "Callout caching" "SECTcallvercache"
29333 .cindex "hints database" "callout cache"
29334 .cindex "callout" "cache, description of"
29335 .cindex "caching" "callout"
29336 Exim caches the results of callouts in order to reduce the amount of resources
29337 used, unless you specify the &%no_cache%& parameter with the &%callout%&
29338 option. A hints database called &"callout"& is used for the cache. Two
29339 different record types are used: one records the result of a callout check for
29340 a specific address, and the other records information that applies to the
29341 entire domain (for example, that it accepts the local part &'postmaster'&).
29342
29343 When an original callout fails, a detailed SMTP error message is given about
29344 the failure. However, for subsequent failures use the cache data, this message
29345 is not available.
29346
29347 The expiry times for negative and positive address cache records are
29348 independent, and can be set by the global options &%callout_negative_expire%&
29349 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
29350
29351 If a host gives a negative response to an SMTP connection, or rejects any
29352 commands up to and including
29353 .code
29354 MAIL FROM:<>
29355 .endd
29356 (but not including the MAIL command with a non-empty address),
29357 any callout attempt is bound to fail. Exim remembers such failures in a
29358 domain cache record, which it uses to fail callouts for the domain without
29359 making new connections, until the domain record times out. There are two
29360 separate expiry times for domain cache records:
29361 &%callout_domain_negative_expire%& (default 3h) and
29362 &%callout_domain_positive_expire%& (default 7d).
29363
29364 Domain records expire when the negative expiry time is reached if callouts
29365 cannot be made for the domain, or if the postmaster check failed.
29366 Otherwise, they expire when the positive expiry time is reached. This
29367 ensures that, for example, a host that stops accepting &"random"& local parts
29368 will eventually be noticed.
29369
29370 The callout caching mechanism is based on the domain of the address that is
29371 being tested. If the domain routes to several hosts, it is assumed that their
29372 behaviour will be the same.
29373
29374
29375
29376 .section "Sender address verification reporting" "SECTsenaddver"
29377 .cindex "verifying" "suppressing error details"
29378 See section &<<SECTaddressverification>>& for a general discussion of
29379 verification. When sender verification fails in an ACL, the details of the
29380 failure are given as additional output lines before the 550 response to the
29381 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
29382 you might see:
29383 .code
29384 MAIL FROM:<xyz@abc.example>
29385 250 OK
29386 RCPT TO:<pqr@def.example>
29387 550-Verification failed for <xyz@abc.example>
29388 550-Called: 192.168.34.43
29389 550-Sent: RCPT TO:<xyz@abc.example>
29390 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
29391 550 Sender verification failed
29392 .endd
29393 If more than one RCPT command fails in the same way, the details are given
29394 only for the first of them. However, some administrators do not want to send
29395 out this much information. You can suppress the details by adding
29396 &`/no_details`& to the ACL statement that requests sender verification. For
29397 example:
29398 .code
29399 verify = sender/no_details
29400 .endd
29401
29402 .section "Redirection while verifying" "SECTredirwhilveri"
29403 .cindex "verifying" "redirection while"
29404 .cindex "address redirection" "while verifying"
29405 A dilemma arises when a local address is redirected by aliasing or forwarding
29406 during verification: should the generated addresses themselves be verified,
29407 or should the successful expansion of the original address be enough to verify
29408 it? By default, Exim takes the following pragmatic approach:
29409
29410 .ilist
29411 When an incoming address is redirected to just one child address, verification
29412 continues with the child address, and if that fails to verify, the original
29413 verification also fails.
29414 .next
29415 When an incoming address is redirected to more than one child address,
29416 verification does not continue. A success result is returned.
29417 .endlist
29418
29419 This seems the most reasonable behaviour for the common use of aliasing as a
29420 way of redirecting different local parts to the same mailbox. It means, for
29421 example, that a pair of alias entries of the form
29422 .code
29423 A.Wol: aw123
29424 aw123: :fail: Gone away, no forwarding address
29425 .endd
29426 work as expected, with both local parts causing verification failure. When a
29427 redirection generates more than one address, the behaviour is more like a
29428 mailing list, where the existence of the alias itself is sufficient for
29429 verification to succeed.
29430
29431 It is possible, however, to change the default behaviour so that all successful
29432 redirections count as successful verifications, however many new addresses are
29433 generated. This is specified by the &%success_on_redirect%& verification
29434 option. For example:
29435 .code
29436 require verify = recipient/success_on_redirect/callout=10s
29437 .endd
29438 In this example, verification succeeds if a router generates a new address, and
29439 the callout does not occur, because no address was routed to a remote host.
29440
29441 When verification is being tested via the &%-bv%& option, the treatment of
29442 redirections is as just described, unless the &%-v%& or any debugging option is
29443 also specified. In that case, full verification is done for every generated
29444 address and a report is output for each of them.
29445
29446
29447
29448 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
29449 .cindex "CSA" "verifying"
29450 Client SMTP Authorization is a system that allows a site to advertise
29451 which machines are and are not permitted to send email. This is done by placing
29452 special SRV records in the DNS; these are looked up using the client's HELO
29453 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
29454 Authorization checks in Exim are performed by the ACL condition:
29455 .code
29456 verify = csa
29457 .endd
29458 This fails if the client is not authorized. If there is a DNS problem, or if no
29459 valid CSA SRV record is found, or if the client is authorized, the condition
29460 succeeds. These three cases can be distinguished using the expansion variable
29461 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
29462 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
29463 be likely to cause problems for legitimate email.
29464
29465 The error messages produced by the CSA code include slightly more
29466 detail. If &$csa_status$& is &"defer"&, this may be because of problems
29467 looking up the CSA SRV record, or problems looking up the CSA target
29468 address record. There are four reasons for &$csa_status$& being &"fail"&:
29469
29470 .ilist
29471 The client's host name is explicitly not authorized.
29472 .next
29473 The client's IP address does not match any of the CSA target IP addresses.
29474 .next
29475 The client's host name is authorized but it has no valid target IP addresses
29476 (for example, the target's addresses are IPv6 and the client is using IPv4).
29477 .next
29478 The client's host name has no CSA SRV record but a parent domain has asserted
29479 that all subdomains must be explicitly authorized.
29480 .endlist
29481
29482 The &%csa%& verification condition can take an argument which is the domain to
29483 use for the DNS query. The default is:
29484 .code
29485 verify = csa/$sender_helo_name
29486 .endd
29487 This implementation includes an extension to CSA. If the query domain
29488 is an address literal such as [192.0.2.95], or if it is a bare IP
29489 address, Exim searches for CSA SRV records in the reverse DNS as if
29490 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
29491 meaningful to say:
29492 .code
29493 verify = csa/$sender_host_address
29494 .endd
29495 In fact, this is the check that Exim performs if the client does not say HELO.
29496 This extension can be turned off by setting the main configuration option
29497 &%dns_csa_use_reverse%& to be false.
29498
29499 If a CSA SRV record is not found for the domain itself, a search
29500 is performed through its parent domains for a record which might be
29501 making assertions about subdomains. The maximum depth of this search is limited
29502 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
29503 default. Exim does not look for CSA SRV records in a top level domain, so the
29504 default settings handle HELO domains as long as seven
29505 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
29506 of legitimate HELO domains.
29507
29508 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
29509 direct SRV lookups, this is not sufficient because of the extra parent domain
29510 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
29511 addresses into lookups in the reverse DNS space. The result of a successful
29512 lookup such as:
29513 .code
29514 ${lookup dnsdb {csa=$sender_helo_name}}
29515 .endd
29516 has two space-separated fields: an authorization code and a target host name.
29517 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
29518 authorization required but absent, or &"?"& for unknown.
29519
29520
29521
29522
29523 .section "Bounce address tag validation" "SECTverifyPRVS"
29524 .cindex "BATV, verifying"
29525 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
29526 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
29527 Genuine incoming bounce messages should therefore always be addressed to
29528 recipients that have a valid tag. This scheme is a way of detecting unwanted
29529 bounce messages caused by sender address forgeries (often called &"collateral
29530 spam"&), because the recipients of such messages do not include valid tags.
29531
29532 There are two expansion items to help with the implementation of the BATV
29533 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
29534 the original envelope sender address by using a simple key to add a hash of the
29535 address and some time-based randomizing information. The &%prvs%& expansion
29536 item creates a signed address, and the &%prvscheck%& expansion item checks one.
29537 The syntax of these expansion items is described in section
29538 &<<SECTexpansionitems>>&.
29539
29540 As an example, suppose the secret per-address keys are stored in an MySQL
29541 database. A query to look up the key for an address could be defined as a macro
29542 like this:
29543 .code
29544 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
29545 WHERE sender='${quote_mysql:$prvscheck_address}'\
29546 }{$value}}
29547 .endd
29548 Suppose also that the senders who make use of BATV are defined by an address
29549 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
29550 use this:
29551 .code
29552 # Bounces: drop unsigned addresses for BATV senders
29553 deny message = This address does not send an unsigned reverse path
29554 senders = :
29555 recipients = +batv_senders
29556
29557 # Bounces: In case of prvs-signed address, check signature.
29558 deny message = Invalid reverse path signature.
29559 senders = :
29560 condition = ${prvscheck {$local_part@$domain}\
29561 {PRVSCHECK_SQL}{1}}
29562 !condition = $prvscheck_result
29563 .endd
29564 The first statement rejects recipients for bounce messages that are addressed
29565 to plain BATV sender addresses, because it is known that BATV senders do not
29566 send out messages with plain sender addresses. The second statement rejects
29567 recipients that are prvs-signed, but with invalid signatures (either because
29568 the key is wrong, or the signature has timed out).
29569
29570 A non-prvs-signed address is not rejected by the second statement, because the
29571 &%prvscheck%& expansion yields an empty string if its first argument is not a
29572 prvs-signed address, thus causing the &%condition%& condition to be false. If
29573 the first argument is a syntactically valid prvs-signed address, the yield is
29574 the third string (in this case &"1"&), whether or not the cryptographic and
29575 timeout checks succeed. The &$prvscheck_result$& variable contains the result
29576 of the checks (empty for failure, &"1"& for success).
29577
29578 There is one more issue you must consider when implementing prvs-signing:
29579 you have to ensure that the routers accept prvs-signed addresses and
29580 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
29581 router to remove the signature with a configuration along these lines:
29582 .code
29583 batv_redirect:
29584 driver = redirect
29585 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
29586 .endd
29587 This works because, if the third argument of &%prvscheck%& is empty, the result
29588 of the expansion of a prvs-signed address is the decoded value of the original
29589 address. This router should probably be the first of your routers that handles
29590 local addresses.
29591
29592 To create BATV-signed addresses in the first place, a transport of this form
29593 can be used:
29594 .code
29595 external_smtp_batv:
29596 driver = smtp
29597 return_path = ${prvs {$return_path} \
29598 {${lookup mysql{SELECT \
29599 secret FROM batv_prvs WHERE \
29600 sender='${quote_mysql:$sender_address}'} \
29601 {$value}fail}}}
29602 .endd
29603 If no key can be found for the existing return path, no signing takes place.
29604
29605
29606
29607 .section "Using an ACL to control relaying" "SECTrelaycontrol"
29608 .cindex "&ACL;" "relay control"
29609 .cindex "relaying" "control by ACL"
29610 .cindex "policy control" "relay control"
29611 An MTA is said to &'relay'& a message if it receives it from some host and
29612 delivers it directly to another host as a result of a remote address contained
29613 within it. Redirecting a local address via an alias or forward file and then
29614 passing the message on to another host is not relaying,
29615 .cindex "&""percent hack""&"
29616 but a redirection as a result of the &"percent hack"& is.
29617
29618 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
29619 A host which is acting as a gateway or an MX backup is concerned with incoming
29620 relaying from arbitrary hosts to a specific set of domains. On the other hand,
29621 a host which is acting as a smart host for a number of clients is concerned
29622 with outgoing relaying from those clients to the Internet at large. Often the
29623 same host is fulfilling both functions,
29624 . ///
29625 . as illustrated in the diagram below,
29626 . ///
29627 but in principle these two kinds of relaying are entirely independent. What is
29628 not wanted is the transmission of mail from arbitrary remote hosts through your
29629 system to arbitrary domains.
29630
29631
29632 You can implement relay control by means of suitable statements in the ACL that
29633 runs for each RCPT command. For convenience, it is often easiest to use
29634 Exim's named list facility to define the domains and hosts involved. For
29635 example, suppose you want to do the following:
29636
29637 .ilist
29638 Deliver a number of domains to mailboxes on the local host (or process them
29639 locally in some other way). Let's say these are &'my.dom1.example'& and
29640 &'my.dom2.example'&.
29641 .next
29642 Relay mail for a number of other domains for which you are the secondary MX.
29643 These might be &'friend1.example'& and &'friend2.example'&.
29644 .next
29645 Relay mail from the hosts on your local LAN, to whatever domains are involved.
29646 Suppose your LAN is 192.168.45.0/24.
29647 .endlist
29648
29649
29650 In the main part of the configuration, you put the following definitions:
29651 .code
29652 domainlist local_domains = my.dom1.example : my.dom2.example
29653 domainlist relay_to_domains = friend1.example : friend2.example
29654 hostlist relay_from_hosts = 192.168.45.0/24
29655 .endd
29656 Now you can use these definitions in the ACL that is run for every RCPT
29657 command:
29658 .code
29659 acl_check_rcpt:
29660 accept domains = +local_domains : +relay_to_domains
29661 accept hosts = +relay_from_hosts
29662 .endd
29663 The first statement accepts any RCPT command that contains an address in
29664 the local or relay domains. For any other domain, control passes to the second
29665 statement, which accepts the command only if it comes from one of the relay
29666 hosts. In practice, you will probably want to make your ACL more sophisticated
29667 than this, for example, by including sender and recipient verification. The
29668 default configuration includes a more comprehensive example, which is described
29669 in chapter &<<CHAPdefconfil>>&.
29670
29671
29672
29673 .section "Checking a relay configuration" "SECTcheralcon"
29674 .cindex "relaying" "checking control of"
29675 You can check the relay characteristics of your configuration in the same way
29676 that you can test any ACL behaviour for an incoming SMTP connection, by using
29677 the &%-bh%& option to run a fake SMTP session with which you interact.
29678
29679 For specifically testing for unwanted relaying, the host
29680 &'relay-test.mail-abuse.org'& provides a useful service. If you telnet to this
29681 host from the host on which Exim is running, using the normal telnet port, you
29682 will see a normal telnet connection message and then quite a long delay. Be
29683 patient. The remote host is making an SMTP connection back to your host, and
29684 trying a number of common probes to test for open relay vulnerability. The
29685 results of the tests will eventually appear on your terminal.
29686 .ecindex IIDacl
29687
29688
29689
29690 . ////////////////////////////////////////////////////////////////////////////
29691 . ////////////////////////////////////////////////////////////////////////////
29692
29693 .chapter "Content scanning at ACL time" "CHAPexiscan"
29694 .scindex IIDcosca "content scanning" "at ACL time"
29695 The extension of Exim to include content scanning at ACL time, formerly known
29696 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
29697 was integrated into the main source for Exim release 4.50, and Tom continues to
29698 maintain it. Most of the wording of this chapter is taken from Tom's
29699 specification.
29700
29701 It is also possible to scan the content of messages at other times. The
29702 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
29703 scanning after all the ACLs have run. A transport filter can be used to scan
29704 messages at delivery time (see the &%transport_filter%& option, described in
29705 chapter &<<CHAPtransportgeneric>>&).
29706
29707 If you want to include the ACL-time content-scanning features when you compile
29708 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
29709 &_Local/Makefile_&. When you do that, the Exim binary is built with:
29710
29711 .ilist
29712 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
29713 for all MIME parts for SMTP and non-SMTP messages, respectively.
29714 .next
29715 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
29716 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
29717 run at the end of message reception (the &%acl_smtp_data%& ACL).
29718 .next
29719 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
29720 of messages, or parts of messages, for debugging purposes.
29721 .next
29722 Additional expansion variables that are set in the new ACL and by the new
29723 conditions.
29724 .next
29725 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
29726 .endlist
29727
29728 There is another content-scanning configuration option for &_Local/Makefile_&,
29729 called WITH_OLD_DEMIME. If this is set, the old, deprecated &%demime%& ACL
29730 condition is compiled, in addition to all the other content-scanning features.
29731
29732 Content-scanning is continually evolving, and new features are still being
29733 added. While such features are still unstable and liable to incompatible
29734 changes, they are made available in Exim by setting options whose names begin
29735 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
29736 this manual. You can find out about them by reading the file called
29737 &_doc/experimental.txt_&.
29738
29739 All the content-scanning facilities work on a MBOX copy of the message that is
29740 temporarily created in a file called:
29741 .display
29742 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
29743 .endd
29744 The &_.eml_& extension is a friendly hint to virus scanners that they can
29745 expect an MBOX-like structure inside that file. The file is created when the
29746 first content scanning facility is called. Subsequent calls to content
29747 scanning conditions open the same file again. The directory is recursively
29748 removed when the &%acl_smtp_data%& ACL has finished running, unless
29749 .code
29750 control = no_mbox_unspool
29751 .endd
29752 has been encountered. When the MIME ACL decodes files, they are put into the
29753 same directory by default.
29754
29755
29756
29757 .section "Scanning for viruses" "SECTscanvirus"
29758 .cindex "virus scanning"
29759 .cindex "content scanning" "for viruses"
29760 .cindex "content scanning" "the &%malware%& condition"
29761 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
29762 It supports a &"generic"& interface to scanners called via the shell, and
29763 specialized interfaces for &"daemon"& type virus scanners, which are resident
29764 in memory and thus are much faster.
29765
29766
29767 .oindex "&%av_scanner%&"
29768 You can set the &%av_scanner%& option in first part of the Exim configuration
29769 file to specify which scanner to use, together with any additional options that
29770 are needed. The basic syntax is as follows:
29771 .display
29772 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
29773 .endd
29774 If you do not set &%av_scanner%&, it defaults to
29775 .code
29776 av_scanner = sophie:/var/run/sophie
29777 .endd
29778 If the value of &%av_scanner%& starts with a dollar character, it is expanded
29779 before use.
29780 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
29781 The following scanner types are supported in this release:
29782
29783 .vlist
29784 .vitem &%aveserver%&
29785 .cindex "virus scanners" "Kaspersky"
29786 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
29787 at &url(http://www.kaspersky.com). This scanner type takes one option,
29788 which is the path to the daemon's UNIX socket. The default is shown in this
29789 example:
29790 .code
29791 av_scanner = aveserver:/var/run/aveserver
29792 .endd
29793
29794
29795 .vitem &%clamd%&
29796 .cindex "virus scanners" "clamd"
29797 This daemon-type scanner is GPL and free. You can get it at
29798 &url(http://www.clamav.net/). Some older versions of clamd do not seem to
29799 unpack MIME containers, so it used to be recommended to unpack MIME attachments
29800 in the MIME ACL. This no longer believed to be necessary. One option is
29801 required: either the path and name of a UNIX socket file, or a hostname or IP
29802 number, and a port, separated by space, as in the second of these examples:
29803 .code
29804 av_scanner = clamd:/opt/clamd/socket
29805 av_scanner = clamd:192.0.2.3 1234
29806 av_scanner = clamd:192.0.2.3 1234:local
29807 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
29808 .endd
29809 If the value of av_scanner points to a UNIX socket file or contains the local
29810 keyword, then the ClamAV interface will pass a filename containing the data
29811 to be scanned, which will should normally result in less I/O happening and be
29812 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
29813 Exim does not assume that there is a common filesystem with the remote host.
29814 There is an option WITH_OLD_CLAMAV_STREAM in &_src/EDITME_& available, should
29815 you be running a version of ClamAV prior to 0.95.
29816
29817 The final example shows that multiple TCP targets can be specified. Exim will
29818 randomly use one for each incoming email (i.e. it load balances them). Note
29819 that only TCP targets may be used if specifying a list of scanners; a UNIX
29820 socket cannot be mixed in with TCP targets. If one of the servers becomes
29821 unavailable, Exim will try the remaining one(s) until it finds one that works.
29822 When a clamd server becomes unreachable, Exim will log a message. Exim does
29823 not keep track of scanner state between multiple messages, and the scanner
29824 selection is random, so the message will get logged in the mainlog for each
29825 email that the down scanner gets chosen first (message wrapped to be readable):
29826 .code
29827 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
29828 clamd: connection to localhost, port 3310 failed
29829 (Connection refused)
29830 .endd
29831
29832 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
29833 contributing the code for this scanner.
29834
29835 .vitem &%cmdline%&
29836 .cindex "virus scanners" "command line interface"
29837 This is the keyword for the generic command line scanner interface. It can be
29838 used to attach virus scanners that are invoked from the shell. This scanner
29839 type takes 3 mandatory options:
29840
29841 .olist
29842 The full path and name of the scanner binary, with all command line options,
29843 and a placeholder (&`%s`&) for the directory to scan.
29844
29845 .next
29846 A regular expression to match against the STDOUT and STDERR output of the
29847 virus scanner. If the expression matches, a virus was found. You must make
29848 absolutely sure that this expression matches on &"virus found"&. This is called
29849 the &"trigger"& expression.
29850
29851 .next
29852 Another regular expression, containing exactly one pair of parentheses, to
29853 match the name of the virus found in the scanners output. This is called the
29854 &"name"& expression.
29855 .endlist olist
29856
29857 For example, Sophos Sweep reports a virus on a line like this:
29858 .code
29859 Virus 'W32/Magistr-B' found in file ./those.bat
29860 .endd
29861 For the trigger expression, we can match the phrase &"found in file"&. For the
29862 name expression, we want to extract the W32/Magistr-B string, so we can match
29863 for the single quotes left and right of it. Altogether, this makes the
29864 configuration setting:
29865 .code
29866 av_scanner = cmdline:\
29867 /path/to/sweep -ss -all -rec -archive %s:\
29868 found in file:'(.+)'
29869 .endd
29870 .vitem &%drweb%&
29871 .cindex "virus scanners" "DrWeb"
29872 The DrWeb daemon scanner (&url(http://www.sald.com/)) interface takes one
29873 argument, either a full path to a UNIX socket, or an IP address and port
29874 separated by white space, as in these examples:
29875 .code
29876 av_scanner = drweb:/var/run/drwebd.sock
29877 av_scanner = drweb:192.168.2.20 31337
29878 .endd
29879 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
29880 is used. Thanks to Alex Miller for contributing the code for this scanner.
29881
29882 .vitem &%fsecure%&
29883 .cindex "virus scanners" "F-Secure"
29884 The F-Secure daemon scanner (&url(http://www.f-secure.com)) takes one
29885 argument which is the path to a UNIX socket. For example:
29886 .code
29887 av_scanner = fsecure:/path/to/.fsav
29888 .endd
29889 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
29890 Thelmen for contributing the code for this scanner.
29891
29892 .vitem &%kavdaemon%&
29893 .cindex "virus scanners" "Kaspersky"
29894 This is the scanner daemon of Kaspersky Version 4. This version of the
29895 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
29896 scanner type takes one option, which is the path to the daemon's UNIX socket.
29897 For example:
29898 .code
29899 av_scanner = kavdaemon:/opt/AVP/AvpCtl
29900 .endd
29901 The default path is &_/var/run/AvpCtl_&.
29902
29903 .vitem &%mksd%&
29904 .cindex "virus scanners" "mksd"
29905 This is a daemon type scanner that is aimed mainly at Polish users, though some
29906 parts of documentation are now available in English. You can get it at
29907 &url(http://linux.mks.com.pl/). The only option for this scanner type is
29908 the maximum number of processes used simultaneously to scan the attachments,
29909 provided that the demime facility is employed and also provided that mksd has
29910 been run with at least the same number of child processes. For example:
29911 .code
29912 av_scanner = mksd:2
29913 .endd
29914 You can safely omit this option (the default value is 1).
29915
29916 .vitem &%sock%&
29917 .cindex "virus scanners" "simple socket-connected"
29918 This is a general-purpose way of talking to simple scanner daemons
29919 running on the local machine.
29920 There are four options:
29921 an address (which may be an IP addres and port, or the path of a Unix socket),
29922 a commandline to send (may include a single %s which will be replaced with
29923 the path to the mail file to be scanned),
29924 an RE to trigger on from the returned data,
29925 an RE to extract malware_name from the returned data.
29926 For example:
29927 .code
29928 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)\$
29929 .endd
29930 Default for the socket specifier is &_/tmp/malware.sock_&.
29931 Default for the commandline is &_%s\n_&.
29932 Both regular-expressions are required.
29933
29934 .vitem &%sophie%&
29935 .cindex "virus scanners" "Sophos and Sophie"
29936 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
29937 You can get Sophie at &url(http://www.clanfield.info/sophie/). The only option
29938 for this scanner type is the path to the UNIX socket that Sophie uses for
29939 client communication. For example:
29940 .code
29941 av_scanner = sophie:/tmp/sophie
29942 .endd
29943 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
29944 the option.
29945 .endlist
29946
29947 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
29948 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
29949 ACL.
29950
29951 The &%av_scanner%& option is expanded each time &%malware%& is called. This
29952 makes it possible to use different scanners. See further below for an example.
29953 The &%malware%& condition caches its results, so when you use it multiple times
29954 for the same message, the actual scanning process is only carried out once.
29955 However, using expandable items in &%av_scanner%& disables this caching, in
29956 which case each use of the &%malware%& condition causes a new scan of the
29957 message.
29958
29959 The &%malware%& condition takes a right-hand argument that is expanded before
29960 use. It can then be one of
29961
29962 .ilist
29963 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
29964 The condition succeeds if a virus was found, and fail otherwise. This is the
29965 recommended usage.
29966 .next
29967 &"false"& or &"0"& or an empty string, in which case no scanning is done and
29968 the condition fails immediately.
29969 .next
29970 A regular expression, in which case the message is scanned for viruses. The
29971 condition succeeds if a virus is found and its name matches the regular
29972 expression. This allows you to take special actions on certain types of virus.
29973 .endlist
29974
29975 You can append &`/defer_ok`& to the &%malware%& condition to accept messages
29976 even if there is a problem with the virus scanner. Otherwise, such a problem
29977 causes the ACL to defer.
29978
29979 .vindex "&$malware_name$&"
29980 When a virus is found, the condition sets up an expansion variable called
29981 &$malware_name$& that contains the name of the virus. You can use it in a
29982 &%message%& modifier that specifies the error returned to the sender, and/or in
29983 logging data.
29984
29985 If your virus scanner cannot unpack MIME and TNEF containers itself, you should
29986 use the &%demime%& condition (see section &<<SECTdemimecond>>&) before the
29987 &%malware%& condition.
29988
29989 Beware the interaction of Exim's &%message_size_limit%& with any size limits
29990 imposed by your anti-virus scanner.
29991
29992 Here is a very simple scanning example:
29993 .code
29994 deny message = This message contains malware ($malware_name)
29995 demime = *
29996 malware = *
29997 .endd
29998 The next example accepts messages when there is a problem with the scanner:
29999 .code
30000 deny message = This message contains malware ($malware_name)
30001 demime = *
30002 malware = */defer_ok
30003 .endd
30004 The next example shows how to use an ACL variable to scan with both sophie and
30005 aveserver. It assumes you have set:
30006 .code
30007 av_scanner = $acl_m0
30008 .endd
30009 in the main Exim configuration.
30010 .code
30011 deny message = This message contains malware ($malware_name)
30012 set acl_m0 = sophie
30013 malware = *
30014
30015 deny message = This message contains malware ($malware_name)
30016 set acl_m0 = aveserver
30017 malware = *
30018 .endd
30019
30020
30021 .section "Scanning with SpamAssassin" "SECTscanspamass"
30022 .cindex "content scanning" "for spam"
30023 .cindex "spam scanning"
30024 .cindex "SpamAssassin"
30025 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
30026 score and a report for the message. You can get SpamAssassin at
30027 &url(http://www.spamassassin.org), or, if you have a working Perl
30028 installation, you can use CPAN by running:
30029 .code
30030 perl -MCPAN -e 'install Mail::SpamAssassin'
30031 .endd
30032 SpamAssassin has its own set of configuration files. Please review its
30033 documentation to see how you can tweak it. The default installation should work
30034 nicely, however.
30035
30036 .oindex "&%spamd_address%&"
30037 After having installed and configured SpamAssassin, start the &%spamd%& daemon.
30038 By default, it listens on 127.0.0.1, TCP port 783. If you use another host or
30039 port for &%spamd%&, you must set the &%spamd_address%& option in the global
30040 part of the Exim configuration as follows (example):
30041 .code
30042 spamd_address = 192.168.99.45 387
30043 .endd
30044 You do not need to set this option if you use the default. As of version 2.60,
30045 &%spamd%& also supports communication over UNIX sockets. If you want to use
30046 these, supply &%spamd_address%& with an absolute file name instead of a
30047 address/port pair:
30048 .code
30049 spamd_address = /var/run/spamd_socket
30050 .endd
30051 You can have multiple &%spamd%& servers to improve scalability. These can
30052 reside on other hardware reachable over the network. To specify multiple
30053 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
30054 option, separated with colons:
30055 .code
30056 spamd_address = 192.168.2.10 783 : \
30057 192.168.2.11 783 : \
30058 192.168.2.12 783
30059 .endd
30060 Up to 32 &%spamd%& servers are supported. The servers are queried in a random
30061 fashion. When a server fails to respond to the connection attempt, all other
30062 servers are tried until one succeeds. If no server responds, the &%spam%&
30063 condition defers.
30064
30065 &*Warning*&: It is not possible to use the UNIX socket connection method with
30066 multiple &%spamd%& servers.
30067
30068 The &%spamd_address%& variable is expanded before use if it starts with
30069 a dollar sign. In this case, the expansion may return a string that is
30070 used as the list so that multiple spamd servers can be the result of an
30071 expansion.
30072
30073 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
30074 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
30075 .code
30076 deny message = This message was classified as SPAM
30077 spam = joe
30078 .endd
30079 The right-hand side of the &%spam%& condition specifies a name. This is
30080 relevant if you have set up multiple SpamAssassin profiles. If you do not want
30081 to scan using a specific profile, but rather use the SpamAssassin system-wide
30082 default profile, you can scan for an unknown name, or simply use &"nobody"&.
30083 However, you must put something on the right-hand side.
30084
30085 The name allows you to use per-domain or per-user antispam profiles in
30086 principle, but this is not straightforward in practice, because a message may
30087 have multiple recipients, not necessarily all in the same domain. Because the
30088 &%spam%& condition has to be called from a DATA ACL in order to be able to
30089 read the contents of the message, the variables &$local_part$& and &$domain$&
30090 are not set.
30091
30092 The right-hand side of the &%spam%& condition is expanded before being used, so
30093 you can put lookups or conditions there. When the right-hand side evaluates to
30094 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
30095
30096
30097 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
30098 large ones may cause significant performance degradation. As most spam messages
30099 are quite small, it is recommended that you do not scan the big ones. For
30100 example:
30101 .code
30102 deny message = This message was classified as SPAM
30103 condition = ${if < {$message_size}{10K}}
30104 spam = nobody
30105 .endd
30106
30107 The &%spam%& condition returns true if the threshold specified in the user's
30108 SpamAssassin profile has been matched or exceeded. If you want to use the
30109 &%spam%& condition for its side effects (see the variables below), you can make
30110 it always return &"true"& by appending &`:true`& to the username.
30111
30112 .cindex "spam scanning" "returned variables"
30113 When the &%spam%& condition is run, it sets up a number of expansion
30114 variables. These variables are saved with the received message, thus they are
30115 available for use at delivery time.
30116
30117 .vlist
30118 .vitem &$spam_score$&
30119 The spam score of the message, for example &"3.4"& or &"30.5"&. This is useful
30120 for inclusion in log or reject messages.
30121
30122 .vitem &$spam_score_int$&
30123 The spam score of the message, multiplied by ten, as an integer value. For
30124 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
30125 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
30126 The integer value is useful for numeric comparisons in conditions.
30127
30128 .vitem &$spam_bar$&
30129 A string consisting of a number of &"+"& or &"-"& characters, representing the
30130 integer part of the spam score value. A spam score of 4.4 would have a
30131 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
30132 headers, since MUAs can match on such strings.
30133
30134 .vitem &$spam_report$&
30135 A multiline text table, containing the full SpamAssassin report for the
30136 message. Useful for inclusion in headers or reject messages.
30137 .endlist
30138
30139 The &%spam%& condition caches its results unless expansion in
30140 spamd_address was used. If you call it again with the same user name, it
30141 does not scan again, but rather returns the same values as before.
30142
30143 The &%spam%& condition returns DEFER if there is any error while running
30144 the message through SpamAssassin or if the expansion of spamd_address
30145 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
30146 statement block), append &`/defer_ok`& to the right-hand side of the
30147 spam condition, like this:
30148 .code
30149 deny message = This message was classified as SPAM
30150 spam = joe/defer_ok
30151 .endd
30152 This causes messages to be accepted even if there is a problem with &%spamd%&.
30153
30154 Here is a longer, commented example of the use of the &%spam%&
30155 condition:
30156 .code
30157 # put headers in all messages (no matter if spam or not)
30158 warn spam = nobody:true
30159 add_header = X-Spam-Score: $spam_score ($spam_bar)
30160 add_header = X-Spam-Report: $spam_report
30161
30162 # add second subject line with *SPAM* marker when message
30163 # is over threshold
30164 warn spam = nobody
30165 add_header = Subject: *SPAM* $h_Subject:
30166
30167 # reject spam at high scores (> 12)
30168 deny message = This message scored $spam_score spam points.
30169 spam = nobody:true
30170 condition = ${if >{$spam_score_int}{120}{1}{0}}
30171 .endd
30172
30173
30174
30175 .section "Scanning MIME parts" "SECTscanmimepart"
30176 .cindex "content scanning" "MIME parts"
30177 .cindex "MIME content scanning"
30178 .oindex "&%acl_smtp_mime%&"
30179 .oindex "&%acl_not_smtp_mime%&"
30180 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
30181 each MIME part of an SMTP message, including multipart types, in the sequence
30182 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
30183 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
30184 options may both refer to the same ACL if you want the same processing in both
30185 cases.
30186
30187 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
30188 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
30189 the case of a non-SMTP message. However, a MIME ACL is called only if the
30190 message contains a &'Content-Type:'& header line. When a call to a MIME
30191 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
30192 result code is sent to the client. In the case of an SMTP message, the
30193 &%acl_smtp_data%& ACL is not called when this happens.
30194
30195 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
30196 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
30197 condition to match against the raw MIME part. You can also use the
30198 &%mime_regex%& condition to match against the decoded MIME part (see section
30199 &<<SECTscanregex>>&).
30200
30201 At the start of a MIME ACL, a number of variables are set from the header
30202 information for the relevant MIME part. These are described below. The contents
30203 of the MIME part are not by default decoded into a disk file except for MIME
30204 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
30205 part into a disk file, you can use the &%decode%& condition. The general
30206 syntax is:
30207 .display
30208 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
30209 .endd
30210 The right hand side is expanded before use. After expansion,
30211 the value can be:
30212
30213 .olist
30214 &"0"& or &"false"&, in which case no decoding is done.
30215 .next
30216 The string &"default"&. In that case, the file is put in the temporary
30217 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
30218 a sequential file name consisting of the message id and a sequence number. The
30219 full path and name is available in &$mime_decoded_filename$& after decoding.
30220 .next
30221 A full path name starting with a slash. If the full name is an existing
30222 directory, it is used as a replacement for the default directory. The filename
30223 is then sequentially assigned. If the path does not exist, it is used as
30224 the full path and file name.
30225 .next
30226 If the string does not start with a slash, it is used as the
30227 filename, and the default path is then used.
30228 .endlist
30229 The &%decode%& condition normally succeeds. It is only false for syntax
30230 errors or unusual circumstances such as memory shortages. You can easily decode
30231 a file with its original, proposed filename using
30232 .code
30233 decode = $mime_filename
30234 .endd
30235 However, you should keep in mind that &$mime_filename$& might contain
30236 anything. If you place files outside of the default path, they are not
30237 automatically unlinked.
30238
30239 For RFC822 attachments (these are messages attached to messages, with a
30240 content-type of &"message/rfc822"&), the ACL is called again in the same manner
30241 as for the primary message, only that the &$mime_is_rfc822$& expansion
30242 variable is set (see below). Attached messages are always decoded to disk
30243 before being checked, and the files are unlinked once the check is done.
30244
30245 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
30246 used to match regular expressions against raw and decoded MIME parts,
30247 respectively. They are described in section &<<SECTscanregex>>&.
30248
30249 .cindex "MIME content scanning" "returned variables"
30250 The following list describes all expansion variables that are
30251 available in the MIME ACL:
30252
30253 .vlist
30254 .vitem &$mime_boundary$&
30255 If the current part is a multipart (see &$mime_is_multipart$&) below, it should
30256 have a boundary string, which is stored in this variable. If the current part
30257 has no boundary parameter in the &'Content-Type:'& header, this variable
30258 contains the empty string.
30259
30260 .vitem &$mime_charset$&
30261 This variable contains the character set identifier, if one was found in the
30262 &'Content-Type:'& header. Examples for charset identifiers are:
30263 .code
30264 us-ascii
30265 gb2312 (Chinese)
30266 iso-8859-1
30267 .endd
30268 Please note that this value is not normalized, so you should do matches
30269 case-insensitively.
30270
30271 .vitem &$mime_content_description$&
30272 This variable contains the normalized content of the &'Content-Description:'&
30273 header. It can contain a human-readable description of the parts content. Some
30274 implementations repeat the filename for attachments here, but they are usually
30275 only used for display purposes.
30276
30277 .vitem &$mime_content_disposition$&
30278 This variable contains the normalized content of the &'Content-Disposition:'&
30279 header. You can expect strings like &"attachment"& or &"inline"& here.
30280
30281 .vitem &$mime_content_id$&
30282 This variable contains the normalized content of the &'Content-ID:'& header.
30283 This is a unique ID that can be used to reference a part from another part.
30284
30285 .vitem &$mime_content_size$&
30286 This variable is set only after the &%decode%& modifier (see above) has been
30287 successfully run. It contains the size of the decoded part in kilobytes. The
30288 size is always rounded up to full kilobytes, so only a completely empty part
30289 has a &$mime_content_size$& of zero.
30290
30291 .vitem &$mime_content_transfer_encoding$&
30292 This variable contains the normalized content of the
30293 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
30294 type. Typical values are &"base64"& and &"quoted-printable"&.
30295
30296 .vitem &$mime_content_type$&
30297 If the MIME part has a &'Content-Type:'& header, this variable contains its
30298 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
30299 are some examples of popular MIME types, as they may appear in this variable:
30300 .code
30301 text/plain
30302 text/html
30303 application/octet-stream
30304 image/jpeg
30305 audio/midi
30306 .endd
30307 If the MIME part has no &'Content-Type:'& header, this variable contains the
30308 empty string.
30309
30310 .vitem &$mime_decoded_filename$&
30311 This variable is set only after the &%decode%& modifier (see above) has been
30312 successfully run. It contains the full path and file name of the file
30313 containing the decoded data.
30314 .endlist
30315
30316 .cindex "RFC 2047"
30317 .vlist
30318 .vitem &$mime_filename$&
30319 This is perhaps the most important of the MIME variables. It contains a
30320 proposed filename for an attachment, if one was found in either the
30321 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
30322 RFC2047 decoded, but no additional sanity checks are done. If no filename was
30323 found, this variable contains the empty string.
30324
30325 .vitem &$mime_is_coverletter$&
30326 This variable attempts to differentiate the &"cover letter"& of an e-mail from
30327 attached data. It can be used to clamp down on flashy or unnecessarily encoded
30328 content in the cover letter, while not restricting attachments at all.
30329
30330 The variable contains 1 (true) for a MIME part believed to be part of the
30331 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
30332 follows:
30333
30334 .olist
30335 The outermost MIME part of a message is always a cover letter.
30336
30337 .next
30338 If a multipart/alternative or multipart/related MIME part is a cover letter,
30339 so are all MIME subparts within that multipart.
30340
30341 .next
30342 If any other multipart is a cover letter, the first subpart is a cover letter,
30343 and the rest are attachments.
30344
30345 .next
30346 All parts contained within an attachment multipart are attachments.
30347 .endlist olist
30348
30349 As an example, the following will ban &"HTML mail"& (including that sent with
30350 alternative plain text), while allowing HTML files to be attached. HTML
30351 coverletter mail attached to non-HMTL coverletter mail will also be allowed:
30352 .code
30353 deny message = HTML mail is not accepted here
30354 !condition = $mime_is_rfc822
30355 condition = $mime_is_coverletter
30356 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
30357 .endd
30358 .vitem &$mime_is_multipart$&
30359 This variable has the value 1 (true) when the current part has the main type
30360 &"multipart"&, for example &"multipart/alternative"& or &"multipart/mixed"&.
30361 Since multipart entities only serve as containers for other parts, you may not
30362 want to carry out specific actions on them.
30363
30364 .vitem &$mime_is_rfc822$&
30365 This variable has the value 1 (true) if the current part is not a part of the
30366 checked message itself, but part of an attached message. Attached message
30367 decoding is fully recursive.
30368
30369 .vitem &$mime_part_count$&
30370 This variable is a counter that is raised for each processed MIME part. It
30371 starts at zero for the very first part (which is usually a multipart). The
30372 counter is per-message, so it is reset when processing RFC822 attachments (see
30373 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
30374 complete, so you can use it in the DATA ACL to determine the number of MIME
30375 parts of a message. For non-MIME messages, this variable contains the value -1.
30376 .endlist
30377
30378
30379
30380 .section "Scanning with regular expressions" "SECTscanregex"
30381 .cindex "content scanning" "with regular expressions"
30382 .cindex "regular expressions" "content scanning with"
30383 You can specify your own custom regular expression matches on the full body of
30384 the message, or on individual MIME parts.
30385
30386 The &%regex%& condition takes one or more regular expressions as arguments and
30387 matches them against the full message (when called in the DATA ACL) or a raw
30388 MIME part (when called in the MIME ACL). The &%regex%& condition matches
30389 linewise, with a maximum line length of 32K characters. That means you cannot
30390 have multiline matches with the &%regex%& condition.
30391
30392 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
30393 to 32K of decoded content (the whole content at once, not linewise). If the
30394 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
30395 is decoded automatically when &%mime_regex%& is executed (using default path
30396 and filename values). If the decoded data is larger than 32K, only the first
30397 32K characters are checked.
30398
30399 The regular expressions are passed as a colon-separated list. To include a
30400 literal colon, you must double it. Since the whole right-hand side string is
30401 expanded before being used, you must also escape dollar signs and backslashes
30402 with more backslashes, or use the &`\N`& facility to disable expansion.
30403 Here is a simple example that contains two regular expressions:
30404 .code
30405 deny message = contains blacklisted regex ($regex_match_string)
30406 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
30407 .endd
30408 The conditions returns true if any one of the regular expressions matches. The
30409 &$regex_match_string$& expansion variable is then set up and contains the
30410 matching regular expression.
30411
30412 &*Warning*&: With large messages, these conditions can be fairly
30413 CPU-intensive.
30414
30415
30416
30417
30418 .section "The demime condition" "SECTdemimecond"
30419 .cindex "content scanning" "MIME checking"
30420 .cindex "MIME content scanning"
30421 The &%demime%& ACL condition provides MIME unpacking, sanity checking and file
30422 extension blocking. It is usable only in the DATA and non-SMTP ACLs. The
30423 &%demime%& condition uses a simpler interface to MIME decoding than the MIME
30424 ACL functionality, but provides no additional facilities. Please note that this
30425 condition is deprecated and kept only for backward compatibility. You must set
30426 the WITH_OLD_DEMIME option in &_Local/Makefile_& at build time to be able to
30427 use the &%demime%& condition.
30428
30429 The &%demime%& condition unpacks MIME containers in the message. It detects
30430 errors in MIME containers and can match file extensions found in the message
30431 against a list. Using this facility produces files containing the unpacked MIME
30432 parts of the message in the temporary scan directory. If you do antivirus
30433 scanning, it is recommended that you use the &%demime%& condition before the
30434 antivirus (&%malware%&) condition.
30435
30436 On the right-hand side of the &%demime%& condition you can pass a
30437 colon-separated list of file extensions that it should match against. For
30438 example:
30439 .code
30440 deny message = Found blacklisted file attachment
30441 demime = vbs:com:bat:pif:prf:lnk
30442 .endd
30443 If one of the file extensions is found, the condition is true, otherwise it is
30444 false. If there is a temporary error while demimeing (for example, &"disk
30445 full"&), the condition defers, and the message is temporarily rejected (unless
30446 the condition is on a &%warn%& verb).
30447
30448 The right-hand side is expanded before being treated as a list, so you can have
30449 conditions and lookups there. If it expands to an empty string, &"false"&, or
30450 zero (&"0"&), no demimeing is done and the condition is false.
30451
30452 The &%demime%& condition set the following variables:
30453
30454 .vlist
30455 .vitem &$demime_errorlevel$&
30456 .vindex "&$demime_errorlevel$&"
30457 When an error is detected in a MIME container, this variable contains the
30458 severity of the error, as an integer number. The higher the value, the more
30459 severe the error (the current maximum value is 3). If this variable is unset or
30460 zero, no error occurred.
30461
30462 .vitem &$demime_reason$&
30463 .vindex "&$demime_reason$&"
30464 When &$demime_errorlevel$& is greater than zero, this variable contains a
30465 human-readable text string describing the MIME error that occurred.
30466 .endlist
30467
30468 .vlist
30469 .vitem &$found_extension$&
30470 .vindex "&$found_extension$&"
30471 When the &%demime%& condition is true, this variable contains the file
30472 extension it found.
30473 .endlist
30474
30475 Both &$demime_errorlevel$& and &$demime_reason$& are set by the first call of
30476 the &%demime%& condition, and are not changed on subsequent calls.
30477
30478 If you do not want to check for file extensions, but rather use the &%demime%&
30479 condition for unpacking or error checking purposes, pass &"*"& as the
30480 right-hand side value. Here is a more elaborate example of how to use this
30481 facility:
30482 .code
30483 # Reject messages with serious MIME container errors
30484 deny message = Found MIME error ($demime_reason).
30485 demime = *
30486 condition = ${if >{$demime_errorlevel}{2}{1}{0}}
30487
30488 # Reject known virus spreading file extensions.
30489 # Accepting these is pretty much braindead.
30490 deny message = contains $found_extension file (blacklisted).
30491 demime = com:vbs:bat:pif:scr
30492
30493 # Freeze .exe and .doc files. Postmaster can
30494 # examine them and eventually thaw them.
30495 deny log_message = Another $found_extension file.
30496 demime = exe:doc
30497 control = freeze
30498 .endd
30499 .ecindex IIDcosca
30500
30501
30502
30503
30504 . ////////////////////////////////////////////////////////////////////////////
30505 . ////////////////////////////////////////////////////////////////////////////
30506
30507 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
30508 "Local scan function"
30509 .scindex IIDlosca "&[local_scan()]& function" "description of"
30510 .cindex "customizing" "input scan using C function"
30511 .cindex "policy control" "by local scan function"
30512 In these days of email worms, viruses, and ever-increasing spam, some sites
30513 want to apply a lot of checking to messages before accepting them.
30514
30515 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
30516 passing messages to external virus and spam scanning software. You can also do
30517 a certain amount in Exim itself through string expansions and the &%condition%&
30518 condition in the ACL that runs after the SMTP DATA command or the ACL for
30519 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
30520
30521 To allow for further customization to a site's own requirements, there is the
30522 possibility of linking Exim with a private message scanning function, written
30523 in C. If you want to run code that is written in something other than C, you
30524 can of course use a little C stub to call it.
30525
30526 The local scan function is run once for every incoming message, at the point
30527 when Exim is just about to accept the message.
30528 It can therefore be used to control non-SMTP messages from local processes as
30529 well as messages arriving via SMTP.
30530
30531 Exim applies a timeout to calls of the local scan function, and there is an
30532 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
30533 Zero means &"no timeout"&.
30534 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
30535 before calling the local scan function, so that the most common types of crash
30536 are caught. If the timeout is exceeded or one of those signals is caught, the
30537 incoming message is rejected with a temporary error if it is an SMTP message.
30538 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
30539 code. The incident is logged on the main and reject logs.
30540
30541
30542
30543 .section "Building Exim to use a local scan function" "SECID207"
30544 .cindex "&[local_scan()]& function" "building Exim to use"
30545 To make use of the local scan function feature, you must tell Exim where your
30546 function is before building Exim, by setting LOCAL_SCAN_SOURCE in your
30547 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
30548 directory, so you might set
30549 .code
30550 LOCAL_SCAN_SOURCE=Local/local_scan.c
30551 .endd
30552 for example. The function must be called &[local_scan()]&. It is called by
30553 Exim after it has received a message, when the success return code is about to
30554 be sent. This is after all the ACLs have been run. The return code from your
30555 function controls whether the message is actually accepted or not. There is a
30556 commented template function (that just accepts the message) in the file
30557 _src/local_scan.c_.
30558
30559 If you want to make use of Exim's run time configuration file to set options
30560 for your &[local_scan()]& function, you must also set
30561 .code
30562 LOCAL_SCAN_HAS_OPTIONS=yes
30563 .endd
30564 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
30565
30566
30567
30568
30569 .section "API for local_scan()" "SECTapiforloc"
30570 .cindex "&[local_scan()]& function" "API description"
30571 You must include this line near the start of your code:
30572 .code
30573 #include "local_scan.h"
30574 .endd
30575 This header file defines a number of variables and other values, and the
30576 prototype for the function itself. Exim is coded to use unsigned char values
30577 almost exclusively, and one of the things this header defines is a shorthand
30578 for &`unsigned char`& called &`uschar`&.
30579 It also contains the following macro definitions, to simplify casting character
30580 strings and pointers to character strings:
30581 .code
30582 #define CS (char *)
30583 #define CCS (const char *)
30584 #define CSS (char **)
30585 #define US (unsigned char *)
30586 #define CUS (const unsigned char *)
30587 #define USS (unsigned char **)
30588 .endd
30589 The function prototype for &[local_scan()]& is:
30590 .code
30591 extern int local_scan(int fd, uschar **return_text);
30592 .endd
30593 The arguments are as follows:
30594
30595 .ilist
30596 &%fd%& is a file descriptor for the file that contains the body of the message
30597 (the -D file). The file is open for reading and writing, but updating it is not
30598 recommended. &*Warning*&: You must &'not'& close this file descriptor.
30599
30600 The descriptor is positioned at character 19 of the file, which is the first
30601 character of the body itself, because the first 19 characters are the message
30602 id followed by &`-D`& and a newline. If you rewind the file, you should use the
30603 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
30604 case this changes in some future version.
30605 .next
30606 &%return_text%& is an address which you can use to return a pointer to a text
30607 string at the end of the function. The value it points to on entry is NULL.
30608 .endlist
30609
30610 The function must return an &%int%& value which is one of the following macros:
30611
30612 .vlist
30613 .vitem &`LOCAL_SCAN_ACCEPT`&
30614 .vindex "&$local_scan_data$&"
30615 The message is accepted. If you pass back a string of text, it is saved with
30616 the message, and made available in the variable &$local_scan_data$&. No
30617 newlines are permitted (if there are any, they are turned into spaces) and the
30618 maximum length of text is 1000 characters.
30619
30620 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
30621 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
30622 queued without immediate delivery, and is frozen.
30623
30624 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
30625 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
30626 queued without immediate delivery.
30627
30628 .vitem &`LOCAL_SCAN_REJECT`&
30629 The message is rejected; the returned text is used as an error message which is
30630 passed back to the sender and which is also logged. Newlines are permitted &--
30631 they cause a multiline response for SMTP rejections, but are converted to
30632 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
30633 used.
30634
30635 .vitem &`LOCAL_SCAN_TEMPREJECT`&
30636 The message is temporarily rejected; the returned text is used as an error
30637 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
30638 problem"& is used.
30639
30640 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
30641 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
30642 message is not written to the reject log. It has the effect of unsetting the
30643 &%rejected_header%& log selector for just this rejection. If
30644 &%rejected_header%& is already unset (see the discussion of the
30645 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
30646 same as LOCAL_SCAN_REJECT.
30647
30648 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
30649 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
30650 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
30651 .endlist
30652
30653 If the message is not being received by interactive SMTP, rejections are
30654 reported by writing to &%stderr%& or by sending an email, as configured by the
30655 &%-oe%& command line options.
30656
30657
30658
30659 .section "Configuration options for local_scan()" "SECTconoptloc"
30660 .cindex "&[local_scan()]& function" "configuration options"
30661 It is possible to have option settings in the main configuration file
30662 that set values in static variables in the &[local_scan()]& module. If you
30663 want to do this, you must have the line
30664 .code
30665 LOCAL_SCAN_HAS_OPTIONS=yes
30666 .endd
30667 in your &_Local/Makefile_& when you build Exim. (This line is in
30668 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
30669 file, you must define static variables to hold the option values, and a table
30670 to define them.
30671
30672 The table must be a vector called &%local_scan_options%&, of type
30673 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
30674 and a pointer to the variable that holds the value. The entries must appear in
30675 alphabetical order. Following &%local_scan_options%& you must also define a
30676 variable called &%local_scan_options_count%& that contains the number of
30677 entries in the table. Here is a short example, showing two kinds of option:
30678 .code
30679 static int my_integer_option = 42;
30680 static uschar *my_string_option = US"a default string";
30681
30682 optionlist local_scan_options[] = {
30683 { "my_integer", opt_int, &my_integer_option },
30684 { "my_string", opt_stringptr, &my_string_option }
30685 };
30686
30687 int local_scan_options_count =
30688 sizeof(local_scan_options)/sizeof(optionlist);
30689 .endd
30690 The values of the variables can now be changed from Exim's runtime
30691 configuration file by including a local scan section as in this example:
30692 .code
30693 begin local_scan
30694 my_integer = 99
30695 my_string = some string of text...
30696 .endd
30697 The available types of option data are as follows:
30698
30699 .vlist
30700 .vitem &*opt_bool*&
30701 This specifies a boolean (true/false) option. The address should point to a
30702 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
30703 that are defined as &"1"& and &"0"&, respectively. If you want to detect
30704 whether such a variable has been set at all, you can initialize it to
30705 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
30706 values.)
30707
30708 .vitem &*opt_fixed*&
30709 This specifies a fixed point number, such as is used for load averages.
30710 The address should point to a variable of type &`int`&. The value is stored
30711 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
30712
30713 .vitem &*opt_int*&
30714 This specifies an integer; the address should point to a variable of type
30715 &`int`&. The value may be specified in any of the integer formats accepted by
30716 Exim.
30717
30718 .vitem &*opt_mkint*&
30719 This is the same as &%opt_int%&, except that when such a value is output in a
30720 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
30721 printed with the suffix K or M.
30722
30723 .vitem &*opt_octint*&
30724 This also specifies an integer, but the value is always interpreted as an
30725 octal integer, whether or not it starts with the digit zero, and it is
30726 always output in octal.
30727
30728 .vitem &*opt_stringptr*&
30729 This specifies a string value; the address must be a pointer to a
30730 variable that points to a string (for example, of type &`uschar *`&).
30731
30732 .vitem &*opt_time*&
30733 This specifies a time interval value. The address must point to a variable of
30734 type &`int`&. The value that is placed there is a number of seconds.
30735 .endlist
30736
30737 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
30738 out the values of all the &[local_scan()]& options.
30739
30740
30741
30742 .section "Available Exim variables" "SECID208"
30743 .cindex "&[local_scan()]& function" "available Exim variables"
30744 The header &_local_scan.h_& gives you access to a number of C variables. These
30745 are the only ones that are guaranteed to be maintained from release to release.
30746 Note, however, that you can obtain the value of any Exim expansion variable,
30747 including &$recipients$&, by calling &'expand_string()'&. The exported
30748 C variables are as follows:
30749
30750 .vlist
30751 .vitem &*int&~body_linecount*&
30752 This variable contains the number of lines in the message's body.
30753
30754 .vitem &*int&~body_zerocount*&
30755 This variable contains the number of binary zero bytes in the message's body.
30756
30757 .vitem &*unsigned&~int&~debug_selector*&
30758 This variable is set to zero when no debugging is taking place. Otherwise, it
30759 is a bitmap of debugging selectors. Two bits are identified for use in
30760 &[local_scan()]&; they are defined as macros:
30761
30762 .ilist
30763 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
30764 testing option that is not privileged &-- any caller may set it. All the
30765 other selector bits can be set only by admin users.
30766
30767 .next
30768 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
30769 by the &`+local_scan`& debug selector. It is not included in the default set
30770 of debugging bits.
30771 .endlist ilist
30772
30773 Thus, to write to the debugging output only when &`+local_scan`& has been
30774 selected, you should use code like this:
30775 .code
30776 if ((debug_selector & D_local_scan) != 0)
30777 debug_printf("xxx", ...);
30778 .endd
30779 .vitem &*uschar&~*expand_string_message*&
30780 After a failing call to &'expand_string()'& (returned value NULL), the
30781 variable &%expand_string_message%& contains the error message, zero-terminated.
30782
30783 .vitem &*header_line&~*header_list*&
30784 A pointer to a chain of header lines. The &%header_line%& structure is
30785 discussed below.
30786
30787 .vitem &*header_line&~*header_last*&
30788 A pointer to the last of the header lines.
30789
30790 .vitem &*uschar&~*headers_charset*&
30791 The value of the &%headers_charset%& configuration option.
30792
30793 .vitem &*BOOL&~host_checking*&
30794 This variable is TRUE during a host checking session that is initiated by the
30795 &%-bh%& command line option.
30796
30797 .vitem &*uschar&~*interface_address*&
30798 The IP address of the interface that received the message, as a string. This
30799 is NULL for locally submitted messages.
30800
30801 .vitem &*int&~interface_port*&
30802 The port on which this message was received. When testing with the &%-bh%&
30803 command line option, the value of this variable is -1 unless a port has been
30804 specified via the &%-oMi%& option.
30805
30806 .vitem &*uschar&~*message_id*&
30807 This variable contains Exim's message id for the incoming message (the value of
30808 &$message_exim_id$&) as a zero-terminated string.
30809
30810 .vitem &*uschar&~*received_protocol*&
30811 The name of the protocol by which the message was received.
30812
30813 .vitem &*int&~recipients_count*&
30814 The number of accepted recipients.
30815
30816 .vitem &*recipient_item&~*recipients_list*&
30817 .cindex "recipient" "adding in local scan"
30818 .cindex "recipient" "removing in local scan"
30819 The list of accepted recipients, held in a vector of length
30820 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
30821 can add additional recipients by calling &'receive_add_recipient()'& (see
30822 below). You can delete recipients by removing them from the vector and
30823 adjusting the value in &%recipients_count%&. In particular, by setting
30824 &%recipients_count%& to zero you remove all recipients. If you then return the
30825 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
30826 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
30827 and then call &'receive_add_recipient()'& as often as needed.
30828
30829 .vitem &*uschar&~*sender_address*&
30830 The envelope sender address. For bounce messages this is the empty string.
30831
30832 .vitem &*uschar&~*sender_host_address*&
30833 The IP address of the sending host, as a string. This is NULL for
30834 locally-submitted messages.
30835
30836 .vitem &*uschar&~*sender_host_authenticated*&
30837 The name of the authentication mechanism that was used, or NULL if the message
30838 was not received over an authenticated SMTP connection.
30839
30840 .vitem &*uschar&~*sender_host_name*&
30841 The name of the sending host, if known.
30842
30843 .vitem &*int&~sender_host_port*&
30844 The port on the sending host.
30845
30846 .vitem &*BOOL&~smtp_input*&
30847 This variable is TRUE for all SMTP input, including BSMTP.
30848
30849 .vitem &*BOOL&~smtp_batched_input*&
30850 This variable is TRUE for BSMTP input.
30851
30852 .vitem &*int&~store_pool*&
30853 The contents of this variable control which pool of memory is used for new
30854 requests. See section &<<SECTmemhanloc>>& for details.
30855 .endlist
30856
30857
30858 .section "Structure of header lines" "SECID209"
30859 The &%header_line%& structure contains the members listed below.
30860 You can add additional header lines by calling the &'header_add()'& function
30861 (see below). You can cause header lines to be ignored (deleted) by setting
30862 their type to *.
30863
30864
30865 .vlist
30866 .vitem &*struct&~header_line&~*next*&
30867 A pointer to the next header line, or NULL for the last line.
30868
30869 .vitem &*int&~type*&
30870 A code identifying certain headers that Exim recognizes. The codes are printing
30871 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
30872 Notice in particular that any header line whose type is * is not transmitted
30873 with the message. This flagging is used for header lines that have been
30874 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
30875 lines.) Effectively, * means &"deleted"&.
30876
30877 .vitem &*int&~slen*&
30878 The number of characters in the header line, including the terminating and any
30879 internal newlines.
30880
30881 .vitem &*uschar&~*text*&
30882 A pointer to the text of the header. It always ends with a newline, followed by
30883 a zero byte. Internal newlines are preserved.
30884 .endlist
30885
30886
30887
30888 .section "Structure of recipient items" "SECID210"
30889 The &%recipient_item%& structure contains these members:
30890
30891 .vlist
30892 .vitem &*uschar&~*address*&
30893 This is a pointer to the recipient address as it was received.
30894
30895 .vitem &*int&~pno*&
30896 This is used in later Exim processing when top level addresses are created by
30897 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
30898 and must always contain -1 at this stage.
30899
30900 .vitem &*uschar&~*errors_to*&
30901 If this value is not NULL, bounce messages caused by failing to deliver to the
30902 recipient are sent to the address it contains. In other words, it overrides the
30903 envelope sender for this one recipient. (Compare the &%errors_to%& generic
30904 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
30905 an unqualified address, Exim qualifies it using the domain from
30906 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
30907 is NULL for all recipients.
30908 .endlist
30909
30910
30911
30912 .section "Available Exim functions" "SECID211"
30913 .cindex "&[local_scan()]& function" "available Exim functions"
30914 The header &_local_scan.h_& gives you access to a number of Exim functions.
30915 These are the only ones that are guaranteed to be maintained from release to
30916 release:
30917
30918 .vlist
30919 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
30920 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
30921
30922 This function creates a child process that runs the command specified by
30923 &%argv%&. The environment for the process is specified by &%envp%&, which can
30924 be NULL if no environment variables are to be passed. A new umask is supplied
30925 for the process in &%newumask%&.
30926
30927 Pipes to the standard input and output of the new process are set up
30928 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
30929 standard error is cloned to the standard output. If there are any file
30930 descriptors &"in the way"& in the new process, they are closed. If the final
30931 argument is TRUE, the new process is made into a process group leader.
30932
30933 The function returns the pid of the new process, or -1 if things go wrong.
30934
30935 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
30936 This function waits for a child process to terminate, or for a timeout (in
30937 seconds) to expire. A timeout value of zero means wait as long as it takes. The
30938 return value is as follows:
30939
30940 .ilist
30941 >= 0
30942
30943 The process terminated by a normal exit and the value is the process
30944 ending status.
30945
30946 .next
30947 < 0 and > &--256
30948
30949 The process was terminated by a signal and the value is the negation of the
30950 signal number.
30951
30952 .next
30953 &--256
30954
30955 The process timed out.
30956 .next
30957 &--257
30958
30959 The was some other error in wait(); &%errno%& is still set.
30960 .endlist
30961
30962 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
30963 This function provide you with a means of submitting a new message to
30964 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
30965 want, but this packages it all up for you.) The function creates a pipe,
30966 forks a subprocess that is running
30967 .code
30968 exim -t -oem -oi -f <>
30969 .endd
30970 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
30971 that is connected to the standard input. The yield of the function is the PID
30972 of the subprocess. You can then write a message to the file descriptor, with
30973 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
30974
30975 When you have finished, call &'child_close()'& to wait for the process to
30976 finish and to collect its ending status. A timeout value of zero is usually
30977 fine in this circumstance. Unless you have made a mistake with the recipient
30978 addresses, you should get a return code of zero.
30979
30980
30981 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
30982 *sender_authentication)*&
30983 This function is a more sophisticated version of &'child_open()'&. The command
30984 that it runs is:
30985 .display
30986 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
30987 .endd
30988 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
30989
30990
30991 .vitem &*void&~debug_printf(char&~*,&~...)*&
30992 This is Exim's debugging function, with arguments as for &'(printf()'&. The
30993 output is written to the standard error stream. If no debugging is selected,
30994 calls to &'debug_printf()'& have no effect. Normally, you should make calls
30995 conditional on the &`local_scan`& debug selector by coding like this:
30996 .code
30997 if ((debug_selector & D_local_scan) != 0)
30998 debug_printf("xxx", ...);
30999 .endd
31000
31001 .vitem &*uschar&~*expand_string(uschar&~*string)*&
31002 This is an interface to Exim's string expansion code. The return value is the
31003 expanded string, or NULL if there was an expansion failure.
31004 The C variable &%expand_string_message%& contains an error message after an
31005 expansion failure. If expansion does not change the string, the return value is
31006 the pointer to the input string. Otherwise, the return value points to a new
31007 block of memory that was obtained by a call to &'store_get()'&. See section
31008 &<<SECTmemhanloc>>& below for a discussion of memory handling.
31009
31010 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
31011 This function allows you to an add additional header line at the end of the
31012 existing ones. The first argument is the type, and should normally be a space
31013 character. The second argument is a format string and any number of
31014 substitution arguments as for &[sprintf()]&. You may include internal newlines
31015 if you want, and you must ensure that the string ends with a newline.
31016
31017 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
31018 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
31019 This function adds a new header line at a specified point in the header
31020 chain. The header itself is specified as for &'header_add()'&.
31021
31022 If &%name%& is NULL, the new header is added at the end of the chain if
31023 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
31024 NULL, the header lines are searched for the first non-deleted header that
31025 matches the name. If one is found, the new header is added before it if
31026 &%after%& is false. If &%after%& is true, the new header is added after the
31027 found header and any adjacent subsequent ones with the same name (even if
31028 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
31029 option controls where the header is added. If it is true, addition is at the
31030 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
31031 headers, or at the top if there are no &'Received:'& headers, you could use
31032 .code
31033 header_add_at_position(TRUE, US"Received", TRUE,
31034 ' ', "X-xxx: ...");
31035 .endd
31036 Normally, there is always at least one non-deleted &'Received:'& header, but
31037 there may not be if &%received_header_text%& expands to an empty string.
31038
31039
31040 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
31041 This function removes header lines. If &%occurrence%& is zero or negative, all
31042 occurrences of the header are removed. If occurrence is greater than zero, that
31043 particular instance of the header is removed. If no header(s) can be found that
31044 match the specification, the function does nothing.
31045
31046
31047 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
31048 int&~length,&~BOOL&~notdel)*&"
31049 This function tests whether the given header has the given name. It is not just
31050 a string comparison, because white space is permitted between the name and the
31051 colon. If the &%notdel%& argument is true, a false return is forced for all
31052 &"deleted"& headers; otherwise they are not treated specially. For example:
31053 .code
31054 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
31055 .endd
31056 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
31057 .cindex "base64 encoding" "functions for &[local_scan()]& use"
31058 This function base64-encodes a string, which is passed by address and length.
31059 The text may contain bytes of any value, including zero. The result is passed
31060 back in dynamic memory that is obtained by calling &'store_get()'&. It is
31061 zero-terminated.
31062
31063 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
31064 This function decodes a base64-encoded string. Its arguments are a
31065 zero-terminated base64-encoded string and the address of a variable that is set
31066 to point to the result, which is in dynamic memory. The length of the decoded
31067 string is the yield of the function. If the input is invalid base64 data, the
31068 yield is -1. A zero byte is added to the end of the output string to make it
31069 easy to interpret as a C string (assuming it contains no zeros of its own). The
31070 added zero byte is not included in the returned count.
31071
31072 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
31073 This function checks for a match in a domain list. Domains are always
31074 matched caselessly. The return value is one of the following:
31075 .display
31076 &`OK `& match succeeded
31077 &`FAIL `& match failed
31078 &`DEFER `& match deferred
31079 .endd
31080 DEFER is usually caused by some kind of lookup defer, such as the
31081 inability to contact a database.
31082
31083 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
31084 BOOL&~caseless)*&"
31085 This function checks for a match in a local part list. The third argument
31086 controls case-sensitivity. The return values are as for
31087 &'lss_match_domain()'&.
31088
31089 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
31090 BOOL&~caseless)*&"
31091 This function checks for a match in an address list. The third argument
31092 controls the case-sensitivity of the local part match. The domain is always
31093 matched caselessly. The return values are as for &'lss_match_domain()'&.
31094
31095 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
31096 uschar&~*list)*&"
31097 This function checks for a match in a host list. The most common usage is
31098 expected to be
31099 .code
31100 lss_match_host(sender_host_name, sender_host_address, ...)
31101 .endd
31102 .vindex "&$sender_host_address$&"
31103 An empty address field matches an empty item in the host list. If the host name
31104 is NULL, the name corresponding to &$sender_host_address$& is automatically
31105 looked up if a host name is required to match an item in the list. The return
31106 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
31107 returns ERROR in the case when it had to look up a host name, but the lookup
31108 failed.
31109
31110 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
31111 *format,&~...)*&"
31112 This function writes to Exim's log files. The first argument should be zero (it
31113 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
31114 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
31115 them. It specifies to which log or logs the message is written. The remaining
31116 arguments are a format and relevant insertion arguments. The string should not
31117 contain any newlines, not even at the end.
31118
31119
31120 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
31121 This function adds an additional recipient to the message. The first argument
31122 is the recipient address. If it is unqualified (has no domain), it is qualified
31123 with the &%qualify_recipient%& domain. The second argument must always be -1.
31124
31125 This function does not allow you to specify a private &%errors_to%& address (as
31126 described with the structure of &%recipient_item%& above), because it pre-dates
31127 the addition of that field to the structure. However, it is easy to add such a
31128 value afterwards. For example:
31129 .code
31130 receive_add_recipient(US"monitor@mydom.example", -1);
31131 recipients_list[recipients_count-1].errors_to =
31132 US"postmaster@mydom.example";
31133 .endd
31134
31135 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
31136 This is a convenience function to remove a named recipient from the list of
31137 recipients. It returns true if a recipient was removed, and false if no
31138 matching recipient could be found. The argument must be a complete email
31139 address.
31140 .endlist
31141
31142
31143 .cindex "RFC 2047"
31144 .vlist
31145 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
31146 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
31147 This function decodes strings that are encoded according to RFC 2047. Typically
31148 these are the contents of header lines. First, each &"encoded word"& is decoded
31149 from the Q or B encoding into a byte-string. Then, if provided with the name of
31150 a charset encoding, and if the &[iconv()]& function is available, an attempt is
31151 made to translate the result to the named character set. If this fails, the
31152 binary string is returned with an error message.
31153
31154 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
31155 maximum MIME word length is enforced. The third argument is the target
31156 encoding, or NULL if no translation is wanted.
31157
31158 .cindex "binary zero" "in RFC 2047 decoding"
31159 .cindex "RFC 2047" "binary zero in"
31160 If a binary zero is encountered in the decoded string, it is replaced by the
31161 contents of the &%zeroval%& argument. For use with Exim headers, the value must
31162 not be 0 because header lines are handled as zero-terminated strings.
31163
31164 The function returns the result of processing the string, zero-terminated; if
31165 &%lenptr%& is not NULL, the length of the result is set in the variable to
31166 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
31167
31168 If an error is encountered, the function returns NULL and uses the &%error%&
31169 argument to return an error message. The variable pointed to by &%error%& is
31170 set to NULL if there is no error; it may be set non-NULL even when the function
31171 returns a non-NULL value if decoding was successful, but there was a problem
31172 with translation.
31173
31174
31175 .vitem &*int&~smtp_fflush(void)*&
31176 This function is used in conjunction with &'smtp_printf()'&, as described
31177 below.
31178
31179 .vitem &*void&~smtp_printf(char&~*,&~...)*&
31180 The arguments of this function are like &[printf()]&; it writes to the SMTP
31181 output stream. You should use this function only when there is an SMTP output
31182 stream, that is, when the incoming message is being received via interactive
31183 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
31184 is FALSE. If you want to test for an incoming message from another host (as
31185 opposed to a local process that used the &%-bs%& command line option), you can
31186 test the value of &%sender_host_address%&, which is non-NULL when a remote host
31187 is involved.
31188
31189 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
31190 output function, so it can be used for all forms of SMTP connection.
31191
31192 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
31193 must start with an appropriate response code: 550 if you are going to return
31194 LOCAL_SCAN_REJECT, 451 if you are going to return
31195 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
31196 initial lines of a multi-line response, the code must be followed by a hyphen
31197 to indicate that the line is not the final response line. You must also ensure
31198 that the lines you write terminate with CRLF. For example:
31199 .code
31200 smtp_printf("550-this is some extra info\r\n");
31201 return LOCAL_SCAN_REJECT;
31202 .endd
31203 Note that you can also create multi-line responses by including newlines in
31204 the data returned via the &%return_text%& argument. The added value of using
31205 &'smtp_printf()'& is that, for instance, you could introduce delays between
31206 multiple output lines.
31207
31208 The &'smtp_printf()'& function does not return any error indication, because it
31209 does not automatically flush pending output, and therefore does not test
31210 the state of the stream. (In the main code of Exim, flushing and error
31211 detection is done when Exim is ready for the next SMTP input command.) If
31212 you want to flush the output and check for an error (for example, the
31213 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
31214 arguments. It flushes the output stream, and returns a non-zero value if there
31215 is an error.
31216
31217 .vitem &*void&~*store_get(int)*&
31218 This function accesses Exim's internal store (memory) manager. It gets a new
31219 chunk of memory whose size is given by the argument. Exim bombs out if it ever
31220 runs out of memory. See the next section for a discussion of memory handling.
31221
31222 .vitem &*void&~*store_get_perm(int)*&
31223 This function is like &'store_get()'&, but it always gets memory from the
31224 permanent pool. See the next section for a discussion of memory handling.
31225
31226 .vitem &*uschar&~*string_copy(uschar&~*string)*&
31227 See below.
31228
31229 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
31230 See below.
31231
31232 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
31233 These three functions create strings using Exim's dynamic memory facilities.
31234 The first makes a copy of an entire string. The second copies up to a maximum
31235 number of characters, indicated by the second argument. The third uses a format
31236 and insertion arguments to create a new string. In each case, the result is a
31237 pointer to a new string in the current memory pool. See the next section for
31238 more discussion.
31239 .endlist
31240
31241
31242
31243 .section "More about Exim's memory handling" "SECTmemhanloc"
31244 .cindex "&[local_scan()]& function" "memory handling"
31245 No function is provided for freeing memory, because that is never needed.
31246 The dynamic memory that Exim uses when receiving a message is automatically
31247 recycled if another message is received by the same process (this applies only
31248 to incoming SMTP connections &-- other input methods can supply only one
31249 message at a time). After receiving the last message, a reception process
31250 terminates.
31251
31252 Because it is recycled, the normal dynamic memory cannot be used for holding
31253 data that must be preserved over a number of incoming messages on the same SMTP
31254 connection. However, Exim in fact uses two pools of dynamic memory; the second
31255 one is not recycled, and can be used for this purpose.
31256
31257 If you want to allocate memory that remains available for subsequent messages
31258 in the same SMTP connection, you should set
31259 .code
31260 store_pool = POOL_PERM
31261 .endd
31262 before calling the function that does the allocation. There is no need to
31263 restore the value if you do not need to; however, if you do want to revert to
31264 the normal pool, you can either restore the previous value of &%store_pool%& or
31265 set it explicitly to POOL_MAIN.
31266
31267 The pool setting applies to all functions that get dynamic memory, including
31268 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
31269 There is also a convenience function called &'store_get_perm()'& that gets a
31270 block of memory from the permanent pool while preserving the value of
31271 &%store_pool%&.
31272 .ecindex IIDlosca
31273
31274
31275
31276
31277 . ////////////////////////////////////////////////////////////////////////////
31278 . ////////////////////////////////////////////////////////////////////////////
31279
31280 .chapter "System-wide message filtering" "CHAPsystemfilter"
31281 .scindex IIDsysfil1 "filter" "system filter"
31282 .scindex IIDsysfil2 "filtering all mail"
31283 .scindex IIDsysfil3 "system filter"
31284 The previous chapters (on ACLs and the local scan function) describe checks
31285 that can be applied to messages before they are accepted by a host. There is
31286 also a mechanism for checking messages once they have been received, but before
31287 they are delivered. This is called the &'system filter'&.
31288
31289 The system filter operates in a similar manner to users' filter files, but it
31290 is run just once per message (however many recipients the message has).
31291 It should not normally be used as a substitute for routing, because &%deliver%&
31292 commands in a system router provide new envelope recipient addresses.
31293 The system filter must be an Exim filter. It cannot be a Sieve filter.
31294
31295 The system filter is run at the start of a delivery attempt, before any routing
31296 is done. If a message fails to be completely delivered at the first attempt,
31297 the system filter is run again at the start of every retry.
31298 If you want your filter to do something only once per message, you can make use
31299 of the &%first_delivery%& condition in an &%if%& command in the filter to
31300 prevent it happening on retries.
31301
31302 .vindex "&$domain$&"
31303 .vindex "&$local_part$&"
31304 &*Warning*&: Because the system filter runs just once, variables that are
31305 specific to individual recipient addresses, such as &$local_part$& and
31306 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
31307 you want to run a centrally-specified filter for each recipient address
31308 independently, you can do so by setting up a suitable &(redirect)& router, as
31309 described in section &<<SECTperaddfil>>& below.
31310
31311
31312 .section "Specifying a system filter" "SECID212"
31313 .cindex "uid (user id)" "system filter"
31314 .cindex "gid (group id)" "system filter"
31315 The name of the file that contains the system filter must be specified by
31316 setting &%system_filter%&. If you want the filter to run under a uid and gid
31317 other than root, you must also set &%system_filter_user%& and
31318 &%system_filter_group%& as appropriate. For example:
31319 .code
31320 system_filter = /etc/mail/exim.filter
31321 system_filter_user = exim
31322 .endd
31323 If a system filter generates any deliveries directly to files or pipes (via the
31324 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
31325 specified by setting &%system_filter_file_transport%& and
31326 &%system_filter_pipe_transport%&, respectively. Similarly,
31327 &%system_filter_reply_transport%& must be set to handle any messages generated
31328 by the &%reply%& command.
31329
31330
31331 .section "Testing a system filter" "SECID213"
31332 You can run simple tests of a system filter in the same way as for a user
31333 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
31334 are permitted only in system filters are recognized.
31335
31336 If you want to test the combined effect of a system filter and a user filter,
31337 you can use both &%-bF%& and &%-bf%& on the same command line.
31338
31339
31340
31341 .section "Contents of a system filter" "SECID214"
31342 The language used to specify system filters is the same as for users' filter
31343 files. It is described in the separate end-user document &'Exim's interface to
31344 mail filtering'&. However, there are some additional features that are
31345 available only in system filters; these are described in subsequent sections.
31346 If they are encountered in a user's filter file or when testing with &%-bf%&,
31347 they cause errors.
31348
31349 .cindex "frozen messages" "manual thaw; testing in filter"
31350 There are two special conditions which, though available in users' filter
31351 files, are designed for use in system filters. The condition &%first_delivery%&
31352 is true only for the first attempt at delivering a message, and
31353 &%manually_thawed%& is true only if the message has been frozen, and
31354 subsequently thawed by an admin user. An explicit forced delivery counts as a
31355 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
31356
31357 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
31358 specify an &"unseen"& (non-significant) delivery, and that delivery does not
31359 succeed, it will not be tried again.
31360 If you want Exim to retry an unseen delivery until it succeeds, you should
31361 arrange to set it up every time the filter runs.
31362
31363 When a system filter finishes running, the values of the variables &$n0$& &--
31364 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
31365 users' filter files. Thus a system filter can, for example, set up &"scores"&
31366 to which users' filter files can refer.
31367
31368
31369
31370 .section "Additional variable for system filters" "SECID215"
31371 .vindex "&$recipients$&"
31372 The expansion variable &$recipients$&, containing a list of all the recipients
31373 of the message (separated by commas and white space), is available in system
31374 filters. It is not available in users' filters for privacy reasons.
31375
31376
31377
31378 .section "Defer, freeze, and fail commands for system filters" "SECID216"
31379 .cindex "freezing messages"
31380 .cindex "message" "freezing"
31381 .cindex "message" "forced failure"
31382 .cindex "&%fail%&" "in system filter"
31383 .cindex "&%freeze%& in system filter"
31384 .cindex "&%defer%& in system filter"
31385 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
31386 always available in system filters, but are not normally enabled in users'
31387 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
31388 for the &(redirect)& router.) These commands can optionally be followed by the
31389 word &%text%& and a string containing an error message, for example:
31390 .code
31391 fail text "this message looks like spam to me"
31392 .endd
31393 The keyword &%text%& is optional if the next character is a double quote.
31394
31395 The &%defer%& command defers delivery of the original recipients of the
31396 message. The &%fail%& command causes all the original recipients to be failed,
31397 and a bounce message to be created. The &%freeze%& command suspends all
31398 delivery attempts for the original recipients. In all cases, any new deliveries
31399 that are specified by the filter are attempted as normal after the filter has
31400 run.
31401
31402 The &%freeze%& command is ignored if the message has been manually unfrozen and
31403 not manually frozen since. This means that automatic freezing by a system
31404 filter can be used as a way of checking out suspicious messages. If a message
31405 is found to be all right, manually unfreezing it allows it to be delivered.
31406
31407 .cindex "log" "&%fail%& command log line"
31408 .cindex "&%fail%&" "log line; reducing"
31409 The text given with a fail command is used as part of the bounce message as
31410 well as being written to the log. If the message is quite long, this can fill
31411 up a lot of log space when such failures are common. To reduce the size of the
31412 log message, Exim interprets the text in a special way if it starts with the
31413 two characters &`<<`& and contains &`>>`& later. The text between these two
31414 strings is written to the log, and the rest of the text is used in the bounce
31415 message. For example:
31416 .code
31417 fail "<<filter test 1>>Your message is rejected \
31418 because it contains attachments that we are \
31419 not prepared to receive."
31420 .endd
31421
31422 .cindex "loop" "caused by &%fail%&"
31423 Take great care with the &%fail%& command when basing the decision to fail on
31424 the contents of the message, because the bounce message will of course include
31425 the contents of the original message and will therefore trigger the &%fail%&
31426 command again (causing a mail loop) unless steps are taken to prevent this.
31427 Testing the &%error_message%& condition is one way to prevent this. You could
31428 use, for example
31429 .code
31430 if $message_body contains "this is spam" and not error_message
31431 then fail text "spam is not wanted here" endif
31432 .endd
31433 though of course that might let through unwanted bounce messages. The
31434 alternative is clever checking of the body and/or headers to detect bounces
31435 generated by the filter.
31436
31437 The interpretation of a system filter file ceases after a
31438 &%defer%&,
31439 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
31440 set up earlier in the filter file are honoured, so you can use a sequence such
31441 as
31442 .code
31443 mail ...
31444 freeze
31445 .endd
31446 to send a specified message when the system filter is freezing (or deferring or
31447 failing) a message. The normal deliveries for the message do not, of course,
31448 take place.
31449
31450
31451
31452 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
31453 .cindex "header lines" "adding; in system filter"
31454 .cindex "header lines" "removing; in system filter"
31455 .cindex "filter" "header lines; adding/removing"
31456 Two filter commands that are available only in system filters are:
31457 .code
31458 headers add <string>
31459 headers remove <string>
31460 .endd
31461 The argument for the &%headers add%& is a string that is expanded and then
31462 added to the end of the message's headers. It is the responsibility of the
31463 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
31464 space is ignored, and if the string is otherwise empty, or if the expansion is
31465 forced to fail, the command has no effect.
31466
31467 You can use &"\n"& within the string, followed by white space, to specify
31468 continued header lines. More than one header may be added in one command by
31469 including &"\n"& within the string without any following white space. For
31470 example:
31471 .code
31472 headers add "X-header-1: ....\n \
31473 continuation of X-header-1 ...\n\
31474 X-header-2: ...."
31475 .endd
31476 Note that the header line continuation white space after the first newline must
31477 be placed before the backslash that continues the input string, because white
31478 space after input continuations is ignored.
31479
31480 The argument for &%headers remove%& is a colon-separated list of header names.
31481 This command applies only to those headers that are stored with the message;
31482 those that are added at delivery time (such as &'Envelope-To:'& and
31483 &'Return-Path:'&) cannot be removed by this means. If there is more than one
31484 header with the same name, they are all removed.
31485
31486 The &%headers%& command in a system filter makes an immediate change to the set
31487 of header lines that was received with the message (with possible additions
31488 from ACL processing). Subsequent commands in the system filter operate on the
31489 modified set, which also forms the basis for subsequent message delivery.
31490 Unless further modified during routing or transporting, this set of headers is
31491 used for all recipients of the message.
31492
31493 During routing and transporting, the variables that refer to the contents of
31494 header lines refer only to those lines that are in this set. Thus, header lines
31495 that are added by a system filter are visible to users' filter files and to all
31496 routers and transports. This contrasts with the manipulation of header lines by
31497 routers and transports, which is not immediate, but which instead is saved up
31498 until the message is actually being written (see section
31499 &<<SECTheadersaddrem>>&).
31500
31501 If the message is not delivered at the first attempt, header lines that were
31502 added by the system filter are stored with the message, and so are still
31503 present at the next delivery attempt. Header lines that were removed are still
31504 present, but marked &"deleted"& so that they are not transported with the
31505 message. For this reason, it is usual to make the &%headers%& command
31506 conditional on &%first_delivery%& so that the set of header lines is not
31507 modified more than once.
31508
31509 Because header modification in a system filter acts immediately, you have to
31510 use an indirect approach if you want to modify the contents of a header line.
31511 For example:
31512 .code
31513 headers add "Old-Subject: $h_subject:"
31514 headers remove "Subject"
31515 headers add "Subject: new subject (was: $h_old-subject:)"
31516 headers remove "Old-Subject"
31517 .endd
31518
31519
31520
31521 .section "Setting an errors address in a system filter" "SECID217"
31522 .cindex "envelope sender"
31523 In a system filter, if a &%deliver%& command is followed by
31524 .code
31525 errors_to <some address>
31526 .endd
31527 in order to change the envelope sender (and hence the error reporting) for that
31528 delivery, any address may be specified. (In a user filter, only the current
31529 user's address can be set.) For example, if some mail is being monitored, you
31530 might use
31531 .code
31532 unseen deliver monitor@spying.example errors_to root@local.example
31533 .endd
31534 to take a copy which would not be sent back to the normal error reporting
31535 address if its delivery failed.
31536
31537
31538
31539 .section "Per-address filtering" "SECTperaddfil"
31540 .vindex "&$domain$&"
31541 .vindex "&$local_part$&"
31542 In contrast to the system filter, which is run just once per message for each
31543 delivery attempt, it is also possible to set up a system-wide filtering
31544 operation that runs once for each recipient address. In this case, variables
31545 such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
31546 filter file could be made dependent on them. This is an example of a router
31547 which implements such a filter:
31548 .code
31549 central_filter:
31550 check_local_user
31551 driver = redirect
31552 domains = +local_domains
31553 file = /central/filters/$local_part
31554 no_verify
31555 allow_filter
31556 allow_freeze
31557 .endd
31558 The filter is run in a separate process under its own uid. Therefore, either
31559 &%check_local_user%& must be set (as above), in which case the filter is run as
31560 the local user, or the &%user%& option must be used to specify which user to
31561 use. If both are set, &%user%& overrides.
31562
31563 Care should be taken to ensure that none of the commands in the filter file
31564 specify a significant delivery if the message is to go on to be delivered to
31565 its intended recipient. The router will not then claim to have dealt with the
31566 address, so it will be passed on to subsequent routers to be delivered in the
31567 normal way.
31568 .ecindex IIDsysfil1
31569 .ecindex IIDsysfil2
31570 .ecindex IIDsysfil3
31571
31572
31573
31574
31575
31576
31577 . ////////////////////////////////////////////////////////////////////////////
31578 . ////////////////////////////////////////////////////////////////////////////
31579
31580 .chapter "Message processing" "CHAPmsgproc"
31581 .scindex IIDmesproc "message" "general processing"
31582 Exim performs various transformations on the sender and recipient addresses of
31583 all messages that it handles, and also on the messages' header lines. Some of
31584 these are optional and configurable, while others always take place. All of
31585 this processing, except rewriting as a result of routing, and the addition or
31586 removal of header lines while delivering, happens when a message is received,
31587 before it is placed on Exim's queue.
31588
31589 Some of the automatic processing takes place by default only for
31590 &"locally-originated"& messages. This adjective is used to describe messages
31591 that are not received over TCP/IP, but instead are passed to an Exim process on
31592 its standard input. This includes the interactive &"local SMTP"& case that is
31593 set up by the &%-bs%& command line option.
31594
31595 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
31596 or ::1) are not considered to be locally-originated. Exim does not treat the
31597 loopback interface specially in any way.
31598
31599 If you want the loopback interface to be treated specially, you must ensure
31600 that there are appropriate entries in your ACLs.
31601
31602
31603
31604
31605 .section "Submission mode for non-local messages" "SECTsubmodnon"
31606 .cindex "message" "submission"
31607 .cindex "submission mode"
31608 Processing that happens automatically for locally-originated messages (unless
31609 &%suppress_local_fixups%& is set) can also be requested for messages that are
31610 received over TCP/IP. The term &"submission mode"& is used to describe this
31611 state. Submission mode is set by the modifier
31612 .code
31613 control = submission
31614 .endd
31615 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
31616 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
31617 a local submission, and is normally used when the source of the message is
31618 known to be an MUA running on a client host (as opposed to an MTA). For
31619 example, to set submission mode for messages originating on the IPv4 loopback
31620 interface, you could include the following in the MAIL ACL:
31621 .code
31622 warn hosts = 127.0.0.1
31623 control = submission
31624 .endd
31625 .cindex "&%sender_retain%& submission option"
31626 There are some options that can be used when setting submission mode. A slash
31627 is used to separate options. For example:
31628 .code
31629 control = submission/sender_retain
31630 .endd
31631 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
31632 true and &%local_from_check%& false for the current incoming message. The first
31633 of these allows an existing &'Sender:'& header in the message to remain, and
31634 the second suppresses the check to ensure that &'From:'& matches the
31635 authenticated sender. With this setting, Exim still fixes up messages by adding
31636 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
31637 attempt to check sender authenticity in header lines.
31638
31639 When &%sender_retain%& is not set, a submission mode setting may specify a
31640 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
31641 example:
31642 .code
31643 control = submission/domain=some.domain
31644 .endd
31645 The domain may be empty. How this value is used is described in sections
31646 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
31647 that allows you to specify the user's full name for inclusion in a created
31648 &'Sender:'& or &'From:'& header line. For example:
31649 .code
31650 accept authenticated = *
31651 control = submission/domain=wonderland.example/\
31652 name=${lookup {$authenticated_id} \
31653 lsearch {/etc/exim/namelist}}
31654 .endd
31655 Because the name may contain any characters, including slashes, the &%name%&
31656 option must be given last. The remainder of the string is used as the name. For
31657 the example above, if &_/etc/exim/namelist_& contains:
31658 .code
31659 bigegg: Humpty Dumpty
31660 .endd
31661 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
31662 line would be:
31663 .code
31664 Sender: Humpty Dumpty <bigegg@wonderland.example>
31665 .endd
31666 .cindex "return path" "in submission mode"
31667 By default, submission mode forces the return path to the same address as is
31668 used to create the &'Sender:'& header. However, if &%sender_retain%& is
31669 specified, the return path is also left unchanged.
31670
31671 &*Note*&: The changes caused by submission mode take effect after the predata
31672 ACL. This means that any sender checks performed before the fix-ups use the
31673 untrusted sender address specified by the user, not the trusted sender address
31674 specified by submission mode. Although this might be slightly unexpected, it
31675 does mean that you can configure ACL checks to spot that a user is trying to
31676 spoof another's address.
31677
31678 .section "Line endings" "SECTlineendings"
31679 .cindex "line endings"
31680 .cindex "carriage return"
31681 .cindex "linefeed"
31682 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
31683 linefeed) is the line ending for messages transmitted over the Internet using
31684 SMTP over TCP/IP. However, within individual operating systems, different
31685 conventions are used. For example, Unix-like systems use just LF, but others
31686 use CRLF or just CR.
31687
31688 Exim was designed for Unix-like systems, and internally, it stores messages
31689 using the system's convention of a single LF as a line terminator. When
31690 receiving a message, all line endings are translated to this standard format.
31691 Originally, it was thought that programs that passed messages directly to an
31692 MTA within an operating system would use that system's convention. Experience
31693 has shown that this is not the case; for example, there are Unix applications
31694 that use CRLF in this circumstance. For this reason, and for compatibility with
31695 other MTAs, the way Exim handles line endings for all messages is now as
31696 follows:
31697
31698 .ilist
31699 LF not preceded by CR is treated as a line ending.
31700 .next
31701 CR is treated as a line ending; if it is immediately followed by LF, the LF
31702 is ignored.
31703 .next
31704 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
31705 nor a local message in the state where a line containing only a dot is a
31706 terminator.
31707 .next
31708 If a bare CR is encountered within a header line, an extra space is added after
31709 the line terminator so as not to end the header line. The reasoning behind this
31710 is that bare CRs in header lines are most likely either to be mistakes, or
31711 people trying to play silly games.
31712 .next
31713 If the first header line received in a message ends with CRLF, a subsequent
31714 bare LF in a header line is treated in the same way as a bare CR in a header
31715 line.
31716 .endlist
31717
31718
31719
31720
31721
31722 .section "Unqualified addresses" "SECID218"
31723 .cindex "unqualified addresses"
31724 .cindex "address" "qualification"
31725 By default, Exim expects every envelope address it receives from an external
31726 host to be fully qualified. Unqualified addresses cause negative responses to
31727 SMTP commands. However, because SMTP is used as a means of transporting
31728 messages from MUAs running on personal workstations, there is sometimes a
31729 requirement to accept unqualified addresses from specific hosts or IP networks.
31730
31731 Exim has two options that separately control which hosts may send unqualified
31732 sender or recipient addresses in SMTP commands, namely
31733 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
31734 cases, if an unqualified address is accepted, it is qualified by adding the
31735 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
31736
31737 .oindex "&%qualify_domain%&"
31738 .oindex "&%qualify_recipient%&"
31739 Unqualified addresses in header lines are automatically qualified for messages
31740 that are locally originated, unless the &%-bnq%& option is given on the command
31741 line. For messages received over SMTP, unqualified addresses in header lines
31742 are qualified only if unqualified addresses are permitted in SMTP commands. In
31743 other words, such qualification is also controlled by
31744 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
31745
31746
31747
31748
31749 .section "The UUCP From line" "SECID219"
31750 .cindex "&""From""& line"
31751 .cindex "UUCP" "&""From""& line"
31752 .cindex "sender" "address"
31753 .oindex "&%uucp_from_pattern%&"
31754 .oindex "&%uucp_from_sender%&"
31755 .cindex "envelope sender"
31756 .cindex "Sendmail compatibility" "&""From""& line"
31757 Messages that have come from UUCP (and some other applications) often begin
31758 with a line containing the envelope sender and a timestamp, following the word
31759 &"From"&. Examples of two common formats are:
31760 .code
31761 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
31762 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
31763 .endd
31764 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
31765 Exim recognizes such lines at the start of messages that are submitted to it
31766 via the command line (that is, on the standard input). It does not recognize
31767 such lines in incoming SMTP messages, unless the sending host matches
31768 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
31769 and &%ignore_fromline_local%& is set. The recognition is controlled by a
31770 regular expression that is defined by the &%uucp_from_pattern%& option, whose
31771 default value matches the two common cases shown above and puts the address
31772 that follows &"From"& into &$1$&.
31773
31774 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
31775 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
31776 a trusted user, the message's sender address is constructed by expanding the
31777 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
31778 then parsed as an RFC 2822 address. If there is no domain, the local part is
31779 qualified with &%qualify_domain%& unless it is the empty string. However, if
31780 the command line &%-f%& option is used, it overrides the &"From"& line.
31781
31782 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
31783 sender address is not changed. This is also the case for incoming SMTP messages
31784 that are permitted to contain &"From"& lines.
31785
31786 Only one &"From"& line is recognized. If there is more than one, the second is
31787 treated as a data line that starts the body of the message, as it is not valid
31788 as a header line. This also happens if a &"From"& line is present in an
31789 incoming SMTP message from a source that is not permitted to send them.
31790
31791
31792
31793 .section "Resent- header lines" "SECID220"
31794 .cindex "&%Resent-%& header lines"
31795 RFC 2822 makes provision for sets of header lines starting with the string
31796 &`Resent-`& to be added to a message when it is resent by the original
31797 recipient to somebody else. These headers are &'Resent-Date:'&,
31798 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
31799 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
31800
31801 .blockquote
31802 &'Resent fields are strictly informational. They MUST NOT be used in the normal
31803 processing of replies or other such automatic actions on messages.'&
31804 .endblockquote
31805
31806 This leaves things a bit vague as far as other processing actions such as
31807 address rewriting are concerned. Exim treats &%Resent-%& header lines as
31808 follows:
31809
31810 .ilist
31811 A &'Resent-From:'& line that just contains the login id of the submitting user
31812 is automatically rewritten in the same way as &'From:'& (see below).
31813 .next
31814 If there's a rewriting rule for a particular header line, it is also applied to
31815 &%Resent-%& header lines of the same type. For example, a rule that rewrites
31816 &'From:'& also rewrites &'Resent-From:'&.
31817 .next
31818 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
31819 also removed.
31820 .next
31821 For a locally-submitted message,
31822 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
31823 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
31824 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
31825 included in log lines in this case.
31826 .next
31827 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
31828 &%Resent-%& header lines are present.
31829 .endlist
31830
31831
31832
31833
31834 .section "The Auto-Submitted: header line" "SECID221"
31835 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
31836 includes the header line:
31837 .code
31838 Auto-Submitted: auto-replied
31839 .endd
31840
31841 .section "The Bcc: header line" "SECID222"
31842 .cindex "&'Bcc:'& header line"
31843 If Exim is called with the &%-t%& option, to take recipient addresses from a
31844 message's header, it removes any &'Bcc:'& header line that may exist (after
31845 extracting its addresses). If &%-t%& is not present on the command line, any
31846 existing &'Bcc:'& is not removed.
31847
31848
31849 .section "The Date: header line" "SECID223"
31850 .cindex "&'Date:'& header line"
31851 If a locally-generated or submission-mode message has no &'Date:'& header line,
31852 Exim adds one, using the current date and time, unless the
31853 &%suppress_local_fixups%& control has been specified.
31854
31855 .section "The Delivery-date: header line" "SECID224"
31856 .cindex "&'Delivery-date:'& header line"
31857 .oindex "&%delivery_date_remove%&"
31858 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
31859 set. Exim can be configured to add them to the final delivery of messages. (See
31860 the generic &%delivery_date_add%& transport option.) They should not be present
31861 in messages in transit. If the &%delivery_date_remove%& configuration option is
31862 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
31863 messages.
31864
31865
31866 .section "The Envelope-to: header line" "SECID225"
31867 .cindex "&'Envelope-to:'& header line"
31868 .oindex "&%envelope_to_remove%&"
31869 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
31870 Exim can be configured to add them to the final delivery of messages. (See the
31871 generic &%envelope_to_add%& transport option.) They should not be present in
31872 messages in transit. If the &%envelope_to_remove%& configuration option is set
31873 (the default), Exim removes &'Envelope-to:'& header lines from incoming
31874 messages.
31875
31876
31877 .section "The From: header line" "SECTthefrohea"
31878 .cindex "&'From:'& header line"
31879 .cindex "Sendmail compatibility" "&""From""& line"
31880 .cindex "message" "submission"
31881 .cindex "submission mode"
31882 If a submission-mode message does not contain a &'From:'& header line, Exim
31883 adds one if either of the following conditions is true:
31884
31885 .ilist
31886 The envelope sender address is not empty (that is, this is not a bounce
31887 message). The added header line copies the envelope sender address.
31888 .next
31889 .vindex "&$authenticated_id$&"
31890 The SMTP session is authenticated and &$authenticated_id$& is not empty.
31891 .olist
31892 .vindex "&$qualify_domain$&"
31893 If no domain is specified by the submission control, the local part is
31894 &$authenticated_id$& and the domain is &$qualify_domain$&.
31895 .next
31896 If a non-empty domain is specified by the submission control, the local
31897 part is &$authenticated_id$&, and the domain is the specified domain.
31898 .next
31899 If an empty domain is specified by the submission control,
31900 &$authenticated_id$& is assumed to be the complete address.
31901 .endlist
31902 .endlist
31903
31904 A non-empty envelope sender takes precedence.
31905
31906 If a locally-generated incoming message does not contain a &'From:'& header
31907 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
31908 containing the sender's address. The calling user's login name and full name
31909 are used to construct the address, as described in section &<<SECTconstr>>&.
31910 They are obtained from the password data by calling &[getpwuid()]& (but see the
31911 &%unknown_login%& configuration option). The address is qualified with
31912 &%qualify_domain%&.
31913
31914 For compatibility with Sendmail, if an incoming, non-SMTP message has a
31915 &'From:'& header line containing just the unqualified login name of the calling
31916 user, this is replaced by an address containing the user's login name and full
31917 name as described in section &<<SECTconstr>>&.
31918
31919
31920 .section "The Message-ID: header line" "SECID226"
31921 .cindex "&'Message-ID:'& header line"
31922 .cindex "message" "submission"
31923 .oindex "&%message_id_header_text%&"
31924 If a locally-generated or submission-mode incoming message does not contain a
31925 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
31926 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
31927 to the message. If there are any &'Resent-:'& headers in the message, it
31928 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
31929 message id, preceded by the letter E to ensure it starts with a letter, and
31930 followed by @ and the primary host name. Additional information can be included
31931 in this header line by setting the &%message_id_header_text%& and/or
31932 &%message_id_header_domain%& options.
31933
31934
31935 .section "The Received: header line" "SECID227"
31936 .cindex "&'Received:'& header line"
31937 A &'Received:'& header line is added at the start of every message. The
31938 contents are defined by the &%received_header_text%& configuration option, and
31939 Exim automatically adds a semicolon and a timestamp to the configured string.
31940
31941 The &'Received:'& header is generated as soon as the message's header lines
31942 have been received. At this stage, the timestamp in the &'Received:'& header
31943 line is the time that the message started to be received. This is the value
31944 that is seen by the DATA ACL and by the &[local_scan()]& function.
31945
31946 Once a message is accepted, the timestamp in the &'Received:'& header line is
31947 changed to the time of acceptance, which is (apart from a small delay while the
31948 -H spool file is written) the earliest time at which delivery could start.
31949
31950
31951 .section "The References: header line" "SECID228"
31952 .cindex "&'References:'& header line"
31953 Messages created by the &(autoreply)& transport include a &'References:'&
31954 header line. This is constructed according to the rules that are described in
31955 section 3.64 of RFC 2822 (which states that replies should contain such a
31956 header line), and section 3.14 of RFC 3834 (which states that automatic
31957 responses are not different in this respect). However, because some mail
31958 processing software does not cope well with very long header lines, no more
31959 than 12 message IDs are copied from the &'References:'& header line in the
31960 incoming message. If there are more than 12, the first one and then the final
31961 11 are copied, before adding the message ID of the incoming message.
31962
31963
31964
31965 .section "The Return-path: header line" "SECID229"
31966 .cindex "&'Return-path:'& header line"
31967 .oindex "&%return_path_remove%&"
31968 &'Return-path:'& header lines are defined as something an MTA may insert when
31969 it does the final delivery of messages. (See the generic &%return_path_add%&
31970 transport option.) Therefore, they should not be present in messages in
31971 transit. If the &%return_path_remove%& configuration option is set (the
31972 default), Exim removes &'Return-path:'& header lines from incoming messages.
31973
31974
31975
31976 .section "The Sender: header line" "SECTthesenhea"
31977 .cindex "&'Sender:'& header line"
31978 .cindex "message" "submission"
31979 For a locally-originated message from an untrusted user, Exim may remove an
31980 existing &'Sender:'& header line, and it may add a new one. You can modify
31981 these actions by setting the &%local_sender_retain%& option true, the
31982 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
31983 control setting.
31984
31985 When a local message is received from an untrusted user and
31986 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
31987 control has not been set, a check is made to see if the address given in the
31988 &'From:'& header line is the correct (local) sender of the message. The address
31989 that is expected has the login name as the local part and the value of
31990 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
31991 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
31992 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
31993 line is added to the message.
31994
31995 If you set &%local_from_check%& false, this checking does not occur. However,
31996 the removal of an existing &'Sender:'& line still happens, unless you also set
31997 &%local_sender_retain%& to be true. It is not possible to set both of these
31998 options true at the same time.
31999
32000 .cindex "submission mode"
32001 By default, no processing of &'Sender:'& header lines is done for messages
32002 received over TCP/IP or for messages submitted by trusted users. However, when
32003 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
32004 not specified on the submission control, the following processing takes place:
32005
32006 .vindex "&$authenticated_id$&"
32007 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
32008 authenticated, and &$authenticated_id$& is not empty, a sender address is
32009 created as follows:
32010
32011 .ilist
32012 .vindex "&$qualify_domain$&"
32013 If no domain is specified by the submission control, the local part is
32014 &$authenticated_id$& and the domain is &$qualify_domain$&.
32015 .next
32016 If a non-empty domain is specified by the submission control, the local part
32017 is &$authenticated_id$&, and the domain is the specified domain.
32018 .next
32019 If an empty domain is specified by the submission control,
32020 &$authenticated_id$& is assumed to be the complete address.
32021 .endlist
32022
32023 This address is compared with the address in the &'From:'& header line. If they
32024 are different, a &'Sender:'& header line containing the created address is
32025 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
32026 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
32027
32028 .cindex "return path" "created from &'Sender:'&"
32029 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
32030 the message (the envelope sender address) is changed to be the same address,
32031 except in the case of submission mode when &%sender_retain%& is specified.
32032
32033
32034
32035 .section "Adding and removing header lines in routers and transports" &&&
32036 "SECTheadersaddrem"
32037 .cindex "header lines" "adding; in router or transport"
32038 .cindex "header lines" "removing; in router or transport"
32039 When a message is delivered, the addition and removal of header lines can be
32040 specified in a system filter, or on any of the routers and transports that
32041 process the message. Section &<<SECTaddremheasys>>& contains details about
32042 modifying headers in a system filter. Header lines can also be added in an ACL
32043 as a message is received (see section &<<SECTaddheadacl>>&).
32044
32045 In contrast to what happens in a system filter, header modifications that are
32046 specified on routers and transports apply only to the particular recipient
32047 addresses that are being processed by those routers and transports. These
32048 changes do not actually take place until a copy of the message is being
32049 transported. Therefore, they do not affect the basic set of header lines, and
32050 they do not affect the values of the variables that refer to header lines.
32051
32052 &*Note*&: In particular, this means that any expansions in the configuration of
32053 the transport cannot refer to the modified header lines, because such
32054 expansions all occur before the message is actually transported.
32055
32056 For both routers and transports, the argument of a &%headers_add%&
32057 option must be in the form of one or more RFC 2822 header lines, separated by
32058 newlines (coded as &"\n"&). For example:
32059 .code
32060 headers_add = X-added-header: added by $primary_hostname\n\
32061 X-added-second: another added header line
32062 .endd
32063 Exim does not check the syntax of these added header lines.
32064
32065 Multiple &%headers_add%& options for a single router or transport can be
32066 specified; the values will append to a single list of header lines.
32067 Each header-line is separately expanded.
32068
32069 The argument of a &%headers_remove%& option must consist of a colon-separated
32070 list of header names. This is confusing, because header names themselves are
32071 often terminated by colons. In this case, the colons are the list separators,
32072 not part of the names. For example:
32073 .code
32074 headers_remove = return-receipt-to:acknowledge-to
32075 .endd
32076
32077 Multiple &%headers_remove%& options for a single router or transport can be
32078 specified; the arguments will append to a single header-names list.
32079 Each item is separately expanded.
32080
32081 When &%headers_add%& or &%headers_remove%& is specified on a router,
32082 items are expanded at routing time,
32083 and then associated with all addresses that are
32084 accepted by that router, and also with any new addresses that it generates. If
32085 an address passes through several routers as a result of aliasing or
32086 forwarding, the changes are cumulative.
32087
32088 .oindex "&%unseen%&"
32089 However, this does not apply to multiple routers that result from the use of
32090 the &%unseen%& option. Any header modifications that were specified by the
32091 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
32092
32093 Addresses that end up with different &%headers_add%& or &%headers_remove%&
32094 settings cannot be delivered together in a batch, so a transport is always
32095 dealing with a set of addresses that have the same header-processing
32096 requirements.
32097
32098 The transport starts by writing the original set of header lines that arrived
32099 with the message, possibly modified by the system filter. As it writes out
32100 these lines, it consults the list of header names that were attached to the
32101 recipient address(es) by &%headers_remove%& options in routers, and it also
32102 consults the transport's own &%headers_remove%& option. Header lines whose
32103 names are on either of these lists are not written out. If there are multiple
32104 instances of any listed header, they are all skipped.
32105
32106 After the remaining original header lines have been written, new header
32107 lines that were specified by routers' &%headers_add%& options are written, in
32108 the order in which they were attached to the address. These are followed by any
32109 header lines specified by the transport's &%headers_add%& option.
32110
32111 This way of handling header line modifications in routers and transports has
32112 the following consequences:
32113
32114 .ilist
32115 The original set of header lines, possibly modified by the system filter,
32116 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
32117 to it, at all times.
32118 .next
32119 Header lines that are added by a router's
32120 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
32121 expansion syntax in subsequent routers or the transport.
32122 .next
32123 Conversely, header lines that are specified for removal by &%headers_remove%&
32124 in a router remain visible to subsequent routers and the transport.
32125 .next
32126 Headers added to an address by &%headers_add%& in a router cannot be removed by
32127 a later router or by a transport.
32128 .next
32129 An added header can refer to the contents of an original header that is to be
32130 removed, even it has the same name as the added header. For example:
32131 .code
32132 headers_remove = subject
32133 headers_add = Subject: new subject (was: $h_subject:)
32134 .endd
32135 .endlist
32136
32137 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
32138 for a &(redirect)& router that has the &%one_time%& option set.
32139
32140
32141
32142
32143
32144 .section "Constructed addresses" "SECTconstr"
32145 .cindex "address" "constructed"
32146 .cindex "constructed address"
32147 When Exim constructs a sender address for a locally-generated message, it uses
32148 the form
32149 .display
32150 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
32151 .endd
32152 For example:
32153 .code
32154 Zaphod Beeblebrox <zaphod@end.univ.example>
32155 .endd
32156 The user name is obtained from the &%-F%& command line option if set, or
32157 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
32158 &"gecos"& field from the password entry. If the &"gecos"& field contains an
32159 ampersand character, this is replaced by the login name with the first letter
32160 upper cased, as is conventional in a number of operating systems. See the
32161 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
32162 The &%unknown_username%& option can be used to specify user names in cases when
32163 there is no password file entry.
32164
32165 .cindex "RFC 2047"
32166 In all cases, the user name is made to conform to RFC 2822 by quoting all or
32167 parts of it if necessary. In addition, if it contains any non-printing
32168 characters, it is encoded as described in RFC 2047, which defines a way of
32169 including non-ASCII characters in header lines. The value of the
32170 &%headers_charset%& option specifies the name of the encoding that is used (the
32171 characters are assumed to be in this encoding). The setting of
32172 &%print_topbitchars%& controls whether characters with the top bit set (that
32173 is, with codes greater than 127) count as printing characters or not.
32174
32175
32176
32177 .section "Case of local parts" "SECID230"
32178 .cindex "case of local parts"
32179 .cindex "local part" "case of"
32180 RFC 2822 states that the case of letters in the local parts of addresses cannot
32181 be assumed to be non-significant. Exim preserves the case of local parts of
32182 addresses, but by default it uses a lower-cased form when it is routing,
32183 because on most Unix systems, usernames are in lower case and case-insensitive
32184 routing is required. However, any particular router can be made to use the
32185 original case for local parts by setting the &%caseful_local_part%& generic
32186 router option.
32187
32188 .cindex "mixed-case login names"
32189 If you must have mixed-case user names on your system, the best way to proceed,
32190 assuming you want case-independent handling of incoming email, is to set up
32191 your first router to convert incoming local parts in your domains to the
32192 correct case by means of a file lookup. For example:
32193 .code
32194 correct_case:
32195 driver = redirect
32196 domains = +local_domains
32197 data = ${lookup{$local_part}cdb\
32198 {/etc/usercased.cdb}{$value}fail}\
32199 @$domain
32200 .endd
32201 For this router, the local part is forced to lower case by the default action
32202 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
32203 up a new local part in the correct case. If you then set &%caseful_local_part%&
32204 on any subsequent routers which process your domains, they will operate on
32205 local parts with the correct case in a case-sensitive manner.
32206
32207
32208
32209 .section "Dots in local parts" "SECID231"
32210 .cindex "dot" "in local part"
32211 .cindex "local part" "dots in"
32212 RFC 2822 forbids empty components in local parts. That is, an unquoted local
32213 part may not begin or end with a dot, nor have two consecutive dots in the
32214 middle. However, it seems that many MTAs do not enforce this, so Exim permits
32215 empty components for compatibility.
32216
32217
32218
32219 .section "Rewriting addresses" "SECID232"
32220 .cindex "rewriting" "addresses"
32221 Rewriting of sender and recipient addresses, and addresses in headers, can
32222 happen automatically, or as the result of configuration options, as described
32223 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
32224 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
32225
32226 Automatic rewriting includes qualification, as mentioned above. The other case
32227 in which it can happen is when an incomplete non-local domain is given. The
32228 routing process may cause this to be expanded into the full domain name. For
32229 example, a header such as
32230 .code
32231 To: hare@teaparty
32232 .endd
32233 might get rewritten as
32234 .code
32235 To: hare@teaparty.wonderland.fict.example
32236 .endd
32237 Rewriting as a result of routing is the one kind of message processing that
32238 does not happen at input time, as it cannot be done until the address has
32239 been routed.
32240
32241 Strictly, one should not do &'any'& deliveries of a message until all its
32242 addresses have been routed, in case any of the headers get changed as a
32243 result of routing. However, doing this in practice would hold up many
32244 deliveries for unreasonable amounts of time, just because one address could not
32245 immediately be routed. Exim therefore does not delay other deliveries when
32246 routing of one or more addresses is deferred.
32247 .ecindex IIDmesproc
32248
32249
32250
32251 . ////////////////////////////////////////////////////////////////////////////
32252 . ////////////////////////////////////////////////////////////////////////////
32253
32254 .chapter "SMTP processing" "CHAPSMTP"
32255 .scindex IIDsmtpproc1 "SMTP" "processing details"
32256 .scindex IIDsmtpproc2 "LMTP" "processing details"
32257 Exim supports a number of different ways of using the SMTP protocol, and its
32258 LMTP variant, which is an interactive protocol for transferring messages into a
32259 closed mail store application. This chapter contains details of how SMTP is
32260 processed. For incoming mail, the following are available:
32261
32262 .ilist
32263 SMTP over TCP/IP (Exim daemon or &'inetd'&);
32264 .next
32265 SMTP over the standard input and output (the &%-bs%& option);
32266 .next
32267 Batched SMTP on the standard input (the &%-bS%& option).
32268 .endlist
32269
32270 For mail delivery, the following are available:
32271
32272 .ilist
32273 SMTP over TCP/IP (the &(smtp)& transport);
32274 .next
32275 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
32276 &"lmtp"&);
32277 .next
32278 LMTP over a pipe to a process running in the local host (the &(lmtp)&
32279 transport);
32280 .next
32281 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
32282 the &%use_bsmtp%& option set).
32283 .endlist
32284
32285 &'Batched SMTP'& is the name for a process in which batches of messages are
32286 stored in or read from files (or pipes), in a format in which SMTP commands are
32287 used to contain the envelope information.
32288
32289
32290
32291 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
32292 .cindex "SMTP" "outgoing over TCP/IP"
32293 .cindex "outgoing SMTP over TCP/IP"
32294 .cindex "LMTP" "over TCP/IP"
32295 .cindex "outgoing LMTP over TCP/IP"
32296 .cindex "EHLO"
32297 .cindex "HELO"
32298 .cindex "SIZE option on MAIL command"
32299 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
32300 The &%protocol%& option selects which protocol is to be used, but the actual
32301 processing is the same in both cases.
32302
32303 If, in response to its EHLO command, Exim is told that the SIZE
32304 parameter is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
32305 command. The value of <&'n'&> is the message size plus the value of the
32306 &%size_addition%& option (default 1024) to allow for additions to the message
32307 such as per-transport header lines, or changes made in a
32308 .cindex "transport" "filter"
32309 .cindex "filter" "transport filter"
32310 transport filter. If &%size_addition%& is set negative, the use of SIZE is
32311 suppressed.
32312
32313 If the remote server advertises support for PIPELINING, Exim uses the
32314 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
32315 required for the transaction.
32316
32317 If the remote server advertises support for the STARTTLS command, and Exim
32318 was built to support TLS encryption, it tries to start a TLS session unless the
32319 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
32320 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
32321 is called for verification.
32322
32323 If the remote server advertises support for the AUTH command, Exim scans
32324 the authenticators configuration for any suitable client settings, as described
32325 in chapter &<<CHAPSMTPAUTH>>&.
32326
32327 .cindex "carriage return"
32328 .cindex "linefeed"
32329 Responses from the remote host are supposed to be terminated by CR followed by
32330 LF. However, there are known to be hosts that do not send CR characters, so in
32331 order to be able to interwork with such hosts, Exim treats LF on its own as a
32332 line terminator.
32333
32334 If a message contains a number of different addresses, all those with the same
32335 characteristics (for example, the same envelope sender) that resolve to the
32336 same set of hosts, in the same order, are sent in a single SMTP transaction,
32337 even if they are for different domains, unless there are more than the setting
32338 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
32339 they are split into groups containing no more than &%max_rcpt%&s addresses
32340 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
32341 in parallel sessions. The order of hosts with identical MX values is not
32342 significant when checking whether addresses can be batched in this way.
32343
32344 When the &(smtp)& transport suffers a temporary failure that is not
32345 message-related, Exim updates its transport-specific database, which contains
32346 records indexed by host name that remember which messages are waiting for each
32347 particular host. It also updates the retry database with new retry times.
32348
32349 .cindex "hints database" "retry keys"
32350 Exim's retry hints are based on host name plus IP address, so if one address of
32351 a multi-homed host is broken, it will soon be skipped most of the time.
32352 See the next section for more detail about error handling.
32353
32354 .cindex "SMTP" "passed connection"
32355 .cindex "SMTP" "batching over TCP/IP"
32356 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
32357 looks in the hints database for the transport to see if there are any queued
32358 messages waiting for the host to which it is connected. If it finds one, it
32359 creates a new Exim process using the &%-MC%& option (which can only be used by
32360 a process running as root or the Exim user) and passes the TCP/IP socket to it
32361 so that it can deliver another message using the same socket. The new process
32362 does only those deliveries that are routed to the connected host, and may in
32363 turn pass the socket on to a third process, and so on.
32364
32365 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
32366 limit the number of messages sent down a single TCP/IP connection.
32367
32368 .cindex "asterisk" "after IP address"
32369 The second and subsequent messages delivered down an existing connection are
32370 identified in the main log by the addition of an asterisk after the closing
32371 square bracket of the IP address.
32372
32373
32374
32375
32376 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
32377 .cindex "error" "in outgoing SMTP"
32378 .cindex "SMTP" "errors in outgoing"
32379 .cindex "host" "error"
32380 Three different kinds of error are recognized for outgoing SMTP: host errors,
32381 message errors, and recipient errors.
32382
32383 .vlist
32384 .vitem "&*Host errors*&"
32385 A host error is not associated with a particular message or with a
32386 particular recipient of a message. The host errors are:
32387
32388 .ilist
32389 Connection refused or timed out,
32390 .next
32391 Any error response code on connection,
32392 .next
32393 Any error response code to EHLO or HELO,
32394 .next
32395 Loss of connection at any time, except after &"."&,
32396 .next
32397 I/O errors at any time,
32398 .next
32399 Timeouts during the session, other than in response to MAIL, RCPT or
32400 the &"."& at the end of the data.
32401 .endlist ilist
32402
32403 For a host error, a permanent error response on connection, or in response to
32404 EHLO, causes all addresses routed to the host to be failed. Any other host
32405 error causes all addresses to be deferred, and retry data to be created for the
32406 host. It is not tried again, for any message, until its retry time arrives. If
32407 the current set of addresses are not all delivered in this run (to some
32408 alternative host), the message is added to the list of those waiting for this
32409 host, so if it is still undelivered when a subsequent successful delivery is
32410 made to the host, it will be sent down the same SMTP connection.
32411
32412 .vitem "&*Message errors*&"
32413 .cindex "message" "error"
32414 A message error is associated with a particular message when sent to a
32415 particular host, but not with a particular recipient of the message. The
32416 message errors are:
32417
32418 .ilist
32419 Any error response code to MAIL, DATA, or the &"."& that terminates
32420 the data,
32421 .next
32422 Timeout after MAIL,
32423 .next
32424 Timeout or loss of connection after the &"."& that terminates the data. A
32425 timeout after the DATA command itself is treated as a host error, as is loss of
32426 connection at any other time.
32427 .endlist ilist
32428
32429 For a message error, a permanent error response (5&'xx'&) causes all addresses
32430 to be failed, and a delivery error report to be returned to the sender. A
32431 temporary error response (4&'xx'&), or one of the timeouts, causes all
32432 addresses to be deferred. Retry data is not created for the host, but instead,
32433 a retry record for the combination of host plus message id is created. The
32434 message is not added to the list of those waiting for this host. This ensures
32435 that the failing message will not be sent to this host again until the retry
32436 time arrives. However, other messages that are routed to the host are not
32437 affected, so if it is some property of the message that is causing the error,
32438 it will not stop the delivery of other mail.
32439
32440 If the remote host specified support for the SIZE parameter in its response
32441 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
32442 over-large message will cause a message error because the error arrives as a
32443 response to MAIL.
32444
32445 .vitem "&*Recipient errors*&"
32446 .cindex "recipient" "error"
32447 A recipient error is associated with a particular recipient of a message. The
32448 recipient errors are:
32449
32450 .ilist
32451 Any error response to RCPT,
32452 .next
32453 Timeout after RCPT.
32454 .endlist
32455
32456 For a recipient error, a permanent error response (5&'xx'&) causes the
32457 recipient address to be failed, and a bounce message to be returned to the
32458 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
32459 address to be deferred, and routing retry data to be created for it. This is
32460 used to delay processing of the address in subsequent queue runs, until its
32461 routing retry time arrives. This applies to all messages, but because it
32462 operates only in queue runs, one attempt will be made to deliver a new message
32463 to the failing address before the delay starts to operate. This ensures that,
32464 if the failure is really related to the message rather than the recipient
32465 (&"message too big for this recipient"& is a possible example), other messages
32466 have a chance of getting delivered. If a delivery to the address does succeed,
32467 the retry information gets cleared, so all stuck messages get tried again, and
32468 the retry clock is reset.
32469
32470 The message is not added to the list of those waiting for this host. Use of the
32471 host for other messages is unaffected, and except in the case of a timeout,
32472 other recipients are processed independently, and may be successfully delivered
32473 in the current SMTP session. After a timeout it is of course impossible to
32474 proceed with the session, so all addresses get deferred. However, those other
32475 than the one that failed do not suffer any subsequent retry delays. Therefore,
32476 if one recipient is causing trouble, the others have a chance of getting
32477 through when a subsequent delivery attempt occurs before the failing
32478 recipient's retry time.
32479 .endlist
32480
32481 In all cases, if there are other hosts (or IP addresses) available for the
32482 current set of addresses (for example, from multiple MX records), they are
32483 tried in this run for any undelivered addresses, subject of course to their
32484 own retry data. In other words, recipient error retry data does not take effect
32485 until the next delivery attempt.
32486
32487 Some hosts have been observed to give temporary error responses to every
32488 MAIL command at certain times (&"insufficient space"& has been seen). It
32489 would be nice if such circumstances could be recognized, and defer data for the
32490 host itself created, but this is not possible within the current Exim design.
32491 What actually happens is that retry data for every (host, message) combination
32492 is created.
32493
32494 The reason that timeouts after MAIL and RCPT are treated specially is that
32495 these can sometimes arise as a result of the remote host's verification
32496 procedures. Exim makes this assumption, and treats them as if a temporary error
32497 response had been received. A timeout after &"."& is treated specially because
32498 it is known that some broken implementations fail to recognize the end of the
32499 message if the last character of the last line is a binary zero. Thus, it is
32500 helpful to treat this case as a message error.
32501
32502 Timeouts at other times are treated as host errors, assuming a problem with the
32503 host, or the connection to it. If a timeout after MAIL, RCPT,
32504 or &"."& is really a connection problem, the assumption is that at the next try
32505 the timeout is likely to occur at some other point in the dialogue, causing it
32506 then to be treated as a host error.
32507
32508 There is experimental evidence that some MTAs drop the connection after the
32509 terminating &"."& if they do not like the contents of the message for some
32510 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
32511 should be given. That is why Exim treats this case as a message rather than a
32512 host error, in order not to delay other messages to the same host.
32513
32514
32515
32516
32517 .section "Incoming SMTP messages over TCP/IP" "SECID233"
32518 .cindex "SMTP" "incoming over TCP/IP"
32519 .cindex "incoming SMTP over TCP/IP"
32520 .cindex "inetd"
32521 .cindex "daemon"
32522 Incoming SMTP messages can be accepted in one of two ways: by running a
32523 listening daemon, or by using &'inetd'&. In the latter case, the entry in
32524 &_/etc/inetd.conf_& should be like this:
32525 .code
32526 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
32527 .endd
32528 Exim distinguishes between this case and the case of a locally running user
32529 agent using the &%-bs%& option by checking whether or not the standard input is
32530 a socket. When it is, either the port must be privileged (less than 1024), or
32531 the caller must be root or the Exim user. If any other user passes a socket
32532 with an unprivileged port number, Exim prints a message on the standard error
32533 stream and exits with an error code.
32534
32535 By default, Exim does not make a log entry when a remote host connects or
32536 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
32537 unexpected. It can be made to write such log entries by setting the
32538 &%smtp_connection%& log selector.
32539
32540 .cindex "carriage return"
32541 .cindex "linefeed"
32542 Commands from the remote host are supposed to be terminated by CR followed by
32543 LF. However, there are known to be hosts that do not send CR characters. In
32544 order to be able to interwork with such hosts, Exim treats LF on its own as a
32545 line terminator.
32546 Furthermore, because common code is used for receiving messages from all
32547 sources, a CR on its own is also interpreted as a line terminator. However, the
32548 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
32549
32550 .cindex "EHLO" "invalid data"
32551 .cindex "HELO" "invalid data"
32552 One area that sometimes gives rise to problems concerns the EHLO or
32553 HELO commands. Some clients send syntactically invalid versions of these
32554 commands, which Exim rejects by default. (This is nothing to do with verifying
32555 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
32556 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
32557 match the broken hosts that send invalid commands.
32558
32559 .cindex "SIZE option on MAIL command"
32560 .cindex "MAIL" "SIZE option"
32561 The amount of disk space available is checked whenever SIZE is received on
32562 a MAIL command, independently of whether &%message_size_limit%& or
32563 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
32564 false. A temporary error is given if there is not enough space. If
32565 &%check_spool_space%& is set, the check is for that amount of space plus the
32566 value given with SIZE, that is, it checks that the addition of the incoming
32567 message will not reduce the space below the threshold.
32568
32569 When a message is successfully received, Exim includes the local message id in
32570 its response to the final &"."& that terminates the data. If the remote host
32571 logs this text it can help with tracing what has happened to a message.
32572
32573 The Exim daemon can limit the number of simultaneous incoming connections it is
32574 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
32575 number of simultaneous incoming connections from a single remote host (see the
32576 &%smtp_accept_max_per_host%& option). Additional connection attempts are
32577 rejected using the SMTP temporary error code 421.
32578
32579 The Exim daemon does not rely on the SIGCHLD signal to detect when a
32580 subprocess has finished, as this can get lost at busy times. Instead, it looks
32581 for completed subprocesses every time it wakes up. Provided there are other
32582 things happening (new incoming calls, starts of queue runs), completed
32583 processes will be noticed and tidied away. On very quiet systems you may
32584 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
32585 it will be noticed when the daemon next wakes up.
32586
32587 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
32588 and can also be set up to reject SMTP calls from non-reserved hosts at times of
32589 high system load &-- for details see the &%smtp_accept_reserve%&,
32590 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
32591 applies in both the daemon and &'inetd'& cases.
32592
32593 Exim normally starts a delivery process for each message received, though this
32594 can be varied by means of the &%-odq%& command line option and the
32595 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
32596 number of simultaneously running delivery processes started in this way from
32597 SMTP input can be limited by the &%smtp_accept_queue%& and
32598 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
32599 subsequently received messages are just put on the input queue without starting
32600 a delivery process.
32601
32602 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
32603 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
32604 started up from the &'inetd'& daemon, because in that case each connection is
32605 handled by an entirely independent Exim process. Control by load average is,
32606 however, available with &'inetd'&.
32607
32608 Exim can be configured to verify addresses in incoming SMTP commands as they
32609 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
32610 to rewrite addresses at this time &-- before any syntax checking is done. See
32611 section &<<SECTrewriteS>>&.
32612
32613 Exim can also be configured to limit the rate at which a client host submits
32614 MAIL and RCPT commands in a single SMTP session. See the
32615 &%smtp_ratelimit_hosts%& option.
32616
32617
32618
32619 .section "Unrecognized SMTP commands" "SECID234"
32620 .cindex "SMTP" "unrecognized commands"
32621 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
32622 commands during a single SMTP connection, it drops the connection after sending
32623 the error response to the last command. The default value for
32624 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
32625 abuse that subvert web servers into making connections to SMTP ports; in these
32626 circumstances, a number of non-SMTP lines are sent first.
32627
32628
32629 .section "Syntax and protocol errors in SMTP commands" "SECID235"
32630 .cindex "SMTP" "syntax errors"
32631 .cindex "SMTP" "protocol errors"
32632 A syntax error is detected if an SMTP command is recognized, but there is
32633 something syntactically wrong with its data, for example, a malformed email
32634 address in a RCPT command. Protocol errors include invalid command
32635 sequencing such as RCPT before MAIL. If Exim receives more than
32636 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
32637 drops the connection after sending the error response to the last command. The
32638 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
32639 broken clients that loop sending bad commands (yes, it has been seen).
32640
32641
32642
32643 .section "Use of non-mail SMTP commands" "SECID236"
32644 .cindex "SMTP" "non-mail commands"
32645 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
32646 DATA. Exim counts such commands, and drops the connection if there are too
32647 many of them in a single SMTP session. This action catches some
32648 denial-of-service attempts and things like repeated failing AUTHs, or a mad
32649 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
32650 defines what &"too many"& means. Its default value is 10.
32651
32652 When a new message is expected, one occurrence of RSET is not counted. This
32653 allows a client to send one RSET between messages (this is not necessary,
32654 but some clients do it). Exim also allows one uncounted occurrence of HELO
32655 or EHLO, and one occurrence of STARTTLS between messages. After
32656 starting up a TLS session, another EHLO is expected, and so it too is not
32657 counted.
32658
32659 The first occurrence of AUTH in a connection, or immediately following
32660 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
32661 RCPT, DATA, and QUIT are counted.
32662
32663 You can control which hosts are subject to the limit set by
32664 &%smtp_accept_max_nonmail%& by setting
32665 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
32666 the limit apply to all hosts. This option means that you can exclude any
32667 specific badly-behaved hosts that you have to live with.
32668
32669
32670
32671
32672 .section "The VRFY and EXPN commands" "SECID237"
32673 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
32674 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
32675 appropriate) in order to decide whether the command should be accepted or not.
32676 If no ACL is defined, the command is rejected.
32677
32678 .cindex "VRFY" "processing"
32679 When VRFY is accepted, it runs exactly the same code as when Exim is
32680 called with the &%-bv%& option.
32681
32682 .cindex "EXPN" "processing"
32683 When EXPN is accepted, a single-level expansion of the address is done.
32684 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
32685 than a verification (the &%-bv%& option). If an unqualified local part is given
32686 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
32687 of VRFY and EXPN commands are logged on the main and reject logs, and
32688 VRFY verification failures are logged on the main log for consistency with
32689 RCPT failures.
32690
32691
32692
32693 .section "The ETRN command" "SECTETRN"
32694 .cindex "ETRN" "processing"
32695 RFC 1985 describes an SMTP command called ETRN that is designed to
32696 overcome the security problems of the TURN command (which has fallen into
32697 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
32698 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
32699 should be accepted or not. If no ACL is defined, the command is rejected.
32700
32701 The ETRN command is concerned with &"releasing"& messages that are awaiting
32702 delivery to certain hosts. As Exim does not organize its message queue by host,
32703 the only form of ETRN that is supported by default is the one where the
32704 text starts with the &"#"& prefix, in which case the remainder of the text is
32705 specific to the SMTP server. A valid ETRN command causes a run of Exim with
32706 the &%-R%& option to happen, with the remainder of the ETRN text as its
32707 argument. For example,
32708 .code
32709 ETRN #brigadoon
32710 .endd
32711 runs the command
32712 .code
32713 exim -R brigadoon
32714 .endd
32715 which causes a delivery attempt on all messages with undelivered addresses
32716 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
32717 default), Exim prevents the simultaneous execution of more than one queue run
32718 for the same argument string as a result of an ETRN command. This stops
32719 a misbehaving client from starting more than one queue runner at once.
32720
32721 .cindex "hints database" "ETRN serialization"
32722 Exim implements the serialization by means of a hints database in which a
32723 record is written whenever a process is started by ETRN, and deleted when
32724 the process completes. However, Exim does not keep the SMTP session waiting for
32725 the ETRN process to complete. Once ETRN is accepted, the client is sent
32726 a &"success"& return code. Obviously there is scope for hints records to get
32727 left lying around if there is a system or program crash. To guard against this,
32728 Exim ignores any records that are more than six hours old.
32729
32730 .oindex "&%smtp_etrn_command%&"
32731 For more control over what ETRN does, the &%smtp_etrn_command%& option can
32732 used. This specifies a command that is run whenever ETRN is received,
32733 whatever the form of its argument. For
32734 example:
32735 .code
32736 smtp_etrn_command = /etc/etrn_command $domain \
32737 $sender_host_address
32738 .endd
32739 .vindex "&$domain$&"
32740 The string is split up into arguments which are independently expanded. The
32741 expansion variable &$domain$& is set to the argument of the ETRN command,
32742 and no syntax checking is done on the contents of this argument. Exim does not
32743 wait for the command to complete, so its status code is not checked. Exim runs
32744 under its own uid and gid when receiving incoming SMTP, so it is not possible
32745 for it to change them before running the command.
32746
32747
32748
32749 .section "Incoming local SMTP" "SECID238"
32750 .cindex "SMTP" "local incoming"
32751 Some user agents use SMTP to pass messages to their local MTA using the
32752 standard input and output, as opposed to passing the envelope on the command
32753 line and writing the message to the standard input. This is supported by the
32754 &%-bs%& option. This form of SMTP is handled in the same way as incoming
32755 messages over TCP/IP (including the use of ACLs), except that the envelope
32756 sender given in a MAIL command is ignored unless the caller is trusted. In
32757 an ACL you can detect this form of SMTP input by testing for an empty host
32758 identification. It is common to have this as the first line in the ACL that
32759 runs for RCPT commands:
32760 .code
32761 accept hosts = :
32762 .endd
32763 This accepts SMTP messages from local processes without doing any other tests.
32764
32765
32766
32767 .section "Outgoing batched SMTP" "SECTbatchSMTP"
32768 .cindex "SMTP" "batched outgoing"
32769 .cindex "batched SMTP output"
32770 Both the &(appendfile)& and &(pipe)& transports can be used for handling
32771 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
32772 be output in BSMTP format. No SMTP responses are possible for this form of
32773 delivery. All it is doing is using SMTP commands as a way of transmitting the
32774 envelope along with the message.
32775
32776 The message is written to the file or pipe preceded by the SMTP commands
32777 MAIL and RCPT, and followed by a line containing a single dot. Lines in
32778 the message that start with a dot have an extra dot added. The SMTP command
32779 HELO is not normally used. If it is required, the &%message_prefix%& option
32780 can be used to specify it.
32781
32782 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
32783 one recipient address at a time by default. However, you can arrange for them
32784 to handle several addresses at once by setting the &%batch_max%& option. When
32785 this is done for BSMTP, messages may contain multiple RCPT commands. See
32786 chapter &<<CHAPbatching>>& for more details.
32787
32788 .vindex "&$host$&"
32789 When one or more addresses are routed to a BSMTP transport by a router that
32790 sets up a host list, the name of the first host on the list is available to the
32791 transport in the variable &$host$&. Here is an example of such a transport and
32792 router:
32793 .code
32794 begin routers
32795 route_append:
32796 driver = manualroute
32797 transport = smtp_appendfile
32798 route_list = domain.example batch.host.example
32799
32800 begin transports
32801 smtp_appendfile:
32802 driver = appendfile
32803 directory = /var/bsmtp/$host
32804 batch_max = 1000
32805 use_bsmtp
32806 user = exim
32807 .endd
32808 This causes messages addressed to &'domain.example'& to be written in BSMTP
32809 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
32810 message (unless there are more than 1000 recipients).
32811
32812
32813
32814 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
32815 .cindex "SMTP" "batched incoming"
32816 .cindex "batched SMTP input"
32817 The &%-bS%& command line option causes Exim to accept one or more messages by
32818 reading SMTP on the standard input, but to generate no responses. If the caller
32819 is trusted, the senders in the MAIL commands are believed; otherwise the
32820 sender is always the caller of Exim. Unqualified senders and receivers are not
32821 rejected (there seems little point) but instead just get qualified. HELO
32822 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
32823 as NOOP; QUIT quits.
32824
32825 Minimal policy checking is done for BSMTP input. Only the non-SMTP
32826 ACL is run in the same way as for non-SMTP local input.
32827
32828 If an error is detected while reading a message, including a missing &"."& at
32829 the end, Exim gives up immediately. It writes details of the error to the
32830 standard output in a stylized way that the calling program should be able to
32831 make some use of automatically, for example:
32832 .code
32833 554 Unexpected end of file
32834 Transaction started in line 10
32835 Error detected in line 14
32836 .endd
32837 It writes a more verbose version, for human consumption, to the standard error
32838 file, for example:
32839 .code
32840 An error was detected while processing a file of BSMTP input.
32841 The error message was:
32842
32843 501 '>' missing at end of address
32844
32845 The SMTP transaction started in line 10.
32846 The error was detected in line 12.
32847 The SMTP command at fault was:
32848
32849 rcpt to:<malformed@in.com.plete
32850
32851 1 previous message was successfully processed.
32852 The rest of the batch was abandoned.
32853 .endd
32854 The return code from Exim is zero only if there were no errors. It is 1 if some
32855 messages were accepted before an error was detected, and 2 if no messages were
32856 accepted.
32857 .ecindex IIDsmtpproc1
32858 .ecindex IIDsmtpproc2
32859
32860
32861
32862 . ////////////////////////////////////////////////////////////////////////////
32863 . ////////////////////////////////////////////////////////////////////////////
32864
32865 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
32866 "Customizing messages"
32867 When a message fails to be delivered, or remains on the queue for more than a
32868 configured amount of time, Exim sends a message to the original sender, or
32869 to an alternative configured address. The text of these messages is built into
32870 the code of Exim, but it is possible to change it, either by adding a single
32871 string, or by replacing each of the paragraphs by text supplied in a file.
32872
32873 The &'From:'& and &'To:'& header lines are automatically generated; you can
32874 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
32875 option. Exim also adds the line
32876 .code
32877 Auto-Submitted: auto-generated
32878 .endd
32879 to all warning and bounce messages,
32880
32881
32882 .section "Customizing bounce messages" "SECID239"
32883 .cindex "customizing" "bounce message"
32884 .cindex "bounce message" "customizing"
32885 If &%bounce_message_text%& is set, its contents are included in the default
32886 message immediately after &"This message was created automatically by mail
32887 delivery software."& The string is not expanded. It is not used if
32888 &%bounce_message_file%& is set.
32889
32890 When &%bounce_message_file%& is set, it must point to a template file for
32891 constructing error messages. The file consists of a series of text items,
32892 separated by lines consisting of exactly four asterisks. If the file cannot be
32893 opened, default text is used and a message is written to the main and panic
32894 logs. If any text item in the file is empty, default text is used for that
32895 item.
32896
32897 .vindex "&$bounce_recipient$&"
32898 .vindex "&$bounce_return_size_limit$&"
32899 Each item of text that is read from the file is expanded, and there are two
32900 expansion variables which can be of use here: &$bounce_recipient$& is set to
32901 the recipient of an error message while it is being created, and
32902 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
32903 option, rounded to a whole number.
32904
32905 The items must appear in the file in the following order:
32906
32907 .ilist
32908 The first item is included in the headers, and should include at least a
32909 &'Subject:'& header. Exim does not check the syntax of these headers.
32910 .next
32911 The second item forms the start of the error message. After it, Exim lists the
32912 failing addresses with their error messages.
32913 .next
32914 The third item is used to introduce any text from pipe transports that is to be
32915 returned to the sender. It is omitted if there is no such text.
32916 .next
32917 The fourth item is used to introduce the copy of the message that is returned
32918 as part of the error report.
32919 .next
32920 The fifth item is added after the fourth one if the returned message is
32921 truncated because it is bigger than &%return_size_limit%&.
32922 .next
32923 The sixth item is added after the copy of the original message.
32924 .endlist
32925
32926 The default state (&%bounce_message_file%& unset) is equivalent to the
32927 following file, in which the sixth item is empty. The &'Subject:'& and some
32928 other lines have been split in order to fit them on the page:
32929 .code
32930 Subject: Mail delivery failed
32931 ${if eq{$sender_address}{$bounce_recipient}
32932 {: returning message to sender}}
32933 ****
32934 This message was created automatically by mail delivery software.
32935
32936 A message ${if eq{$sender_address}{$bounce_recipient}
32937 {that you sent }{sent by
32938
32939 <$sender_address>
32940
32941 }}could not be delivered to all of its recipients.
32942 This is a permanent error. The following address(es) failed:
32943 ****
32944 The following text was generated during the delivery attempt(s):
32945 ****
32946 ------ This is a copy of the message, including all the headers.
32947 ------
32948 ****
32949 ------ The body of the message is $message_size characters long;
32950 only the first
32951 ------ $bounce_return_size_limit or so are included here.
32952 ****
32953 .endd
32954 .section "Customizing warning messages" "SECTcustwarn"
32955 .cindex "customizing" "warning message"
32956 .cindex "warning of delay" "customizing the message"
32957 The option &%warn_message_file%& can be pointed at a template file for use when
32958 warnings about message delays are created. In this case there are only three
32959 text sections:
32960
32961 .ilist
32962 The first item is included in the headers, and should include at least a
32963 &'Subject:'& header. Exim does not check the syntax of these headers.
32964 .next
32965 The second item forms the start of the warning message. After it, Exim lists
32966 the delayed addresses.
32967 .next
32968 The third item then ends the message.
32969 .endlist
32970
32971 The default state is equivalent to the following file, except that some lines
32972 have been split here, in order to fit them on the page:
32973 .code
32974 Subject: Warning: message $message_exim_id delayed
32975 $warn_message_delay
32976 ****
32977 This message was created automatically by mail delivery software.
32978
32979 A message ${if eq{$sender_address}{$warn_message_recipients}
32980 {that you sent }{sent by
32981
32982 <$sender_address>
32983
32984 }}has not been delivered to all of its recipients after
32985 more than $warn_message_delay on the queue on $primary_hostname.
32986
32987 The message identifier is: $message_exim_id
32988 The subject of the message is: $h_subject
32989 The date of the message is: $h_date
32990
32991 The following address(es) have not yet been delivered:
32992 ****
32993 No action is required on your part. Delivery attempts will
32994 continue for some time, and this warning may be repeated at
32995 intervals if the message remains undelivered. Eventually the
32996 mail delivery software will give up, and when that happens,
32997 the message will be returned to you.
32998 .endd
32999 .vindex "&$warn_message_delay$&"
33000 .vindex "&$warn_message_recipients$&"
33001 However, in the default state the subject and date lines are omitted if no
33002 appropriate headers exist. During the expansion of this file,
33003 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
33004 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
33005 of recipients for the warning message. There may be more than one if there are
33006 multiple addresses with different &%errors_to%& settings on the routers that
33007 handled them.
33008
33009
33010
33011
33012 . ////////////////////////////////////////////////////////////////////////////
33013 . ////////////////////////////////////////////////////////////////////////////
33014
33015 .chapter "Some common configuration settings" "CHAPcomconreq"
33016 This chapter discusses some configuration settings that seem to be fairly
33017 common. More examples and discussion can be found in the Exim book.
33018
33019
33020
33021 .section "Sending mail to a smart host" "SECID240"
33022 .cindex "smart host" "example router"
33023 If you want to send all mail for non-local domains to a &"smart host"&, you
33024 should replace the default &(dnslookup)& router with a router which does the
33025 routing explicitly:
33026 .code
33027 send_to_smart_host:
33028 driver = manualroute
33029 route_list = !+local_domains smart.host.name
33030 transport = remote_smtp
33031 .endd
33032 You can use the smart host's IP address instead of the name if you wish.
33033 If you are using Exim only to submit messages to a smart host, and not for
33034 receiving incoming messages, you can arrange for it to do the submission
33035 synchronously by setting the &%mua_wrapper%& option (see chapter
33036 &<<CHAPnonqueueing>>&).
33037
33038
33039
33040
33041 .section "Using Exim to handle mailing lists" "SECTmailinglists"
33042 .cindex "mailing lists"
33043 Exim can be used to run simple mailing lists, but for large and/or complicated
33044 requirements, the use of additional specialized mailing list software such as
33045 Majordomo or Mailman is recommended.
33046
33047 The &(redirect)& router can be used to handle mailing lists where each list
33048 is maintained in a separate file, which can therefore be managed by an
33049 independent manager. The &%domains%& router option can be used to run these
33050 lists in a separate domain from normal mail. For example:
33051 .code
33052 lists:
33053 driver = redirect
33054 domains = lists.example
33055 file = /usr/lists/$local_part
33056 forbid_pipe
33057 forbid_file
33058 errors_to = $local_part-request@lists.example
33059 no_more
33060 .endd
33061 This router is skipped for domains other than &'lists.example'&. For addresses
33062 in that domain, it looks for a file that matches the local part. If there is no
33063 such file, the router declines, but because &%no_more%& is set, no subsequent
33064 routers are tried, and so the whole delivery fails.
33065
33066 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
33067 expanded into a file name or a pipe delivery, which is usually inappropriate in
33068 a mailing list.
33069
33070 .oindex "&%errors_to%&"
33071 The &%errors_to%& option specifies that any delivery errors caused by addresses
33072 taken from a mailing list are to be sent to the given address rather than the
33073 original sender of the message. However, before acting on this, Exim verifies
33074 the error address, and ignores it if verification fails.
33075
33076 For example, using the configuration above, mail sent to
33077 &'dicts@lists.example'& is passed on to those addresses contained in
33078 &_/usr/lists/dicts_&, with error reports directed to
33079 &'dicts-request@lists.example'&, provided that this address can be verified.
33080 There could be a file called &_/usr/lists/dicts-request_& containing
33081 the address(es) of this particular list's manager(s), but other approaches,
33082 such as setting up an earlier router (possibly using the &%local_part_prefix%&
33083 or &%local_part_suffix%& options) to handle addresses of the form
33084 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
33085
33086
33087
33088 .section "Syntax errors in mailing lists" "SECID241"
33089 .cindex "mailing lists" "syntax errors in"
33090 If an entry in redirection data contains a syntax error, Exim normally defers
33091 delivery of the original address. That means that a syntax error in a mailing
33092 list holds up all deliveries to the list. This may not be appropriate when a
33093 list is being maintained automatically from data supplied by users, and the
33094 addresses are not rigorously checked.
33095
33096 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
33097 entries that fail to parse, noting the incident in the log. If in addition
33098 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
33099 whenever a broken address is skipped. It is usually appropriate to set
33100 &%syntax_errors_to%& to the same address as &%errors_to%&.
33101
33102
33103
33104 .section "Re-expansion of mailing lists" "SECID242"
33105 .cindex "mailing lists" "re-expansion of"
33106 Exim remembers every individual address to which a message has been delivered,
33107 in order to avoid duplication, but it normally stores only the original
33108 recipient addresses with a message. If all the deliveries to a mailing list
33109 cannot be done at the first attempt, the mailing list is re-expanded when the
33110 delivery is next tried. This means that alterations to the list are taken into
33111 account at each delivery attempt, so addresses that have been added to
33112 the list since the message arrived will therefore receive a copy of the
33113 message, even though it pre-dates their subscription.
33114
33115 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
33116 on the &(redirect)& router. If this is done, any addresses generated by the
33117 router that fail to deliver at the first attempt are added to the message as
33118 &"top level"& addresses, and the parent address that generated them is marked
33119 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
33120 subsequent delivery attempts. The disadvantage of this is that if any of the
33121 failing addresses are incorrect, correcting them in the file has no effect on
33122 pre-existing messages.
33123
33124 The original top-level address is remembered with each of the generated
33125 addresses, and is output in any log messages. However, any intermediate parent
33126 addresses are not recorded. This makes a difference to the log only if the
33127 &%all_parents%& selector is set, but for mailing lists there is normally only
33128 one level of expansion anyway.
33129
33130
33131
33132 .section "Closed mailing lists" "SECID243"
33133 .cindex "mailing lists" "closed"
33134 The examples so far have assumed open mailing lists, to which anybody may
33135 send mail. It is also possible to set up closed lists, where mail is accepted
33136 from specified senders only. This is done by making use of the generic
33137 &%senders%& option to restrict the router that handles the list.
33138
33139 The following example uses the same file as a list of recipients and as a list
33140 of permitted senders. It requires three routers:
33141 .code
33142 lists_request:
33143 driver = redirect
33144 domains = lists.example
33145 local_part_suffix = -request
33146 file = /usr/lists/$local_part$local_part_suffix
33147 no_more
33148
33149 lists_post:
33150 driver = redirect
33151 domains = lists.example
33152 senders = ${if exists {/usr/lists/$local_part}\
33153 {lsearch;/usr/lists/$local_part}{*}}
33154 file = /usr/lists/$local_part
33155 forbid_pipe
33156 forbid_file
33157 errors_to = $local_part-request@lists.example
33158 no_more
33159
33160 lists_closed:
33161 driver = redirect
33162 domains = lists.example
33163 allow_fail
33164 data = :fail: $local_part@lists.example is a closed mailing list
33165 .endd
33166 All three routers have the same &%domains%& setting, so for any other domains,
33167 they are all skipped. The first router runs only if the local part ends in
33168 &%-request%&. It handles messages to the list manager(s) by means of an open
33169 mailing list.
33170
33171 The second router runs only if the &%senders%& precondition is satisfied. It
33172 checks for the existence of a list that corresponds to the local part, and then
33173 checks that the sender is on the list by means of a linear search. It is
33174 necessary to check for the existence of the file before trying to search it,
33175 because otherwise Exim thinks there is a configuration error. If the file does
33176 not exist, the expansion of &%senders%& is *, which matches all senders. This
33177 means that the router runs, but because there is no list, declines, and
33178 &%no_more%& ensures that no further routers are run. The address fails with an
33179 &"unrouteable address"& error.
33180
33181 The third router runs only if the second router is skipped, which happens when
33182 a mailing list exists, but the sender is not on it. This router forcibly fails
33183 the address, giving a suitable error message.
33184
33185
33186
33187
33188 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
33189 .cindex "VERP"
33190 .cindex "Variable Envelope Return Paths"
33191 .cindex "envelope sender"
33192 Variable Envelope Return Paths &-- see &url(http://cr.yp.to/proto/verp.txt) &--
33193 are a way of helping mailing list administrators discover which subscription
33194 address is the cause of a particular delivery failure. The idea is to encode
33195 the original recipient address in the outgoing envelope sender address, so that
33196 if the message is forwarded by another host and then subsequently bounces, the
33197 original recipient can be extracted from the recipient address of the bounce.
33198
33199 .oindex &%errors_to%&
33200 .oindex &%return_path%&
33201 Envelope sender addresses can be modified by Exim using two different
33202 facilities: the &%errors_to%& option on a router (as shown in previous mailing
33203 list examples), or the &%return_path%& option on a transport. The second of
33204 these is effective only if the message is successfully delivered to another
33205 host; it is not used for errors detected on the local host (see the description
33206 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
33207 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
33208 .code
33209 verp_smtp:
33210 driver = smtp
33211 max_rcpt = 1
33212 return_path = \
33213 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
33214 {$1-request+$local_part=$domain@your.dom.example}fail}
33215 .endd
33216 This has the effect of rewriting the return path (envelope sender) on outgoing
33217 SMTP messages, if the local part of the original return path ends in
33218 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
33219 local part and domain of the recipient into the return path. Suppose, for
33220 example, that a message whose return path has been set to
33221 &'somelist-request@your.dom.example'& is sent to
33222 &'subscriber@other.dom.example'&. In the transport, the return path is
33223 rewritten as
33224 .code
33225 somelist-request+subscriber=other.dom.example@your.dom.example
33226 .endd
33227 .vindex "&$local_part$&"
33228 For this to work, you must tell Exim to send multiple copies of messages that
33229 have more than one recipient, so that each copy has just one recipient. This is
33230 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
33231 might be sent to several different recipients in the same domain, in which case
33232 &$local_part$& is not available in the transport, because it is not unique.
33233
33234 Unless your host is doing nothing but mailing list deliveries, you should
33235 probably use a separate transport for the VERP deliveries, so as not to use
33236 extra resources in making one-per-recipient copies for other deliveries. This
33237 can easily be done by expanding the &%transport%& option in the router:
33238 .code
33239 dnslookup:
33240 driver = dnslookup
33241 domains = ! +local_domains
33242 transport = \
33243 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
33244 {verp_smtp}{remote_smtp}}
33245 no_more
33246 .endd
33247 If you want to change the return path using &%errors_to%& in a router instead
33248 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
33249 routers that handle mailing list addresses. This will ensure that all delivery
33250 errors, including those detected on the local host, are sent to the VERP
33251 address.
33252
33253 On a host that does no local deliveries and has no manual routing, only the
33254 &(dnslookup)& router needs to be changed. A special transport is not needed for
33255 SMTP deliveries. Every mailing list recipient has its own return path value,
33256 and so Exim must hand them to the transport one at a time. Here is an example
33257 of a &(dnslookup)& router that implements VERP:
33258 .code
33259 verp_dnslookup:
33260 driver = dnslookup
33261 domains = ! +local_domains
33262 transport = remote_smtp
33263 errors_to = \
33264 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
33265 {$1-request+$local_part=$domain@your.dom.example}fail}
33266 no_more
33267 .endd
33268 Before you start sending out messages with VERPed return paths, you must also
33269 configure Exim to accept the bounce messages that come back to those paths.
33270 Typically this is done by setting a &%local_part_suffix%& option for a
33271 router, and using this to route the messages to wherever you want to handle
33272 them.
33273
33274 The overhead incurred in using VERP depends very much on the size of the
33275 message, the number of recipient addresses that resolve to the same remote
33276 host, and the speed of the connection over which the message is being sent. If
33277 a lot of addresses resolve to the same host and the connection is slow, sending
33278 a separate copy of the message for each address may take substantially longer
33279 than sending a single copy with many recipients (for which VERP cannot be
33280 used).
33281
33282
33283
33284
33285
33286
33287 .section "Virtual domains" "SECTvirtualdomains"
33288 .cindex "virtual domains"
33289 .cindex "domain" "virtual"
33290 The phrase &'virtual domain'& is unfortunately used with two rather different
33291 meanings:
33292
33293 .ilist
33294 A domain for which there are no real mailboxes; all valid local parts are
33295 aliases for other email addresses. Common examples are organizational
33296 top-level domains and &"vanity"& domains.
33297 .next
33298 One of a number of independent domains that are all handled by the same host,
33299 with mailboxes on that host, but where the mailbox owners do not necessarily
33300 have login accounts on that host.
33301 .endlist
33302
33303 The first usage is probably more common, and does seem more &"virtual"& than
33304 the second. This kind of domain can be handled in Exim with a straightforward
33305 aliasing router. One approach is to create a separate alias file for each
33306 virtual domain. Exim can test for the existence of the alias file to determine
33307 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
33308 to a router of this form:
33309 .code
33310 virtual:
33311 driver = redirect
33312 domains = dsearch;/etc/mail/virtual
33313 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
33314 no_more
33315 .endd
33316 The &%domains%& option specifies that the router is to be skipped, unless there
33317 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
33318 domain that is being processed. When the router runs, it looks up the local
33319 part in the file to find a new address (or list of addresses). The &%no_more%&
33320 setting ensures that if the lookup fails (leading to &%data%& being an empty
33321 string), Exim gives up on the address without trying any subsequent routers.
33322
33323 This one router can handle all the virtual domains because the alias file names
33324 follow a fixed pattern. Permissions can be arranged so that appropriate people
33325 can edit the different alias files. A successful aliasing operation results in
33326 a new envelope recipient address, which is then routed from scratch.
33327
33328 The other kind of &"virtual"& domain can also be handled in a straightforward
33329 way. One approach is to create a file for each domain containing a list of
33330 valid local parts, and use it in a router like this:
33331 .code
33332 my_domains:
33333 driver = accept
33334 domains = dsearch;/etc/mail/domains
33335 local_parts = lsearch;/etc/mail/domains/$domain
33336 transport = my_mailboxes
33337 .endd
33338 The address is accepted if there is a file for the domain, and the local part
33339 can be found in the file. The &%domains%& option is used to check for the
33340 file's existence because &%domains%& is tested before the &%local_parts%&
33341 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
33342 because that option is tested after &%local_parts%&. The transport is as
33343 follows:
33344 .code
33345 my_mailboxes:
33346 driver = appendfile
33347 file = /var/mail/$domain/$local_part
33348 user = mail
33349 .endd
33350 This uses a directory of mailboxes for each domain. The &%user%& setting is
33351 required, to specify which uid is to be used for writing to the mailboxes.
33352
33353 The configuration shown here is just one example of how you might support this
33354 requirement. There are many other ways this kind of configuration can be set
33355 up, for example, by using a database instead of separate files to hold all the
33356 information about the domains.
33357
33358
33359
33360 .section "Multiple user mailboxes" "SECTmulbox"
33361 .cindex "multiple mailboxes"
33362 .cindex "mailbox" "multiple"
33363 .cindex "local part" "prefix"
33364 .cindex "local part" "suffix"
33365 Heavy email users often want to operate with multiple mailboxes, into which
33366 incoming mail is automatically sorted. A popular way of handling this is to
33367 allow users to use multiple sender addresses, so that replies can easily be
33368 identified. Users are permitted to add prefixes or suffixes to their local
33369 parts for this purpose. The wildcard facility of the generic router options
33370 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
33371 example, consider this router:
33372 .code
33373 userforward:
33374 driver = redirect
33375 check_local_user
33376 file = $home/.forward
33377 local_part_suffix = -*
33378 local_part_suffix_optional
33379 allow_filter
33380 .endd
33381 .vindex "&$local_part_suffix$&"
33382 It runs a user's &_.forward_& file for all local parts of the form
33383 &'username-*'&. Within the filter file the user can distinguish different
33384 cases by testing the variable &$local_part_suffix$&. For example:
33385 .code
33386 if $local_part_suffix contains -special then
33387 save /home/$local_part/Mail/special
33388 endif
33389 .endd
33390 If the filter file does not exist, or does not deal with such addresses, they
33391 fall through to subsequent routers, and, assuming no subsequent use of the
33392 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
33393 control over which suffixes are valid.
33394
33395 Alternatively, a suffix can be used to trigger the use of a different
33396 &_.forward_& file &-- which is the way a similar facility is implemented in
33397 another MTA:
33398 .code
33399 userforward:
33400 driver = redirect
33401 check_local_user
33402 file = $home/.forward$local_part_suffix
33403 local_part_suffix = -*
33404 local_part_suffix_optional
33405 allow_filter
33406 .endd
33407 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
33408 example, &_.forward-special_& is used. Once again, if the appropriate file
33409 does not exist, or does not deal with the address, it is passed on to
33410 subsequent routers, which could, if required, look for an unqualified
33411 &_.forward_& file to use as a default.
33412
33413
33414
33415 .section "Simplified vacation processing" "SECID244"
33416 .cindex "vacation processing"
33417 The traditional way of running the &'vacation'& program is for a user to set up
33418 a pipe command in a &_.forward_& file
33419 (see section &<<SECTspecitredli>>& for syntax details).
33420 This is prone to error by inexperienced users. There are two features of Exim
33421 that can be used to make this process simpler for users:
33422
33423 .ilist
33424 A local part prefix such as &"vacation-"& can be specified on a router which
33425 can cause the message to be delivered directly to the &'vacation'& program, or
33426 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
33427 &_.forward_& file are then much simpler. For example:
33428 .code
33429 spqr, vacation-spqr
33430 .endd
33431 .next
33432 The &%require_files%& generic router option can be used to trigger a
33433 vacation delivery by checking for the existence of a certain file in the
33434 user's home directory. The &%unseen%& generic option should also be used, to
33435 ensure that the original delivery also proceeds. In this case, all the user has
33436 to do is to create a file called, say, &_.vacation_&, containing a vacation
33437 message.
33438 .endlist
33439
33440 Another advantage of both these methods is that they both work even when the
33441 use of arbitrary pipes by users is locked out.
33442
33443
33444
33445 .section "Taking copies of mail" "SECID245"
33446 .cindex "message" "copying every"
33447 Some installations have policies that require archive copies of all messages to
33448 be made. A single copy of each message can easily be taken by an appropriate
33449 command in a system filter, which could, for example, use a different file for
33450 each day's messages.
33451
33452 There is also a shadow transport mechanism that can be used to take copies of
33453 messages that are successfully delivered by local transports, one copy per
33454 delivery. This could be used, &'inter alia'&, to implement automatic
33455 notification of delivery by sites that insist on doing such things.
33456
33457
33458
33459 .section "Intermittently connected hosts" "SECID246"
33460 .cindex "intermittently connected hosts"
33461 It has become quite common (because it is cheaper) for hosts to connect to the
33462 Internet periodically rather than remain connected all the time. The normal
33463 arrangement is that mail for such hosts accumulates on a system that is
33464 permanently connected.
33465
33466 Exim was designed for use on permanently connected hosts, and so it is not
33467 particularly well-suited to use in an intermittently connected environment.
33468 Nevertheless there are some features that can be used.
33469
33470
33471 .section "Exim on the upstream server host" "SECID247"
33472 It is tempting to arrange for incoming mail for the intermittently connected
33473 host to remain on Exim's queue until the client connects. However, this
33474 approach does not scale very well. Two different kinds of waiting message are
33475 being mixed up in the same queue &-- those that cannot be delivered because of
33476 some temporary problem, and those that are waiting for their destination host
33477 to connect. This makes it hard to manage the queue, as well as wasting
33478 resources, because each queue runner scans the entire queue.
33479
33480 A better approach is to separate off those messages that are waiting for an
33481 intermittently connected host. This can be done by delivering these messages
33482 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
33483 format, from where they are transmitted by other software when their
33484 destination connects. This makes it easy to collect all the mail for one host
33485 in a single directory, and to apply local timeout rules on a per-message basis
33486 if required.
33487
33488 On a very small scale, leaving the mail on Exim's queue can be made to work. If
33489 you are doing this, you should configure Exim with a long retry period for the
33490 intermittent host. For example:
33491 .code
33492 cheshire.wonderland.fict.example * F,5d,24h
33493 .endd
33494 This stops a lot of failed delivery attempts from occurring, but Exim remembers
33495 which messages it has queued up for that host. Once the intermittent host comes
33496 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
33497 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
33498 causes all the queued up messages to be delivered, often down a single SMTP
33499 connection. While the host remains connected, any new messages get delivered
33500 immediately.
33501
33502 If the connecting hosts do not have fixed IP addresses, that is, if a host is
33503 issued with a different IP address each time it connects, Exim's retry
33504 mechanisms on the holding host get confused, because the IP address is normally
33505 used as part of the key string for holding retry information. This can be
33506 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
33507 Since this has disadvantages for permanently connected hosts, it is best to
33508 arrange a separate transport for the intermittently connected ones.
33509
33510
33511
33512 .section "Exim on the intermittently connected client host" "SECID248"
33513 The value of &%smtp_accept_queue_per_connection%& should probably be
33514 increased, or even set to zero (that is, disabled) on the intermittently
33515 connected host, so that all incoming messages down a single connection get
33516 delivered immediately.
33517
33518 .cindex "SMTP" "passed connection"
33519 .cindex "SMTP" "multiple deliveries"
33520 .cindex "multiple SMTP deliveries"
33521 Mail waiting to be sent from an intermittently connected host will probably
33522 not have been routed, because without a connection DNS lookups are not
33523 possible. This means that if a normal queue run is done at connection time,
33524 each message is likely to be sent in a separate SMTP session. This can be
33525 avoided by starting the queue run with a command line option beginning with
33526 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
33527 first pass, routing is done but no deliveries take place. The second pass is a
33528 normal queue run; since all the messages have been previously routed, those
33529 destined for the same host are likely to get sent as multiple deliveries in a
33530 single SMTP connection.
33531
33532
33533
33534 . ////////////////////////////////////////////////////////////////////////////
33535 . ////////////////////////////////////////////////////////////////////////////
33536
33537 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
33538 "Exim as a non-queueing client"
33539 .cindex "client, non-queueing"
33540 .cindex "smart host" "suppressing queueing"
33541 On a personal computer, it is a common requirement for all
33542 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
33543 configured to operate that way, for all the popular operating systems.
33544 However, there are some MUAs for Unix-like systems that cannot be so
33545 configured: they submit messages using the command line interface of
33546 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
33547 messages this way.
33548
33549 If the personal computer runs continuously, there is no problem, because it can
33550 run a conventional MTA that handles delivery to the smart host, and deal with
33551 any delays via its queueing mechanism. However, if the computer does not run
33552 continuously or runs different operating systems at different times, queueing
33553 email is not desirable.
33554
33555 There is therefore a requirement for something that can provide the
33556 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
33557 any queueing or retrying facilities. Furthermore, the delivery to the smart
33558 host should be synchronous, so that if it fails, the sending MUA is immediately
33559 informed. In other words, we want something that extends an MUA that submits
33560 to a local MTA via the command line so that it behaves like one that submits
33561 to a remote smart host using TCP/SMTP.
33562
33563 There are a number of applications (for example, there is one called &'ssmtp'&)
33564 that do this job. However, people have found them to be lacking in various
33565 ways. For instance, you might want to allow aliasing and forwarding to be done
33566 before sending a message to the smart host.
33567
33568 Exim already had the necessary infrastructure for doing this job. Just a few
33569 tweaks were needed to make it behave as required, though it is somewhat of an
33570 overkill to use a fully-featured MTA for this purpose.
33571
33572 .oindex "&%mua_wrapper%&"
33573 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
33574 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
33575 assumes that it is being used to &"wrap"& a command-line MUA in the manner
33576 just described. As well as setting &%mua_wrapper%&, you also need to provide a
33577 compatible router and transport configuration. Typically there will be just one
33578 router and one transport, sending everything to a smart host.
33579
33580 When run in MUA wrapping mode, the behaviour of Exim changes in the
33581 following ways:
33582
33583 .ilist
33584 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
33585 In other words, the only way to submit messages is via the command line.
33586 .next
33587 Each message is synchronously delivered as soon as it is received (&%-odi%& is
33588 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
33589 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
33590 does not finish until the delivery attempt is complete. If the delivery is
33591 successful, a zero return code is given.
33592 .next
33593 Address redirection is permitted, but the final routing for all addresses must
33594 be to the same remote transport, and to the same list of hosts. Furthermore,
33595 the return address (envelope sender) must be the same for all recipients, as
33596 must any added or deleted header lines. In other words, it must be possible to
33597 deliver the message in a single SMTP transaction, however many recipients there
33598 are.
33599 .next
33600 If these conditions are not met, or if routing any address results in a
33601 failure or defer status, or if Exim is unable to deliver all the recipients
33602 successfully to one of the smart hosts, delivery of the entire message fails.
33603 .next
33604 Because no queueing is allowed, all failures are treated as permanent; there
33605 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
33606 smart host. Furthermore, because only a single yes/no response can be given to
33607 the caller, it is not possible to deliver to some recipients and not others. If
33608 there is an error (temporary or permanent) for any recipient, all are failed.
33609 .next
33610 If more than one smart host is listed, Exim will try another host after a
33611 connection failure or a timeout, in the normal way. However, if this kind of
33612 failure happens for all the hosts, the delivery fails.
33613 .next
33614 When delivery fails, an error message is written to the standard error stream
33615 (as well as to Exim's log), and Exim exits to the caller with a return code
33616 value 1. The message is expunged from Exim's spool files. No bounce messages
33617 are ever generated.
33618 .next
33619 No retry data is maintained, and any retry rules are ignored.
33620 .next
33621 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
33622 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
33623 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
33624 .endlist
33625
33626 The overall effect is that Exim makes a single synchronous attempt to deliver
33627 the message, failing if there is any kind of problem. Because no local
33628 deliveries are done and no daemon can be run, Exim does not need root
33629 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
33630 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
33631 the advantages and disadvantages of running without root privilege.
33632
33633
33634
33635
33636 . ////////////////////////////////////////////////////////////////////////////
33637 . ////////////////////////////////////////////////////////////////////////////
33638
33639 .chapter "Log files" "CHAPlog"
33640 .scindex IIDloggen "log" "general description"
33641 .cindex "log" "types of"
33642 Exim writes three different logs, referred to as the main log, the reject log,
33643 and the panic log:
33644
33645 .ilist
33646 .cindex "main log"
33647 The main log records the arrival of each message and each delivery in a single
33648 line in each case. The format is as compact as possible, in an attempt to keep
33649 down the size of log files. Two-character flag sequences make it easy to pick
33650 out these lines. A number of other events are recorded in the main log. Some of
33651 them are optional, in which case the &%log_selector%& option controls whether
33652 they are included or not. A Perl script called &'eximstats'&, which does simple
33653 analysis of main log files, is provided in the Exim distribution (see section
33654 &<<SECTmailstat>>&).
33655 .next
33656 .cindex "reject log"
33657 The reject log records information from messages that are rejected as a result
33658 of a configuration option (that is, for policy reasons).
33659 The first line of each rejection is a copy of the line that is also written to
33660 the main log. Then, if the message's header has been read at the time the log
33661 is written, its contents are written to this log. Only the original header
33662 lines are available; header lines added by ACLs are not logged. You can use the
33663 reject log to check that your policy controls are working correctly; on a busy
33664 host this may be easier than scanning the main log for rejection messages. You
33665 can suppress the writing of the reject log by setting &%write_rejectlog%&
33666 false.
33667 .next
33668 .cindex "panic log"
33669 .cindex "system log"
33670 When certain serious errors occur, Exim writes entries to its panic log. If the
33671 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
33672 are usually written to the main log as well, but can get lost amid the mass of
33673 other entries. The panic log should be empty under normal circumstances. It is
33674 therefore a good idea to check it (or to have a &'cron'& script check it)
33675 regularly, in order to become aware of any problems. When Exim cannot open its
33676 panic log, it tries as a last resort to write to the system log (syslog). This
33677 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
33678 message itself is written at priority LOG_CRIT.
33679 .endlist
33680
33681 Every log line starts with a timestamp, in the format shown in the following
33682 example. Note that many of the examples shown in this chapter are line-wrapped.
33683 In the log file, this would be all on one line:
33684 .code
33685 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
33686 by QUIT
33687 .endd
33688 By default, the timestamps are in the local timezone. There are two
33689 ways of changing this:
33690
33691 .ilist
33692 You can set the &%timezone%& option to a different time zone; in particular, if
33693 you set
33694 .code
33695 timezone = UTC
33696 .endd
33697 the timestamps will be in UTC (aka GMT).
33698 .next
33699 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
33700 example:
33701 .code
33702 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
33703 .endd
33704 .endlist
33705
33706 .cindex "log" "process ids in"
33707 .cindex "pid (process id)" "in log lines"
33708 Exim does not include its process id in log lines by default, but you can
33709 request that it does so by specifying the &`pid`& log selector (see section
33710 &<<SECTlogselector>>&). When this is set, the process id is output, in square
33711 brackets, immediately after the time and date.
33712
33713
33714
33715
33716 .section "Where the logs are written" "SECTwhelogwri"
33717 .cindex "log" "destination"
33718 .cindex "log" "to file"
33719 .cindex "log" "to syslog"
33720 .cindex "syslog"
33721 The logs may be written to local files, or to syslog, or both. However, it
33722 should be noted that many syslog implementations use UDP as a transport, and
33723 are therefore unreliable in the sense that messages are not guaranteed to
33724 arrive at the loghost, nor is the ordering of messages necessarily maintained.
33725 It has also been reported that on large log files (tens of megabytes) you may
33726 need to tweak syslog to prevent it syncing the file with each write &-- on
33727 Linux this has been seen to make syslog take 90% plus of CPU time.
33728
33729 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
33730 &_Local/Makefile_& or by setting &%log_file_path%& in the run time
33731 configuration. This latter string is expanded, so it can contain, for example,
33732 references to the host name:
33733 .code
33734 log_file_path = /var/log/$primary_hostname/exim_%slog
33735 .endd
33736 It is generally advisable, however, to set the string in &_Local/Makefile_&
33737 rather than at run time, because then the setting is available right from the
33738 start of Exim's execution. Otherwise, if there's something it wants to log
33739 before it has read the configuration file (for example, an error in the
33740 configuration file) it will not use the path you want, and may not be able to
33741 log at all.
33742
33743 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
33744 list, currently limited to at most two items. This is one option where the
33745 facility for changing a list separator may not be used. The list must always be
33746 colon-separated. If an item in the list is &"syslog"& then syslog is used;
33747 otherwise the item must either be an absolute path, containing &`%s`& at the
33748 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
33749 implying the use of a default path.
33750
33751 When Exim encounters an empty item in the list, it searches the list defined by
33752 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
33753 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
33754 mean &"use the path specified at build time"&. It no such item exists, log
33755 files are written in the &_log_& subdirectory of the spool directory. This is
33756 equivalent to the setting:
33757 .code
33758 log_file_path = $spool_directory/log/%slog
33759 .endd
33760 If you do not specify anything at build time or run time, that is where the
33761 logs are written.
33762
33763 A log file path may also contain &`%D`& or &`%M`& if datestamped log file names
33764 are in use &-- see section &<<SECTdatlogfil>>& below.
33765
33766 Here are some examples of possible settings:
33767 .display
33768 &`LOG_FILE_PATH=syslog `& syslog only
33769 &`LOG_FILE_PATH=:syslog `& syslog and default path
33770 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
33771 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
33772 .endd
33773 If there are more than two paths in the list, the first is used and a panic
33774 error is logged.
33775
33776
33777
33778 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
33779 .cindex "log" "cycling local files"
33780 .cindex "cycling logs"
33781 .cindex "&'exicyclog'&"
33782 .cindex "log" "local files; writing to"
33783 Some operating systems provide centralized and standardized methods for cycling
33784 log files. For those that do not, a utility script called &'exicyclog'& is
33785 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
33786 main and reject logs each time it is called. The maximum number of old logs to
33787 keep can be set. It is suggested this script is run as a daily &'cron'& job.
33788
33789 An Exim delivery process opens the main log when it first needs to write to it,
33790 and it keeps the file open in case subsequent entries are required &-- for
33791 example, if a number of different deliveries are being done for the same
33792 message. However, remote SMTP deliveries can take a long time, and this means
33793 that the file may be kept open long after it is renamed if &'exicyclog'& or
33794 something similar is being used to rename log files on a regular basis. To
33795 ensure that a switch of log files is noticed as soon as possible, Exim calls
33796 &[stat()]& on the main log's name before reusing an open file, and if the file
33797 does not exist, or its inode has changed, the old file is closed and Exim
33798 tries to open the main log from scratch. Thus, an old log file may remain open
33799 for quite some time, but no Exim processes should write to it once it has been
33800 renamed.
33801
33802
33803
33804 .section "Datestamped log files" "SECTdatlogfil"
33805 .cindex "log" "datestamped files"
33806 Instead of cycling the main and reject log files by renaming them
33807 periodically, some sites like to use files whose names contain a datestamp,
33808 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
33809 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
33810 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
33811 point where the datestamp is required. For example:
33812 .code
33813 log_file_path = /var/spool/exim/log/%slog-%D
33814 log_file_path = /var/log/exim-%s-%D.log
33815 log_file_path = /var/spool/exim/log/%D-%slog
33816 log_file_path = /var/log/exim/%s.%M
33817 .endd
33818 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
33819 examples of names generated by the above examples:
33820 .code
33821 /var/spool/exim/log/mainlog-20021225
33822 /var/log/exim-reject-20021225.log
33823 /var/spool/exim/log/20021225-mainlog
33824 /var/log/exim/main.200212
33825 .endd
33826 When this form of log file is specified, Exim automatically switches to new
33827 files at midnight. It does not make any attempt to compress old logs; you
33828 will need to write your own script if you require this. You should not
33829 run &'exicyclog'& with this form of logging.
33830
33831 The location of the panic log is also determined by &%log_file_path%&, but it
33832 is not datestamped, because rotation of the panic log does not make sense.
33833 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
33834 the string. In addition, if it immediately follows a slash, a following
33835 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
33836 character is removed. Thus, the four examples above would give these panic
33837 log names:
33838 .code
33839 /var/spool/exim/log/paniclog
33840 /var/log/exim-panic.log
33841 /var/spool/exim/log/paniclog
33842 /var/log/exim/panic
33843 .endd
33844
33845
33846 .section "Logging to syslog" "SECID249"
33847 .cindex "log" "syslog; writing to"
33848 The use of syslog does not change what Exim logs or the format of its messages,
33849 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
33850 Exim's log lines are omitted when these lines are sent to syslog. Apart from
33851 that, the same strings are written to syslog as to log files. The syslog
33852 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
33853 by default, but you can change these by setting the &%syslog_facility%& and
33854 &%syslog_processname%& options, respectively. If Exim was compiled with
33855 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
33856 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
33857 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
33858 the time and host name to each line.
33859 The three log streams are mapped onto syslog priorities as follows:
33860
33861 .ilist
33862 &'mainlog'& is mapped to LOG_INFO
33863 .next
33864 &'rejectlog'& is mapped to LOG_NOTICE
33865 .next
33866 &'paniclog'& is mapped to LOG_ALERT
33867 .endlist
33868
33869 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
33870 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
33871 these are routed by syslog to the same place. You can suppress this duplication
33872 by setting &%syslog_duplication%& false.
33873
33874 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
33875 entries contain multiple lines when headers are included. To cope with both
33876 these cases, entries written to syslog are split into separate &[syslog()]&
33877 calls at each internal newline, and also after a maximum of
33878 870 data characters. (This allows for a total syslog line length of 1024, when
33879 additions such as timestamps are added.) If you are running a syslog
33880 replacement that can handle lines longer than the 1024 characters allowed by
33881 RFC 3164, you should set
33882 .code
33883 SYSLOG_LONG_LINES=yes
33884 .endd
33885 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
33886 lines, but it still splits at internal newlines in &'reject'& log entries.
33887
33888 To make it easy to re-assemble split lines later, each component of a split
33889 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
33890 where <&'n'&> is the component number and <&'m'&> is the total number of
33891 components in the entry. The / delimiter is used when the line was split
33892 because it was too long; if it was split because of an internal newline, the \
33893 delimiter is used. For example, supposing the length limit to be 50 instead of
33894 870, the following would be the result of a typical rejection message to
33895 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
33896 name, and pid as added by syslog:
33897 .code
33898 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
33899 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
33900 [3/5] when scanning for sender: missing or malformed lo
33901 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
33902 [5/5] mple>)
33903 .endd
33904 The same error might cause the following lines to be written to &"rejectlog"&
33905 (LOG_NOTICE):
33906 .code
33907 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
33908 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
33909 [3/18] er when scanning for sender: missing or malformed
33910 [4/18] local part in "<>" (envelope sender is <ph10@cam
33911 [5\18] .example>)
33912 [6\18] Recipients: ph10@some.domain.cam.example
33913 [7\18] P Received: from [127.0.0.1] (ident=ph10)
33914 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
33915 [9\18] id 16RdAL-0006pc-00
33916 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
33917 [11\18] 09:43 +0100
33918 [12\18] F From: <>
33919 [13\18] Subject: this is a test header
33920 [18\18] X-something: this is another header
33921 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
33922 [16\18] le>
33923 [17\18] B Bcc:
33924 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
33925 .endd
33926 Log lines that are neither too long nor contain newlines are written to syslog
33927 without modification.
33928
33929 If only syslog is being used, the Exim monitor is unable to provide a log tail
33930 display, unless syslog is routing &'mainlog'& to a file on the local host and
33931 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
33932 where it is.
33933
33934
33935
33936 .section "Log line flags" "SECID250"
33937 One line is written to the main log for each message received, and for each
33938 successful, unsuccessful, and delayed delivery. These lines can readily be
33939 picked out by the distinctive two-character flags that immediately follow the
33940 timestamp. The flags are:
33941 .display
33942 &`<=`& message arrival
33943 &`=>`& normal message delivery
33944 &`->`& additional address in same delivery
33945 &`>>`& cutthrough message delivery
33946 &`*>`& delivery suppressed by &%-N%&
33947 &`**`& delivery failed; address bounced
33948 &`==`& delivery deferred; temporary problem
33949 .endd
33950
33951
33952 .section "Logging message reception" "SECID251"
33953 .cindex "log" "reception line"
33954 The format of the single-line entry in the main log that is written for every
33955 message received is shown in the basic example below, which is split over
33956 several lines in order to fit it on the page:
33957 .code
33958 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
33959 H=mailer.fict.example [192.168.123.123] U=exim
33960 P=smtp S=5678 id=<incoming message id>
33961 .endd
33962 The address immediately following &"<="& is the envelope sender address. A
33963 bounce message is shown with the sender address &"<>"&, and if it is locally
33964 generated, this is followed by an item of the form
33965 .code
33966 R=<message id>
33967 .endd
33968 which is a reference to the message that caused the bounce to be sent.
33969
33970 .cindex "HELO"
33971 .cindex "EHLO"
33972 For messages from other hosts, the H and U fields identify the remote host and
33973 record the RFC 1413 identity of the user that sent the message, if one was
33974 received. The number given in square brackets is the IP address of the sending
33975 host. If there is a single, unparenthesized host name in the H field, as
33976 above, it has been verified to correspond to the IP address (see the
33977 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
33978 by the remote host in the SMTP HELO or EHLO command, and has not been
33979 verified. If verification yields a different name to that given for HELO or
33980 EHLO, the verified name appears first, followed by the HELO or EHLO
33981 name in parentheses.
33982
33983 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
33984 without brackets, in the HELO or EHLO command, leading to entries in
33985 the log containing text like these examples:
33986 .code
33987 H=(10.21.32.43) [192.168.8.34]
33988 H=([10.21.32.43]) [192.168.8.34]
33989 .endd
33990 This can be confusing. Only the final address in square brackets can be relied
33991 on.
33992
33993 For locally generated messages (that is, messages not received over TCP/IP),
33994 the H field is omitted, and the U field contains the login name of the caller
33995 of Exim.
33996
33997 .cindex "authentication" "logging"
33998 .cindex "AUTH" "logging"
33999 For all messages, the P field specifies the protocol used to receive the
34000 message. This is the value that is stored in &$received_protocol$&. In the case
34001 of incoming SMTP messages, the value indicates whether or not any SMTP
34002 extensions (ESMTP), encryption, or authentication were used. If the SMTP
34003 session was encrypted, there is an additional X field that records the cipher
34004 suite that was used.
34005
34006 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
34007 hosts that have authenticated themselves using the SMTP AUTH command. The first
34008 value is used when the SMTP connection was encrypted (&"secure"&). In this case
34009 there is an additional item A= followed by the name of the authenticator that
34010 was used. If an authenticated identification was set up by the authenticator's
34011 &%server_set_id%& option, this is logged too, separated by a colon from the
34012 authenticator name.
34013
34014 .cindex "size" "of message"
34015 The id field records the existing message id, if present. The size of the
34016 received message is given by the S field. When the message is delivered,
34017 headers may be removed or added, so that the size of delivered copies of the
34018 message may not correspond with this value (and indeed may be different to each
34019 other).
34020
34021 The &%log_selector%& option can be used to request the logging of additional
34022 data when a message is received. See section &<<SECTlogselector>>& below.
34023
34024
34025
34026 .section "Logging deliveries" "SECID252"
34027 .cindex "log" "delivery line"
34028 The format of the single-line entry in the main log that is written for every
34029 delivery is shown in one of the examples below, for local and remote
34030 deliveries, respectively. Each example has been split into two lines in order
34031 to fit it on the page:
34032 .code
34033 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
34034 <marv@hitch.fict.example> R=localuser T=local_delivery
34035 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
34036 monk@holistic.fict.example R=dnslookup T=remote_smtp
34037 H=holistic.fict.example [192.168.234.234]
34038 .endd
34039 For ordinary local deliveries, the original address is given in angle brackets
34040 after the final delivery address, which might be a pipe or a file. If
34041 intermediate address(es) exist between the original and the final address, the
34042 last of these is given in parentheses after the final address. The R and T
34043 fields record the router and transport that were used to process the address.
34044
34045 If SMTP AUTH was used for the delivery there is an additional item A=
34046 followed by the name of the authenticator that was used.
34047 If an authenticated identification was set up by the authenticator's &%client_set_id%&
34048 option, this is logged too, separated by a colon from the authenticator name.
34049
34050 If a shadow transport was run after a successful local delivery, the log line
34051 for the successful delivery has an item added on the end, of the form
34052 .display
34053 &`ST=<`&&'shadow transport name'&&`>`&
34054 .endd
34055 If the shadow transport did not succeed, the error message is put in
34056 parentheses afterwards.
34057
34058 .cindex "asterisk" "after IP address"
34059 When more than one address is included in a single delivery (for example, two
34060 SMTP RCPT commands in one transaction) the second and subsequent addresses are
34061 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
34062 down a single SMTP connection, an asterisk follows the IP address in the log
34063 lines for the second and subsequent messages.
34064
34065 .cindex "delivery" "cutthrough; logging"
34066 .cindex "cutthrough" "logging"
34067 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
34068 line precedes the reception line, since cutthrough waits for a possible
34069 rejection from the destination in case it can reject the sourced item.
34070
34071 The generation of a reply message by a filter file gets logged as a
34072 &"delivery"& to the addressee, preceded by &">"&.
34073
34074 The &%log_selector%& option can be used to request the logging of additional
34075 data when a message is delivered. See section &<<SECTlogselector>>& below.
34076
34077
34078 .section "Discarded deliveries" "SECID253"
34079 .cindex "discarded messages"
34080 .cindex "message" "discarded"
34081 .cindex "delivery" "discarded; logging"
34082 When a message is discarded as a result of the command &"seen finish"& being
34083 obeyed in a filter file which generates no deliveries, a log entry of the form
34084 .code
34085 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
34086 <low.club@bridge.example> R=userforward
34087 .endd
34088 is written, to record why no deliveries are logged. When a message is discarded
34089 because it is aliased to &":blackhole:"& the log line is like this:
34090 .code
34091 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
34092 <hole@nowhere.example> R=blackhole_router
34093 .endd
34094
34095
34096 .section "Deferred deliveries" "SECID254"
34097 When a delivery is deferred, a line of the following form is logged:
34098 .code
34099 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
34100 R=dnslookup T=smtp defer (146): Connection refused
34101 .endd
34102 In the case of remote deliveries, the error is the one that was given for the
34103 last IP address that was tried. Details of individual SMTP failures are also
34104 written to the log, so the above line would be preceded by something like
34105 .code
34106 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
34107 mail1.endrest.example [192.168.239.239]: Connection refused
34108 .endd
34109 When a deferred address is skipped because its retry time has not been reached,
34110 a message is written to the log, but this can be suppressed by setting an
34111 appropriate value in &%log_selector%&.
34112
34113
34114
34115 .section "Delivery failures" "SECID255"
34116 .cindex "delivery" "failure; logging"
34117 If a delivery fails because an address cannot be routed, a line of the
34118 following form is logged:
34119 .code
34120 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
34121 <jim@trek99.example>: unknown mail domain
34122 .endd
34123 If a delivery fails at transport time, the router and transport are shown, and
34124 the response from the remote host is included, as in this example:
34125 .code
34126 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
34127 R=dnslookup T=remote_smtp: SMTP error from remote mailer
34128 after pipelined RCPT TO:<ace400@pb.example>: host
34129 pbmail3.py.example [192.168.63.111]: 553 5.3.0
34130 <ace400@pb.example>...Addressee unknown
34131 .endd
34132 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
34133 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
34134 disabling PIPELINING. The log lines for all forms of delivery failure are
34135 flagged with &`**`&.
34136
34137
34138
34139 .section "Fake deliveries" "SECID256"
34140 .cindex "delivery" "fake; logging"
34141 If a delivery does not actually take place because the &%-N%& option has been
34142 used to suppress it, a normal delivery line is written to the log, except that
34143 &"=>"& is replaced by &"*>"&.
34144
34145
34146
34147 .section "Completion" "SECID257"
34148 A line of the form
34149 .code
34150 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
34151 .endd
34152 is written to the main log when a message is about to be removed from the spool
34153 at the end of its processing.
34154
34155
34156
34157
34158 .section "Summary of Fields in Log Lines" "SECID258"
34159 .cindex "log" "summary of fields"
34160 A summary of the field identifiers that are used in log lines is shown in
34161 the following table:
34162 .display
34163 &`A `& authenticator name (and optional id and sender)
34164 &`C `& SMTP confirmation on delivery
34165 &` `& command list for &"no mail in SMTP session"&
34166 &`CV `& certificate verification status
34167 &`D `& duration of &"no mail in SMTP session"&
34168 &`DN `& distinguished name from peer certificate
34169 &`DT `& on &`=>`& lines: time taken for a delivery
34170 &`F `& sender address (on delivery lines)
34171 &`H `& host name and IP address
34172 &`I `& local interface used
34173 &`id `& message id for incoming message
34174 &`P `& on &`<=`& lines: protocol used
34175 &` `& on &`=>`& and &`**`& lines: return path
34176 &`QT `& on &`=>`& lines: time spent on queue so far
34177 &` `& on &"Completed"& lines: time spent on queue
34178 &`R `& on &`<=`& lines: reference for local bounce
34179 &` `& on &`=>`& &`**`& and &`==`& lines: router name
34180 &`S `& size of message
34181 &`SNI `& server name indication from TLS client hello
34182 &`ST `& shadow transport name
34183 &`T `& on &`<=`& lines: message subject (topic)
34184 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
34185 &`U `& local user or RFC 1413 identity
34186 &`X `& TLS cipher suite
34187 .endd
34188
34189
34190 .section "Other log entries" "SECID259"
34191 Various other types of log entry are written from time to time. Most should be
34192 self-explanatory. Among the more common are:
34193
34194 .ilist
34195 .cindex "retry" "time not reached"
34196 &'retry time not reached'&&~&~An address previously suffered a temporary error
34197 during routing or local delivery, and the time to retry has not yet arrived.
34198 This message is not written to an individual message log file unless it happens
34199 during the first delivery attempt.
34200 .next
34201 &'retry time not reached for any host'&&~&~An address previously suffered
34202 temporary errors during remote delivery, and the retry time has not yet arrived
34203 for any of the hosts to which it is routed.
34204 .next
34205 .cindex "spool directory" "file locked"
34206 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
34207 some other Exim process is already working on the message. This can be quite
34208 common if queue running processes are started at frequent intervals. The
34209 &'exiwhat'& utility script can be used to find out what Exim processes are
34210 doing.
34211 .next
34212 .cindex "error" "ignored"
34213 &'error ignored'&&~&~There are several circumstances that give rise to this
34214 message:
34215 .olist
34216 Exim failed to deliver a bounce message whose age was greater than
34217 &%ignore_bounce_errors_after%&. The bounce was discarded.
34218 .next
34219 A filter file set up a delivery using the &"noerror"& option, and the delivery
34220 failed. The delivery was discarded.
34221 .next
34222 A delivery set up by a router configured with
34223 . ==== As this is a nested list, any displays it contains must be indented
34224 . ==== as otherwise they are too far to the left.
34225 .code
34226 errors_to = <>
34227 .endd
34228 failed. The delivery was discarded.
34229 .endlist olist
34230 .endlist ilist
34231
34232
34233
34234
34235
34236 .section "Reducing or increasing what is logged" "SECTlogselector"
34237 .cindex "log" "selectors"
34238 By setting the &%log_selector%& global option, you can disable some of Exim's
34239 default logging, or you can request additional logging. The value of
34240 &%log_selector%& is made up of names preceded by plus or minus characters. For
34241 example:
34242 .code
34243 log_selector = +arguments -retry_defer
34244 .endd
34245 The list of optional log items is in the following table, with the default
34246 selection marked by asterisks:
34247 .display
34248 &` 8bitmime `& received 8BITMIME status
34249 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
34250 &` address_rewrite `& address rewriting
34251 &` all_parents `& all parents in => lines
34252 &` arguments `& command line arguments
34253 &`*connection_reject `& connection rejections
34254 &`*delay_delivery `& immediate delivery delayed
34255 &` deliver_time `& time taken to perform delivery
34256 &` delivery_size `& add &`S=`&&'nnn'& to => lines
34257 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
34258 &`*etrn `& ETRN commands
34259 &`*host_lookup_failed `& as it says
34260 &` ident_timeout `& timeout for ident connection
34261 &` incoming_interface `& incoming interface on <= lines
34262 &` incoming_port `& incoming port on <= lines
34263 &`*lost_incoming_connection `& as it says (includes timeouts)
34264 &` outgoing_port `& add remote port to => lines
34265 &`*queue_run `& start and end queue runs
34266 &` queue_time `& time on queue for one recipient
34267 &` queue_time_overall `& time on queue for whole message
34268 &` pid `& Exim process id
34269 &` received_recipients `& recipients on <= lines
34270 &` received_sender `& sender on <= lines
34271 &`*rejected_header `& header contents on reject log
34272 &`*retry_defer `& &"retry time not reached"&
34273 &` return_path_on_delivery `& put return path on => and ** lines
34274 &` sender_on_delivery `& add sender to => lines
34275 &`*sender_verify_fail `& sender verification failures
34276 &`*size_reject `& rejection because too big
34277 &`*skip_delivery `& delivery skipped in a queue run
34278 &`*smtp_confirmation `& SMTP confirmation on => lines
34279 &` smtp_connection `& SMTP connections
34280 &` smtp_incomplete_transaction`& incomplete SMTP transactions
34281 &` smtp_mailauth `& AUTH argument to MAIL commands
34282 &` smtp_no_mail `& session with no MAIL commands
34283 &` smtp_protocol_error `& SMTP protocol errors
34284 &` smtp_syntax_error `& SMTP syntax errors
34285 &` subject `& contents of &'Subject:'& on <= lines
34286 &` tls_certificate_verified `& certificate verification status
34287 &`*tls_cipher `& TLS cipher suite on <= and => lines
34288 &` tls_peerdn `& TLS peer DN on <= and => lines
34289 &` tls_sni `& TLS SNI on <= lines
34290 &` unknown_in_list `& DNS lookup failed in list match
34291
34292 &` all `& all of the above
34293 .endd
34294 More details on each of these items follows:
34295
34296 .ilist
34297 .cindex "8BITMIME"
34298 .cindex "log" "8BITMIME"
34299 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
34300 which may help in tracking down interoperability issues with ancient MTAs
34301 that are not 8bit clean. This is added to the &"<="& line, tagged with
34302 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
34303 &`7BIT`& and &`8BITMIME`& respectively.
34304 .next
34305 .cindex "&%warn%& ACL verb" "log when skipping"
34306 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
34307 its conditions cannot be evaluated, a log line to this effect is written if
34308 this log selector is set.
34309 .next
34310 .cindex "log" "rewriting"
34311 .cindex "rewriting" "logging"
34312 &%address_rewrite%&: This applies both to global rewrites and per-transport
34313 rewrites, but not to rewrites in filters run as an unprivileged user (because
34314 such users cannot access the log).
34315 .next
34316 .cindex "log" "full parentage"
34317 &%all_parents%&: Normally only the original and final addresses are logged on
34318 delivery lines; with this selector, intermediate parents are given in
34319 parentheses between them.
34320 .next
34321 .cindex "log" "Exim arguments"
34322 .cindex "Exim arguments, logging"
34323 &%arguments%&: This causes Exim to write the arguments with which it was called
34324 to the main log, preceded by the current working directory. This is a debugging
34325 feature, added to make it easier to find out how certain MUAs call
34326 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
34327 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
34328 that are empty or that contain white space are quoted. Non-printing characters
34329 are shown as escape sequences. This facility cannot log unrecognized arguments,
34330 because the arguments are checked before the configuration file is read. The
34331 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
34332 between the caller and Exim.
34333 .next
34334 .cindex "log" "connection rejections"
34335 &%connection_reject%&: A log entry is written whenever an incoming SMTP
34336 connection is rejected, for whatever reason.
34337 .next
34338 .cindex "log" "delayed delivery"
34339 .cindex "delayed delivery, logging"
34340 &%delay_delivery%&: A log entry is written whenever a delivery process is not
34341 started for an incoming message because the load is too high or too many
34342 messages were received on one connection. Logging does not occur if no delivery
34343 process is started because &%queue_only%& is set or &%-odq%& was used.
34344 .next
34345 .cindex "log" "delivery duration"
34346 &%deliver_time%&: For each delivery, the amount of real time it has taken to
34347 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
34348 .next
34349 .cindex "log" "message size on delivery"
34350 .cindex "size" "of message"
34351 &%delivery_size%&: For each delivery, the size of message delivered is added to
34352 the &"=>"& line, tagged with S=.
34353 .next
34354 .cindex "log" "dnslist defer"
34355 .cindex "DNS list" "logging defer"
34356 .cindex "black list (DNS)"
34357 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
34358 DNS black list suffers a temporary error.
34359 .next
34360 .cindex "log" "ETRN commands"
34361 .cindex "ETRN" "logging"
34362 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
34363 is run to determine whether or not it is actually accepted. An invalid ETRN
34364 command, or one received within a message transaction is not logged by this
34365 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
34366 .next
34367 .cindex "log" "host lookup failure"
34368 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
34369 any addresses, or when a lookup of an IP address fails to find a host name, a
34370 log line is written. This logging does not apply to direct DNS lookups when
34371 routing email addresses, but it does apply to &"byname"& lookups.
34372 .next
34373 .cindex "log" "ident timeout"
34374 .cindex "RFC 1413" "logging timeout"
34375 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
34376 client's ident port times out.
34377 .next
34378 .cindex "log" "incoming interface"
34379 .cindex "interface" "logging"
34380 &%incoming_interface%&: The interface on which a message was received is added
34381 to the &"<="& line as an IP address in square brackets, tagged by I= and
34382 followed by a colon and the port number. The local interface and port are also
34383 added to other SMTP log lines, for example &"SMTP connection from"&, and to
34384 rejection lines.
34385 .next
34386 .cindex "log" "incoming remote port"
34387 .cindex "port" "logging remote"
34388 .cindex "TCP/IP" "logging incoming remote port"
34389 .vindex "&$sender_fullhost$&"
34390 .vindex "&$sender_rcvhost$&"
34391 &%incoming_port%&: The remote port number from which a message was received is
34392 added to log entries and &'Received:'& header lines, following the IP address
34393 in square brackets, and separated from it by a colon. This is implemented by
34394 changing the value that is put in the &$sender_fullhost$& and
34395 &$sender_rcvhost$& variables. Recording the remote port number has become more
34396 important with the widening use of NAT (see RFC 2505).
34397 .next
34398 .cindex "log" "dropped connection"
34399 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
34400 connection is unexpectedly dropped.
34401 .next
34402 .cindex "log" "outgoing remote port"
34403 .cindex "port" "logging outgoint remote"
34404 .cindex "TCP/IP" "logging ougtoing remote port"
34405 &%outgoing_port%&: The remote port number is added to delivery log lines (those
34406 containing => tags) following the IP address. This option is not included in
34407 the default setting, because for most ordinary configurations, the remote port
34408 number is always 25 (the SMTP port).
34409 .next
34410 .cindex "log" "process ids in"
34411 .cindex "pid (process id)" "in log lines"
34412 &%pid%&: The current process id is added to every log line, in square brackets,
34413 immediately after the time and date.
34414 .next
34415 .cindex "log" "queue run"
34416 .cindex "queue runner" "logging"
34417 &%queue_run%&: The start and end of every queue run are logged.
34418 .next
34419 .cindex "log" "queue time"
34420 &%queue_time%&: The amount of time the message has been in the queue on the
34421 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
34422 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
34423 includes reception time as well as the delivery time for the current address.
34424 This means that it may be longer than the difference between the arrival and
34425 delivery log line times, because the arrival log line is not written until the
34426 message has been successfully received.
34427 .next
34428 &%queue_time_overall%&: The amount of time the message has been in the queue on
34429 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
34430 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
34431 message, so it includes reception time as well as the total delivery time.
34432 .next
34433 .cindex "log" "recipients"
34434 &%received_recipients%&: The recipients of a message are listed in the main log
34435 as soon as the message is received. The list appears at the end of the log line
34436 that is written when a message is received, preceded by the word &"for"&. The
34437 addresses are listed after they have been qualified, but before any rewriting
34438 has taken place.
34439 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
34440 in the list.
34441 .next
34442 .cindex "log" "sender reception"
34443 &%received_sender%&: The unrewritten original sender of a message is added to
34444 the end of the log line that records the message's arrival, after the word
34445 &"from"& (before the recipients if &%received_recipients%& is also set).
34446 .next
34447 .cindex "log" "header lines for rejection"
34448 &%rejected_header%&: If a message's header has been received at the time a
34449 rejection is written to the reject log, the complete header is added to the
34450 log. Header logging can be turned off individually for messages that are
34451 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
34452 .next
34453 .cindex "log" "retry defer"
34454 &%retry_defer%&: A log line is written if a delivery is deferred because a
34455 retry time has not yet been reached. However, this &"retry time not reached"&
34456 message is always omitted from individual message logs after the first delivery
34457 attempt.
34458 .next
34459 .cindex "log" "return path"
34460 &%return_path_on_delivery%&: The return path that is being transmitted with
34461 the message is included in delivery and bounce lines, using the tag P=.
34462 This is omitted if no delivery actually happens, for example, if routing fails,
34463 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
34464 .next
34465 .cindex "log" "sender on delivery"
34466 &%sender_on_delivery%&: The message's sender address is added to every delivery
34467 and bounce line, tagged by F= (for &"from"&).
34468 This is the original sender that was received with the message; it is not
34469 necessarily the same as the outgoing return path.
34470 .next
34471 .cindex "log" "sender verify failure"
34472 &%sender_verify_fail%&: If this selector is unset, the separate log line that
34473 gives details of a sender verification failure is not written. Log lines for
34474 the rejection of SMTP commands contain just &"sender verify failed"&, so some
34475 detail is lost.
34476 .next
34477 .cindex "log" "size rejection"
34478 &%size_reject%&: A log line is written whenever a message is rejected because
34479 it is too big.
34480 .next
34481 .cindex "log" "frozen messages; skipped"
34482 .cindex "frozen messages" "logging skipping"
34483 &%skip_delivery%&: A log line is written whenever a message is skipped during a
34484 queue run because it is frozen or because another process is already delivering
34485 it.
34486 .cindex "&""spool file is locked""&"
34487 The message that is written is &"spool file is locked"&.
34488 .next
34489 .cindex "log" "smtp confirmation"
34490 .cindex "SMTP" "logging confirmation"
34491 .cindex "LMTP" "logging confirmation"
34492 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
34493 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
34494 A number of MTAs (including Exim) return an identifying string in this
34495 response.
34496 .next
34497 .cindex "log" "SMTP connections"
34498 .cindex "SMTP" "logging connections"
34499 &%smtp_connection%&: A log line is written whenever an SMTP connection is
34500 established or closed, unless the connection is from a host that matches
34501 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
34502 only when the closure is unexpected.) This applies to connections from local
34503 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
34504 dropped in the middle of a message, a log line is always written, whether or
34505 not this selector is set, but otherwise nothing is written at the start and end
34506 of connections unless this selector is enabled.
34507
34508 For TCP/IP connections to an Exim daemon, the current number of connections is
34509 included in the log message for each new connection, but note that the count is
34510 reset if the daemon is restarted.
34511 Also, because connections are closed (and the closure is logged) in
34512 subprocesses, the count may not include connections that have been closed but
34513 whose termination the daemon has not yet noticed. Thus, while it is possible to
34514 match up the opening and closing of connections in the log, the value of the
34515 logged counts may not be entirely accurate.
34516 .next
34517 .cindex "log" "SMTP transaction; incomplete"
34518 .cindex "SMTP" "logging incomplete transactions"
34519 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
34520 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
34521 and the message sender plus any accepted recipients are included in the log
34522 line. This can provide evidence of dictionary attacks.
34523 .next
34524 .cindex "log" "non-MAIL SMTP sessions"
34525 .cindex "MAIL" "logging session without"
34526 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
34527 connection terminates without having issued a MAIL command. This includes both
34528 the case when the connection is dropped, and the case when QUIT is used. It
34529 does not include cases where the connection is rejected right at the start (by
34530 an ACL, or because there are too many connections, or whatever). These cases
34531 already have their own log lines.
34532
34533 The log line that is written contains the identity of the client in the usual
34534 way, followed by D= and a time, which records the duration of the connection.
34535 If the connection was authenticated, this fact is logged exactly as it is for
34536 an incoming message, with an A= item. If the connection was encrypted, CV=,
34537 DN=, and X= items may appear as they do for an incoming message, controlled by
34538 the same logging options.
34539
34540 Finally, if any SMTP commands were issued during the connection, a C= item
34541 is added to the line, listing the commands that were used. For example,
34542 .code
34543 C=EHLO,QUIT
34544 .endd
34545 shows that the client issued QUIT straight after EHLO. If there were fewer
34546 than 20 commands, they are all listed. If there were more than 20 commands,
34547 the last 20 are listed, preceded by &"..."&. However, with the default
34548 setting of 10 for &%smtp_accep_max_nonmail%&, the connection will in any case
34549 have been aborted before 20 non-mail commands are processed.
34550 .next
34551 &%smtp_mailauth%&: A third subfield with the authenticated sender,
34552 colon-separated, is appended to the A= item for a message arrival or delivery
34553 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
34554 was accepted or used.
34555 .next
34556 .cindex "log" "SMTP protocol error"
34557 .cindex "SMTP" "logging protocol error"
34558 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
34559 encountered. Exim does not have perfect detection of all protocol errors
34560 because of transmission delays and the use of pipelining. If PIPELINING has
34561 been advertised to a client, an Exim server assumes that the client will use
34562 it, and therefore it does not count &"expected"& errors (for example, RCPT
34563 received after rejecting MAIL) as protocol errors.
34564 .next
34565 .cindex "SMTP" "logging syntax errors"
34566 .cindex "SMTP" "syntax errors; logging"
34567 .cindex "SMTP" "unknown command; logging"
34568 .cindex "log" "unknown SMTP command"
34569 .cindex "log" "SMTP syntax error"
34570 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
34571 encountered. An unrecognized command is treated as a syntax error. For an
34572 external connection, the host identity is given; for an internal connection
34573 using &%-bs%& the sender identification (normally the calling user) is given.
34574 .next
34575 .cindex "log" "subject"
34576 .cindex "subject, logging"
34577 &%subject%&: The subject of the message is added to the arrival log line,
34578 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
34579 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
34580 specifies whether characters with values greater than 127 should be logged
34581 unchanged, or whether they should be rendered as escape sequences.
34582 .next
34583 .cindex "log" "certificate verification"
34584 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
34585 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
34586 verified, and &`CV=no`& if not.
34587 .next
34588 .cindex "log" "TLS cipher"
34589 .cindex "TLS" "logging cipher"
34590 &%tls_cipher%&: When a message is sent or received over an encrypted
34591 connection, the cipher suite used is added to the log line, preceded by X=.
34592 .next
34593 .cindex "log" "TLS peer DN"
34594 .cindex "TLS" "logging peer DN"
34595 &%tls_peerdn%&: When a message is sent or received over an encrypted
34596 connection, and a certificate is supplied by the remote host, the peer DN is
34597 added to the log line, preceded by DN=.
34598 .next
34599 .cindex "log" "TLS SNI"
34600 .cindex "TLS" "logging SNI"
34601 &%tls_sni%&: When a message is received over an encrypted connection, and
34602 the remote host provided the Server Name Indication extension, the SNI is
34603 added to the log line, preceded by SNI=.
34604 .next
34605 .cindex "log" "DNS failure in list"
34606 &%unknown_in_list%&: This setting causes a log entry to be written when the
34607 result of a list match is failure because a DNS lookup failed.
34608 .endlist
34609
34610
34611 .section "Message log" "SECID260"
34612 .cindex "message" "log file for"
34613 .cindex "log" "message log; description of"
34614 .cindex "&_msglog_& directory"
34615 .oindex "&%preserve_message_logs%&"
34616 In addition to the general log files, Exim writes a log file for each message
34617 that it handles. The names of these per-message logs are the message ids, and
34618 they are kept in the &_msglog_& sub-directory of the spool directory. Each
34619 message log contains copies of the log lines that apply to the message. This
34620 makes it easier to inspect the status of an individual message without having
34621 to search the main log. A message log is deleted when processing of the message
34622 is complete, unless &%preserve_message_logs%& is set, but this should be used
34623 only with great care because they can fill up your disk very quickly.
34624
34625 On a heavily loaded system, it may be desirable to disable the use of
34626 per-message logs, in order to reduce disk I/O. This can be done by setting the
34627 &%message_logs%& option false.
34628 .ecindex IIDloggen
34629
34630
34631
34632
34633 . ////////////////////////////////////////////////////////////////////////////
34634 . ////////////////////////////////////////////////////////////////////////////
34635
34636 .chapter "Exim utilities" "CHAPutils"
34637 .scindex IIDutils "utilities"
34638 A number of utility scripts and programs are supplied with Exim and are
34639 described in this chapter. There is also the Exim Monitor, which is covered in
34640 the next chapter. The utilities described here are:
34641
34642 .itable none 0 0 3 7* left 15* left 40* left
34643 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
34644 "list what Exim processes are doing"
34645 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
34646 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
34647 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
34648 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
34649 various criteria"
34650 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
34651 .irow &<<SECTmailstat>>& &'eximstats'& &&&
34652 "extract statistics from the log"
34653 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
34654 "check address acceptance from given IP"
34655 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
34656 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
34657 .irow &<<SECThindatmai>>& &'exim_dumpdb'& "dump a hints database"
34658 .irow &<<SECThindatmai>>& &'exim_tidydb'& "clean up a hints database"
34659 .irow &<<SECThindatmai>>& &'exim_fixdb'& "patch a hints database"
34660 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
34661 .endtable
34662
34663 Another utility that might be of use to sites with many MTAs is Tom Kistner's
34664 &'exilog'&. It provides log visualizations across multiple Exim servers. See
34665 &url(http://duncanthrax.net/exilog/) for details.
34666
34667
34668
34669
34670 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
34671 .cindex "&'exiwhat'&"
34672 .cindex "process, querying"
34673 .cindex "SIGUSR1"
34674 On operating systems that can restart a system call after receiving a signal
34675 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
34676 a line describing what it is doing to the file &_exim-process.info_& in the
34677 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
34678 processes it can find, having first emptied the file. It then waits for one
34679 second to allow the Exim processes to react before displaying the results. In
34680 order to run &'exiwhat'& successfully you have to have sufficient privilege to
34681 send the signal to the Exim processes, so it is normally run as root.
34682
34683 &*Warning*&: This is not an efficient process. It is intended for occasional
34684 use by system administrators. It is not sensible, for example, to set up a
34685 script that sends SIGUSR1 signals to Exim processes at short intervals.
34686
34687
34688 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
34689 varies in different operating systems. Not only are different options used,
34690 but the format of the output is different. For this reason, there are some
34691 system configuration options that configure exactly how &'exiwhat'& works. If
34692 it doesn't seem to be working for you, check the following compile-time
34693 options:
34694 .display
34695 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
34696 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
34697 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
34698 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
34699 .endd
34700 An example of typical output from &'exiwhat'& is
34701 .code
34702 164 daemon: -q1h, listening on port 25
34703 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
34704 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
34705 [10.19.42.42] (editor@ref.example)
34706 10592 handling incoming call from [192.168.243.242]
34707 10628 accepting a local non-SMTP message
34708 .endd
34709 The first number in the output line is the process number. The third line has
34710 been split here, in order to fit it on the page.
34711
34712
34713
34714 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
34715 .cindex "&'exiqgrep'&"
34716 .cindex "queue" "grepping"
34717 This utility is a Perl script contributed by Matt Hubbard. It runs
34718 .code
34719 exim -bpu
34720 .endd
34721 or (in case &*-a*& switch is specified)
34722 .code
34723 exim -bp
34724 .endd
34725 .new
34726 The &*-C*& option is used to specify an alternate &_exim.conf_& which might
34727 contain alternate exim configuration the queue management might be using.
34728 .wen
34729
34730 to obtain a queue listing, and then greps the output to select messages
34731 that match given criteria. The following selection options are available:
34732
34733 .vlist
34734 .vitem &*-f*&&~<&'regex'&>
34735 Match the sender address using a case-insensitive search. The field that is
34736 tested is enclosed in angle brackets, so you can test for bounce messages with
34737 .code
34738 exiqgrep -f '^<>$'
34739 .endd
34740 .vitem &*-r*&&~<&'regex'&>
34741 Match a recipient address using a case-insensitve search. The field that is
34742 tested is not enclosed in angle brackets.
34743
34744 .vitem &*-s*&&~<&'regex'&>
34745 Match against the size field.
34746
34747 .vitem &*-y*&&~<&'seconds'&>
34748 Match messages that are younger than the given time.
34749
34750 .vitem &*-o*&&~<&'seconds'&>
34751 Match messages that are older than the given time.
34752
34753 .vitem &*-z*&
34754 Match only frozen messages.
34755
34756 .vitem &*-x*&
34757 Match only non-frozen messages.
34758 .endlist
34759
34760 The following options control the format of the output:
34761
34762 .vlist
34763 .vitem &*-c*&
34764 Display only the count of matching messages.
34765
34766 .vitem &*-l*&
34767 Long format &-- display the full message information as output by Exim. This is
34768 the default.
34769
34770 .vitem &*-i*&
34771 Display message ids only.
34772
34773 .vitem &*-b*&
34774 Brief format &-- one line per message.
34775
34776 .vitem &*-R*&
34777 Display messages in reverse order.
34778
34779 .vitem &*-a*&
34780 Include delivered recipients in queue listing.
34781 .endlist
34782
34783 There is one more option, &%-h%&, which outputs a list of options.
34784
34785
34786
34787 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
34788 .cindex "&'exiqsumm'&"
34789 .cindex "queue" "summary"
34790 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
34791 -bp`& and produces a summary of the messages on the queue. Thus, you use it by
34792 running a command such as
34793 .code
34794 exim -bp | exiqsumm
34795 .endd
34796 The output consists of one line for each domain that has messages waiting for
34797 it, as in the following example:
34798 .code
34799 3 2322 74m 66m msn.com.example
34800 .endd
34801 Each line lists the number of pending deliveries for a domain, their total
34802 volume, and the length of time that the oldest and the newest messages have
34803 been waiting. Note that the number of pending deliveries is greater than the
34804 number of messages when messages have more than one recipient.
34805
34806 A summary line is output at the end. By default the output is sorted on the
34807 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
34808 the output to be sorted by oldest message and by count of messages,
34809 respectively. There are also three options that split the messages for each
34810 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
34811 separates frozen messages, and &%-s%& separates messages according to their
34812 sender.
34813
34814 The output of &'exim -bp'& contains the original addresses in the message, so
34815 this also applies to the output from &'exiqsumm'&. No domains from addresses
34816 generated by aliasing or forwarding are included (unless the &%one_time%&
34817 option of the &(redirect)& router has been used to convert them into &"top
34818 level"& addresses).
34819
34820
34821
34822
34823 .section "Extracting specific information from the log (exigrep)" &&&
34824 "SECTextspeinf"
34825 .cindex "&'exigrep'&"
34826 .cindex "log" "extracts; grepping for"
34827 The &'exigrep'& utility is a Perl script that searches one or more main log
34828 files for entries that match a given pattern. When it finds a match, it
34829 extracts all the log entries for the relevant message, not just those that
34830 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
34831 given message, or all mail for a given user, or for a given host, for example.
34832 The input files can be in Exim log format or syslog format.
34833 If a matching log line is not associated with a specific message, it is
34834 included in &'exigrep'&'s output without any additional lines. The usage is:
34835 .display
34836 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
34837 .endd
34838 If no log file names are given on the command line, the standard input is read.
34839
34840 The &%-t%& argument specifies a number of seconds. It adds an additional
34841 condition for message selection. Messages that are complete are shown only if
34842 they spent more than <&'n'&> seconds on the queue.
34843
34844 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
34845 makes it case-sensitive. This may give a performance improvement when searching
34846 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
34847 option; with &%-I%& they do not. In both cases it is possible to change the
34848 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
34849
34850 The &%-l%& option means &"literal"&, that is, treat all characters in the
34851 pattern as standing for themselves. Otherwise the pattern must be a Perl
34852 regular expression.
34853
34854 The &%-v%& option inverts the matching condition. That is, a line is selected
34855 if it does &'not'& match the pattern.
34856
34857 If the location of a &'zcat'& command is known from the definition of
34858 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
34859 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
34860
34861
34862 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
34863 .cindex "&'exipick'&"
34864 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
34865 lists messages from the queue according to a variety of criteria. For details
34866 of &'exipick'&'s facilities, visit the web page at
34867 &url(http://www.exim.org/eximwiki/ToolExipickManPage) or run &'exipick'& with
34868 the &%--help%& option.
34869
34870
34871 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
34872 .cindex "log" "cycling local files"
34873 .cindex "cycling logs"
34874 .cindex "&'exicyclog'&"
34875 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
34876 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
34877 you are using log files with datestamps in their names (see section
34878 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
34879 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
34880 There are two command line options for &'exicyclog'&:
34881 .ilist
34882 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
34883 default that is set when Exim is built. The default default is 10.
34884 .next
34885 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
34886 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
34887 overriding the script's default, which is to find the setting from Exim's
34888 configuration.
34889 .endlist
34890
34891 Each time &'exicyclog'& is run the file names get &"shuffled down"& by one. If
34892 the main log file name is &_mainlog_& (the default) then when &'exicyclog'& is
34893 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
34894 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
34895 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
34896 logs are handled similarly.
34897
34898 If the limit is greater than 99, the script uses 3-digit numbers such as
34899 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
34900 to one that is greater, or &'vice versa'&, you will have to fix the names of
34901 any existing log files.
34902
34903 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
34904 the end are deleted. All files with numbers greater than 01 are compressed,
34905 using a compression command which is configured by the COMPRESS_COMMAND
34906 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
34907 root &%crontab%& entry of the form
34908 .code
34909 1 0 * * * su exim -c /usr/exim/bin/exicyclog
34910 .endd
34911 assuming you have used the name &"exim"& for the Exim user. You can run
34912 &'exicyclog'& as root if you wish, but there is no need.
34913
34914
34915
34916 .section "Mail statistics (eximstats)" "SECTmailstat"
34917 .cindex "statistics"
34918 .cindex "&'eximstats'&"
34919 A Perl script called &'eximstats'& is provided for extracting statistical
34920 information from log files. The output is either plain text, or HTML.
34921 Exim log files are also supported by the &'Lire'& system produced by the
34922 LogReport Foundation &url(http://www.logreport.org).
34923
34924 The &'eximstats'& script has been hacked about quite a bit over time. The
34925 latest version is the result of some extensive revision by Steve Campbell. A
34926 lot of information is given by default, but there are options for suppressing
34927 various parts of it. Following any options, the arguments to the script are a
34928 list of files, which should be main log files. For example:
34929 .code
34930 eximstats -nr /var/spool/exim/log/mainlog.01
34931 .endd
34932 By default, &'eximstats'& extracts information about the number and volume of
34933 messages received from or delivered to various hosts. The information is sorted
34934 both by message count and by volume, and the top fifty hosts in each category
34935 are listed on the standard output. Similar information, based on email
34936 addresses or domains instead of hosts can be requested by means of various
34937 options. For messages delivered and received locally, similar statistics are
34938 also produced per user.
34939
34940 The output also includes total counts and statistics about delivery errors, and
34941 histograms showing the number of messages received and deliveries made in each
34942 hour of the day. A delivery with more than one address in its envelope (for
34943 example, an SMTP transaction with more than one RCPT command) is counted
34944 as a single delivery by &'eximstats'&.
34945
34946 Though normally more deliveries than receipts are reported (as messages may
34947 have multiple recipients), it is possible for &'eximstats'& to report more
34948 messages received than delivered, even though the queue is empty at the start
34949 and end of the period in question. If an incoming message contains no valid
34950 recipients, no deliveries are recorded for it. A bounce message is handled as
34951 an entirely separate message.
34952
34953 &'eximstats'& always outputs a grand total summary giving the volume and number
34954 of messages received and deliveries made, and the number of hosts involved in
34955 each case. It also outputs the number of messages that were delayed (that is,
34956 not completely delivered at the first attempt), and the number that had at
34957 least one address that failed.
34958
34959 The remainder of the output is in sections that can be independently disabled
34960 or modified by various options. It consists of a summary of deliveries by
34961 transport, histograms of messages received and delivered per time interval
34962 (default per hour), information about the time messages spent on the queue,
34963 a list of relayed messages, lists of the top fifty sending hosts, local
34964 senders, destination hosts, and destination local users by count and by volume,
34965 and a list of delivery errors that occurred.
34966
34967 The relay information lists messages that were actually relayed, that is, they
34968 came from a remote host and were directly delivered to some other remote host,
34969 without being processed (for example, for aliasing or forwarding) locally.
34970
34971 There are quite a few options for &'eximstats'& to control exactly what it
34972 outputs. These are documented in the Perl script itself, and can be extracted
34973 by running the command &(perldoc)& on the script. For example:
34974 .code
34975 perldoc /usr/exim/bin/eximstats
34976 .endd
34977
34978 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
34979 .cindex "&'exim_checkaccess'&"
34980 .cindex "policy control" "checking access"
34981 .cindex "checking access"
34982 The &%-bh%& command line argument allows you to run a fake SMTP session with
34983 debugging output, in order to check what Exim is doing when it is applying
34984 policy controls to incoming SMTP mail. However, not everybody is sufficiently
34985 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
34986 sometimes you just want to answer the question &"Does this address have
34987 access?"& without bothering with any further details.
34988
34989 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
34990 two arguments, an IP address and an email address:
34991 .code
34992 exim_checkaccess 10.9.8.7 A.User@a.domain.example
34993 .endd
34994 The utility runs a call to Exim with the &%-bh%& option, to test whether the
34995 given email address would be accepted in a RCPT command in a TCP/IP
34996 connection from the host with the given IP address. The output of the utility
34997 is either the word &"accepted"&, or the SMTP error response, for example:
34998 .code
34999 Rejected:
35000 550 Relay not permitted
35001 .endd
35002 When running this test, the utility uses &`<>`& as the envelope sender address
35003 for the MAIL command, but you can change this by providing additional
35004 options. These are passed directly to the Exim command. For example, to specify
35005 that the test is to be run with the sender address &'himself@there.example'&
35006 you can use:
35007 .code
35008 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
35009 -f himself@there.example
35010 .endd
35011 Note that these additional Exim command line items must be given after the two
35012 mandatory arguments.
35013
35014 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
35015 while running its checks. You can run checks that include callouts by using
35016 &%-bhc%&, but this is not yet available in a &"packaged"& form.
35017
35018
35019
35020 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
35021 .cindex "DBM" "building dbm files"
35022 .cindex "building DBM files"
35023 .cindex "&'exim_dbmbuild'&"
35024 .cindex "lower casing"
35025 .cindex "binary zero" "in lookup key"
35026 The &'exim_dbmbuild'& program reads an input file containing keys and data in
35027 the format used by the &(lsearch)& lookup (see section
35028 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
35029 names as keys and the remainder of the information as data. The lower-casing
35030 can be prevented by calling the program with the &%-nolc%& option.
35031
35032 A terminating zero is included as part of the key string. This is expected by
35033 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
35034 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
35035 strings or the data strings. The &(dbmnz)& lookup type can be used with such
35036 files.
35037
35038 The program requires two arguments: the name of the input file (which can be a
35039 single hyphen to indicate the standard input), and the name of the output file.
35040 It creates the output under a temporary name, and then renames it if all went
35041 well.
35042
35043 .cindex "USE_DB"
35044 If the native DB interface is in use (USE_DB is set in a compile-time
35045 configuration file &-- this is common in free versions of Unix) the two file
35046 names must be different, because in this mode the Berkeley DB functions create
35047 a single output file using exactly the name given. For example,
35048 .code
35049 exim_dbmbuild /etc/aliases /etc/aliases.db
35050 .endd
35051 reads the system alias file and creates a DBM version of it in
35052 &_/etc/aliases.db_&.
35053
35054 In systems that use the &'ndbm'& routines (mostly proprietary versions of
35055 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
35056 environment, the suffixes are added to the second argument of
35057 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
35058 when the Berkeley functions are used in compatibility mode (though this is not
35059 recommended), because in that case it adds a &_.db_& suffix to the file name.
35060
35061 If a duplicate key is encountered, the program outputs a warning, and when it
35062 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
35063 option is used. By default, only the first of a set of duplicates is used &--
35064 this makes it compatible with &(lsearch)& lookups. There is an option
35065 &%-lastdup%& which causes it to use the data for the last duplicate instead.
35066 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
35067 &%stderr%&. For other errors, where it doesn't actually make a new file, the
35068 return code is 2.
35069
35070
35071
35072
35073 .section "Finding individual retry times (exinext)" "SECTfinindret"
35074 .cindex "retry" "times"
35075 .cindex "&'exinext'&"
35076 A utility called &'exinext'& (mostly a Perl script) provides the ability to
35077 fish specific information out of the retry database. Given a mail domain (or a
35078 complete address), it looks up the hosts for that domain, and outputs any retry
35079 information for the hosts or for the domain. At present, the retry information
35080 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
35081 output. For example:
35082 .code
35083 $ exinext piglet@milne.fict.example
35084 kanga.milne.example:192.168.8.1 error 146: Connection refused
35085 first failed: 21-Feb-1996 14:57:34
35086 last tried: 21-Feb-1996 14:57:34
35087 next try at: 21-Feb-1996 15:02:34
35088 roo.milne.example:192.168.8.3 error 146: Connection refused
35089 first failed: 20-Jan-1996 13:12:08
35090 last tried: 21-Feb-1996 11:42:03
35091 next try at: 21-Feb-1996 19:42:03
35092 past final cutoff time
35093 .endd
35094 You can also give &'exinext'& a local part, without a domain, and it
35095 will give any retry information for that local part in your default domain.
35096 A message id can be used to obtain retry information pertaining to a specific
35097 message. This exists only when an attempt to deliver a message to a remote host
35098 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
35099 &'exinext'& is not particularly efficient, but then it is not expected to be
35100 run very often.
35101
35102 The &'exinext'& utility calls Exim to find out information such as the location
35103 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
35104 passed on to the &'exim'& commands. The first specifies an alternate Exim
35105 configuration file, and the second sets macros for use within the configuration
35106 file. These features are mainly to help in testing, but might also be useful in
35107 environments where more than one configuration file is in use.
35108
35109
35110
35111 .section "Hints database maintenance" "SECThindatmai"
35112 .cindex "hints database" "maintenance"
35113 .cindex "maintaining Exim's hints database"
35114 Three utility programs are provided for maintaining the DBM files that Exim
35115 uses to contain its delivery hint information. Each program requires two
35116 arguments. The first specifies the name of Exim's spool directory, and the
35117 second is the name of the database it is to operate on. These are as follows:
35118
35119 .ilist
35120 &'retry'&: the database of retry information
35121 .next
35122 &'wait-'&<&'transport name'&>: databases of information about messages waiting
35123 for remote hosts
35124 .next
35125 &'callout'&: the callout cache
35126 .next
35127 &'ratelimit'&: the data for implementing the ratelimit ACL condition
35128 .next
35129 &'misc'&: other hints data
35130 .endlist
35131
35132 The &'misc'& database is used for
35133
35134 .ilist
35135 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
35136 .next
35137 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
35138 &(smtp)& transport)
35139 .endlist
35140
35141
35142
35143 .section "exim_dumpdb" "SECID261"
35144 .cindex "&'exim_dumpdb'&"
35145 The entire contents of a database are written to the standard output by the
35146 &'exim_dumpdb'& program, which has no options or arguments other than the
35147 spool and database names. For example, to dump the retry database:
35148 .code
35149 exim_dumpdb /var/spool/exim retry
35150 .endd
35151 Two lines of output are produced for each entry:
35152 .code
35153 T:mail.ref.example:192.168.242.242 146 77 Connection refused
35154 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
35155 .endd
35156 The first item on the first line is the key of the record. It starts with one
35157 of the letters R, or T, depending on whether it refers to a routing or
35158 transport retry. For a local delivery, the next part is the local address; for
35159 a remote delivery it is the name of the remote host, followed by its failing IP
35160 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
35161 transport). If the remote port is not the standard one (port 25), it is added
35162 to the IP address. Then there follows an error code, an additional error code,
35163 and a textual description of the error.
35164
35165 The three times on the second line are the time of first failure, the time of
35166 the last delivery attempt, and the computed time for the next attempt. The line
35167 ends with an asterisk if the cutoff time for the last retry rule has been
35168 exceeded.
35169
35170 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
35171 consists of a host name followed by a list of ids for messages that are or were
35172 waiting to be delivered to that host. If there are a very large number for any
35173 one host, continuation records, with a sequence number added to the host name,
35174 may be seen. The data in these records is often out of date, because a message
35175 may be routed to several alternative hosts, and Exim makes no effort to keep
35176 cross-references.
35177
35178
35179
35180 .section "exim_tidydb" "SECID262"
35181 .cindex "&'exim_tidydb'&"
35182 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
35183 database. If run with no options, it removes all records that are more than 30
35184 days old. The age is calculated from the date and time that the record was last
35185 updated. Note that, in the case of the retry database, it is &'not'& the time
35186 since the first delivery failure. Information about a host that has been down
35187 for more than 30 days will remain in the database, provided that the record is
35188 updated sufficiently often.
35189
35190 The cutoff date can be altered by means of the &%-t%& option, which must be
35191 followed by a time. For example, to remove all records older than a week from
35192 the retry database:
35193 .code
35194 exim_tidydb -t 7d /var/spool/exim retry
35195 .endd
35196 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
35197 message ids. In the former these appear as data in records keyed by host &--
35198 they were messages that were waiting for that host &-- and in the latter they
35199 are the keys for retry information for messages that have suffered certain
35200 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
35201 message ids in database records are those of messages that are still on the
35202 queue. Message ids for messages that no longer exist are removed from
35203 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
35204 For the &'retry'& database, records whose keys are non-existent message ids are
35205 removed. The &'exim_tidydb'& utility outputs comments on the standard output
35206 whenever it removes information from the database.
35207
35208 Certain records are automatically removed by Exim when they are no longer
35209 needed, but others are not. For example, if all the MX hosts for a domain are
35210 down, a retry record is created for each one. If the primary MX host comes back
35211 first, its record is removed when Exim successfully delivers to it, but the
35212 records for the others remain because Exim has not tried to use those hosts.
35213
35214 It is important, therefore, to run &'exim_tidydb'& periodically on all the
35215 hints databases. You should do this at a quiet time of day, because it requires
35216 a database to be locked (and therefore inaccessible to Exim) while it does its
35217 work. Removing records from a DBM file does not normally make the file smaller,
35218 but all the common DBM libraries are able to re-use the space that is released.
35219 After an initial phase of increasing in size, the databases normally reach a
35220 point at which they no longer get any bigger, as long as they are regularly
35221 tidied.
35222
35223 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
35224 databases is likely to keep on increasing.
35225
35226
35227
35228
35229 .section "exim_fixdb" "SECID263"
35230 .cindex "&'exim_fixdb'&"
35231 The &'exim_fixdb'& program is a utility for interactively modifying databases.
35232 Its main use is for testing Exim, but it might also be occasionally useful for
35233 getting round problems in a live system. It has no options, and its interface
35234 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
35235 key of a database record can then be entered, and the data for that record is
35236 displayed.
35237
35238 If &"d"& is typed at the next prompt, the entire record is deleted. For all
35239 except the &'retry'& database, that is the only operation that can be carried
35240 out. For the &'retry'& database, each field is output preceded by a number, and
35241 data for individual fields can be changed by typing the field number followed
35242 by new data, for example:
35243 .code
35244 > 4 951102:1000
35245 .endd
35246 resets the time of the next delivery attempt. Time values are given as a
35247 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
35248 used as optional separators.
35249
35250
35251
35252
35253 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
35254 .cindex "mailbox" "maintenance"
35255 .cindex "&'exim_lock'&"
35256 .cindex "locking mailboxes"
35257 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
35258 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
35259 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
35260 a user agent while investigating a problem. The utility requires the name of
35261 the file as its first argument. If the locking is successful, the second
35262 argument is run as a command (using C's &[system()]& function); if there is no
35263 second argument, the value of the SHELL environment variable is used; if this
35264 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
35265 is unlocked and the utility ends. The following options are available:
35266
35267 .vlist
35268 .vitem &%-fcntl%&
35269 Use &[fcntl()]& locking on the open mailbox.
35270
35271 .vitem &%-flock%&
35272 Use &[flock()]& locking on the open mailbox, provided the operating system
35273 supports it.
35274
35275 .vitem &%-interval%&
35276 This must be followed by a number, which is a number of seconds; it sets the
35277 interval to sleep between retries (default 3).
35278
35279 .vitem &%-lockfile%&
35280 Create a lock file before opening the mailbox.
35281
35282 .vitem &%-mbx%&
35283 Lock the mailbox using MBX rules.
35284
35285 .vitem &%-q%&
35286 Suppress verification output.
35287
35288 .vitem &%-retries%&
35289 This must be followed by a number; it sets the number of times to try to get
35290 the lock (default 10).
35291
35292 .vitem &%-restore_time%&
35293 This option causes &%exim_lock%& to restore the modified and read times to the
35294 locked file before exiting. This allows you to access a locked mailbox (for
35295 example, to take a backup copy) without disturbing the times that the user
35296 subsequently sees.
35297
35298 .vitem &%-timeout%&
35299 This must be followed by a number, which is a number of seconds; it sets a
35300 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
35301 default), a non-blocking call is used.
35302
35303 .vitem &%-v%&
35304 Generate verbose output.
35305 .endlist
35306
35307 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
35308 default is to create a lock file and also to use &[fcntl()]& locking on the
35309 mailbox, which is the same as Exim's default. The use of &%-flock%& or
35310 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
35311 requires that the directory containing the file be writeable. Locking by lock
35312 file does not last for ever; Exim assumes that a lock file is expired if it is
35313 more than 30 minutes old.
35314
35315 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
35316 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
35317 to be taken out on the open mailbox, and an exclusive lock on the file
35318 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
35319 number of the mailbox file. When the locking is released, if an exclusive lock
35320 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
35321
35322 The default output contains verification of the locking that takes place. The
35323 &%-v%& option causes some additional information to be given. The &%-q%& option
35324 suppresses all output except error messages.
35325
35326 A command such as
35327 .code
35328 exim_lock /var/spool/mail/spqr
35329 .endd
35330 runs an interactive shell while the file is locked, whereas
35331 .display
35332 &`exim_lock -q /var/spool/mail/spqr <<End`&
35333 <&'some commands'&>
35334 &`End`&
35335 .endd
35336 runs a specific non-interactive sequence of commands while the file is locked,
35337 suppressing all verification output. A single command can be run by a command
35338 such as
35339 .code
35340 exim_lock -q /var/spool/mail/spqr \
35341 "cp /var/spool/mail/spqr /some/where"
35342 .endd
35343 Note that if a command is supplied, it must be entirely contained within the
35344 second argument &-- hence the quotes.
35345 .ecindex IIDutils
35346
35347
35348 . ////////////////////////////////////////////////////////////////////////////
35349 . ////////////////////////////////////////////////////////////////////////////
35350
35351 .chapter "The Exim monitor" "CHAPeximon"
35352 .scindex IIDeximon "Exim monitor" "description"
35353 .cindex "X-windows"
35354 .cindex "&'eximon'&"
35355 .cindex "Local/eximon.conf"
35356 .cindex "&_exim_monitor/EDITME_&"
35357 The Exim monitor is an application which displays in an X window information
35358 about the state of Exim's queue and what Exim is doing. An admin user can
35359 perform certain operations on messages from this GUI interface; however all
35360 such facilities are also available from the command line, and indeed, the
35361 monitor itself makes use of the command line to perform any actions requested.
35362
35363
35364
35365 .section "Running the monitor" "SECID264"
35366 The monitor is started by running the script called &'eximon'&. This is a shell
35367 script that sets up a number of environment variables, and then runs the
35368 binary called &_eximon.bin_&. The default appearance of the monitor window can
35369 be changed by editing the &_Local/eximon.conf_& file created by editing
35370 &_exim_monitor/EDITME_&. Comments in that file describe what the various
35371 parameters are for.
35372
35373 The parameters that get built into the &'eximon'& script can be overridden for
35374 a particular invocation by setting up environment variables of the same names,
35375 preceded by &`EXIMON_`&. For example, a shell command such as
35376 .code
35377 EXIMON_LOG_DEPTH=400 eximon
35378 .endd
35379 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
35380 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
35381 overrides the Exim log file configuration. This makes it possible to have
35382 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
35383 syslog messages are routed to a file on the local host.
35384
35385 X resources can be used to change the appearance of the window in the normal
35386 way. For example, a resource setting of the form
35387 .code
35388 Eximon*background: gray94
35389 .endd
35390 changes the colour of the background to light grey rather than white. The
35391 stripcharts are drawn with both the data lines and the reference lines in
35392 black. This means that the reference lines are not visible when on top of the
35393 data. However, their colour can be changed by setting a resource called
35394 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
35395 For example, if your X server is running Unix, you could set up lighter
35396 reference lines in the stripcharts by obeying
35397 .code
35398 xrdb -merge <<End
35399 Eximon*highlight: gray
35400 End
35401 .endd
35402 .cindex "admin user"
35403 In order to see the contents of messages on the queue, and to operate on them,
35404 &'eximon'& must either be run as root or by an admin user.
35405
35406 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
35407 contain X11 resource parameters interpreted by the X11 library. In addition,
35408 if the first parameter starts with the string "gdb" then it is removed and the
35409 binary is invoked under gdb (the parameter is used as the gdb command-name, so
35410 versioned variants of gdb can be invoked).
35411
35412 The monitor's window is divided into three parts. The first contains one or
35413 more stripcharts and two action buttons, the second contains a &"tail"& of the
35414 main log file, and the third is a display of the queue of messages awaiting
35415 delivery, with two more action buttons. The following sections describe these
35416 different parts of the display.
35417
35418
35419
35420
35421 .section "The stripcharts" "SECID265"
35422 .cindex "stripchart"
35423 The first stripchart is always a count of messages on the queue. Its name can
35424 be configured by setting QUEUE_STRIPCHART_NAME in the
35425 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
35426 configuration script by regular expression matches on log file entries, making
35427 it possible to display, for example, counts of messages delivered to certain
35428 hosts or using certain transports. The supplied defaults display counts of
35429 received and delivered messages, and of local and SMTP deliveries. The default
35430 period between stripchart updates is one minute; this can be adjusted by a
35431 parameter in the &_Local/eximon.conf_& file.
35432
35433 The stripchart displays rescale themselves automatically as the value they are
35434 displaying changes. There are always 10 horizontal lines in each chart; the
35435 title string indicates the value of each division when it is greater than one.
35436 For example, &"x2"& means that each division represents a value of 2.
35437
35438 It is also possible to have a stripchart which shows the percentage fullness of
35439 a particular disk partition, which is useful when local deliveries are confined
35440 to a single partition.
35441
35442 .cindex "&%statvfs%& function"
35443 This relies on the availability of the &[statvfs()]& function or equivalent in
35444 the operating system. Most, but not all versions of Unix that support Exim have
35445 this. For this particular stripchart, the top of the chart always represents
35446 100%, and the scale is given as &"x10%"&. This chart is configured by setting
35447 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
35448 &_Local/eximon.conf_& file.
35449
35450
35451
35452
35453 .section "Main action buttons" "SECID266"
35454 .cindex "size" "of monitor window"
35455 .cindex "Exim monitor" "window size"
35456 .cindex "window size"
35457 Below the stripcharts there is an action button for quitting the monitor. Next
35458 to this is another button marked &"Size"&. They are placed here so that
35459 shrinking the window to its default minimum size leaves just the queue count
35460 stripchart and these two buttons visible. Pressing the &"Size"& button causes
35461 the window to expand to its maximum size, unless it is already at the maximum,
35462 in which case it is reduced to its minimum.
35463
35464 When expanding to the maximum, if the window cannot be fully seen where it
35465 currently is, it is moved back to where it was the last time it was at full
35466 size. When it is expanding from its minimum size, the old position is
35467 remembered, and next time it is reduced to the minimum it is moved back there.
35468
35469 The idea is that you can keep a reduced window just showing one or two
35470 stripcharts at a convenient place on your screen, easily expand it to show
35471 the full window when required, and just as easily put it back to what it was.
35472 The idea is copied from what the &'twm'& window manager does for its
35473 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
35474 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
35475
35476 Normally, the monitor starts up with the window at its full size, but it can be
35477 built so that it starts up with the window at its smallest size, by setting
35478 START_SMALL=yes in &_Local/eximon.conf_&.
35479
35480
35481
35482 .section "The log display" "SECID267"
35483 .cindex "log" "tail of; in monitor"
35484 The second section of the window is an area in which a display of the tail of
35485 the main log is maintained.
35486 To save space on the screen, the timestamp on each log line is shortened by
35487 removing the date and, if &%log_timezone%& is set, the timezone.
35488 The log tail is not available when the only destination for logging data is
35489 syslog, unless the syslog lines are routed to a local file whose name is passed
35490 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
35491
35492 The log sub-window has a scroll bar at its lefthand side which can be used to
35493 move back to look at earlier text, and the up and down arrow keys also have a
35494 scrolling effect. The amount of log that is kept depends on the setting of
35495 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
35496 to use. When this is full, the earlier 50% of data is discarded &-- this is
35497 much more efficient than throwing it away line by line. The sub-window also has
35498 a horizontal scroll bar for accessing the ends of long log lines. This is the
35499 only means of horizontal scrolling; the right and left arrow keys are not
35500 available. Text can be cut from this part of the window using the mouse in the
35501 normal way. The size of this subwindow is controlled by parameters in the
35502 configuration file &_Local/eximon.conf_&.
35503
35504 Searches of the text in the log window can be carried out by means of the ^R
35505 and ^S keystrokes, which default to a reverse and a forward search,
35506 respectively. The search covers only the text that is displayed in the window.
35507 It cannot go further back up the log.
35508
35509 The point from which the search starts is indicated by a caret marker. This is
35510 normally at the end of the text in the window, but can be positioned explicitly
35511 by pointing and clicking with the left mouse button, and is moved automatically
35512 by a successful search. If new text arrives in the window when it is scrolled
35513 back, the caret remains where it is, but if the window is not scrolled back,
35514 the caret is moved to the end of the new text.
35515
35516 Pressing ^R or ^S pops up a window into which the search text can be typed.
35517 There are buttons for selecting forward or reverse searching, for carrying out
35518 the search, and for cancelling. If the &"Search"& button is pressed, the search
35519 happens and the window remains so that further searches can be done. If the
35520 &"Return"& key is pressed, a single search is done and the window is closed. If
35521 ^C is typed the search is cancelled.
35522
35523 The searching facility is implemented using the facilities of the Athena text
35524 widget. By default this pops up a window containing both &"search"& and
35525 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
35526 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
35527 However, the linkers in BSDI and HP-UX seem unable to handle an externally
35528 provided version of &%TextPop%& when the remaining parts of the text widget
35529 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
35530 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
35531 on these systems, at the expense of having unwanted items in the search popup
35532 window.
35533
35534
35535
35536 .section "The queue display" "SECID268"
35537 .cindex "queue" "display in monitor"
35538 The bottom section of the monitor window contains a list of all messages that
35539 are on the queue, which includes those currently being received or delivered,
35540 as well as those awaiting delivery. The size of this subwindow is controlled by
35541 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
35542 at which it is updated is controlled by another parameter in the same file &--
35543 the default is 5 minutes, since queue scans can be quite expensive. However,
35544 there is an &"Update"& action button just above the display which can be used
35545 to force an update of the queue display at any time.
35546
35547 When a host is down for some time, a lot of pending mail can build up for it,
35548 and this can make it hard to deal with other messages on the queue. To help
35549 with this situation there is a button next to &"Update"& called &"Hide"&. If
35550 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
35551 type anything in here and press &"Return"&, the text is added to a chain of
35552 such texts, and if every undelivered address in a message matches at least one
35553 of the texts, the message is not displayed.
35554
35555 If there is an address that does not match any of the texts, all the addresses
35556 are displayed as normal. The matching happens on the ends of addresses so, for
35557 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
35558 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
35559 has been set up, a button called &"Unhide"& is displayed. If pressed, it
35560 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
35561 a hide request is automatically cancelled after one hour.
35562
35563 While the dialogue box is displayed, you can't press any buttons or do anything
35564 else to the monitor window. For this reason, if you want to cut text from the
35565 queue display to use in the dialogue box, you have to do the cutting before
35566 pressing the &"Hide"& button.
35567
35568 The queue display contains, for each unhidden queued message, the length of
35569 time it has been on the queue, the size of the message, the message id, the
35570 message sender, and the first undelivered recipient, all on one line. If it is
35571 a bounce message, the sender is shown as &"<>"&. If there is more than one
35572 recipient to which the message has not yet been delivered, subsequent ones are
35573 listed on additional lines, up to a maximum configured number, following which
35574 an ellipsis is displayed. Recipients that have already received the message are
35575 not shown.
35576
35577 .cindex "frozen messages" "display"
35578 If a message is frozen, an asterisk is displayed at the left-hand side.
35579
35580 The queue display has a vertical scroll bar, and can also be scrolled by means
35581 of the arrow keys. Text can be cut from it using the mouse in the normal way.
35582 The text searching facilities, as described above for the log window, are also
35583 available, but the caret is always moved to the end of the text when the queue
35584 display is updated.
35585
35586
35587
35588 .section "The queue menu" "SECID269"
35589 .cindex "queue" "menu in monitor"
35590 If the &%shift%& key is held down and the left button is clicked when the mouse
35591 pointer is over the text for any message, an action menu pops up, and the first
35592 line of the queue display for the message is highlighted. This does not affect
35593 any selected text.
35594
35595 If you want to use some other event for popping up the menu, you can set the
35596 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
35597 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
35598 value set in this parameter is a standard X event description. For example, to
35599 run eximon using &%ctrl%& rather than &%shift%& you could use
35600 .code
35601 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
35602 .endd
35603 The title of the menu is the message id, and it contains entries which act as
35604 follows:
35605
35606 .ilist
35607 &'message log'&: The contents of the message log for the message are displayed
35608 in a new text window.
35609 .next
35610 &'headers'&: Information from the spool file that contains the envelope
35611 information and headers is displayed in a new text window. See chapter
35612 &<<CHAPspool>>& for a description of the format of spool files.
35613 .next
35614 &'body'&: The contents of the spool file containing the body of the message are
35615 displayed in a new text window. There is a default limit of 20,000 bytes to the
35616 amount of data displayed. This can be changed by setting the BODY_MAX
35617 option at compile time, or the EXIMON_BODY_MAX option at run time.
35618 .next
35619 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
35620 delivery of the message. This causes an automatic thaw if the message is
35621 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
35622 a new text window. The delivery is run in a separate process, to avoid holding
35623 up the monitor while the delivery proceeds.
35624 .next
35625 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
35626 that the message be frozen.
35627 .next
35628 .cindex "thawing messages"
35629 .cindex "unfreezing messages"
35630 .cindex "frozen messages" "thawing"
35631 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
35632 that the message be thawed.
35633 .next
35634 .cindex "delivery" "forcing failure"
35635 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
35636 that Exim gives up trying to deliver the message. A bounce message is generated
35637 for any remaining undelivered addresses.
35638 .next
35639 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
35640 that the message be deleted from the system without generating a bounce
35641 message.
35642 .next
35643 &'add recipient'&: A dialog box is displayed into which a recipient address can
35644 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
35645 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
35646 Otherwise it must be entered as a fully qualified address. Pressing RETURN
35647 causes a call to Exim to be made using the &%-Mar%& option to request that an
35648 additional recipient be added to the message, unless the entry box is empty, in
35649 which case no action is taken.
35650 .next
35651 &'mark delivered'&: A dialog box is displayed into which a recipient address
35652 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
35653 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
35654 Otherwise it must be entered as a fully qualified address. Pressing RETURN
35655 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
35656 recipient address as already delivered, unless the entry box is empty, in which
35657 case no action is taken.
35658 .next
35659 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
35660 mark all recipient addresses as already delivered.
35661 .next
35662 &'edit sender'&: A dialog box is displayed initialized with the current
35663 sender's address. Pressing RETURN causes a call to Exim to be made using the
35664 &%-Mes%& option to replace the sender address, unless the entry box is empty,
35665 in which case no action is taken. If you want to set an empty sender (as in
35666 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
35667 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
35668 the address is qualified with that domain.
35669 .endlist
35670
35671 When a delivery is forced, a window showing the &%-v%& output is displayed. In
35672 other cases when a call to Exim is made, if there is any output from Exim (in
35673 particular, if the command fails) a window containing the command and the
35674 output is displayed. Otherwise, the results of the action are normally apparent
35675 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
35676 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
35677 if no output is generated.
35678
35679 The queue display is automatically updated for actions such as freezing and
35680 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
35681 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
35682 force an update of the display after one of these actions.
35683
35684 In any text window that is displayed as result of a menu action, the normal
35685 cut-and-paste facility is available, and searching can be carried out using ^R
35686 and ^S, as described above for the log tail window.
35687 .ecindex IIDeximon
35688
35689
35690
35691
35692
35693 . ////////////////////////////////////////////////////////////////////////////
35694 . ////////////////////////////////////////////////////////////////////////////
35695
35696 .chapter "Security considerations" "CHAPsecurity"
35697 .scindex IIDsecurcon "security" "discussion of"
35698 This chapter discusses a number of issues concerned with security, some of
35699 which are also covered in other parts of this manual.
35700
35701 For reasons that this author does not understand, some people have promoted
35702 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
35703 existence of this chapter in the documentation. However, the intent of the
35704 chapter is simply to describe the way Exim works in relation to certain
35705 security concerns, not to make any specific claims about the effectiveness of
35706 its security as compared with other MTAs.
35707
35708 What follows is a description of the way Exim is supposed to be. Best efforts
35709 have been made to try to ensure that the code agrees with the theory, but an
35710 absence of bugs can never be guaranteed. Any that are reported will get fixed
35711 as soon as possible.
35712
35713
35714 .section "Building a more &""hardened""& Exim" "SECID286"
35715 .cindex "security" "build-time features"
35716 There are a number of build-time options that can be set in &_Local/Makefile_&
35717 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
35718 Exim administrator who does not have the root password, or by someone who has
35719 penetrated the Exim (but not the root) account. These options are as follows:
35720
35721 .ilist
35722 ALT_CONFIG_PREFIX can be set to a string that is required to match the
35723 start of any file names used with the &%-C%& option. When it is set, these file
35724 names are also not allowed to contain the sequence &"/../"&. (However, if the
35725 value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
35726 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
35727 default setting for &%ALT_CONFIG_PREFIX%&.
35728
35729 If the permitted configuration files are confined to a directory to
35730 which only root has access, this guards against someone who has broken
35731 into the Exim account from running a privileged Exim with an arbitrary
35732 configuration file, and using it to break into other accounts.
35733 .next
35734
35735 If a non-trusted configuration file (i.e. not the default configuration file
35736 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
35737 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
35738 the next item), then root privilege is retained only if the caller of Exim is
35739 root. This locks out the possibility of testing a configuration using &%-C%&
35740 right through message reception and delivery, even if the caller is root. The
35741 reception works, but by that time, Exim is running as the Exim user, so when
35742 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
35743 privilege to be lost. However, root can test reception and delivery using two
35744 separate commands.
35745
35746 .next
35747 The WHITELIST_D_MACROS build option declares some macros to be safe to override
35748 with &%-D%& if the real uid is one of root, the Exim run-time user or the
35749 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
35750 requiring the run-time value supplied to &%-D%& to match a regex that errs on
35751 the restrictive side. Requiring build-time selection of safe macros is onerous
35752 but this option is intended solely as a transition mechanism to permit
35753 previously-working configurations to continue to work after release 4.73.
35754 .next
35755 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
35756 is disabled.
35757 .next
35758 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
35759 never to be used for any deliveries. This is like the &%never_users%& runtime
35760 option, but it cannot be overridden; the runtime option adds additional users
35761 to the list. The default setting is &"root"&; this prevents a non-root user who
35762 is permitted to modify the runtime file from using Exim as a way to get root.
35763 .endlist
35764
35765
35766
35767 .section "Root privilege" "SECID270"
35768 .cindex "setuid"
35769 .cindex "root privilege"
35770 The Exim binary is normally setuid to root, which means that it gains root
35771 privilege (runs as root) when it starts execution. In some special cases (for
35772 example, when the daemon is not in use and there are no local deliveries), it
35773 may be possible to run Exim setuid to some user other than root. This is
35774 discussed in the next section. However, in most installations, root privilege
35775 is required for two things:
35776
35777 .ilist
35778 To set up a socket connected to the standard SMTP port (25) when initialising
35779 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
35780 not required.
35781 .next
35782 To be able to change uid and gid in order to read users' &_.forward_& files and
35783 perform local deliveries as the receiving user or as specified in the
35784 configuration.
35785 .endlist
35786
35787 It is not necessary to be root to do any of the other things Exim does, such as
35788 receiving messages and delivering them externally over SMTP, and it is
35789 obviously more secure if Exim does not run as root except when necessary.
35790 For this reason, a user and group for Exim to use must be defined in
35791 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
35792 group"&. Their values can be changed by the run time configuration, though this
35793 is not recommended. Often a user called &'exim'& is used, but some sites use
35794 &'mail'& or another user name altogether.
35795
35796 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
35797 abdication; the process cannot regain root afterwards. Prior to release 4.00,
35798 &[seteuid()]& was used in some circumstances, but this is no longer the case.
35799
35800 After a new Exim process has interpreted its command line options, it changes
35801 uid and gid in the following cases:
35802
35803 .ilist
35804 .oindex "&%-C%&"
35805 .oindex "&%-D%&"
35806 If the &%-C%& option is used to specify an alternate configuration file, or if
35807 the &%-D%& option is used to define macro values for the configuration, and the
35808 calling process is not running as root, the uid and gid are changed to those of
35809 the calling process.
35810 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
35811 option may not be used at all.
35812 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
35813 can be supplied if the calling process is running as root, the Exim run-time
35814 user or CONFIGURE_OWNER, if defined.
35815 .next
35816 .oindex "&%-be%&"
35817 .oindex "&%-bf%&"
35818 .oindex "&%-bF%&"
35819 If the expansion test option (&%-be%&) or one of the filter testing options
35820 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
35821 calling process.
35822 .next
35823 If the process is not a daemon process or a queue runner process or a delivery
35824 process or a process for testing address routing (started with &%-bt%&), the
35825 uid and gid are changed to the Exim user and group. This means that Exim always
35826 runs under its own uid and gid when receiving messages. This also applies when
35827 testing address verification
35828 .oindex "&%-bv%&"
35829 .oindex "&%-bh%&"
35830 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
35831 option).
35832 .next
35833 For a daemon, queue runner, delivery, or address testing process, the uid
35834 remains as root at this stage, but the gid is changed to the Exim group.
35835 .endlist
35836
35837 The processes that initially retain root privilege behave as follows:
35838
35839 .ilist
35840 A daemon process changes the gid to the Exim group and the uid to the Exim
35841 user after setting up one or more listening sockets. The &[initgroups()]&
35842 function is called, so that if the Exim user is in any additional groups, they
35843 will be used during message reception.
35844 .next
35845 A queue runner process retains root privilege throughout its execution. Its
35846 job is to fork a controlled sequence of delivery processes.
35847 .next
35848 A delivery process retains root privilege throughout most of its execution,
35849 but any actual deliveries (that is, the transports themselves) are run in
35850 subprocesses which always change to a non-root uid and gid. For local
35851 deliveries this is typically the uid and gid of the owner of the mailbox; for
35852 remote deliveries, the Exim uid and gid are used. Once all the delivery
35853 subprocesses have been run, a delivery process changes to the Exim uid and gid
35854 while doing post-delivery tidying up such as updating the retry database and
35855 generating bounce and warning messages.
35856
35857 While the recipient addresses in a message are being routed, the delivery
35858 process runs as root. However, if a user's filter file has to be processed,
35859 this is done in a subprocess that runs under the individual user's uid and
35860 gid. A system filter is run as root unless &%system_filter_user%& is set.
35861 .next
35862 A process that is testing addresses (the &%-bt%& option) runs as root so that
35863 the routing is done in the same environment as a message delivery.
35864 .endlist
35865
35866
35867
35868
35869 .section "Running Exim without privilege" "SECTrunexiwitpri"
35870 .cindex "privilege, running without"
35871 .cindex "unprivileged running"
35872 .cindex "root privilege" "running without"
35873 Some installations like to run Exim in an unprivileged state for more of its
35874 operation, for added security. Support for this mode of operation is provided
35875 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
35876 gid are changed to the Exim user and group at the start of a delivery process
35877 (and also queue runner and address testing processes). This means that address
35878 routing is no longer run as root, and the deliveries themselves cannot change
35879 to any other uid.
35880
35881 .cindex SIGHUP
35882 .cindex "daemon" "restarting"
35883 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
35884 that the daemon can still be started in the usual way, and it can respond
35885 correctly to SIGHUP because the re-invocation regains root privilege.
35886
35887 An alternative approach is to make Exim setuid to the Exim user and also setgid
35888 to the Exim group. If you do this, the daemon must be started from a root
35889 process. (Calling Exim from a root process makes it behave in the way it does
35890 when it is setuid root.) However, the daemon cannot restart itself after a
35891 SIGHUP signal because it cannot regain privilege.
35892
35893 It is still useful to set &%deliver_drop_privilege%& in this case, because it
35894 stops Exim from trying to re-invoke itself to do a delivery after a message has
35895 been received. Such a re-invocation is a waste of resources because it has no
35896 effect.
35897
35898 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
35899 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
35900 to the Exim user seems a clean approach, but there is one complication:
35901
35902 In this style of operation, Exim is running with the real uid and gid set to
35903 those of the calling process, and the effective uid/gid set to Exim's values.
35904 Ideally, any association with the calling process' uid/gid should be dropped,
35905 that is, the real uid/gid should be reset to the effective values so as to
35906 discard any privileges that the caller may have. While some operating systems
35907 have a function that permits this action for a non-root effective uid, quite a
35908 number of them do not. Because of this lack of standardization, Exim does not
35909 address this problem at this time.
35910
35911 For this reason, the recommended approach for &"mostly unprivileged"& running
35912 is to keep the Exim binary setuid to root, and to set
35913 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
35914 be used in the most straightforward way.
35915
35916 If you configure Exim not to run delivery processes as root, there are a
35917 number of restrictions on what you can do:
35918
35919 .ilist
35920 You can deliver only as the Exim user/group. You should explicitly use the
35921 &%user%& and &%group%& options to override routers or local transports that
35922 normally deliver as the recipient. This makes sure that configurations that
35923 work in this mode function the same way in normal mode. Any implicit or
35924 explicit specification of another user causes an error.
35925 .next
35926 Use of &_.forward_& files is severely restricted, such that it is usually
35927 not worthwhile to include them in the configuration.
35928 .next
35929 Users who wish to use &_.forward_& would have to make their home directory and
35930 the file itself accessible to the Exim user. Pipe and append-to-file entries,
35931 and their equivalents in Exim filters, cannot be used. While they could be
35932 enabled in the Exim user's name, that would be insecure and not very useful.
35933 .next
35934 Unless the local user mailboxes are all owned by the Exim user (possible in
35935 some POP3 or IMAP-only environments):
35936
35937 .olist
35938 They must be owned by the Exim group and be writeable by that group. This
35939 implies you must set &%mode%& in the appendfile configuration, as well as the
35940 mode of the mailbox files themselves.
35941 .next
35942 You must set &%no_check_owner%&, since most or all of the files will not be
35943 owned by the Exim user.
35944 .next
35945 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
35946 on a newly created mailbox when unprivileged. This also implies that new
35947 mailboxes need to be created manually.
35948 .endlist olist
35949 .endlist ilist
35950
35951
35952 These restrictions severely restrict what can be done in local deliveries.
35953 However, there are no restrictions on remote deliveries. If you are running a
35954 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
35955 gives more security at essentially no cost.
35956
35957 If you are using the &%mua_wrapper%& facility (see chapter
35958 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
35959
35960
35961
35962
35963 .section "Delivering to local files" "SECID271"
35964 Full details of the checks applied by &(appendfile)& before it writes to a file
35965 are given in chapter &<<CHAPappendfile>>&.
35966
35967
35968
35969 .section "Running local commands" "SECTsecconslocalcmds"
35970 .cindex "security" "local commands"
35971 .cindex "security" "command injection attacks"
35972 There are a number of ways in which an administrator can configure Exim to run
35973 commands based upon received, untrustworthy, data. Further, in some
35974 configurations a user who can control a &_.forward_& file can also arrange to
35975 run commands. Configuration to check includes, but is not limited to:
35976
35977 .ilist
35978 Use of &%use_shell%& in the pipe transport: various forms of shell command
35979 injection may be possible with this option present. It is dangerous and should
35980 be used only with considerable caution. Consider constraints which whitelist
35981 allowed characters in a variable which is to be used in a pipe transport that
35982 has &%use_shell%& enabled.
35983 .next
35984 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
35985 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
35986 &_.forward_& files in a redirect router. If Exim is running on a central mail
35987 hub to which ordinary users do not have shell access, but home directories are
35988 NFS mounted (for instance) then administrators should review the list of these
35989 forbid options available, and should bear in mind that the options that may
35990 need forbidding can change as new features are added between releases.
35991 .next
35992 The &%${run...}%& expansion item does not use a shell by default, but
35993 administrators can configure use of &_/bin/sh_& as part of the command.
35994 Such invocations should be viewed with prejudicial suspicion.
35995 .next
35996 Administrators who use embedded Perl are advised to explore how Perl's
35997 taint checking might apply to their usage.
35998 .next
35999 Use of &%${expand...}%& is somewhat analagous to shell's eval builtin and
36000 administrators are well advised to view its use with suspicion, in case (for
36001 instance) it allows a local-part to contain embedded Exim directives.
36002 .next
36003 Use of &%${match_local_part...}%& and friends becomes more dangerous if
36004 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
36005 each can reference arbitrary lists and files, rather than just being a list
36006 of opaque strings.
36007 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
36008 real-world security vulnerabilities caused by its use with untrustworthy data
36009 injected in, for SQL injection attacks.
36010 Consider the use of the &%inlisti%& expansion condition instead.
36011 .endlist
36012
36013
36014
36015
36016 .section "Trust in configuration data" "SECTsecconfdata"
36017 .cindex "security" "data sources"
36018 .cindex "security" "regular expressions"
36019 .cindex "regular expressions" "security"
36020 .cindex "PCRE" "security"
36021 If configuration data for Exim can come from untrustworthy sources, there
36022 are some issues to be aware of:
36023
36024 .ilist
36025 Use of &%${expand...}%& may provide a path for shell injection attacks.
36026 .next
36027 Letting untrusted data provide a regular expression is unwise.
36028 .next
36029 Using &%${match...}%& to apply a fixed regular expression against untrusted
36030 data may result in pathological behaviour within PCRE. Be aware of what
36031 "backtracking" means and consider options for being more strict with a regular
36032 expression. Avenues to explore include limiting what can match (avoiding &`.`&
36033 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
36034 possessive quantifiers or just not using regular expressions against untrusted
36035 data.
36036 .next
36037 It can be important to correctly use &%${quote:...}%&,
36038 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
36039 items to ensure that data is correctly constructed.
36040 .next
36041 Some lookups might return multiple results, even though normal usage is only
36042 expected to yield one result.
36043 .endlist
36044
36045
36046
36047
36048 .section "IPv4 source routing" "SECID272"
36049 .cindex "source routing" "in IP packets"
36050 .cindex "IP source routing"
36051 Many operating systems suppress IP source-routed packets in the kernel, but
36052 some cannot be made to do this, so Exim does its own check. It logs incoming
36053 IPv4 source-routed TCP calls, and then drops them. Things are all different in
36054 IPv6. No special checking is currently done.
36055
36056
36057
36058 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
36059 Support for these SMTP commands is disabled by default. If required, they can
36060 be enabled by defining suitable ACLs.
36061
36062
36063
36064
36065 .section "Privileged users" "SECID274"
36066 .cindex "trusted users"
36067 .cindex "admin user"
36068 .cindex "privileged user"
36069 .cindex "user" "trusted"
36070 .cindex "user" "admin"
36071 Exim recognizes two sets of users with special privileges. Trusted users are
36072 able to submit new messages to Exim locally, but supply their own sender
36073 addresses and information about a sending host. For other users submitting
36074 local messages, Exim sets up the sender address from the uid, and doesn't
36075 permit a remote host to be specified.
36076
36077 .oindex "&%-f%&"
36078 However, an untrusted user is permitted to use the &%-f%& command line option
36079 in the special form &%-f <>%& to indicate that a delivery failure for the
36080 message should not cause an error report. This affects the message's envelope,
36081 but it does not affect the &'Sender:'& header. Untrusted users may also be
36082 permitted to use specific forms of address with the &%-f%& option by setting
36083 the &%untrusted_set_sender%& option.
36084
36085 Trusted users are used to run processes that receive mail messages from some
36086 other mail domain and pass them on to Exim for delivery either locally, or over
36087 the Internet. Exim trusts a caller that is running as root, as the Exim user,
36088 as any user listed in the &%trusted_users%& configuration option, or under any
36089 group listed in the &%trusted_groups%& option.
36090
36091 Admin users are permitted to do things to the messages on Exim's queue. They
36092 can freeze or thaw messages, cause them to be returned to their senders, remove
36093 them entirely, or modify them in various ways. In addition, admin users can run
36094 the Exim monitor and see all the information it is capable of providing, which
36095 includes the contents of files on the spool.
36096
36097 .oindex "&%-M%&"
36098 .oindex "&%-q%&"
36099 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
36100 delivery of messages on its queue is restricted to admin users. This
36101 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
36102 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
36103 queue is also restricted to admin users. This restriction can be relaxed by
36104 setting &%no_queue_list_requires_admin%&.
36105
36106 Exim recognizes an admin user if the calling process is running as root or as
36107 the Exim user or if any of the groups associated with the calling process is
36108 the Exim group. It is not necessary actually to be running under the Exim
36109 group. However, if admin users who are not root or the Exim user are to access
36110 the contents of files on the spool via the Exim monitor (which runs
36111 unprivileged), Exim must be built to allow group read access to its spool
36112 files.
36113
36114
36115
36116 .section "Spool files" "SECID275"
36117 .cindex "spool directory" "files"
36118 Exim's spool directory and everything it contains is owned by the Exim user and
36119 set to the Exim group. The mode for spool files is defined in the
36120 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
36121 any user who is a member of the Exim group can access these files.
36122
36123
36124
36125 .section "Use of argv[0]" "SECID276"
36126 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
36127 of specific strings, Exim assumes certain options. For example, calling Exim
36128 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
36129 to calling it with the option &%-bS%&. There are no security implications in
36130 this.
36131
36132
36133
36134 .section "Use of %f formatting" "SECID277"
36135 The only use made of &"%f"& by Exim is in formatting load average values. These
36136 are actually stored in integer variables as 1000 times the load average.
36137 Consequently, their range is limited and so therefore is the length of the
36138 converted output.
36139
36140
36141
36142 .section "Embedded Exim path" "SECID278"
36143 Exim uses its own path name, which is embedded in the code, only when it needs
36144 to re-exec in order to regain root privilege. Therefore, it is not root when it
36145 does so. If some bug allowed the path to get overwritten, it would lead to an
36146 arbitrary program's being run as exim, not as root.
36147
36148
36149
36150 .section "Dynamic module directory" "SECTdynmoddir"
36151 Any dynamically loadable modules must be installed into the directory
36152 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
36153 loading it.
36154
36155
36156 .section "Use of sprintf()" "SECID279"
36157 .cindex "&[sprintf()]&"
36158 A large number of occurrences of &"sprintf"& in the code are actually calls to
36159 &'string_sprintf()'&, a function that returns the result in malloc'd store.
36160 The intermediate formatting is done into a large fixed buffer by a function
36161 that runs through the format string itself, and checks the length of each
36162 conversion before performing it, thus preventing buffer overruns.
36163
36164 The remaining uses of &[sprintf()]& happen in controlled circumstances where
36165 the output buffer is known to be sufficiently long to contain the converted
36166 string.
36167
36168
36169
36170 .section "Use of debug_printf() and log_write()" "SECID280"
36171 Arbitrary strings are passed to both these functions, but they do their
36172 formatting by calling the function &'string_vformat()'&, which runs through
36173 the format string itself, and checks the length of each conversion.
36174
36175
36176
36177 .section "Use of strcat() and strcpy()" "SECID281"
36178 These are used only in cases where the output buffer is known to be large
36179 enough to hold the result.
36180 .ecindex IIDsecurcon
36181
36182
36183
36184
36185 . ////////////////////////////////////////////////////////////////////////////
36186 . ////////////////////////////////////////////////////////////////////////////
36187
36188 .chapter "Format of spool files" "CHAPspool"
36189 .scindex IIDforspo1 "format" "spool files"
36190 .scindex IIDforspo2 "spool directory" "format of files"
36191 .scindex IIDforspo3 "spool files" "format of"
36192 .cindex "spool files" "editing"
36193 A message on Exim's queue consists of two files, whose names are the message id
36194 followed by -D and -H, respectively. The data portion of the message is kept in
36195 the -D file on its own. The message's envelope, status, and headers are all
36196 kept in the -H file, whose format is described in this chapter. Each of these
36197 two files contains the final component of its own name as its first line. This
36198 is insurance against disk crashes where the directory is lost but the files
36199 themselves are recoverable.
36200
36201 Some people are tempted into editing -D files in order to modify messages. You
36202 need to be extremely careful if you do this; it is not recommended and you are
36203 on your own if you do it. Here are some of the pitfalls:
36204
36205 .ilist
36206 You must ensure that Exim does not try to deliver the message while you are
36207 fiddling with it. The safest way is to take out a write lock on the -D file,
36208 which is what Exim itself does, using &[fcntl()]&. If you update the file in
36209 place, the lock will be retained. If you write a new file and rename it, the
36210 lock will be lost at the instant of rename.
36211 .next
36212 .vindex "&$body_linecount$&"
36213 If you change the number of lines in the file, the value of
36214 &$body_linecount$&, which is stored in the -H file, will be incorrect. At
36215 present, this value is not used by Exim, but there is no guarantee that this
36216 will always be the case.
36217 .next
36218 If the message is in MIME format, you must take care not to break it.
36219 .next
36220 If the message is cryptographically signed, any change will invalidate the
36221 signature.
36222 .endlist
36223 All in all, modifying -D files is fraught with danger.
36224
36225 Files whose names end with -J may also be seen in the &_input_& directory (or
36226 its subdirectories when &%split_spool_directory%& is set). These are journal
36227 files, used to record addresses to which the message has been delivered during
36228 the course of a delivery attempt. If there are still undelivered recipients at
36229 the end, the -H file is updated, and the -J file is deleted. If, however, there
36230 is some kind of crash (for example, a power outage) before this happens, the -J
36231 file remains in existence. When Exim next processes the message, it notices the
36232 -J file and uses it to update the -H file before starting the next delivery
36233 attempt.
36234
36235 .section "Format of the -H file" "SECID282"
36236 .cindex "uid (user id)" "in spool file"
36237 .cindex "gid (group id)" "in spool file"
36238 The second line of the -H file contains the login name for the uid of the
36239 process that called Exim to read the message, followed by the numerical uid and
36240 gid. For a locally generated message, this is normally the user who sent the
36241 message. For a message received over TCP/IP via the daemon, it is
36242 normally the Exim user.
36243
36244 The third line of the file contains the address of the message's sender as
36245 transmitted in the envelope, contained in angle brackets. The sender address is
36246 empty for bounce messages. For incoming SMTP mail, the sender address is given
36247 in the MAIL command. For locally generated mail, the sender address is
36248 created by Exim from the login name of the current user and the configured
36249 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
36250 leading &"From&~"& line if the caller is trusted, or if the supplied address is
36251 &"<>"& or an address that matches &%untrusted_set_senders%&.
36252
36253 The fourth line contains two numbers. The first is the time that the message
36254 was received, in the conventional Unix form &-- the number of seconds since the
36255 start of the epoch. The second number is a count of the number of messages
36256 warning of delayed delivery that have been sent to the sender.
36257
36258 There follow a number of lines starting with a hyphen. These can appear in any
36259 order, and are omitted when not relevant:
36260
36261 .vlist
36262 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
36263 This item is obsolete, and is not generated from Exim release 4.61 onwards;
36264 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
36265 recognized, to provide backward compatibility. In the old format, a line of
36266 this form is present for every ACL variable that is not empty. The number
36267 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
36268 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
36269 the data string for the variable. The string itself starts at the beginning of
36270 the next line, and is followed by a newline character. It may contain internal
36271 newlines.
36272
36273 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
36274 A line of this form is present for every ACL connection variable that is
36275 defined. Note that there is a space between &%-aclc%& and the rest of the name.
36276 The length is the length of the data string for the variable. The string itself
36277 starts at the beginning of the next line, and is followed by a newline
36278 character. It may contain internal newlines.
36279
36280 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
36281 A line of this form is present for every ACL message variable that is defined.
36282 Note that there is a space between &%-aclm%& and the rest of the name. The
36283 length is the length of the data string for the variable. The string itself
36284 starts at the beginning of the next line, and is followed by a newline
36285 character. It may contain internal newlines.
36286
36287 .vitem "&%-active_hostname%&&~<&'hostname'&>"
36288 This is present if, when the message was received over SMTP, the value of
36289 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
36290
36291 .vitem &%-allow_unqualified_recipient%&
36292 This is present if unqualified recipient addresses are permitted in header
36293 lines (to stop such addresses from being qualified if rewriting occurs at
36294 transport time). Local messages that were input using &%-bnq%& and remote
36295 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
36296
36297 .vitem &%-allow_unqualified_sender%&
36298 This is present if unqualified sender addresses are permitted in header lines
36299 (to stop such addresses from being qualified if rewriting occurs at transport
36300 time). Local messages that were input using &%-bnq%& and remote messages from
36301 hosts that match &%sender_unqualified_hosts%& set this flag.
36302
36303 .vitem "&%-auth_id%&&~<&'text'&>"
36304 The id information for a message received on an authenticated SMTP connection
36305 &-- the value of the &$authenticated_id$& variable.
36306
36307 .vitem "&%-auth_sender%&&~<&'address'&>"
36308 The address of an authenticated sender &-- the value of the
36309 &$authenticated_sender$& variable.
36310
36311 .vitem "&%-body_linecount%&&~<&'number'&>"
36312 This records the number of lines in the body of the message, and is always
36313 present.
36314
36315 .vitem "&%-body_zerocount%&&~<&'number'&>"
36316 This records the number of binary zero bytes in the body of the message, and is
36317 present if the number is greater than zero.
36318
36319 .vitem &%-deliver_firsttime%&
36320 This is written when a new message is first added to the spool. When the spool
36321 file is updated after a deferral, it is omitted.
36322
36323 .vitem "&%-frozen%&&~<&'time'&>"
36324 .cindex "frozen messages" "spool data"
36325 The message is frozen, and the freezing happened at <&'time'&>.
36326
36327 .vitem "&%-helo_name%&&~<&'text'&>"
36328 This records the host name as specified by a remote host in a HELO or EHLO
36329 command.
36330
36331 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
36332 This records the IP address of the host from which the message was received and
36333 the remote port number that was used. It is omitted for locally generated
36334 messages.
36335
36336 .vitem "&%-host_auth%&&~<&'text'&>"
36337 If the message was received on an authenticated SMTP connection, this records
36338 the name of the authenticator &-- the value of the
36339 &$sender_host_authenticated$& variable.
36340
36341 .vitem &%-host_lookup_failed%&
36342 This is present if an attempt to look up the sending host's name from its IP
36343 address failed. It corresponds to the &$host_lookup_failed$& variable.
36344
36345 .vitem "&%-host_name%&&~<&'text'&>"
36346 .cindex "reverse DNS lookup"
36347 .cindex "DNS" "reverse lookup"
36348 This records the name of the remote host from which the message was received,
36349 if the host name was looked up from the IP address when the message was being
36350 received. It is not present if no reverse lookup was done.
36351
36352 .vitem "&%-ident%&&~<&'text'&>"
36353 For locally submitted messages, this records the login of the originating user,
36354 unless it was a trusted user and the &%-oMt%& option was used to specify an
36355 ident value. For messages received over TCP/IP, this records the ident string
36356 supplied by the remote host, if any.
36357
36358 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
36359 This records the IP address of the local interface and the port number through
36360 which a message was received from a remote host. It is omitted for locally
36361 generated messages.
36362
36363 .vitem &%-local%&
36364 The message is from a local sender.
36365
36366 .vitem &%-localerror%&
36367 The message is a locally-generated bounce message.
36368
36369 .vitem "&%-local_scan%&&~<&'string'&>"
36370 This records the data string that was returned by the &[local_scan()]& function
36371 when the message was received &-- the value of the &$local_scan_data$&
36372 variable. It is omitted if no data was returned.
36373
36374 .vitem &%-manual_thaw%&
36375 The message was frozen but has been thawed manually, that is, by an explicit
36376 Exim command rather than via the auto-thaw process.
36377
36378 .vitem &%-N%&
36379 A testing delivery process was started using the &%-N%& option to suppress any
36380 actual deliveries, but delivery was deferred. At any further delivery attempts,
36381 &%-N%& is assumed.
36382
36383 .vitem &%-received_protocol%&
36384 This records the value of the &$received_protocol$& variable, which contains
36385 the name of the protocol by which the message was received.
36386
36387 .vitem &%-sender_set_untrusted%&
36388 The envelope sender of this message was set by an untrusted local caller (used
36389 to ensure that the caller is displayed in queue listings).
36390
36391 .vitem "&%-spam_score_int%&&~<&'number'&>"
36392 If a message was scanned by SpamAssassin, this is present. It records the value
36393 of &$spam_score_int$&.
36394
36395 .vitem &%-tls_certificate_verified%&
36396 A TLS certificate was received from the client that sent this message, and the
36397 certificate was verified by the server.
36398
36399 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
36400 When the message was received over an encrypted connection, this records the
36401 name of the cipher suite that was used.
36402
36403 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
36404 When the message was received over an encrypted connection, and a certificate
36405 was received from the client, this records the Distinguished Name from that
36406 certificate.
36407 .endlist
36408
36409 Following the options there is a list of those addresses to which the message
36410 is not to be delivered. This set of addresses is initialized from the command
36411 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
36412 is set; otherwise it starts out empty. Whenever a successful delivery is made,
36413 the address is added to this set. The addresses are kept internally as a
36414 balanced binary tree, and it is a representation of that tree which is written
36415 to the spool file. If an address is expanded via an alias or forward file, the
36416 original address is added to the tree when deliveries to all its child
36417 addresses are complete.
36418
36419 If the tree is empty, there is a single line in the spool file containing just
36420 the text &"XX"&. Otherwise, each line consists of two letters, which are either
36421 Y or N, followed by an address. The address is the value for the node of the
36422 tree, and the letters indicate whether the node has a left branch and/or a
36423 right branch attached to it, respectively. If branches exist, they immediately
36424 follow. Here is an example of a three-node tree:
36425 .code
36426 YY darcy@austen.fict.example
36427 NN alice@wonderland.fict.example
36428 NN editor@thesaurus.ref.example
36429 .endd
36430 After the non-recipients tree, there is a list of the message's recipients.
36431 This is a simple list, preceded by a count. It includes all the original
36432 recipients of the message, including those to whom the message has already been
36433 delivered. In the simplest case, the list contains one address per line. For
36434 example:
36435 .code
36436 4
36437 editor@thesaurus.ref.example
36438 darcy@austen.fict.example
36439 rdo@foundation
36440 alice@wonderland.fict.example
36441 .endd
36442 However, when a child address has been added to the top-level addresses as a
36443 result of the use of the &%one_time%& option on a &(redirect)& router, each
36444 line is of the following form:
36445 .display
36446 <&'top-level address'&> <&'errors_to address'&> &&&
36447 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
36448 .endd
36449 The 01 flag bit indicates the presence of the three other fields that follow
36450 the top-level address. Other bits may be used in future to support additional
36451 fields. The <&'parent number'&> is the offset in the recipients list of the
36452 original parent of the &"one time"& address. The first two fields are the
36453 envelope sender that is associated with this address and its length. If the
36454 length is zero, there is no special envelope sender (there are then two space
36455 characters in the line). A non-empty field can arise from a &(redirect)& router
36456 that has an &%errors_to%& setting.
36457
36458
36459 A blank line separates the envelope and status information from the headers
36460 which follow. A header may occupy several lines of the file, and to save effort
36461 when reading it in, each header is preceded by a number and an identifying
36462 character. The number is the number of characters in the header, including any
36463 embedded newlines and the terminating newline. The character is one of the
36464 following:
36465
36466 .table2 50pt
36467 .row <&'blank'&> "header in which Exim has no special interest"
36468 .row &`B`& "&'Bcc:'& header"
36469 .row &`C`& "&'Cc:'& header"
36470 .row &`F`& "&'From:'& header"
36471 .row &`I`& "&'Message-id:'& header"
36472 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
36473 .row &`R`& "&'Reply-To:'& header"
36474 .row &`S`& "&'Sender:'& header"
36475 .row &`T`& "&'To:'& header"
36476 .row &`*`& "replaced or deleted header"
36477 .endtable
36478
36479 Deleted or replaced (rewritten) headers remain in the spool file for debugging
36480 purposes. They are not transmitted when the message is delivered. Here is a
36481 typical set of headers:
36482 .code
36483 111P Received: by hobbit.fict.example with local (Exim 4.00)
36484 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
36485 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
36486 038* X-rewrote-sender: bb@hobbit.fict.example
36487 042* From: Bilbo Baggins <bb@hobbit.fict.example>
36488 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
36489 099* To: alice@wonderland.fict.example, rdo@foundation,
36490 darcy@austen.fict.example, editor@thesaurus.ref.example
36491 104T To: alice@wonderland.fict.example, rdo@foundation.example,
36492 darcy@austen.fict.example, editor@thesaurus.ref.example
36493 038 Date: Fri, 11 May 2001 10:28:59 +0100
36494 .endd
36495 The asterisked headers indicate that the envelope sender, &'From:'& header, and
36496 &'To:'& header have been rewritten, the last one because routing expanded the
36497 unqualified domain &'foundation'&.
36498 .ecindex IIDforspo1
36499 .ecindex IIDforspo2
36500 .ecindex IIDforspo3
36501
36502 . ////////////////////////////////////////////////////////////////////////////
36503 . ////////////////////////////////////////////////////////////////////////////
36504
36505 .chapter "Support for DKIM (DomainKeys Identified Mail)" "CHAPdkim" &&&
36506 "DKIM Support"
36507 .cindex "DKIM"
36508
36509 DKIM is a mechanism by which messages sent by some entity can be provably
36510 linked to a domain which that entity controls. It permits reputation to
36511 be tracked on a per-domain basis, rather than merely upon source IP address.
36512 DKIM is documented in RFC 4871.
36513
36514 Since version 4.70, DKIM support is compiled into Exim by default. It can be
36515 disabled by setting DISABLE_DKIM=yes in Local/Makefile.
36516
36517 Exim's DKIM implementation allows to
36518 .olist
36519 Sign outgoing messages: This function is implemented in the SMTP transport.
36520 It can co-exist with all other Exim features
36521 (including transport filters)
36522 except cutthrough delivery.
36523 .next
36524 Verify signatures in incoming messages: This is implemented by an additional
36525 ACL (acl_smtp_dkim), which can be called several times per message, with
36526 different signature contexts.
36527 .endlist
36528
36529 In typical Exim style, the verification implementation does not include any
36530 default "policy". Instead it enables you to build your own policy using
36531 Exim's standard controls.
36532
36533 Please note that verification of DKIM signatures in incoming mail is turned
36534 on by default for logging purposes. For each signature in incoming email,
36535 exim will log a line displaying the most important signature details, and the
36536 signature status. Here is an example (with line-breaks added for clarity):
36537 .code
36538 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
36539 d=facebookmail.com s=q1-2009b
36540 c=relaxed/relaxed a=rsa-sha1
36541 i=@facebookmail.com t=1252484542 [verification succeeded]
36542 .endd
36543 You might want to turn off DKIM verification processing entirely for internal
36544 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
36545 control modifier. This should typically be done in the RCPT ACL, at points
36546 where you accept mail from relay sources (internal hosts or authenticated
36547 senders).
36548
36549
36550 .section "Signing outgoing messages" "SECID513"
36551 .cindex "DKIM" "signing"
36552
36553 Signing is implemented by setting private options on the SMTP transport.
36554 These options take (expandable) strings as arguments.
36555
36556 .option dkim_domain smtp string&!! unset
36557 MANDATORY:
36558 The domain you want to sign with. The result of this expanded
36559 option is put into the &%$dkim_domain%& expansion variable.
36560
36561 .option dkim_selector smtp string&!! unset
36562 MANDATORY:
36563 This sets the key selector string. You can use the &%$dkim_domain%& expansion
36564 variable to look up a matching selector. The result is put in the expansion
36565 variable &%$dkim_selector%& which should be used in the &%dkim_private_key%&
36566 option along with &%$dkim_domain%&.
36567
36568 .option dkim_private_key smtp string&!! unset
36569 MANDATORY:
36570 This sets the private key to use. You can use the &%$dkim_domain%& and
36571 &%$dkim_selector%& expansion variables to determine the private key to use.
36572 The result can either
36573 .ilist
36574 be a valid RSA private key in ASCII armor, including line breaks.
36575 .next
36576 start with a slash, in which case it is treated as a file that contains
36577 the private key.
36578 .next
36579 be "0", "false" or the empty string, in which case the message will not
36580 be signed. This case will not result in an error, even if &%dkim_strict%&
36581 is set.
36582 .endlist
36583
36584 .option dkim_canon smtp string&!! unset
36585 OPTIONAL:
36586 This option sets the canonicalization method used when signing a message.
36587 The DKIM RFC currently supports two methods: "simple" and "relaxed".
36588 The option defaults to "relaxed" when unset. Note: the current implementation
36589 only supports using the same canonicalization method for both headers and body.
36590
36591 .option dkim_strict smtp string&!! unset
36592 OPTIONAL:
36593 This option defines how Exim behaves when signing a message that
36594 should be signed fails for some reason. When the expansion evaluates to
36595 either "1" or "true", Exim will defer. Otherwise Exim will send the message
36596 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
36597 variables here.
36598
36599 .option dkim_sign_headers smtp string&!! unset
36600 OPTIONAL:
36601 When set, this option must expand to (or be specified as) a colon-separated
36602 list of header names. Headers with these names will be included in the message
36603 signature. When unspecified, the header names recommended in RFC4871 will be
36604 used.
36605
36606
36607 .section "Verifying DKIM signatures in incoming mail" "SECID514"
36608 .cindex "DKIM" "verification"
36609
36610 Verification of DKIM signatures in incoming email is implemented via the
36611 &%acl_smtp_dkim%& ACL. By default, this ACL is called once for each
36612 syntactically(!) correct signature in the incoming message.
36613 A missing ACL definition defaults to accept.
36614 If any ACL call does not acccept, the message is not accepted.
36615 If a cutthrough delivery was in progress for the message it is
36616 summarily dropped (having wasted the transmission effort).
36617
36618 To evaluate the signature in the ACL a large number of expansion variables
36619 containing the signature status and its details are set up during the
36620 runtime of the ACL.
36621
36622 Calling the ACL only for existing signatures is not sufficient to build
36623 more advanced policies. For that reason, the global option
36624 &%dkim_verify_signers%&, and a global expansion variable
36625 &%$dkim_signers%& exist.
36626
36627 The global option &%dkim_verify_signers%& can be set to a colon-separated
36628 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
36629 called. It is expanded when the message has been received. At this point,
36630 the expansion variable &%$dkim_signers%& already contains a colon-separated
36631 list of signer domains and identities for the message. When
36632 &%dkim_verify_signers%& is not specified in the main configuration,
36633 it defaults as:
36634 .code
36635 dkim_verify_signers = $dkim_signers
36636 .endd
36637 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
36638 DKIM signature in the message. Current DKIM verifiers may want to explicitly
36639 call the ACL for known domains or identities. This would be achieved as follows:
36640 .code
36641 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
36642 .endd
36643 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
36644 and "ebay.com", plus all domains and identities that have signatures in the message.
36645 You can also be more creative in constructing your policy. For example:
36646 .code
36647 dkim_verify_signers = $sender_address_domain:$dkim_signers
36648 .endd
36649
36650 If a domain or identity is listed several times in the (expanded) value of
36651 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
36652
36653
36654 Inside the &%acl_smtp_dkim%&, the following expansion variables are
36655 available (from most to least important):
36656
36657
36658 .vlist
36659 .vitem &%$dkim_cur_signer%&
36660 The signer that is being evaluated in this ACL run. This can be a domain or
36661 an identity. This is one of the list items from the expanded main option
36662 &%dkim_verify_signers%& (see above).
36663 .vitem &%$dkim_verify_status%&
36664 A string describing the general status of the signature. One of
36665 .ilist
36666 &%none%&: There is no signature in the message for the current domain or
36667 identity (as reflected by &%$dkim_cur_signer%&).
36668 .next
36669 &%invalid%&: The signature could not be verified due to a processing error.
36670 More detail is available in &%$dkim_verify_reason%&.
36671 .next
36672 &%fail%&: Verification of the signature failed. More detail is
36673 available in &%$dkim_verify_reason%&.
36674 .next
36675 &%pass%&: The signature passed verification. It is valid.
36676 .endlist
36677 .vitem &%$dkim_verify_reason%&
36678 A string giving a litte bit more detail when &%$dkim_verify_status%& is either
36679 "fail" or "invalid". One of
36680 .ilist
36681 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
36682 key for the domain could not be retrieved. This may be a temporary problem.
36683 .next
36684 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
36685 record for the domain is syntactically invalid.
36686 .next
36687 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
36688 body hash does not match the one specified in the signature header. This
36689 means that the message body was modified in transit.
36690 .next
36691 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
36692 could not be verified. This may mean that headers were modified,
36693 re-written or otherwise changed in a way which is incompatible with
36694 DKIM verification. It may of course also mean that the signature is forged.
36695 .endlist
36696 .vitem &%$dkim_domain%&
36697 The signing domain. IMPORTANT: This variable is only populated if there is
36698 an actual signature in the message for the current domain or identity (as
36699 reflected by &%$dkim_cur_signer%&).
36700 .vitem &%$dkim_identity%&
36701 The signing identity, if present. IMPORTANT: This variable is only populated
36702 if there is an actual signature in the message for the current domain or
36703 identity (as reflected by &%$dkim_cur_signer%&).
36704 .vitem &%$dkim_selector%&
36705 The key record selector string.
36706 .vitem &%$dkim_algo%&
36707 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
36708 .vitem &%$dkim_canon_body%&
36709 The body canonicalization method. One of 'relaxed' or 'simple'.
36710 .vitem &%dkim_canon_headers%&
36711 The header canonicalization method. One of 'relaxed' or 'simple'.
36712 .vitem &%$dkim_copiedheaders%&
36713 A transcript of headers and their values which are included in the signature
36714 (copied from the 'z=' tag of the signature).
36715 .vitem &%$dkim_bodylength%&
36716 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
36717 limit was set by the signer, "9999999999999" is returned. This makes sure
36718 that this variable always expands to an integer value.
36719 .vitem &%$dkim_created%&
36720 UNIX timestamp reflecting the date and time when the signature was created.
36721 When this was not specified by the signer, "0" is returned.
36722 .vitem &%$dkim_expires%&
36723 UNIX timestamp reflecting the date and time when the signer wants the
36724 signature to be treated as "expired". When this was not specified by the
36725 signer, "9999999999999" is returned. This makes it possible to do useful
36726 integer size comparisons against this value.
36727 .vitem &%$dkim_headernames%&
36728 A colon-separated list of names of headers included in the signature.
36729 .vitem &%$dkim_key_testing%&
36730 "1" if the key record has the "testing" flag set, "0" if not.
36731 .vitem &%$dkim_key_nosubdomains%&
36732 "1" if the key record forbids subdomaining, "0" otherwise.
36733 .vitem &%$dkim_key_srvtype%&
36734 Service type (tag s=) from the key record. Defaults to "*" if not specified
36735 in the key record.
36736 .vitem &%$dkim_key_granularity%&
36737 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
36738 in the key record.
36739 .vitem &%$dkim_key_notes%&
36740 Notes from the key record (tag n=).
36741 .endlist
36742
36743 In addition, two ACL conditions are provided:
36744
36745 .vlist
36746 .vitem &%dkim_signers%&
36747 ACL condition that checks a colon-separated list of domains or identities
36748 for a match against the domain or identity that the ACL is currently verifying
36749 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
36750 verb to a group of domains or identities. For example:
36751
36752 .code
36753 # Warn when Mail purportedly from GMail has no signature at all
36754 warn log_message = GMail sender without DKIM signature
36755 sender_domains = gmail.com
36756 dkim_signers = gmail.com
36757 dkim_status = none
36758 .endd
36759
36760 .vitem &%dkim_status%&
36761 ACL condition that checks a colon-separated list of possible DKIM verification
36762 results against the actual result of verification. This is typically used
36763 to restrict an ACL verb to a list of verification outcomes, for example:
36764
36765 .code
36766 deny message = Mail from Paypal with invalid/missing signature
36767 sender_domains = paypal.com:paypal.de
36768 dkim_signers = paypal.com:paypal.de
36769 dkim_status = none:invalid:fail
36770 .endd
36771
36772 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
36773 see the documentation of the &%$dkim_verify_status%& expansion variable above
36774 for more information of what they mean.
36775 .endlist
36776
36777 . ////////////////////////////////////////////////////////////////////////////
36778 . ////////////////////////////////////////////////////////////////////////////
36779
36780 .chapter "Adding new drivers or lookup types" "CHID13" &&&
36781 "Adding drivers or lookups"
36782 .cindex "adding drivers"
36783 .cindex "new drivers, adding"
36784 .cindex "drivers" "adding new"
36785 The following actions have to be taken in order to add a new router, transport,
36786 authenticator, or lookup type to Exim:
36787
36788 .olist
36789 Choose a name for the driver or lookup type that does not conflict with any
36790 existing name; I will use &"newdriver"& in what follows.
36791 .next
36792 Add to &_src/EDITME_& the line:
36793 .display
36794 <&'type'&>&`_NEWDRIVER=yes`&
36795 .endd
36796 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
36797 code is not to be included in the binary by default, comment this line out. You
36798 should also add any relevant comments about the driver or lookup type.
36799 .next
36800 Add to &_src/config.h.defaults_& the line:
36801 .code
36802 #define <type>_NEWDRIVER
36803 .endd
36804 .next
36805 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
36806 and create a table entry as is done for all the other drivers and lookup types.
36807 .next
36808 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
36809 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
36810 Add your &`NEWDRIVER`& to that list.
36811 As long as the dynamic module would be named &_newdriver.so_&, you can use the
36812 simple form that most lookups have.
36813 .next
36814 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
36815 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
36816 driver or lookup type and add it to the definition of OBJ.
36817 .next
36818 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
36819 &_src_&.
36820 .next
36821 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
36822 as for other drivers and lookups.
36823 .endlist
36824
36825 Then all you need to do is write the code! A good way to start is to make a
36826 proforma by copying an existing module of the same type, globally changing all
36827 occurrences of the name, and cutting out most of the code. Note that any
36828 options you create must be listed in alphabetical order, because the tables are
36829 searched using a binary chop procedure.
36830
36831 There is a &_README_& file in each of the sub-directories of &_src_& describing
36832 the interface that is expected.
36833
36834
36835
36836
36837 . ////////////////////////////////////////////////////////////////////////////
36838 . ////////////////////////////////////////////////////////////////////////////
36839
36840 . /////////////////////////////////////////////////////////////////////////////
36841 . These lines are processing instructions for the Simple DocBook Processor that
36842 . Philip Hazel has developed as a less cumbersome way of making PostScript and
36843 . PDFs than using xmlto and fop. They will be ignored by all other XML
36844 . processors.
36845 . /////////////////////////////////////////////////////////////////////////////
36846
36847 .literal xml
36848 <?sdop
36849 format="newpage"
36850 foot_right_recto="&chaptertitle;"
36851 foot_right_verso="&chaptertitle;"
36852 ?>
36853 .literal off
36854
36855 .makeindex "Options index" "option"
36856 .makeindex "Variables index" "variable"
36857 .makeindex "Concept index" "concept"
36858
36859
36860 . /////////////////////////////////////////////////////////////////////////////
36861 . /////////////////////////////////////////////////////////////////////////////