Remove references to PCRE documentation no longer supplied with Exim.
[exim.git] / doc / doc-docbook / spec.xfpt
1 . $Cambridge: exim/doc/doc-docbook/spec.xfpt,v 1.38 2008/02/26 11:46:33 fanf2 Exp $
2 .
3 . /////////////////////////////////////////////////////////////////////////////
4 . This is the primary source of the Exim Manual. It is an xfpt document that is
5 . converted into DocBook XML for subsequent conversion into printing and online
6 . formats. The markup used herein is "standard" xfpt markup, with some extras.
7 . The markup is summarized in a file called Markup.txt.
8 .
9 . WARNING: When you use the .new macro, make sure it appears *before* any
10 . adjacent index items; otherwise you get an empty "paragraph" which causes
11 . unwanted vertical space.
12 . /////////////////////////////////////////////////////////////////////////////
13
14 .include stdflags
15 .include stdmacs
16
17 . /////////////////////////////////////////////////////////////////////////////
18 . This outputs the standard DocBook boilerplate.
19 . /////////////////////////////////////////////////////////////////////////////
20
21 .docbook
22
23 . /////////////////////////////////////////////////////////////////////////////
24 . These lines are processing instructions for the Simple DocBook Processor that
25 . Philip Hazel has developed as a less cumbersome way of making PostScript and
26 . PDFs than using xmlto and fop. They will be ignored by all other XML
27 . processors.
28 . /////////////////////////////////////////////////////////////////////////////
29
30 .literal xml
31 <?sdop
32 foot_right_recto="&chaptertitle; (&chapternumber;)"
33 foot_right_verso="&chaptertitle; (&chapternumber;)"
34 toc_chapter_blanks="yes,yes"
35 table_warn_overflow="overprint"
36 ?>
37 .literal off
38
39 . /////////////////////////////////////////////////////////////////////////////
40 . This generate the outermost <book> element that wraps then entire document.
41 . /////////////////////////////////////////////////////////////////////////////
42
43 .book
44
45 . /////////////////////////////////////////////////////////////////////////////
46 . These definitions set some parameters and save some typing. Remember that
47 . the <bookinfo> element must also be updated for each new edition.
48 . /////////////////////////////////////////////////////////////////////////////
49
50 .set previousversion "4.69"
51 .set version "4.70"
52
53 .set ACL "access control lists (ACLs)"
54 .set I "&nbsp;&nbsp;&nbsp;&nbsp;"
55
56
57 . /////////////////////////////////////////////////////////////////////////////
58 . Additional xfpt markup used by this document, over and above the default
59 . provided in the xfpt library.
60 . /////////////////////////////////////////////////////////////////////////////
61
62 . --- Override the &$ flag to automatically insert a $ with the variable name
63
64 .flag &$ $& "<varname>$" "</varname>"
65
66 . --- Short flags for daggers in option headings. They will always be inside
67 . --- an italic string, but we want the daggers to be roman.
68
69 .flag &!! "</emphasis>&dagger;<emphasis>"
70 .flag &!? "</emphasis>&Dagger;<emphasis>"
71
72 . --- A macro for an Exim option definition heading, generating a one-line
73 . --- table with four columns. For cases when the option name is given with
74 . --- a space, so that it can be split, a fifth argument is used for the
75 . --- index entry.
76
77 .macro option
78 .arg 5
79 .oindex "&%$5%&"
80 .endarg
81 .arg -5
82 .oindex "&%$1%&"
83 .endarg
84 .itable all 0 0 4 8* left 6* center 6* center 6* right
85 .row "&%$1%&" "Use: &'$2'&" "Type: &'$3'&" "Default: &'$4'&"
86 .endtable
87 .endmacro
88
89 . --- A macro for the common 2-column tables. The width of the first column
90 . --- is suitable for the many tables at the start of the main options chapter;
91 . --- the small number of other 2-column tables override it.
92
93 .macro table2 196pt 254pt
94 .itable none 0 0 2 $1 left $2 left
95 .endmacro
96
97 . --- A macro that generates .row, but puts &I; at the start of the first
98 . --- argument, thus indenting it. Assume a minimum of two arguments, and
99 . --- allow up to four arguments, which is as many as we'll ever need.
100
101 .macro irow
102 .arg 4
103 .row "&I;$1" "$2" "$3" "$4"
104 .endarg
105 .arg -4
106 .arg 3
107 .row "&I;$1" "$2" "$3"
108 .endarg
109 .arg -3
110 .row "&I;$1" "$2"
111 .endarg
112 .endarg
113 .endmacro
114
115 . --- Macros for option, variable, and concept index entries. For a "range"
116 . --- style of entry, use .scindex for the start and .ecindex for the end. The
117 . --- first argument of .scindex and the only argument of .ecindex must be the
118 . --- ID that ties them together.
119
120 .macro cindex
121 &<indexterm role="concept">&
122 &<primary>&$1&</primary>&
123 .arg 2
124 &<secondary>&$2&</secondary>&
125 .endarg
126 &</indexterm>&
127 .endmacro
128
129 .macro scindex
130 &<indexterm role="concept" id="$1" class="startofrange">&
131 &<primary>&$2&</primary>&
132 .arg 3
133 &<secondary>&$3&</secondary>&
134 .endarg
135 &</indexterm>&
136 .endmacro
137
138 .macro ecindex
139 &<indexterm role="concept" startref="$1" class="endofrange"/>&
140 .endmacro
141
142 .macro oindex
143 &<indexterm role="option">&
144 &<primary>&$1&</primary>&
145 .arg 2
146 &<secondary>&$2&</secondary>&
147 .endarg
148 &</indexterm>&
149 .endmacro
150
151 .macro vindex
152 &<indexterm role="variable">&
153 &<primary>&$1&</primary>&
154 .arg 2
155 &<secondary>&$2&</secondary>&
156 .endarg
157 &</indexterm>&
158 .endmacro
159
160 .macro index
161 .echo "** Don't use .index; use .cindex or .oindex or .vindex"
162 .endmacro
163 . ////////////////////////////////////////////////////////////////////////////
164
165
166 . ////////////////////////////////////////////////////////////////////////////
167 . The <bookinfo> element is removed from the XML before processing for Ascii
168 . output formats.
169 . ////////////////////////////////////////////////////////////////////////////
170
171 .literal xml
172 <bookinfo>
173 <title>Specification of the Exim Mail Transfer Agent</title>
174 <titleabbrev>The Exim MTA</titleabbrev>
175 <date>23 August 2007</date>
176 <author><firstname>Philip</firstname><surname>Hazel</surname></author>
177 <authorinitials>PH</authorinitials>
178 <affiliation><orgname>University of Cambridge Computing Service</orgname></affiliation>
179 <address>New Museums Site, Pembroke Street, Cambridge CB2 3QH, England</address>
180 <revhistory><revision>
181 <revnumber>4.68</revnumber>
182 <date>23 August 2007</date>
183 <authorinitials>PH</authorinitials>
184 </revision></revhistory>
185 <copyright><year>2007</year><holder>University of Cambridge</holder></copyright>
186 </bookinfo>
187 .literal off
188
189
190 . /////////////////////////////////////////////////////////////////////////////
191 . This chunk of literal XML implements index entries of the form "x, see y" and
192 . "x, see also y". However, the DocBook DTD doesn't allow <indexterm> entries
193 . at the top level, so we have to put the .chapter directive first.
194 . /////////////////////////////////////////////////////////////////////////////
195
196 .chapter "Introduction" "CHID1"
197 .literal xml
198
199 <indexterm role="variable">
200 <primary>$1, $2, etc.</primary>
201 <see><emphasis>numerical variables</emphasis></see>
202 </indexterm>
203 <indexterm role="concept">
204 <primary>address</primary>
205 <secondary>rewriting</secondary>
206 <see><emphasis>rewriting</emphasis></see>
207 </indexterm>
208 <indexterm role="concept">
209 <primary>Bounce Address Tag Validation</primary>
210 <see><emphasis>BATV</emphasis></see>
211 </indexterm>
212 <indexterm role="concept">
213 <primary>Client SMTP Authorization</primary>
214 <see><emphasis>CSA</emphasis></see>
215 </indexterm>
216 <indexterm role="concept">
217 <primary>CR character</primary>
218 <see><emphasis>carriage return</emphasis></see>
219 </indexterm>
220 <indexterm role="concept">
221 <primary>CRL</primary>
222 <see><emphasis>certificate revocation list</emphasis></see>
223 </indexterm>
224 <indexterm role="concept">
225 <primary>delivery</primary>
226 <secondary>failure report</secondary>
227 <see><emphasis>bounce message</emphasis></see>
228 </indexterm>
229 <indexterm role="concept">
230 <primary>dialup</primary>
231 <see><emphasis>intermittently connected hosts</emphasis></see>
232 </indexterm>
233 <indexterm role="concept">
234 <primary>exiscan</primary>
235 <see><emphasis>content scanning</emphasis></see>
236 </indexterm>
237 <indexterm role="concept">
238 <primary>failover</primary>
239 <see><emphasis>fallback</emphasis></see>
240 </indexterm>
241 <indexterm role="concept">
242 <primary>fallover</primary>
243 <see><emphasis>fallback</emphasis></see>
244 </indexterm>
245 <indexterm role="concept">
246 <primary>filter</primary>
247 <secondary>Sieve</secondary>
248 <see><emphasis>Sieve filter</emphasis></see>
249 </indexterm>
250 <indexterm role="concept">
251 <primary>ident</primary>
252 <see><emphasis>RFC 1413</emphasis></see>
253 </indexterm>
254 <indexterm role="concept">
255 <primary>LF character</primary>
256 <see><emphasis>linefeed</emphasis></see>
257 </indexterm>
258 <indexterm role="concept">
259 <primary>maximum</primary>
260 <seealso><emphasis>limit</emphasis></seealso>
261 </indexterm>
262 <indexterm role="concept">
263 <primary>monitor</primary>
264 <see><emphasis>Exim monitor</emphasis></see>
265 </indexterm>
266 <indexterm role="concept">
267 <primary>no_<emphasis>xxx</emphasis></primary>
268 <see>entry for xxx</see>
269 </indexterm>
270 <indexterm role="concept">
271 <primary>NUL</primary>
272 <see><emphasis>binary zero</emphasis></see>
273 </indexterm>
274 <indexterm role="concept">
275 <primary>passwd file</primary>
276 <see><emphasis>/etc/passwd</emphasis></see>
277 </indexterm>
278 <indexterm role="concept">
279 <primary>process id</primary>
280 <see><emphasis>pid</emphasis></see>
281 </indexterm>
282 <indexterm role="concept">
283 <primary>RBL</primary>
284 <see><emphasis>DNS list</emphasis></see>
285 </indexterm>
286 <indexterm role="concept">
287 <primary>redirection</primary>
288 <see><emphasis>address redirection</emphasis></see>
289 </indexterm>
290 <indexterm role="concept">
291 <primary>return path</primary>
292 <seealso><emphasis>envelope sender</emphasis></seealso>
293 </indexterm>
294 <indexterm role="concept">
295 <primary>scanning</primary>
296 <see><emphasis>content scanning</emphasis></see>
297 </indexterm>
298 <indexterm role="concept">
299 <primary>SSL</primary>
300 <see><emphasis>TLS</emphasis></see>
301 </indexterm>
302 <indexterm role="concept">
303 <primary>string</primary>
304 <secondary>expansion</secondary>
305 <see><emphasis>expansion</emphasis></see>
306 </indexterm>
307 <indexterm role="concept">
308 <primary>top bit</primary>
309 <see><emphasis>8-bit characters</emphasis></see>
310 </indexterm>
311 <indexterm role="concept">
312 <primary>variables</primary>
313 <see><emphasis>expansion, variables</emphasis></see>
314 </indexterm>
315 <indexterm role="concept">
316 <primary>zero, binary</primary>
317 <see><emphasis>binary zero</emphasis></see>
318 </indexterm>
319
320 .literal off
321
322
323 . /////////////////////////////////////////////////////////////////////////////
324 . This is the real start of the first chapter. See the comment above as to why
325 . we can't have the .chapter line here.
326 . chapter "Introduction"
327 . /////////////////////////////////////////////////////////////////////////////
328
329 Exim is a mail transfer agent (MTA) for hosts that are running Unix or
330 Unix-like operating systems. It was designed on the assumption that it would be
331 run on hosts that are permanently connected to the Internet. However, it can be
332 used on intermittently connected hosts with suitable configuration adjustments.
333
334 Configuration files currently exist for the following operating systems: AIX,
335 BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd,
336 GNU/Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD,
337 OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4,
338 Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and Unixware.
339 Some of these operating systems are no longer current and cannot easily be
340 tested, so the configuration files may no longer work in practice.
341
342 There are also configuration files for compiling Exim in the Cygwin environment
343 that can be installed on systems running Windows. However, this document does
344 not contain any information about running Exim in the Cygwin environment.
345
346 The terms and conditions for the use and distribution of Exim are contained in
347 the file &_NOTICE_&. Exim is distributed under the terms of the GNU General
348 Public Licence, a copy of which may be found in the file &_LICENCE_&.
349
350 The use, supply or promotion of Exim for the purpose of sending bulk,
351 unsolicited electronic mail is incompatible with the basic aims of the program,
352 which revolve around the free provision of a service that enhances the quality
353 of personal communications. The author of Exim regards indiscriminate
354 mass-mailing as an antisocial, irresponsible abuse of the Internet.
355
356 Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
357 experience of running and working on the Smail 3 code, I could never have
358 contemplated starting to write a new MTA. Many of the ideas and user interfaces
359 were originally taken from Smail 3, though the actual code of Exim is entirely
360 new, and has developed far beyond the initial concept.
361
362 Many people, both in Cambridge and around the world, have contributed to the
363 development and the testing of Exim, and to porting it to various operating
364 systems. I am grateful to them all. The distribution now contains a file called
365 &_ACKNOWLEDGMENTS_&, in which I have started recording the names of
366 contributors.
367
368
369 .section "Exim documentation" "SECID1"
370 . Keep this example change bar when updating the documentation!
371 .new
372 .cindex "documentation"
373 This edition of the Exim specification applies to version &version; of Exim.
374 Substantive changes from the &previousversion; edition are marked in some
375 renditions of the document; this paragraph is so marked if the rendition is
376 capable of showing a change indicator.
377 .wen
378
379 This document is very much a reference manual; it is not a tutorial. The reader
380 is expected to have some familiarity with the SMTP mail transfer protocol and
381 with general Unix system administration. Although there are some discussions
382 and examples in places, the information is mostly organized in a way that makes
383 it easy to look up, rather than in a natural order for sequential reading.
384 Furthermore, the manual aims to cover every aspect of Exim in detail, including
385 a number of rarely-used, special-purpose features that are unlikely to be of
386 very wide interest.
387
388 .cindex "books about Exim"
389 An &"easier"& discussion of Exim which provides more in-depth explanatory,
390 introductory, and tutorial material can be found in a book entitled &'The Exim
391 SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge
392 (&url(http://www.uit.co.uk/exim-book/)).
393
394 This book also contains a chapter that gives a general introduction to SMTP and
395 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
396 with the latest release of Exim. (Note that the earlier book about Exim,
397 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
398
399 .cindex "Debian" "information sources"
400 If you are using a Debian distribution of Exim, you will find information about
401 Debian-specific features in the file
402 &_/usr/share/doc/exim4-base/README.Debian_&.
403 The command &(man update-exim.conf)& is another source of Debian-specific
404 information.
405
406 .cindex "&_doc/NewStuff_&"
407 .cindex "&_doc/ChangeLog_&"
408 .cindex "change log"
409 As the program develops, there may be features in newer versions that have not
410 yet made it into this document, which is updated only when the most significant
411 digit of the fractional part of the version number changes. Specifications of
412 new features that are not yet in this manual are placed in the file
413 &_doc/NewStuff_& in the Exim distribution.
414
415 Some features may be classified as &"experimental"&. These may change
416 incompatibly while they are developing, or even be withdrawn. For this reason,
417 they are not documented in this manual. Information about experimental features
418 can be found in the file &_doc/experimental.txt_&.
419
420 All changes to the program (whether new features, bug fixes, or other kinds of
421 change) are noted briefly in the file called &_doc/ChangeLog_&.
422
423 .cindex "&_doc/spec.txt_&"
424 This specification itself is available as an ASCII file in &_doc/spec.txt_& so
425 that it can easily be searched with a text editor. Other files in the &_doc_&
426 directory are:
427
428 .table2 100pt
429 .row &_OptionLists.txt_& "list of all options in alphabetical order"
430 .row &_dbm.discuss.txt_& "discussion about DBM libraries"
431 .row &_exim.8_& "a man page of Exim's command line options"
432 .row &_experimental.txt_& "documentation of experimental features"
433 .row &_filter.txt_& "specification of the filter language"
434 .row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3"
435 .row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4"
436 .endtable
437
438 The main specification and the specification of the filtering language are also
439 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
440 &<<SECTavail>>& below tells you how to get hold of these.
441
442
443
444 .section "FTP and web sites" "SECID2"
445 .cindex "web site"
446 .cindex "FTP site"
447 The primary site for Exim source distributions is currently the University of
448 Cambridge's FTP site, whose contents are described in &'Where to find the Exim
449 distribution'& below. In addition, there is a web site and an FTP site at
450 &%exim.org%&. These are now also hosted at the University of Cambridge. The
451 &%exim.org%& site was previously hosted for a number of years by Energis
452 Squared, formerly Planet Online Ltd, whose support I gratefully acknowledge.
453
454 .cindex "wiki"
455 .cindex "FAQ"
456 As well as Exim distribution tar files, the Exim web site contains a number of
457 differently formatted versions of the documentation. A recent addition to the
458 online information is the Exim wiki (&url(http://wiki.exim.org)),
459 which contains what used to be a separate FAQ, as well as various other
460 examples, tips, and know-how that have been contributed by Exim users.
461
462 .cindex Bugzilla
463 An Exim Bugzilla exists at &url(http://bugs.exim.org). You can use
464 this to report bugs, and also to add items to the wish list. Please search
465 first to check that you are not duplicating a previous entry.
466
467
468
469 .section "Mailing lists" "SECID3"
470 .cindex "mailing lists" "for Exim users"
471 The following Exim mailing lists exist:
472
473 .table2 140pt
474 .row &'exim-users@exim.org'& "General discussion list"
475 .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc."
476 .row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
477 .row &'exim-future@exim.org'& "Discussion of long-term development"
478 .endtable
479
480 You can subscribe to these lists, change your existing subscriptions, and view
481 or search the archives via the mailing lists link on the Exim home page.
482 .cindex "Debian" "mailing list for"
483 If you are using a Debian distribution of Exim, you may wish to subscribe to
484 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
485 via this web page:
486 .display
487 &url(http://lists.alioth.debian.org/mailman/listinfo/pkg-exim4-users)
488 .endd
489 Please ask Debian-specific questions on this list and not on the general Exim
490 lists.
491
492 .section "Exim training" "SECID4"
493 .cindex "training courses"
494 Training courses in Cambridge (UK) used to be run annually by the author of
495 Exim, before he retired. At the time of writing, there are no plans to run
496 further Exim courses in Cambridge. However, if that changes, relevant
497 information will be posted at &url(http://www-tus.csx.cam.ac.uk/courses/exim/).
498
499 .section "Bug reports" "SECID5"
500 .cindex "bug reports"
501 .cindex "reporting bugs"
502 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
503 via the Bugzilla (&url(http://bugs.exim.org)). However, if you are unsure
504 whether some behaviour is a bug or not, the best thing to do is to post a
505 message to the &'exim-dev'& mailing list and have it discussed.
506
507
508
509 .section "Where to find the Exim distribution" "SECTavail"
510 .cindex "FTP site"
511 .cindex "distribution" "ftp site"
512 The master ftp site for the Exim distribution is
513 .display
514 &*ftp://ftp.csx.cam.ac.uk/pub/software/email/exim*&
515 .endd
516 This is mirrored by
517 .display
518 &*ftp://ftp.exim.org/pub/exim*&
519 .endd
520 The file references that follow are relative to the &_exim_& directories at
521 these sites. There are now quite a number of independent mirror sites around
522 the world. Those that I know about are listed in the file called &_Mirrors_&.
523
524 Within the &_exim_& directory there are subdirectories called &_exim3_& (for
525 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
526 distributions), and &_Testing_& for testing versions. In the &_exim4_&
527 subdirectory, the current release can always be found in files called
528 .display
529 &_exim-n.nn.tar.gz_&
530 &_exim-n.nn.tar.bz2_&
531 .endd
532 where &'n.nn'& is the highest such version number in the directory. The two
533 files contain identical data; the only difference is the type of compression.
534 The &_.bz2_& file is usually a lot smaller than the &_.gz_& file.
535
536 .cindex "distribution" "signing details"
537 .cindex "distribution" "public key"
538 .cindex "public key for signed distribution"
539 The distributions are currently signed with Nigel Metheringham's GPG key. The
540 corresponding public key is available from a number of keyservers, and there is
541 also a copy in the file &_nigel-pubkey.asc_&. The signatures for the tar bundles are
542 in:
543 .display
544 &_exim-n.nn.tar.gz.asc_&
545 &_exim-n.nn.tar.bz2.asc_&
546 .endd
547 For each released version, the log of changes is made separately available in a
548 separate file in the directory &_ChangeLogs_& so that it is possible to
549 find out what has changed without having to download the entire distribution.
550
551 .cindex "documentation" "available formats"
552 The main distribution contains ASCII versions of this specification and other
553 documentation; other formats of the documents are available in separate files
554 inside the &_exim4_& directory of the FTP site:
555 .display
556 &_exim-html-n.nn.tar.gz_&
557 &_exim-pdf-n.nn.tar.gz_&
558 &_exim-postscript-n.nn.tar.gz_&
559 &_exim-texinfo-n.nn.tar.gz_&
560 .endd
561 These tar files contain only the &_doc_& directory, not the complete
562 distribution, and are also available in &_.bz2_& as well as &_.gz_& forms.
563
564
565 .section "Limitations" "SECID6"
566 .ilist
567 .cindex "limitations of Exim"
568 .cindex "bang paths" "not handled by Exim"
569 Exim is designed for use as an Internet MTA, and therefore handles addresses in
570 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
571 simple two-component bang paths can be converted by a straightforward rewriting
572 configuration. This restriction does not prevent Exim from being interfaced to
573 UUCP as a transport mechanism, provided that domain addresses are used.
574 .next
575 .cindex "domainless addresses"
576 .cindex "address" "without domain"
577 Exim insists that every address it handles has a domain attached. For incoming
578 local messages, domainless addresses are automatically qualified with a
579 configured domain value. Configuration options specify from which remote
580 systems unqualified addresses are acceptable. These are then qualified on
581 arrival.
582 .next
583 .cindex "transport" "external"
584 .cindex "external transports"
585 The only external transport mechanisms that are currently implemented are SMTP
586 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
587 transport is available, and there are facilities for writing messages to files
588 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
589 to send messages to other transport mechanisms such as UUCP, provided they can
590 handle domain-style addresses. Batched SMTP input is also catered for.
591 .next
592 Exim is not designed for storing mail for dial-in hosts. When the volumes of
593 such mail are large, it is better to get the messages &"delivered"& into files
594 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
595 other means.
596 .next
597 Although Exim does have basic facilities for scanning incoming messages, these
598 are not comprehensive enough to do full virus or spam scanning. Such operations
599 are best carried out using additional specialized software packages. If you
600 compile Exim with the content-scanning extension, straightforward interfaces to
601 a number of common scanners are provided.
602 .endlist
603
604
605 .section "Run time configuration" "SECID7"
606 Exim's run time configuration is held in a single text file that is divided
607 into a number of sections. The entries in this file consist of keywords and
608 values, in the style of Smail 3 configuration files. A default configuration
609 file which is suitable for simple online installations is provided in the
610 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
611
612
613 .section "Calling interface" "SECID8"
614 .cindex "Sendmail compatibility" "command line interface"
615 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
616 can be a straight replacement for &_/usr/lib/sendmail_& or
617 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
618 about Sendmail in order to run Exim. For actions other than sending messages,
619 Sendmail-compatible options also exist, but those that produce output (for
620 example, &%-bp%&, which lists the messages on the queue) do so in Exim's own
621 format. There are also some additional options that are compatible with Smail
622 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
623 documents all Exim's command line options. This information is automatically
624 made into the man page that forms part of the Exim distribution.
625
626 Control of messages on the queue can be done via certain privileged command
627 line options. There is also an optional monitor program called &'eximon'&,
628 which displays current information in an X window, and which contains a menu
629 interface to Exim's command line administration options.
630
631
632
633 .section "Terminology" "SECID9"
634 .cindex "terminology definitions"
635 .cindex "body of message" "definition of"
636 The &'body'& of a message is the actual data that the sender wants to transmit.
637 It is the last part of a message, and is separated from the &'header'& (see
638 below) by a blank line.
639
640 .cindex "bounce message" "definition of"
641 When a message cannot be delivered, it is normally returned to the sender in a
642 delivery failure message or a &"non-delivery report"& (NDR). The term
643 &'bounce'& is commonly used for this action, and the error reports are often
644 called &'bounce messages'&. This is a convenient shorthand for &"delivery
645 failure error report"&. Such messages have an empty sender address in the
646 message's &'envelope'& (see below) to ensure that they cannot themselves give
647 rise to further bounce messages.
648
649 The term &'default'& appears frequently in this manual. It is used to qualify a
650 value which is used in the absence of any setting in the configuration. It may
651 also qualify an action which is taken unless a configuration setting specifies
652 otherwise.
653
654 The term &'defer'& is used when the delivery of a message to a specific
655 destination cannot immediately take place for some reason (a remote host may be
656 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
657 until a later time.
658
659 The word &'domain'& is sometimes used to mean all but the first component of a
660 host's name. It is &'not'& used in that sense here, where it normally refers to
661 the part of an email address following the @ sign.
662
663 .cindex "envelope, definition of"
664 .cindex "sender" "definition of"
665 A message in transit has an associated &'envelope'&, as well as a header and a
666 body. The envelope contains a sender address (to which bounce messages should
667 be delivered), and any number of recipient addresses. References to the
668 sender or the recipients of a message usually mean the addresses in the
669 envelope. An MTA uses these addresses for delivery, and for returning bounce
670 messages, not the addresses that appear in the header lines.
671
672 .cindex "message" "header, definition of"
673 .cindex "header section" "definition of"
674 The &'header'& of a message is the first part of a message's text, consisting
675 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
676 &'Subject:'&, etc. Long header lines can be split over several text lines by
677 indenting the continuations. The header is separated from the body by a blank
678 line.
679
680 .cindex "local part" "definition of"
681 .cindex "domain" "definition of"
682 The term &'local part'&, which is taken from RFC 2822, is used to refer to that
683 part of an email address that precedes the @ sign. The part that follows the
684 @ sign is called the &'domain'& or &'mail domain'&.
685
686 .cindex "local delivery" "definition of"
687 .cindex "remote delivery, definition of"
688 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
689 delivery to a file or a pipe on the local host from delivery by SMTP over
690 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
691 host it is running on are &'remote'&.
692
693 .cindex "return path" "definition of"
694 &'Return path'& is another name that is used for the sender address in a
695 message's envelope.
696
697 .cindex "queue" "definition of"
698 The term &'queue'& is used to refer to the set of messages awaiting delivery,
699 because this term is in widespread use in the context of MTAs. However, in
700 Exim's case the reality is more like a pool than a queue, because there is
701 normally no ordering of waiting messages.
702
703 .cindex "queue runner" "definition of"
704 The term &'queue runner'& is used to describe a process that scans the queue
705 and attempts to deliver those messages whose retry times have come. This term
706 is used by other MTAs, and also relates to the command &%runq%&, but in Exim
707 the waiting messages are normally processed in an unpredictable order.
708
709 .cindex "spool directory" "definition of"
710 The term &'spool directory'& is used for a directory in which Exim keeps the
711 messages on its queue &-- that is, those that it is in the process of
712 delivering. This should not be confused with the directory in which local
713 mailboxes are stored, which is called a &"spool directory"& by some people. In
714 the Exim documentation, &"spool"& is always used in the first sense.
715
716
717
718
719
720
721 . ////////////////////////////////////////////////////////////////////////////
722 . ////////////////////////////////////////////////////////////////////////////
723
724 .chapter "Incorporated code" "CHID2"
725 .cindex "incorporated code"
726 .cindex "regular expressions" "library"
727 .cindex "PCRE"
728 A number of pieces of external code are included in the Exim distribution.
729
730 .ilist
731 Regular expressions are supported in the main Exim program and in the
732 Exim monitor using the freely-distributable PCRE library, copyright
733 &copy; University of Cambridge. The source to PCRE is no longer shipped with
734 Exim, so you will need to use the version of PCRE shipped with your system,
735 or obtain and install the full version of the library from
736 &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
737 .next
738 .cindex "cdb" "acknowledgment"
739 Support for the cdb (Constant DataBase) lookup method is provided by code
740 contributed by Nigel Metheringham of (at the time he contributed it) Planet
741 Online Ltd. The implementation is completely contained within the code of Exim.
742 It does not link against an external cdb library. The code contains the
743 following statements:
744
745 .blockquote
746 Copyright &copy; 1998 Nigel Metheringham, Planet Online Ltd
747
748 This program is free software; you can redistribute it and/or modify it under
749 the terms of the GNU General Public License as published by the Free Software
750 Foundation; either version 2 of the License, or (at your option) any later
751 version.
752 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
753 the spec and sample code for cdb can be obtained from
754 &url(http://www.pobox.com/~djb/cdb.html). This implementation borrows
755 some code from Dan Bernstein's implementation (which has no license
756 restrictions applied to it).
757 .endblockquote
758 .next
759 .cindex "SPA authentication"
760 .cindex "Samba project"
761 .cindex "Microsoft Secure Password Authentication"
762 Client support for Microsoft's &'Secure Password Authentication'& is provided
763 by code contributed by Marc Prud'hommeaux. Server support was contributed by
764 Tom Kistner. This includes code taken from the Samba project, which is released
765 under the Gnu GPL.
766 .next
767 .cindex "Cyrus"
768 .cindex "&'pwcheck'& daemon"
769 .cindex "&'pwauthd'& daemon"
770 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
771 by code taken from the Cyrus-SASL library and adapted by Alexander S.
772 Sabourenkov. The permission notice appears below, in accordance with the
773 conditions expressed therein.
774
775 .blockquote
776 Copyright &copy; 2001 Carnegie Mellon University. All rights reserved.
777
778 Redistribution and use in source and binary forms, with or without
779 modification, are permitted provided that the following conditions
780 are met:
781
782 .olist
783 Redistributions of source code must retain the above copyright
784 notice, this list of conditions and the following disclaimer.
785 .next
786 Redistributions in binary form must reproduce the above copyright
787 notice, this list of conditions and the following disclaimer in
788 the documentation and/or other materials provided with the
789 distribution.
790 .next
791 The name &"Carnegie Mellon University"& must not be used to
792 endorse or promote products derived from this software without
793 prior written permission. For permission or any other legal
794 details, please contact
795 .display
796 Office of Technology Transfer
797 Carnegie Mellon University
798 5000 Forbes Avenue
799 Pittsburgh, PA 15213-3890
800 (412) 268-4387, fax: (412) 268-7395
801 tech-transfer@andrew.cmu.edu
802 .endd
803 .next
804 Redistributions of any form whatsoever must retain the following
805 acknowledgment:
806
807 &"This product includes software developed by Computing Services
808 at Carnegie Mellon University (&url(http://www.cmu.edu/computing/)."&
809
810 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
811 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
812 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
813 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
814 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
815 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
816 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
817 .endlist
818 .endblockquote
819
820 .next
821 .cindex "Exim monitor" "acknowledgment"
822 .cindex "X-windows"
823 .cindex "Athena"
824 The Exim Monitor program, which is an X-Window application, includes
825 modified versions of the Athena StripChart and TextPop widgets.
826 This code is copyright by DEC and MIT, and their permission notice appears
827 below, in accordance with the conditions expressed therein.
828
829 .blockquote
830 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
831 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
832
833 All Rights Reserved
834
835 Permission to use, copy, modify, and distribute this software and its
836 documentation for any purpose and without fee is hereby granted,
837 provided that the above copyright notice appear in all copies and that
838 both that copyright notice and this permission notice appear in
839 supporting documentation, and that the names of Digital or MIT not be
840 used in advertising or publicity pertaining to distribution of the
841 software without specific, written prior permission.
842
843 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
844 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
845 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
846 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
847 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
848 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
849 SOFTWARE.
850 .endblockquote
851
852 .next
853 Many people have contributed code fragments, some large, some small, that were
854 not covered by any specific licence requirements. It is assumed that the
855 contributors are happy to see their code incorporated into Exim under the GPL.
856 .endlist
857
858
859
860
861
862 . ////////////////////////////////////////////////////////////////////////////
863 . ////////////////////////////////////////////////////////////////////////////
864
865 .chapter "How Exim receives and delivers mail" "CHID11" &&&
866 "Receiving and delivering mail"
867
868
869 .section "Overall philosophy" "SECID10"
870 .cindex "design philosophy"
871 Exim is designed to work efficiently on systems that are permanently connected
872 to the Internet and are handling a general mix of mail. In such circumstances,
873 most messages can be delivered immediately. Consequently, Exim does not
874 maintain independent queues of messages for specific domains or hosts, though
875 it does try to send several messages in a single SMTP connection after a host
876 has been down, and it also maintains per-host retry information.
877
878
879 .section "Policy control" "SECID11"
880 .cindex "policy control" "overview"
881 Policy controls are now an important feature of MTAs that are connected to the
882 Internet. Perhaps their most important job is to stop MTAs being abused as
883 &"open relays"& by misguided individuals who send out vast amounts of
884 unsolicited junk, and want to disguise its source. Exim provides flexible
885 facilities for specifying policy controls on incoming mail:
886
887 .ilist
888 .cindex "&ACL;" "introduction"
889 Exim 4 (unlike previous versions of Exim) implements policy controls on
890 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
891 series of statements that may either grant or deny access. ACLs can be used at
892 several places in the SMTP dialogue while receiving a message from a remote
893 host. However, the most common places are after each RCPT command, and at the
894 very end of the message. The sysadmin can specify conditions for accepting or
895 rejecting individual recipients or the entire message, respectively, at these
896 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
897 error code.
898 .next
899 An ACL is also available for locally generated, non-SMTP messages. In this
900 case, the only available actions are to accept or deny the entire message.
901 .next
902 When Exim is compiled with the content-scanning extension, facilities are
903 provided in the ACL mechanism for passing the message to external virus and/or
904 spam scanning software. The result of such a scan is passed back to the ACL,
905 which can then use it to decide what to do with the message.
906 .next
907 When a message has been received, either from a remote host or from the local
908 host, but before the final acknowledgment has been sent, a locally supplied C
909 function called &[local_scan()]& can be run to inspect the message and decide
910 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
911 is accepted, the list of recipients can be modified by the function.
912 .next
913 Using the &[local_scan()]& mechanism is another way of calling external scanner
914 software. The &%SA-Exim%& add-on package works this way. It does not require
915 Exim to be compiled with the content-scanning extension.
916 .next
917 After a message has been accepted, a further checking mechanism is available in
918 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
919 runs at the start of every delivery process.
920 .endlist
921
922
923
924 .section "User filters" "SECID12"
925 .cindex "filter" "introduction"
926 .cindex "Sieve filter"
927 In a conventional Exim configuration, users are able to run private filters by
928 setting up appropriate &_.forward_& files in their home directories. See
929 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
930 configuration needed to support this, and the separate document entitled
931 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
932 of filtering are available:
933
934 .ilist
935 Sieve filters are written in the standard filtering language that is defined
936 by RFC 3028.
937 .next
938 Exim filters are written in a syntax that is unique to Exim, but which is more
939 powerful than Sieve, which it pre-dates.
940 .endlist
941
942 User filters are run as part of the routing process, described below.
943
944
945
946 .section "Message identification" "SECTmessiden"
947 .cindex "message ids" "details of format"
948 .cindex "format" "of message id"
949 .cindex "id of message"
950 .cindex "base62"
951 .cindex "base36"
952 .cindex "Darwin"
953 .cindex "Cygwin"
954 Every message handled by Exim is given a &'message id'& which is sixteen
955 characters long. It is divided into three parts, separated by hyphens, for
956 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
957 normally encoding numbers in base 62. However, in the Darwin operating
958 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
959 (avoiding the use of lower case letters) is used instead, because the message
960 id is used to construct file names, and the names of files in those systems are
961 not always case-sensitive.
962
963 .cindex "pid (process id)" "re-use of"
964 The detail of the contents of the message id have changed as Exim has evolved.
965 Earlier versions relied on the operating system not re-using a process id (pid)
966 within one second. On modern operating systems, this assumption can no longer
967 be made, so the algorithm had to be changed. To retain backward compatibility,
968 the format of the message id was retained, which is why the following rules are
969 somewhat eccentric:
970
971 .ilist
972 The first six characters of the message id are the time at which the message
973 started to be received, to a granularity of one second. That is, this field
974 contains the number of seconds since the start of the epoch (the normal Unix
975 way of representing the date and time of day).
976 .next
977 After the first hyphen, the next six characters are the id of the process that
978 received the message.
979 .next
980 There are two different possibilities for the final two characters:
981 .olist
982 .oindex "&%localhost_number%&"
983 If &%localhost_number%& is not set, this value is the fractional part of the
984 time of reception, normally in units of 1/2000 of a second, but for systems
985 that must use base 36 instead of base 62 (because of case-insensitive file
986 systems), the units are 1/1000 of a second.
987 .next
988 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
989 the fractional part of the time, which in this case is in units of 1/200
990 (1/100) of a second.
991 .endlist
992 .endlist
993
994 After a message has been received, Exim waits for the clock to tick at the
995 appropriate resolution before proceeding, so that if another message is
996 received by the same process, or by another process with the same (re-used)
997 pid, it is guaranteed that the time will be different. In most cases, the clock
998 will already have ticked while the message was being received.
999
1000
1001 .section "Receiving mail" "SECID13"
1002 .cindex "receiving mail"
1003 .cindex "message" "reception"
1004 The only way Exim can receive mail from another host is using SMTP over
1005 TCP/IP, in which case the sender and recipient addresses are transferred using
1006 SMTP commands. However, from a locally running process (such as a user's MUA),
1007 there are several possibilities:
1008
1009 .ilist
1010 If the process runs Exim with the &%-bm%& option, the message is read
1011 non-interactively (usually via a pipe), with the recipients taken from the
1012 command line, or from the body of the message if &%-t%& is also used.
1013 .next
1014 If the process runs Exim with the &%-bS%& option, the message is also read
1015 non-interactively, but in this case the recipients are listed at the start of
1016 the message in a series of SMTP RCPT commands, terminated by a DATA
1017 command. This is so-called &"batch SMTP"& format,
1018 but it isn't really SMTP. The SMTP commands are just another way of passing
1019 envelope addresses in a non-interactive submission.
1020 .next
1021 If the process runs Exim with the &%-bs%& option, the message is read
1022 interactively, using the SMTP protocol. A two-way pipe is normally used for
1023 passing data between the local process and the Exim process.
1024 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1025 example, the ACLs for SMTP commands are used for this form of submission.
1026 .next
1027 A local process may also make a TCP/IP call to the host's loopback address
1028 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1029 does not treat the loopback address specially. It treats all such connections
1030 in the same way as connections from other hosts.
1031 .endlist
1032
1033
1034 .cindex "message sender, constructed by Exim"
1035 .cindex "sender" "constructed by Exim"
1036 In the three cases that do not involve TCP/IP, the sender address is
1037 constructed from the login name of the user that called Exim and a default
1038 qualification domain (which can be set by the &%qualify_domain%& configuration
1039 option). For local or batch SMTP, a sender address that is passed using the
1040 SMTP MAIL command is ignored. However, the system administrator may allow
1041 certain users (&"trusted users"&) to specify a different sender address
1042 unconditionally, or all users to specify certain forms of different sender
1043 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1044 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1045 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1046 users to change sender addresses.
1047
1048 Messages received by either of the non-interactive mechanisms are subject to
1049 checking by the non-SMTP ACL, if one is defined. Messages received using SMTP
1050 (either over TCP/IP, or interacting with a local process) can be checked by a
1051 number of ACLs that operate at different times during the SMTP session. Either
1052 individual recipients, or the entire message, can be rejected if local policy
1053 requirements are not met. The &[local_scan()]& function (see chapter
1054 &<<CHAPlocalscan>>&) is run for all incoming messages.
1055
1056 Exim can be configured not to start a delivery process when a message is
1057 received; this can be unconditional, or depend on the number of incoming SMTP
1058 connections or the system load. In these situations, new messages wait on the
1059 queue until a queue runner process picks them up. However, in standard
1060 configurations under normal conditions, delivery is started as soon as a
1061 message is received.
1062
1063
1064
1065
1066
1067 .section "Handling an incoming message" "SECID14"
1068 .cindex "spool directory" "files that hold a message"
1069 .cindex "file" "how a message is held"
1070 When Exim accepts a message, it writes two files in its spool directory. The
1071 first contains the envelope information, the current status of the message, and
1072 the header lines, and the second contains the body of the message. The names of
1073 the two spool files consist of the message id, followed by &`-H`& for the
1074 file containing the envelope and header, and &`-D`& for the data file.
1075
1076 .cindex "spool directory" "&_input_& sub-directory"
1077 By default all these message files are held in a single directory called
1078 &_input_& inside the general Exim spool directory. Some operating systems do
1079 not perform very well if the number of files in a directory gets large; to
1080 improve performance in such cases, the &%split_spool_directory%& option can be
1081 used. This causes Exim to split up the input files into 62 sub-directories
1082 whose names are single letters or digits. When this is done, the queue is
1083 processed one sub-directory at a time instead of all at once, which can improve
1084 overall performance even when there are not enough files in each directory to
1085 affect file system performance.
1086
1087 The envelope information consists of the address of the message's sender and
1088 the addresses of the recipients. This information is entirely separate from
1089 any addresses contained in the header lines. The status of the message includes
1090 a list of recipients who have already received the message. The format of the
1091 first spool file is described in chapter &<<CHAPspool>>&.
1092
1093 .cindex "rewriting" "addresses"
1094 Address rewriting that is specified in the rewrite section of the configuration
1095 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1096 both in the header lines and the envelope, at the time the message is accepted.
1097 If during the course of delivery additional addresses are generated (for
1098 example, via aliasing), these new addresses are rewritten as soon as they are
1099 generated. At the time a message is actually delivered (transported) further
1100 rewriting can take place; because this is a transport option, it can be
1101 different for different forms of delivery. It is also possible to specify the
1102 addition or removal of certain header lines at the time the message is
1103 delivered (see chapters &<<CHAProutergeneric>>& and
1104 &<<CHAPtransportgeneric>>&).
1105
1106
1107
1108 .section "Life of a message" "SECID15"
1109 .cindex "message" "life of"
1110 .cindex "message" "frozen"
1111 A message remains in the spool directory until it is completely delivered to
1112 its recipients or to an error address, or until it is deleted by an
1113 administrator or by the user who originally created it. In cases when delivery
1114 cannot proceed &-- for example, when a message can neither be delivered to its
1115 recipients nor returned to its sender, the message is marked &"frozen"& on the
1116 spool, and no more deliveries are attempted.
1117
1118 .cindex "frozen messages" "thawing"
1119 .cindex "message" "thawing frozen"
1120 An administrator can &"thaw"& such messages when the problem has been
1121 corrected, and can also freeze individual messages by hand if necessary. In
1122 addition, an administrator can force a delivery error, causing a bounce message
1123 to be sent.
1124
1125 .oindex "&%timeout_frozen_after%&"
1126 .oindex "&%ignore_bounce_errors_after%&"
1127 There are options called &%ignore_bounce_errors_after%& and
1128 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1129 The first applies only to frozen bounces, the second to any frozen messages.
1130
1131 .cindex "message" "log file for"
1132 .cindex "log" "file for each message"
1133 While Exim is working on a message, it writes information about each delivery
1134 attempt to its main log file. This includes successful, unsuccessful, and
1135 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1136 lines are also written to a separate &'message log'& file for each message.
1137 These logs are solely for the benefit of the administrator, and are normally
1138 deleted along with the spool files when processing of a message is complete.
1139 The use of individual message logs can be disabled by setting
1140 &%no_message_logs%&; this might give an improvement in performance on very busy
1141 systems.
1142
1143 .cindex "journal file"
1144 .cindex "file" "journal"
1145 All the information Exim itself needs to set up a delivery is kept in the first
1146 spool file, along with the header lines. When a successful delivery occurs, the
1147 address is immediately written at the end of a journal file, whose name is the
1148 message id followed by &`-J`&. At the end of a delivery run, if there are some
1149 addresses left to be tried again later, the first spool file (the &`-H`& file)
1150 is updated to indicate which these are, and the journal file is then deleted.
1151 Updating the spool file is done by writing a new file and renaming it, to
1152 minimize the possibility of data loss.
1153
1154 Should the system or the program crash after a successful delivery but before
1155 the spool file has been updated, the journal is left lying around. The next
1156 time Exim attempts to deliver the message, it reads the journal file and
1157 updates the spool file before proceeding. This minimizes the chances of double
1158 deliveries caused by crashes.
1159
1160
1161
1162 .section "Processing an address for delivery" "SECTprocaddress"
1163 .cindex "drivers" "definition of"
1164 .cindex "router" "definition of"
1165 .cindex "transport" "definition of"
1166 The main delivery processing elements of Exim are called &'routers'& and
1167 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1168 number of them is provided in the source distribution, and compile-time options
1169 specify which ones are included in the binary. Run time options specify which
1170 ones are actually used for delivering messages.
1171
1172 .cindex "drivers" "instance definition"
1173 Each driver that is specified in the run time configuration is an &'instance'&
1174 of that particular driver type. Multiple instances are allowed; for example,
1175 you can set up several different &(smtp)& transports, each with different
1176 option values that might specify different ports or different timeouts. Each
1177 instance has its own identifying name. In what follows we will normally use the
1178 instance name when discussing one particular instance (that is, one specific
1179 configuration of the driver), and the generic driver name when discussing
1180 the driver's features in general.
1181
1182 A &'router'& is a driver that operates on an address, either determining how
1183 its delivery should happen, by assigning it to a specific transport, or
1184 converting the address into one or more new addresses (for example, via an
1185 alias file). A router may also explicitly choose to fail an address, causing it
1186 to be bounced.
1187
1188 A &'transport'& is a driver that transmits a copy of the message from Exim's
1189 spool to some destination. There are two kinds of transport: for a &'local'&
1190 transport, the destination is a file or a pipe on the local host, whereas for a
1191 &'remote'& transport the destination is some other host. A message is passed
1192 to a specific transport as a result of successful routing. If a message has
1193 several recipients, it may be passed to a number of different transports.
1194
1195 .cindex "preconditions" "definition of"
1196 An address is processed by passing it to each configured router instance in
1197 turn, subject to certain preconditions, until a router accepts the address or
1198 specifies that it should be bounced. We will describe this process in more
1199 detail shortly. First, as a simple example, we consider how each recipient
1200 address in a message is processed in a small configuration of three routers.
1201
1202 To make this a more concrete example, it is described in terms of some actual
1203 routers, but remember, this is only an example. You can configure Exim's
1204 routers in many different ways, and there may be any number of routers in a
1205 configuration.
1206
1207 The first router that is specified in a configuration is often one that handles
1208 addresses in domains that are not recognized specially by the local host. These
1209 are typically addresses for arbitrary domains on the Internet. A precondition
1210 is set up which looks for the special domains known to the host (for example,
1211 its own domain name), and the router is run for addresses that do &'not'&
1212 match. Typically, this is a router that looks up domains in the DNS in order to
1213 find the hosts to which this address routes. If it succeeds, the address is
1214 assigned to a suitable SMTP transport; if it does not succeed, the router is
1215 configured to fail the address.
1216
1217 The second router is reached only when the domain is recognized as one that
1218 &"belongs"& to the local host. This router does redirection &-- also known as
1219 aliasing and forwarding. When it generates one or more new addresses from the
1220 original, each of them is routed independently from the start. Otherwise, the
1221 router may cause an address to fail, or it may simply decline to handle the
1222 address, in which case the address is passed to the next router.
1223
1224 The final router in many configurations is one that checks to see if the
1225 address belongs to a local mailbox. The precondition may involve a check to
1226 see if the local part is the name of a login account, or it may look up the
1227 local part in a file or a database. If its preconditions are not met, or if
1228 the router declines, we have reached the end of the routers. When this happens,
1229 the address is bounced.
1230
1231
1232
1233 .section "Processing an address for verification" "SECID16"
1234 .cindex "router" "for verification"
1235 .cindex "verifying address" "overview"
1236 As well as being used to decide how to deliver to an address, Exim's routers
1237 are also used for &'address verification'&. Verification can be requested as
1238 one of the checks to be performed in an ACL for incoming messages, on both
1239 sender and recipient addresses, and it can be tested using the &%-bv%& and
1240 &%-bvs%& command line options.
1241
1242 When an address is being verified, the routers are run in &"verify mode"&. This
1243 does not affect the way the routers work, but it is a state that can be
1244 detected. By this means, a router can be skipped or made to behave differently
1245 when verifying. A common example is a configuration in which the first router
1246 sends all messages to a message-scanning program, unless they have been
1247 previously scanned. Thus, the first router accepts all addresses without any
1248 checking, making it useless for verifying. Normally, the &%no_verify%& option
1249 would be set for such a router, causing it to be skipped in verify mode.
1250
1251
1252
1253
1254 .section "Running an individual router" "SECTrunindrou"
1255 .cindex "router" "running details"
1256 .cindex "preconditions" "checking"
1257 .cindex "router" "result of running"
1258 As explained in the example above, a number of preconditions are checked before
1259 running a router. If any are not met, the router is skipped, and the address is
1260 passed to the next router. When all the preconditions on a router &'are'& met,
1261 the router is run. What happens next depends on the outcome, which is one of
1262 the following:
1263
1264 .ilist
1265 &'accept'&: The router accepts the address, and either assigns it to a
1266 transport, or generates one or more &"child"& addresses. Processing the
1267 original address ceases,
1268 .oindex "&%unseen%&"
1269 unless the &%unseen%& option is set on the router. This option
1270 can be used to set up multiple deliveries with different routing (for example,
1271 for keeping archive copies of messages). When &%unseen%& is set, the address is
1272 passed to the next router. Normally, however, an &'accept'& return marks the
1273 end of routing.
1274
1275 Any child addresses generated by the router are processed independently,
1276 starting with the first router by default. It is possible to change this by
1277 setting the &%redirect_router%& option to specify which router to start at for
1278 child addresses. Unlike &%pass_router%& (see below) the router specified by
1279 &%redirect_router%& may be anywhere in the router configuration.
1280 .next
1281 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1282 requests that the address be passed to another router. By default the address
1283 is passed to the next router, but this can be changed by setting the
1284 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1285 must be below the current router (to avoid loops).
1286 .next
1287 &'decline'&: The router declines to accept the address because it does not
1288 recognize it at all. By default, the address is passed to the next router, but
1289 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1290 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1291 &'decline'& into &'fail'&.
1292 .next
1293 &'fail'&: The router determines that the address should fail, and queues it for
1294 the generation of a bounce message. There is no further processing of the
1295 original address unless &%unseen%& is set on the router.
1296 .next
1297 &'defer'&: The router cannot handle the address at the present time. (A
1298 database may be offline, or a DNS lookup may have timed out.) No further
1299 processing of the address happens in this delivery attempt. It is tried again
1300 next time the message is considered for delivery.
1301 .next
1302 &'error'&: There is some error in the router (for example, a syntax error in
1303 its configuration). The action is as for defer.
1304 .endlist
1305
1306 If an address reaches the end of the routers without having been accepted by
1307 any of them, it is bounced as unrouteable. The default error message in this
1308 situation is &"unrouteable address"&, but you can set your own message by
1309 making use of the &%cannot_route_message%& option. This can be set for any
1310 router; the value from the last router that &"saw"& the address is used.
1311
1312 Sometimes while routing you want to fail a delivery when some conditions are
1313 met but others are not, instead of passing the address on for further routing.
1314 You can do this by having a second router that explicitly fails the delivery
1315 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1316 facility for this purpose.
1317
1318
1319 .section "Duplicate addresses" "SECID17"
1320 .cindex "case of local parts"
1321 .cindex "address duplicate, discarding"
1322 .cindex "duplicate addresses"
1323 Once routing is complete, Exim scans the addresses that are assigned to local
1324 and remote transports, and discards any duplicates that it finds. During this
1325 check, local parts are treated as case-sensitive. This happens only when
1326 actually delivering a message; when testing routers with &%-bt%&, all the
1327 routed addresses are shown.
1328
1329
1330
1331 .section "Router preconditions" "SECTrouprecon"
1332 .cindex "router" "preconditions, order of processing"
1333 .cindex "preconditions" "order of processing"
1334 The preconditions that are tested for each router are listed below, in the
1335 order in which they are tested. The individual configuration options are
1336 described in more detail in chapter &<<CHAProutergeneric>>&.
1337
1338 .ilist
1339 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1340 the local parts handled by the router may or must have certain prefixes and/or
1341 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1342 skipped. These conditions are tested first. When an affix is present, it is
1343 removed from the local part before further processing, including the evaluation
1344 of any other conditions.
1345 .next
1346 Routers can be designated for use only when not verifying an address, that is,
1347 only when routing it for delivery (or testing its delivery routing). If the
1348 &%verify%& option is set false, the router is skipped when Exim is verifying an
1349 address.
1350 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1351 &%verify_recipient%&, which independently control the use of the router for
1352 sender and recipient verification. You can set these options directly if
1353 you want a router to be used for only one type of verification.
1354 .next
1355 If the &%address_test%& option is set false, the router is skipped when Exim is
1356 run with the &%-bt%& option to test an address routing. This can be helpful
1357 when the first router sends all new messages to a scanner of some sort; it
1358 makes it possible to use &%-bt%& to test subsequent delivery routing without
1359 having to simulate the effect of the scanner.
1360 .next
1361 Routers can be designated for use only when verifying an address, as
1362 opposed to routing it for delivery. The &%verify_only%& option controls this.
1363 .next
1364 Individual routers can be explicitly skipped when running the routers to
1365 check an address given in the SMTP EXPN command (see the &%expn%& option).
1366 .next
1367 If the &%domains%& option is set, the domain of the address must be in the set
1368 of domains that it defines.
1369 .next
1370 .vindex "&$local_part_prefix$&"
1371 .vindex "&$local_part$&"
1372 .vindex "&$local_part_suffix$&"
1373 If the &%local_parts%& option is set, the local part of the address must be in
1374 the set of local parts that it defines. If &%local_part_prefix%& or
1375 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1376 part before this check. If you want to do precondition tests on local parts
1377 that include affixes, you can do so by using a &%condition%& option (see below)
1378 that uses the variables &$local_part$&, &$local_part_prefix$&, and
1379 &$local_part_suffix$& as necessary.
1380 .next
1381 .vindex "&$local_user_uid$&"
1382 .vindex "&$local_user_gid$&"
1383 .vindex "&$home$&"
1384 If the &%check_local_user%& option is set, the local part must be the name of
1385 an account on the local host. If this check succeeds, the uid and gid of the
1386 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1387 user's home directory is placed in &$home$&; these values can be used in the
1388 remaining preconditions.
1389 .next
1390 If the &%router_home_directory%& option is set, it is expanded at this point,
1391 because it overrides the value of &$home$&. If this expansion were left till
1392 later, the value of &$home$& as set by &%check_local_user%& would be used in
1393 subsequent tests. Having two different values of &$home$& in the same router
1394 could lead to confusion.
1395 .next
1396 If the &%senders%& option is set, the envelope sender address must be in the
1397 set of addresses that it defines.
1398 .next
1399 If the &%require_files%& option is set, the existence or non-existence of
1400 specified files is tested.
1401 .next
1402 .cindex "customizing" "precondition"
1403 If the &%condition%& option is set, it is evaluated and tested. This option
1404 uses an expanded string to allow you to set up your own custom preconditions.
1405 Expanded strings are described in chapter &<<CHAPexpand>>&.
1406 .endlist
1407
1408
1409 Note that &%require_files%& comes near the end of the list, so you cannot use
1410 it to check for the existence of a file in which to lookup up a domain, local
1411 part, or sender. However, as these options are all expanded, you can use the
1412 &%exists%& expansion condition to make such tests within each condition. The
1413 &%require_files%& option is intended for checking files that the router may be
1414 going to use internally, or which are needed by a specific transport (for
1415 example, &_.procmailrc_&).
1416
1417
1418
1419 .section "Delivery in detail" "SECID18"
1420 .cindex "delivery" "in detail"
1421 When a message is to be delivered, the sequence of events is as follows:
1422
1423 .ilist
1424 If a system-wide filter file is specified, the message is passed to it. The
1425 filter may add recipients to the message, replace the recipients, discard the
1426 message, cause a new message to be generated, or cause the message delivery to
1427 fail. The format of the system filter file is the same as for Exim user filter
1428 files, described in the separate document entitled &'Exim's interfaces to mail
1429 filtering'&.
1430 .cindex "Sieve filter" "not available for system filter"
1431 (&*Note*&: Sieve cannot be used for system filter files.)
1432
1433 Some additional features are available in system filters &-- see chapter
1434 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1435 filter only once per delivery attempt, however many recipients it has. However,
1436 if there are several delivery attempts because one or more addresses could not
1437 be immediately delivered, the system filter is run each time. The filter
1438 condition &%first_delivery%& can be used to detect the first run of the system
1439 filter.
1440 .next
1441 Each recipient address is offered to each configured router in turn, subject to
1442 its preconditions, until one is able to handle it. If no router can handle the
1443 address, that is, if they all decline, the address is failed. Because routers
1444 can be targeted at particular domains, several locally handled domains can be
1445 processed entirely independently of each other.
1446 .next
1447 .cindex "routing" "loops in"
1448 .cindex "loop" "while routing"
1449 A router that accepts an address may assign it to a local or a remote
1450 transport. However, the transport is not run at this time. Instead, the address
1451 is placed on a list for the particular transport, which will be run later.
1452 Alternatively, the router may generate one or more new addresses (typically
1453 from alias, forward, or filter files). New addresses are fed back into this
1454 process from the top, but in order to avoid loops, a router ignores any address
1455 which has an identically-named ancestor that was processed by itself.
1456 .next
1457 When all the routing has been done, addresses that have been successfully
1458 handled are passed to their assigned transports. When local transports are
1459 doing real local deliveries, they handle only one address at a time, but if a
1460 local transport is being used as a pseudo-remote transport (for example, to
1461 collect batched SMTP messages for transmission by some other means) multiple
1462 addresses can be handled. Remote transports can always handle more than one
1463 address at a time, but can be configured not to do so, or to restrict multiple
1464 addresses to the same domain.
1465 .next
1466 Each local delivery to a file or a pipe runs in a separate process under a
1467 non-privileged uid, and these deliveries are run one at a time. Remote
1468 deliveries also run in separate processes, normally under a uid that is private
1469 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1470 run in parallel. The maximum number of simultaneous remote deliveries for any
1471 one message is set by the &%remote_max_parallel%& option.
1472 The order in which deliveries are done is not defined, except that all local
1473 deliveries happen before any remote deliveries.
1474 .next
1475 .cindex "queue runner"
1476 When it encounters a local delivery during a queue run, Exim checks its retry
1477 database to see if there has been a previous temporary delivery failure for the
1478 address before running the local transport. If there was a previous failure,
1479 Exim does not attempt a new delivery until the retry time for the address is
1480 reached. However, this happens only for delivery attempts that are part of a
1481 queue run. Local deliveries are always attempted when delivery immediately
1482 follows message reception, even if retry times are set for them. This makes for
1483 better behaviour if one particular message is causing problems (for example,
1484 causing quota overflow, or provoking an error in a filter file).
1485 .next
1486 .cindex "delivery" "retry in remote transports"
1487 Remote transports do their own retry handling, since an address may be
1488 deliverable to one of a number of hosts, each of which may have a different
1489 retry time. If there have been previous temporary failures and no host has
1490 reached its retry time, no delivery is attempted, whether in a queue run or
1491 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1492 .next
1493 If there were any permanent errors, a bounce message is returned to an
1494 appropriate address (the sender in the common case), with details of the error
1495 for each failing address. Exim can be configured to send copies of bounce
1496 messages to other addresses.
1497 .next
1498 .cindex "delivery" "deferral"
1499 If one or more addresses suffered a temporary failure, the message is left on
1500 the queue, to be tried again later. Delivery of these addresses is said to be
1501 &'deferred'&.
1502 .next
1503 When all the recipient addresses have either been delivered or bounced,
1504 handling of the message is complete. The spool files and message log are
1505 deleted, though the message log can optionally be preserved if required.
1506 .endlist
1507
1508
1509
1510
1511 .section "Retry mechanism" "SECID19"
1512 .cindex "delivery" "retry mechanism"
1513 .cindex "retry" "description of mechanism"
1514 .cindex "queue runner"
1515 Exim's mechanism for retrying messages that fail to get delivered at the first
1516 attempt is the queue runner process. You must either run an Exim daemon that
1517 uses the &%-q%& option with a time interval to start queue runners at regular
1518 intervals, or use some other means (such as &'cron'&) to start them. If you do
1519 not arrange for queue runners to be run, messages that fail temporarily at the
1520 first attempt will remain on your queue for ever. A queue runner process works
1521 its way through the queue, one message at a time, trying each delivery that has
1522 passed its retry time.
1523 You can run several queue runners at once.
1524
1525 Exim uses a set of configured rules to determine when next to retry the failing
1526 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1527 should give up trying to deliver to the address, at which point it generates a
1528 bounce message. If no retry rules are set for a particular host, address, and
1529 error combination, no retries are attempted, and temporary errors are treated
1530 as permanent.
1531
1532
1533
1534 .section "Temporary delivery failure" "SECID20"
1535 .cindex "delivery" "temporary failure"
1536 There are many reasons why a message may not be immediately deliverable to a
1537 particular address. Failure to connect to a remote machine (because it, or the
1538 connection to it, is down) is one of the most common. Temporary failures may be
1539 detected during routing as well as during the transport stage of delivery.
1540 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1541 is on a file system where the user is over quota. Exim can be configured to
1542 impose its own quotas on local mailboxes; where system quotas are set they will
1543 also apply.
1544
1545 If a host is unreachable for a period of time, a number of messages may be
1546 waiting for it by the time it recovers, and sending them in a single SMTP
1547 connection is clearly beneficial. Whenever a delivery to a remote host is
1548 deferred,
1549
1550 .cindex "hints database"
1551 Exim makes a note in its hints database, and whenever a successful
1552 SMTP delivery has happened, it looks to see if any other messages are waiting
1553 for the same host. If any are found, they are sent over the same SMTP
1554 connection, subject to a configuration limit as to the maximum number in any
1555 one connection.
1556
1557
1558
1559
1560 .section "Permanent delivery failure" "SECID21"
1561 .cindex "delivery" "permanent failure"
1562 .cindex "bounce message" "when generated"
1563 When a message cannot be delivered to some or all of its intended recipients, a
1564 bounce message is generated. Temporary delivery failures turn into permanent
1565 errors when their timeout expires. All the addresses that fail in a given
1566 delivery attempt are listed in a single message. If the original message has
1567 many recipients, it is possible for some addresses to fail in one delivery
1568 attempt and others to fail subsequently, giving rise to more than one bounce
1569 message. The wording of bounce messages can be customized by the administrator.
1570 See chapter &<<CHAPemsgcust>>& for details.
1571
1572 .cindex "&'X-Failed-Recipients:'& header line"
1573 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1574 failed addresses, for the benefit of programs that try to analyse such messages
1575 automatically.
1576
1577 .cindex "bounce message" "recipient of"
1578 A bounce message is normally sent to the sender of the original message, as
1579 obtained from the message's envelope. For incoming SMTP messages, this is the
1580 address given in the MAIL command. However, when an address is expanded via a
1581 forward or alias file, an alternative address can be specified for delivery
1582 failures of the generated addresses. For a mailing list expansion (see section
1583 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1584 of the list.
1585
1586
1587
1588 .section "Failures to deliver bounce messages" "SECID22"
1589 .cindex "bounce message" "failure to deliver"
1590 If a bounce message (either locally generated or received from a remote host)
1591 itself suffers a permanent delivery failure, the message is left on the queue,
1592 but it is frozen, awaiting the attention of an administrator. There are options
1593 that can be used to make Exim discard such failed messages, or to keep them
1594 for only a short time (see &%timeout_frozen_after%& and
1595 &%ignore_bounce_errors_after%&).
1596
1597
1598
1599
1600
1601 . ////////////////////////////////////////////////////////////////////////////
1602 . ////////////////////////////////////////////////////////////////////////////
1603
1604 .chapter "Building and installing Exim" "CHID3"
1605 .scindex IIDbuex "building Exim"
1606
1607 .section "Unpacking" "SECID23"
1608 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1609 creates a directory with the name of the current release (for example,
1610 &_exim-&version;_&) into which the following files are placed:
1611
1612 .table2 140pt
1613 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1614 .irow &_CHANGES_& "contains a reference to where changes are &&&
1615 documented"
1616 .irow &_LICENCE_& "the GNU General Public Licence"
1617 .irow &_Makefile_& "top-level make file"
1618 .irow &_NOTICE_& "conditions for the use of Exim"
1619 .irow &_README_& "list of files, directories and simple build &&&
1620 instructions"
1621 .endtable
1622
1623 Other files whose names begin with &_README_& may also be present. The
1624 following subdirectories are created:
1625
1626 .table2 140pt
1627 .irow &_Local_& "an empty directory for local configuration files"
1628 .irow &_OS_& "OS-specific files"
1629 .irow &_doc_& "documentation files"
1630 .irow &_exim_monitor_& "source files for the Exim monitor"
1631 .irow &_scripts_& "scripts used in the build process"
1632 .irow &_src_& "remaining source files"
1633 .irow &_util_& "independent utilities"
1634 .endtable
1635
1636 The main utility programs are contained in the &_src_& directory, and are built
1637 with the Exim binary. The &_util_& directory contains a few optional scripts
1638 that may be useful to some sites.
1639
1640
1641 .section "Multiple machine architectures and operating systems" "SECID24"
1642 .cindex "building Exim" "multiple OS/architectures"
1643 The building process for Exim is arranged to make it easy to build binaries for
1644 a number of different architectures and operating systems from the same set of
1645 source files. Compilation does not take place in the &_src_& directory.
1646 Instead, a &'build directory'& is created for each architecture and operating
1647 system.
1648 .cindex "symbolic link" "to build directory"
1649 Symbolic links to the sources are installed in this directory, which is where
1650 the actual building takes place. In most cases, Exim can discover the machine
1651 architecture and operating system for itself, but the defaults can be
1652 overridden if necessary.
1653
1654
1655 .section "PCRE library" "SECTpcre"
1656 .cindex "PCRE library"
1657 Exim no longer has an embedded PCRE library as the vast majority of
1658 modern systems include PCRE as a system library, although you may need
1659 to install the PCRE or PCRE development package for your operating
1660 system. If your system has a normal PCRE installation the Exim build
1661 process will need no further configuration. If the library or the
1662 headers are in an unusual location you will need to set the PCRE_LIBS
1663 and INCLUDE directives appropriately. If your operating system has no
1664 PCRE support then you will need to obtain and build the current PCRE
1665 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
1666
1667 .section "DBM libraries" "SECTdb"
1668 .cindex "DBM libraries" "discussion of"
1669 .cindex "hints database" "DBM files used for"
1670 Even if you do not use any DBM files in your configuration, Exim still needs a
1671 DBM library in order to operate, because it uses indexed files for its hints
1672 databases. Unfortunately, there are a number of DBM libraries in existence, and
1673 different operating systems often have different ones installed.
1674
1675 .cindex "Solaris" "DBM library for"
1676 .cindex "IRIX, DBM library for"
1677 .cindex "BSD, DBM library for"
1678 .cindex "Linux, DBM library for"
1679 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1680 Linux distribution, the DBM configuration should happen automatically, and you
1681 may be able to ignore this section. Otherwise, you may have to learn more than
1682 you would like about DBM libraries from what follows.
1683
1684 .cindex "&'ndbm'& DBM library"
1685 Licensed versions of Unix normally contain a library of DBM functions operating
1686 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1687 versions of Unix seem to vary in what they contain as standard. In particular,
1688 some early versions of Linux have no default DBM library, and different
1689 distributors have chosen to bundle different libraries with their packaged
1690 versions. However, the more recent releases seem to have standardized on the
1691 Berkeley DB library.
1692
1693 Different DBM libraries have different conventions for naming the files they
1694 use. When a program opens a file called &_dbmfile_&, there are several
1695 possibilities:
1696
1697 .olist
1698 A traditional &'ndbm'& implementation, such as that supplied as part of
1699 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1700 .next
1701 .cindex "&'gdbm'& DBM library"
1702 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1703 compatibility interface it makes two different hard links to it with names
1704 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1705 file name is used unmodified.
1706 .next
1707 .cindex "Berkeley DB library"
1708 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1709 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1710 programmer exactly the same as the traditional &'ndbm'& implementation.
1711 .next
1712 If the Berkeley package is used in its native mode, it operates on a single
1713 file called &_dbmfile_&; the programmer's interface is somewhat different to
1714 the traditional &'ndbm'& interface.
1715 .next
1716 To complicate things further, there are several very different versions of the
1717 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1718 2.&'x'& and 3.&'x'& were current for a while, but the latest versions are now
1719 numbered 4.&'x'&. Maintenance of some of the earlier releases has ceased. All
1720 versions of Berkeley DB can be obtained from
1721 &url(http://www.sleepycat.com/).
1722 .next
1723 .cindex "&'tdb'& DBM library"
1724 Yet another DBM library, called &'tdb'&, is available from
1725 &url(http://download.sourceforge.net/tdb). It has its own interface, and also
1726 operates on a single file.
1727 .endlist
1728
1729 .cindex "USE_DB"
1730 .cindex "DBM libraries" "configuration for building"
1731 Exim and its utilities can be compiled to use any of these interfaces. In order
1732 to use any version of the Berkeley DB package in native mode, you must set
1733 USE_DB in an appropriate configuration file (typically
1734 &_Local/Makefile_&). For example:
1735 .code
1736 USE_DB=yes
1737 .endd
1738 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1739 error is diagnosed if you set more than one of these.
1740
1741 At the lowest level, the build-time configuration sets none of these options,
1742 thereby assuming an interface of type (1). However, some operating system
1743 configuration files (for example, those for the BSD operating systems and
1744 Linux) assume type (4) by setting USE_DB as their default, and the
1745 configuration files for Cygwin set USE_GDBM. Anything you set in
1746 &_Local/Makefile_&, however, overrides these system defaults.
1747
1748 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1749 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1750 in one of these lines:
1751 .code
1752 DBMLIB = -ldb
1753 DBMLIB = -ltdb
1754 .endd
1755 Settings like that will work if the DBM library is installed in the standard
1756 place. Sometimes it is not, and the library's header file may also not be in
1757 the default path. You may need to set INCLUDE to specify where the header
1758 file is, and to specify the path to the library more fully in DBMLIB, as in
1759 this example:
1760 .code
1761 INCLUDE=-I/usr/local/include/db-4.1
1762 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1763 .endd
1764 There is further detailed discussion about the various DBM libraries in the
1765 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1766
1767
1768
1769 .section "Pre-building configuration" "SECID25"
1770 .cindex "building Exim" "pre-building configuration"
1771 .cindex "configuration for building Exim"
1772 .cindex "&_Local/Makefile_&"
1773 .cindex "&_src/EDITME_&"
1774 Before building Exim, a local configuration file that specifies options
1775 independent of any operating system has to be created with the name
1776 &_Local/Makefile_&. A template for this file is supplied as the file
1777 &_src/EDITME_&, and it contains full descriptions of all the option settings
1778 therein. These descriptions are therefore not repeated here. If you are
1779 building Exim for the first time, the simplest thing to do is to copy
1780 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1781
1782 There are three settings that you must supply, because Exim will not build
1783 without them. They are the location of the run time configuration file
1784 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1785 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1786 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1787 a colon-separated list of file names; Exim uses the first of them that exists.
1788
1789 There are a few other parameters that can be specified either at build time or
1790 at run time, to enable the same binary to be used on a number of different
1791 machines. However, if the locations of Exim's spool directory and log file
1792 directory (if not within the spool directory) are fixed, it is recommended that
1793 you specify them in &_Local/Makefile_& instead of at run time, so that errors
1794 detected early in Exim's execution (such as a malformed configuration file) can
1795 be logged.
1796
1797 .cindex "content scanning" "specifying at build time"
1798 Exim's interfaces for calling virus and spam scanning software directly from
1799 access control lists are not compiled by default. If you want to include these
1800 facilities, you need to set
1801 .code
1802 WITH_CONTENT_SCAN=yes
1803 .endd
1804 in your &_Local/Makefile_&. For details of the facilities themselves, see
1805 chapter &<<CHAPexiscan>>&.
1806
1807
1808 .cindex "&_Local/eximon.conf_&"
1809 .cindex "&_exim_monitor/EDITME_&"
1810 If you are going to build the Exim monitor, a similar configuration process is
1811 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1812 your installation and saved under the name &_Local/eximon.conf_&. If you are
1813 happy with the default settings described in &_exim_monitor/EDITME_&,
1814 &_Local/eximon.conf_& can be empty, but it must exist.
1815
1816 This is all the configuration that is needed in straightforward cases for known
1817 operating systems. However, the building process is set up so that it is easy
1818 to override options that are set by default or by operating-system-specific
1819 configuration files, for example to change the name of the C compiler, which
1820 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1821 do this.
1822
1823
1824
1825 .section "Support for iconv()" "SECID26"
1826 .cindex "&[iconv()]& support"
1827 .cindex "RFC 2047"
1828 The contents of header lines in messages may be encoded according to the rules
1829 described RFC 2047. This makes it possible to transmit characters that are not
1830 in the ASCII character set, and to label them as being in a particular
1831 character set. When Exim is inspecting header lines by means of the &%$h_%&
1832 mechanism, it decodes them, and translates them into a specified character set
1833 (default ISO-8859-1). The translation is possible only if the operating system
1834 supports the &[iconv()]& function.
1835
1836 However, some of the operating systems that supply &[iconv()]& do not support
1837 very many conversions. The GNU &%libiconv%& library (available from
1838 &url(http://www.gnu.org/software/libiconv/)) can be installed on such
1839 systems to remedy this deficiency, as well as on systems that do not supply
1840 &[iconv()]& at all. After installing &%libiconv%&, you should add
1841 .code
1842 HAVE_ICONV=yes
1843 .endd
1844 to your &_Local/Makefile_& and rebuild Exim.
1845
1846
1847
1848 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1849 .cindex "TLS" "including support for TLS"
1850 .cindex "encryption" "including support for"
1851 .cindex "SUPPORT_TLS"
1852 .cindex "OpenSSL" "building Exim with"
1853 .cindex "GnuTLS" "building Exim with"
1854 Exim can be built to support encrypted SMTP connections, using the STARTTLS
1855 command as per RFC 2487. It can also support legacy clients that expect to
1856 start a TLS session immediately on connection to a non-standard port (see the
1857 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1858 line option).
1859
1860 If you want to build Exim with TLS support, you must first install either the
1861 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1862 implementing SSL.
1863
1864 If OpenSSL is installed, you should set
1865 .code
1866 SUPPORT_TLS=yes
1867 TLS_LIBS=-lssl -lcrypto
1868 .endd
1869 in &_Local/Makefile_&. You may also need to specify the locations of the
1870 OpenSSL library and include files. For example:
1871 .code
1872 SUPPORT_TLS=yes
1873 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1874 TLS_INCLUDE=-I/usr/local/openssl/include/
1875 .endd
1876 .cindex "USE_GNUTLS"
1877 If GnuTLS is installed, you should set
1878 .code
1879 SUPPORT_TLS=yes
1880 USE_GNUTLS=yes
1881 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1882 .endd
1883 in &_Local/Makefile_&, and again you may need to specify the locations of the
1884 library and include files. For example:
1885 .code
1886 SUPPORT_TLS=yes
1887 USE_GNUTLS=yes
1888 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1889 TLS_INCLUDE=-I/usr/gnu/include
1890 .endd
1891 You do not need to set TLS_INCLUDE if the relevant directory is already
1892 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1893 given in chapter &<<CHAPTLS>>&.
1894
1895
1896
1897
1898 .section "Use of tcpwrappers" "SECID27"
1899 .cindex "tcpwrappers, building Exim to support"
1900 .cindex "USE_TCP_WRAPPERS"
1901 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
1902 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
1903 alternative to Exim's own checking facilities for installations that are
1904 already making use of &'tcpwrappers'& for other purposes. To do this, you
1905 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
1906 &_tcpd.h_& to be available at compile time, and also ensure that the library
1907 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
1908 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
1909 you might have
1910 .code
1911 USE_TCP_WRAPPERS=yes
1912 CFLAGS=-O -I/usr/local/include
1913 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
1914 .endd
1915 in &_Local/Makefile_&. The name to use in the &'tcpwrappers'& control files is
1916 &"exim"&. For example, the line
1917 .code
1918 exim : LOCAL 192.168.1. .friendly.domain.example
1919 .endd
1920 in your &_/etc/hosts.allow_& file allows connections from the local host, from
1921 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
1922 All other connections are denied. Consult the &'tcpwrappers'& documentation for
1923 further details.
1924
1925
1926
1927 .section "Including support for IPv6" "SECID28"
1928 .cindex "IPv6" "including support for"
1929 Exim contains code for use on systems that have IPv6 support. Setting
1930 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
1931 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
1932 where the IPv6 support is not fully integrated into the normal include and
1933 library files.
1934
1935 Two different types of DNS record for handling IPv6 addresses have been
1936 defined. AAAA records (analogous to A records for IPv4) are in use, and are
1937 currently seen as the mainstream. Another record type called A6 was proposed
1938 as better than AAAA because it had more flexibility. However, it was felt to be
1939 over-complex, and its status was reduced to &"experimental"&. It is not known
1940 if anyone is actually using A6 records. Exim has support for A6 records, but
1941 this is included only if you set &`SUPPORT_A6=YES`& in &_Local/Makefile_&. The
1942 support has not been tested for some time.
1943
1944
1945
1946 .section "The building process" "SECID29"
1947 .cindex "build directory"
1948 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
1949 created, run &'make'& at the top level. It determines the architecture and
1950 operating system types, and creates a build directory if one does not exist.
1951 For example, on a Sun system running Solaris 8, the directory
1952 &_build-SunOS5-5.8-sparc_& is created.
1953 .cindex "symbolic link" "to source files"
1954 Symbolic links to relevant source files are installed in the build directory.
1955
1956 &*Warning*&: The &%-j%& (parallel) flag must not be used with &'make'&; the
1957 building process fails if it is set.
1958
1959 If this is the first time &'make'& has been run, it calls a script that builds
1960 a make file inside the build directory, using the configuration files from the
1961 &_Local_& directory. The new make file is then passed to another instance of
1962 &'make'&. This does the real work, building a number of utility scripts, and
1963 then compiling and linking the binaries for the Exim monitor (if configured), a
1964 number of utility programs, and finally Exim itself. The command &`make
1965 makefile`& can be used to force a rebuild of the make file in the build
1966 directory, should this ever be necessary.
1967
1968 If you have problems building Exim, check for any comments there may be in the
1969 &_README_& file concerning your operating system, and also take a look at the
1970 FAQ, where some common problems are covered.
1971
1972
1973
1974 .section 'Output from &"make"&' "SECID283"
1975 The output produced by the &'make'& process for compile lines is often very
1976 unreadable, because these lines can be very long. For this reason, the normal
1977 output is suppressed by default, and instead output similar to that which
1978 appears when compiling the 2.6 Linux kernel is generated: just a short line for
1979 each module that is being compiled or linked. However, it is still possible to
1980 get the full output, by calling &'make'& like this:
1981 .code
1982 FULLECHO='' make -e
1983 .endd
1984 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
1985 command reflection in &'make'&. When you ask for the full output, it is
1986 given in addition to the short output.
1987
1988
1989
1990 .section "Overriding build-time options for Exim" "SECToverride"
1991 .cindex "build-time options, overriding"
1992 The main make file that is created at the beginning of the building process
1993 consists of the concatenation of a number of files which set configuration
1994 values, followed by a fixed set of &'make'& instructions. If a value is set
1995 more than once, the last setting overrides any previous ones. This provides a
1996 convenient way of overriding defaults. The files that are concatenated are, in
1997 order:
1998 .display
1999 &_OS/Makefile-Default_&
2000 &_OS/Makefile-_&<&'ostype'&>
2001 &_Local/Makefile_&
2002 &_Local/Makefile-_&<&'ostype'&>
2003 &_Local/Makefile-_&<&'archtype'&>
2004 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2005 &_OS/Makefile-Base_&
2006 .endd
2007 .cindex "&_Local/Makefile_&"
2008 .cindex "building Exim" "operating system type"
2009 .cindex "building Exim" "architecture type"
2010 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2011 architecture type. &_Local/Makefile_& is required to exist, and the building
2012 process fails if it is absent. The other three &_Local_& files are optional,
2013 and are often not needed.
2014
2015 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2016 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2017 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2018 values are used, thereby providing a means of forcing particular settings.
2019 Otherwise, the scripts try to get values from the &%uname%& command. If this
2020 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2021 of &'ad hoc'& transformations are then applied, to produce the standard names
2022 that Exim expects. You can run these scripts directly from the shell in order
2023 to find out what values are being used on your system.
2024
2025
2026 &_OS/Makefile-Default_& contains comments about the variables that are set
2027 therein. Some (but not all) are mentioned below. If there is something that
2028 needs changing, review the contents of this file and the contents of the make
2029 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2030 default values are.
2031
2032
2033 .cindex "building Exim" "overriding default settings"
2034 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2035 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2036 need to change the original files. Instead, you should make the changes by
2037 putting the new values in an appropriate &_Local_& file. For example,
2038 .cindex "Tru64-Unix build-time settings"
2039 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2040 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2041 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2042 called with the option &%-std1%&, to make it recognize some of the features of
2043 Standard C that Exim uses. (Most other compilers recognize Standard C by
2044 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2045 containing the lines
2046 .code
2047 CC=cc
2048 CFLAGS=-std1
2049 .endd
2050 If you are compiling for just one operating system, it may be easier to put
2051 these lines directly into &_Local/Makefile_&.
2052
2053 Keeping all your local configuration settings separate from the distributed
2054 files makes it easy to transfer them to new versions of Exim simply by copying
2055 the contents of the &_Local_& directory.
2056
2057
2058 .cindex "NIS lookup type" "including support for"
2059 .cindex "NIS+ lookup type" "including support for"
2060 .cindex "LDAP" "including support for"
2061 .cindex "lookup" "inclusion in binary"
2062 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2063 lookup, but not all systems have these components installed, so the default is
2064 not to include the relevant code in the binary. All the different kinds of file
2065 and database lookup that Exim supports are implemented as separate code modules
2066 which are included only if the relevant compile-time options are set. In the
2067 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2068 .code
2069 LOOKUP_LDAP=yes
2070 LOOKUP_NIS=yes
2071 LOOKUP_NISPLUS=yes
2072 .endd
2073 and similar settings apply to the other lookup types. They are all listed in
2074 &_src/EDITME_&. In many cases the relevant include files and interface
2075 libraries need to be installed before compiling Exim.
2076 .cindex "cdb" "including support for"
2077 However, there are some optional lookup types (such as cdb) for which
2078 the code is entirely contained within Exim, and no external include
2079 files or libraries are required. When a lookup type is not included in the
2080 binary, attempts to configure Exim to use it cause run time configuration
2081 errors.
2082
2083 .cindex "Perl" "including support for"
2084 Exim can be linked with an embedded Perl interpreter, allowing Perl
2085 subroutines to be called during string expansion. To enable this facility,
2086 .code
2087 EXIM_PERL=perl.o
2088 .endd
2089 must be defined in &_Local/Makefile_&. Details of this facility are given in
2090 chapter &<<CHAPperl>>&.
2091
2092 .cindex "X11 libraries, location of"
2093 The location of the X11 libraries is something that varies a lot between
2094 operating systems, and there may be different versions of X11 to cope
2095 with. Exim itself makes no use of X11, but if you are compiling the Exim
2096 monitor, the X11 libraries must be available.
2097 The following three variables are set in &_OS/Makefile-Default_&:
2098 .code
2099 X11=/usr/X11R6
2100 XINCLUDE=-I$(X11)/include
2101 XLFLAGS=-L$(X11)/lib
2102 .endd
2103 These are overridden in some of the operating-system configuration files. For
2104 example, in &_OS/Makefile-SunOS5_& there is
2105 .code
2106 X11=/usr/openwin
2107 XINCLUDE=-I$(X11)/include
2108 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2109 .endd
2110 If you need to override the default setting for your operating system, place a
2111 definition of all three of these variables into your
2112 &_Local/Makefile-<ostype>_& file.
2113
2114 .cindex "EXTRALIBS"
2115 If you need to add any extra libraries to the link steps, these can be put in a
2116 variable called EXTRALIBS, which appears in all the link commands, but by
2117 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2118 command for linking the main Exim binary, and not for any associated utilities.
2119
2120 .cindex "DBM libraries" "configuration for building"
2121 There is also DBMLIB, which appears in the link commands for binaries that
2122 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2123 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2124 binary, and which can be used, for example, to include additional X11
2125 libraries.
2126
2127 .cindex "configuration file" "editing"
2128 The make file copes with rebuilding Exim correctly if any of the configuration
2129 files are edited. However, if an optional configuration file is deleted, it is
2130 necessary to touch the associated non-optional file (that is,
2131 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2132
2133
2134 .section "OS-specific header files" "SECID30"
2135 .cindex "&_os.h_&"
2136 .cindex "building Exim" "OS-specific C header files"
2137 The &_OS_& directory contains a number of files with names of the form
2138 &_os.h-<ostype>_&. These are system-specific C header files that should not
2139 normally need to be changed. There is a list of macro settings that are
2140 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2141 are porting Exim to a new operating system.
2142
2143
2144
2145 .section "Overriding build-time options for the monitor" "SECID31"
2146 .cindex "building Eximon"
2147 A similar process is used for overriding things when building the Exim monitor,
2148 where the files that are involved are
2149 .display
2150 &_OS/eximon.conf-Default_&
2151 &_OS/eximon.conf-_&<&'ostype'&>
2152 &_Local/eximon.conf_&
2153 &_Local/eximon.conf-_&<&'ostype'&>
2154 &_Local/eximon.conf-_&<&'archtype'&>
2155 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2156 .endd
2157 .cindex "&_Local/eximon.conf_&"
2158 As with Exim itself, the final three files need not exist, and in this case the
2159 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2160 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2161 variables of the same name, preceded by EXIMON_. For example, setting
2162 EXIMON_LOG_DEPTH in the environment overrides the value of
2163 LOG_DEPTH at run time.
2164 .ecindex IIDbuex
2165
2166
2167 .section "Installing Exim binaries and scripts" "SECID32"
2168 .cindex "installing Exim"
2169 .cindex "BIN_DIRECTORY"
2170 The command &`make install`& runs the &(exim_install)& script with no
2171 arguments. The script copies binaries and utility scripts into the directory
2172 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2173 .cindex "setuid" "installing Exim with"
2174 The install script copies files only if they are newer than the files they are
2175 going to replace. The Exim binary is required to be owned by root and have the
2176 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2177 install`& as root so that it can set up the Exim binary in this way. However, in
2178 some special situations (for example, if a host is doing no local deliveries)
2179 it may be possible to run Exim without making the binary setuid root (see
2180 chapter &<<CHAPsecurity>>& for details).
2181
2182 .cindex "CONFIGURE_FILE"
2183 Exim's run time configuration file is named by the CONFIGURE_FILE setting
2184 in &_Local/Makefile_&. If this names a single file, and the file does not
2185 exist, the default configuration file &_src/configure.default_& is copied there
2186 by the installation script. If a run time configuration file already exists, it
2187 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2188 alternative files, no default is installed.
2189
2190 .cindex "system aliases file"
2191 .cindex "&_/etc/aliases_&"
2192 One change is made to the default configuration file when it is installed: the
2193 default configuration contains a router that references a system aliases file.
2194 The path to this file is set to the value specified by
2195 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2196 If the system aliases file does not exist, the installation script creates it,
2197 and outputs a comment to the user.
2198
2199 The created file contains no aliases, but it does contain comments about the
2200 aliases a site should normally have. Mail aliases have traditionally been
2201 kept in &_/etc/aliases_&. However, some operating systems are now using
2202 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2203 Exim's configuration if necessary.
2204
2205 The default configuration uses the local host's name as the only local domain,
2206 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2207 running as the local user. System aliases and &_.forward_& files in users' home
2208 directories are supported, but no NIS or NIS+ support is configured. Domains
2209 other than the name of the local host are routed using the DNS, with delivery
2210 over SMTP.
2211
2212 It is possible to install Exim for special purposes (such as building a binary
2213 distribution) in a private part of the file system. You can do this by a
2214 command such as
2215 .code
2216 make DESTDIR=/some/directory/ install
2217 .endd
2218 This has the effect of pre-pending the specified directory to all the file
2219 paths, except the name of the system aliases file that appears in the default
2220 configuration. (If a default alias file is created, its name &'is'& modified.)
2221 For backwards compatibility, ROOT is used if DESTDIR is not set,
2222 but this usage is deprecated.
2223
2224 .cindex "installing Exim" "what is not installed"
2225 Running &'make install'& does not copy the Exim 4 conversion script
2226 &'convert4r4'&. You will probably run this only once if you are
2227 upgrading from Exim 3. None of the documentation files in the &_doc_&
2228 directory are copied, except for the info files when you have set
2229 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2230
2231 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2232 to their names. The Exim binary itself, however, is handled differently. It is
2233 installed under a name that includes the version number and the compile number,
2234 for example &_exim-&version;-1_&. The script then arranges for a symbolic link
2235 called &_exim_& to point to the binary. If you are updating a previous version
2236 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2237 from the directory (as seen by other processes).
2238
2239 .cindex "installing Exim" "testing the script"
2240 If you want to see what the &'make install'& will do before running it for
2241 real, you can pass the &%-n%& option to the installation script by this
2242 command:
2243 .code
2244 make INSTALL_ARG=-n install
2245 .endd
2246 The contents of the variable INSTALL_ARG are passed to the installation
2247 script. You do not need to be root to run this test. Alternatively, you can run
2248 the installation script directly, but this must be from within the build
2249 directory. For example, from the top-level Exim directory you could use this
2250 command:
2251 .code
2252 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2253 .endd
2254 .cindex "installing Exim" "install script options"
2255 There are two other options that can be supplied to the installation script.
2256
2257 .ilist
2258 &%-no_chown%& bypasses the call to change the owner of the installed binary
2259 to root, and the call to make it a setuid binary.
2260 .next
2261 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2262 installed binary.
2263 .endlist
2264
2265 INSTALL_ARG can be used to pass these options to the script. For example:
2266 .code
2267 make INSTALL_ARG=-no_symlink install
2268 .endd
2269 The installation script can also be given arguments specifying which files are
2270 to be copied. For example, to install just the Exim binary, and nothing else,
2271 without creating the symbolic link, you could use:
2272 .code
2273 make INSTALL_ARG='-no_symlink exim' install
2274 .endd
2275
2276
2277
2278 .section "Installing info documentation" "SECTinsinfdoc"
2279 .cindex "installing Exim" "&'info'& documentation"
2280 Not all systems use the GNU &'info'& system for documentation, and for this
2281 reason, the Texinfo source of Exim's documentation is not included in the main
2282 distribution. Instead it is available separately from the ftp site (see section
2283 &<<SECTavail>>&).
2284
2285 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2286 source of the documentation is found in the source tree, running &`make
2287 install`& automatically builds the info files and installs them.
2288
2289
2290
2291 .section "Setting up the spool directory" "SECID33"
2292 .cindex "spool directory" "creating"
2293 When it starts up, Exim tries to create its spool directory if it does not
2294 exist. The Exim uid and gid are used for the owner and group of the spool
2295 directory. Sub-directories are automatically created in the spool directory as
2296 necessary.
2297
2298
2299
2300
2301 .section "Testing" "SECID34"
2302 .cindex "testing" "installation"
2303 Having installed Exim, you can check that the run time configuration file is
2304 syntactically valid by running the following command, which assumes that the
2305 Exim binary directory is within your PATH environment variable:
2306 .code
2307 exim -bV
2308 .endd
2309 If there are any errors in the configuration file, Exim outputs error messages.
2310 Otherwise it outputs the version number and build date,
2311 the DBM library that is being used, and information about which drivers and
2312 other optional code modules are included in the binary.
2313 Some simple routing tests can be done by using the address testing option. For
2314 example,
2315 .display
2316 &`exim -bt`& <&'local username'&>
2317 .endd
2318 should verify that it recognizes a local mailbox, and
2319 .display
2320 &`exim -bt`& <&'remote address'&>
2321 .endd
2322 a remote one. Then try getting it to deliver mail, both locally and remotely.
2323 This can be done by passing messages directly to Exim, without going through a
2324 user agent. For example:
2325 .code
2326 exim -v postmaster@your.domain.example
2327 From: user@your.domain.example
2328 To: postmaster@your.domain.example
2329 Subject: Testing Exim
2330
2331 This is a test message.
2332 ^D
2333 .endd
2334 The &%-v%& option causes Exim to output some verification of what it is doing.
2335 In this case you should see copies of three log lines, one for the message's
2336 arrival, one for its delivery, and one containing &"Completed"&.
2337
2338 .cindex "delivery" "problems with"
2339 If you encounter problems, look at Exim's log files (&'mainlog'& and
2340 &'paniclog'&) to see if there is any relevant information there. Another source
2341 of information is running Exim with debugging turned on, by specifying the
2342 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2343 with debugging turned on by a command of the form
2344 .display
2345 &`exim -d -M`& <&'exim-message-id'&>
2346 .endd
2347 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2348 produces rather a lot of output, but you can cut this down to specific areas.
2349 For example, if you use &%-d-all+route%& only the debugging information
2350 relevant to routing is included. (See the &%-d%& option in chapter
2351 &<<CHAPcommandline>>& for more details.)
2352
2353 .cindex '&"sticky"& bit'
2354 .cindex "lock files"
2355 One specific problem that has shown up on some sites is the inability to do
2356 local deliveries into a shared mailbox directory, because it does not have the
2357 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2358 writing to a mailbox file, and if it cannot create the lock file, the delivery
2359 is deferred. You can get round this either by setting the &"sticky bit"& on the
2360 directory, or by setting a specific group for local deliveries and allowing
2361 that group to create files in the directory (see the comments above the
2362 &(local_delivery)& transport in the default configuration file). Another
2363 approach is to configure Exim not to use lock files, but just to rely on
2364 &[fcntl()]& locking instead. However, you should do this only if all user
2365 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2366 see chapter &<<CHAPappendfile>>&.
2367
2368 One thing that cannot be tested on a system that is already running an MTA is
2369 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2370 &%-oX%& option can be used to run an Exim daemon that listens on some other
2371 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2372 &'exim_checkaccess'& utility can be used to check out policy controls on
2373 incoming SMTP mail.
2374
2375 Testing a new version on a system that is already running Exim can most easily
2376 be done by building a binary with a different CONFIGURE_FILE setting. From
2377 within the run time configuration, all other file and directory names
2378 that Exim uses can be altered, in order to keep it entirely clear of the
2379 production version.
2380
2381
2382 .section "Replacing another MTA with Exim" "SECID35"
2383 .cindex "replacing another MTA"
2384 Building and installing Exim for the first time does not of itself put it in
2385 general use. The name by which the system's MTA is called by mail user agents
2386 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2387 operating system), and it is necessary to make this name point to the &'exim'&
2388 binary in order to get the user agents to pass messages to Exim. This is
2389 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2390 or &_/usr/lib/sendmail_&
2391 .cindex "symbolic link" "to &'exim'& binary"
2392 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2393 privilege and executable status from the old MTA. It is then necessary to stop
2394 and restart the mailer daemon, if one is running.
2395
2396 .cindex "FreeBSD, MTA indirection"
2397 .cindex "&_/etc/mail/mailer.conf_&"
2398 Some operating systems have introduced alternative ways of switching MTAs. For
2399 example, if you are running FreeBSD, you need to edit the file
2400 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2401 described. A typical example of the contents of this file for running Exim is
2402 as follows:
2403 .code
2404 sendmail /usr/exim/bin/exim
2405 send-mail /usr/exim/bin/exim
2406 mailq /usr/exim/bin/exim -bp
2407 newaliases /usr/bin/true
2408 .endd
2409 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2410 your Exim installation is &"live"&. Check it by sending a message from your
2411 favourite user agent.
2412
2413 You should consider what to tell your users about the change of MTA. Exim may
2414 have different capabilities to what was previously running, and there are
2415 various operational differences such as the text of messages produced by
2416 command line options and in bounce messages. If you allow your users to make
2417 use of Exim's filtering capabilities, you should make the document entitled
2418 &'Exim's interface to mail filtering'& available to them.
2419
2420
2421
2422 .section "Upgrading Exim" "SECID36"
2423 .cindex "upgrading Exim"
2424 If you are already running Exim on your host, building and installing a new
2425 version automatically makes it available to MUAs, or any other programs that
2426 call the MTA directly. However, if you are running an Exim daemon, you do need
2427 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2428 new binary. You do not need to stop processing mail in order to install a new
2429 version of Exim. The install script does not modify an existing runtime
2430 configuration file.
2431
2432
2433
2434
2435 .section "Stopping the Exim daemon on Solaris" "SECID37"
2436 .cindex "Solaris" "stopping Exim on"
2437 The standard command for stopping the mailer daemon on Solaris is
2438 .code
2439 /etc/init.d/sendmail stop
2440 .endd
2441 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2442 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2443 for the text &"sendmail"&; this is not present because the actual program name
2444 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2445 solution is to replace the line that finds the process id with something like
2446 .code
2447 pid=`cat /var/spool/exim/exim-daemon.pid`
2448 .endd
2449 to obtain the daemon's pid directly from the file that Exim saves it in.
2450
2451 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2452 still be received from local processes, and if automatic delivery is configured
2453 (the normal case), deliveries will still occur.
2454
2455
2456
2457
2458 . ////////////////////////////////////////////////////////////////////////////
2459 . ////////////////////////////////////////////////////////////////////////////
2460
2461 .chapter "The Exim command line" "CHAPcommandline"
2462 .scindex IIDclo1 "command line" "options"
2463 .scindex IIDclo2 "options" "command line"
2464 Exim's command line takes the standard Unix form of a sequence of options,
2465 each starting with a hyphen character, followed by a number of arguments. The
2466 options are compatible with the main options of Sendmail, and there are also
2467 some additional options, some of which are compatible with Smail 3. Certain
2468 combinations of options do not make sense, and provoke an error if used.
2469 The form of the arguments depends on which options are set.
2470
2471
2472 .section "Setting options by program name" "SECID38"
2473 .cindex "&'mailq'&"
2474 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2475 were present before any other options.
2476 The &%-bp%& option requests a listing of the contents of the mail queue on the
2477 standard output.
2478 This feature is for compatibility with some systems that contain a command of
2479 that name in one of the standard libraries, symbolically linked to
2480 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2481
2482 .cindex "&'rsmtp'&"
2483 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2484 were present before any other options, for compatibility with Smail. The
2485 &%-bS%& option is used for reading in a number of messages in batched SMTP
2486 format.
2487
2488 .cindex "&'rmail'&"
2489 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2490 &%-oee%& options were present before any other options, for compatibility with
2491 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2492
2493 .cindex "&'runq'&"
2494 .cindex "queue runner"
2495 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2496 were present before any other options, for compatibility with Smail. The &%-q%&
2497 option causes a single queue runner process to be started.
2498
2499 .cindex "&'newaliases'&"
2500 .cindex "alias file" "building"
2501 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2502 If Exim is called under the name &'newaliases'& it behaves as if the option
2503 &%-bi%& were present before any other options, for compatibility with Sendmail.
2504 This option is used for rebuilding Sendmail's alias file. Exim does not have
2505 the concept of a single alias file, but can be configured to run a given
2506 command if called with the &%-bi%& option.
2507
2508
2509 .section "Trusted and admin users" "SECTtrustedadmin"
2510 Some Exim options are available only to &'trusted users'& and others are
2511 available only to &'admin users'&. In the description below, the phrases &"Exim
2512 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2513 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2514 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2515
2516 .ilist
2517 .cindex "trusted users" "definition of"
2518 .cindex "user" "trusted definition of"
2519 The trusted users are root, the Exim user, any user listed in the
2520 &%trusted_users%& configuration option, and any user whose current group or any
2521 supplementary group is one of those listed in the &%trusted_groups%&
2522 configuration option. Note that the Exim group is not automatically trusted.
2523
2524 .cindex '&"From"& line'
2525 .cindex "envelope sender"
2526 Trusted users are always permitted to use the &%-f%& option or a leading
2527 &"From&~"& line to specify the envelope sender of a message that is passed to
2528 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2529 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2530 users to set envelope senders.
2531
2532 .cindex "&'From:'& header line"
2533 .cindex "&'Sender:'& header line"
2534 For a trusted user, there is never any check on the contents of the &'From:'&
2535 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2536 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2537
2538 Trusted users may also specify a host name, host address, interface address,
2539 protocol name, ident value, and authentication data when submitting a message
2540 locally. Thus, they are able to insert messages into Exim's queue locally that
2541 have the characteristics of messages received from a remote host. Untrusted
2542 users may in some circumstances use &%-f%&, but can never set the other values
2543 that are available to trusted users.
2544 .next
2545 .cindex "user" "admin definition of"
2546 .cindex "admin user" "definition of"
2547 The admin users are root, the Exim user, and any user that is a member of the
2548 Exim group or of any group listed in the &%admin_groups%& configuration option.
2549 The current group does not have to be one of these groups.
2550
2551 Admin users are permitted to list the queue, and to carry out certain
2552 operations on messages, for example, to force delivery failures. It is also
2553 necessary to be an admin user in order to see the full information provided by
2554 the Exim monitor, and full debugging output.
2555
2556 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2557 Exim to attempt delivery of messages on its queue is restricted to admin users.
2558 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2559 option false (that is, specifying &%no_prod_requires_admin%&).
2560
2561 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2562 is restricted to admin users unless &%queue_list_requires_admin%& is set
2563 false.
2564 .endlist
2565
2566
2567 &*Warning*&: If you configure your system so that admin users are able to
2568 edit Exim's configuration file, you are giving those users an easy way of
2569 getting root. There is further discussion of this issue at the start of chapter
2570 &<<CHAPconf>>&.
2571
2572
2573
2574
2575 .section "Command line options" "SECID39"
2576 Exim's command line options are described in alphabetical order below. If none
2577 of the options that specifies a specific action (such as starting the daemon or
2578 a queue runner, or testing an address, or receiving a message in a specific
2579 format, or listing the queue) are present, and there is at least one argument
2580 on the command line, &%-bm%& (accept a local message on the standard input,
2581 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2582 outputs a brief message about itself and exits.
2583
2584 . ////////////////////////////////////////////////////////////////////////////
2585 . Insert a stylized XML comment here, to identify the start of the command line
2586 . options. This is for the benefit of the Perl script that automatically
2587 . creates a man page for the options.
2588 . ////////////////////////////////////////////////////////////////////////////
2589
2590 .literal xml
2591 <!-- === Start of command line options === -->
2592 .literal off
2593
2594
2595 .vlist
2596 .vitem &%--%&
2597 .oindex "--"
2598 .cindex "options" "command line; terminating"
2599 This is a pseudo-option whose only purpose is to terminate the options and
2600 therefore to cause subsequent command line items to be treated as arguments
2601 rather than options, even if they begin with hyphens.
2602
2603 .vitem &%--help%&
2604 .oindex "&%--help%&"
2605 This option causes Exim to output a few sentences stating what it is.
2606 The same output is generated if the Exim binary is called with no options and
2607 no arguments.
2608
2609 .vitem &%-B%&<&'type'&>
2610 .oindex "&%-B%&"
2611 .cindex "8-bit characters"
2612 .cindex "Sendmail compatibility" "8-bit characters"
2613 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2614 clean; it ignores this option.
2615
2616 .vitem &%-bd%&
2617 .oindex "&%-bd%&"
2618 .cindex "daemon"
2619 .cindex "SMTP" "listener"
2620 .cindex "queue runner"
2621 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2622 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2623 that the daemon should also initiate periodic queue runs.
2624
2625 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2626 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2627 disconnect from the controlling terminal. When running this way, it can be
2628 stopped by pressing ctrl-C.
2629
2630 By default, Exim listens for incoming connections to the standard SMTP port on
2631 all the host's running interfaces. However, it is possible to listen on other
2632 ports, on multiple ports, and only on specific interfaces. Chapter
2633 &<<CHAPinterfaces>>& contains a description of the options that control this.
2634
2635 When a listening daemon
2636 .cindex "daemon" "process id (pid)"
2637 .cindex "pid (process id)" "of daemon"
2638 is started without the use of &%-oX%& (that is, without overriding the normal
2639 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2640 in Exim's spool directory. This location can be overridden by setting
2641 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2642 running as root.
2643
2644 When &%-oX%& is used on the command line to start a listening daemon, the
2645 process id is not written to the normal pid file path. However, &%-oP%& can be
2646 used to specify a path on the command line if a pid file is required.
2647
2648 The SIGHUP signal
2649 .cindex "SIGHUP"
2650 .cindex "daemon" "restarting"
2651 can be used to cause the daemon to re-execute itself. This should be done
2652 whenever Exim's configuration file, or any file that is incorporated into it by
2653 means of the &%.include%& facility, is changed, and also whenever a new version
2654 of Exim is installed. It is not necessary to do this when other files that are
2655 referenced from the configuration (for example, alias files) are changed,
2656 because these are reread each time they are used.
2657
2658 .vitem &%-bdf%&
2659 .oindex "&%-bdf%&"
2660 This option has the same effect as &%-bd%& except that it never disconnects
2661 from the controlling terminal, even when no debugging is specified.
2662
2663 .vitem &%-be%&
2664 .oindex "&%-be%&"
2665 .cindex "testing" "string expansion"
2666 .cindex "expansion" "testing"
2667 Run Exim in expansion testing mode. Exim discards its root privilege, to
2668 prevent ordinary users from using this mode to read otherwise inaccessible
2669 files. If no arguments are given, Exim runs interactively, prompting for lines
2670 of data. Otherwise, it processes each argument in turn.
2671
2672 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2673 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2674 used without command line arguments. If successful, it uses the &[readline()]&
2675 function, which provides extensive line-editing facilities, for reading the
2676 test data. A line history is supported.
2677
2678 Long expansion expressions can be split over several lines by using backslash
2679 continuations. As in Exim's run time configuration, white space at the start of
2680 continuation lines is ignored. Each argument or data line is passed through the
2681 string expansion mechanism, and the result is output. Variable values from the
2682 configuration file (for example, &$qualify_domain$&) are available, but no
2683 message-specific values (such as &$sender_domain$&) are set, because no message
2684 is being processed (but see &%-bem%& and &%-Mset%&).
2685
2686 &*Note*&: If you use this mechanism to test lookups, and you change the data
2687 files or databases you are using, you must exit and restart Exim before trying
2688 the same lookup again. Otherwise, because each Exim process caches the results
2689 of lookups, you will just get the same result as before.
2690
2691 .vitem &%-bem%&&~<&'filename'&>
2692 .oindex "&%-bem%&"
2693 .cindex "testing" "string expansion"
2694 .cindex "expansion" "testing"
2695 This option operates like &%-be%& except that it must be followed by the name
2696 of a file. For example:
2697 .code
2698 exim -bem /tmp/testmessage
2699 .endd
2700 The file is read as a message (as if receiving a locally-submitted non-SMTP
2701 message) before any of the test expansions are done. Thus, message-specific
2702 variables such as &$message_size$& and &$header_from:$& are available. However,
2703 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2704 recipients are read from the headers in the normal way, and are shown in the
2705 &$recipients$& variable. Note that recipients cannot be given on the command
2706 line, because further arguments are taken as strings to expand (just like
2707 &%-be%&).
2708
2709 .vitem &%-bF%&&~<&'filename'&>
2710 .oindex "&%-bF%&"
2711 .cindex "system filter" "testing"
2712 .cindex "testing" "system filter"
2713 This option is the same as &%-bf%& except that it assumes that the filter being
2714 tested is a system filter. The additional commands that are available only in
2715 system filters are recognized.
2716
2717 .vitem &%-bf%&&~<&'filename'&>
2718 .oindex "&%-bf%&"
2719 .cindex "filter" "testing"
2720 .cindex "testing" "filter file"
2721 .cindex "forward file" "testing"
2722 .cindex "testing" "forward file"
2723 .cindex "Sieve filter" "testing"
2724 This option runs Exim in user filter testing mode; the file is the filter file
2725 to be tested, and a test message must be supplied on the standard input. If
2726 there are no message-dependent tests in the filter, an empty file can be
2727 supplied.
2728
2729 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2730 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2731 filter and a user filter in the same run. For example:
2732 .code
2733 exim -bF /system/filter -bf /user/filter </test/message
2734 .endd
2735 This is helpful when the system filter adds header lines or sets filter
2736 variables that are used by the user filter.
2737
2738 If the test filter file does not begin with one of the special lines
2739 .code
2740 # Exim filter
2741 # Sieve filter
2742 .endd
2743 it is taken to be a normal &_.forward_& file, and is tested for validity under
2744 that interpretation. See sections &<<SECTitenonfilred>>& to
2745 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2746 redirection lists.
2747
2748 The result of an Exim command that uses &%-bf%&, provided no errors are
2749 detected, is a list of the actions that Exim would try to take if presented
2750 with the message for real. More details of filter testing are given in the
2751 separate document entitled &'Exim's interfaces to mail filtering'&.
2752
2753 When testing a filter file,
2754 .cindex "&""From""& line"
2755 .cindex "envelope sender"
2756 .oindex "&%-f%&" "for filter testing"
2757 the envelope sender can be set by the &%-f%& option,
2758 or by a &"From&~"& line at the start of the test message. Various parameters
2759 that would normally be taken from the envelope recipient address of the message
2760 can be set by means of additional command line options (see the next four
2761 options).
2762
2763 .vitem &%-bfd%&&~<&'domain'&>
2764 .oindex "&%-bfd%&"
2765 .vindex "&$qualify_domain$&"
2766 This sets the domain of the recipient address when a filter file is being
2767 tested by means of the &%-bf%& option. The default is the value of
2768 &$qualify_domain$&.
2769
2770 .vitem &%-bfl%&&~<&'local&~part'&>
2771 .oindex "&%-bfl%&"
2772 This sets the local part of the recipient address when a filter file is being
2773 tested by means of the &%-bf%& option. The default is the username of the
2774 process that calls Exim. A local part should be specified with any prefix or
2775 suffix stripped, because that is how it appears to the filter when a message is
2776 actually being delivered.
2777
2778 .vitem &%-bfp%&&~<&'prefix'&>
2779 .oindex "&%-bfp%&"
2780 This sets the prefix of the local part of the recipient address when a filter
2781 file is being tested by means of the &%-bf%& option. The default is an empty
2782 prefix.
2783
2784 .vitem &%-bfs%&&~<&'suffix'&>
2785 .oindex "&%-bfs%&"
2786 This sets the suffix of the local part of the recipient address when a filter
2787 file is being tested by means of the &%-bf%& option. The default is an empty
2788 suffix.
2789
2790 .vitem &%-bh%&&~<&'IP&~address'&>
2791 .oindex "&%-bh%&"
2792 .cindex "testing" "incoming SMTP"
2793 .cindex "SMTP" "testing incoming"
2794 .cindex "testing" "relay control"
2795 .cindex "relaying" "testing configuration"
2796 .cindex "policy control" "testing"
2797 .cindex "debugging" "&%-bh%& option"
2798 This option runs a fake SMTP session as if from the given IP address, using the
2799 standard input and output. The IP address may include a port number at the end,
2800 after a full stop. For example:
2801 .code
2802 exim -bh 10.9.8.7.1234
2803 exim -bh fe80::a00:20ff:fe86:a061.5678
2804 .endd
2805 When an IPv6 address is given, it is converted into canonical form. In the case
2806 of the second example above, the value of &$sender_host_address$& after
2807 conversion to the canonical form is
2808 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2809
2810 Comments as to what is going on are written to the standard error file. These
2811 include lines beginning with &"LOG"& for anything that would have been logged.
2812 This facility is provided for testing configuration options for incoming
2813 messages, to make sure they implement the required policy. For example, you can
2814 test your relay controls using &%-bh%&.
2815
2816 &*Warning 1*&:
2817 .cindex "RFC 1413"
2818 You can test features of the configuration that rely on ident (RFC 1413)
2819 information by using the &%-oMt%& option. However, Exim cannot actually perform
2820 an ident callout when testing using &%-bh%& because there is no incoming SMTP
2821 connection.
2822
2823 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2824 are also skipped when testing using &%-bh%&. If you want these callouts to
2825 occur, use &%-bhc%& instead.
2826
2827 Messages supplied during the testing session are discarded, and nothing is
2828 written to any of the real log files. There may be pauses when DNS (and other)
2829 lookups are taking place, and of course these may time out. The &%-oMi%& option
2830 can be used to specify a specific IP interface and port if this is important,
2831 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
2832 session were authenticated.
2833
2834 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2835 output just states whether a given recipient address from a given host is
2836 acceptable or not. See section &<<SECTcheckaccess>>&.
2837
2838 Features such as authentication and encryption, where the client input is not
2839 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
2840 specialized SMTP test program such as
2841 &url(http://jetmore.org/john/code/#swaks,swaks).
2842
2843 .vitem &%-bhc%&&~<&'IP&~address'&>
2844 .oindex "&%-bhc%&"
2845 This option operates in the same way as &%-bh%&, except that address
2846 verification callouts are performed if required. This includes consulting and
2847 updating the callout cache database.
2848
2849 .vitem &%-bi%&
2850 .oindex "&%-bi%&"
2851 .cindex "alias file" "building"
2852 .cindex "building alias file"
2853 .cindex "Sendmail compatibility" "&%-bi%& option"
2854 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
2855 Exim does not have the concept of a single alias file, and so it cannot mimic
2856 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
2857 tend to appear in various scripts such as NIS make files, so the option must be
2858 recognized.
2859
2860 If &%-bi%& is encountered, the command specified by the &%bi_command%&
2861 configuration option is run, under the uid and gid of the caller of Exim. If
2862 the &%-oA%& option is used, its value is passed to the command as an argument.
2863 The command set by &%bi_command%& may not contain arguments. The command can
2864 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
2865 if this is required. If the &%bi_command%& option is not set, calling Exim with
2866 &%-bi%& is a no-op.
2867
2868 .vitem &%-bm%&
2869 .oindex "&%-bm%&"
2870 .cindex "local message reception"
2871 This option runs an Exim receiving process that accepts an incoming,
2872 locally-generated message on the current input. The recipients are given as the
2873 command arguments (except when &%-t%& is also present &-- see below). Each
2874 argument can be a comma-separated list of RFC 2822 addresses. This is the
2875 default option for selecting the overall action of an Exim call; it is assumed
2876 if no other conflicting option is present.
2877
2878 If any addresses in the message are unqualified (have no domain), they are
2879 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
2880 options, as appropriate. The &%-bnq%& option (see below) provides a way of
2881 suppressing this for special cases.
2882
2883 Policy checks on the contents of local messages can be enforced by means of
2884 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
2885
2886 .cindex "return code" "for &%-bm%&"
2887 The return code is zero if the message is successfully accepted. Otherwise, the
2888 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
2889
2890 The format
2891 .cindex "message" "format"
2892 .cindex "format" "message"
2893 .cindex "&""From""& line"
2894 .cindex "UUCP" "&""From""& line"
2895 .cindex "Sendmail compatibility" "&""From""& line"
2896 of the message must be as defined in RFC 2822, except that, for
2897 compatibility with Sendmail and Smail, a line in one of the forms
2898 .code
2899 From sender Fri Jan 5 12:55 GMT 1997
2900 From sender Fri, 5 Jan 97 12:55:01
2901 .endd
2902 (with the weekday optional, and possibly with additional text after the date)
2903 is permitted to appear at the start of the message. There appears to be no
2904 authoritative specification of the format of this line. Exim recognizes it by
2905 matching against the regular expression defined by the &%uucp_from_pattern%&
2906 option, which can be changed if necessary.
2907
2908 .oindex "&%-f%&" "overriding &""From""& line"
2909 The specified sender is treated as if it were given as the argument to the
2910 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
2911 preference to the address taken from the message. The caller of Exim must be a
2912 trusted user for the sender of a message to be set in this way.
2913
2914 .vitem &%-bnq%&
2915 .oindex "&%-bnq%&"
2916 .cindex "address qualification, suppressing"
2917 By default, Exim automatically qualifies unqualified addresses (those
2918 without domains) that appear in messages that are submitted locally (that
2919 is, not over TCP/IP). This qualification applies both to addresses in
2920 envelopes, and addresses in header lines. Sender addresses are qualified using
2921 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
2922 defaults to the value of &%qualify_domain%&).
2923
2924 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
2925 being used to re-submit messages that originally came from remote hosts after
2926 content scanning, you probably do not want to qualify unqualified addresses in
2927 header lines. (Such lines will be present only if you have not enabled a header
2928 syntax check in the appropriate ACL.)
2929
2930 The &%-bnq%& option suppresses all qualification of unqualified addresses in
2931 messages that originate on the local host. When this is used, unqualified
2932 addresses in the envelope provoke errors (causing message rejection) and
2933 unqualified addresses in header lines are left alone.
2934
2935
2936 .vitem &%-bP%&
2937 .oindex "&%-bP%&"
2938 .cindex "configuration options" "extracting"
2939 .cindex "options" "configuration &-- extracting"
2940 If this option is given with no arguments, it causes the values of all Exim's
2941 main configuration options to be written to the standard output. The values
2942 of one or more specific options can be requested by giving their names as
2943 arguments, for example:
2944 .code
2945 exim -bP qualify_domain hold_domains
2946 .endd
2947 .cindex "hiding configuration option values"
2948 .cindex "configuration options" "hiding value of"
2949 .cindex "options" "hiding value of"
2950 However, any option setting that is preceded by the word &"hide"& in the
2951 configuration file is not shown in full, except to an admin user. For other
2952 users, the output is as in this example:
2953 .code
2954 mysql_servers = <value not displayable>
2955 .endd
2956 If &%configure_file%& is given as an argument, the name of the run time
2957 configuration file is output.
2958 If a list of configuration files was supplied, the value that is output here
2959 is the name of the file that was actually used.
2960
2961 .cindex "daemon" "process id (pid)"
2962 .cindex "pid (process id)" "of daemon"
2963 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
2964 directories where log files and daemon pid files are written are output,
2965 respectively. If these values are unset, log files are written in a
2966 sub-directory of the spool directory called &%log%&, and the pid file is
2967 written directly into the spool directory.
2968
2969 If &%-bP%& is followed by a name preceded by &`+`&, for example,
2970 .code
2971 exim -bP +local_domains
2972 .endd
2973 it searches for a matching named list of any type (domain, host, address, or
2974 local part) and outputs what it finds.
2975
2976 .cindex "options" "router &-- extracting"
2977 .cindex "options" "transport &-- extracting"
2978 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
2979 followed by the name of an appropriate driver instance, the option settings for
2980 that driver are output. For example:
2981 .code
2982 exim -bP transport local_delivery
2983 .endd
2984 The generic driver options are output first, followed by the driver's private
2985 options. A list of the names of drivers of a particular type can be obtained by
2986 using one of the words &%router_list%&, &%transport_list%&, or
2987 &%authenticator_list%&, and a complete list of all drivers with their option
2988 settings can be obtained by using &%routers%&, &%transports%&, or
2989 &%authenticators%&.
2990
2991
2992 .vitem &%-bp%&
2993 .oindex "&%-bp%&"
2994 .cindex "queue" "listing messages on"
2995 .cindex "listing" "messages on the queue"
2996 This option requests a listing of the contents of the mail queue on the
2997 standard output. If the &%-bp%& option is followed by a list of message ids,
2998 just those messages are listed. By default, this option can be used only by an
2999 admin user. However, the &%queue_list_requires_admin%& option can be set false
3000 to allow any user to see the queue.
3001
3002 Each message on the queue is displayed as in the following example:
3003 .code
3004 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3005 red.king@looking-glass.fict.example
3006 <other addresses>
3007 .endd
3008 .cindex "message" "size in queue listing"
3009 .cindex "size" "of message"
3010 The first line contains the length of time the message has been on the queue
3011 (in this case 25 minutes), the size of the message (2.9K), the unique local
3012 identifier for the message, and the message sender, as contained in the
3013 envelope. For bounce messages, the sender address is empty, and appears as
3014 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3015 the default sender address, the user's login name is shown in parentheses
3016 before the sender address.
3017
3018 .cindex "frozen messages" "in queue listing"
3019 If the message is frozen (attempts to deliver it are suspended) then the text
3020 &"*** frozen ***"& is displayed at the end of this line.
3021
3022 The recipients of the message (taken from the envelope, not the headers) are
3023 displayed on subsequent lines. Those addresses to which the message has already
3024 been delivered are marked with the letter D. If an original address gets
3025 expanded into several addresses via an alias or forward file, the original is
3026 displayed with a D only when deliveries for all of its child addresses are
3027 complete.
3028
3029
3030 .vitem &%-bpa%&
3031 .oindex "&%-bpa%&"
3032 This option operates like &%-bp%&, but in addition it shows delivered addresses
3033 that were generated from the original top level address(es) in each message by
3034 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3035 of just &"D"&.
3036
3037
3038 .vitem &%-bpc%&
3039 .oindex "&%-bpc%&"
3040 .cindex "queue" "count of messages on"
3041 This option counts the number of messages on the queue, and writes the total
3042 to the standard output. It is restricted to admin users, unless
3043 &%queue_list_requires_admin%& is set false.
3044
3045
3046 .vitem &%-bpr%&
3047 .oindex "&%-bpr%&"
3048 This option operates like &%-bp%&, but the output is not sorted into
3049 chronological order of message arrival. This can speed it up when there are
3050 lots of messages on the queue, and is particularly useful if the output is
3051 going to be post-processed in a way that doesn't need the sorting.
3052
3053 .vitem &%-bpra%&
3054 .oindex "&%-bpra%&"
3055 This option is a combination of &%-bpr%& and &%-bpa%&.
3056
3057 .vitem &%-bpru%&
3058 .oindex "&%-bpru%&"
3059 This option is a combination of &%-bpr%& and &%-bpu%&.
3060
3061
3062 .vitem &%-bpu%&
3063 .oindex "&%-bpu%&"
3064 This option operates like &%-bp%& but shows only undelivered top-level
3065 addresses for each message displayed. Addresses generated by aliasing or
3066 forwarding are not shown, unless the message was deferred after processing by a
3067 router with the &%one_time%& option set.
3068
3069
3070 .vitem &%-brt%&
3071 .oindex "&%-brt%&"
3072 .cindex "testing" "retry configuration"
3073 .cindex "retry" "configuration testing"
3074 This option is for testing retry rules, and it must be followed by up to three
3075 arguments. It causes Exim to look for a retry rule that matches the values
3076 and to write it to the standard output. For example:
3077 .code
3078 exim -brt bach.comp.mus.example
3079 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3080 .endd
3081 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3082 argument, which is required, can be a complete address in the form
3083 &'local_part@domain'&, or it can be just a domain name. If the second argument
3084 contains a dot, it is interpreted as an optional second domain name; if no
3085 retry rule is found for the first argument, the second is tried. This ties in
3086 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3087 rule is found that matches the host, one that matches the mail domain is
3088 sought. Finally, an argument that is the name of a specific delivery error, as
3089 used in setting up retry rules, can be given. For example:
3090 .code
3091 exim -brt haydn.comp.mus.example quota_3d
3092 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3093 .endd
3094
3095 .vitem &%-brw%&
3096 .oindex "&%-brw%&"
3097 .cindex "testing" "rewriting"
3098 .cindex "rewriting" "testing"
3099 This option is for testing address rewriting rules, and it must be followed by
3100 a single argument, consisting of either a local part without a domain, or a
3101 complete address with a fully qualified domain. Exim outputs how this address
3102 would be rewritten for each possible place it might appear. See chapter
3103 &<<CHAPrewrite>>& for further details.
3104
3105 .vitem &%-bS%&
3106 .oindex "&%-bS%&"
3107 .cindex "SMTP" "batched incoming"
3108 .cindex "batched SMTP input"
3109 This option is used for batched SMTP input, which is an alternative interface
3110 for non-interactive local message submission. A number of messages can be
3111 submitted in a single run. However, despite its name, this is not really SMTP
3112 input. Exim reads each message's envelope from SMTP commands on the standard
3113 input, but generates no responses. If the caller is trusted, or
3114 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3115 believed; otherwise the sender is always the caller of Exim.
3116
3117 The message itself is read from the standard input, in SMTP format (leading
3118 dots doubled), terminated by a line containing just a single dot. An error is
3119 provoked if the terminating dot is missing. A further message may then follow.
3120
3121 As for other local message submissions, the contents of incoming batch SMTP
3122 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3123 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3124 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3125
3126 Some other SMTP commands are recognized in the input. HELO and EHLO act
3127 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3128 QUIT quits, ignoring the rest of the standard input.
3129
3130 .cindex "return code" "for &%-bS%&"
3131 If any error is encountered, reports are written to the standard output and
3132 error streams, and Exim gives up immediately. The return code is 0 if no error
3133 was detected; it is 1 if one or more messages were accepted before the error
3134 was detected; otherwise it is 2.
3135
3136 More details of input using batched SMTP are given in section
3137 &<<SECTincomingbatchedSMTP>>&.
3138
3139 .vitem &%-bs%&
3140 .oindex "&%-bs%&"
3141 .cindex "SMTP" "local input"
3142 .cindex "local SMTP input"
3143 This option causes Exim to accept one or more messages by reading SMTP commands
3144 on the standard input, and producing SMTP replies on the standard output. SMTP
3145 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3146 Some user agents use this interface as a way of passing locally-generated
3147 messages to the MTA.
3148
3149 In
3150 .cindex "sender" "source of"
3151 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3152 set, the senders of messages are taken from the SMTP MAIL commands.
3153 Otherwise the content of these commands is ignored and the sender is set up as
3154 the calling user. Unqualified addresses are automatically qualified using
3155 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3156 &%-bnq%& option is used.
3157
3158 .cindex "inetd"
3159 The
3160 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3161 using a listening daemon. Exim can distinguish the two cases by checking
3162 whether the standard input is a TCP/IP socket. When Exim is called from
3163 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3164 above concerning senders and qualification do not apply. In this situation,
3165 Exim behaves in exactly the same way as it does when receiving a message via
3166 the listening daemon.
3167
3168 .vitem &%-bt%&
3169 .oindex "&%-bt%&"
3170 .cindex "testing" "addresses"
3171 .cindex "address" "testing"
3172 This option runs Exim in address testing mode, in which each argument is taken
3173 as a recipient address to be tested for deliverability. The results are
3174 written to the standard output. If a test fails, and the caller is not an admin
3175 user, no details of the failure are output, because these might contain
3176 sensitive information such as usernames and passwords for database lookups.
3177
3178 If no arguments are given, Exim runs in an interactive manner, prompting with a
3179 right angle bracket for addresses to be tested.
3180
3181 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3182 &[readline()]& function, because it is running as &'root'& and there are
3183 security issues.
3184
3185 Each address is handled as if it were the recipient address of a message
3186 (compare the &%-bv%& option). It is passed to the routers and the result is
3187 written to the standard output. However, any router that has
3188 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3189 genuine routing tests if your first router passes everything to a scanner
3190 program.
3191
3192 .cindex "return code" "for &%-bt%&"
3193 The return code is 2 if any address failed outright; it is 1 if no address
3194 failed outright but at least one could not be resolved for some reason. Return
3195 code 0 is given only when all addresses succeed.
3196
3197 .cindex "duplicate addresses"
3198 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3199 addresses after routing is complete, so that only one delivery takes place.
3200 This does not happen when testing with &%-bt%&; the full results of routing are
3201 always shown.
3202
3203 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3204 routers in the configuration makes any tests on the sender address of a
3205 message,
3206 .oindex "&%-f%&" "for address testing"
3207 you can use the &%-f%& option to set an appropriate sender when running
3208 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3209 default qualifying domain. However, if you have set up (for example) routers
3210 whose behaviour depends on the contents of an incoming message, you cannot test
3211 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3212 doing such tests.
3213
3214 .vitem &%-bV%&
3215 .oindex "&%-bV%&"
3216 .cindex "version number of Exim"
3217 This option causes Exim to write the current version number, compilation
3218 number, and compilation date of the &'exim'& binary to the standard output.
3219 It also lists the DBM library this is being used, the optional modules (such as
3220 specific lookup types), the drivers that are included in the binary, and the
3221 name of the run time configuration file that is in use.
3222
3223 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3224 configuration file. However, this is a static check only. It cannot check
3225 values that are to be expanded. For example, although a misspelt ACL verb is
3226 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3227 alone to discover (for example) all the typos in the configuration; some
3228 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3229 dynamic testing facilities.
3230
3231 .vitem &%-bv%&
3232 .oindex "&%-bv%&"
3233 .cindex "verifying address" "using &%-bv%&"
3234 .cindex "address" "verification"
3235 This option runs Exim in address verification mode, in which each argument is
3236 taken as a recipient address to be verified by the routers. (This does
3237 not involve any verification callouts). During normal operation, verification
3238 happens mostly as a consequence processing a &%verify%& condition in an ACL
3239 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3240 including callouts, see the &%-bh%& and &%-bhc%& options.
3241
3242 If verification fails, and the caller is not an admin user, no details of the
3243 failure are output, because these might contain sensitive information such as
3244 usernames and passwords for database lookups.
3245
3246 If no arguments are given, Exim runs in an interactive manner, prompting with a
3247 right angle bracket for addresses to be verified.
3248
3249 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3250 &[readline()]& function, because it is running as &'exim'& and there are
3251 security issues.
3252
3253 Verification differs from address testing (the &%-bt%& option) in that routers
3254 that have &%no_verify%& set are skipped, and if the address is accepted by a
3255 router that has &%fail_verify%& set, verification fails. The address is
3256 verified as a recipient if &%-bv%& is used; to test verification for a sender
3257 address, &%-bvs%& should be used.
3258
3259 If the &%-v%& option is not set, the output consists of a single line for each
3260 address, stating whether it was verified or not, and giving a reason in the
3261 latter case. Without &%-v%&, generating more than one address by redirection
3262 causes verification to end successfully, without considering the generated
3263 addresses. However, if just one address is generated, processing continues,
3264 and the generated address must verify successfully for the overall verification
3265 to succeed.
3266
3267 When &%-v%& is set, more details are given of how the address has been handled,
3268 and in the case of address redirection, all the generated addresses are also
3269 considered. Verification may succeed for some and fail for others.
3270
3271 The
3272 .cindex "return code" "for &%-bv%&"
3273 return code is 2 if any address failed outright; it is 1 if no address
3274 failed outright but at least one could not be resolved for some reason. Return
3275 code 0 is given only when all addresses succeed.
3276
3277 If any of the routers in the configuration makes any tests on the sender
3278 address of a message, you should use the &%-f%& option to set an appropriate
3279 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3280 calling user at the default qualifying domain.
3281
3282 .vitem &%-bvs%&
3283 .oindex "&%-bvs%&"
3284 This option acts like &%-bv%&, but verifies the address as a sender rather
3285 than a recipient address. This affects any rewriting and qualification that
3286 might happen.
3287
3288 .vitem &%-C%&&~<&'filelist'&>
3289 .oindex "&%-C%&"
3290 .cindex "configuration file" "alternate"
3291 .cindex "CONFIGURE_FILE"
3292 .cindex "alternate configuration file"
3293 This option causes Exim to find the run time configuration file from the given
3294 list instead of from the list specified by the CONFIGURE_FILE
3295 compile-time setting. Usually, the list will consist of just a single file
3296 name, but it can be a colon-separated list of names. In this case, the first
3297 file that exists is used. Failure to open an existing file stops Exim from
3298 proceeding any further along the list, and an error is generated.
3299
3300 When this option is used by a caller other than root or the Exim user, and the
3301 list is different from the compiled-in list, Exim gives up its root privilege
3302 immediately, and runs with the real and effective uid and gid set to those of
3303 the caller. However, if ALT_CONFIG_ROOT_ONLY is defined in
3304 &_Local/Makefile_&, root privilege is retained for &%-C%& only if the caller of
3305 Exim is root.
3306
3307 That is, the Exim user is no longer privileged in this regard. This build-time
3308 option is not set by default in the Exim source distribution tarbundle.
3309 However, if you are using a &"packaged"& version of Exim (source or binary),
3310 the packagers might have enabled it.
3311
3312 Setting ALT_CONFIG_ROOT_ONLY locks out the possibility of testing a
3313 configuration using &%-C%& right through message reception and delivery, even
3314 if the caller is root. The reception works, but by that time, Exim is running
3315 as the Exim user, so when it re-executes to regain privilege for the delivery,
3316 the use of &%-C%& causes privilege to be lost. However, root can test reception
3317 and delivery using two separate commands (one to put a message on the queue,
3318 using &%-odq%&, and another to do the delivery, using &%-M%&).
3319
3320 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3321 prefix string with which any file named in a &%-C%& command line option
3322 must start. In addition, the file name must not contain the sequence &`/../`&.
3323 However, if the value of the &%-C%& option is identical to the value of
3324 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3325 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3326 unset, any file name can be used with &%-C%&.
3327
3328 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3329 to a directory to which only root has access. This prevents someone who has
3330 broken into the Exim account from running a privileged Exim with an arbitrary
3331 configuration file.
3332
3333 The &%-C%& facility is useful for ensuring that configuration files are
3334 syntactically correct, but cannot be used for test deliveries, unless the
3335 caller is privileged, or unless it is an exotic configuration that does not
3336 require privilege. No check is made on the owner or group of the files
3337 specified by this option.
3338
3339 .vitem &%-D%&<&'macro'&>=<&'value'&>
3340 .oindex "&%-D%&"
3341 .cindex "macro" "setting on command line"
3342 This option can be used to override macro definitions in the configuration file
3343 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3344 unprivileged caller, it causes Exim to give up its root privilege.
3345 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3346 completely disabled, and its use causes an immediate error exit.
3347
3348 The entire option (including equals sign if present) must all be within one
3349 command line item. &%-D%& can be used to set the value of a macro to the empty
3350 string, in which case the equals sign is optional. These two commands are
3351 synonymous:
3352 .code
3353 exim -DABC ...
3354 exim -DABC= ...
3355 .endd
3356 To include spaces in a macro definition item, quotes must be used. If you use
3357 quotes, spaces are permitted around the macro name and the equals sign. For
3358 example:
3359 .code
3360 exim '-D ABC = something' ...
3361 .endd
3362 &%-D%& may be repeated up to 10 times on a command line.
3363
3364 .vitem &%-d%&<&'debug&~options'&>
3365 .oindex "&%-d%&"
3366 .cindex "debugging" "list of selectors"
3367 .cindex "debugging" "&%-d%& option"
3368 This option causes debugging information to be written to the standard
3369 error stream. It is restricted to admin users because debugging output may show
3370 database queries that contain password information. Also, the details of users'
3371 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3372 writes an error message to the standard error stream and exits with a non-zero
3373 return code.
3374
3375 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3376 standard debugging data is output. This can be reduced, or increased to include
3377 some more rarely needed information, by directly following &%-d%& with a string
3378 made up of names preceded by plus or minus characters. These add or remove sets
3379 of debugging data, respectively. For example, &%-d+filter%& adds filter
3380 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3381 no spaces are allowed in the debug setting. The available debugging categories
3382 are:
3383 .display
3384 &`acl `& ACL interpretation
3385 &`auth `& authenticators
3386 &`deliver `& general delivery logic
3387 &`dns `& DNS lookups (see also resolver)
3388 &`dnsbl `& DNS black list (aka RBL) code
3389 &`exec `& arguments for &[execv()]& calls
3390 &`expand `& detailed debugging for string expansions
3391 &`filter `& filter handling
3392 &`hints_lookup `& hints data lookups
3393 &`host_lookup `& all types of name-to-IP address handling
3394 &`ident `& ident lookup
3395 &`interface `& lists of local interfaces
3396 &`lists `& matching things in lists
3397 &`load `& system load checks
3398 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3399 &<<CHAPlocalscan>>&)
3400 &`lookup `& general lookup code and all lookups
3401 &`memory `& memory handling
3402 &`pid `& add pid to debug output lines
3403 &`process_info `& setting info for the process log
3404 &`queue_run `& queue runs
3405 &`receive `& general message reception logic
3406 &`resolver `& turn on the DNS resolver's debugging output
3407 &`retry `& retry handling
3408 &`rewrite `& address rewriting
3409 &`route `& address routing
3410 &`timestamp `& add timestamp to debug output lines
3411 &`tls `& TLS logic
3412 &`transport `& transports
3413 &`uid `& changes of uid/gid and looking up uid/gid
3414 &`verify `& address verification logic
3415 &`all `& almost all of the above (see below), and also &%-v%&
3416 .endd
3417 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3418 for &`-all`&. The reason for this is that &`+all`& is something that people
3419 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3420 is included, an awful lot of output that is very rarely of interest is
3421 generated, so it now has to be explicitly requested. However, &`-all`& does
3422 turn everything off.
3423
3424 .cindex "resolver, debugging output"
3425 .cindex "DNS resolver, debugging output"
3426 The &`resolver`& option produces output only if the DNS resolver was compiled
3427 with DEBUG enabled. This is not the case in some operating systems. Also,
3428 unfortunately, debugging output from the DNS resolver is written to stdout
3429 rather than stderr.
3430
3431 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3432 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3433 However, the &`pid`& selector is forced when debugging is turned on for a
3434 daemon, which then passes it on to any re-executed Exims. Exim also
3435 automatically adds the pid to debug lines when several remote deliveries are
3436 run in parallel.
3437
3438 The &`timestamp`& selector causes the current time to be inserted at the start
3439 of all debug output lines. This can be useful when trying to track down delays
3440 in processing.
3441
3442 If the &%debug_print%& option is set in any driver, it produces output whenever
3443 any debugging is selected, or if &%-v%& is used.
3444
3445 .vitem &%-dd%&<&'debug&~options'&>
3446 .oindex "&%-dd%&"
3447 This option behaves exactly like &%-d%& except when used on a command that
3448 starts a daemon process. In that case, debugging is turned off for the
3449 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3450 behaviour of the daemon without creating as much output as full debugging does.
3451
3452 .vitem &%-dropcr%&
3453 .oindex "&%-dropcr%&"
3454 This is an obsolete option that is now a no-op. It used to affect the way Exim
3455 handled CR and LF characters in incoming messages. What happens now is
3456 described in section &<<SECTlineendings>>&.
3457
3458 .vitem &%-E%&
3459 .oindex "&%-E%&"
3460 .cindex "bounce message" "generating"
3461 This option specifies that an incoming message is a locally-generated delivery
3462 failure report. It is used internally by Exim when handling delivery failures
3463 and is not intended for external use. Its only effect is to stop Exim
3464 generating certain messages to the postmaster, as otherwise message cascades
3465 could occur in some situations. As part of the same option, a message id may
3466 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3467 new message contains the id, following &"R="&, as a cross-reference.
3468
3469 .vitem &%-e%&&'x'&
3470 .oindex "&%-e%&&'x'&"
3471 There are a number of Sendmail options starting with &%-oe%& which seem to be
3472 called by various programs without the leading &%o%& in the option. For
3473 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3474 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3475
3476 .vitem &%-F%&&~<&'string'&>
3477 .oindex "&%-F%&"
3478 .cindex "sender" "name"
3479 .cindex "name" "of sender"
3480 This option sets the sender's full name for use when a locally-generated
3481 message is being accepted. In the absence of this option, the user's &'gecos'&
3482 entry from the password data is used. As users are generally permitted to alter
3483 their &'gecos'& entries, no security considerations are involved. White space
3484 between &%-F%& and the <&'string'&> is optional.
3485
3486 .vitem &%-f%&&~<&'address'&>
3487 .oindex "&%-f%&"
3488 .cindex "sender" "address"
3489 .cindex "address" "sender"
3490 .cindex "trusted users"
3491 .cindex "envelope sender"
3492 .cindex "user" "trusted"
3493 This option sets the address of the envelope sender of a locally-generated
3494 message (also known as the return path). The option can normally be used only
3495 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3496 users to use it.
3497
3498 Processes running as root or the Exim user are always trusted. Other
3499 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3500 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3501 of a local message is set to the caller's login name at the default qualify
3502 domain.
3503
3504 There is one exception to the restriction on the use of &%-f%&: an empty sender
3505 can be specified by any user, trusted or not, to create a message that can
3506 never provoke a bounce. An empty sender can be specified either as an empty
3507 string, or as a pair of angle brackets with nothing between them, as in these
3508 examples of shell commands:
3509 .code
3510 exim -f '<>' user@domain
3511 exim -f "" user@domain
3512 .endd
3513 In addition, the use of &%-f%& is not restricted when testing a filter file
3514 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3515 &%-bv%& options.
3516
3517 Allowing untrusted users to change the sender address does not of itself make
3518 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3519 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3520 though this can be overridden by setting &%no_local_from_check%&.
3521
3522 White
3523 .cindex "&""From""& line"
3524 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3525 given as two arguments or one combined argument). The sender of a
3526 locally-generated message can also be set (when permitted) by an initial
3527 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3528 if &%-f%& is also present, it overrides &"From&~"&.
3529
3530 .vitem &%-G%&
3531 .oindex "&%-G%&"
3532 .cindex "Sendmail compatibility" "&%-G%& option ignored"
3533 This is a Sendmail option which is ignored by Exim.
3534
3535 .vitem &%-h%&&~<&'number'&>
3536 .oindex "&%-h%&"
3537 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3538 This option is accepted for compatibility with Sendmail, but has no effect. (In
3539 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3540 headers.)
3541
3542 .vitem &%-i%&
3543 .oindex "&%-i%&"
3544 .cindex "Solaris" "&'mail'& command"
3545 .cindex "dot" "in incoming non-SMTP message"
3546 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3547 line by itself should not terminate an incoming, non-SMTP message. I can find
3548 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3549 command in Solaris 2.4 uses it. See also &%-ti%&.
3550
3551 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3552 .oindex "&%-M%&"
3553 .cindex "forcing delivery"
3554 .cindex "delivery" "forcing attempt"
3555 .cindex "frozen messages" "forcing delivery"
3556 This option requests Exim to run a delivery attempt on each message in turn. If
3557 any of the messages are frozen, they are automatically thawed before the
3558 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3559 and &%hold_domains%& are ignored.
3560
3561 Retry
3562 .cindex "hints database" "overriding retry hints"
3563 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3564 the normal retry time has not yet been reached. This option requires the caller
3565 to be an admin user. However, there is an option called &%prod_requires_admin%&
3566 which can be set false to relax this restriction (and also the same requirement
3567 for the &%-q%&, &%-R%&, and &%-S%& options).
3568
3569 The deliveries happen synchronously, that is, the original Exim process does
3570 not terminate until all the delivery attempts have finished. No output is
3571 produced unless there is a serious error. If you want to see what is happening,
3572 use the &%-v%& option as well, or inspect Exim's main log.
3573
3574 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3575 .oindex "&%-Mar%&"
3576 .cindex "message" "adding recipients"
3577 .cindex "recipient" "adding"
3578 This option requests Exim to add the addresses to the list of recipients of the
3579 message (&"ar"& for &"add recipients"&). The first argument must be a message
3580 id, and the remaining ones must be email addresses. However, if the message is
3581 active (in the middle of a delivery attempt), it is not altered. This option
3582 can be used only by an admin user.
3583
3584 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3585 &~<&'message&~id'&>"
3586 .oindex "&%-MC%&"
3587 .cindex "SMTP" "passed connection"
3588 .cindex "SMTP" "multiple deliveries"
3589 .cindex "multiple SMTP deliveries"
3590 This option is not intended for use by external callers. It is used internally
3591 by Exim to invoke another instance of itself to deliver a waiting message using
3592 an existing SMTP connection, which is passed as the standard input. Details are
3593 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3594 must be root or the Exim user in order to use it.
3595
3596 .vitem &%-MCA%&
3597 .oindex "&%-MCA%&"
3598 This option is not intended for use by external callers. It is used internally
3599 by Exim in conjunction with the &%-MC%& option. It signifies that the
3600 connection to the remote host has been authenticated.
3601
3602 .vitem &%-MCP%&
3603 .oindex "&%-MCP%&"
3604 This option is not intended for use by external callers. It is used internally
3605 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3606 which Exim is connected supports pipelining.
3607
3608 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3609 .oindex "&%-MCQ%&"
3610 This option is not intended for use by external callers. It is used internally
3611 by Exim in conjunction with the &%-MC%& option when the original delivery was
3612 started by a queue runner. It passes on the process id of the queue runner,
3613 together with the file descriptor number of an open pipe. Closure of the pipe
3614 signals the final completion of the sequence of processes that are passing
3615 messages through the same SMTP connection.
3616
3617 .vitem &%-MCS%&
3618 .oindex "&%-MCS%&"
3619 This option is not intended for use by external callers. It is used internally
3620 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3621 SMTP SIZE option should be used on messages delivered down the existing
3622 connection.
3623
3624 .vitem &%-MCT%&
3625 .oindex "&%-MCT%&"
3626 This option is not intended for use by external callers. It is used internally
3627 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3628 host to which Exim is connected supports TLS encryption.
3629
3630 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3631 .oindex "&%-Mc%&"
3632 .cindex "hints database" "not overridden by &%-Mc%&"
3633 .cindex "delivery" "manually started &-- not forced"
3634 This option requests Exim to run a delivery attempt on each message in turn,
3635 but unlike the &%-M%& option, it does check for retry hints, and respects any
3636 that are found. This option is not very useful to external callers. It is
3637 provided mainly for internal use by Exim when it needs to re-invoke itself in
3638 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3639 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3640 respects retry times and other options such as &%hold_domains%& that are
3641 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3642 If you want to run a specific delivery as if in a queue run, you should use
3643 &%-q%& with a message id argument. A distinction between queue run deliveries
3644 and other deliveries is made in one or two places.
3645
3646 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3647 .oindex "&%-Mes%&"
3648 .cindex "message" "changing sender"
3649 .cindex "sender" "changing"
3650 This option requests Exim to change the sender address in the message to the
3651 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3652 &"edit sender"&). There must be exactly two arguments. The first argument must
3653 be a message id, and the second one an email address. However, if the message
3654 is active (in the middle of a delivery attempt), its status is not altered.
3655 This option can be used only by an admin user.
3656
3657 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3658 .oindex "&%-Mf%&"
3659 .cindex "freezing messages"
3660 .cindex "message" "manually freezing"
3661 This option requests Exim to mark each listed message as &"frozen"&. This
3662 prevents any delivery attempts taking place until the message is &"thawed"&,
3663 either manually or as a result of the &%auto_thaw%& configuration option.
3664 However, if any of the messages are active (in the middle of a delivery
3665 attempt), their status is not altered. This option can be used only by an admin
3666 user.
3667
3668 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3669 .oindex "&%-Mg%&"
3670 .cindex "giving up on messages"
3671 .cindex "message" "abandoning delivery attempts"
3672 .cindex "delivery" "abandoning further attempts"
3673 This option requests Exim to give up trying to deliver the listed messages,
3674 including any that are frozen. However, if any of the messages are active,
3675 their status is not altered. For non-bounce messages, a delivery error message
3676 is sent to the sender, containing the text &"cancelled by administrator"&.
3677 Bounce messages are just discarded. This option can be used only by an admin
3678 user.
3679
3680 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3681 .oindex "&%-Mmad%&"
3682 .cindex "delivery" "cancelling all"
3683 This option requests Exim to mark all the recipient addresses in the messages
3684 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
3685 message is active (in the middle of a delivery attempt), its status is not
3686 altered. This option can be used only by an admin user.
3687
3688 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3689 .oindex "&%-Mmd%&"
3690 .cindex "delivery" "cancelling by address"
3691 .cindex "recipient" "removing"
3692 .cindex "removing recipients"
3693 This option requests Exim to mark the given addresses as already delivered
3694 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
3695 the remaining ones must be email addresses. These are matched to recipient
3696 addresses in the message in a case-sensitive manner. If the message is active
3697 (in the middle of a delivery attempt), its status is not altered. This option
3698 can be used only by an admin user.
3699
3700 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3701 .oindex "&%-Mrm%&"
3702 .cindex "removing messages"
3703 .cindex "abandoning mail"
3704 .cindex "message" "manually discarding"
3705 This option requests Exim to remove the given messages from the queue. No
3706 bounce messages are sent; each message is simply forgotten. However, if any of
3707 the messages are active, their status is not altered. This option can be used
3708 only by an admin user or by the user who originally caused the message to be
3709 placed on the queue.
3710
3711 .vitem &%-Mset%&&~<&'message&~id'&>
3712 .oindex "&%-Mset%&
3713 .cindex "testing" "string expansion"
3714 .cindex "expansion" "testing"
3715 This option is useful only in conjunction with &%-be%& (that is, when testing
3716 string expansions). Exim loads the given message from its spool before doing
3717 the test expansions, thus setting message-specific variables such as
3718 &$message_size$& and the header variables. The &$recipients$& variable is made
3719 available. This feature is provided to make it easier to test expansions that
3720 make use of these variables. However, this option can be used only by an admin
3721 user. See also &%-bem%&.
3722
3723 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3724 .oindex "&%-Mt%&"
3725 .cindex "thawing messages"
3726 .cindex "unfreezing messages"
3727 .cindex "frozen messages" "thawing"
3728 .cindex "message" "thawing frozen"
3729 This option requests Exim to &"thaw"& any of the listed messages that are
3730 &"frozen"&, so that delivery attempts can resume. However, if any of the
3731 messages are active, their status is not altered. This option can be used only
3732 by an admin user.
3733
3734 .vitem &%-Mvb%&&~<&'message&~id'&>
3735 .oindex "&%-Mvb%&"
3736 .cindex "listing" "message body"
3737 .cindex "message" "listing body of"
3738 This option causes the contents of the message body (-D) spool file to be
3739 written to the standard output. This option can be used only by an admin user.
3740
3741 .vitem &%-Mvc%&&~<&'message&~id'&>
3742 .oindex "&%-Mvc%&"
3743 .cindex "message" "listing in RFC 2822 format"
3744 .cindex "listing" "message in RFC 2922 format"
3745 This option causes a copy of the complete message (header lines plus body) to
3746 be written to the standard output in RFC 2822 format. This option can be used
3747 only by an admin user.
3748
3749 .vitem &%-Mvh%&&~<&'message&~id'&>
3750 .oindex "&%-Mvh%&"
3751 .cindex "listing" "message headers"
3752 .cindex "header lines" "listing"
3753 .cindex "message" "listing header lines"
3754 This option causes the contents of the message headers (-H) spool file to be
3755 written to the standard output. This option can be used only by an admin user.
3756
3757 .vitem &%-Mvl%&&~<&'message&~id'&>
3758 .oindex "&%-Mvl%&"
3759 .cindex "listing" "message log"
3760 .cindex "message" "listing message log"
3761 This option causes the contents of the message log spool file to be written to
3762 the standard output. This option can be used only by an admin user.
3763
3764 .vitem &%-m%&
3765 .oindex "&%-m%&"
3766 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
3767 treats it that way too.
3768
3769 .vitem &%-N%&
3770 .oindex "&%-N%&"
3771 .cindex "debugging" "&%-N%& option"
3772 .cindex "debugging" "suppressing delivery"
3773 This is a debugging option that inhibits delivery of a message at the transport
3774 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
3775 it just doesn't actually transport the message, but instead behaves as if it
3776 had successfully done so. However, it does not make any updates to the retry
3777 database, and the log entries for deliveries are flagged with &"*>"& rather
3778 than &"=>"&.
3779
3780 Because &%-N%& discards any message to which it applies, only root or the Exim
3781 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
3782 words, an ordinary user can use it only when supplying an incoming message to
3783 which it will apply. Although transportation never fails when &%-N%& is set, an
3784 address may be deferred because of a configuration problem on a transport, or a
3785 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
3786 the message, and applies to any subsequent delivery attempts that may happen
3787 for that message.
3788
3789 .vitem &%-n%&
3790 .oindex "&%-n%&"
3791 .cindex "Sendmail compatibility" "&%-n%& option ignored"
3792 This option is interpreted by Sendmail to mean &"no aliasing"&. It is ignored
3793 by Exim.
3794
3795 .vitem &%-O%&&~<&'data'&>
3796 .oindex "&%-O%&"
3797 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
3798 Exim.
3799
3800 .vitem &%-oA%&&~<&'file&~name'&>
3801 .oindex "&%-oA%&"
3802 .cindex "Sendmail compatibility" "&%-oA%& option"
3803 This option is used by Sendmail in conjunction with &%-bi%& to specify an
3804 alternative alias file name. Exim handles &%-bi%& differently; see the
3805 description above.
3806
3807 .vitem &%-oB%&&~<&'n'&>
3808 .oindex "&%-oB%&"
3809 .cindex "SMTP" "passed connection"
3810 .cindex "SMTP" "multiple deliveries"
3811 .cindex "multiple SMTP deliveries"
3812 This is a debugging option which limits the maximum number of messages that can
3813 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
3814 transport. If <&'n'&> is omitted, the limit is set to 1.
3815
3816 .vitem &%-odb%&
3817 .oindex "&%-odb%&"
3818 .cindex "background delivery"
3819 .cindex "delivery" "in the background"
3820 This option applies to all modes in which Exim accepts incoming messages,
3821 including the listening daemon. It requests &"background"& delivery of such
3822 messages, which means that the accepting process automatically starts a
3823 delivery process for each message received, but does not wait for the delivery
3824 processes to finish.
3825
3826 When all the messages have been received, the reception process exits,
3827 leaving the delivery processes to finish in their own time. The standard output
3828 and error streams are closed at the start of each delivery process.
3829 This is the default action if none of the &%-od%& options are present.
3830
3831 If one of the queueing options in the configuration file
3832 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
3833 overrides it if &%queue_only_override%& is set true, which is the default
3834 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
3835
3836 .vitem &%-odf%&
3837 .oindex "&%-odf%&"
3838 .cindex "foreground delivery"
3839 .cindex "delivery" "in the foreground"
3840 This option requests &"foreground"& (synchronous) delivery when Exim has
3841 accepted a locally-generated message. (For the daemon it is exactly the same as
3842 &%-odb%&.) A delivery process is automatically started to deliver the message,
3843 and Exim waits for it to complete before proceeding.
3844
3845 The original Exim reception process does not finish until the delivery
3846 process for the final message has ended. The standard error stream is left open
3847 during deliveries.
3848
3849 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
3850 false and one of the queueing options in the configuration file is in effect.
3851
3852 If there is a temporary delivery error during foreground delivery, the
3853 message is left on the queue for later delivery, and the original reception
3854 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
3855 restricted configuration that never queues messages.
3856
3857
3858 .vitem &%-odi%&
3859 .oindex "&%-odi%&"
3860 This option is synonymous with &%-odf%&. It is provided for compatibility with
3861 Sendmail.
3862
3863 .vitem &%-odq%&
3864 .oindex "&%-odq%&"
3865 .cindex "non-immediate delivery"
3866 .cindex "delivery" "suppressing immediate"
3867 .cindex "queueing incoming messages"
3868 This option applies to all modes in which Exim accepts incoming messages,
3869 including the listening daemon. It specifies that the accepting process should
3870 not automatically start a delivery process for each message received. Messages
3871 are placed on the queue, and remain there until a subsequent queue runner
3872 process encounters them. There are several configuration options (such as
3873 &%queue_only%&) that can be used to queue incoming messages under certain
3874 conditions. This option overrides all of them and also &%-odqs%&. It always
3875 forces queueing.
3876
3877 .vitem &%-odqs%&
3878 .oindex "&%-odqs%&"
3879 .cindex "SMTP" "delaying delivery"
3880 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
3881 However, like &%-odb%& and &%-odi%&, this option has no effect if
3882 &%queue_only_override%& is false and one of the queueing options in the
3883 configuration file is in effect.
3884
3885 When &%-odqs%& does operate, a delivery process is started for each incoming
3886 message, in the background by default, but in the foreground if &%-odi%& is
3887 also present. The recipient addresses are routed, and local deliveries are done
3888 in the normal way. However, if any SMTP deliveries are required, they are not
3889 done at this time, so the message remains on the queue until a subsequent queue
3890 runner process encounters it. Because routing was done, Exim knows which
3891 messages are waiting for which hosts, and so a number of messages for the same
3892 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
3893 configuration option has the same effect for specific domains. See also the
3894 &%-qq%& option.
3895
3896 .vitem &%-oee%&
3897 .oindex "&%-oee%&"
3898 .cindex "error" "reporting"
3899 If an error is detected while a non-SMTP message is being received (for
3900 example, a malformed address), the error is reported to the sender in a mail
3901 message.
3902
3903 .cindex "return code" "for &%-oee%&"
3904 Provided
3905 this error message is successfully sent, the Exim receiving process
3906 exits with a return code of zero. If not, the return code is 2 if the problem
3907 is that the original message has no recipients, or 1 any other error. This is
3908 the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
3909
3910 .vitem &%-oem%&
3911 .oindex "&%-oem%&"
3912 .cindex "error" "reporting"
3913 .cindex "return code" "for &%-oem%&"
3914 This is the same as &%-oee%&, except that Exim always exits with a non-zero
3915 return code, whether or not the error message was successfully sent.
3916 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
3917
3918 .vitem &%-oep%&
3919 .oindex "&%-oep%&"
3920 .cindex "error" "reporting"
3921 If an error is detected while a non-SMTP message is being received, the
3922 error is reported by writing a message to the standard error file (stderr).
3923 .cindex "return code" "for &%-oep%&"
3924 The return code is 1 for all errors.
3925
3926 .vitem &%-oeq%&
3927 .oindex "&%-oeq%&"
3928 .cindex "error" "reporting"
3929 This option is supported for compatibility with Sendmail, but has the same
3930 effect as &%-oep%&.
3931
3932 .vitem &%-oew%&
3933 .oindex "&%-oew%&"
3934 .cindex "error" "reporting"
3935 This option is supported for compatibility with Sendmail, but has the same
3936 effect as &%-oem%&.
3937
3938 .vitem &%-oi%&
3939 .oindex "&%-oi%&"
3940 .cindex "dot" "in incoming non-SMTP message"
3941 This option, which has the same effect as &%-i%&, specifies that a dot on a
3942 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
3943 single dot does terminate, though Exim does no special processing for other
3944 lines that start with a dot. This option is set by default if Exim is called as
3945 &'rmail'&. See also &%-ti%&.
3946
3947 .vitem &%-oitrue%&
3948 .oindex "&%-oitrue%&"
3949 This option is treated as synonymous with &%-oi%&.
3950
3951 .vitem &%-oMa%&&~<&'host&~address'&>
3952 .oindex "&%-oMa%&"
3953 .cindex "sender" "host address, specifying for local message"
3954 A number of options starting with &%-oM%& can be used to set values associated
3955 with remote hosts on locally-submitted messages (that is, messages not received
3956 over TCP/IP). These options can be used by any caller in conjunction with the
3957 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
3958 other circumstances, they are ignored unless the caller is trusted.
3959
3960 The &%-oMa%& option sets the sender host address. This may include a port
3961 number at the end, after a full stop (period). For example:
3962 .code
3963 exim -bs -oMa 10.9.8.7.1234
3964 .endd
3965 An alternative syntax is to enclose the IP address in square brackets,
3966 followed by a colon and the port number:
3967 .code
3968 exim -bs -oMa [10.9.8.7]:1234
3969 .endd
3970 The IP address is placed in the &$sender_host_address$& variable, and the
3971 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
3972 are present on the command line, the sender host IP address is taken from
3973 whichever one is last.
3974
3975 .vitem &%-oMaa%&&~<&'name'&>
3976 .oindex "&%-oMaa%&"
3977 .cindex "authentication" "name, specifying for local message"
3978 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
3979 option sets the value of &$sender_host_authenticated$& (the authenticator
3980 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
3981 This option can be used with &%-bh%& and &%-bs%& to set up an
3982 authenticated SMTP session without actually using the SMTP AUTH command.
3983
3984 .vitem &%-oMai%&&~<&'string'&>
3985 .oindex "&%-oMai%&"
3986 .cindex "authentication" "id, specifying for local message"
3987 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
3988 option sets the value of &$authenticated_id$& (the id that was authenticated).
3989 This overrides the default value (the caller's login id, except with &%-bh%&,
3990 where there is no default) for messages from local sources. See chapter
3991 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
3992
3993 .vitem &%-oMas%&&~<&'address'&>
3994 .oindex "&%-oMas%&"
3995 .cindex "authentication" "sender, specifying for local message"
3996 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
3997 option sets the authenticated sender value in &$authenticated_sender$&. It
3998 overrides the sender address that is created from the caller's login id for
3999 messages from local sources, except when &%-bh%& is used, when there is no
4000 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4001 specified on a MAIL command overrides this value. See chapter
4002 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4003
4004 .vitem &%-oMi%&&~<&'interface&~address'&>
4005 .oindex "&%-oMi%&"
4006 .cindex "interface" "address, specifying for local message"
4007 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4008 option sets the IP interface address value. A port number may be included,
4009 using the same syntax as for &%-oMa%&. The interface address is placed in
4010 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4011
4012 .vitem &%-oMr%&&~<&'protocol&~name'&>
4013 .oindex "&%-oMr%&"
4014 .cindex "protocol, specifying for local message"
4015 .vindex "&$received_protocol$&"
4016 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4017 option sets the received protocol value that is stored in
4018 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4019 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4020 SMTP protocol names (see the description of &$received_protocol$& in section
4021 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4022 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4023 be set by &%-oMr%&.
4024
4025 .vitem &%-oMs%&&~<&'host&~name'&>
4026 .oindex "&%-oMs%&"
4027 .cindex "sender" "host name, specifying for local message"
4028 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4029 option sets the sender host name in &$sender_host_name$&. When this option is
4030 present, Exim does not attempt to look up a host name from an IP address; it
4031 uses the name it is given.
4032
4033 .vitem &%-oMt%&&~<&'ident&~string'&>
4034 .oindex "&%-oMt%&"
4035 .cindex "sender" "ident string, specifying for local message"
4036 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4037 option sets the sender ident value in &$sender_ident$&. The default setting for
4038 local callers is the login id of the calling process, except when &%-bh%& is
4039 used, when there is no default.
4040
4041 .vitem &%-om%&
4042 .oindex "&%-om%&"
4043 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4044 In Sendmail, this option means &"me too"&, indicating that the sender of a
4045 message should receive a copy of the message if the sender appears in an alias
4046 expansion. Exim always does this, so the option does nothing.
4047
4048 .vitem &%-oo%&
4049 .oindex "&%-oo%&"
4050 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4051 This option is ignored. In Sendmail it specifies &"old style headers"&,
4052 whatever that means.
4053
4054 .vitem &%-oP%&&~<&'path'&>
4055 .oindex "&%-oP%&"
4056 .cindex "pid (process id)" "of daemon"
4057 .cindex "daemon" "process id (pid)"
4058 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4059 value. The option specifies the file to which the process id of the daemon is
4060 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4061 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4062 because in those cases, the normal pid file is not used.
4063
4064 .vitem &%-or%&&~<&'time'&>
4065 .oindex "&%-or%&"
4066 .cindex "timeout" "for non-SMTP input"
4067 This option sets a timeout value for incoming non-SMTP messages. If it is not
4068 set, Exim will wait forever for the standard input. The value can also be set
4069 by the &%receive_timeout%& option. The format used for specifying times is
4070 described in section &<<SECTtimeformat>>&.
4071
4072 .vitem &%-os%&&~<&'time'&>
4073 .oindex "&%-os%&"
4074 .cindex "timeout" "for SMTP input"
4075 .cindex "SMTP" "input timeout"
4076 This option sets a timeout value for incoming SMTP messages. The timeout
4077 applies to each SMTP command and block of data. The value can also be set by
4078 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4079 for specifying times is described in section &<<SECTtimeformat>>&.
4080
4081 .vitem &%-ov%&
4082 .oindex "&%-ov%&"
4083 This option has exactly the same effect as &%-v%&.
4084
4085 .vitem &%-oX%&&~<&'number&~or&~string'&>
4086 .oindex "&%-oX%&"
4087 .cindex "TCP/IP" "setting listening ports"
4088 .cindex "TCP/IP" "setting listening interfaces"
4089 .cindex "port" "receiving TCP/IP"
4090 This option is relevant only when the &%-bd%& (start listening daemon) option
4091 is also given. It controls which ports and interfaces the daemon uses. Details
4092 of the syntax, and how it interacts with configuration file options, are given
4093 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4094 file is written unless &%-oP%& is also present to specify a pid file name.
4095
4096 .vitem &%-pd%&
4097 .oindex "&%-pd%&"
4098 .cindex "Perl" "starting the interpreter"
4099 This option applies when an embedded Perl interpreter is linked with Exim (see
4100 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4101 option, forcing the starting of the interpreter to be delayed until it is
4102 needed.
4103
4104 .vitem &%-ps%&
4105 .oindex "&%-ps%&"
4106 .cindex "Perl" "starting the interpreter"
4107 This option applies when an embedded Perl interpreter is linked with Exim (see
4108 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4109 option, forcing the starting of the interpreter to occur as soon as Exim is
4110 started.
4111
4112 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4113 .oindex "&%-p%&"
4114 For compatibility with Sendmail, this option is equivalent to
4115 .display
4116 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4117 .endd
4118 It sets the incoming protocol and host name (for trusted callers). The
4119 host name and its colon can be omitted when only the protocol is to be set.
4120 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4121 to embedded Perl. It is therefore impossible to set a protocol value of &`p`&
4122 or &`s`& using this option (but that does not seem a real limitation).
4123
4124 .vitem &%-q%&
4125 .oindex "&%-q%&"
4126 .cindex "queue runner" "starting manually"
4127 This option is normally restricted to admin users. However, there is a
4128 configuration option called &%prod_requires_admin%& which can be set false to
4129 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4130 and &%-S%& options).
4131
4132 .cindex "queue runner" "description of operation"
4133 The &%-q%& option starts one queue runner process. This scans the queue of
4134 waiting messages, and runs a delivery process for each one in turn. It waits
4135 for each delivery process to finish before starting the next one. A delivery
4136 process may not actually do any deliveries if the retry times for the addresses
4137 have not been reached. Use &%-qf%& (see below) if you want to override this.
4138
4139 If
4140 .cindex "SMTP" "passed connection"
4141 .cindex "SMTP" "multiple deliveries"
4142 .cindex "multiple SMTP deliveries"
4143 the delivery process spawns other processes to deliver other messages down
4144 passed SMTP connections, the queue runner waits for these to finish before
4145 proceeding.
4146
4147 When all the queued messages have been considered, the original queue runner
4148 process terminates. In other words, a single pass is made over the waiting
4149 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4150 this to be repeated periodically.
4151
4152 Exim processes the waiting messages in an unpredictable order. It isn't very
4153 random, but it is likely to be different each time, which is all that matters.
4154 If one particular message screws up a remote MTA, other messages to the same
4155 MTA have a chance of getting through if they get tried first.
4156
4157 It is possible to cause the messages to be processed in lexical message id
4158 order, which is essentially the order in which they arrived, by setting the
4159 &%queue_run_in_order%& option, but this is not recommended for normal use.
4160
4161 .vitem &%-q%&<&'qflags'&>
4162 The &%-q%& option may be followed by one or more flag letters that change its
4163 behaviour. They are all optional, but if more than one is present, they must
4164 appear in the correct order. Each flag is described in a separate item below.
4165
4166 .vitem &%-qq...%&
4167 .oindex "&%-qq%&"
4168 .cindex "queue" "double scanning"
4169 .cindex "queue" "routing"
4170 .cindex "routing" "whole queue before delivery"
4171 An option starting with &%-qq%& requests a two-stage queue run. In the first
4172 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4173 every domain. Addresses are routed, local deliveries happen, but no remote
4174 transports are run.
4175
4176 .cindex "hints database" "remembering routing"
4177 The hints database that remembers which messages are waiting for specific hosts
4178 is updated, as if delivery to those hosts had been deferred. After this is
4179 complete, a second, normal queue scan happens, with routing and delivery taking
4180 place as normal. Messages that are routed to the same host should mostly be
4181 delivered down a single SMTP
4182 .cindex "SMTP" "passed connection"
4183 .cindex "SMTP" "multiple deliveries"
4184 .cindex "multiple SMTP deliveries"
4185 connection because of the hints that were set up during the first queue scan.
4186 This option may be useful for hosts that are connected to the Internet
4187 intermittently.
4188
4189 .vitem &%-q[q]i...%&
4190 .oindex "&%-qi%&"
4191 .cindex "queue" "initial delivery"
4192 If the &'i'& flag is present, the queue runner runs delivery processes only for
4193 those messages that haven't previously been tried. (&'i'& stands for &"initial
4194 delivery"&.) This can be helpful if you are putting messages on the queue using
4195 &%-odq%& and want a queue runner just to process the new messages.
4196
4197 .vitem &%-q[q][i]f...%&
4198 .oindex "&%-qf%&"
4199 .cindex "queue" "forcing delivery"
4200 .cindex "delivery" "forcing in queue run"
4201 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4202 message, whereas without &'f'& only those non-frozen addresses that have passed
4203 their retry times are tried.
4204
4205 .vitem &%-q[q][i]ff...%&
4206 .oindex "&%-qff%&"
4207 .cindex "frozen messages" "forcing delivery"
4208 If &'ff'& is present, a delivery attempt is forced for every message, whether
4209 frozen or not.
4210
4211 .vitem &%-q[q][i][f[f]]l%&
4212 .oindex "&%-ql%&"
4213 .cindex "queue" "local deliveries only"
4214 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4215 be done. If a message requires any remote deliveries, it remains on the queue
4216 for later delivery.
4217
4218 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4219 .cindex "queue" "delivering specific messages"
4220 When scanning the queue, Exim can be made to skip over messages whose ids are
4221 lexically less than a given value by following the &%-q%& option with a
4222 starting message id. For example:
4223 .code
4224 exim -q 0t5C6f-0000c8-00
4225 .endd
4226 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4227 second message id is given, messages whose ids are lexically greater than it
4228 are also skipped. If the same id is given twice, for example,
4229 .code
4230 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4231 .endd
4232 just one delivery process is started, for that message. This differs from
4233 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4234 that it counts as a delivery from a queue run. Note that the selection
4235 mechanism does not affect the order in which the messages are scanned. There
4236 are also other ways of selecting specific sets of messages for delivery in a
4237 queue run &-- see &%-R%& and &%-S%&.
4238
4239 .vitem &%-q%&<&'qflags'&><&'time'&>
4240 .cindex "queue runner" "starting periodically"
4241 .cindex "periodic queue running"
4242 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4243 starting a queue runner process at intervals specified by the given time value
4244 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4245 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4246 single daemon process handles both functions. A common way of starting up a
4247 combined daemon at system boot time is to use a command such as
4248 .code
4249 /usr/exim/bin/exim -bd -q30m
4250 .endd
4251 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4252 process every 30 minutes.
4253
4254 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4255 pid file is written unless one is explicitly requested by the &%-oP%& option.
4256
4257 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4258 .oindex "&%-qR%&"
4259 This option is synonymous with &%-R%&. It is provided for Sendmail
4260 compatibility.
4261
4262 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4263 .oindex "&%-qS%&"
4264 This option is synonymous with &%-S%&.
4265
4266 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4267 .oindex "&%-R%&"
4268 .cindex "queue runner" "for specific recipients"
4269 .cindex "delivery" "to given domain"
4270 .cindex "domain" "delivery to"
4271 The <&'rsflags'&> may be empty, in which case the white space before the string
4272 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4273 which are the possible values for <&'rsflags'&>. White space is required if
4274 <&'rsflags'&> is not empty.
4275
4276 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4277 perform a single queue run, except that, when scanning the messages on the
4278 queue, Exim processes only those that have at least one undelivered recipient
4279 address containing the given string, which is checked in a case-independent
4280 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4281 regular expression; otherwise it is a literal string.
4282
4283 If you want to do periodic queue runs for messages with specific recipients,
4284 you can combine &%-R%& with &%-q%& and a time value. For example:
4285 .code
4286 exim -q25m -R @special.domain.example
4287 .endd
4288 This example does a queue run for messages with recipients in the given domain
4289 every 25 minutes. Any additional flags that are specified with &%-q%& are
4290 applied to each queue run.
4291
4292 Once a message is selected for delivery by this mechanism, all its addresses
4293 are processed. For the first selected message, Exim overrides any retry
4294 information and forces a delivery attempt for each undelivered address. This
4295 means that if delivery of any address in the first message is successful, any
4296 existing retry information is deleted, and so delivery attempts for that
4297 address in subsequently selected messages (which are processed without forcing)
4298 will run. However, if delivery of any address does not succeed, the retry
4299 information is updated, and in subsequently selected messages, the failing
4300 address will be skipped.
4301
4302 .cindex "frozen messages" "forcing delivery"
4303 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4304 all selected messages, not just the first; frozen messages are included when
4305 &'ff'& is present.
4306
4307 The &%-R%& option makes it straightforward to initiate delivery of all messages
4308 to a given domain after a host has been down for some time. When the SMTP
4309 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4310 effect is to run Exim with the &%-R%& option, but it can be configured to run
4311 an arbitrary command instead.
4312
4313 .vitem &%-r%&
4314 .oindex "&%-r%&"
4315 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4316
4317 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4318 .oindex "&%-S%&"
4319 .cindex "delivery" "from given sender"
4320 .cindex "queue runner" "for specific senders"
4321 This option acts like &%-R%& except that it checks the string against each
4322 message's sender instead of against the recipients. If &%-R%& is also set, both
4323 conditions must be met for a message to be selected. If either of the options
4324 has &'f'& or &'ff'& in its flags, the associated action is taken.
4325
4326 .vitem &%-Tqt%&&~<&'times'&>
4327 .oindex "&%-Tqt%&"
4328 This an option that is exclusively for use by the Exim testing suite. It is not
4329 recognized when Exim is run normally. It allows for the setting up of explicit
4330 &"queue times"& so that various warning/retry features can be tested.
4331
4332 .vitem &%-t%&
4333 .oindex "&%-t%&"
4334 .cindex "recipient" "extracting from header lines"
4335 .cindex "&'Bcc:'& header line"
4336 .cindex "&'Cc:'& header line"
4337 .cindex "&'To:'& header line"
4338 When Exim is receiving a locally-generated, non-SMTP message on its standard
4339 input, the &%-t%& option causes the recipients of the message to be obtained
4340 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4341 from the command arguments. The addresses are extracted before any rewriting
4342 takes place and the &'Bcc:'& header line, if present, is then removed.
4343
4344 .cindex "Sendmail compatibility" "&%-t%& option"
4345 If the command has any arguments, they specify addresses to which the message
4346 is &'not'& to be delivered. That is, the argument addresses are removed from
4347 the recipients list obtained from the headers. This is compatible with Smail 3
4348 and in accordance with the documented behaviour of several versions of
4349 Sendmail, as described in man pages on a number of operating systems (e.g.
4350 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4351 argument addresses to those obtained from the headers, and the O'Reilly
4352 Sendmail book documents it that way. Exim can be made to add argument addresses
4353 instead of subtracting them by setting the option
4354 &%extract_addresses_remove_arguments%& false.
4355
4356 .cindex "&%Resent-%& header lines" "with &%-t%&"
4357 If there are any &%Resent-%& header lines in the message, Exim extracts
4358 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4359 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4360 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4361 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4362
4363 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4364 message is resent several times). The RFC also specifies that they should be
4365 added at the front of the message, and separated by &'Received:'& lines. It is
4366 not at all clear how &%-t%& should operate in the present of multiple sets,
4367 nor indeed exactly what constitutes a &"set"&.
4368 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4369 are often added at the end of the header, and if a message is resent more than
4370 once, it is common for the original set of &%Resent-%& headers to be renamed as
4371 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4372
4373 .vitem &%-ti%&
4374 .oindex "&%-ti%&"
4375 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4376 compatibility with Sendmail.
4377
4378 .vitem &%-tls-on-connect%&
4379 .oindex "&%-tls-on-connect%&"
4380 .cindex "TLS" "use without STARTTLS"
4381 .cindex "TLS" "automatic start"
4382 This option is available when Exim is compiled with TLS support. It forces all
4383 incoming SMTP connections to behave as if the incoming port is listed in the
4384 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4385 &<<CHAPTLS>>& for further details.
4386
4387
4388 .vitem &%-U%&
4389 .oindex "&%-U%&"
4390 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4391 Sendmail uses this option for &"initial message submission"&, and its
4392 documentation states that in future releases, it may complain about
4393 syntactically invalid messages rather than fixing them when this flag is not
4394 set. Exim ignores this option.
4395
4396 .vitem &%-v%&
4397 .oindex "&%-v%&"
4398 This option causes Exim to write information to the standard error stream,
4399 describing what it is doing. In particular, it shows the log lines for
4400 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4401 dialogue is shown. Some of the log lines shown may not actually be written to
4402 the log if the setting of &%log_selector%& discards them. Any relevant
4403 selectors are shown with each log line. If none are shown, the logging is
4404 unconditional.
4405
4406 .vitem &%-x%&
4407 .oindex "&%-x%&"
4408 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4409 National Language Support extended characters in the body of the mail item"&).
4410 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4411 this option.
4412 .endlist
4413
4414 .ecindex IIDclo1
4415 .ecindex IIDclo2
4416
4417
4418 . ////////////////////////////////////////////////////////////////////////////
4419 . Insert a stylized DocBook comment here, to identify the end of the command
4420 . line options. This is for the benefit of the Perl script that automatically
4421 . creates a man page for the options.
4422 . ////////////////////////////////////////////////////////////////////////////
4423
4424 .literal xml
4425 <!-- === End of command line options === -->
4426 .literal off
4427
4428
4429
4430
4431
4432 . ////////////////////////////////////////////////////////////////////////////
4433 . ////////////////////////////////////////////////////////////////////////////
4434
4435
4436 .chapter "The Exim run time configuration file" "CHAPconf" &&&
4437 "The runtime configuration file"
4438
4439 .cindex "run time configuration"
4440 .cindex "configuration file" "general description"
4441 .cindex "CONFIGURE_FILE"
4442 .cindex "configuration file" "errors in"
4443 .cindex "error" "in configuration file"
4444 .cindex "return code" "for bad configuration"
4445 Exim uses a single run time configuration file that is read whenever an Exim
4446 binary is executed. Note that in normal operation, this happens frequently,
4447 because Exim is designed to operate in a distributed manner, without central
4448 control.
4449
4450 If a syntax error is detected while reading the configuration file, Exim
4451 writes a message on the standard error, and exits with a non-zero return code.
4452 The message is also written to the panic log. &*Note*&: Only simple syntax
4453 errors can be detected at this time. The values of any expanded options are
4454 not checked until the expansion happens, even when the expansion does not
4455 actually alter the string.
4456
4457 The name of the configuration file is compiled into the binary for security
4458 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4459 most configurations, this specifies a single file. However, it is permitted to
4460 give a colon-separated list of file names, in which case Exim uses the first
4461 existing file in the list.
4462
4463 .cindex "EXIM_USER"
4464 .cindex "EXIM_GROUP"
4465 .cindex "CONFIGURE_OWNER"
4466 .cindex "CONFIGURE_GROUP"
4467 .cindex "configuration file" "ownership"
4468 .cindex "ownership" "configuration file"
4469 The run time configuration file must be owned by root or by the user that is
4470 specified at compile time by the EXIM_USER option, or by the user that is
4471 specified at compile time by the CONFIGURE_OWNER option (if set). The
4472 configuration file must not be world-writeable or group-writeable, unless its
4473 group is the one specified at compile time by the EXIM_GROUP option or by the
4474 CONFIGURE_GROUP option.
4475
4476 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4477 to root, anybody who is able to edit the run time configuration file has an
4478 easy way to run commands as root. If you make your mail administrators members
4479 of the Exim group, but do not trust them with root, make sure that the run time
4480 configuration is not group writeable.
4481
4482 A default configuration file, which will work correctly in simple situations,
4483 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4484 defines just one file name, the installation process copies the default
4485 configuration to a new file of that name if it did not previously exist. If
4486 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4487 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4488 configuration.
4489
4490
4491
4492 .section "Using a different configuration file" "SECID40"
4493 .cindex "configuration file" "alternate"
4494 A one-off alternate configuration can be specified by the &%-C%& command line
4495 option, which may specify a single file or a list of files. However, when
4496 &%-C%& is used, Exim gives up its root privilege, unless called by root or the
4497 Exim user (or unless the argument for &%-C%& is identical to the built-in value
4498 from CONFIGURE_FILE). &%-C%& is useful mainly for checking the syntax of
4499 configuration files before installing them. No owner or group checks are done
4500 on a configuration file specified by &%-C%&.
4501
4502 The privileged use of &%-C%& by the Exim user can be locked out by setting
4503 ALT_CONFIG_ROOT_ONLY in &_Local/Makefile_& when building Exim. However,
4504 if you do this, you also lock out the possibility of testing a
4505 configuration using &%-C%& right through message reception and delivery, even
4506 if the caller is root. The reception works, but by that time, Exim is running
4507 as the Exim user, so when it re-execs to regain privilege for the delivery, the
4508 use of &%-C%& causes privilege to be lost. However, root can test reception and
4509 delivery using two separate commands (one to put a message on the queue, using
4510 &%-odq%&, and another to do the delivery, using &%-M%&).
4511
4512 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4513 prefix string with which any file named in a &%-C%& command line option must
4514 start. In addition, the file name must not contain the sequence &"&`/../`&"&.
4515 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any file
4516 name can be used with &%-C%&.
4517
4518 One-off changes to a configuration can be specified by the &%-D%& command line
4519 option, which defines and overrides values for macros used inside the
4520 configuration file. However, like &%-C%&, the use of this option by a
4521 non-privileged user causes Exim to discard its root privilege.
4522 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4523 completely disabled, and its use causes an immediate error exit.
4524
4525 Some sites may wish to use the same Exim binary on different machines that
4526 share a file system, but to use different configuration files on each machine.
4527 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4528 looks for a file whose name is the configuration file name followed by a dot
4529 and the machine's node name, as obtained from the &[uname()]& function. If this
4530 file does not exist, the standard name is tried. This processing occurs for
4531 each file name in the list given by CONFIGURE_FILE or &%-C%&.
4532
4533 In some esoteric situations different versions of Exim may be run under
4534 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4535 help with this. See the comments in &_src/EDITME_& for details.
4536
4537
4538
4539 .section "Configuration file format" "SECTconffilfor"
4540 .cindex "configuration file" "format of"
4541 .cindex "format" "configuration file"
4542 Exim's configuration file is divided into a number of different parts. General
4543 option settings must always appear at the start of the file. The other parts
4544 are all optional, and may appear in any order. Each part other than the first
4545 is introduced by the word &"begin"& followed by the name of the part. The
4546 optional parts are:
4547
4548 .ilist
4549 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
4550 &<<CHAPACL>>&).
4551 .next
4552 .cindex "AUTH" "configuration"
4553 &'authenticators'&: Configuration settings for the authenticator drivers. These
4554 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4555 .next
4556 &'routers'&: Configuration settings for the router drivers. Routers process
4557 addresses and determine how the message is to be delivered (see chapters
4558 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
4559 .next
4560 &'transports'&: Configuration settings for the transport drivers. Transports
4561 define mechanisms for copying messages to destinations (see chapters
4562 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
4563 .next
4564 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
4565 If there is no retry section, or if it is empty (that is, no retry rules are
4566 defined), Exim will not retry deliveries. In this situation, temporary errors
4567 are treated the same as permanent errors. Retry rules are discussed in chapter
4568 &<<CHAPretry>>&.
4569 .next
4570 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4571 when new addresses are generated during delivery. Rewriting is discussed in
4572 chapter &<<CHAPrewrite>>&.
4573 .next
4574 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4575 want to use this feature, you must set
4576 .code
4577 LOCAL_SCAN_HAS_OPTIONS=yes
4578 .endd
4579 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
4580 facility are given in chapter &<<CHAPlocalscan>>&.
4581 .endlist
4582
4583 .cindex "configuration file" "leading white space in"
4584 .cindex "configuration file" "trailing white space in"
4585 .cindex "white space" "in configuration file"
4586 Leading and trailing white space in configuration lines is always ignored.
4587
4588 Blank lines in the file, and lines starting with a # character (ignoring
4589 leading white space) are treated as comments and are ignored. &*Note*&: A
4590 # character other than at the beginning of a line is not treated specially,
4591 and does not introduce a comment.
4592
4593 Any non-comment line can be continued by ending it with a backslash. Note that
4594 the general rule for white space means that trailing white space after the
4595 backslash and leading white space at the start of continuation
4596 lines is ignored. Comment lines beginning with # (but not empty lines) may
4597 appear in the middle of a sequence of continuation lines.
4598
4599 A convenient way to create a configuration file is to start from the
4600 default, which is supplied in &_src/configure.default_&, and add, delete, or
4601 change settings as required.
4602
4603 The ACLs, retry rules, and rewriting rules have their own syntax which is
4604 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
4605 respectively. The other parts of the configuration file have some syntactic
4606 items in common, and these are described below, from section &<<SECTcos>>&
4607 onwards. Before that, the inclusion, macro, and conditional facilities are
4608 described.
4609
4610
4611
4612 .section "File inclusions in the configuration file" "SECID41"
4613 .cindex "inclusions in configuration file"
4614 .cindex "configuration file" "including other files"
4615 .cindex "&`.include`& in configuration file"
4616 .cindex "&`.include_if_exists`& in configuration file"
4617 You can include other files inside Exim's run time configuration file by
4618 using this syntax:
4619 .display
4620 &`.include`& <&'file name'&>
4621 &`.include_if_exists`& <&'file name'&>
4622 .endd
4623 on a line by itself. Double quotes round the file name are optional. If you use
4624 the first form, a configuration error occurs if the file does not exist; the
4625 second form does nothing for non-existent files. In all cases, an absolute file
4626 name is required.
4627
4628 Includes may be nested to any depth, but remember that Exim reads its
4629 configuration file often, so it is a good idea to keep them to a minimum.
4630 If you change the contents of an included file, you must HUP the daemon,
4631 because an included file is read only when the configuration itself is read.
4632
4633 The processing of inclusions happens early, at a physical line level, so, like
4634 comment lines, an inclusion can be used in the middle of an option setting,
4635 for example:
4636 .code
4637 hosts_lookup = a.b.c \
4638 .include /some/file
4639 .endd
4640 Include processing happens after macro processing (see below). Its effect is to
4641 process the lines of the included file as if they occurred inline where the
4642 inclusion appears.
4643
4644
4645
4646 .section "Macros in the configuration file" "SECTmacrodefs"
4647 .cindex "macro" "description of"
4648 .cindex "configuration file" "macros"
4649 If a line in the main part of the configuration (that is, before the first
4650 &"begin"& line) begins with an upper case letter, it is taken as a macro
4651 definition, and must be of the form
4652 .display
4653 <&'name'&> = <&'rest of line'&>
4654 .endd
4655 The name must consist of letters, digits, and underscores, and need not all be
4656 in upper case, though that is recommended. The rest of the line, including any
4657 continuations, is the replacement text, and has leading and trailing white
4658 space removed. Quotes are not removed. The replacement text can never end with
4659 a backslash character, but this doesn't seem to be a serious limitation.
4660
4661 Macros may also be defined between router, transport, authenticator, or ACL
4662 definitions. They may not, however, be defined within an individual driver or
4663 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
4664
4665 .section "Macro substitution" "SECID42"
4666 Once a macro is defined, all subsequent lines in the file (and any included
4667 files) are scanned for the macro name; if there are several macros, the line is
4668 scanned for each in turn, in the order in which the macros are defined. The
4669 replacement text is not re-scanned for the current macro, though it is scanned
4670 for subsequently defined macros. For this reason, a macro name may not contain
4671 the name of a previously defined macro as a substring. You could, for example,
4672 define
4673 .display
4674 &`ABCD_XYZ = `&<&'something'&>
4675 &`ABCD = `&<&'something else'&>
4676 .endd
4677 but putting the definitions in the opposite order would provoke a configuration
4678 error. Macro expansion is applied to individual physical lines from the file,
4679 before checking for line continuation or file inclusion (see above). If a line
4680 consists solely of a macro name, and the expansion of the macro is empty, the
4681 line is ignored. A macro at the start of a line may turn the line into a
4682 comment line or a &`.include`& line.
4683
4684
4685 .section "Redefining macros" "SECID43"
4686 Once defined, the value of a macro can be redefined later in the configuration
4687 (or in an included file). Redefinition is specified by using &'=='& instead of
4688 &'='&. For example:
4689 .code
4690 MAC = initial value
4691 ...
4692 MAC == updated value
4693 .endd
4694 Redefinition does not alter the order in which the macros are applied to the
4695 subsequent lines of the configuration file. It is still the same order in which
4696 the macros were originally defined. All that changes is the macro's value.
4697 Redefinition makes it possible to accumulate values. For example:
4698 .code
4699 MAC = initial value
4700 ...
4701 MAC == MAC and something added
4702 .endd
4703 This can be helpful in situations where the configuration file is built
4704 from a number of other files.
4705
4706 .section "Overriding macro values" "SECID44"
4707 The values set for macros in the configuration file can be overridden by the
4708 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
4709 used, unless called by root or the Exim user. A definition on the command line
4710 using the &%-D%& option causes all definitions and redefinitions within the
4711 file to be ignored.
4712
4713
4714
4715 .section "Example of macro usage" "SECID45"
4716 As an example of macro usage, consider a configuration where aliases are looked
4717 up in a MySQL database. It helps to keep the file less cluttered if long
4718 strings such as SQL statements are defined separately as macros, for example:
4719 .code
4720 ALIAS_QUERY = select mailbox from user where \
4721 login=${quote_mysql:$local_part};
4722 .endd
4723 This can then be used in a &(redirect)& router setting like this:
4724 .code
4725 data = ${lookup mysql{ALIAS_QUERY}}
4726 .endd
4727 In earlier versions of Exim macros were sometimes used for domain, host, or
4728 address lists. In Exim 4 these are handled better by named lists &-- see
4729 section &<<SECTnamedlists>>&.
4730
4731
4732 .section "Conditional skips in the configuration file" "SECID46"
4733 .cindex "configuration file" "conditional skips"
4734 .cindex "&`.ifdef`&"
4735 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
4736 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
4737 portions of the configuration file. The processing happens whenever the file is
4738 read (that is, when an Exim binary starts to run).
4739
4740 The implementation is very simple. Instances of the first four directives must
4741 be followed by text that includes the names of one or macros. The condition
4742 that is tested is whether or not any macro substitution has taken place in the
4743 line. Thus:
4744 .code
4745 .ifdef AAA
4746 message_size_limit = 50M
4747 .else
4748 message_size_limit = 100M
4749 .endif
4750 .endd
4751 sets a message size limit of 50M if the macro &`AAA`& is defined, and 100M
4752 otherwise. If there is more than one macro named on the line, the condition
4753 is true if any of them are defined. That is, it is an &"or"& condition. To
4754 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
4755
4756 Although you can use a macro expansion to generate one of these directives,
4757 it is not very useful, because the condition &"there was a macro substitution
4758 in this line"& will always be true.
4759
4760 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
4761 to clarify complicated nestings.
4762
4763
4764
4765 .section "Common option syntax" "SECTcos"
4766 .cindex "common option syntax"
4767 .cindex "syntax of common options"
4768 .cindex "configuration file" "common option syntax"
4769 For the main set of options, driver options, and &[local_scan()]& options,
4770 each setting is on a line by itself, and starts with a name consisting of
4771 lower-case letters and underscores. Many options require a data value, and in
4772 these cases the name must be followed by an equals sign (with optional white
4773 space) and then the value. For example:
4774 .code
4775 qualify_domain = mydomain.example.com
4776 .endd
4777 .cindex "hiding configuration option values"
4778 .cindex "configuration options" "hiding value of"
4779 .cindex "options" "hiding value of"
4780 Some option settings may contain sensitive data, for example, passwords for
4781 accessing databases. To stop non-admin users from using the &%-bP%& command
4782 line option to read these values, you can precede the option settings with the
4783 word &"hide"&. For example:
4784 .code
4785 hide mysql_servers = localhost/users/admin/secret-password
4786 .endd
4787 For non-admin users, such options are displayed like this:
4788 .code
4789 mysql_servers = <value not displayable>
4790 .endd
4791 If &"hide"& is used on a driver option, it hides the value of that option on
4792 all instances of the same driver.
4793
4794 The following sections describe the syntax used for the different data types
4795 that are found in option settings.
4796
4797
4798 .section "Boolean options" "SECID47"
4799 .cindex "format" "boolean"
4800 .cindex "boolean configuration values"
4801 .oindex "&%no_%&&'xxx'&"
4802 .oindex "&%not_%&&'xxx'&"
4803 Options whose type is given as boolean are on/off switches. There are two
4804 different ways of specifying such options: with and without a data value. If
4805 the option name is specified on its own without data, the switch is turned on;
4806 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
4807 boolean options may be followed by an equals sign and one of the words
4808 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
4809 the following two settings have exactly the same effect:
4810 .code
4811 queue_only
4812 queue_only = true
4813 .endd
4814 The following two lines also have the same (opposite) effect:
4815 .code
4816 no_queue_only
4817 queue_only = false
4818 .endd
4819 You can use whichever syntax you prefer.
4820
4821
4822
4823
4824 .section "Integer values" "SECID48"
4825 .cindex "integer configuration values"
4826 .cindex "format" "integer"
4827 If an option's type is given as &"integer"&, the value can be given in decimal,
4828 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
4829 number is assumed. Otherwise, it is treated as an octal number unless it starts
4830 with the characters &"0x"&, in which case the remainder is interpreted as a
4831 hexadecimal number.
4832
4833 If an integer value is followed by the letter K, it is multiplied by 1024; if
4834 it is followed by the letter M, it is multiplied by 1024x1024. When the values
4835 of integer option settings are output, values which are an exact multiple of
4836 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
4837 and M. The printing style is independent of the actual input format that was
4838 used.
4839
4840
4841 .section "Octal integer values" "SECID49"
4842 .cindex "integer format"
4843 .cindex "format" "octal integer"
4844 If an option's type is given as &"octal integer"&, its value is always
4845 interpreted as an octal number, whether or not it starts with the digit zero.
4846 Such options are always output in octal.
4847
4848
4849 .section "Fixed point numbers" "SECID50"
4850 .cindex "fixed point configuration values"
4851 .cindex "format" "fixed point"
4852 If an option's type is given as &"fixed-point"&, its value must be a decimal
4853 integer, optionally followed by a decimal point and up to three further digits.
4854
4855
4856
4857 .section "Time intervals" "SECTtimeformat"
4858 .cindex "time interval" "specifying in configuration"
4859 .cindex "format" "time interval"
4860 A time interval is specified as a sequence of numbers, each followed by one of
4861 the following letters, with no intervening white space:
4862
4863 .table2 30pt
4864 .irow &%s%& seconds
4865 .irow &%m%& minutes
4866 .irow &%h%& hours
4867 .irow &%d%& days
4868 .irow &%w%& weeks
4869 .endtable
4870
4871 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
4872 intervals are output in the same format. Exim does not restrict the values; it
4873 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
4874
4875
4876
4877 .section "String values" "SECTstrings"
4878 .cindex "string" "format of configuration values"
4879 .cindex "format" "string"
4880 If an option's type is specified as &"string"&, the value can be specified with
4881 or without double-quotes. If it does not start with a double-quote, the value
4882 consists of the remainder of the line plus any continuation lines, starting at
4883 the first character after any leading white space, with trailing white space
4884 removed, and with no interpretation of the characters in the string. Because
4885 Exim removes comment lines (those beginning with #) at an early stage, they can
4886 appear in the middle of a multi-line string. The following two settings are
4887 therefore equivalent:
4888 .code
4889 trusted_users = uucp:mail
4890 trusted_users = uucp:\
4891 # This comment line is ignored
4892 mail
4893 .endd
4894 .cindex "string" "quoted"
4895 .cindex "escape characters in quoted strings"
4896 If a string does start with a double-quote, it must end with a closing
4897 double-quote, and any backslash characters other than those used for line
4898 continuation are interpreted as escape characters, as follows:
4899
4900 .table2 100pt
4901 .irow &`\\`& "single backslash"
4902 .irow &`\n`& "newline"
4903 .irow &`\r`& "carriage return"
4904 .irow &`\t`& "tab"
4905 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
4906 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
4907 character"
4908 .endtable
4909
4910 If a backslash is followed by some other character, including a double-quote
4911 character, that character replaces the pair.
4912
4913 Quoting is necessary only if you want to make use of the backslash escapes to
4914 insert special characters, or if you need to specify a value with leading or
4915 trailing spaces. These cases are rare, so quoting is almost never needed in
4916 current versions of Exim. In versions of Exim before 3.14, quoting was required
4917 in order to continue lines, so you may come across older configuration files
4918 and examples that apparently quote unnecessarily.
4919
4920
4921 .section "Expanded strings" "SECID51"
4922 .cindex "expansion" "definition of"
4923 Some strings in the configuration file are subjected to &'string expansion'&,
4924 by which means various parts of the string may be changed according to the
4925 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
4926 is as just described; in particular, the handling of backslashes in quoted
4927 strings is done as part of the input process, before expansion takes place.
4928 However, backslash is also an escape character for the expander, so any
4929 backslashes that are required for that reason must be doubled if they are
4930 within a quoted configuration string.
4931
4932
4933 .section "User and group names" "SECID52"
4934 .cindex "user name" "format of"
4935 .cindex "format" "user name"
4936 .cindex "groups" "name format"
4937 .cindex "format" "group name"
4938 User and group names are specified as strings, using the syntax described
4939 above, but the strings are interpreted specially. A user or group name must
4940 either consist entirely of digits, or be a name that can be looked up using the
4941 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
4942
4943
4944 .section "List construction" "SECTlistconstruct"
4945 .cindex "list" "syntax of in configuration"
4946 .cindex "format" "list item in configuration"
4947 .cindex "string" "list, definition of"
4948 The data for some configuration options is a list of items, with colon as the
4949 default separator. Many of these options are shown with type &"string list"& in
4950 the descriptions later in this document. Others are listed as &"domain list"&,
4951 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
4952 are all the same; however, those other than &"string list"& are subject to
4953 particular kinds of interpretation, as described in chapter
4954 &<<CHAPdomhosaddlists>>&.
4955
4956 In all these cases, the entire list is treated as a single string as far as the
4957 input syntax is concerned. The &%trusted_users%& setting in section
4958 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
4959 in a list, it must be entered as two colons. Leading and trailing white space
4960 on each item in a list is ignored. This makes it possible to include items that
4961 start with a colon, and in particular, certain forms of IPv6 address. For
4962 example, the list
4963 .code
4964 local_interfaces = 127.0.0.1 : ::::1
4965 .endd
4966 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
4967
4968 &*Note*&: Although leading and trailing white space is ignored in individual
4969 list items, it is not ignored when parsing the list. The space after the first
4970 colon in the example above is necessary. If it were not there, the list would
4971 be interpreted as the two items 127.0.0.1:: and 1.
4972
4973 .section "Changing list separators" "SECID53"
4974 .cindex "list separator" "changing"
4975 .cindex "IPv6" "addresses in lists"
4976 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
4977 introduced to allow the separator character to be changed. If a list begins
4978 with a left angle bracket, followed by any punctuation character, that
4979 character is used instead of colon as the list separator. For example, the list
4980 above can be rewritten to use a semicolon separator like this:
4981 .code
4982 local_interfaces = <; 127.0.0.1 ; ::1
4983 .endd
4984 This facility applies to all lists, with the exception of the list in
4985 &%log_file_path%&. It is recommended that the use of non-colon separators be
4986 confined to circumstances where they really are needed.
4987
4988 .cindex "list separator" "newline as"
4989 .cindex "newline" "as list separator"
4990 It is also possible to use newline and other control characters (those with
4991 code values less than 32, plus DEL) as separators in lists. Such separators
4992 must be provided literally at the time the list is processed. For options that
4993 are string-expanded, you can write the separator using a normal escape
4994 sequence. This will be processed by the expander before the string is
4995 interpreted as a list. For example, if a newline-separated list of domains is
4996 generated by a lookup, you can process it directly by a line such as this:
4997 .code
4998 domains = <\n ${lookup mysql{.....}}
4999 .endd
5000 This avoids having to change the list separator in such data. You are unlikely
5001 to want to use a control character as a separator in an option that is not
5002 expanded, because the value is literal text. However, it can be done by giving
5003 the value in quotes. For example:
5004 .code
5005 local_interfaces = "<\n 127.0.0.1 \n ::1"
5006 .endd
5007 Unlike printing character separators, which can be included in list items by
5008 doubling, it is not possible to include a control character as data when it is
5009 set as the separator. Two such characters in succession are interpreted as
5010 enclosing an empty list item.
5011
5012
5013
5014 .section "Empty items in lists" "SECTempitelis"
5015 .cindex "list" "empty item in"
5016 An empty item at the end of a list is always ignored. In other words, trailing
5017 separator characters are ignored. Thus, the list in
5018 .code
5019 senders = user@domain :
5020 .endd
5021 contains only a single item. If you want to include an empty string as one item
5022 in a list, it must not be the last item. For example, this list contains three
5023 items, the second of which is empty:
5024 .code
5025 senders = user1@domain : : user2@domain
5026 .endd
5027 &*Note*&: There must be white space between the two colons, as otherwise they
5028 are interpreted as representing a single colon data character (and the list
5029 would then contain just one item). If you want to specify a list that contains
5030 just one, empty item, you can do it as in this example:
5031 .code
5032 senders = :
5033 .endd
5034 In this case, the first item is empty, and the second is discarded because it
5035 is at the end of the list.
5036
5037
5038
5039
5040 .section "Format of driver configurations" "SECTfordricon"
5041 .cindex "drivers" "configuration format"
5042 There are separate parts in the configuration for defining routers, transports,
5043 and authenticators. In each part, you are defining a number of driver
5044 instances, each with its own set of options. Each driver instance is defined by
5045 a sequence of lines like this:
5046 .display
5047 <&'instance name'&>:
5048 <&'option'&>
5049 ...
5050 <&'option'&>
5051 .endd
5052 In the following example, the instance name is &(localuser)&, and it is
5053 followed by three options settings:
5054 .code
5055 localuser:
5056 driver = accept
5057 check_local_user
5058 transport = local_delivery
5059 .endd
5060 For each driver instance, you specify which Exim code module it uses &-- by the
5061 setting of the &%driver%& option &-- and (optionally) some configuration
5062 settings. For example, in the case of transports, if you want a transport to
5063 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5064 a local file you would use the &(appendfile)& driver. Each of the drivers is
5065 described in detail in its own separate chapter later in this manual.
5066
5067 You can have several routers, transports, or authenticators that are based on
5068 the same underlying driver (each must have a different instance name).
5069
5070 The order in which routers are defined is important, because addresses are
5071 passed to individual routers one by one, in order. The order in which
5072 transports are defined does not matter at all. The order in which
5073 authenticators are defined is used only when Exim, as a client, is searching
5074 them to find one that matches an authentication mechanism offered by the
5075 server.
5076
5077 .cindex "generic options"
5078 .cindex "options" "generic &-- definition of"
5079 Within a driver instance definition, there are two kinds of option: &'generic'&
5080 and &'private'&. The generic options are those that apply to all drivers of the
5081 same type (that is, all routers, all transports or all authenticators). The
5082 &%driver%& option is a generic option that must appear in every definition.
5083 .cindex "private options"
5084 The private options are special for each driver, and none need appear, because
5085 they all have default values.
5086
5087 The options may appear in any order, except that the &%driver%& option must
5088 precede any private options, since these depend on the particular driver. For
5089 this reason, it is recommended that &%driver%& always be the first option.
5090
5091 Driver instance names, which are used for reference in log entries and
5092 elsewhere, can be any sequence of letters, digits, and underscores (starting
5093 with a letter) and must be unique among drivers of the same type. A router and
5094 a transport (for example) can each have the same name, but no two router
5095 instances can have the same name. The name of a driver instance should not be
5096 confused with the name of the underlying driver module. For example, the
5097 configuration lines:
5098 .code
5099 remote_smtp:
5100 driver = smtp
5101 .endd
5102 create an instance of the &(smtp)& transport driver whose name is
5103 &(remote_smtp)&. The same driver code can be used more than once, with
5104 different instance names and different option settings each time. A second
5105 instance of the &(smtp)& transport, with different options, might be defined
5106 thus:
5107 .code
5108 special_smtp:
5109 driver = smtp
5110 port = 1234
5111 command_timeout = 10s
5112 .endd
5113 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5114 these transport instances from routers, and these names would appear in log
5115 lines.
5116
5117 Comment lines may be present in the middle of driver specifications. The full
5118 list of option settings for any particular driver instance, including all the
5119 defaulted values, can be extracted by making use of the &%-bP%& command line
5120 option.
5121
5122
5123
5124
5125
5126
5127 . ////////////////////////////////////////////////////////////////////////////
5128 . ////////////////////////////////////////////////////////////////////////////
5129
5130 .chapter "The default configuration file" "CHAPdefconfil"
5131 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5132 .cindex "default" "configuration file &""walk through""&"
5133 The default configuration file supplied with Exim as &_src/configure.default_&
5134 is sufficient for a host with simple mail requirements. As an introduction to
5135 the way Exim is configured, this chapter &"walks through"& the default
5136 configuration, giving brief explanations of the settings. Detailed descriptions
5137 of the options are given in subsequent chapters. The default configuration file
5138 itself contains extensive comments about ways you might want to modify the
5139 initial settings. However, note that there are many options that are not
5140 mentioned at all in the default configuration.
5141
5142
5143
5144 .section "Main configuration settings" "SECTdefconfmain"
5145 The main (global) configuration option settings must always come first in the
5146 file. The first thing you'll see in the file, after some initial comments, is
5147 the line
5148 .code
5149 # primary_hostname =
5150 .endd
5151 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5152 to know the official, fully qualified name of your host, and this is where you
5153 can specify it. However, in most cases you do not need to set this option. When
5154 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5155
5156 The first three non-comment configuration lines are as follows:
5157 .code
5158 domainlist local_domains = @
5159 domainlist relay_to_domains =
5160 hostlist relay_from_hosts = 127.0.0.1
5161 .endd
5162 These are not, in fact, option settings. They are definitions of two named
5163 domain lists and one named host list. Exim allows you to give names to lists of
5164 domains, hosts, and email addresses, in order to make it easier to manage the
5165 configuration file (see section &<<SECTnamedlists>>&).
5166
5167 The first line defines a domain list called &'local_domains'&; this is used
5168 later in the configuration to identify domains that are to be delivered
5169 on the local host.
5170
5171 .cindex "@ in a domain list"
5172 There is just one item in this list, the string &"@"&. This is a special form
5173 of entry which means &"the name of the local host"&. Thus, if the local host is
5174 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5175 be delivered locally. Because the local host's name is referenced indirectly,
5176 the same configuration file can be used on different hosts.
5177
5178 The second line defines a domain list called &'relay_to_domains'&, but the
5179 list itself is empty. Later in the configuration we will come to the part that
5180 controls mail relaying through the local host; it allows relaying to any
5181 domains in this list. By default, therefore, no relaying on the basis of a mail
5182 domain is permitted.
5183
5184 The third line defines a host list called &'relay_from_hosts'&. This list is
5185 used later in the configuration to permit relaying from any host or IP address
5186 that matches the list. The default contains just the IP address of the IPv4
5187 loopback interface, which means that processes on the local host are able to
5188 submit mail for relaying by sending it over TCP/IP to that interface. No other
5189 hosts are permitted to submit messages for relaying.
5190
5191 Just to be sure there's no misunderstanding: at this point in the configuration
5192 we aren't actually setting up any controls. We are just defining some domains
5193 and hosts that will be used in the controls that are specified later.
5194
5195 The next two configuration lines are genuine option settings:
5196 .code
5197 acl_smtp_rcpt = acl_check_rcpt
5198 acl_smtp_data = acl_check_data
5199 .endd
5200 These options specify &'Access Control Lists'& (ACLs) that are to be used
5201 during an incoming SMTP session for every recipient of a message (every RCPT
5202 command), and after the contents of the message have been received,
5203 respectively. The names of the lists are &'acl_check_rcpt'& and
5204 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5205 section of the configuration. The RCPT ACL controls which recipients are
5206 accepted for an incoming message &-- if a configuration does not provide an ACL
5207 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5208 contents of a message to be checked.
5209
5210 Two commented-out option settings are next:
5211 .code
5212 # av_scanner = clamd:/tmp/clamd
5213 # spamd_address = 127.0.0.1 783
5214 .endd
5215 These are example settings that can be used when Exim is compiled with the
5216 content-scanning extension. The first specifies the interface to the virus
5217 scanner, and the second specifies the interface to SpamAssassin. Further
5218 details are given in chapter &<<CHAPexiscan>>&.
5219
5220 Three more commented-out option settings follow:
5221 .code
5222 # tls_advertise_hosts = *
5223 # tls_certificate = /etc/ssl/exim.crt
5224 # tls_privatekey = /etc/ssl/exim.pem
5225 .endd
5226 These are example settings that can be used when Exim is compiled with
5227 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5228 first one specifies the list of clients that are allowed to use TLS when
5229 connecting to this server; in this case the wildcard means all clients. The
5230 other options specify where Exim should find its TLS certificate and private
5231 key, which together prove the server's identity to any clients that connect.
5232 More details are given in chapter &<<CHAPTLS>>&.
5233
5234 Another two commented-out option settings follow:
5235 .code
5236 # daemon_smtp_ports = 25 : 465 : 587
5237 # tls_on_connect_ports = 465
5238 .endd
5239 .cindex "port" "465 and 587"
5240 .cindex "port" "for message submission"
5241 .cindex "message" "submission, ports for"
5242 .cindex "ssmtp protocol"
5243 .cindex "smtps protocol"
5244 .cindex "SMTP" "ssmtp protocol"
5245 .cindex "SMTP" "smtps protocol"
5246 These options provide better support for roaming users who wish to use this
5247 server for message submission. They are not much use unless you have turned on
5248 TLS (as described in the previous paragraph) and authentication (about which
5249 more in section &<<SECTdefconfauth>>&). The usual SMTP port 25 is often blocked
5250 on end-user networks, so RFC 4409 specifies that message submission should use
5251 port 587 instead. However some software (notably Microsoft Outlook) cannot be
5252 configured to use port 587 correctly, so these settings also enable the
5253 non-standard &"smtps"& (aka &"ssmtp"&) port 465 (see section
5254 &<<SECTsupobssmt>>&).
5255
5256 Two more commented-out options settings follow:
5257 .code
5258 # qualify_domain =
5259 # qualify_recipient =
5260 .endd
5261 The first of these specifies a domain that Exim uses when it constructs a
5262 complete email address from a local login name. This is often needed when Exim
5263 receives a message from a local process. If you do not set &%qualify_domain%&,
5264 the value of &%primary_hostname%& is used. If you set both of these options,
5265 you can have different qualification domains for sender and recipient
5266 addresses. If you set only the first one, its value is used in both cases.
5267
5268 .cindex "domain literal" "recognizing format"
5269 The following line must be uncommented if you want Exim to recognize
5270 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5271 (an IP address within square brackets) instead of a named domain.
5272 .code
5273 # allow_domain_literals
5274 .endd
5275 The RFCs still require this form, but many people think that in the modern
5276 Internet it makes little sense to permit mail to be sent to specific hosts by
5277 quoting their IP addresses. This ancient format has been used by people who
5278 try to abuse hosts by using them for unwanted relaying. However, some
5279 people believe there are circumstances (for example, messages addressed to
5280 &'postmaster'&) where domain literals are still useful.
5281
5282 The next configuration line is a kind of trigger guard:
5283 .code
5284 never_users = root
5285 .endd
5286 It specifies that no delivery must ever be run as the root user. The normal
5287 convention is to set up &'root'& as an alias for the system administrator. This
5288 setting is a guard against slips in the configuration.
5289 The list of users specified by &%never_users%& is not, however, the complete
5290 list; the build-time configuration in &_Local/Makefile_& has an option called
5291 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5292 contents of &%never_users%& are added to this list. By default
5293 FIXED_NEVER_USERS also specifies root.
5294
5295 When a remote host connects to Exim in order to send mail, the only information
5296 Exim has about the host's identity is its IP address. The next configuration
5297 line,
5298 .code
5299 host_lookup = *
5300 .endd
5301 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5302 in order to get a host name. This improves the quality of the logging
5303 information, but if you feel it is too expensive, you can remove it entirely,
5304 or restrict the lookup to hosts on &"nearby"& networks.
5305 Note that it is not always possible to find a host name from an IP address,
5306 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5307 unreachable.
5308
5309 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5310 1413 (hence their names):
5311 .code
5312 rfc1413_hosts = *
5313 rfc1413_query_timeout = 5s
5314 .endd
5315 These settings cause Exim to make ident callbacks for all incoming SMTP calls.
5316 You can limit the hosts to which these calls are made, or change the timeout
5317 that is used. If you set the timeout to zero, all ident calls are disabled.
5318 Although they are cheap and can provide useful information for tracing problem
5319 messages, some hosts and firewalls have problems with ident calls. This can
5320 result in a timeout instead of an immediate refused connection, leading to
5321 delays on starting up an incoming SMTP session.
5322
5323 When Exim receives messages over SMTP connections, it expects all addresses to
5324 be fully qualified with a domain, as required by the SMTP definition. However,
5325 if you are running a server to which simple clients submit messages, you may
5326 find that they send unqualified addresses. The two commented-out options:
5327 .code
5328 # sender_unqualified_hosts =
5329 # recipient_unqualified_hosts =
5330 .endd
5331 show how you can specify hosts that are permitted to send unqualified sender
5332 and recipient addresses, respectively.
5333
5334 The &%percent_hack_domains%& option is also commented out:
5335 .code
5336 # percent_hack_domains =
5337 .endd
5338 It provides a list of domains for which the &"percent hack"& is to operate.
5339 This is an almost obsolete form of explicit email routing. If you do not know
5340 anything about it, you can safely ignore this topic.
5341
5342 The last two settings in the main part of the default configuration are
5343 concerned with messages that have been &"frozen"& on Exim's queue. When a
5344 message is frozen, Exim no longer continues to try to deliver it. Freezing
5345 occurs when a bounce message encounters a permanent failure because the sender
5346 address of the original message that caused the bounce is invalid, so the
5347 bounce cannot be delivered. This is probably the most common case, but there
5348 are also other conditions that cause freezing, and frozen messages are not
5349 always bounce messages.
5350 .code
5351 ignore_bounce_errors_after = 2d
5352 timeout_frozen_after = 7d
5353 .endd
5354 The first of these options specifies that failing bounce messages are to be
5355 discarded after 2 days on the queue. The second specifies that any frozen
5356 message (whether a bounce message or not) is to be timed out (and discarded)
5357 after a week. In this configuration, the first setting ensures that no failing
5358 bounce message ever lasts a week.
5359
5360
5361
5362 .section "ACL configuration" "SECID54"
5363 .cindex "default" "ACLs"
5364 .cindex "&ACL;" "default configuration"
5365 In the default configuration, the ACL section follows the main configuration.
5366 It starts with the line
5367 .code
5368 begin acl
5369 .endd
5370 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5371 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5372 and &%acl_smtp_data%& above.
5373
5374 .cindex "RCPT" "ACL for"
5375 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5376 RCPT command specifies one of the message's recipients. The ACL statements
5377 are considered in order, until the recipient address is either accepted or
5378 rejected. The RCPT command is then accepted or rejected, according to the
5379 result of the ACL processing.
5380 .code
5381 acl_check_rcpt:
5382 .endd
5383 This line, consisting of a name terminated by a colon, marks the start of the
5384 ACL, and names it.
5385 .code
5386 accept hosts = :
5387 .endd
5388 This ACL statement accepts the recipient if the sending host matches the list.
5389 But what does that strange list mean? It doesn't actually contain any host
5390 names or IP addresses. The presence of the colon puts an empty item in the
5391 list; Exim matches this only if the incoming message did not come from a remote
5392 host, because in that case, the remote hostname is empty. The colon is
5393 important. Without it, the list itself is empty, and can never match anything.
5394
5395 What this statement is doing is to accept unconditionally all recipients in
5396 messages that are submitted by SMTP from local processes using the standard
5397 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5398 manner.
5399 .code
5400 deny message = Restricted characters in address
5401 domains = +local_domains
5402 local_parts = ^[.] : ^.*[@%!/|]
5403
5404 deny message = Restricted characters in address
5405 domains = !+local_domains
5406 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5407 .endd
5408 These statements are concerned with local parts that contain any of the
5409 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5410 Although these characters are entirely legal in local parts (in the case of
5411 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5412 in Internet mail addresses.
5413
5414 The first three have in the past been associated with explicitly routed
5415 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5416 option). Addresses containing these characters are regularly tried by spammers
5417 in an attempt to bypass relaying restrictions, and also by open relay testing
5418 programs. Unless you really need them it is safest to reject these characters
5419 at this early stage. This configuration is heavy-handed in rejecting these
5420 characters for all messages it accepts from remote hosts. This is a deliberate
5421 policy of being as safe as possible.
5422
5423 The first rule above is stricter, and is applied to messages that are addressed
5424 to one of the local domains handled by this host. This is implemented by the
5425 first condition, which restricts it to domains that are listed in the
5426 &'local_domains'& domain list. The &"+"& character is used to indicate a
5427 reference to a named list. In this configuration, there is just one domain in
5428 &'local_domains'&, but in general there may be many.
5429
5430 The second condition on the first statement uses two regular expressions to
5431 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5432 or &"|"&. If you have local accounts that include these characters, you will
5433 have to modify this rule.
5434
5435 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5436 allows them because they have been encountered in practice. (Consider the
5437 common convention of local parts constructed as
5438 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5439 the author of Exim, who has no second initial.) However, a local part starting
5440 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5441 file name (for example, for a mailing list). This is also true for local parts
5442 that contain slashes. A pipe symbol can also be troublesome if the local part
5443 is incorporated unthinkingly into a shell command line.
5444
5445 The second rule above applies to all other domains, and is less strict. This
5446 allows your own users to send outgoing messages to sites that use slashes
5447 and vertical bars in their local parts. It blocks local parts that begin
5448 with a dot, slash, or vertical bar, but allows these characters within the
5449 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5450 and &"!"& is blocked, as before. The motivation here is to prevent your users
5451 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5452 .code
5453 accept local_parts = postmaster
5454 domains = +local_domains
5455 .endd
5456 This statement, which has two conditions, accepts an incoming address if the
5457 local part is &'postmaster'& and the domain is one of those listed in the
5458 &'local_domains'& domain list. The &"+"& character is used to indicate a
5459 reference to a named list. In this configuration, there is just one domain in
5460 &'local_domains'&, but in general there may be many.
5461
5462 The presence of this statement means that mail to postmaster is never blocked
5463 by any of the subsequent tests. This can be helpful while sorting out problems
5464 in cases where the subsequent tests are incorrectly denying access.
5465 .code
5466 require verify = sender
5467 .endd
5468 This statement requires the sender address to be verified before any subsequent
5469 ACL statement can be used. If verification fails, the incoming recipient
5470 address is refused. Verification consists of trying to route the address, to
5471 see if a bounce message could be delivered to it. In the case of remote
5472 addresses, basic verification checks only the domain, but &'callouts'& can be
5473 used for more verification if required. Section &<<SECTaddressverification>>&
5474 discusses the details of address verification.
5475 .code
5476 accept hosts = +relay_from_hosts
5477 control = submission
5478 .endd
5479 This statement accepts the address if the message is coming from one of the
5480 hosts that are defined as being allowed to relay through this host. Recipient
5481 verification is omitted here, because in many cases the clients are dumb MUAs
5482 that do not cope well with SMTP error responses. For the same reason, the
5483 second line specifies &"submission mode"& for messages that are accepted. This
5484 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
5485 messages that are deficient in some way, for example, because they lack a
5486 &'Date:'& header line. If you are actually relaying out from MTAs, you should
5487 probably add recipient verification here, and disable submission mode.
5488 .code
5489 accept authenticated = *
5490 control = submission
5491 .endd
5492 This statement accepts the address if the client host has authenticated itself.
5493 Submission mode is again specified, on the grounds that such messages are most
5494 likely to come from MUAs. The default configuration does not define any
5495 authenticators, though it does include some nearly complete commented-out
5496 examples described in &<<SECTdefconfauth>>&. This means that no client can in
5497 fact authenticate until you complete the authenticator definitions.
5498 .code
5499 require message = relay not permitted
5500 domains = +local_domains : +relay_domains
5501 .endd
5502 This statement rejects the address if its domain is neither a local domain nor
5503 one of the domains for which this host is a relay.
5504 .code
5505 require verify = recipient
5506 .endd
5507 This statement requires the recipient address to be verified; if verification
5508 fails, the address is rejected.
5509 .code
5510 # deny message = rejected because $sender_host_address \
5511 # is in a black list at $dnslist_domain\n\
5512 # $dnslist_text
5513 # dnslists = black.list.example
5514 #
5515 # warn dnslists = black.list.example
5516 # add_header = X-Warning: $sender_host_address is in \
5517 # a black list at $dnslist_domain
5518 # log_message = found in $dnslist_domain
5519 .endd
5520 These commented-out lines are examples of how you could configure Exim to check
5521 sending hosts against a DNS black list. The first statement rejects messages
5522 from blacklisted hosts, whereas the second just inserts a warning header
5523 line.
5524 .code
5525 # require verify = csa
5526 .endd
5527 This commented-out line is an example of how you could turn on client SMTP
5528 authorization (CSA) checking. Such checks do DNS lookups for special SRV
5529 records.
5530 .code
5531 accept
5532 .endd
5533 The final statement in the first ACL unconditionally accepts any recipient
5534 address that has successfully passed all the previous tests.
5535 .code
5536 acl_check_data:
5537 .endd
5538 This line marks the start of the second ACL, and names it. Most of the contents
5539 of this ACL are commented out:
5540 .code
5541 # deny malware = *
5542 # message = This message contains a virus \
5543 # ($malware_name).
5544 .endd
5545 These lines are examples of how to arrange for messages to be scanned for
5546 viruses when Exim has been compiled with the content-scanning extension, and a
5547 suitable virus scanner is installed. If the message is found to contain a
5548 virus, it is rejected with the given custom error message.
5549 .code
5550 # warn spam = nobody
5551 # message = X-Spam_score: $spam_score\n\
5552 # X-Spam_score_int: $spam_score_int\n\
5553 # X-Spam_bar: $spam_bar\n\
5554 # X-Spam_report: $spam_report
5555 .endd
5556 These lines are an example of how to arrange for messages to be scanned by
5557 SpamAssassin when Exim has been compiled with the content-scanning extension,
5558 and SpamAssassin has been installed. The SpamAssassin check is run with
5559 &`nobody`& as its user parameter, and the results are added to the message as a
5560 series of extra header line. In this case, the message is not rejected,
5561 whatever the spam score.
5562 .code
5563 accept
5564 .endd
5565 This final line in the DATA ACL accepts the message unconditionally.
5566
5567
5568 .section "Router configuration" "SECID55"
5569 .cindex "default" "routers"
5570 .cindex "routers" "default"
5571 The router configuration comes next in the default configuration, introduced
5572 by the line
5573 .code
5574 begin routers
5575 .endd
5576 Routers are the modules in Exim that make decisions about where to send
5577 messages. An address is passed to each router in turn, until it is either
5578 accepted, or failed. This means that the order in which you define the routers
5579 matters. Each router is fully described in its own chapter later in this
5580 manual. Here we give only brief overviews.
5581 .code
5582 # domain_literal:
5583 # driver = ipliteral
5584 # domains = !+local_domains
5585 # transport = remote_smtp
5586 .endd
5587 .cindex "domain literal" "default router"
5588 This router is commented out because the majority of sites do not want to
5589 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
5590 you uncomment this router, you also need to uncomment the setting of
5591 &%allow_domain_literals%& in the main part of the configuration.
5592 .code
5593 dnslookup:
5594 driver = dnslookup
5595 domains = ! +local_domains
5596 transport = remote_smtp
5597 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
5598 no_more
5599 .endd
5600 The first uncommented router handles addresses that do not involve any local
5601 domains. This is specified by the line
5602 .code
5603 domains = ! +local_domains
5604 .endd
5605 The &%domains%& option lists the domains to which this router applies, but the
5606 exclamation mark is a negation sign, so the router is used only for domains
5607 that are not in the domain list called &'local_domains'& (which was defined at
5608 the start of the configuration). The plus sign before &'local_domains'&
5609 indicates that it is referring to a named list. Addresses in other domains are
5610 passed on to the following routers.
5611
5612 The name of the router driver is &(dnslookup)&,
5613 and is specified by the &%driver%& option. Do not be confused by the fact that
5614 the name of this router instance is the same as the name of the driver. The
5615 instance name is arbitrary, but the name set in the &%driver%& option must be
5616 one of the driver modules that is in the Exim binary.
5617
5618 The &(dnslookup)& router routes addresses by looking up their domains in the
5619 DNS in order to obtain a list of hosts to which the address is routed. If the
5620 router succeeds, the address is queued for the &(remote_smtp)& transport, as
5621 specified by the &%transport%& option. If the router does not find the domain
5622 in the DNS, no further routers are tried because of the &%no_more%& setting, so
5623 the address fails and is bounced.
5624
5625 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
5626 be entirely ignored. This option is present because a number of cases have been
5627 encountered where MX records in the DNS point to host names
5628 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
5629 Completely ignoring these IP addresses causes Exim to fail to route the
5630 email address, so it bounces. Otherwise, Exim would log a routing problem, and
5631 continue to try to deliver the message periodically until the address timed
5632 out.
5633 .code
5634 system_aliases:
5635 driver = redirect
5636 allow_fail
5637 allow_defer
5638 data = ${lookup{$local_part}lsearch{/etc/aliases}}
5639 # user = exim
5640 file_transport = address_file
5641 pipe_transport = address_pipe
5642 .endd
5643 Control reaches this and subsequent routers only for addresses in the local
5644 domains. This router checks to see whether the local part is defined as an
5645 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
5646 data that it looks up from that file. If no data is found for the local part,
5647 the value of the &%data%& option is empty, causing the address to be passed to
5648 the next router.
5649
5650 &_/etc/aliases_& is a conventional name for the system aliases file that is
5651 often used. That is why it is referenced by from the default configuration
5652 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
5653 &_Local/Makefile_& before building Exim.
5654 .code
5655 userforward:
5656 driver = redirect
5657 check_local_user
5658 # local_part_suffix = +* : -*
5659 # local_part_suffix_optional
5660 file = $home/.forward
5661 # allow_filter
5662 no_verify
5663 no_expn
5664 check_ancestor
5665 file_transport = address_file
5666 pipe_transport = address_pipe
5667 reply_transport = address_reply
5668 .endd
5669 This is the most complicated router in the default configuration. It is another
5670 redirection router, but this time it is looking for forwarding data set up by
5671 individual users. The &%check_local_user%& setting specifies a check that the
5672 local part of the address is the login name of a local user. If it is not, the
5673 router is skipped. The two commented options that follow &%check_local_user%&,
5674 namely:
5675 .code
5676 # local_part_suffix = +* : -*
5677 # local_part_suffix_optional
5678 .endd
5679 .vindex "&$local_part_suffix$&"
5680 show how you can specify the recognition of local part suffixes. If the first
5681 is uncommented, a suffix beginning with either a plus or a minus sign, followed
5682 by any sequence of characters, is removed from the local part and placed in the
5683 variable &$local_part_suffix$&. The second suffix option specifies that the
5684 presence of a suffix in the local part is optional. When a suffix is present,
5685 the check for a local login uses the local part with the suffix removed.
5686
5687 When a local user account is found, the file called &_.forward_& in the user's
5688 home directory is consulted. If it does not exist, or is empty, the router
5689 declines. Otherwise, the contents of &_.forward_& are interpreted as
5690 redirection data (see chapter &<<CHAPredirect>>& for more details).
5691
5692 .cindex "Sieve filter" "enabling in default router"
5693 Traditional &_.forward_& files contain just a list of addresses, pipes, or
5694 files. Exim supports this by default. However, if &%allow_filter%& is set (it
5695 is commented out by default), the contents of the file are interpreted as a set
5696 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
5697 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
5698 separate document entitled &'Exim's interfaces to mail filtering'&.
5699
5700 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
5701 verifying addresses, or when running as a consequence of an SMTP EXPN command.
5702 There are two reasons for doing this:
5703
5704 .olist
5705 Whether or not a local user has a &_.forward_& file is not really relevant when
5706 checking an address for validity; it makes sense not to waste resources doing
5707 unnecessary work.
5708 .next
5709 More importantly, when Exim is verifying addresses or handling an EXPN
5710 command during an SMTP session, it is running as the Exim user, not as root.
5711 The group is the Exim group, and no additional groups are set up.
5712 It may therefore not be possible for Exim to read users' &_.forward_& files at
5713 this time.
5714 .endlist
5715
5716 The setting of &%check_ancestor%& prevents the router from generating a new
5717 address that is the same as any previous address that was redirected. (This
5718 works round a problem concerning a bad interaction between aliasing and
5719 forwarding &-- see section &<<SECTredlocmai>>&).
5720
5721 The final three option settings specify the transports that are to be used when
5722 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
5723 auto-reply, respectively. For example, if a &_.forward_& file contains
5724 .code
5725 a.nother@elsewhere.example, /home/spqr/archive
5726 .endd
5727 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
5728 transport.
5729 .code
5730 localuser:
5731 driver = accept
5732 check_local_user
5733 # local_part_suffix = +* : -*
5734 # local_part_suffix_optional
5735 transport = local_delivery
5736 .endd
5737 The final router sets up delivery into local mailboxes, provided that the local
5738 part is the name of a local login, by accepting the address and assigning it to
5739 the &(local_delivery)& transport. Otherwise, we have reached the end of the
5740 routers, so the address is bounced. The commented suffix settings fulfil the
5741 same purpose as they do for the &(userforward)& router.
5742
5743
5744 .section "Transport configuration" "SECID56"
5745 .cindex "default" "transports"
5746 .cindex "transports" "default"
5747 Transports define mechanisms for actually delivering messages. They operate
5748 only when referenced from routers, so the order in which they are defined does
5749 not matter. The transports section of the configuration starts with
5750 .code
5751 begin transports
5752 .endd
5753 One remote transport and four local transports are defined.
5754 .code
5755 remote_smtp:
5756 driver = smtp
5757 .endd
5758 This transport is used for delivering messages over SMTP connections. All its
5759 options are defaulted. The list of remote hosts comes from the router.
5760 .code
5761 local_delivery:
5762 driver = appendfile
5763 file = /var/mail/$local_part
5764 delivery_date_add
5765 envelope_to_add
5766 return_path_add
5767 # group = mail
5768 # mode = 0660
5769 .endd
5770 This &(appendfile)& transport is used for local delivery to user mailboxes in
5771 traditional BSD mailbox format. By default it runs under the uid and gid of the
5772 local user, which requires the sticky bit to be set on the &_/var/mail_&
5773 directory. Some systems use the alternative approach of running mail deliveries
5774 under a particular group instead of using the sticky bit. The commented options
5775 show how this can be done.
5776
5777 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
5778 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
5779 similarly-named options above.
5780 .code
5781 address_pipe:
5782 driver = pipe
5783 return_output
5784 .endd
5785 This transport is used for handling deliveries to pipes that are generated by
5786 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
5787 option specifies that any output generated by the pipe is to be returned to the
5788 sender.
5789 .code
5790 address_file:
5791 driver = appendfile
5792 delivery_date_add
5793 envelope_to_add
5794 return_path_add
5795 .endd
5796 This transport is used for handling deliveries to files that are generated by
5797 redirection. The name of the file is not specified in this instance of
5798 &(appendfile)&, because it comes from the &(redirect)& router.
5799 .code
5800 address_reply:
5801 driver = autoreply
5802 .endd
5803 This transport is used for handling automatic replies generated by users'
5804 filter files.
5805
5806
5807
5808 .section "Default retry rule" "SECID57"
5809 .cindex "retry" "default rule"
5810 .cindex "default" "retry rule"
5811 The retry section of the configuration file contains rules which affect the way
5812 Exim retries deliveries that cannot be completed at the first attempt. It is
5813 introduced by the line
5814 .code
5815 begin retry
5816 .endd
5817 In the default configuration, there is just one rule, which applies to all
5818 errors:
5819 .code
5820 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
5821 .endd
5822 This causes any temporarily failing address to be retried every 15 minutes for
5823 2 hours, then at intervals starting at one hour and increasing by a factor of
5824 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
5825 is not delivered after 4 days of temporary failure, it is bounced.
5826
5827 If the retry section is removed from the configuration, or is empty (that is,
5828 if no retry rules are defined), Exim will not retry deliveries. This turns
5829 temporary errors into permanent errors.
5830
5831
5832 .section "Rewriting configuration" "SECID58"
5833 The rewriting section of the configuration, introduced by
5834 .code
5835 begin rewrite
5836 .endd
5837 contains rules for rewriting addresses in messages as they arrive. There are no
5838 rewriting rules in the default configuration file.
5839
5840
5841
5842 .section "Authenticators configuration" "SECTdefconfauth"
5843 .cindex "AUTH" "configuration"
5844 The authenticators section of the configuration, introduced by
5845 .code
5846 begin authenticators
5847 .endd
5848 defines mechanisms for the use of the SMTP AUTH command. The default
5849 configuration file contains two commented-out example authenticators
5850 which support plaintext username/password authentication using the
5851 standard PLAIN mechanism and the traditional but non-standard LOGIN
5852 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
5853 to support most MUA software.
5854
5855 The example PLAIN authenticator looks like this:
5856 .code
5857 #PLAIN:
5858 # driver = plaintext
5859 # server_set_id = $auth2
5860 # server_prompts = :
5861 # server_condition = Authentication is not yet configured
5862 # server_advertise_condition = ${if def:tls_cipher }
5863 .endd
5864 And the example LOGIN authenticator looks like this:
5865 .code
5866 #LOGIN:
5867 # driver = plaintext
5868 # server_set_id = $auth1
5869 # server_prompts = <| Username: | Password:
5870 # server_condition = Authentication is not yet configured
5871 # server_advertise_condition = ${if def:tls_cipher }
5872 .endd
5873
5874 The &%server_set_id%& option makes Exim remember the authenticated username
5875 in &$authenticated_id$&, which can be used later in ACLs or routers. The
5876 &%server_prompts%& option configures the &(plaintext)& authenticator so
5877 that it implements the details of the specific authentication mechanism,
5878 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
5879 when Exim offers authentication to clients; in the examples, this is only
5880 when TLS or SSL has been started, so to enable the authenticators you also
5881 need to add support for TLS as described in &<<SECTdefconfmain>>&.
5882
5883 The &%server_condition%& setting defines how to verify that the username and
5884 password are correct. In the examples it just produces an error message.
5885 To make the authenticators work, you can use a string expansion
5886 expression like one of the examples in &<<CHAPplaintext>>&.
5887
5888 .ecindex IIDconfiwal
5889
5890
5891
5892 . ////////////////////////////////////////////////////////////////////////////
5893 . ////////////////////////////////////////////////////////////////////////////
5894
5895 .chapter "Regular expressions" "CHAPregexp"
5896
5897 .cindex "regular expressions" "library"
5898 .cindex "PCRE"
5899 Exim supports the use of regular expressions in many of its options. It
5900 uses the PCRE regular expression library; this provides regular expression
5901 matching that is compatible with Perl 5. The syntax and semantics of
5902 regular expressions is discussed in many Perl reference books, and also in
5903 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
5904 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
5905
5906 The documentation for the syntax and semantics of the regular expressions that
5907 are supported by PCRE is included in the PCRE distribution, and no further
5908 description is included here. The PCRE functions are called from Exim using
5909 the default option settings (that is, with no PCRE options set), except that
5910 the PCRE_CASELESS option is set when the matching is required to be
5911 case-insensitive.
5912
5913 In most cases, when a regular expression is required in an Exim configuration,
5914 it has to start with a circumflex, in order to distinguish it from plain text
5915 or an &"ends with"& wildcard. In this example of a configuration setting, the
5916 second item in the colon-separated list is a regular expression.
5917 .code
5918 domains = a.b.c : ^\\d{3} : *.y.z : ...
5919 .endd
5920 The doubling of the backslash is required because of string expansion that
5921 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
5922 of this issue, and a way of avoiding the need for doubling backslashes. The
5923 regular expression that is eventually used in this example contains just one
5924 backslash. The circumflex is included in the regular expression, and has the
5925 normal effect of &"anchoring"& it to the start of the string that is being
5926 matched.
5927
5928 There are, however, two cases where a circumflex is not required for the
5929 recognition of a regular expression: these are the &%match%& condition in a
5930 string expansion, and the &%matches%& condition in an Exim filter file. In
5931 these cases, the relevant string is always treated as a regular expression; if
5932 it does not start with a circumflex, the expression is not anchored, and can
5933 match anywhere in the subject string.
5934
5935 In all cases, if you want a regular expression to match at the end of a string,
5936 you must code the $ metacharacter to indicate this. For example:
5937 .code
5938 domains = ^\\d{3}\\.example
5939 .endd
5940 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
5941 You need to use:
5942 .code
5943 domains = ^\\d{3}\\.example\$
5944 .endd
5945 if you want &'example'& to be the top-level domain. The backslash before the
5946 $ is needed because string expansion also interprets dollar characters.
5947
5948
5949
5950 . ////////////////////////////////////////////////////////////////////////////
5951 . ////////////////////////////////////////////////////////////////////////////
5952
5953 .chapter "File and database lookups" "CHAPfdlookup"
5954 .scindex IIDfidalo1 "file" "lookups"
5955 .scindex IIDfidalo2 "database" "lookups"
5956 .cindex "lookup" "description of"
5957 Exim can be configured to look up data in files or databases as it processes
5958 messages. Two different kinds of syntax are used:
5959
5960 .olist
5961 A string that is to be expanded may contain explicit lookup requests. These
5962 cause parts of the string to be replaced by data that is obtained from the
5963 lookup. Lookups of this type are conditional expansion items. Different results
5964 can be defined for the cases of lookup success and failure. See chapter
5965 &<<CHAPexpand>>&, where string expansions are described in detail.
5966 .next
5967 Lists of domains, hosts, and email addresses can contain lookup requests as a
5968 way of avoiding excessively long linear lists. In this case, the data that is
5969 returned by the lookup is often (but not always) discarded; whether the lookup
5970 succeeds or fails is what really counts. These kinds of list are described in
5971 chapter &<<CHAPdomhosaddlists>>&.
5972 .endlist
5973
5974 String expansions, lists, and lookups interact with each other in such a way
5975 that there is no order in which to describe any one of them that does not
5976 involve references to the others. Each of these three chapters makes more sense
5977 if you have read the other two first. If you are reading this for the first
5978 time, be aware that some of it will make a lot more sense after you have read
5979 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
5980
5981 .section "Examples of different lookup syntax" "SECID60"
5982 It is easy to confuse the two different kinds of lookup, especially as the
5983 lists that may contain the second kind are always expanded before being
5984 processed as lists. Therefore, they may also contain lookups of the first kind.
5985 Be careful to distinguish between the following two examples:
5986 .code
5987 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
5988 domains = lsearch;/some/file
5989 .endd
5990 The first uses a string expansion, the result of which must be a domain list.
5991 No strings have been specified for a successful or a failing lookup; the
5992 defaults in this case are the looked-up data and an empty string, respectively.
5993 The expansion takes place before the string is processed as a list, and the
5994 file that is searched could contain lines like this:
5995 .code
5996 192.168.3.4: domain1:domain2:...
5997 192.168.1.9: domain3:domain4:...
5998 .endd
5999 When the lookup succeeds, the result of the expansion is a list of domains (and
6000 possibly other types of item that are allowed in domain lists).
6001
6002 In the second example, the lookup is a single item in a domain list. It causes
6003 Exim to use a lookup to see if the domain that is being processed can be found
6004 in the file. The file could contains lines like this:
6005 .code
6006 domain1:
6007 domain2:
6008 .endd
6009 Any data that follows the keys is not relevant when checking that the domain
6010 matches the list item.
6011
6012 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6013 Consider a file containing lines like this:
6014 .code
6015 192.168.5.6: lsearch;/another/file
6016 .endd
6017 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6018 first &%domains%& setting above generates the second setting, which therefore
6019 causes a second lookup to occur.
6020
6021 The rest of this chapter describes the different lookup types that are
6022 available. Any of them can be used in any part of the configuration where a
6023 lookup is permitted.
6024
6025
6026 .section "Lookup types" "SECID61"
6027 .cindex "lookup" "types of"
6028 .cindex "single-key lookup" "definition of"
6029 Two different types of data lookup are implemented:
6030
6031 .ilist
6032 The &'single-key'& type requires the specification of a file in which to look,
6033 and a single key to search for. The key must be a non-empty string for the
6034 lookup to succeed. The lookup type determines how the file is searched.
6035 .next
6036 .cindex "query-style lookup" "definition of"
6037 The &'query-style'& type accepts a generalized database query. No particular
6038 key value is assumed by Exim for query-style lookups. You can use whichever
6039 Exim variables you need to construct the database query.
6040 .endlist
6041
6042 The code for each lookup type is in a separate source file that is included in
6043 the binary of Exim only if the corresponding compile-time option is set. The
6044 default settings in &_src/EDITME_& are:
6045 .code
6046 LOOKUP_DBM=yes
6047 LOOKUP_LSEARCH=yes
6048 .endd
6049 which means that only linear searching and DBM lookups are included by default.
6050 For some types of lookup (e.g. SQL databases), you need to install appropriate
6051 libraries and header files before building Exim.
6052
6053
6054
6055
6056 .section "Single-key lookup types" "SECTsinglekeylookups"
6057 .cindex "lookup" "single-key types"
6058 .cindex "single-key lookup" "list of types"
6059 The following single-key lookup types are implemented:
6060
6061 .ilist
6062 .cindex "cdb" "description of"
6063 .cindex "lookup" "cdb"
6064 .cindex "binary zero" "in lookup key"
6065 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6066 string without a terminating binary zero. The cdb format is designed for
6067 indexed files that are read frequently and never updated, except by total
6068 re-creation. As such, it is particularly suitable for large files containing
6069 aliases or other indexed data referenced by an MTA. Information about cdb can
6070 be found in several places:
6071 .display
6072 &url(http://www.pobox.com/~djb/cdb.html)
6073 &url(ftp://ftp.corpit.ru/pub/tinycdb/)
6074 &url(http://packages.debian.org/stable/utils/freecdb.html)
6075 .endd
6076 A cdb distribution is not needed in order to build Exim with cdb support,
6077 because the code for reading cdb files is included directly in Exim itself.
6078 However, no means of building or testing cdb files is provided with Exim, so
6079 you need to obtain a cdb distribution in order to do this.
6080 .next
6081 .cindex "DBM" "lookup type"
6082 .cindex "lookup" "dbm"
6083 .cindex "binary zero" "in lookup key"
6084 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6085 DBM file by looking up the record with the given key. A terminating binary
6086 zero is included in the key that is passed to the DBM library. See section
6087 &<<SECTdb>>& for a discussion of DBM libraries.
6088
6089 .cindex "Berkeley DB library" "file format"
6090 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6091 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6092 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6093 the DB_UNKNOWN option. This enables it to handle any of the types of database
6094 that the library supports, and can be useful for accessing DBM files created by
6095 other applications. (For earlier DB versions, DB_HASH is always used.)
6096 .next
6097 .cindex "lookup" "dbmnz"
6098 .cindex "lookup" "dbm &-- terminating zero"
6099 .cindex "binary zero" "in lookup key"
6100 .cindex "Courier"
6101 .cindex "&_/etc/userdbshadow.dat_&"
6102 .cindex "dmbnz lookup type"
6103 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6104 is not included in the key that is passed to the DBM library. You may need this
6105 if you want to look up data in files that are created by or shared with some
6106 other application that does not use terminating zeros. For example, you need to
6107 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6108 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6109 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6110 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6111 .next
6112 .cindex "lookup" "dsearch"
6113 .cindex "dsearch lookup type"
6114 &(dsearch)&: The given file must be a directory; this is searched for an entry
6115 whose name is the key by calling the &[lstat()]& function. The key may not
6116 contain any forward slash characters. If &[lstat()]& succeeds, the result of
6117 the lookup is the name of the entry, which may be a file, directory,
6118 symbolic link, or any other kind of directory entry. An example of how this
6119 lookup can be used to support virtual domains is given in section
6120 &<<SECTvirtualdomains>>&.
6121 .next
6122 .cindex "lookup" "iplsearch"
6123 .cindex "iplsearch lookup type"
6124 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6125 terminated by a colon or white space or the end of the line. The keys in the
6126 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6127 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6128 being interpreted as a key terminator. For example:
6129 .code
6130 1.2.3.4: data for 1.2.3.4
6131 192.168.0.0/16 data for 192.168.0.0/16
6132 "abcd::cdab": data for abcd::cdab
6133 "abcd:abcd::/32" data for abcd:abcd::/32
6134 .endd
6135 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6136 file is searched linearly, using the CIDR masks where present, until a matching
6137 key is found. The first key that matches is used; there is no attempt to find a
6138 &"best"& match. Apart from the way the keys are matched, the processing for
6139 &(iplsearch)& is the same as for &(lsearch)&.
6140
6141 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6142 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6143 lookup types support only literal keys.
6144
6145 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6146 the implicit key is the host's IP address rather than its name (see section
6147 &<<SECThoslispatsikey>>&).
6148 .next
6149 .cindex "linear search"
6150 .cindex "lookup" "lsearch"
6151 .cindex "lsearch lookup type"
6152 .cindex "case sensitivity" "in lsearch lookup"
6153 &(lsearch)&: The given file is a text file that is searched linearly for a
6154 line beginning with the search key, terminated by a colon or white space or the
6155 end of the line. The search is case-insensitive; that is, upper and lower case
6156 letters are treated as the same. The first occurrence of the key that is found
6157 in the file is used.
6158
6159 White space between the key and the colon is permitted. The remainder of the
6160 line, with leading and trailing white space removed, is the data. This can be
6161 continued onto subsequent lines by starting them with any amount of white
6162 space, but only a single space character is included in the data at such a
6163 junction. If the data begins with a colon, the key must be terminated by a
6164 colon, for example:
6165 .code
6166 baduser: :fail:
6167 .endd
6168 Empty lines and lines beginning with # are ignored, even if they occur in the
6169 middle of an item. This is the traditional textual format of alias files. Note
6170 that the keys in an &(lsearch)& file are literal strings. There is no
6171 wildcarding of any kind.
6172
6173 .cindex "lookup" "lsearch &-- colons in keys"
6174 .cindex "white space" "in lsearch key"
6175 In most &(lsearch)& files, keys are not required to contain colons or #
6176 characters, or white space. However, if you need this feature, it is available.
6177 If a key begins with a doublequote character, it is terminated only by a
6178 matching quote (or end of line), and the normal escaping rules apply to its
6179 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6180 quoted keys (exactly as for unquoted keys). There is no special handling of
6181 quotes for the data part of an &(lsearch)& line.
6182
6183 .next
6184 .cindex "NIS lookup type"
6185 .cindex "lookup" "NIS"
6186 .cindex "binary zero" "in lookup key"
6187 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
6188 the given key, without a terminating binary zero. There is a variant called
6189 &(nis0)& which does include the terminating binary zero in the key. This is
6190 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6191 aliases; the full map names must be used.
6192
6193 .next
6194 .cindex "wildlsearch lookup type"
6195 .cindex "lookup" "wildlsearch"
6196 .cindex "nwildlsearch lookup type"
6197 .cindex "lookup" "nwildlsearch"
6198 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6199 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6200 the file may be wildcarded. The difference between these two lookup types is
6201 that for &(wildlsearch)&, each key in the file is string-expanded before being
6202 used, whereas for &(nwildlsearch)&, no expansion takes place.
6203
6204 .cindex "case sensitivity" "in (n)wildlsearch lookup"
6205 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
6206 file that are regular expressions can be made case-sensitive by the use of
6207 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
6208
6209 . ==== As this is a nested list, any displays it contains must be indented
6210 . ==== as otherwise they are too far to the left.
6211
6212 .olist
6213 The string may begin with an asterisk to mean &"ends with"&. For example:
6214 .code
6215 *.a.b.c data for anything.a.b.c
6216 *fish data for anythingfish
6217 .endd
6218 .next
6219 The string may begin with a circumflex to indicate a regular expression. For
6220 example, for &(wildlsearch)&:
6221 .code
6222 ^\N\d+\.a\.b\N data for <digits>.a.b
6223 .endd
6224 Note the use of &`\N`& to disable expansion of the contents of the regular
6225 expression. If you are using &(nwildlsearch)&, where the keys are not
6226 string-expanded, the equivalent entry is:
6227 .code
6228 ^\d+\.a\.b data for <digits>.a.b
6229 .endd
6230 The case-insensitive flag is set at the start of compiling the regular
6231 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
6232 For example, to make the entire pattern case-sensitive:
6233 .code
6234 ^(?-i)\d+\.a\.b data for <digits>.a.b
6235 .endd
6236
6237 If the regular expression contains white space or colon characters, you must
6238 either quote it (see &(lsearch)& above), or represent these characters in other
6239 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
6240 colon. This may be easier than quoting, because if you quote, you have to
6241 escape all the backslashes inside the quotes.
6242
6243 &*Note*&: It is not possible to capture substrings in a regular expression
6244 match for later use, because the results of all lookups are cached. If a lookup
6245 is repeated, the result is taken from the cache, and no actual pattern matching
6246 takes place. The values of all the numeric variables are unset after a
6247 &((n)wildlsearch)& match.
6248
6249 .next
6250 Although I cannot see it being of much use, the general matching function that
6251 is used to implement &((n)wildlsearch)& means that the string may begin with a
6252 lookup name terminated by a semicolon, and followed by lookup data. For
6253 example:
6254 .code
6255 cdb;/some/file data for keys that match the file
6256 .endd
6257 The data that is obtained from the nested lookup is discarded.
6258 .endlist olist
6259
6260 Keys that do not match any of these patterns are interpreted literally. The
6261 continuation rules for the data are the same as for &(lsearch)&, and keys may
6262 be followed by optional colons.
6263
6264 &*Warning*&: Unlike most other single-key lookup types, a file of data for
6265 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
6266 lookup types support only literal keys.
6267 .endlist ilist
6268
6269
6270 .section "Query-style lookup types" "SECID62"
6271 .cindex "lookup" "query-style types"
6272 .cindex "query-style lookup" "list of types"
6273 The supported query-style lookup types are listed below. Further details about
6274 many of them are given in later sections.
6275
6276 .ilist
6277 .cindex "DNS" "as a lookup type"
6278 .cindex "lookup" "DNS"
6279 &(dnsdb)&: This does a DNS search for one or more records whose domain names
6280 are given in the supplied query. The resulting data is the contents of the
6281 records. See section &<<SECTdnsdb>>&.
6282 .next
6283 .cindex "InterBase lookup type"
6284 .cindex "lookup" "InterBase"
6285 &(ibase)&: This does a lookup in an InterBase database.
6286 .next
6287 .cindex "LDAP" "lookup type"
6288 .cindex "lookup" "LDAP"
6289 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
6290 returns attributes from a single entry. There is a variant called &(ldapm)&
6291 that permits values from multiple entries to be returned. A third variant
6292 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
6293 any attribute values. See section &<<SECTldap>>&.
6294 .next
6295 .cindex "MySQL" "lookup type"
6296 .cindex "lookup" "MySQL"
6297 &(mysql)&: The format of the query is an SQL statement that is passed to a
6298 MySQL database. See section &<<SECTsql>>&.
6299 .next
6300 .cindex "NIS+ lookup type"
6301 .cindex "lookup" "NIS+"
6302 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
6303 the field to be returned. See section &<<SECTnisplus>>&.
6304 .next
6305 .cindex "Oracle" "lookup type"
6306 .cindex "lookup" "Oracle"
6307 &(oracle)&: The format of the query is an SQL statement that is passed to an
6308 Oracle database. See section &<<SECTsql>>&.
6309 .next
6310 .cindex "lookup" "passwd"
6311 .cindex "passwd lookup type"
6312 .cindex "&_/etc/passwd_&"
6313 &(passwd)& is a query-style lookup with queries that are just user names. The
6314 lookup calls &[getpwnam()]& to interrogate the system password data, and on
6315 success, the result string is the same as you would get from an &(lsearch)&
6316 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
6317 password value. For example:
6318 .code
6319 *:42:42:King Rat:/home/kr:/bin/bash
6320 .endd
6321 .next
6322 .cindex "PostgreSQL lookup type"
6323 .cindex "lookup" "PostgreSQL"
6324 &(pgsql)&: The format of the query is an SQL statement that is passed to a
6325 PostgreSQL database. See section &<<SECTsql>>&.
6326
6327 .next
6328 .cindex "sqlite lookup type"
6329 .cindex "lookup" "sqlite"
6330 &(sqlite)&: The format of the query is a file name followed by an SQL statement
6331 that is passed to an SQLite database. See section &<<SECTsqlite>>&.
6332
6333 .next
6334 &(testdb)&: This is a lookup type that is used for testing Exim. It is
6335 not likely to be useful in normal operation.
6336 .next
6337 .cindex "whoson lookup type"
6338 .cindex "lookup" "whoson"
6339 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
6340 allows a server to check whether a particular (dynamically allocated) IP
6341 address is currently allocated to a known (trusted) user and, optionally, to
6342 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
6343 at one time for &"POP before SMTP"& authentication, but that approach has been
6344 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
6345 &"POP before SMTP"& checking using ACL statements such as
6346 .code
6347 require condition = \
6348 ${lookup whoson {$sender_host_address}{yes}{no}}
6349 .endd
6350 The query consists of a single IP address. The value returned is the name of
6351 the authenticated user, which is stored in the variable &$value$&. However, in
6352 this example, the data in &$value$& is not used; the result of the lookup is
6353 one of the fixed strings &"yes"& or &"no"&.
6354 .endlist
6355
6356
6357
6358 .section "Temporary errors in lookups" "SECID63"
6359 .cindex "lookup" "temporary error in"
6360 Lookup functions can return temporary error codes if the lookup cannot be
6361 completed. For example, an SQL or LDAP database might be unavailable. For this
6362 reason, it is not advisable to use a lookup that might do this for critical
6363 options such as a list of local domains.
6364
6365 When a lookup cannot be completed in a router or transport, delivery
6366 of the message (to the relevant address) is deferred, as for any other
6367 temporary error. In other circumstances Exim may assume the lookup has failed,
6368 or may give up altogether.
6369
6370
6371
6372 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
6373 .cindex "wildcard lookups"
6374 .cindex "lookup" "default values"
6375 .cindex "lookup" "wildcard"
6376 .cindex "lookup" "* added to type"
6377 .cindex "default" "in single-key lookups"
6378 In this context, a &"default value"& is a value specified by the administrator
6379 that is to be used if a lookup fails.
6380
6381 &*Note:*& This section applies only to single-key lookups. For query-style
6382 lookups, the facilities of the query language must be used. An attempt to
6383 specify a default for a query-style lookup provokes an error.
6384
6385 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
6386 and the initial lookup fails, the key &"*"& is looked up in the file to
6387 provide a default value. See also the section on partial matching below.
6388
6389 .cindex "*@ with single-key lookup"
6390 .cindex "lookup" "*@ added to type"
6391 .cindex "alias file" "per-domain default"
6392 Alternatively, if &"*@"& is added to a single-key lookup type (for example
6393 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
6394 character, a second lookup is done with everything before the last @ replaced
6395 by *. This makes it possible to provide per-domain defaults in alias files
6396 that include the domains in the keys. If the second lookup fails (or doesn't
6397 take place because there is no @ in the key), &"*"& is looked up.
6398 For example, a &(redirect)& router might contain:
6399 .code
6400 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
6401 .endd
6402 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
6403 looks up these keys, in this order:
6404 .code
6405 jane@eyre.example
6406 *@eyre.example
6407 *
6408 .endd
6409 The data is taken from whichever key it finds first. &*Note*&: In an
6410 &(lsearch)& file, this does not mean the first of these keys in the file. A
6411 complete scan is done for each key, and only if it is not found at all does
6412 Exim move on to try the next key.
6413
6414
6415
6416 .section "Partial matching in single-key lookups" "SECTpartiallookup"
6417 .cindex "partial matching"
6418 .cindex "wildcard lookups"
6419 .cindex "lookup" "partial matching"
6420 .cindex "lookup" "wildcard"
6421 .cindex "asterisk" "in search type"
6422 The normal operation of a single-key lookup is to search the file for an exact
6423 match with the given key. However, in a number of situations where domains are
6424 being looked up, it is useful to be able to do partial matching. In this case,
6425 information in the file that has a key starting with &"*."& is matched by any
6426 domain that ends with the components that follow the full stop. For example, if
6427 a key in a DBM file is
6428 .code
6429 *.dates.fict.example
6430 .endd
6431 then when partial matching is enabled this is matched by (amongst others)
6432 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
6433 by &'dates.fict.example'&, if that does not appear as a separate key in the
6434 file.
6435
6436 &*Note*&: Partial matching is not available for query-style lookups. It is
6437 also not available for any lookup items in address lists (see section
6438 &<<SECTaddresslist>>&).
6439
6440 Partial matching is implemented by doing a series of separate lookups using
6441 keys constructed by modifying the original subject key. This means that it can
6442 be used with any of the single-key lookup types, provided that
6443 partial matching keys
6444 beginning with a special prefix (default &"*."&) are included in the data file.
6445 Keys in the file that do not begin with the prefix are matched only by
6446 unmodified subject keys when partial matching is in use.
6447
6448 Partial matching is requested by adding the string &"partial-"& to the front of
6449 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
6450 is done, the subject key is first looked up unmodified; if that fails, &"*."&
6451 is added at the start of the subject key, and it is looked up again. If that
6452 fails, further lookups are tried with dot-separated components removed from the
6453 start of the subject key, one-by-one, and &"*."& added on the front of what
6454 remains.
6455
6456 A minimum number of two non-* components are required. This can be adjusted
6457 by including a number before the hyphen in the search type. For example,
6458 &%partial3-lsearch%& specifies a minimum of three non-* components in the
6459 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
6460 subject key is &'2250.dates.fict.example'& then the following keys are looked
6461 up when the minimum number of non-* components is two:
6462 .code
6463 2250.dates.fict.example
6464 *.2250.dates.fict.example
6465 *.dates.fict.example
6466 *.fict.example
6467 .endd
6468 As soon as one key in the sequence is successfully looked up, the lookup
6469 finishes.
6470
6471 .cindex "lookup" "partial matching &-- changing prefix"
6472 .cindex "prefix" "for partial matching"
6473 The use of &"*."& as the partial matching prefix is a default that can be
6474 changed. The motivation for this feature is to allow Exim to operate with file
6475 formats that are used by other MTAs. A different prefix can be supplied in
6476 parentheses instead of the hyphen after &"partial"&. For example:
6477 .code
6478 domains = partial(.)lsearch;/some/file
6479 .endd
6480 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
6481 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
6482 components is unchanged). The prefix may consist of any punctuation characters
6483 other than a closing parenthesis. It may be empty, for example:
6484 .code
6485 domains = partial1()cdb;/some/file
6486 .endd
6487 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
6488 &`a.b.c`&, &`b.c`&, and &`c`&.
6489
6490 If &"partial0"& is specified, what happens at the end (when the lookup with
6491 just one non-wild component has failed, and the original key is shortened right
6492 down to the null string) depends on the prefix:
6493
6494 .ilist
6495 If the prefix has zero length, the whole lookup fails.
6496 .next
6497 If the prefix has length 1, a lookup for just the prefix is done. For
6498 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
6499 .next
6500 Otherwise, if the prefix ends in a dot, the dot is removed, and the
6501 remainder is looked up. With the default prefix, therefore, the final lookup is
6502 for &"*"& on its own.
6503 .next
6504 Otherwise, the whole prefix is looked up.
6505 .endlist
6506
6507
6508 If the search type ends in &"*"& or &"*@"& (see section
6509 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
6510 this implies happens after all partial lookups have failed. If &"partial0"& is
6511 specified, adding &"*"& to the search type has no effect with the default
6512 prefix, because the &"*"& key is already included in the sequence of partial
6513 lookups. However, there might be a use for lookup types such as
6514 &"partial0(.)lsearch*"&.
6515
6516 The use of &"*"& in lookup partial matching differs from its use as a wildcard
6517 in domain lists and the like. Partial matching works only in terms of
6518 dot-separated components; a key such as &`*fict.example`&
6519 in a database file is useless, because the asterisk in a partial matching
6520 subject key is always followed by a dot.
6521
6522
6523
6524
6525 .section "Lookup caching" "SECID64"
6526 .cindex "lookup" "caching"
6527 .cindex "caching" "lookup data"
6528 Exim caches all lookup results in order to avoid needless repetition of
6529 lookups. However, because (apart from the daemon) Exim operates as a collection
6530 of independent, short-lived processes, this caching applies only within a
6531 single Exim process. There is no inter-process lookup caching facility.
6532
6533 For single-key lookups, Exim keeps the relevant files open in case there is
6534 another lookup that needs them. In some types of configuration this can lead to
6535 many files being kept open for messages with many recipients. To avoid hitting
6536 the operating system limit on the number of simultaneously open files, Exim
6537 closes the least recently used file when it needs to open more files than its
6538 own internal limit, which can be changed via the &%lookup_open_max%& option.
6539
6540 The single-key lookup files are closed and the lookup caches are flushed at
6541 strategic points during delivery &-- for example, after all routing is
6542 complete.
6543
6544
6545
6546
6547 .section "Quoting lookup data" "SECID65"
6548 .cindex "lookup" "quoting"
6549 .cindex "quoting" "in lookups"
6550 When data from an incoming message is included in a query-style lookup, there
6551 is the possibility of special characters in the data messing up the syntax of
6552 the query. For example, a NIS+ query that contains
6553 .code
6554 [name=$local_part]
6555 .endd
6556 will be broken if the local part happens to contain a closing square bracket.
6557 For NIS+, data can be enclosed in double quotes like this:
6558 .code
6559 [name="$local_part"]
6560 .endd
6561 but this still leaves the problem of a double quote in the data. The rule for
6562 NIS+ is that double quotes must be doubled. Other lookup types have different
6563 rules, and to cope with the differing requirements, an expansion operator
6564 of the following form is provided:
6565 .code
6566 ${quote_<lookup-type>:<string>}
6567 .endd
6568 For example, the safest way to write the NIS+ query is
6569 .code
6570 [name="${quote_nisplus:$local_part}"]
6571 .endd
6572 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
6573 operator can be used for all lookup types, but has no effect for single-key
6574 lookups, since no quoting is ever needed in their key strings.
6575
6576
6577
6578
6579 .section "More about dnsdb" "SECTdnsdb"
6580 .cindex "dnsdb lookup"
6581 .cindex "lookup" "dnsdb"
6582 .cindex "DNS" "as a lookup type"
6583 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
6584 of a record type and a domain name, separated by an equals sign. For example,
6585 an expansion string could contain:
6586 .code
6587 ${lookup dnsdb{mx=a.b.example}{$value}fail}
6588 .endd
6589 If the lookup succeeds, the result is placed in &$value$&, which in this case
6590 is used on its own as the result. If the lookup does not succeed, the
6591 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
6592 &<<SECTforexpfai>>& for an explanation of what this means.
6593
6594 The supported DNS record types are A, CNAME, MX, NS, PTR, SRV, and TXT, and,
6595 when Exim is compiled with IPv6 support, AAAA (and A6 if that is also
6596 configured). If no type is given, TXT is assumed. When the type is PTR,
6597 the data can be an IP address, written as normal; inversion and the addition of
6598 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
6599 .code
6600 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
6601 .endd
6602 If the data for a PTR record is not a syntactically valid IP address, it is not
6603 altered and nothing is added.
6604
6605 .cindex "MX record" "in &(dnsdb)& lookup"
6606 .cindex "SRV record" "in &(dnsdb)& lookup"
6607 For an MX lookup, both the preference value and the host name are returned for
6608 each record, separated by a space. For an SRV lookup, the priority, weight,
6609 port, and host name are returned for each record, separated by spaces.
6610
6611 For any record type, if multiple records are found (or, for A6 lookups, if a
6612 single record leads to multiple addresses), the data is returned as a
6613 concatenation, with newline as the default separator. The order, of course,
6614 depends on the DNS resolver. You can specify a different separator character
6615 between multiple records by putting a right angle-bracket followed immediately
6616 by the new separator at the start of the query. For example:
6617 .code
6618 ${lookup dnsdb{>: a=host1.example}}
6619 .endd
6620 It is permitted to specify a space as the separator character. Further
6621 white space is ignored.
6622
6623 .section "Pseudo dnsdb record types" "SECID66"
6624 .cindex "MX record" "in &(dnsdb)& lookup"
6625 By default, both the preference value and the host name are returned for
6626 each MX record, separated by a space. If you want only host names, you can use
6627 the pseudo-type MXH:
6628 .code
6629 ${lookup dnsdb{mxh=a.b.example}}
6630 .endd
6631 In this case, the preference values are omitted, and just the host names are
6632 returned.
6633
6634 .cindex "name server for enclosing domain"
6635 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
6636 records on the given domain, but if none are found, it removes the first
6637 component of the domain name, and tries again. This process continues until NS
6638 records are found or there are no more components left (or there is a DNS
6639 error). In other words, it may return the name servers for a top-level domain,
6640 but it never returns the root name servers. If there are no NS records for the
6641 top-level domain, the lookup fails. Consider these examples:
6642 .code
6643 ${lookup dnsdb{zns=xxx.quercite.com}}
6644 ${lookup dnsdb{zns=xxx.edu}}
6645 .endd
6646 Assuming that in each case there are no NS records for the full domain name,
6647 the first returns the name servers for &%quercite.com%&, and the second returns
6648 the name servers for &%edu%&.
6649
6650 You should be careful about how you use this lookup because, unless the
6651 top-level domain does not exist, the lookup always returns some host names. The
6652 sort of use to which this might be put is for seeing if the name servers for a
6653 given domain are on a blacklist. You can probably assume that the name servers
6654 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
6655 such a list.
6656
6657 .cindex "CSA" "in &(dnsdb)& lookup"
6658 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
6659 records according to the CSA rules, which are described in section
6660 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
6661 not sufficient because of the extra parent domain search behaviour of CSA. The
6662 result of a successful lookup such as:
6663 .code
6664 ${lookup dnsdb {csa=$sender_helo_name}}
6665 .endd
6666 has two space-separated fields: an authorization code and a target host name.
6667 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
6668 authorization required but absent, or &"?"& for unknown.
6669
6670
6671 .section "Multiple dnsdb lookups" "SECID67"
6672 In the previous sections, &(dnsdb)& lookups for a single domain are described.
6673 However, you can specify a list of domains or IP addresses in a single
6674 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
6675 the default separator, but with the ability to change this. For example:
6676 .code
6677 ${lookup dnsdb{one.domain.com:two.domain.com}}
6678 ${lookup dnsdb{a=one.host.com:two.host.com}}
6679 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
6680 .endd
6681 In order to retain backwards compatibility, there is one special case: if
6682 the lookup type is PTR and no change of separator is specified, Exim looks
6683 to see if the rest of the string is precisely one IPv6 address. In this
6684 case, it does not treat it as a list.
6685
6686 The data from each lookup is concatenated, with newline separators by default,
6687 in the same way that multiple DNS records for a single item are handled. A
6688 different separator can be specified, as described above.
6689
6690 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
6691 temporary DNS error for any of them, the behaviour is controlled by
6692 an optional keyword followed by a comma that may appear before the record
6693 type. The possible keywords are &"defer_strict"&, &"defer_never"&, and
6694 &"defer_lax"&. With &"strict"& behaviour, any temporary DNS error causes the
6695 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
6696 ignored, and the behaviour is as if the DNS lookup failed to find anything.
6697 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
6698 error causes the whole lookup to defer only if none of the other lookups
6699 succeed. The default is &"lax"&, so the following lookups are equivalent:
6700 .code
6701 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
6702 ${lookup dnsdb{a=one.host.com:two.host.com}}
6703 .endd
6704 Thus, in the default case, as long as at least one of the DNS lookups
6705 yields some data, the lookup succeeds.
6706
6707
6708
6709
6710 .section "More about LDAP" "SECTldap"
6711 .cindex "LDAP" "lookup, more about"
6712 .cindex "lookup" "LDAP"
6713 .cindex "Solaris" "LDAP"
6714 The original LDAP implementation came from the University of Michigan; this has
6715 become &"Open LDAP"&, and there are now two different releases. Another
6716 implementation comes from Netscape, and Solaris 7 and subsequent releases
6717 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
6718 the lookup function level, their error handling is different. For this reason
6719 it is necessary to set a compile-time variable when building Exim with LDAP, to
6720 indicate which LDAP library is in use. One of the following should appear in
6721 your &_Local/Makefile_&:
6722 .code
6723 LDAP_LIB_TYPE=UMICHIGAN
6724 LDAP_LIB_TYPE=OPENLDAP1
6725 LDAP_LIB_TYPE=OPENLDAP2
6726 LDAP_LIB_TYPE=NETSCAPE
6727 LDAP_LIB_TYPE=SOLARIS
6728 .endd
6729 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
6730 same interface as the University of Michigan version.
6731
6732 There are three LDAP lookup types in Exim. These behave slightly differently in
6733 the way they handle the results of a query:
6734
6735 .ilist
6736 &(ldap)& requires the result to contain just one entry; if there are more, it
6737 gives an error.
6738 .next
6739 &(ldapdn)& also requires the result to contain just one entry, but it is the
6740 Distinguished Name that is returned rather than any attribute values.
6741 .next
6742 &(ldapm)& permits the result to contain more than one entry; the attributes
6743 from all of them are returned.
6744 .endlist
6745
6746
6747 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
6748 Exim behaves as if the entry did not exist, and the lookup fails. The format of
6749 the data returned by a successful lookup is described in the next section.
6750 First we explain how LDAP queries are coded.
6751
6752
6753 .section "Format of LDAP queries" "SECTforldaque"
6754 .cindex "LDAP" "query format"
6755 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
6756 the configuration of a &(redirect)& router one might have this setting:
6757 .code
6758 data = ${lookup ldap \
6759 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
6760 c=UK?mailbox?base?}}
6761 .endd
6762 .cindex "LDAP" "with TLS"
6763 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
6764 secure (encrypted) LDAP connections. The second of these ensures that an
6765 encrypted TLS connection is used.
6766
6767
6768 .section "LDAP quoting" "SECID68"
6769 .cindex "LDAP" "quoting"
6770 Two levels of quoting are required in LDAP queries, the first for LDAP itself
6771 and the second because the LDAP query is represented as a URL. Furthermore,
6772 within an LDAP query, two different kinds of quoting are required. For this
6773 reason, there are two different LDAP-specific quoting operators.
6774
6775 The &%quote_ldap%& operator is designed for use on strings that are part of
6776 filter specifications. Conceptually, it first does the following conversions on
6777 the string:
6778 .code
6779 * => \2A
6780 ( => \28
6781 ) => \29
6782 \ => \5C
6783 .endd
6784 in accordance with RFC 2254. The resulting string is then quoted according
6785 to the rules for URLs, that is, all non-alphanumeric characters except
6786 .code
6787 ! $ ' - . _ ( ) * +
6788 .endd
6789 are converted to their hex values, preceded by a percent sign. For example:
6790 .code
6791 ${quote_ldap: a(bc)*, a<yz>; }
6792 .endd
6793 yields
6794 .code
6795 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
6796 .endd
6797 Removing the URL quoting, this is (with a leading and a trailing space):
6798 .code
6799 a\28bc\29\2A, a<yz>;
6800 .endd
6801 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
6802 base DN specifications in queries. Conceptually, it first converts the string
6803 by inserting a backslash in front of any of the following characters:
6804 .code
6805 , + " \ < > ;
6806 .endd
6807 It also inserts a backslash before any leading spaces or # characters, and
6808 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
6809 is then quoted according to the rules for URLs. For example:
6810 .code
6811 ${quote_ldap_dn: a(bc)*, a<yz>; }
6812 .endd
6813 yields
6814 .code
6815 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
6816 .endd
6817 Removing the URL quoting, this is (with a trailing space):
6818 .code
6819 \ a(bc)*\, a\<yz\>\;\
6820 .endd
6821 There are some further comments about quoting in the section on LDAP
6822 authentication below.
6823
6824
6825 .section "LDAP connections" "SECID69"
6826 .cindex "LDAP" "connections"
6827 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
6828 is in use, via a Unix domain socket. The example given above does not specify
6829 an LDAP server. A server that is reached by TCP/IP can be specified in a query
6830 by starting it with
6831 .code
6832 ldap://<hostname>:<port>/...
6833 .endd
6834 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
6835 used. When no server is specified in a query, a list of default servers is
6836 taken from the &%ldap_default_servers%& configuration option. This supplies a
6837 colon-separated list of servers which are tried in turn until one successfully
6838 handles a query, or there is a serious error. Successful handling either
6839 returns the requested data, or indicates that it does not exist. Serious errors
6840 are syntactical, or multiple values when only a single value is expected.
6841 Errors which cause the next server to be tried are connection failures, bind
6842 failures, and timeouts.
6843
6844 For each server name in the list, a port number can be given. The standard way
6845 of specifying a host and port is to use a colon separator (RFC 1738). Because
6846 &%ldap_default_servers%& is a colon-separated list, such colons have to be
6847 doubled. For example
6848 .code
6849 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
6850 .endd
6851 If &%ldap_default_servers%& is unset, a URL with no server name is passed
6852 to the LDAP library with no server name, and the library's default (normally
6853 the local host) is used.
6854
6855 If you are using the OpenLDAP library, you can connect to an LDAP server using
6856 a Unix domain socket instead of a TCP/IP connection. This is specified by using
6857 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
6858 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
6859 not available.
6860
6861 For this type of connection, instead of a host name for the server, a pathname
6862 for the socket is required, and the port number is not relevant. The pathname
6863 can be specified either as an item in &%ldap_default_servers%&, or inline in
6864 the query. In the former case, you can have settings such as
6865 .code
6866 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
6867 .endd
6868 When the pathname is given in the query, you have to escape the slashes as
6869 &`%2F`& to fit in with the LDAP URL syntax. For example:
6870 .code
6871 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
6872 .endd
6873 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
6874 a pathname, it uses the Unix domain socket code, even if the query actually
6875 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
6876 socket connection. This behaviour means that you can use a setting of
6877 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
6878 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
6879 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
6880 backup host.
6881
6882 If an explicit &`ldapi`& type is given in a query when a host name is
6883 specified, an error is diagnosed. However, if there are more items in
6884 &%ldap_default_servers%&, they are tried. In other words:
6885
6886 .ilist
6887 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
6888 interface.
6889 .next
6890 Using &`ldapi`& with a host name causes an error.
6891 .endlist
6892
6893
6894 Using &`ldapi`& with no host or path in the query, and no setting of
6895 &%ldap_default_servers%&, does whatever the library does by default.
6896
6897
6898
6899 .section "LDAP authentication and control information" "SECID70"
6900 .cindex "LDAP" "authentication"
6901 The LDAP URL syntax provides no way of passing authentication and other control
6902 information to the server. To make this possible, the URL in an LDAP query may
6903 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
6904 spaces. If a value contains spaces it must be enclosed in double quotes, and
6905 when double quotes are used, backslash is interpreted in the usual way inside
6906 them. The following names are recognized:
6907 .display
6908 &`DEREFERENCE`& set the dereferencing parameter
6909 &`NETTIME `& set a timeout for a network operation
6910 &`USER `& set the DN, for authenticating the LDAP bind
6911 &`PASS `& set the password, likewise
6912 &`REFERRALS `& set the referrals parameter
6913 &`SIZE `& set the limit for the number of entries returned
6914 &`TIME `& set the maximum waiting time for a query
6915 .endd
6916 The value of the DEREFERENCE parameter must be one of the words &"never"&,
6917 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
6918 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
6919 library from trying to follow referrals issued by the LDAP server.
6920
6921 The name CONNECT is an obsolete name for NETTIME, retained for
6922 backwards compatibility. This timeout (specified as a number of seconds) is
6923 enforced from the client end for operations that can be carried out over a
6924 network. Specifically, it applies to network connections and calls to the
6925 &'ldap_result()'& function. If the value is greater than zero, it is used if
6926 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
6927 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
6928 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
6929 Netscape SDK; for OpenLDAP no action is taken.
6930
6931 The TIME parameter (also a number of seconds) is passed to the server to
6932 set a server-side limit on the time taken to complete a search.
6933
6934
6935 Here is an example of an LDAP query in an Exim lookup that uses some of these
6936 values. This is a single line, folded to fit on the page:
6937 .code
6938 ${lookup ldap
6939 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
6940 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
6941 {$value}fail}
6942 .endd
6943 The encoding of spaces as &`%20`& is a URL thing which should not be done for
6944 any of the auxiliary data. Exim configuration settings that include lookups
6945 which contain password information should be preceded by &"hide"& to prevent
6946 non-admin users from using the &%-bP%& option to see their values.
6947
6948 The auxiliary data items may be given in any order. The default is no
6949 connection timeout (the system timeout is used), no user or password, no limit
6950 on the number of entries returned, and no time limit on queries.
6951
6952 When a DN is quoted in the USER= setting for LDAP authentication, Exim
6953 removes any URL quoting that it may contain before passing it LDAP. Apparently
6954 some libraries do this for themselves, but some do not. Removing the URL
6955 quoting has two advantages:
6956
6957 .ilist
6958 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
6959 DNs as with DNs inside actual queries.
6960 .next
6961 It permits spaces inside USER= DNs.
6962 .endlist
6963
6964 For example, a setting such as
6965 .code
6966 USER=cn=${quote_ldap_dn:$1}
6967 .endd
6968 should work even if &$1$& contains spaces.
6969
6970 Expanded data for the PASS= value should be quoted using the &%quote%&
6971 expansion operator, rather than the LDAP quote operators. The only reason this
6972 field needs quoting is to ensure that it conforms to the Exim syntax, which
6973 does not allow unquoted spaces. For example:
6974 .code
6975 PASS=${quote:$3}
6976 .endd
6977 The LDAP authentication mechanism can be used to check passwords as part of
6978 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
6979 &<<CHAPexpand>>&.
6980
6981
6982
6983 .section "Format of data returned by LDAP" "SECID71"
6984 .cindex "LDAP" "returned data formats"
6985 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
6986 as a sequence of values, for example
6987 .code
6988 cn=manager, o=University of Cambridge, c=UK
6989 .endd
6990 The &(ldap)& lookup type generates an error if more than one entry matches the
6991 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
6992 the result between the data from different entries. It is possible for multiple
6993 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
6994 you know that whatever values are returned all came from a single entry in the
6995 directory.
6996
6997 In the common case where you specify a single attribute in your LDAP query, the
6998 result is not quoted, and does not contain the attribute name. If the attribute
6999 has multiple values, they are separated by commas.
7000
7001 If you specify multiple attributes, the result contains space-separated, quoted
7002 strings, each preceded by the attribute name and an equals sign. Within the
7003 quotes, the quote character, backslash, and newline are escaped with
7004 backslashes, and commas are used to separate multiple values for the attribute.
7005 Apart from the escaping, the string within quotes takes the same form as the
7006 output when a single attribute is requested. Specifying no attributes is the
7007 same as specifying all of an entry's attributes.
7008
7009 Here are some examples of the output format. The first line of each pair is an
7010 LDAP query, and the second is the data that is returned. The attribute called
7011 &%attr1%& has two values, whereas &%attr2%& has only one value:
7012 .code
7013 ldap:///o=base?attr1?sub?(uid=fred)
7014 value1.1, value1.2
7015
7016 ldap:///o=base?attr2?sub?(uid=fred)
7017 value two
7018
7019 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7020 attr1="value1.1, value1.2" attr2="value two"
7021
7022 ldap:///o=base??sub?(uid=fred)
7023 objectClass="top" attr1="value1.1, value1.2" attr2="value two"
7024 .endd
7025 The &%extract%& operator in string expansions can be used to pick out
7026 individual fields from data that consists of &'key'&=&'value'& pairs. You can
7027 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7028 results of LDAP lookups.
7029
7030
7031
7032
7033 .section "More about NIS+" "SECTnisplus"
7034 .cindex "NIS+ lookup type"
7035 .cindex "lookup" "NIS+"
7036 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7037 and field name. If this is given, the result of a successful query is the
7038 contents of the named field; otherwise the result consists of a concatenation
7039 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
7040 values containing spaces are quoted. For example, the query
7041 .code
7042 [name=mg1456],passwd.org_dir
7043 .endd
7044 might return the string
7045 .code
7046 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
7047 home=/home/mg1456 shell=/bin/bash shadow=""
7048 .endd
7049 (split over two lines here to fit on the page), whereas
7050 .code
7051 [name=mg1456],passwd.org_dir:gcos
7052 .endd
7053 would just return
7054 .code
7055 Martin Guerre
7056 .endd
7057 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
7058 for the given indexed key. The effect of the &%quote_nisplus%& expansion
7059 operator is to double any quote characters within the text.
7060
7061
7062
7063 .section "SQL lookups" "SECTsql"
7064 .cindex "SQL lookup types"
7065 .cindex "MySQL" "lookup type"
7066 .cindex "PostgreSQL lookup type"
7067 .cindex "lookup" "MySQL"
7068 .cindex "lookup" "PostgreSQL"
7069 .cindex "Oracle" "lookup type"
7070 .cindex "lookup" "Oracle"
7071 .cindex "InterBase lookup type"
7072 .cindex "lookup" "InterBase"
7073 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, and SQLite
7074 databases. Queries for these databases contain SQL statements, so an example
7075 might be
7076 .code
7077 ${lookup mysql{select mailbox from users where id='userx'}\
7078 {$value}fail}
7079 .endd
7080 If the result of the query contains more than one field, the data for each
7081 field in the row is returned, preceded by its name, so the result of
7082 .code
7083 ${lookup pgsql{select home,name from users where id='userx'}\
7084 {$value}}
7085 .endd
7086 might be
7087 .code
7088 home=/home/userx name="Mister X"
7089 .endd
7090 Empty values and values containing spaces are double quoted, with embedded
7091 quotes escaped by a backslash. If the result of the query contains just one
7092 field, the value is passed back verbatim, without a field name, for example:
7093 .code
7094 Mister X
7095 .endd
7096 If the result of the query yields more than one row, it is all concatenated,
7097 with a newline between the data for each row.
7098
7099
7100 .section "More about MySQL, PostgreSQL, Oracle, and InterBase" "SECID72"
7101 .cindex "MySQL" "lookup type"
7102 .cindex "PostgreSQL lookup type"
7103 .cindex "lookup" "MySQL"
7104 .cindex "lookup" "PostgreSQL"
7105 .cindex "Oracle" "lookup type"
7106 .cindex "lookup" "Oracle"
7107 .cindex "InterBase lookup type"
7108 .cindex "lookup" "InterBase"
7109 If any MySQL, PostgreSQL, Oracle, or InterBase lookups are used, the
7110 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, or &%ibase_servers%&
7111 option (as appropriate) must be set to a colon-separated list of server
7112 information.
7113 (For MySQL and PostgreSQL only, the global option need not be set if all
7114 queries contain their own server information &-- see section
7115 &<<SECTspeserque>>&.) Each item in the list is a slash-separated list of four
7116 items: host name, database name, user name, and password. In the case of
7117 Oracle, the host name field is used for the &"service name"&, and the database
7118 name field is not used and should be empty. For example:
7119 .code
7120 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
7121 .endd
7122 Because password data is sensitive, you should always precede the setting with
7123 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
7124 option. Here is an example where two MySQL servers are listed:
7125 .code
7126 hide mysql_servers = localhost/users/root/secret:\
7127 otherhost/users/root/othersecret
7128 .endd
7129 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
7130 because this is a colon-separated list, the colon has to be doubled. For each
7131 query, these parameter groups are tried in order until a connection is made and
7132 a query is successfully processed. The result of a query may be that no data is
7133 found, but that is still a successful query. In other words, the list of
7134 servers provides a backup facility, not a list of different places to look.
7135
7136 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
7137 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
7138 respectively, and the characters single-quote, double-quote, and backslash
7139 itself are escaped with backslashes. The &%quote_pgsql%& expansion operator, in
7140 addition, escapes the percent and underscore characters. This cannot be done
7141 for MySQL because these escapes are not recognized in contexts where these
7142 characters are not special.
7143
7144 .section "Specifying the server in the query" "SECTspeserque"
7145 For MySQL and PostgreSQL lookups (but not currently for Oracle and InterBase),
7146 it is possible to specify a list of servers with an individual query. This is
7147 done by starting the query with
7148 .display
7149 &`servers=`&&'server1:server2:server3:...'&&`;`&
7150 .endd
7151 Each item in the list may take one of two forms:
7152 .olist
7153 If it contains no slashes it is assumed to be just a host name. The appropriate
7154 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
7155 of the same name, and the remaining parameters (database, user, password) are
7156 taken from there.
7157 .next
7158 If it contains any slashes, it is taken as a complete parameter set.
7159 .endlist
7160 The list of servers is used in exactly the same way as the global list.
7161 Once a connection to a server has happened and a query has been
7162 successfully executed, processing of the lookup ceases.
7163
7164 This feature is intended for use in master/slave situations where updates
7165 are occurring and you want to update the master rather than a slave. If the
7166 master is in the list as a backup for reading, you might have a global setting
7167 like this:
7168 .code
7169 mysql_servers = slave1/db/name/pw:\
7170 slave2/db/name/pw:\
7171 master/db/name/pw
7172 .endd
7173 In an updating lookup, you could then write:
7174 .code
7175 ${lookup mysql{servers=master; UPDATE ...}
7176 .endd
7177 That query would then be sent only to the master server. If, on the other hand,
7178 the master is not to be used for reading, and so is not present in the global
7179 option, you can still update it by a query of this form:
7180 .code
7181 ${lookup pgsql{servers=master/db/name/pw; UPDATE ...}
7182 .endd
7183
7184
7185 .section "Special MySQL features" "SECID73"
7186 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
7187 causes a connection to the server on the local host by means of a Unix domain
7188 socket. An alternate socket can be specified in parentheses. The full syntax of
7189 each item in &%mysql_servers%& is:
7190 .display
7191 <&'hostname'&>::<&'port'&>(<&'socket name'&>)/<&'database'&>/&&&
7192 <&'user'&>/<&'password'&>
7193 .endd
7194 Any of the three sub-parts of the first field can be omitted. For normal use on
7195 the local host it can be left blank or set to just &"localhost"&.
7196
7197 No database need be supplied &-- but if it is absent here, it must be given in
7198 the queries.
7199
7200 If a MySQL query is issued that does not request any data (an insert, update,
7201 or delete command), the result of the lookup is the number of rows affected.
7202
7203 &*Warning*&: This can be misleading. If an update does not actually change
7204 anything (for example, setting a field to the value it already has), the result
7205 is zero because no rows are affected.
7206
7207
7208 .section "Special PostgreSQL features" "SECID74"
7209 PostgreSQL lookups can also use Unix domain socket connections to the database.
7210 This is usually faster and costs less CPU time than a TCP/IP connection.
7211 However it can be used only if the mail server runs on the same machine as the
7212 database server. A configuration line for PostgreSQL via Unix domain sockets
7213 looks like this:
7214 .code
7215 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
7216 .endd
7217 In other words, instead of supplying a host name, a path to the socket is
7218 given. The path name is enclosed in parentheses so that its slashes aren't
7219 visually confused with the delimiters for the other server parameters.
7220
7221 If a PostgreSQL query is issued that does not request any data (an insert,
7222 update, or delete command), the result of the lookup is the number of rows
7223 affected.
7224
7225 .section "More about SQLite" "SECTsqlite"
7226 .cindex "lookup" "SQLite"
7227 .cindex "sqlite lookup type"
7228 SQLite is different to the other SQL lookups because a file name is required in
7229 addition to the SQL query. An SQLite database is a single file, and there is no
7230 daemon as in the other SQL databases. The interface to Exim requires the name
7231 of the file, as an absolute path, to be given at the start of the query. It is
7232 separated from the query by white space. This means that the path name cannot
7233 contain white space. Here is a lookup expansion example:
7234 .code
7235 ${lookup sqlite {/some/thing/sqlitedb \
7236 select name from aliases where id='userx';}}
7237 .endd
7238 In a list, the syntax is similar. For example:
7239 .code
7240 domainlist relay_domains = sqlite;/some/thing/sqlitedb \
7241 select * from relays where ip='$sender_host_address';
7242 .endd
7243 The only character affected by the &%quote_sqlite%& operator is a single
7244 quote, which it doubles.
7245
7246 The SQLite library handles multiple simultaneous accesses to the database
7247 internally. Multiple readers are permitted, but only one process can
7248 update at once. Attempts to access the database while it is being updated
7249 are rejected after a timeout period, during which the SQLite library
7250 waits for the lock to be released. In Exim, the default timeout is set
7251 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
7252 option.
7253 .ecindex IIDfidalo1
7254 .ecindex IIDfidalo2
7255
7256
7257 . ////////////////////////////////////////////////////////////////////////////
7258 . ////////////////////////////////////////////////////////////////////////////
7259
7260 .chapter "Domain, host, address, and local part lists" &&&
7261 "CHAPdomhosaddlists" &&&
7262 "Domain, host, and address lists"
7263 .scindex IIDdohoadli "lists of domains; hosts; etc."
7264 A number of Exim configuration options contain lists of domains, hosts,
7265 email addresses, or local parts. For example, the &%hold_domains%& option
7266 contains a list of domains whose delivery is currently suspended. These lists
7267 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
7268 arguments to expansion conditions such as &%match_domain%&.
7269
7270 Each item in one of these lists is a pattern to be matched against a domain,
7271 host, email address, or local part, respectively. In the sections below, the
7272 different types of pattern for each case are described, but first we cover some
7273 general facilities that apply to all four kinds of list.
7274
7275
7276
7277 .section "Expansion of lists" "SECID75"
7278 .cindex "expansion" "of lists"
7279 Each list is expanded as a single string before it is used. The result of
7280 expansion must be a list, possibly containing empty items, which is split up
7281 into separate items for matching. By default, colon is the separator character,
7282 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
7283 &<<SECTempitelis>>& for details of the list syntax; the second of these
7284 discusses the way to specify empty list items.
7285
7286
7287 If the string expansion is forced to fail, Exim behaves as if the item it is
7288 testing (domain, host, address, or local part) is not in the list. Other
7289 expansion failures cause temporary errors.
7290
7291 If an item in a list is a regular expression, backslashes, dollars and possibly
7292 other special characters in the expression must be protected against
7293 misinterpretation by the string expander. The easiest way to do this is to use
7294 the &`\N`& expansion feature to indicate that the contents of the regular
7295 expression should not be expanded. For example, in an ACL you might have:
7296 .code
7297 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
7298 ${lookup{$domain}lsearch{/badsenders/bydomain}}
7299 .endd
7300 The first item is a regular expression that is protected from expansion by
7301 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
7302 senders based on the receiving domain.
7303
7304
7305
7306
7307 .section "Negated items in lists" "SECID76"
7308 .cindex "list" "negation"
7309 .cindex "negation" "in lists"
7310 Items in a list may be positive or negative. Negative items are indicated by a
7311 leading exclamation mark, which may be followed by optional white space. A list
7312 defines a set of items (domains, etc). When Exim processes one of these lists,
7313 it is trying to find out whether a domain, host, address, or local part
7314 (respectively) is in the set that is defined by the list. It works like this:
7315
7316 The list is scanned from left to right. If a positive item is matched, the
7317 subject that is being checked is in the set; if a negative item is matched, the
7318 subject is not in the set. If the end of the list is reached without the
7319 subject having matched any of the patterns, it is in the set if the last item
7320 was a negative one, but not if it was a positive one. For example, the list in
7321 .code
7322 domainlist relay_domains = !a.b.c : *.b.c
7323 .endd
7324 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
7325 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
7326 list is positive. However, if the setting were
7327 .code
7328 domainlist relay_domains = !a.b.c
7329 .endd
7330 then all domains other than &'a.b.c'& would match because the last item in the
7331 list is negative. In other words, a list that ends with a negative item behaves
7332 as if it had an extra item &`:*`& on the end.
7333
7334 Another way of thinking about positive and negative items in lists is to read
7335 the connector as &"or"& after a positive item and as &"and"& after a negative
7336 item.
7337
7338
7339
7340 .section "File names in lists" "SECTfilnamlis"
7341 .cindex "list" "file name in"
7342 If an item in a domain, host, address, or local part list is an absolute file
7343 name (beginning with a slash character), each line of the file is read and
7344 processed as if it were an independent item in the list, except that further
7345 file names are not allowed,
7346 and no expansion of the data from the file takes place.
7347 Empty lines in the file are ignored, and the file may also contain comment
7348 lines:
7349
7350 .ilist
7351 For domain and host lists, if a # character appears anywhere in a line of the
7352 file, it and all following characters are ignored.
7353 .next
7354 Because local parts may legitimately contain # characters, a comment in an
7355 address list or local part list file is recognized only if # is preceded by
7356 white space or the start of the line. For example:
7357 .code
7358 not#comment@x.y.z # but this is a comment
7359 .endd
7360 .endlist
7361
7362 Putting a file name in a list has the same effect as inserting each line of the
7363 file as an item in the list (blank lines and comments excepted). However, there
7364 is one important difference: the file is read each time the list is processed,
7365 so if its contents vary over time, Exim's behaviour changes.
7366
7367 If a file name is preceded by an exclamation mark, the sense of any match
7368 within the file is inverted. For example, if
7369 .code
7370 hold_domains = !/etc/nohold-domains
7371 .endd
7372 and the file contains the lines
7373 .code
7374 !a.b.c
7375 *.b.c
7376 .endd
7377 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
7378 any domain matching &`*.b.c`& is not.
7379
7380
7381
7382 .section "An lsearch file is not an out-of-line list" "SECID77"
7383 As will be described in the sections that follow, lookups can be used in lists
7384 to provide indexed methods of checking list membership. There has been some
7385 confusion about the way &(lsearch)& lookups work in lists. Because
7386 an &(lsearch)& file contains plain text and is scanned sequentially, it is
7387 sometimes thought that it is allowed to contain wild cards and other kinds of
7388 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
7389 always fixed strings, just as for any other single-key lookup type.
7390
7391 If you want to use a file to contain wild-card patterns that form part of a
7392 list, just give the file name on its own, without a search type, as described
7393 in the previous section. You could also use the &(wildlsearch)& or
7394 &(nwildlsearch)&, but there is no advantage in doing this.
7395
7396
7397
7398
7399 .section "Named lists" "SECTnamedlists"
7400 .cindex "named lists"
7401 .cindex "list" "named"
7402 A list of domains, hosts, email addresses, or local parts can be given a name
7403 which is then used to refer to the list elsewhere in the configuration. This is
7404 particularly convenient if the same list is required in several different
7405 places. It also allows lists to be given meaningful names, which can improve
7406 the readability of the configuration. For example, it is conventional to define
7407 a domain list called &'local_domains'& for all the domains that are handled
7408 locally on a host, using a configuration line such as
7409 .code
7410 domainlist local_domains = localhost:my.dom.example
7411 .endd
7412 Named lists are referenced by giving their name preceded by a plus sign, so,
7413 for example, a router that is intended to handle local domains would be
7414 configured with the line
7415 .code
7416 domains = +local_domains
7417 .endd
7418 The first router in a configuration is often one that handles all domains
7419 except the local ones, using a configuration with a negated item like this:
7420 .code
7421 dnslookup:
7422 driver = dnslookup
7423 domains = ! +local_domains
7424 transport = remote_smtp
7425 no_more
7426 .endd
7427 The four kinds of named list are created by configuration lines starting with
7428 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
7429 respectively. Then there follows the name that you are defining, followed by an
7430 equals sign and the list itself. For example:
7431 .code
7432 hostlist relay_hosts = 192.168.23.0/24 : my.friend.example
7433 addresslist bad_senders = cdb;/etc/badsenders
7434 .endd
7435 A named list may refer to other named lists:
7436 .code
7437 domainlist dom1 = first.example : second.example
7438 domainlist dom2 = +dom1 : third.example
7439 domainlist dom3 = fourth.example : +dom2 : fifth.example
7440 .endd
7441 &*Warning*&: If the last item in a referenced list is a negative one, the
7442 effect may not be what you intended, because the negation does not propagate
7443 out to the higher level. For example, consider:
7444 .code
7445 domainlist dom1 = !a.b
7446 domainlist dom2 = +dom1 : *.b
7447 .endd
7448 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
7449 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
7450 means it matches the second list as well. The effect is not the same as
7451 .code
7452 domainlist dom2 = !a.b : *.b
7453 .endd
7454 where &'x.y'& does not match. It's best to avoid negation altogether in
7455 referenced lists if you can.
7456
7457 Named lists may have a performance advantage. When Exim is routing an
7458 address or checking an incoming message, it caches the result of tests on named
7459 lists. So, if you have a setting such as
7460 .code
7461 domains = +local_domains
7462 .endd
7463 on several of your routers
7464 or in several ACL statements,
7465 the actual test is done only for the first one. However, the caching works only
7466 if there are no expansions within the list itself or any sublists that it
7467 references. In other words, caching happens only for lists that are known to be
7468 the same each time they are referenced.
7469
7470 By default, there may be up to 16 named lists of each type. This limit can be
7471 extended by changing a compile-time variable. The use of domain and host lists
7472 is recommended for concepts such as local domains, relay domains, and relay
7473 hosts. The default configuration is set up like this.
7474
7475
7476
7477 .section "Named lists compared with macros" "SECID78"
7478 .cindex "list" "named compared with macro"
7479 .cindex "macro" "compared with named list"
7480 At first sight, named lists might seem to be no different from macros in the
7481 configuration file. However, macros are just textual substitutions. If you
7482 write
7483 .code
7484 ALIST = host1 : host2
7485 auth_advertise_hosts = !ALIST
7486 .endd
7487 it probably won't do what you want, because that is exactly the same as
7488 .code
7489 auth_advertise_hosts = !host1 : host2
7490 .endd
7491 Notice that the second host name is not negated. However, if you use a host
7492 list, and write
7493 .code
7494 hostlist alist = host1 : host2
7495 auth_advertise_hosts = ! +alist
7496 .endd
7497 the negation applies to the whole list, and so that is equivalent to
7498 .code
7499 auth_advertise_hosts = !host1 : !host2
7500 .endd
7501
7502
7503 .section "Named list caching" "SECID79"
7504 .cindex "list" "caching of named"
7505 .cindex "caching" "named lists"
7506 While processing a message, Exim caches the result of checking a named list if
7507 it is sure that the list is the same each time. In practice, this means that
7508 the cache operates only if the list contains no $ characters, which guarantees
7509 that it will not change when it is expanded. Sometimes, however, you may have
7510 an expanded list that you know will be the same each time within a given
7511 message. For example:
7512 .code
7513 domainlist special_domains = \
7514 ${lookup{$sender_host_address}cdb{/some/file}}
7515 .endd
7516 This provides a list of domains that depends only on the sending host's IP
7517 address. If this domain list is referenced a number of times (for example,
7518 in several ACL lines, or in several routers) the result of the check is not
7519 cached by default, because Exim does not know that it is going to be the
7520 same list each time.
7521
7522 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
7523 cache the result anyway. For example:
7524 .code
7525 domainlist_cache special_domains = ${lookup{...
7526 .endd
7527 If you do this, you should be absolutely sure that caching is going to do
7528 the right thing in all cases. When in doubt, leave it out.
7529
7530
7531
7532 .section "Domain lists" "SECTdomainlist"
7533 .cindex "domain list" "patterns for"
7534 .cindex "list" "domain list"
7535 Domain lists contain patterns that are to be matched against a mail domain.
7536 The following types of item may appear in domain lists:
7537
7538 .ilist
7539 .cindex "primary host name"
7540 .cindex "host name" "matched in domain list"
7541 .oindex "&%primary_hostname%&"
7542 .cindex "domain list" "matching primary host name"
7543 .cindex "@ in a domain list"
7544 If a pattern consists of a single @ character, it matches the local host name,
7545 as set by the &%primary_hostname%& option (or defaulted). This makes it
7546 possible to use the same configuration file on several different hosts that
7547 differ only in their names.
7548 .next
7549 .cindex "@[] in a domain list"
7550 .cindex "domain list" "matching local IP interfaces"
7551 .cindex "domain literal"
7552 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
7553 in square brackets (as in an email address that contains a domain literal), but
7554 only if that IP address is recognized as local for email routing purposes. The
7555 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
7556 control which of a host's several IP addresses are treated as local.
7557 In today's Internet, the use of domain literals is controversial.
7558 .next
7559 .cindex "@mx_any"
7560 .cindex "@mx_primary"
7561 .cindex "@mx_secondary"
7562 .cindex "domain list" "matching MX pointers to local host"
7563 If a pattern consists of the string &`@mx_any`& it matches any domain that
7564 has an MX record pointing to the local host or to any host that is listed in
7565 .oindex "&%hosts_treat_as_local%&"
7566 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
7567 are similar, except that the first matches only when a primary MX target is the
7568 local host, and the second only when no primary MX target is the local host,
7569 but a secondary MX target is. &"Primary"& means an MX record with the lowest
7570 preference value &-- there may of course be more than one of them.
7571
7572 The MX lookup that takes place when matching a pattern of this type is
7573 performed with the resolver options for widening names turned off. Thus, for
7574 example, a single-component domain will &'not'& be expanded by adding the
7575 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
7576 options of the &(dnslookup)& router for a discussion of domain widening.
7577
7578 Sometimes you may want to ignore certain IP addresses when using one of these
7579 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
7580 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
7581 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
7582 on a router). For example:
7583 .code
7584 domains = @mx_any/ignore=127.0.0.1
7585 .endd
7586 This example matches any domain that has an MX record pointing to one of
7587 the local host's IP addresses other than 127.0.0.1.
7588
7589 The list of IP addresses is in fact processed by the same code that processes
7590 host lists, so it may contain CIDR-coded network specifications and it may also
7591 contain negative items.
7592
7593 Because the list of IP addresses is a sublist within a domain list, you have to
7594 be careful about delimiters if there is more than one address. Like any other
7595 list, the default delimiter can be changed. Thus, you might have:
7596 .code
7597 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
7598 an.other.domain : ...
7599 .endd
7600 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
7601 involved, it is easiest to change the delimiter for the main list as well:
7602 .code
7603 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
7604 an.other.domain ? ...
7605 .endd
7606 .next
7607 .cindex "asterisk" "in domain list"
7608 .cindex "domain list" "asterisk in"
7609 .cindex "domain list" "matching &""ends with""&"
7610 If a pattern starts with an asterisk, the remaining characters of the pattern
7611 are compared with the terminating characters of the domain. The use of &"*"& in
7612 domain lists differs from its use in partial matching lookups. In a domain
7613 list, the character following the asterisk need not be a dot, whereas partial
7614 matching works only in terms of dot-separated components. For example, a domain
7615 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
7616 &'cipher.key.ex'&.
7617
7618 .next
7619 .cindex "regular expressions" "in domain list"
7620 .cindex "domain list" "matching regular expression"
7621 If a pattern starts with a circumflex character, it is treated as a regular
7622 expression, and matched against the domain using a regular expression matching
7623 function. The circumflex is treated as part of the regular expression.
7624 Email domains are case-independent, so this regular expression match is by
7625 default case-independent, but you can make it case-dependent by starting it
7626 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
7627 are given in chapter &<<CHAPregexp>>&.
7628
7629 &*Warning*&: Because domain lists are expanded before being processed, you
7630 must escape any backslash and dollar characters in the regular expression, or
7631 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
7632 it is not to be expanded (unless you really do want to build a regular
7633 expression by expansion, of course).
7634 .next
7635 .cindex "lookup" "in domain list"
7636 .cindex "domain list" "matching by lookup"
7637 If a pattern starts with the name of a single-key lookup type followed by a
7638 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
7639 must be a file name in a suitable format for the lookup type. For example, for
7640 &"cdb;"& it must be an absolute path:
7641 .code
7642 domains = cdb;/etc/mail/local_domains.cdb
7643 .endd
7644 The appropriate type of lookup is done on the file using the domain name as the
7645 key. In most cases, the data that is looked up is not used; Exim is interested
7646 only in whether or not the key is present in the file. However, when a lookup
7647 is used for the &%domains%& option on a router
7648 or a &%domains%& condition in an ACL statement, the data is preserved in the
7649 &$domain_data$& variable and can be referred to in other router options or
7650 other statements in the same ACL.
7651
7652 .next
7653 Any of the single-key lookup type names may be preceded by
7654 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
7655 .code
7656 domains = partial-dbm;/partial/domains
7657 .endd
7658 This causes partial matching logic to be invoked; a description of how this
7659 works is given in section &<<SECTpartiallookup>>&.
7660
7661 .next
7662 .cindex "asterisk" "in lookup type"
7663 Any of the single-key lookup types may be followed by an asterisk. This causes
7664 a default lookup for a key consisting of a single asterisk to be done if the
7665 original lookup fails. This is not a useful feature when using a domain list to
7666 select particular domains (because any domain would match), but it might have
7667 value if the result of the lookup is being used via the &$domain_data$&
7668 expansion variable.
7669 .next
7670 If the pattern starts with the name of a query-style lookup type followed by a
7671 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
7672 pattern must be an appropriate query for the lookup type, as described in
7673 chapter &<<CHAPfdlookup>>&. For example:
7674 .code
7675 hold_domains = mysql;select domain from holdlist \
7676 where domain = '$domain';
7677 .endd
7678 In most cases, the data that is looked up is not used (so for an SQL query, for
7679 example, it doesn't matter what field you select). Exim is interested only in
7680 whether or not the query succeeds. However, when a lookup is used for the
7681 &%domains%& option on a router, the data is preserved in the &$domain_data$&
7682 variable and can be referred to in other options.
7683 .next
7684 .cindex "domain list" "matching literal domain name"
7685 If none of the above cases apply, a caseless textual comparison is made
7686 between the pattern and the domain.
7687 .endlist
7688
7689 Here is an example that uses several different kinds of pattern:
7690 .code
7691 domainlist funny_domains = \
7692 @ : \
7693 lib.unseen.edu : \
7694 *.foundation.fict.example : \
7695 \N^[1-2]\d{3}\.fict\.example$\N : \
7696 partial-dbm;/opt/data/penguin/book : \
7697 nis;domains.byname : \
7698 nisplus;[name=$domain,status=local],domains.org_dir
7699 .endd
7700 There are obvious processing trade-offs among the various matching modes. Using
7701 an asterisk is faster than a regular expression, and listing a few names
7702 explicitly probably is too. The use of a file or database lookup is expensive,
7703 but may be the only option if hundreds of names are required. Because the
7704 patterns are tested in order, it makes sense to put the most commonly matched
7705 patterns earlier.
7706
7707
7708
7709 .section "Host lists" "SECThostlist"
7710 .cindex "host list" "patterns in"
7711 .cindex "list" "host list"
7712 Host lists are used to control what remote hosts are allowed to do. For
7713 example, some hosts may be allowed to use the local host as a relay, and some
7714 may be permitted to use the SMTP ETRN command. Hosts can be identified in
7715 two different ways, by name or by IP address. In a host list, some types of
7716 pattern are matched to a host name, and some are matched to an IP address.
7717 You need to be particularly careful with this when single-key lookups are
7718 involved, to ensure that the right value is being used as the key.
7719
7720
7721 .section "Special host list patterns" "SECID80"
7722 .cindex "empty item in hosts list"
7723 .cindex "host list" "empty string in"
7724 If a host list item is the empty string, it matches only when no remote host is
7725 involved. This is the case when a message is being received from a local
7726 process using SMTP on the standard input, that is, when a TCP/IP connection is
7727 not used.
7728
7729 .cindex "asterisk" "in host list"
7730 The special pattern &"*"& in a host list matches any host or no host. Neither
7731 the IP address nor the name is actually inspected.
7732
7733
7734
7735 .section "Host list patterns that match by IP address" "SECThoslispatip"
7736 .cindex "host list" "matching IP addresses"
7737 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
7738 the incoming address actually appears in the IPv6 host as
7739 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
7740 list, it is converted into a traditional IPv4 address first. (Not all operating
7741 systems accept IPv4 calls on IPv6 sockets, as there have been some security
7742 concerns.)
7743
7744 The following types of pattern in a host list check the remote host by
7745 inspecting its IP address:
7746
7747 .ilist
7748 If the pattern is a plain domain name (not a regular expression, not starting
7749 with *, not a lookup of any kind), Exim calls the operating system function
7750 to find the associated IP address(es). Exim uses the newer
7751 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
7752 This typically causes a forward DNS lookup of the name. The result is compared
7753 with the IP address of the subject host.
7754
7755 If there is a temporary problem (such as a DNS timeout) with the host name
7756 lookup, a temporary error occurs. For example, if the list is being used in an
7757 ACL condition, the ACL gives a &"defer"& response, usually leading to a
7758 temporary SMTP error code. If no IP address can be found for the host name,
7759 what happens is described in section &<<SECTbehipnot>>& below.
7760
7761 .next
7762 .cindex "@ in a host list"
7763 If the pattern is &"@"&, the primary host name is substituted and used as a
7764 domain name, as just described.
7765
7766 .next
7767 If the pattern is an IP address, it is matched against the IP address of the
7768 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
7769 IPv6 addresses can be given in colon-separated format, but the colons have to
7770 be doubled so as not to be taken as item separators when the default list
7771 separator is used. IPv6 addresses are recognized even when Exim is compiled
7772 without IPv6 support. This means that if they appear in a host list on an
7773 IPv4-only host, Exim will not treat them as host names. They are just addresses
7774 that can never match a client host.
7775
7776 .next
7777 .cindex "@[] in a host list"
7778 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
7779 the local host. For example, if the local host is an IPv4 host with one
7780 interface address 10.45.23.56, these two ACL statements have the same effect:
7781 .code
7782 accept hosts = 127.0.0.1 : 10.45.23.56
7783 accept hosts = @[]
7784 .endd
7785 .next
7786 .cindex "CIDR notation"
7787 If the pattern is an IP address followed by a slash and a mask length (for
7788 example 10.11.42.0/24), it is matched against the IP address of the subject
7789 host under the given mask. This allows, an entire network of hosts to be
7790 included (or excluded) by a single item. The mask uses CIDR notation; it
7791 specifies the number of address bits that must match, starting from the most
7792 significant end of the address.
7793
7794 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
7795 of a range of addresses. It is the number of bits in the network portion of the
7796 address. The above example specifies a 24-bit netmask, so it matches all 256
7797 addresses in the 10.11.42.0 network. An item such as
7798 .code
7799 192.168.23.236/31
7800 .endd
7801 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
7802 32 for an IPv4 address is the same as no mask at all; just a single address
7803 matches.
7804
7805 Here is another example which shows an IPv4 and an IPv6 network:
7806 .code
7807 recipient_unqualified_hosts = 192.168.0.0/16: \
7808 3ffe::ffff::836f::::/48
7809 .endd
7810 The doubling of list separator characters applies only when these items
7811 appear inline in a host list. It is not required when indirecting via a file.
7812 For example:
7813 .code
7814 recipient_unqualified_hosts = /opt/exim/unqualnets
7815 .endd
7816 could make use of a file containing
7817 .code
7818 172.16.0.0/12
7819 3ffe:ffff:836f::/48
7820 .endd
7821 to have exactly the same effect as the previous example. When listing IPv6
7822 addresses inline, it is usually more convenient to use the facility for
7823 changing separator characters. This list contains the same two networks:
7824 .code
7825 recipient_unqualified_hosts = <; 172.16.0.0/12; \
7826 3ffe:ffff:836f::/48
7827 .endd
7828 The separator is changed to semicolon by the leading &"<;"& at the start of the
7829 list.
7830 .endlist
7831
7832
7833
7834 .section "Host list patterns for single-key lookups by host address" &&&
7835 "SECThoslispatsikey"
7836 .cindex "host list" "lookup of IP address"
7837 When a host is to be identified by a single-key lookup of its complete IP
7838 address, the pattern takes this form:
7839 .display
7840 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
7841 .endd
7842 For example:
7843 .code
7844 hosts_lookup = net-cdb;/hosts-by-ip.db
7845 .endd
7846 The text form of the IP address of the subject host is used as the lookup key.
7847 IPv6 addresses are converted to an unabbreviated form, using lower case
7848 letters, with dots as separators because colon is the key terminator in
7849 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
7850 quoting the keys, but this is a facility that was added later.] The data
7851 returned by the lookup is not used.
7852
7853 .cindex "IP address" "masking"
7854 .cindex "host list" "masked IP address"
7855 Single-key lookups can also be performed using masked IP addresses, using
7856 patterns of this form:
7857 .display
7858 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
7859 .endd
7860 For example:
7861 .code
7862 net24-dbm;/networks.db
7863 .endd
7864 The IP address of the subject host is masked using <&'number'&> as the mask
7865 length. A textual string is constructed from the masked value, followed by the
7866 mask, and this is used as the lookup key. For example, if the host's IP address
7867 is 192.168.34.6, the key that is looked up for the above example is
7868 &"192.168.34.0/24"&.
7869
7870 When an IPv6 address is converted to a string, dots are normally used instead
7871 of colons, so that keys in &(lsearch)& files need not contain colons (which
7872 terminate &(lsearch)& keys). This was implemented some time before the ability
7873 to quote keys was made available in &(lsearch)& files. However, the more
7874 recently implemented &(iplsearch)& files do require colons in IPv6 keys
7875 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
7876 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
7877 converted using colons and not dots. In all cases, full, unabbreviated IPv6
7878 addresses are always used.
7879
7880 Ideally, it would be nice to tidy up this anomalous situation by changing to
7881 colons in all cases, given that quoting is now available for &(lsearch)&.
7882 However, this would be an incompatible change that might break some existing
7883 configurations.
7884
7885 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
7886 IPv6 address) is not the same as specifying just &%net-%& without a number. In
7887 the former case the key strings include the mask value, whereas in the latter
7888 case the IP address is used on its own.
7889
7890
7891
7892 .section "Host list patterns that match by host name" "SECThoslispatnam"
7893 .cindex "host" "lookup failures"
7894 .cindex "unknown host name"
7895 .cindex "host list" "matching host name"
7896 There are several types of pattern that require Exim to know the name of the
7897 remote host. These are either wildcard patterns or lookups by name. (If a
7898 complete hostname is given without any wildcarding, it is used to find an IP
7899 address to match against, as described in the section &<<SECThoslispatip>>&
7900 above.)
7901
7902 If the remote host name is not already known when Exim encounters one of these
7903 patterns, it has to be found from the IP address.
7904 Although many sites on the Internet are conscientious about maintaining reverse
7905 DNS data for their hosts, there are also many that do not do this.
7906 Consequently, a name cannot always be found, and this may lead to unwanted
7907 effects. Take care when configuring host lists with wildcarded name patterns.
7908 Consider what will happen if a name cannot be found.
7909
7910 Because of the problems of determining host names from IP addresses, matching
7911 against host names is not as common as matching against IP addresses.
7912
7913 By default, in order to find a host name, Exim first does a reverse DNS lookup;
7914 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
7915 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
7916 are done can be changed by setting the &%host_lookup_order%& option. For
7917 security, once Exim has found one or more names, it looks up the IP addresses
7918 for these names and compares them with the IP address that it started with.
7919 Only those names whose IP addresses match are accepted. Any other names are
7920 discarded. If no names are left, Exim behaves as if the host name cannot be
7921 found. In the most common case there is only one name and one IP address.
7922
7923 There are some options that control what happens if a host name cannot be
7924 found. These are described in section &<<SECTbehipnot>>& below.
7925
7926 .cindex "host" "alias for"
7927 .cindex "alias for host"
7928 As a result of aliasing, hosts may have more than one name. When processing any
7929 of the following types of pattern, all the host's names are checked:
7930
7931 .ilist
7932 .cindex "asterisk" "in host list"
7933 If a pattern starts with &"*"& the remainder of the item must match the end of
7934 the host name. For example, &`*.b.c`& matches all hosts whose names end in
7935 &'.b.c'&. This special simple form is provided because this is a very common
7936 requirement. Other kinds of wildcarding require the use of a regular
7937 expression.
7938 .next
7939 .cindex "regular expressions" "in host list"
7940 .cindex "host list" "regular expression in"
7941 If the item starts with &"^"& it is taken to be a regular expression which is
7942 matched against the host name. Host names are case-independent, so this regular
7943 expression match is by default case-independent, but you can make it
7944 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
7945 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
7946 example,
7947 .code
7948 ^(a|b)\.c\.d$
7949 .endd
7950 is a regular expression that matches either of the two hosts &'a.c.d'& or
7951 &'b.c.d'&. When a regular expression is used in a host list, you must take care
7952 that backslash and dollar characters are not misinterpreted as part of the
7953 string expansion. The simplest way to do this is to use &`\N`& to mark that
7954 part of the string as non-expandable. For example:
7955 .code
7956 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
7957 .endd
7958 &*Warning*&: If you want to match a complete host name, you must include the
7959 &`$`& terminating metacharacter in the regular expression, as in the above
7960 example. Without it, a match at the start of the host name is all that is
7961 required.
7962 .endlist
7963
7964
7965
7966
7967 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
7968 .cindex "host" "lookup failures, permanent"
7969 While processing a host list, Exim may need to look up an IP address from a
7970 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
7971 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
7972 behaviour when it fails to find the information it is seeking is the same.
7973
7974 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
7975 apply to temporary DNS errors, whose handling is described in the next section.
7976
7977 .cindex "&`+include_unknown`&"
7978 .cindex "&`+ignore_unknown`&"
7979 By default, Exim behaves as if the host does not match the list. This may not
7980 always be what you want to happen. To change Exim's behaviour, the special
7981 items &`+include_unknown`& or &`+ignore_unknown`& may appear in the list (at
7982 top level &-- they are not recognized in an indirected file).
7983
7984 .ilist
7985 If any item that follows &`+include_unknown`& requires information that
7986 cannot found, Exim behaves as if the host does match the list. For example,
7987 .code
7988 host_reject_connection = +include_unknown:*.enemy.ex
7989 .endd
7990 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
7991 any hosts whose name it cannot find.
7992
7993 .next
7994 If any item that follows &`+ignore_unknown`& requires information that cannot
7995 be found, Exim ignores that item and proceeds to the rest of the list. For
7996 example:
7997 .code
7998 accept hosts = +ignore_unknown : friend.example : \
7999 192.168.4.5
8000 .endd
8001 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
8002 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
8003 name can be found for 192.168.4.5, it is rejected.
8004 .endlist
8005
8006 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
8007 list. The effect of each one lasts until the next, or until the end of the
8008 list.
8009
8010
8011 .section "Temporary DNS errors when looking up host information" &&&
8012 "SECTtemdnserr"
8013 .cindex "host" "lookup failures, temporary"
8014 .cindex "&`+include_defer`&"
8015 .cindex "&`+ignore_defer`&"
8016 A temporary DNS lookup failure normally causes a defer action (except when
8017 &%dns_again_means_nonexist%& converts it into a permanent error). However,
8018 host lists can include &`+ignore_defer`& and &`+include_defer`&, analagous to
8019 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
8020 section. These options should be used with care, probably only in non-critical
8021 host lists such as whitelists.
8022
8023
8024
8025 .section "Host list patterns for single-key lookups by host name" &&&
8026 "SECThoslispatnamsk"
8027 .cindex "unknown host name"
8028 .cindex "host list" "matching host name"
8029 If a pattern is of the form
8030 .display
8031 <&'single-key-search-type'&>;<&'search-data'&>
8032 .endd
8033 for example
8034 .code
8035 dbm;/host/accept/list
8036 .endd
8037 a single-key lookup is performed, using the host name as its key. If the
8038 lookup succeeds, the host matches the item. The actual data that is looked up
8039 is not used.
8040
8041 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
8042 keys in the file, not IP addresses. If you want to do lookups based on IP
8043 addresses, you must precede the search type with &"net-"& (see section
8044 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
8045 two items in the same list, one doing an address lookup and one doing a name
8046 lookup, both using the same file.
8047
8048
8049
8050 .section "Host list patterns for query-style lookups" "SECID81"
8051 If a pattern is of the form
8052 .display
8053 <&'query-style-search-type'&>;<&'query'&>
8054 .endd
8055 the query is obeyed, and if it succeeds, the host matches the item. The actual
8056 data that is looked up is not used. The variables &$sender_host_address$& and
8057 &$sender_host_name$& can be used in the query. For example:
8058 .code
8059 hosts_lookup = pgsql;\
8060 select ip from hostlist where ip='$sender_host_address'
8061 .endd
8062 The value of &$sender_host_address$& for an IPv6 address contains colons. You
8063 can use the &%sg%& expansion item to change this if you need to. If you want to
8064 use masked IP addresses in database queries, you can use the &%mask%& expansion
8065 operator.
8066
8067 If the query contains a reference to &$sender_host_name$&, Exim automatically
8068 looks up the host name if has not already done so. (See section
8069 &<<SECThoslispatnam>>& for comments on finding host names.)
8070
8071 Historical note: prior to release 4.30, Exim would always attempt to find a
8072 host name before running the query, unless the search type was preceded by
8073 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
8074 still recognized for query-style lookups, but its presence or absence has no
8075 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
8076 See section &<<SECThoslispatsikey>>&.)
8077
8078
8079
8080 .section "Mixing wildcarded host names and addresses in host lists" &&&
8081 "SECTmixwilhos"
8082 .cindex "host list" "mixing names and addresses in"
8083 If you have name lookups or wildcarded host names and IP addresses in the same
8084 host list, you should normally put the IP addresses first. For example, in an
8085 ACL you could have:
8086 .code
8087 accept hosts = 10.9.8.7 : *.friend.example
8088 .endd
8089 The reason for this lies in the left-to-right way that Exim processes lists.
8090 It can test IP addresses without doing any DNS lookups, but when it reaches an
8091 item that requires a host name, it fails if it cannot find a host name to
8092 compare with the pattern. If the above list is given in the opposite order, the
8093 &%accept%& statement fails for a host whose name cannot be found, even if its
8094 IP address is 10.9.8.7.
8095
8096 If you really do want to do the name check first, and still recognize the IP
8097 address, you can rewrite the ACL like this:
8098 .code
8099 accept hosts = *.friend.example
8100 accept hosts = 10.9.8.7
8101 .endd
8102 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
8103 &<<CHAPACL>>& for details of ACLs.
8104
8105
8106
8107
8108
8109 .section "Address lists" "SECTaddresslist"
8110 .cindex "list" "address list"
8111 .cindex "address list" "empty item"
8112 .cindex "address list" "patterns"
8113 Address lists contain patterns that are matched against mail addresses. There
8114 is one special case to be considered: the sender address of a bounce message is
8115 always empty. You can test for this by providing an empty item in an address
8116 list. For example, you can set up a router to process bounce messages by
8117 using this option setting:
8118 .code
8119 senders = :
8120 .endd
8121 The presence of the colon creates an empty item. If you do not provide any
8122 data, the list is empty and matches nothing. The empty sender can also be
8123 detected by a regular expression that matches an empty string,
8124 and by a query-style lookup that succeeds when &$sender_address$& is empty.
8125
8126 Non-empty items in an address list can be straightforward email addresses. For
8127 example:
8128 .code
8129 senders = jbc@askone.example : hs@anacreon.example
8130 .endd
8131 A certain amount of wildcarding is permitted. If a pattern contains an @
8132 character, but is not a regular expression and does not begin with a
8133 semicolon-terminated lookup type (described below), the local part of the
8134 subject address is compared with the local part of the pattern, which may start
8135 with an asterisk. If the local parts match, the domain is checked in exactly
8136 the same way as for a pattern in a domain list. For example, the domain can be
8137 wildcarded, refer to a named list, or be a lookup:
8138 .code
8139 deny senders = *@*.spamming.site:\
8140 *@+hostile_domains:\
8141 bozo@partial-lsearch;/list/of/dodgy/sites:\
8142 *@dbm;/bad/domains.db
8143 .endd
8144 .cindex "local part" "starting with !"
8145 .cindex "address list" "local part starting with !"
8146 If a local part that begins with an exclamation mark is required, it has to be
8147 specified using a regular expression, because otherwise the exclamation mark is
8148 treated as a sign of negation, as is standard in lists.
8149
8150 If a non-empty pattern that is not a regular expression or a lookup does not
8151 contain an @ character, it is matched against the domain part of the subject
8152 address. The only two formats that are recognized this way are a literal
8153 domain, or a domain pattern that starts with *. In both these cases, the effect
8154 is the same as if &`*@`& preceded the pattern. For example:
8155 .code
8156 deny senders = enemy.domain : *.enemy.domain
8157 .endd
8158
8159 The following kinds of more complicated address list pattern can match any
8160 address, including the empty address that is characteristic of bounce message
8161 senders:
8162
8163 .ilist
8164 .cindex "regular expressions" "in address list"
8165 .cindex "address list" "regular expression in"
8166 If (after expansion) a pattern starts with &"^"&, a regular expression match is
8167 done against the complete address, with the pattern as the regular expression.
8168 You must take care that backslash and dollar characters are not misinterpreted
8169 as part of the string expansion. The simplest way to do this is to use &`\N`&
8170 to mark that part of the string as non-expandable. For example:
8171 .code
8172 deny senders = \N^.*this.*@example\.com$\N : \
8173 \N^\d{8}.+@spamhaus.example$\N : ...
8174 .endd
8175 The &`\N`& sequences are removed by the expansion, so these items do indeed
8176 start with &"^"& by the time they are being interpreted as address patterns.
8177
8178 .next
8179 .cindex "address list" "lookup for complete address"
8180 Complete addresses can be looked up by using a pattern that starts with a
8181 lookup type terminated by a semicolon, followed by the data for the lookup. For
8182 example:
8183 .code
8184 deny senders = cdb;/etc/blocked.senders : \
8185 mysql;select address from blocked where \
8186 address='${quote_mysql:$sender_address}'
8187 .endd
8188 Both query-style and single-key lookup types can be used. For a single-key
8189 lookup type, Exim uses the complete address as the key. However, empty keys are
8190 not supported for single-key lookups, so a match against the empty address
8191 always fails. This restriction does not apply to query-style lookups.
8192
8193 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
8194 cannot be used, and is ignored if specified, with an entry being written to the
8195 panic log.
8196 .cindex "*@ with single-key lookup"
8197 However, you can configure lookup defaults, as described in section
8198 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
8199 default. For example, with this lookup:
8200 .code
8201 accept senders = lsearch*@;/some/file
8202 .endd
8203 the file could contains lines like this:
8204 .code
8205 user1@domain1.example
8206 *@domain2.example
8207 .endd
8208 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
8209 that are tried is:
8210 .code
8211 nimrod@jaeger.example
8212 *@jaeger.example
8213 *
8214 .endd
8215 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
8216 would mean that every address matches, thus rendering the test useless.
8217
8218 &*Warning 2*&: Do not confuse these two kinds of item:
8219 .code
8220 deny recipients = dbm*@;/some/file
8221 deny recipients = *@dbm;/some/file
8222 .endd
8223 The first does a whole address lookup, with defaulting, as just described,
8224 because it starts with a lookup type. The second matches the local part and
8225 domain independently, as described in a bullet point below.
8226 .endlist
8227
8228
8229 The following kinds of address list pattern can match only non-empty addresses.
8230 If the subject address is empty, a match against any of these pattern types
8231 always fails.
8232
8233
8234 .ilist
8235 .cindex "@@ with single-key lookup"
8236 .cindex "address list" "@@ lookup type"
8237 .cindex "address list" "split local part and domain"
8238 If a pattern starts with &"@@"& followed by a single-key lookup item
8239 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
8240 split into a local part and a domain. The domain is looked up in the file. If
8241 it is not found, there is no match. If it is found, the data that is looked up
8242 from the file is treated as a colon-separated list of local part patterns, each
8243 of which is matched against the subject local part in turn.
8244
8245 .cindex "asterisk" "in address list"
8246 The lookup may be a partial one, and/or one involving a search for a default
8247 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
8248 patterns that are looked up can be regular expressions or begin with &"*"&, or
8249 even be further lookups. They may also be independently negated. For example,
8250 with
8251 .code
8252 deny senders = @@dbm;/etc/reject-by-domain
8253 .endd
8254 the data from which the DBM file is built could contain lines like
8255 .code
8256 baddomain.com: !postmaster : *
8257 .endd
8258 to reject all senders except &%postmaster%& from that domain.
8259
8260 .cindex "local part" "starting with !"
8261 If a local part that actually begins with an exclamation mark is required, it
8262 has to be specified using a regular expression. In &(lsearch)& files, an entry
8263 may be split over several lines by indenting the second and subsequent lines,
8264 but the separating colon must still be included at line breaks. White space
8265 surrounding the colons is ignored. For example:
8266 .code
8267 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
8268 spammer3 : spammer4
8269 .endd
8270 As in all colon-separated lists in Exim, a colon can be included in an item by
8271 doubling.
8272
8273 If the last item in the list starts with a right angle-bracket, the remainder
8274 of the item is taken as a new key to look up in order to obtain a continuation
8275 list of local parts. The new key can be any sequence of characters. Thus one
8276 might have entries like
8277 .code
8278 aol.com: spammer1 : spammer 2 : >*
8279 xyz.com: spammer3 : >*
8280 *: ^\d{8}$
8281 .endd
8282 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
8283 local parts for all domains, in addition to the specific local parts listed for
8284 each domain. Of course, using this feature costs another lookup each time a
8285 chain is followed, but the effort needed to maintain the data is reduced.
8286
8287 .cindex "loop" "in lookups"
8288 It is possible to construct loops using this facility, and in order to catch
8289 them, the chains may be no more than fifty items long.
8290
8291 .next
8292 The @@<&'lookup'&> style of item can also be used with a query-style
8293 lookup, but in this case, the chaining facility is not available. The lookup
8294 can only return a single list of local parts.
8295 .endlist
8296
8297 &*Warning*&: There is an important difference between the address list items
8298 in these two examples:
8299 .code
8300 senders = +my_list
8301 senders = *@+my_list
8302 .endd
8303 In the first one, &`my_list`& is a named address list, whereas in the second
8304 example it is a named domain list.
8305
8306
8307
8308
8309 .section "Case of letters in address lists" "SECTcasletadd"
8310 .cindex "case of local parts"
8311 .cindex "address list" "case forcing"
8312 .cindex "case forcing in address lists"
8313 Domains in email addresses are always handled caselessly, but for local parts
8314 case may be significant on some systems (see &%caseful_local_part%& for how
8315 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
8316 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
8317 blocking lists should be done in a case-independent manner. Since most address
8318 lists in Exim are used for this kind of control, Exim attempts to do this by
8319 default.
8320
8321 The domain portion of an address is always lowercased before matching it to an
8322 address list. The local part is lowercased by default, and any string
8323 comparisons that take place are done caselessly. This means that the data in
8324 the address list itself, in files included as plain file names, and in any file
8325 that is looked up using the &"@@"& mechanism, can be in any case. However, the
8326 keys in files that are looked up by a search type other than &(lsearch)& (which
8327 works caselessly) must be in lower case, because these lookups are not
8328 case-independent.
8329
8330 .cindex "&`+caseful`&"
8331 To allow for the possibility of caseful address list matching, if an item in
8332 an address list is the string &"+caseful"&, the original case of the local
8333 part is restored for any comparisons that follow, and string comparisons are no
8334 longer case-independent. This does not affect the domain, which remains in
8335 lower case. However, although independent matches on the domain alone are still
8336 performed caselessly, regular expressions that match against an entire address
8337 become case-sensitive after &"+caseful"& has been seen.
8338
8339
8340
8341 .section "Local part lists" "SECTlocparlis"
8342 .cindex "list" "local part list"
8343 .cindex "local part" "list"
8344 Case-sensitivity in local part lists is handled in the same way as for address
8345 lists, as just described. The &"+caseful"& item can be used if required. In a
8346 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
8347 set false, the subject is lowercased and the matching is initially
8348 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
8349 matching in the local part list, but not elsewhere in the router. If
8350 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
8351 option is case-sensitive from the start.
8352
8353 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
8354 comments are handled in the same way as address lists &-- they are recognized
8355 only if the # is preceded by white space or the start of the line.
8356 Otherwise, local part lists are matched in the same way as domain lists, except
8357 that the special items that refer to the local host (&`@`&, &`@[]`&,
8358 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
8359 Refer to section &<<SECTdomainlist>>& for details of the other available item
8360 types.
8361 .ecindex IIDdohoadli
8362
8363
8364
8365
8366 . ////////////////////////////////////////////////////////////////////////////
8367 . ////////////////////////////////////////////////////////////////////////////
8368
8369 .chapter "String expansions" "CHAPexpand"
8370 .scindex IIDstrexp "expansion" "of strings"
8371 Many strings in Exim's run time configuration are expanded before use. Some of
8372 them are expanded every time they are used; others are expanded only once.
8373
8374 When a string is being expanded it is copied verbatim from left to right except
8375 when a dollar or backslash character is encountered. A dollar specifies the
8376 start of a portion of the string that is interpreted and replaced as described
8377 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
8378 escape character, as described in the following section.
8379
8380
8381
8382 .section "Literal text in expanded strings" "SECTlittext"
8383 .cindex "expansion" "including literal text"
8384 An uninterpreted dollar can be included in an expanded string by putting a
8385 backslash in front of it. A backslash can be used to prevent any special
8386 character being treated specially in an expansion, including backslash itself.
8387 If the string appears in quotes in the configuration file, two backslashes are
8388 required because the quotes themselves cause interpretation of backslashes when
8389 the string is read in (see section &<<SECTstrings>>&).
8390
8391 .cindex "expansion" "non-expandable substrings"
8392 A portion of the string can specified as non-expandable by placing it between
8393 two occurrences of &`\N`&. This is particularly useful for protecting regular
8394 expressions, which often contain backslashes and dollar signs. For example:
8395 .code
8396 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
8397 .endd
8398 On encountering the first &`\N`&, the expander copies subsequent characters
8399 without interpretation until it reaches the next &`\N`& or the end of the
8400 string.
8401
8402
8403
8404 .section "Character escape sequences in expanded strings" "SECID82"
8405 .cindex "expansion" "escape sequences"
8406 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
8407 expanded string is recognized as an escape sequence for the character newline,
8408 carriage return, or tab, respectively. A backslash followed by up to three
8409 octal digits is recognized as an octal encoding for a single character, and a
8410 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
8411 encoding.
8412
8413 These escape sequences are also recognized in quoted strings when they are read
8414 in. Their interpretation in expansions as well is useful for unquoted strings,
8415 and for other cases such as looked-up strings that are then expanded.
8416
8417
8418 .section "Testing string expansions" "SECID83"
8419 .cindex "expansion" "testing"
8420 .cindex "testing" "string expansion"
8421 .oindex "&%-be%&"
8422 Many expansions can be tested by calling Exim with the &%-be%& option. This
8423 takes the command arguments, or lines from the standard input if there are no
8424 arguments, runs them through the string expansion code, and writes the results
8425 to the standard output. Variables based on configuration values are set up, but
8426 since no message is being processed, variables such as &$local_part$& have no
8427 value. Nevertheless the &%-be%& option can be useful for checking out file and
8428 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
8429 and &%nhash%&.
8430
8431 Exim gives up its root privilege when it is called with the &%-be%& option, and
8432 instead runs under the uid and gid it was called with, to prevent users from
8433 using &%-be%& for reading files to which they do not have access.
8434
8435 .oindex "&%-bem%&"
8436 If you want to test expansions that include variables whose values are taken
8437 from a message, there are two other options that can be used. The &%-bem%&
8438 option is like &%-be%& except that it is followed by a file name. The file is
8439 read as a message before doing the test expansions. For example:
8440 .code
8441 exim -bem /tmp/test.message '$h_subject:'
8442 .endd
8443 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
8444 Exim message identifier. For example:
8445 .code
8446 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
8447 .endd
8448 This loads the message from Exim's spool before doing the test expansions, and
8449 is therefore restricted to admin users.
8450
8451
8452 .section "Forced expansion failure" "SECTforexpfai"
8453 .cindex "expansion" "forced failure"
8454 A number of expansions that are described in the following section have
8455 alternative &"true"& and &"false"& substrings, enclosed in brace characters
8456 (which are sometimes called &"curly brackets"&). Which of the two strings is
8457 used depends on some condition that is evaluated as part of the expansion. If,
8458 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
8459 the entire string expansion fails in a way that can be detected by the code
8460 that requested the expansion. This is called &"forced expansion failure"&, and
8461 its consequences depend on the circumstances. In some cases it is no different
8462 from any other expansion failure, but in others a different action may be
8463 taken. Such variations are mentioned in the documentation of the option that is
8464 being expanded.
8465
8466
8467
8468
8469 .section "Expansion items" "SECTexpansionitems"
8470 The following items are recognized in expanded strings. White space may be used
8471 between sub-items that are keywords or substrings enclosed in braces inside an
8472 outer set of braces, to improve readability. &*Warning*&: Within braces,
8473 white space is significant.
8474
8475 .vlist
8476 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
8477 .cindex "expansion" "variables"
8478 Substitute the contents of the named variable, for example:
8479 .code
8480 $local_part
8481 ${domain}
8482 .endd
8483 The second form can be used to separate the name from subsequent alphanumeric
8484 characters. This form (using braces) is available only for variables; it does
8485 &'not'& apply to message headers. The names of the variables are given in
8486 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
8487 given, the expansion fails.
8488
8489 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
8490 .cindex "expansion" "operators"
8491 The string is first itself expanded, and then the operation specified by
8492 <&'op'&> is applied to it. For example:
8493 .code
8494 ${lc:$local_part}
8495 .endd
8496 The string starts with the first character after the colon, which may be
8497 leading white space. A list of operators is given in section &<<SECTexpop>>&
8498 below. The operator notation is used for simple expansion items that have just
8499 one argument, because it reduces the number of braces and therefore makes the
8500 string easier to understand.
8501
8502 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
8503 This item inserts &"basic"& header lines. It is described with the &%header%&
8504 expansion item below.
8505
8506 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
8507 {*&<&'arg'&>&*}...}*&"
8508 .cindex &%dlfunc%&
8509 This expansion dynamically loads and then calls a locally-written C function.
8510 This functionality is available only if Exim is compiled with
8511 .code
8512 EXPAND_DLFUNC=yes
8513 .endd
8514 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
8515 object so that it doesn't reload the same object file in the same Exim process
8516 (but of course Exim does start new processes frequently).
8517
8518 There may be from zero to eight arguments to the function. When compiling
8519 a local function that is to be called in this way, &_local_scan.h_& should be
8520 included. The Exim variables and functions that are defined by that API
8521 are also available for dynamically loaded functions. The function itself
8522 must have the following type:
8523 .code
8524 int dlfunction(uschar **yield, int argc, uschar *argv[])
8525 .endd
8526 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
8527 function should return one of the following values:
8528
8529 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
8530 into the expanded string that is being built.
8531
8532 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
8533 from &'yield'&, if it is set.
8534
8535 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
8536 taken from &'yield'& if it is set.
8537
8538 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
8539
8540 When compiling a function that is to be used in this way with gcc,
8541 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
8542 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
8543
8544 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
8545 {*&<&'string3'&>&*}}*&"
8546 .cindex "expansion" "extracting substrings by key"
8547 .cindex "&%extract%&" "substrings by key"
8548 The key and <&'string1'&> are first expanded separately. Leading and trailing
8549 white space is removed from the key (but not from any of the strings). The key
8550 must not consist entirely of digits. The expanded <&'string1'&> must be of the
8551 form:
8552 .display
8553 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
8554 .endd
8555 .vindex "&$value$&"
8556 where the equals signs and spaces (but not both) are optional. If any of the
8557 values contain white space, they must be enclosed in double quotes, and any
8558 values that are enclosed in double quotes are subject to escape processing as
8559 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
8560 for the value that corresponds to the key. The search is case-insensitive. If
8561 the key is found, <&'string2'&> is expanded, and replaces the whole item;
8562 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
8563 variable &$value$& contains the value that has been extracted. Afterwards, it
8564 is restored to any previous value it might have had.
8565
8566 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
8567 key is not found. If {<&'string2'&>} is also omitted, the value that was
8568 extracted is used. Thus, for example, these two expansions are identical, and
8569 yield &"2001"&:
8570 .code
8571 ${extract{gid}{uid=1984 gid=2001}}
8572 ${extract{gid}{uid=1984 gid=2001}{$value}}
8573 .endd
8574 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
8575 appear, for example:
8576 .code
8577 ${extract{Z}{A=... B=...}{$value} fail }
8578 .endd
8579 This forces an expansion failure (see section &<<SECTforexpfai>>&);
8580 {<&'string2'&>} must be present for &"fail"& to be recognized.
8581
8582
8583 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
8584 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
8585 .cindex "expansion" "extracting substrings by number"
8586 .cindex "&%extract%&" "substrings by number"
8587 The <&'number'&> argument must consist entirely of decimal digits,
8588 apart from leading and trailing white space, which is ignored.
8589 This is what distinguishes this form of &%extract%& from the previous kind. It
8590 behaves in the same way, except that, instead of extracting a named field, it
8591 extracts from <&'string1'&> the field whose number is given as the first
8592 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
8593 <&'string3'&> as before.
8594
8595 The fields in the string are separated by any one of the characters in the
8596 separator string. These may include space or tab characters.
8597 The first field is numbered one. If the number is negative, the fields are
8598 counted from the end of the string, with the rightmost one numbered -1. If the
8599 number given is zero, the entire string is returned. If the modulus of the
8600 number is greater than the number of fields in the string, the result is the
8601 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
8602 provided. For example:
8603 .code
8604 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
8605 .endd
8606 yields &"42"&, and
8607 .code
8608 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
8609 .endd
8610 yields &"99"&. Two successive separators mean that the field between them is
8611 empty (for example, the fifth field above).
8612
8613
8614 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
8615 .cindex "list" "selecting by condition"
8616 .cindex "expansion" "selecting from list by condition"
8617 .vindex "&$item$&"
8618 After expansion, <&'string'&> is interpreted as a list, colon-separated by
8619 default, but the separator can be changed in the usual way. For each item
8620 in this list, its value is place in &$item$&, and then the condition is
8621 evaluated. If the condition is true, &$item$& is added to the output as an
8622 item in a new list; if the condition is false, the item is discarded. The
8623 separator used for the output list is the same as the one used for the
8624 input, but a separator setting is not included in the output. For example:
8625 .code
8626 ${filter{a:b:c}{!eq{$item}{b}}
8627 .endd
8628 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
8629 to what it was before. See also the &*map*& and &*reduce*& expansion items.
8630
8631
8632 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
8633 .cindex "hash function" "textual"
8634 .cindex "expansion" "textual hash"
8635 This is a textual hashing function, and was the first to be implemented in
8636 early versions of Exim. In current releases, there are other hashing functions
8637 (numeric, MD5, and SHA-1), which are described below.
8638
8639 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
8640 <&'n'&>. If you are using fixed values for these numbers, that is, if
8641 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
8642 use the simpler operator notation that avoids some of the braces:
8643 .code
8644 ${hash_<n>_<m>:<string>}
8645 .endd
8646 The second number is optional (in both notations). If <&'n'&> is greater than
8647 or equal to the length of the string, the expansion item returns the string.
8648 Otherwise it computes a new string of length <&'n'&> by applying a hashing
8649 function to the string. The new string consists of characters taken from the
8650 first <&'m'&> characters of the string
8651 .code
8652 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
8653 .endd
8654 If <&'m'&> is not present the value 26 is used, so that only lower case
8655 letters appear. For example:
8656 .display
8657 &`$hash{3}{monty}} `& yields &`jmg`&
8658 &`$hash{5}{monty}} `& yields &`monty`&
8659 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
8660 .endd
8661
8662 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
8663 &*$h_*&<&'header&~name'&>&*:*&" &&&
8664 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
8665 &*$bh_*&<&'header&~name'&>&*:*&" &&&
8666 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
8667 &*$rh_*&<&'header&~name'&>&*:*&"
8668 .cindex "expansion" "header insertion"
8669 .vindex "&$header_$&"
8670 .vindex "&$bheader_$&"
8671 .vindex "&$rheader_$&"
8672 .cindex "header lines" "in expansion strings"
8673 .cindex "header lines" "character sets"
8674 .cindex "header lines" "decoding"
8675 Substitute the contents of the named message header line, for example
8676 .code
8677 $header_reply-to:
8678 .endd
8679 The newline that terminates a header line is not included in the expansion, but
8680 internal newlines (caused by splitting the header line over several physical
8681 lines) may be present.
8682
8683 The difference between &%rheader%&, &%bheader%&, and &%header%& is in the way
8684 the data in the header line is interpreted.
8685
8686 .ilist
8687 .cindex "white space" "in header lines"
8688 &%rheader%& gives the original &"raw"& content of the header line, with no
8689 processing at all, and without the removal of leading and trailing white space.
8690
8691 .next
8692 .cindex "base64 encoding" "in header lines"
8693 &%bheader%& removes leading and trailing white space, and then decodes base64
8694 or quoted-printable MIME &"words"& within the header text, but does no
8695 character set translation. If decoding of what looks superficially like a MIME
8696 &"word"& fails, the raw string is returned. If decoding
8697 .cindex "binary zero" "in header line"
8698 produces a binary zero character, it is replaced by a question mark &-- this is
8699 what Exim does for binary zeros that are actually received in header lines.
8700
8701 .next
8702 &%header%& tries to translate the string as decoded by &%bheader%& to a
8703 standard character set. This is an attempt to produce the same string as would
8704 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
8705 returned. Translation is attempted only on operating systems that support the
8706 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
8707 a system Makefile or in &_Local/Makefile_&.
8708 .endlist ilist
8709
8710 In a filter file, the target character set for &%header%& can be specified by a
8711 command of the following form:
8712 .code
8713 headers charset "UTF-8"
8714 .endd
8715 This command affects all references to &$h_$& (or &$header_$&) expansions in
8716 subsequently obeyed filter commands. In the absence of this command, the target
8717 character set in a filter is taken from the setting of the &%headers_charset%&
8718 option in the runtime configuration. The value of this option defaults to the
8719 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
8720 ISO-8859-1.
8721
8722 Header names follow the syntax of RFC 2822, which states that they may contain
8723 any printing characters except space and colon. Consequently, curly brackets
8724 &'do not'& terminate header names, and should not be used to enclose them as
8725 if they were variables. Attempting to do so causes a syntax error.
8726
8727 Only header lines that are common to all copies of a message are visible to
8728 this mechanism. These are the original header lines that are received with the
8729 message, and any that are added by an ACL statement or by a system
8730 filter. Header lines that are added to a particular copy of a message by a
8731 router or transport are not accessible.
8732
8733 For incoming SMTP messages, no header lines are visible in ACLs that are obeyed
8734 before the DATA ACL, because the header structure is not set up until the
8735 message is received. Header lines that are added in a RCPT ACL (for example)
8736 are saved until the message's incoming header lines are available, at which
8737 point they are added. When a DATA ACL is running, however, header lines added
8738 by earlier ACLs are visible.
8739
8740 Upper case and lower case letters are synonymous in header names. If the
8741 following character is white space, the terminating colon may be omitted, but
8742 this is not recommended, because you may then forget it when it is needed. When
8743 white space terminates the header name, it is included in the expanded string.
8744 If the message does not contain the given header, the expansion item is
8745 replaced by an empty string. (See the &%def%& condition in section
8746 &<<SECTexpcond>>& for a means of testing for the existence of a header.)
8747
8748 If there is more than one header with the same name, they are all concatenated
8749 to form the substitution string, up to a maximum length of 64K. Unless
8750 &%rheader%& is being used, leading and trailing white space is removed from
8751 each header before concatenation, and a completely empty header is ignored. A
8752 newline character is then inserted between non-empty headers, but there is no
8753 newline at the very end. For the &%header%& and &%bheader%& expansion, for
8754 those headers that contain lists of addresses, a comma is also inserted at the
8755 junctions between headers. This does not happen for the &%rheader%& expansion.
8756
8757
8758 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
8759 .cindex "expansion" "hmac hashing"
8760 .cindex &%hmac%&
8761 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
8762 shared secret and some text into a message authentication code, as specified in
8763 RFC 2104. This differs from &`${md5:secret_text...}`& or
8764 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
8765 cryptographic hash, allowing for authentication that is not possible with MD5
8766 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
8767 present. For example:
8768 .code
8769 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
8770 .endd
8771 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
8772 produces:
8773 .code
8774 dd97e3ba5d1a61b5006108f8c8252953
8775 .endd
8776 As an example of how this might be used, you might put in the main part of
8777 an Exim configuration:
8778 .code
8779 SPAMSCAN_SECRET=cohgheeLei2thahw
8780 .endd
8781 In a router or a transport you could then have:
8782 .code
8783 headers_add = \
8784 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
8785 ${hmac{md5}{SPAMSCAN_SECRET}\
8786 {${primary_hostname},${message_exim_id},$h_message-id:}}
8787 .endd
8788 Then given a message, you can check where it was scanned by looking at the
8789 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
8790 this header line is authentic by recomputing the authentication code from the
8791 host name, message ID and the &'Message-id:'& header line. This can be done
8792 using Exim's &%-be%& option, or by other means, for example by using the
8793 &'hmac_md5_hex()'& function in Perl.
8794
8795
8796 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
8797 .cindex "expansion" "conditional"
8798 .cindex "&%if%&, expansion item"
8799 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
8800 item; otherwise <&'string2'&> is used. The available conditions are described
8801 in section &<<SECTexpcond>>& below. For example:
8802 .code
8803 ${if eq {$local_part}{postmaster} {yes}{no} }
8804 .endd
8805 The second string need not be present; if it is not and the condition is not
8806 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
8807 be present instead of the second string (without any curly brackets). In this
8808 case, the expansion is forced to fail if the condition is not true (see section
8809 &<<SECTforexpfai>>&).
8810
8811 If both strings are omitted, the result is the string &`true`& if the condition
8812 is true, and the empty string if the condition is false. This makes it less
8813 cumbersome to write custom ACL and router conditions. For example, instead of
8814 .code
8815 condition = ${if >{$acl_m4}{3}{true}{false}}
8816 .endd
8817 you can use
8818 .code
8819 condition = ${if >{$acl_m4}{3}}
8820 .endd
8821
8822 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
8823 .cindex "expansion" "string truncation"
8824 .cindex "&%length%& expansion item"
8825 The &%length%& item is used to extract the initial portion of a string. Both
8826 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
8827 you are using a fixed value for the number, that is, if <&'string1'&> does not
8828 change when expanded, you can use the simpler operator notation that avoids
8829 some of the braces:
8830 .code
8831 ${length_<n>:<string>}
8832 .endd
8833 The result of this item is either the first <&'n'&> characters or the whole
8834 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
8835 &%strlen%&, which gives the length of a string.
8836
8837
8838 .vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
8839 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
8840 This is the first of one of two different types of lookup item, which are both
8841 described in the next item.
8842
8843 .vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
8844 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
8845 .cindex "expansion" "lookup in"
8846 .cindex "file" "lookups"
8847 .cindex "lookup" "in expanded string"
8848 The two forms of lookup item specify data lookups in files and databases, as
8849 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
8850 lookups, and the second is used for query-style lookups. The <&'key'&>,
8851 <&'file'&>, and <&'query'&> strings are expanded before use.
8852
8853 If there is any white space in a lookup item which is part of a filter command,
8854 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
8855 other place where white space is significant, the lookup item must be enclosed
8856 in double quotes. The use of data lookups in users' filter files may be locked
8857 out by the system administrator.
8858
8859 .vindex "&$value$&"
8860 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
8861 During its expansion, the variable &$value$& contains the data returned by the
8862 lookup. Afterwards it reverts to the value it had previously (at the outer
8863 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
8864 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
8865 string on failure. If <&'string2'&> is provided, it can itself be a nested
8866 lookup, thus providing a mechanism for looking up a default value when the
8867 original lookup fails.
8868
8869 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
8870 data for the outer lookup while the parameters of the second lookup are
8871 expanded, and also while <&'string2'&> of the second lookup is expanded, should
8872 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
8873 appear, and in this case, if the lookup fails, the entire expansion is forced
8874 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
8875 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
8876 successful lookup, and nothing in the case of failure.
8877
8878 For single-key lookups, the string &"partial"& is permitted to precede the
8879 search type in order to do partial matching, and * or *@ may follow a search
8880 type to request default lookups if the key does not match (see sections
8881 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
8882
8883 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
8884 If a partial search is used, the variables &$1$& and &$2$& contain the wild
8885 and non-wild parts of the key during the expansion of the replacement text.
8886 They return to their previous values at the end of the lookup item.
8887
8888 This example looks up the postmaster alias in the conventional alias file:
8889 .code
8890 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
8891 .endd
8892 This example uses NIS+ to look up the full name of the user corresponding to
8893 the local part of an address, forcing the expansion to fail if it is not found:
8894 .code
8895 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
8896 {$value}fail}
8897 .endd
8898
8899
8900 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
8901 .cindex "expansion" "list creation"
8902 .vindex "&$item$&"
8903 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
8904 default, but the separator can be changed in the usual way. For each item
8905 in this list, its value is place in &$item$&, and then <&'string2'&> is
8906 expanded and added to the output as an item in a new list. The separator used
8907 for the output list is the same as the one used for the input, but a separator
8908 setting is not included in the output. For example:
8909 .code
8910 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
8911 .endd
8912 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
8913 value of &$item$& is restored to what it was before. See also the &*filter*&
8914 and &*reduce*& expansion items.
8915
8916 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
8917 .cindex "expansion" "numeric hash"
8918 .cindex "hash function" "numeric"
8919 The three strings are expanded; the first two must yield numbers. Call them
8920 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
8921 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
8922 can use the simpler operator notation that avoids some of the braces:
8923 .code
8924 ${nhash_<n>_<m>:<string>}
8925 .endd
8926 The second number is optional (in both notations). If there is only one number,
8927 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
8928 processed by a div/mod hash function that returns two numbers, separated by a
8929 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
8930 example,
8931 .code
8932 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
8933 .endd
8934 returns the string &"6/33"&.
8935
8936
8937
8938 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
8939 .cindex "Perl" "use in expanded string"
8940 .cindex "expansion" "calling Perl from"
8941 This item is available only if Exim has been built to include an embedded Perl
8942 interpreter. The subroutine name and the arguments are first separately
8943 expanded, and then the Perl subroutine is called with those arguments. No
8944 additional arguments need be given; the maximum number permitted, including the
8945 name of the subroutine, is nine.
8946
8947 The return value of the subroutine is inserted into the expanded string, unless
8948 the return value is &%undef%&. In that case, the expansion fails in the same
8949 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
8950 Whatever you return is evaluated in a scalar context. For example, if you
8951 return the name of a Perl vector, the return value is the size of the vector,
8952 not its contents.
8953
8954 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
8955 with the error message that was passed to &%die%&. More details of the embedded
8956 Perl facility are given in chapter &<<CHAPperl>>&.
8957
8958 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
8959 out the use of this expansion item in filter files.
8960
8961
8962 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
8963 .cindex "&%prvs%& expansion item"
8964 The first argument is a complete email address and the second is secret
8965 keystring. The third argument, specifying a key number, is optional. If absent,
8966 it defaults to 0. The result of the expansion is a prvs-signed email address,
8967 to be typically used with the &%return_path%& option on an &(smtp)& transport
8968 as part of a bounce address tag validation (BATV) scheme. For more discussion
8969 and an example, see section &<<SECTverifyPRVS>>&.
8970
8971 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
8972 {*&<&'string'&>&*}}*&"
8973 .cindex "&%prvscheck%& expansion item"
8974 This expansion item is the complement of the &%prvs%& item. It is used for
8975 checking prvs-signed addresses. If the expansion of the first argument does not
8976 yield a syntactically valid prvs-signed address, the whole item expands to the
8977 empty string. When the first argument does expand to a syntactically valid
8978 prvs-signed address, the second argument is expanded, with the prvs-decoded
8979 version of the address and the key number extracted from the address in the
8980 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
8981
8982 These two variables can be used in the expansion of the second argument to
8983 retrieve the secret. The validity of the prvs-signed address is then checked
8984 against the secret. The result is stored in the variable &$prvscheck_result$&,
8985 which is empty for failure or &"1"& for success.
8986
8987 The third argument is optional; if it is missing, it defaults to an empty
8988 string. This argument is now expanded. If the result is an empty string, the
8989 result of the expansion is the decoded version of the address. This is the case
8990 whether or not the signature was valid. Otherwise, the result of the expansion
8991 is the expansion of the third argument.
8992
8993 All three variables can be used in the expansion of the third argument.
8994 However, once the expansion is complete, only &$prvscheck_result$& remains set.
8995 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
8996
8997 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
8998 .cindex "expansion" "inserting an entire file"
8999 .cindex "file" "inserting into expansion"
9000 .cindex "&%readfile%& expansion item"
9001 The file name and end-of-line string are first expanded separately. The file is
9002 then read, and its contents replace the entire item. All newline characters in
9003 the file are replaced by the end-of-line string if it is present. Otherwise,
9004 newlines are left in the string.
9005 String expansion is not applied to the contents of the file. If you want this,
9006 you must wrap the item in an &%expand%& operator. If the file cannot be read,
9007 the string expansion fails.
9008
9009 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
9010 locks out the use of this expansion item in filter files.
9011
9012
9013
9014 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
9015 {*&<&'timeout'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
9016 .cindex "expansion" "inserting from a socket"
9017 .cindex "socket, use of in expansion"
9018 .cindex "&%readsocket%& expansion item"
9019 This item inserts data from a Unix domain or Internet socket into the expanded
9020 string. The minimal way of using it uses just two arguments, as in these
9021 examples:
9022 .code
9023 ${readsocket{/socket/name}{request string}}
9024 ${readsocket{inet:some.host:1234}{request string}}
9025 .endd
9026 For a Unix domain socket, the first substring must be the path to the socket.
9027 For an Internet socket, the first substring must contain &`inet:`& followed by
9028 a host name or IP address, followed by a colon and a port, which can be a
9029 number or the name of a TCP port in &_/etc/services_&. An IP address may
9030 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
9031 example:
9032 .code
9033 ${readsocket{inet:[::1]:1234}{request string}}
9034 .endd
9035 Only a single host name may be given, but if looking it up yields more than
9036 one IP address, they are each tried in turn until a connection is made. For
9037 both kinds of socket, Exim makes a connection, writes the request string
9038 (unless it is an empty string) and reads from the socket until an end-of-file
9039 is read. A timeout of 5 seconds is applied. Additional, optional arguments
9040 extend what can be done. Firstly, you can vary the timeout. For example:
9041 .code
9042 ${readsocket{/socket/name}{request string}{3s}}
9043 .endd
9044 A fourth argument allows you to change any newlines that are in the data
9045 that is read, in the same way as for &%readfile%& (see above). This example
9046 turns them into spaces:
9047 .code
9048 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
9049 .endd
9050 As with all expansions, the substrings are expanded before the processing
9051 happens. Errors in these sub-expansions cause the expansion to fail. In
9052 addition, the following errors can occur:
9053
9054 .ilist
9055 Failure to create a socket file descriptor;
9056 .next
9057 Failure to connect the socket;
9058 .next
9059 Failure to write the request string;
9060 .next
9061 Timeout on reading from the socket.
9062 .endlist
9063
9064 By default, any of these errors causes the expansion to fail. However, if
9065 you supply a fifth substring, it is expanded and used when any of the above
9066 errors occurs. For example:
9067 .code
9068 ${readsocket{/socket/name}{request string}{3s}{\n}\
9069 {socket failure}}
9070 .endd
9071 You can test for the existence of a Unix domain socket by wrapping this
9072 expansion in &`${if exists`&, but there is a race condition between that test
9073 and the actual opening of the socket, so it is safer to use the fifth argument
9074 if you want to be absolutely sure of avoiding an expansion error for a
9075 non-existent Unix domain socket, or a failure to connect to an Internet socket.
9076
9077 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
9078 locks out the use of this expansion item in filter files.
9079
9080
9081 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9082 .cindex "expansion" "reducing a list to a scalar"
9083 .cindex "list" "reducing to a scalar"
9084 .vindex "&$value$&"
9085 .vindex "&$item$&"
9086 This operation reduces a list to a single, scalar string. After expansion,
9087 <&'string1'&> is interpreted as a list, colon-separated by default, but the
9088 separator can be changed in the usual way. Then <&'string2'&> is expanded and
9089 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
9090 list is assigned to &$item$& in turn, and <&'string3'&> is expanded for each of
9091 them. The result of that expansion is assigned to &$value$& before the next
9092 iteration. When the end of the list is reached, the final value of &$value$& is
9093 added to the expansion output. The &*reduce*& expansion item can be used in a
9094 number of ways. For example, to add up a list of numbers:
9095 .code
9096 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
9097 .endd
9098 The result of that expansion would be &`6`&. The maximum of a list of numbers
9099 can be found:
9100 .code
9101 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
9102 .endd
9103 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
9104 restored to what they were before. See also the &*filter*& and &*map*&
9105 expansion items.
9106
9107 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
9108 This item inserts &"raw"& header lines. It is described with the &%header%&
9109 expansion item above.
9110
9111 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
9112 {*&<&'string2'&>&*}}*&"
9113 .cindex "expansion" "running a command"
9114 .cindex "&%run%& expansion item"
9115 The command and its arguments are first expanded separately, and then the
9116 command is run in a separate process, but under the same uid and gid. As in
9117 other command executions from Exim, a shell is not used by default. If you want
9118 a shell, you must explicitly code it.
9119
9120 The standard input for the command exists, but is empty. The standard output
9121 and standard error are set to the same file descriptor.
9122 .cindex "return code" "from &%run%& expansion"
9123 .vindex "&$value$&"
9124 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
9125 and replaces the entire item; during this expansion, the standard output/error
9126 from the command is in the variable &$value$&. If the command fails,
9127 <&'string2'&>, if present, is expanded and used. Once again, during the
9128 expansion, the standard output/error from the command is in the variable
9129 &$value$&.
9130
9131 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
9132 can be the word &"fail"& (not in braces) to force expansion failure if the
9133 command does not succeed. If both strings are omitted, the result is contents
9134 of the standard output/error on success, and nothing on failure.
9135
9136 .vindex "&$runrc$&"
9137 The return code from the command is put in the variable &$runrc$&, and this
9138 remains set afterwards, so in a filter file you can do things like this:
9139 .code
9140 if "${run{x y z}{}}$runrc" is 1 then ...
9141 elif $runrc is 2 then ...
9142 ...
9143 endif
9144 .endd
9145 If execution of the command fails (for example, the command does not exist),
9146 the return code is 127 &-- the same code that shells use for non-existent
9147 commands.
9148
9149 &*Warning*&: In a router or transport, you cannot assume the order in which
9150 option values are expanded, except for those preconditions whose order of
9151 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
9152 by the expansion of one option, and use it in another.
9153
9154 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
9155 out the use of this expansion item in filter files.
9156
9157
9158 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
9159 .cindex "expansion" "string substitution"
9160 .cindex "&%sg%& expansion item"
9161 This item works like Perl's substitution operator (s) with the global (/g)
9162 option; hence its name. However, unlike the Perl equivalent, Exim does not
9163 modify the subject string; instead it returns the modified string for insertion
9164 into the overall expansion. The item takes three arguments: the subject string,
9165 a regular expression, and a substitution string. For example:
9166 .code
9167 ${sg{abcdefabcdef}{abc}{xyz}}
9168 .endd
9169 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
9170 if any $ or \ characters are required in the regular expression or in the
9171 substitution string, they have to be escaped. For example:
9172 .code
9173 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
9174 .endd
9175 yields &"defabc"&, and
9176 .code
9177 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
9178 .endd
9179 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
9180 the regular expression from string expansion.
9181
9182
9183
9184 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9185 .cindex "&%substr%& expansion item"
9186 .cindex "substring extraction"
9187 .cindex "expansion" "substring extraction"
9188 The three strings are expanded; the first two must yield numbers. Call them
9189 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9190 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9191 can use the simpler operator notation that avoids some of the braces:
9192 .code
9193 ${substr_<n>_<m>:<string>}
9194 .endd
9195 The second number is optional (in both notations).
9196 If it is absent in the simpler format, the preceding underscore must also be
9197 omitted.
9198
9199 The &%substr%& item can be used to extract more general substrings than
9200 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
9201 length required. For example
9202 .code
9203 ${substr{3}{2}{$local_part}}
9204 .endd
9205 If the starting offset is greater than the string length the result is the
9206 null string; if the length plus starting offset is greater than the string
9207 length, the result is the right-hand part of the string, starting from the
9208 given offset. The first character in the string has offset zero.
9209
9210 The &%substr%& expansion item can take negative offset values to count
9211 from the right-hand end of its operand. The last character is offset -1, the
9212 second-last is offset -2, and so on. Thus, for example,
9213 .code
9214 ${substr{-5}{2}{1234567}}
9215 .endd
9216 yields &"34"&. If the absolute value of a negative offset is greater than the
9217 length of the string, the substring starts at the beginning of the string, and
9218 the length is reduced by the amount of overshoot. Thus, for example,
9219 .code
9220 ${substr{-5}{2}{12}}
9221 .endd
9222 yields an empty string, but
9223 .code
9224 ${substr{-3}{2}{12}}
9225 .endd
9226 yields &"1"&.
9227
9228 When the second number is omitted from &%substr%&, the remainder of the string
9229 is taken if the offset is positive. If it is negative, all characters in the
9230 string preceding the offset point are taken. For example, an offset of -1 and
9231 no length, as in these semantically identical examples:
9232 .code
9233 ${substr_-1:abcde}
9234 ${substr{-1}{abcde}}
9235 .endd
9236 yields all but the last character of the string, that is, &"abcd"&.
9237
9238
9239
9240 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
9241 {*&<&'replacements'&>&*}}*&"
9242 .cindex "expansion" "character translation"
9243 .cindex "&%tr%& expansion item"
9244 This item does single-character translation on its subject string. The second
9245 argument is a list of characters to be translated in the subject string. Each
9246 matching character is replaced by the corresponding character from the
9247 replacement list. For example
9248 .code
9249 ${tr{abcdea}{ac}{13}}
9250 .endd
9251 yields &`1b3de1`&. If there are duplicates in the second character string, the
9252 last occurrence is used. If the third string is shorter than the second, its
9253 last character is replicated. However, if it is empty, no translation takes
9254 place.
9255 .endlist
9256
9257
9258
9259 .section "Expansion operators" "SECTexpop"
9260 .cindex "expansion" "operators"
9261 For expansion items that perform transformations on a single argument string,
9262 the &"operator"& notation is used because it is simpler and uses fewer braces.
9263 The substring is first expanded before the operation is applied to it. The
9264 following operations can be performed:
9265
9266 .vlist
9267 .vitem &*${address:*&<&'string'&>&*}*&
9268 .cindex "expansion" "RFC 2822 address handling"
9269 .cindex "&%address%& expansion item"
9270 The string is interpreted as an RFC 2822 address, as it might appear in a
9271 header line, and the effective address is extracted from it. If the string does
9272 not parse successfully, the result is empty.
9273
9274
9275 .vitem &*${addresses:*&<&'string'&>&*}*&
9276 .cindex "expansion" "RFC 2822 address handling"
9277 .cindex "&%addresses%& expansion item"
9278 The string (after expansion) is interpreted as a list of addresses in RFC
9279 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
9280 operative address (&'local-part@domain'&) is extracted from each item, and the
9281 result of the expansion is a colon-separated list, with appropriate
9282 doubling of colons should any happen to be present in the email addresses.
9283 Syntactically invalid RFC2822 address items are omitted from the output.
9284
9285 It is possible to specify a character other than colon for the output
9286 separator by starting the string with > followed by the new separator
9287 character. For example:
9288 .code
9289 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
9290 .endd
9291 expands to &`ceo@up.stairs&&sec@base.ment`&. Compare the &*address*& (singular)
9292 expansion item, which extracts the working address from a single RFC2822
9293 address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
9294 processing lists.
9295
9296
9297 .vitem &*${base62:*&<&'digits'&>&*}*&
9298 .cindex "&%base62%& expansion item"
9299 .cindex "expansion" "conversion to base 62"
9300 The string must consist entirely of decimal digits. The number is converted to
9301 base 62 and output as a string of six characters, including leading zeros. In
9302 the few operating environments where Exim uses base 36 instead of base 62 for
9303 its message identifiers (because those systems do not have case-sensitive file
9304 names), base 36 is used by this operator, despite its name. &*Note*&: Just to
9305 be absolutely clear: this is &'not'& base64 encoding.
9306
9307 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
9308 .cindex "&%base62d%& expansion item"
9309 .cindex "expansion" "conversion to base 62"
9310 The string must consist entirely of base-62 digits, or, in operating
9311 environments where Exim uses base 36 instead of base 62 for its message
9312 identifiers, base-36 digits. The number is converted to decimal and output as a
9313 string.
9314
9315 .vitem &*${domain:*&<&'string'&>&*}*&
9316 .cindex "domain" "extraction"
9317 .cindex "expansion" "domain extraction"
9318 The string is interpreted as an RFC 2822 address and the domain is extracted
9319 from it. If the string does not parse successfully, the result is empty.
9320
9321
9322 .vitem &*${escape:*&<&'string'&>&*}*&
9323 .cindex "expansion" "escaping non-printing characters"
9324 .cindex "&%escape%& expansion item"
9325 If the string contains any non-printing characters, they are converted to
9326 escape sequences starting with a backslash. Whether characters with the most
9327 significant bit set (so-called &"8-bit characters"&) count as printing or not
9328 is controlled by the &%print_topbitchars%& option.
9329
9330
9331 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
9332 .cindex "expansion" "expression evaluation"
9333 .cindex "expansion" "arithmetic expression"
9334 .cindex "&%eval%& expansion item"
9335 These items supports simple arithmetic and bitwise logical operations in
9336 expansion strings. The string (after expansion) must be a conventional
9337 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
9338 logical operators, and parentheses. All operations are carried out using
9339 integer arithmetic. The operator priorities are as follows (the same as in the
9340 C programming language):
9341 .table2 70pt 300pt
9342 .irow &'highest:'& "not (~), negate (-)"
9343 .irow "" "multiply (*), divide (/), remainder (%)"
9344 .irow "" "plus (+), minus (-)"
9345 .irow "" "shift-left (<<), shift-right (>>)"
9346 .irow "" "and (&&)"
9347 .irow "" "xor (^)"
9348 .irow &'lowest:'& "or (|)"
9349 .endtable
9350 Binary operators with the same priority are evaluated from left to right. White
9351 space is permitted before or after operators.
9352
9353 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
9354 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
9355 decimal, even if they start with a leading zero; hexadecimal numbers are not
9356 permitted. This can be useful when processing numbers extracted from dates or
9357 times, which often do have leading zeros.
9358
9359 A number may be followed by &"K"& or &"M"& to multiply it by 1024 or 1024*1024,
9360 respectively. Negative numbers are supported. The result of the computation is
9361 a decimal representation of the answer (without &"K"& or &"M"&). For example:
9362
9363 .display
9364 &`${eval:1+1} `& yields 2
9365 &`${eval:1+2*3} `& yields 7
9366 &`${eval:(1+2)*3} `& yields 9
9367 &`${eval:2+42%5} `& yields 4
9368 &`${eval:0xc&amp;5} `& yields 4
9369 &`${eval:0xc|5} `& yields 13
9370 &`${eval:0xc^5} `& yields 9
9371 &`${eval:0xc>>1} `& yields 6
9372 &`${eval:0xc<<1} `& yields 24
9373 &`${eval:~255&amp;0x1234} `& yields 4608
9374 &`${eval:-(~255&amp;0x1234)} `& yields -4608
9375 .endd
9376
9377 As a more realistic example, in an ACL you might have
9378 .code
9379 deny message = Too many bad recipients
9380 condition = \
9381 ${if and { \
9382 {>{$rcpt_count}{10}} \
9383 { \
9384 < \
9385 {$recipients_count} \
9386 {${eval:$rcpt_count/2}} \
9387 } \
9388 }{yes}{no}}
9389 .endd
9390 The condition is true if there have been more than 10 RCPT commands and
9391 fewer than half of them have resulted in a valid recipient.
9392
9393
9394 .vitem &*${expand:*&<&'string'&>&*}*&
9395 .cindex "expansion" "re-expansion of substring"
9396 The &%expand%& operator causes a string to be expanded for a second time. For
9397 example,
9398 .code
9399 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
9400 .endd
9401 first looks up a string in a file while expanding the operand for &%expand%&,
9402 and then re-expands what it has found.
9403
9404
9405 .vitem &*${from_utf8:*&<&'string'&>&*}*&
9406 .cindex "Unicode"
9407 .cindex "UTF-8" "conversion from"
9408 .cindex "expansion" "UTF-8 conversion"
9409 .cindex "&%from_utf8%& expansion item"
9410 The world is slowly moving towards Unicode, although there are no standards for
9411 email yet. However, other applications (including some databases) are starting
9412 to store data in Unicode, using UTF-8 encoding. This operator converts from a
9413 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
9414 converted to underscores. The input must be a valid UTF-8 string. If it is not,
9415 the result is an undefined sequence of bytes.
9416
9417 Unicode code points with values less than 256 are compatible with ASCII and
9418 ISO-8859-1 (also known as Latin-1).
9419 For example, character 169 is the copyright symbol in both cases, though the
9420 way it is encoded is different. In UTF-8, more than one byte is needed for
9421 characters with code values greater than 127, whereas ISO-8859-1 is a
9422 single-byte encoding (but thereby limited to 256 characters). This makes
9423 translation from UTF-8 to ISO-8859-1 straightforward.
9424
9425
9426 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
9427 .cindex "hash function" "textual"
9428 .cindex "expansion" "textual hash"
9429 The &%hash%& operator is a simpler interface to the hashing function that can
9430 be used when the two parameters are fixed numbers (as opposed to strings that
9431 change when expanded). The effect is the same as
9432 .code
9433 ${hash{<n>}{<m>}{<string>}}
9434 .endd
9435 See the description of the general &%hash%& item above for details. The
9436 abbreviation &%h%& can be used when &%hash%& is used as an operator.
9437
9438
9439
9440 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
9441 .cindex "base64 encoding" "conversion from hex"
9442 .cindex "expansion" "hex to base64"
9443 .cindex "&%hex2b64%& expansion item"
9444 This operator converts a hex string into one that is base64 encoded. This can
9445 be useful for processing the output of the MD5 and SHA-1 hashing functions.
9446
9447
9448 .vitem &*${lc:*&<&'string'&>&*}*&
9449 .cindex "case forcing in strings"
9450 .cindex "string" "case forcing"
9451 .cindex "lower casing"
9452 .cindex "expansion" "case forcing"
9453 .cindex "&%lc%& expansion item"
9454 This forces the letters in the string into lower-case, for example:
9455 .code
9456 ${lc:$local_part}
9457 .endd
9458
9459 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
9460 .cindex "expansion" "string truncation"
9461 .cindex "&%length%& expansion item"
9462 The &%length%& operator is a simpler interface to the &%length%& function that
9463 can be used when the parameter is a fixed number (as opposed to a string that
9464 changes when expanded). The effect is the same as
9465 .code
9466 ${length{<number>}{<string>}}
9467 .endd
9468 See the description of the general &%length%& item above for details. Note that
9469 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
9470 when &%length%& is used as an operator.
9471
9472
9473 .vitem &*${local_part:*&<&'string'&>&*}*&
9474 .cindex "expansion" "local part extraction"
9475 .cindex "&%local_part%& expansion item"
9476 The string is interpreted as an RFC 2822 address and the local part is
9477 extracted from it. If the string does not parse successfully, the result is
9478 empty.
9479
9480
9481 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
9482 .cindex "masked IP address"
9483 .cindex "IP address" "masking"
9484 .cindex "CIDR notation"
9485 .cindex "expansion" "IP address masking"
9486 .cindex "&%mask%& expansion item"
9487 If the form of the string to be operated on is not an IP address followed by a
9488 slash and an integer (that is, a network address in CIDR notation), the
9489 expansion fails. Otherwise, this operator converts the IP address to binary,
9490 masks off the least significant bits according to the bit count, and converts
9491 the result back to text, with mask appended. For example,
9492 .code
9493 ${mask:10.111.131.206/28}
9494 .endd
9495 returns the string &"10.111.131.192/28"&. Since this operation is expected to
9496 be mostly used for looking up masked addresses in files, the result for an IPv6
9497 address uses dots to separate components instead of colons, because colon
9498 terminates a key string in lsearch files. So, for example,
9499 .code
9500 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
9501 .endd
9502 returns the string
9503 .code
9504 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
9505 .endd
9506 Letters in IPv6 addresses are always output in lower case.
9507
9508
9509 .vitem &*${md5:*&<&'string'&>&*}*&
9510 .cindex "MD5 hash"
9511 .cindex "expansion" "MD5 hash"
9512 .cindex "&%md5%& expansion item"
9513 The &%md5%& operator computes the MD5 hash value of the string, and returns it
9514 as a 32-digit hexadecimal number, in which any letters are in lower case.
9515
9516
9517 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
9518 .cindex "expansion" "numeric hash"
9519 .cindex "hash function" "numeric"
9520 The &%nhash%& operator is a simpler interface to the numeric hashing function
9521 that can be used when the two parameters are fixed numbers (as opposed to
9522 strings that change when expanded). The effect is the same as
9523 .code
9524 ${nhash{<n>}{<m>}{<string>}}
9525 .endd
9526 See the description of the general &%nhash%& item above for details.
9527
9528
9529 .vitem &*${quote:*&<&'string'&>&*}*&
9530 .cindex "quoting" "in string expansions"
9531 .cindex "expansion" "quoting"
9532 .cindex "&%quote%& expansion item"
9533 The &%quote%& operator puts its argument into double quotes if it
9534 is an empty string or
9535 contains anything other than letters, digits, underscores, dots, and hyphens.
9536 Any occurrences of double quotes and backslashes are escaped with a backslash.
9537 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
9538 respectively For example,
9539 .code
9540 ${quote:ab"*"cd}
9541 .endd
9542 becomes
9543 .code
9544 "ab\"*\"cd"
9545 .endd
9546 The place where this is useful is when the argument is a substitution from a
9547 variable or a message header.
9548
9549 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
9550 .cindex "&%quote_local_part%& expansion item"
9551 This operator is like &%quote%&, except that it quotes the string only if
9552 required to do so by the rules of RFC 2822 for quoting local parts. For
9553 example, a plus sign would not cause quoting (but it would for &%quote%&).
9554 If you are creating a new email address from the contents of &$local_part$&
9555 (or any other unknown data), you should always use this operator.
9556
9557
9558 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
9559 .cindex "quoting" "lookup-specific"
9560 This operator applies lookup-specific quoting rules to the string. Each
9561 query-style lookup type has its own quoting rules which are described with
9562 the lookups in chapter &<<CHAPfdlookup>>&. For example,
9563 .code
9564 ${quote_ldap:two * two}
9565 .endd
9566 returns
9567 .code
9568 two%20%5C2A%20two
9569 .endd
9570 For single-key lookup types, no quoting is ever necessary and this operator
9571 yields an unchanged string.
9572
9573
9574 .vitem &*${rfc2047:*&<&'string'&>&*}*&
9575 .cindex "expansion" "RFC 2047"
9576 .cindex "RFC 2047" "expansion operator"
9577 .cindex "&%rfc2047%& expansion item"
9578 This operator encodes text according to the rules of RFC 2047. This is an
9579 encoding that is used in header lines to encode non-ASCII characters. It is
9580 assumed that the input string is in the encoding specified by the
9581 &%headers_charset%& option, which defaults to ISO-8859-1. If the string
9582 contains only characters in the range 33&--126, and no instances of the
9583 characters
9584 .code
9585 ? = ( ) < > @ , ; : \ " . [ ] _
9586 .endd
9587 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
9588 string, using as many &"encoded words"& as necessary to encode all the
9589 characters.
9590
9591
9592 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
9593 .cindex "expansion" "RFC 2047"
9594 .cindex "RFC 2047" "decoding"
9595 .cindex "&%rfc2047d%& expansion item"
9596 This operator decodes strings that are encoded as per RFC 2047. Binary zero
9597 bytes are replaced by question marks. Characters are converted into the
9598 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
9599 not recognized unless &%check_rfc2047_length%& is set false.
9600
9601 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
9602 access a header line, RFC 2047 decoding is done automatically. You do not need
9603 to use this operator as well.
9604
9605
9606
9607 .vitem &*${rxquote:*&<&'string'&>&*}*&
9608 .cindex "quoting" "in regular expressions"
9609 .cindex "regular expressions" "quoting"
9610 .cindex "&%rxquote%& expansion item"
9611 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
9612 characters in its argument. This is useful when substituting the values of
9613 variables or headers inside regular expressions.
9614
9615
9616 .vitem &*${sha1:*&<&'string'&>&*}*&
9617 .cindex "SHA-1 hash"
9618 .cindex "expansion" "SHA-1 hashing"
9619 .cindex "&%sha2%& expansion item"
9620 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
9621 it as a 40-digit hexadecimal number, in which any letters are in upper case.
9622
9623
9624 .vitem &*${stat:*&<&'string'&>&*}*&
9625 .cindex "expansion" "statting a file"
9626 .cindex "file" "extracting characteristics"
9627 .cindex "&%stat%& expansion item"
9628 The string, after expansion, must be a file path. A call to the &[stat()]&
9629 function is made for this path. If &[stat()]& fails, an error occurs and the
9630 expansion fails. If it succeeds, the data from the stat replaces the item, as a
9631 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
9632 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
9633 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
9634 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
9635 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
9636 can extract individual fields using the &%extract%& expansion item.
9637
9638 The use of the &%stat%& expansion in users' filter files can be locked out by
9639 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
9640 systems for files larger than 2GB.
9641
9642 .vitem &*${str2b64:*&<&'string'&>&*}*&
9643 .cindex "expansion" "base64 encoding"
9644 .cindex "base64 encoding" "in string expansion"
9645 .cindex "&%str2b64%& expansion item"
9646 This operator converts a string into one that is base64 encoded.
9647
9648
9649
9650 .vitem &*${strlen:*&<&'string'&>&*}*&
9651 .cindex "expansion" "string length"
9652 .cindex "string" "length in expansion"
9653 .cindex "&%strlen%& expansion item"
9654 The item is replace by the length of the expanded string, expressed as a
9655 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
9656
9657
9658 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
9659 .cindex "&%substr%& expansion item"
9660 .cindex "substring extraction"
9661 .cindex "expansion" "substring expansion"
9662 The &%substr%& operator is a simpler interface to the &%substr%& function that
9663 can be used when the two parameters are fixed numbers (as opposed to strings
9664 that change when expanded). The effect is the same as
9665 .code
9666 ${substr{<start>}{<length>}{<string>}}
9667 .endd
9668 See the description of the general &%substr%& item above for details. The
9669 abbreviation &%s%& can be used when &%substr%& is used as an operator.
9670
9671 .vitem &*${time_eval:*&<&'string'&>&*}*&
9672 .cindex "&%time_eval%& expansion item"
9673 .cindex "time interval" "decoding"
9674 This item converts an Exim time interval such as &`2d4h5m`& into a number of
9675 seconds.
9676
9677 .vitem &*${time_interval:*&<&'string'&>&*}*&
9678 .cindex "&%time_interval%& expansion item"
9679 .cindex "time interval" "formatting"
9680 The argument (after sub-expansion) must be a sequence of decimal digits that
9681 represents an interval of time as a number of seconds. It is converted into a
9682 number of larger units and output in Exim's normal time format, for example,
9683 &`1w3d4h2m6s`&.
9684
9685 .vitem &*${uc:*&<&'string'&>&*}*&
9686 .cindex "case forcing in strings"
9687 .cindex "string" "case forcing"
9688 .cindex "upper casing"
9689 .cindex "expansion" "case forcing"
9690 .cindex "&%uc%& expansion item"
9691 This forces the letters in the string into upper-case.
9692 .endlist
9693
9694
9695
9696
9697
9698
9699 .section "Expansion conditions" "SECTexpcond"
9700 .scindex IIDexpcond "expansion" "conditions"
9701 The following conditions are available for testing by the &%${if%& construct
9702 while expanding strings:
9703
9704 .vlist
9705 .vitem &*!*&<&'condition'&>
9706 .cindex "expansion" "negating a condition"
9707 .cindex "negation" "in expansion condition"
9708 Preceding any condition with an exclamation mark negates the result of the
9709 condition.
9710
9711 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9712 .cindex "numeric comparison"
9713 .cindex "expansion" "numeric comparison"
9714 There are a number of symbolic operators for doing numeric comparisons. They
9715 are:
9716 .display
9717 &`= `& equal
9718 &`== `& equal
9719 &`> `& greater
9720 &`>= `& greater or equal
9721 &`< `& less
9722 &`<= `& less or equal
9723 .endd
9724 For example:
9725 .code
9726 ${if >{$message_size}{10M} ...
9727 .endd
9728 Note that the general negation operator provides for inequality testing. The
9729 two strings must take the form of optionally signed decimal integers,
9730 optionally followed by one of the letters &"K"& or &"M"& (in either upper or
9731 lower case), signifying multiplication by 1024 or 1024*1024, respectively.
9732 As a special case, the numerical value of an empty string is taken as
9733 zero.
9734
9735 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9736 .cindex "expansion" "encrypted comparison"
9737 .cindex "encrypted strings, comparing"
9738 .cindex "&%crypteq%& expansion condition"
9739 This condition is included in the Exim binary if it is built to support any
9740 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
9741 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
9742 included in the binary.
9743
9744 The &%crypteq%& condition has two arguments. The first is encrypted and
9745 compared against the second, which is already encrypted. The second string may
9746 be in the LDAP form for storing encrypted strings, which starts with the
9747 encryption type in curly brackets, followed by the data. If the second string
9748 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
9749 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
9750 Typically this will be a field from a password file. An example of an encrypted
9751 string in LDAP form is:
9752 .code
9753 {md5}CY9rzUYh03PK3k6DJie09g==
9754 .endd
9755 If such a string appears directly in an expansion, the curly brackets have to
9756 be quoted, because they are part of the expansion syntax. For example:
9757 .code
9758 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
9759 .endd
9760 The following encryption types (whose names are matched case-independently) are
9761 supported:
9762
9763 .ilist
9764 .cindex "MD5 hash"
9765 .cindex "base64 encoding" "in encrypted password"
9766 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
9767 printable characters to compare with the remainder of the second string. If the
9768 length of the comparison string is 24, Exim assumes that it is base64 encoded
9769 (as in the above example). If the length is 32, Exim assumes that it is a
9770 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
9771 comparison fails.
9772
9773 .next
9774 .cindex "SHA-1 hash"
9775 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
9776 printable characters to compare with the remainder of the second string. If the
9777 length of the comparison string is 28, Exim assumes that it is base64 encoded.
9778 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
9779 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
9780
9781 .next
9782 .cindex "&[crypt()]&"
9783 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
9784 only the first eight characters of the password. However, in modern operating
9785 systems this is no longer true, and in many cases the entire password is used,
9786 whatever its length.
9787
9788 .next
9789 .cindex "&[crypt16()]&"
9790 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
9791 use up to 16 characters of the password in some operating systems. Again, in
9792 modern operating systems, more characters may be used.
9793 .endlist
9794 Exim has its own version of &[crypt16()]&, which is just a double call to
9795 &[crypt()]&. For operating systems that have their own version, setting
9796 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
9797 operating system version instead of its own. This option is set by default in
9798 the OS-dependent &_Makefile_& for those operating systems that are known to
9799 support &[crypt16()]&.
9800
9801 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
9802 it was not using the same algorithm as some operating systems' versions. It
9803 turns out that as well as &[crypt16()]& there is a function called
9804 &[bigcrypt()]& in some operating systems. This may or may not use the same
9805 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
9806
9807 However, since there is now a move away from the traditional &[crypt()]&
9808 functions towards using SHA1 and other algorithms, tidying up this area of
9809 Exim is seen as very low priority.
9810
9811 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
9812 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
9813 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
9814 default is &`{crypt}`&. Whatever the default, you can always use either
9815 function by specifying it explicitly in curly brackets.
9816
9817 .vitem &*def:*&<&'variable&~name'&>
9818 .cindex "expansion" "checking for empty variable"
9819 .cindex "&%def%& expansion condition"
9820 The &%def%& condition must be followed by the name of one of the expansion
9821 variables defined in section &<<SECTexpvar>>&. The condition is true if the
9822 variable does not contain the empty string. For example:
9823 .code
9824 ${if def:sender_ident {from $sender_ident}}
9825 .endd
9826 Note that the variable name is given without a leading &%$%& character. If the
9827 variable does not exist, the expansion fails.
9828
9829 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
9830 &~&*def:h_*&<&'header&~name'&>&*:*&"
9831 .cindex "expansion" "checking header line existence"
9832 This condition is true if a message is being processed and the named header
9833 exists in the message. For example,
9834 .code
9835 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
9836 .endd
9837 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
9838 the header name must be terminated by a colon if white space does not follow.
9839
9840 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
9841 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9842 .cindex "string" "comparison"
9843 .cindex "expansion" "string comparison"
9844 .cindex "&%eq%& expansion condition"
9845 .cindex "&%eqi%& expansion condition"
9846 The two substrings are first expanded. The condition is true if the two
9847 resulting strings are identical. For &%eq%& the comparison includes the case of
9848 letters, whereas for &%eqi%& the comparison is case-independent.
9849
9850 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
9851 .cindex "expansion" "file existence test"
9852 .cindex "file" "existence test"
9853 .cindex "&%exists%&, expansion condition"
9854 The substring is first expanded and then interpreted as an absolute path. The
9855 condition is true if the named file (or directory) exists. The existence test
9856 is done by calling the &[stat()]& function. The use of the &%exists%& test in
9857 users' filter files may be locked out by the system administrator.
9858
9859 .vitem &*first_delivery*&
9860 .cindex "delivery" "first"
9861 .cindex "first delivery"
9862 .cindex "expansion" "first delivery test"
9863 .cindex "&%first_delivery%& expansion condition"
9864 This condition, which has no data, is true during a message's first delivery
9865 attempt. It is false during any subsequent delivery attempts.
9866
9867
9868 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
9869 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
9870 .cindex "list" "iterative conditions"
9871 .cindex "expansion" "&*forall*& condition"
9872 .cindex "expansion" "&*forany*& condition"
9873 .vindex "&$item$&"
9874 These conditions iterate over a list. The first argument is expanded to form
9875 the list. By default, the list separator is a colon, but it can be changed by
9876 the normal method. The second argument is interpreted as a condition that is to
9877 be applied to each item in the list in turn. During the interpretation of the
9878 condition, the current list item is placed in a variable called &$item$&.
9879 .ilist
9880 For &*forany*&, interpretation stops if the condition is true for any item, and
9881 the result of the whole condition is true. If the condition is false for all
9882 items in the list, the overall condition is false.
9883 .next
9884 For &*forall*&, interpretation stops if the condition is false for any item,
9885 and the result of the whole condition is false. If the condition is true for
9886 all items in the list, the overall condition is true.
9887 .endlist
9888 Note that negation of &*forany*& means that the condition must be false for all
9889 items for the overall condition to succeed, and negation of &*forall*& means
9890 that the condition must be false for at least one item. In this example, the
9891 list separator is changed to a comma:
9892 .code
9893 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
9894 .endd
9895 The value of &$item$& is saved and restored while &*forany*& or &*forall*& is
9896 being processed, to enable these expansion items to be nested.
9897
9898
9899 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
9900 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9901 .cindex "string" "comparison"
9902 .cindex "expansion" "string comparison"
9903 .cindex "&%ge%& expansion condition"
9904 .cindex "&%gei%& expansion condition"
9905 The two substrings are first expanded. The condition is true if the first
9906 string is lexically greater than or equal to the second string. For &%ge%& the
9907 comparison includes the case of letters, whereas for &%gei%& the comparison is
9908 case-independent.
9909
9910 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
9911 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9912 .cindex "string" "comparison"
9913 .cindex "expansion" "string comparison"
9914 .cindex "&%gt%& expansion condition"
9915 .cindex "&%gti%& expansion condition"
9916 The two substrings are first expanded. The condition is true if the first
9917 string is lexically greater than the second string. For &%gt%& the comparison
9918 includes the case of letters, whereas for &%gti%& the comparison is
9919 case-independent.
9920
9921 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
9922 &*isip4&~{*&<&'string'&>&*}*& &&&
9923 &*isip6&~{*&<&'string'&>&*}*&
9924 .cindex "IP address" "testing string format"
9925 .cindex "string" "testing for IP address"
9926 .cindex "&%isip%& expansion condition"
9927 .cindex "&%isip4%& expansion condition"
9928 .cindex "&%isip6%& expansion condition"
9929 The substring is first expanded, and then tested to see if it has the form of
9930 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
9931 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
9932
9933 For an IPv4 address, the test is for four dot-separated components, each of
9934 which consists of from one to three digits. For an IPv6 address, up to eight
9935 colon-separated components are permitted, each containing from one to four
9936 hexadecimal digits. There may be fewer than eight components if an empty
9937 component (adjacent colons) is present. Only one empty component is permitted.
9938
9939 &*Note*&: The checks are just on the form of the address; actual numerical
9940 values are not considered. Thus, for example, 999.999.999.999 passes the IPv4
9941 check. The main use of these tests is to distinguish between IP addresses and
9942 host names, or between IPv4 and IPv6 addresses. For example, you could use
9943 .code
9944 ${if isip4{$sender_host_address}...
9945 .endd
9946 to test which IP version an incoming SMTP connection is using.
9947
9948 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
9949 .cindex "LDAP" "use for authentication"
9950 .cindex "expansion" "LDAP authentication test"
9951 .cindex "&%ldapauth%& expansion condition"
9952 This condition supports user authentication using LDAP. See section
9953 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
9954 queries. For this use, the query must contain a user name and password. The
9955 query itself is not used, and can be empty. The condition is true if the
9956 password is not empty, and the user name and password are accepted by the LDAP
9957 server. An empty password is rejected without calling LDAP because LDAP binds
9958 with an empty password are considered anonymous regardless of the username, and
9959 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
9960 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
9961 this can be used.
9962
9963
9964 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
9965 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9966 .cindex "string" "comparison"
9967 .cindex "expansion" "string comparison"
9968 .cindex "&%le%& expansion condition"
9969 .cindex "&%lei%& expansion condition"
9970 The two substrings are first expanded. The condition is true if the first
9971 string is lexically less than or equal to the second string. For &%le%& the
9972 comparison includes the case of letters, whereas for &%lei%& the comparison is
9973 case-independent.
9974
9975 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
9976 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9977 .cindex "string" "comparison"
9978 .cindex "expansion" "string comparison"
9979 .cindex "&%lt%& expansion condition"
9980 .cindex "&%lti%& expansion condition"
9981 The two substrings are first expanded. The condition is true if the first
9982 string is lexically less than the second string. For &%lt%& the comparison
9983 includes the case of letters, whereas for &%lti%& the comparison is
9984 case-independent.
9985
9986
9987 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9988 .cindex "expansion" "regular expression comparison"
9989 .cindex "regular expressions" "match in expanded string"
9990 .cindex "&%match%& expansion condition"
9991 The two substrings are first expanded. The second is then treated as a regular
9992 expression and applied to the first. Because of the pre-expansion, if the
9993 regular expression contains dollar, or backslash characters, they must be
9994 escaped. Care must also be taken if the regular expression contains braces
9995 (curly brackets). A closing brace must be escaped so that it is not taken as a
9996 premature termination of <&'string2'&>. The easiest approach is to use the
9997 &`\N`& feature to disable expansion of the regular expression.
9998 For example,
9999 .code
10000 ${if match {$local_part}{\N^\d{3}\N} ...
10001 .endd
10002 If the whole expansion string is in double quotes, further escaping of
10003 backslashes is also required.
10004
10005 The condition is true if the regular expression match succeeds.
10006 The regular expression is not required to begin with a circumflex
10007 metacharacter, but if there is no circumflex, the expression is not anchored,
10008 and it may match anywhere in the subject, not just at the start. If you want
10009 the pattern to match at the end of the subject, you must include the &`$`&
10010 metacharacter at an appropriate point.
10011
10012 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
10013 At the start of an &%if%& expansion the values of the numeric variable
10014 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
10015 succeeds causes them to be reset to the substrings of that condition and they
10016 will have these values during the expansion of the success string. At the end
10017 of the &%if%& expansion, the previous values are restored. After testing a
10018 combination of conditions using &%or%&, the subsequent values of the numeric
10019 variables are those of the condition that succeeded.
10020
10021 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10022 .cindex "&%match_address%& expansion condition"
10023 See &*match_local_part*&.
10024
10025 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10026 .cindex "&%match_domain%& expansion condition"
10027 See &*match_local_part*&.
10028
10029 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10030 .cindex "&%match_ip%& expansion condition"
10031 This condition matches an IP address to a list of IP address patterns. It must
10032 be followed by two argument strings. The first (after expansion) must be an IP
10033 address or an empty string. The second (after expansion) is a restricted host
10034 list that can match only an IP address, not a host name. For example:
10035 .code
10036 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
10037 .endd
10038 The specific types of host list item that are permitted in the list are:
10039
10040 .ilist
10041 An IP address, optionally with a CIDR mask.
10042 .next
10043 A single asterisk, which matches any IP address.
10044 .next
10045 An empty item, which matches only if the IP address is empty. This could be
10046 useful for testing for a locally submitted message or one from specific hosts
10047 in a single test such as
10048 . ==== As this is a nested list, any displays it contains must be indented
10049 . ==== as otherwise they are too far to the left. This comment applies to
10050 . ==== the use of xmlto plus fop. There's no problem when formatting with
10051 . ==== sdop, with or without the extra indent.
10052 .code
10053 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
10054 .endd
10055 where the first item in the list is the empty string.
10056 .next
10057 The item @[] matches any of the local host's interface addresses.
10058 .next
10059 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
10060 even if &`net-`& is not specified. There is never any attempt to turn the IP
10061 address into a host name. The most common type of linear search for
10062 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
10063 masks. For example:
10064 .code
10065 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
10066 .endd
10067 It is of course possible to use other kinds of lookup, and in such a case, you
10068 do need to specify the &`net-`& prefix if you want to specify a specific
10069 address mask, for example:
10070 .code
10071 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
10072 .endd
10073 However, unless you are combining a &%match_ip%& condition with others, it is
10074 just as easy to use the fact that a lookup is itself a condition, and write:
10075 .code
10076 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
10077 .endd
10078 .endlist ilist
10079
10080 Consult section &<<SECThoslispatip>>& for further details of these patterns.
10081
10082 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10083 .cindex "domain list" "in expansion condition"
10084 .cindex "address list" "in expansion condition"
10085 .cindex "local part" "list, in expansion condition"
10086 .cindex "&%match_local_part%& expansion condition"
10087 This condition, together with &%match_address%& and &%match_domain%&, make it
10088 possible to test domain, address, and local part lists within expansions. Each
10089 condition requires two arguments: an item and a list to match. A trivial
10090 example is:
10091 .code
10092 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
10093 .endd
10094 In each case, the second argument may contain any of the allowable items for a
10095 list of the appropriate type. Also, because the second argument (after
10096 expansion) is a standard form of list, it is possible to refer to a named list.
10097 Thus, you can use conditions like this:
10098 .code
10099 ${if match_domain{$domain}{+local_domains}{...
10100 .endd
10101 .cindex "&`+caseful`&"
10102 For address lists, the matching starts off caselessly, but the &`+caseful`&
10103 item can be used, as in all address lists, to cause subsequent items to
10104 have their local parts matched casefully. Domains are always matched
10105 caselessly.
10106
10107 &*Note*&: Host lists are &'not'& supported in this way. This is because
10108 hosts have two identities: a name and an IP address, and it is not clear
10109 how to specify cleanly how such a test would work. However, IP addresses can be
10110 matched using &%match_ip%&.
10111
10112 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
10113 .cindex "PAM authentication"
10114 .cindex "AUTH" "with PAM"
10115 .cindex "Solaris" "PAM support"
10116 .cindex "expansion" "PAM authentication test"
10117 .cindex "&%pam%& expansion condition"
10118 &'Pluggable Authentication Modules'&
10119 (&url(http://www.kernel.org/pub/linux/libs/pam/)) are a facility that is
10120 available in the latest releases of Solaris and in some GNU/Linux
10121 distributions. The Exim support, which is intended for use in conjunction with
10122 the SMTP AUTH command, is available only if Exim is compiled with
10123 .code
10124 SUPPORT_PAM=yes
10125 .endd
10126 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
10127 in some releases of GNU/Linux &%-ldl%& is also needed.
10128
10129 The argument string is first expanded, and the result must be a
10130 colon-separated list of strings. Leading and trailing white space is ignored.
10131 The PAM module is initialized with the service name &"exim"& and the user name
10132 taken from the first item in the colon-separated data string (<&'string1'&>).
10133 The remaining items in the data string are passed over in response to requests
10134 from the authentication function. In the simple case there will only be one
10135 request, for a password, so the data consists of just two strings.
10136
10137 There can be problems if any of the strings are permitted to contain colon
10138 characters. In the usual way, these have to be doubled to avoid being taken as
10139 separators. If the data is being inserted from a variable, the &%sg%& expansion
10140 item can be used to double any existing colons. For example, the configuration
10141 of a LOGIN authenticator might contain this setting:
10142 .code
10143 server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
10144 .endd
10145 For a PLAIN authenticator you could use:
10146 .code
10147 server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
10148 .endd
10149 In some operating systems, PAM authentication can be done only from a process
10150 running as root. Since Exim is running as the Exim user when receiving
10151 messages, this means that PAM cannot be used directly in those systems.
10152 A patched version of the &'pam_unix'& module that comes with the
10153 Linux PAM package is available from &url(http://www.e-admin.de/pam_exim/).
10154 The patched module allows one special uid/gid combination, in addition to root,
10155 to authenticate. If you build the patched module to allow the Exim user and
10156 group, PAM can then be used from an Exim authenticator.
10157
10158
10159 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
10160 .cindex "&'pwcheck'& daemon"
10161 .cindex "Cyrus"
10162 .cindex "expansion" "&'pwcheck'& authentication test"
10163 .cindex "&%pwcheck%& expansion condition"
10164 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
10165 This is one way of making it possible for passwords to be checked by a process
10166 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
10167 deprecated. Its replacement is &'saslauthd'& (see below).
10168
10169 The pwcheck support is not included in Exim by default. You need to specify
10170 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
10171 building Exim. For example:
10172 .code
10173 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
10174 .endd
10175 You do not need to install the full Cyrus software suite in order to use
10176 the pwcheck daemon. You can compile and install just the daemon alone
10177 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
10178 access to the &_/var/pwcheck_& directory.
10179
10180 The &%pwcheck%& condition takes one argument, which must be the user name and
10181 password, separated by a colon. For example, in a LOGIN authenticator
10182 configuration, you might have this:
10183 .code
10184 server_condition = ${if pwcheck{$auth1:$auth2}}
10185 .endd
10186 .vitem &*queue_running*&
10187 .cindex "queue runner" "detecting when delivering from"
10188 .cindex "expansion" "queue runner test"
10189 .cindex "&%queue_running%& expansion condition"
10190 This condition, which has no data, is true during delivery attempts that are
10191 initiated by queue runner processes, and false otherwise.
10192
10193
10194 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
10195 .cindex "Radius"
10196 .cindex "expansion" "Radius authentication"
10197 .cindex "&%radius%& expansion condition"
10198 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
10199 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
10200 the Radius client configuration file in order to build Exim with Radius
10201 support.
10202
10203 With just that one setting, Exim expects to be linked with the &%radiusclient%&
10204 library, using the original API. If you are using release 0.4.0 or later of
10205 this library, you need to set
10206 .code
10207 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
10208 .endd
10209 in &_Local/Makefile_& when building Exim. You can also link Exim with the
10210 &%libradius%& library that comes with FreeBSD. To do this, set
10211 .code
10212 RADIUS_LIB_TYPE=RADLIB
10213 .endd
10214 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
10215 You may also have to supply a suitable setting in EXTRALIBS so that the
10216 Radius library can be found when Exim is linked.
10217
10218 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
10219 Radius client library, which calls the Radius server. The condition is true if
10220 the authentication is successful. For example:
10221 .code
10222 server_condition = ${if radius{<arguments>}}
10223 .endd
10224
10225
10226 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
10227 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
10228 .cindex "&'saslauthd'& daemon"
10229 .cindex "Cyrus"
10230 .cindex "expansion" "&'saslauthd'& authentication test"
10231 .cindex "&%saslauthd%& expansion condition"
10232 This condition supports user authentication using the Cyrus &'saslauthd'&
10233 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
10234 Using this daemon is one way of making it possible for passwords to be checked
10235 by a process that is not running as root.
10236
10237 The saslauthd support is not included in Exim by default. You need to specify
10238 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
10239 building Exim. For example:
10240 .code
10241 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
10242 .endd
10243 You do not need to install the full Cyrus software suite in order to use
10244 the saslauthd daemon. You can compile and install just the daemon alone
10245 from the Cyrus SASL library.
10246
10247 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
10248 two are mandatory. For example:
10249 .code
10250 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
10251 .endd
10252 The service and the realm are optional (which is why the arguments are enclosed
10253 in their own set of braces). For details of the meaning of the service and
10254 realm, and how to run the daemon, consult the Cyrus documentation.
10255 .endlist vlist
10256
10257
10258
10259 .section "Combining expansion conditions" "SECID84"
10260 .cindex "expansion" "combining conditions"
10261 Several conditions can be tested at once by combining them using the &%and%&
10262 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
10263 conditions on their own, and precede their lists of sub-conditions. Each
10264 sub-condition must be enclosed in braces within the overall braces that contain
10265 the list. No repetition of &%if%& is used.
10266
10267
10268 .vlist
10269 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
10270 .cindex "&""or""& expansion condition"
10271 .cindex "expansion" "&""or""& of conditions"
10272 The sub-conditions are evaluated from left to right. The condition is true if
10273 any one of the sub-conditions is true.
10274 For example,
10275 .code
10276 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
10277 .endd
10278 When a true sub-condition is found, the following ones are parsed but not
10279 evaluated. If there are several &"match"& sub-conditions the values of the
10280 numeric variables afterwards are taken from the first one that succeeds.
10281
10282 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
10283 .cindex "&""and""& expansion condition"
10284 .cindex "expansion" "&""and""& of conditions"
10285 The sub-conditions are evaluated from left to right. The condition is true if
10286 all of the sub-conditions are true. If there are several &"match"&
10287 sub-conditions, the values of the numeric variables afterwards are taken from
10288 the last one. When a false sub-condition is found, the following ones are
10289 parsed but not evaluated.
10290 .endlist
10291 .ecindex IIDexpcond
10292
10293
10294
10295
10296 .section "Expansion variables" "SECTexpvar"
10297 .cindex "expansion" "variables, list of"
10298 This section contains an alphabetical list of all the expansion variables. Some
10299 of them are available only when Exim is compiled with specific options such as
10300 support for TLS or the content scanning extension.
10301
10302 .vlist
10303 .vitem "&$0$&, &$1$&, etc"
10304 .cindex "numerical variables (&$1$& &$2$& etc)"
10305 When a &%match%& expansion condition succeeds, these variables contain the
10306 captured substrings identified by the regular expression during subsequent
10307 processing of the success string of the containing &%if%& expansion item.
10308 However, they do not retain their values afterwards; in fact, their previous
10309 values are restored at the end of processing an &%if%& item. The numerical
10310 variables may also be set externally by some other matching process which
10311 precedes the expansion of the string. For example, the commands available in
10312 Exim filter files include an &%if%& command with its own regular expression
10313 matching condition.
10314
10315 .vitem "&$acl_c...$&"
10316 Values can be placed in these variables by the &%set%& modifier in an ACL. They
10317 can be given any name that starts with &$acl_c$& and is at least six characters
10318 long, but the sixth character must be either a digit or an underscore. For
10319 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
10320 variables persist throughout the lifetime of an SMTP connection. They can be
10321 used to pass information between ACLs and between different invocations of the
10322 same ACL. When a message is received, the values of these variables are saved
10323 with the message, and can be accessed by filters, routers, and transports
10324 during subsequent delivery.
10325
10326 .vitem "&$acl_m...$&"
10327 These variables are like the &$acl_c...$& variables, except that their values
10328 are reset after a message has been received. Thus, if several messages are
10329 received in one SMTP connection, &$acl_m...$& values are not passed on from one
10330 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
10331 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
10332 message is received, the values of these variables are saved with the message,
10333 and can be accessed by filters, routers, and transports during subsequent
10334 delivery.
10335
10336 .vitem &$acl_verify_message$&
10337 .vindex "&$acl_verify_message$&"
10338 After an address verification has failed, this variable contains the failure
10339 message. It retains its value for use in subsequent modifiers. The message can
10340 be preserved by coding like this:
10341 .code
10342 warn !verify = sender
10343 set acl_m0 = $acl_verify_message
10344 .endd
10345 You can use &$acl_verify_message$& during the expansion of the &%message%& or
10346 &%log_message%& modifiers, to include information about the verification
10347 failure.
10348
10349 .vitem &$address_data$&
10350 .vindex "&$address_data$&"
10351 This variable is set by means of the &%address_data%& option in routers. The
10352 value then remains with the address while it is processed by subsequent routers
10353 and eventually a transport. If the transport is handling multiple addresses,
10354 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
10355 for more details. &*Note*&: The contents of &$address_data$& are visible in
10356 user filter files.
10357
10358 If &$address_data$& is set when the routers are called from an ACL to verify
10359 a recipient address, the final value is still in the variable for subsequent
10360 conditions and modifiers of the ACL statement. If routing the address caused it
10361 to be redirected to just one address, the child address is also routed as part
10362 of the verification, and in this case the final value of &$address_data$& is
10363 from the child's routing.
10364
10365 If &$address_data$& is set when the routers are called from an ACL to verify a
10366 sender address, the final value is also preserved, but this time in
10367 &$sender_address_data$&, to distinguish it from data from a recipient
10368 address.
10369
10370 In both cases (recipient and sender verification), the value does not persist
10371 after the end of the current ACL statement. If you want to preserve
10372 these values for longer, you can save them in ACL variables.
10373
10374 .vitem &$address_file$&
10375 .vindex "&$address_file$&"
10376 When, as a result of aliasing, forwarding, or filtering, a message is directed
10377 to a specific file, this variable holds the name of the file when the transport
10378 is running. At other times, the variable is empty. For example, using the
10379 default configuration, if user &%r2d2%& has a &_.forward_& file containing
10380 .code
10381 /home/r2d2/savemail
10382 .endd
10383 then when the &(address_file)& transport is running, &$address_file$&
10384 contains the text string &`/home/r2d2/savemail`&.
10385 .cindex "Sieve filter" "value of &$address_file$&"
10386 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
10387 then up to the transport configuration to generate an appropriate absolute path
10388 to the relevant file.
10389
10390 .vitem &$address_pipe$&
10391 .vindex "&$address_pipe$&"
10392 When, as a result of aliasing or forwarding, a message is directed to a pipe,
10393 this variable holds the pipe command when the transport is running.
10394
10395 .vitem "&$auth1$& &-- &$auth3$&"
10396 .vindex "&$auth1$&, &$auth2$&, etc"
10397 These variables are used in SMTP authenticators (see chapters
10398 &<<CHAPplaintext>>&&--&<<CHAPspa>>&). Elsewhere, they are empty.
10399
10400 .vitem &$authenticated_id$&
10401 .cindex "authentication" "id"
10402 .vindex "&$authenticated_id$&"
10403 When a server successfully authenticates a client it may be configured to
10404 preserve some of the authentication information in the variable
10405 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
10406 user/password authenticator configuration might preserve the user name for use
10407 in the routers. Note that this is not the same information that is saved in
10408 &$sender_host_authenticated$&.
10409 When a message is submitted locally (that is, not over a TCP connection)
10410 the value of &$authenticated_id$& is normally the login name of the calling
10411 process. However, a trusted user can override this by means of the &%-oMai%&
10412 command line option.
10413
10414
10415
10416
10417 .vitem &$authenticated_sender$&
10418 .cindex "sender" "authenticated"
10419 .cindex "authentication" "sender"
10420 .cindex "AUTH" "on MAIL command"
10421 .vindex "&$authenticated_sender$&"
10422 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
10423 SMTP MAIL command if it believes the sender is sufficiently trusted, as
10424 described in section &<<SECTauthparamail>>&. Unless the data is the string
10425 &"<>"&, it is set as the authenticated sender of the message, and the value is
10426 available during delivery in the &$authenticated_sender$& variable. If the
10427 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
10428
10429 .vindex "&$qualify_domain$&"
10430 When a message is submitted locally (that is, not over a TCP connection), the
10431 value of &$authenticated_sender$& is an address constructed from the login
10432 name of the calling process and &$qualify_domain$&, except that a trusted user
10433 can override this by means of the &%-oMas%& command line option.
10434
10435
10436 .vitem &$authentication_failed$&
10437 .cindex "authentication" "failure"
10438 .vindex "&$authentication_failed$&"
10439 This variable is set to &"1"& in an Exim server if a client issues an AUTH
10440 command that does not succeed. Otherwise it is set to &"0"&. This makes it
10441 possible to distinguish between &"did not try to authenticate"&
10442 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
10443 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
10444 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
10445 negative response to an AUTH command, including (for example) an attempt to use
10446 an undefined mechanism.
10447
10448 .vitem &$body_linecount$&
10449 .cindex "message body" "line count"
10450 .cindex "body of message" "line count"
10451 .vindex "&$body_linecount$&"
10452 When a message is being received or delivered, this variable contains the
10453 number of lines in the message's body. See also &$message_linecount$&.
10454
10455 .vitem &$body_zerocount$&
10456 .cindex "message body" "binary zero count"
10457 .cindex "body of message" "binary zero count"
10458 .cindex "binary zero" "in message body"
10459 .vindex "&$body_zerocount$&"
10460 When a message is being received or delivered, this variable contains the
10461 number of binary zero bytes in the message's body.
10462
10463 .vitem &$bounce_recipient$&
10464 .vindex "&$bounce_recipient$&"
10465 This is set to the recipient address of a bounce message while Exim is creating
10466 it. It is useful if a customized bounce message text file is in use (see
10467 chapter &<<CHAPemsgcust>>&).
10468
10469 .vitem &$bounce_return_size_limit$&
10470 .vindex "&$bounce_return_size_limit$&"
10471 This contains the value set in the &%bounce_return_size_limit%& option, rounded
10472 up to a multiple of 1000. It is useful when a customized error message text
10473 file is in use (see chapter &<<CHAPemsgcust>>&).
10474
10475 .vitem &$caller_gid$&
10476 .cindex "gid (group id)" "caller"
10477 .vindex "&$caller_gid$&"
10478 The real group id under which the process that called Exim was running. This is
10479 not the same as the group id of the originator of a message (see
10480 &$originator_gid$&). If Exim re-execs itself, this variable in the new
10481 incarnation normally contains the Exim gid.
10482
10483 .vitem &$caller_uid$&
10484 .cindex "uid (user id)" "caller"
10485 .vindex "&$caller_uid$&"
10486 The real user id under which the process that called Exim was running. This is
10487 not the same as the user id of the originator of a message (see
10488 &$originator_uid$&). If Exim re-execs itself, this variable in the new
10489 incarnation normally contains the Exim uid.
10490
10491 .vitem &$compile_date$&
10492 .vindex "&$compile_date$&"
10493 The date on which the Exim binary was compiled.
10494
10495 .vitem &$compile_number$&
10496 .vindex "&$compile_number$&"
10497 The building process for Exim keeps a count of the number
10498 of times it has been compiled. This serves to distinguish different
10499 compilations of the same version of the program.
10500
10501 .vitem &$demime_errorlevel$&
10502 .vindex "&$demime_errorlevel$&"
10503 This variable is available when Exim is compiled with
10504 the content-scanning extension and the obsolete &%demime%& condition. For
10505 details, see section &<<SECTdemimecond>>&.
10506
10507 .vitem &$demime_reason$&
10508 .vindex "&$demime_reason$&"
10509 This variable is available when Exim is compiled with the
10510 content-scanning extension and the obsolete &%demime%& condition. For details,
10511 see section &<<SECTdemimecond>>&.
10512
10513 .vitem &$dnslist_domain$& &&&
10514 &$dnslist_matched$& &&&
10515 &$dnslist_text$& &&&
10516 &$dnslist_value$&
10517 .vindex "&$dnslist_domain$&"
10518 .vindex "&$dnslist_matched$&"
10519 .vindex "&$dnslist_text$&"
10520 .vindex "&$dnslist_value$&"
10521 .cindex "black list (DNS)"
10522 When a DNS (black) list lookup succeeds, these variables are set to contain
10523 the following data from the lookup: the list's domain name, the key that was
10524 looked up, the contents of any associated TXT record, and the value from the
10525 main A record. See section &<<SECID204>>& for more details.
10526
10527 .vitem &$domain$&
10528 .vindex "&$domain$&"
10529 When an address is being routed, or delivered on its own, this variable
10530 contains the domain. Uppercase letters in the domain are converted into lower
10531 case for &$domain$&.
10532
10533 Global address rewriting happens when a message is received, so the value of
10534 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
10535 is set during user filtering, but not during system filtering, because a
10536 message may have many recipients and the system filter is called just once.
10537
10538 When more than one address is being delivered at once (for example, several
10539 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
10540 have the same domain. Transports can be restricted to handling only one domain
10541 at a time if the value of &$domain$& is required at transport time &-- this is
10542 the default for local transports. For further details of the environment in
10543 which local transports are run, see chapter &<<CHAPenvironment>>&.
10544
10545 .oindex "&%delay_warning_condition%&"
10546 At the end of a delivery, if all deferred addresses have the same domain, it is
10547 set in &$domain$& during the expansion of &%delay_warning_condition%&.
10548
10549 The &$domain$& variable is also used in some other circumstances:
10550
10551 .ilist
10552 When an ACL is running for a RCPT command, &$domain$& contains the domain of
10553 the recipient address. The domain of the &'sender'& address is in
10554 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
10555 normally set during the running of the MAIL ACL. However, if the sender address
10556 is verified with a callout during the MAIL ACL, the sender domain is placed in
10557 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
10558 the &(smtp)& transport.
10559
10560 .next
10561 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
10562 &$domain$& contains the domain portion of the address that is being rewritten;
10563 it can be used in the expansion of the replacement address, for example, to
10564 rewrite domains by file lookup.
10565
10566 .next
10567 With one important exception, whenever a domain list is being scanned,
10568 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
10569 a &%sender_domains%& condition in an ACL is being processed, the subject domain
10570 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
10571 that, in a RCPT ACL, the sender domain list can be dependent on the
10572 recipient domain (which is what is in &$domain$& at this time).
10573
10574 .next
10575 .cindex "ETRN" "value of &$domain$&"
10576 .oindex "&%smtp_etrn_command%&"
10577 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
10578 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
10579 .endlist
10580
10581
10582 .vitem &$domain_data$&
10583 .vindex "&$domain_data$&"
10584 When the &%domains%& option on a router matches a domain by
10585 means of a lookup, the data read by the lookup is available during the running
10586 of the router as &$domain_data$&. In addition, if the driver routes the
10587 address to a transport, the value is available in that transport. If the
10588 transport is handling multiple addresses, the value from the first address is
10589 used.
10590
10591 &$domain_data$& is also set when the &%domains%& condition in an ACL matches a
10592 domain by means of a lookup. The data read by the lookup is available during
10593 the rest of the ACL statement. In all other situations, this variable expands
10594 to nothing.
10595
10596 .vitem &$exim_gid$&
10597 .vindex "&$exim_gid$&"
10598 This variable contains the numerical value of the Exim group id.
10599
10600 .vitem &$exim_path$&
10601 .vindex "&$exim_path$&"
10602 This variable contains the path to the Exim binary.
10603
10604 .vitem &$exim_uid$&
10605 .vindex "&$exim_uid$&"
10606 This variable contains the numerical value of the Exim user id.
10607
10608 .vitem &$found_extension$&
10609 .vindex "&$found_extension$&"
10610 This variable is available when Exim is compiled with the
10611 content-scanning extension and the obsolete &%demime%& condition. For details,
10612 see section &<<SECTdemimecond>>&.
10613
10614 .vitem &$header_$&<&'name'&>
10615 This is not strictly an expansion variable. It is expansion syntax for
10616 inserting the message header line with the given name. Note that the name must
10617 be terminated by colon or white space, because it may contain a wide variety of
10618 characters. Note also that braces must &'not'& be used.
10619
10620 .vitem &$home$&
10621 .vindex "&$home$&"
10622 When the &%check_local_user%& option is set for a router, the user's home
10623 directory is placed in &$home$& when the check succeeds. In particular, this
10624 means it is set during the running of users' filter files. A router may also
10625 explicitly set a home directory for use by a transport; this can be overridden
10626 by a setting on the transport itself.
10627
10628 When running a filter test via the &%-bf%& option, &$home$& is set to the value
10629 of the environment variable HOME.
10630
10631 .vitem &$host$&
10632 .vindex "&$host$&"
10633 If a router assigns an address to a transport (any transport), and passes a
10634 list of hosts with the address, the value of &$host$& when the transport starts
10635 to run is the name of the first host on the list. Note that this applies both
10636 to local and remote transports.
10637
10638 .cindex "transport" "filter"
10639 .cindex "filter" "transport filter"
10640 For the &(smtp)& transport, if there is more than one host, the value of
10641 &$host$& changes as the transport works its way through the list. In
10642 particular, when the &(smtp)& transport is expanding its options for encryption
10643 using TLS, or for specifying a transport filter (see chapter
10644 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
10645 is connected.
10646
10647 When used in the client part of an authenticator configuration (see chapter
10648 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
10649 client is connected.
10650
10651
10652 .vitem &$host_address$&
10653 .vindex "&$host_address$&"
10654 This variable is set to the remote host's IP address whenever &$host$& is set
10655 for a remote connection. It is also set to the IP address that is being checked
10656 when the &%ignore_target_hosts%& option is being processed.
10657
10658 .vitem &$host_data$&
10659 .vindex "&$host_data$&"
10660 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
10661 result of the lookup is made available in the &$host_data$& variable. This
10662 allows you, for example, to do things like this:
10663 .code
10664 deny hosts = net-lsearch;/some/file
10665 message = $host_data
10666 .endd
10667 .vitem &$host_lookup_deferred$&
10668 .cindex "host name" "lookup, failure of"
10669 .vindex "&$host_lookup_deferred$&"
10670 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
10671 message comes from a remote host and there is an attempt to look up the host's
10672 name from its IP address, and the attempt is not successful, one of these
10673 variables is set to &"1"&.
10674
10675 .ilist
10676 If the lookup receives a definite negative response (for example, a DNS lookup
10677 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
10678
10679 .next
10680 If there is any kind of problem during the lookup, such that Exim cannot
10681 tell whether or not the host name is defined (for example, a timeout for a DNS
10682 lookup), &$host_lookup_deferred$& is set to &"1"&.
10683 .endlist ilist
10684
10685 Looking up a host's name from its IP address consists of more than just a
10686 single reverse lookup. Exim checks that a forward lookup of at least one of the
10687 names it receives from a reverse lookup yields the original IP address. If this
10688 is not the case, Exim does not accept the looked up name(s), and
10689 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
10690 IP address (for example, the existence of a PTR record in the DNS) is not
10691 sufficient on its own for the success of a host name lookup. If the reverse
10692 lookup succeeds, but there is a lookup problem such as a timeout when checking
10693 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
10694 &"1"&. See also &$sender_host_name$&.
10695
10696 .vitem &$host_lookup_failed$&
10697 .vindex "&$host_lookup_failed$&"
10698 See &$host_lookup_deferred$&.
10699
10700
10701 .vitem &$inode$&
10702 .vindex "&$inode$&"
10703 The only time this variable is set is while expanding the &%directory_file%&
10704 option in the &(appendfile)& transport. The variable contains the inode number
10705 of the temporary file which is about to be renamed. It can be used to construct
10706 a unique name for the file.
10707
10708 .vitem &$interface_address$&
10709 .vindex "&$interface_address$&"
10710 This is an obsolete name for &$received_ip_address$&.
10711
10712 .vitem &$interface_port$&
10713 .vindex "&$interface_port$&"
10714 This is an obsolete name for &$received_port$&.
10715
10716 .vitem &$item$&
10717 .vindex "&$item$&"
10718 This variable is used during the expansion of &*forall*& and &*forany*&
10719 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
10720 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
10721 empty.
10722
10723 .vitem &$ldap_dn$&
10724 .vindex "&$ldap_dn$&"
10725 This variable, which is available only when Exim is compiled with LDAP support,
10726 contains the DN from the last entry in the most recently successful LDAP
10727 lookup.
10728
10729 .vitem &$load_average$&
10730 .vindex "&$load_average$&"
10731 This variable contains the system load average, multiplied by 1000 so that it
10732 is an integer. For example, if the load average is 0.21, the value of the
10733 variable is 210. The value is recomputed every time the variable is referenced.
10734
10735 .vitem &$local_part$&
10736 .vindex "&$local_part$&"
10737 When an address is being routed, or delivered on its own, this
10738 variable contains the local part. When a number of addresses are being
10739 delivered together (for example, multiple RCPT commands in an SMTP
10740 session), &$local_part$& is not set.
10741
10742 Global address rewriting happens when a message is received, so the value of
10743 &$local_part$& during routing and delivery is the value after rewriting.
10744 &$local_part$& is set during user filtering, but not during system filtering,
10745 because a message may have many recipients and the system filter is called just
10746 once.
10747
10748 .vindex "&$local_part_prefix$&"
10749 .vindex "&$local_part_suffix$&"
10750 If a local part prefix or suffix has been recognized, it is not included in the
10751 value of &$local_part$& during routing and subsequent delivery. The values of
10752 any prefix or suffix are in &$local_part_prefix$& and
10753 &$local_part_suffix$&, respectively.
10754
10755 When a message is being delivered to a file, pipe, or autoreply transport as a
10756 result of aliasing or forwarding, &$local_part$& is set to the local part of
10757 the parent address, not to the file name or command (see &$address_file$& and
10758 &$address_pipe$&).
10759
10760 When an ACL is running for a RCPT command, &$local_part$& contains the
10761 local part of the recipient address.
10762
10763 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
10764 &$local_part$& contains the local part of the address that is being rewritten;
10765 it can be used in the expansion of the replacement address, for example.
10766
10767 In all cases, all quoting is removed from the local part. For example, for both
10768 the addresses
10769 .code
10770 "abc:xyz"@test.example
10771 abc\:xyz@test.example
10772 .endd
10773 the value of &$local_part$& is
10774 .code
10775 abc:xyz
10776 .endd
10777 If you use &$local_part$& to create another address, you should always wrap it
10778 inside a quoting operator. For example, in a &(redirect)& router you could
10779 have:
10780 .code
10781 data = ${quote_local_part:$local_part}@new.domain.example
10782 .endd
10783 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
10784 to process local parts in a case-dependent manner in a router, you can set the
10785 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
10786
10787 .vitem &$local_part_data$&
10788 .vindex "&$local_part_data$&"
10789 When the &%local_parts%& option on a router matches a local part by means of a
10790 lookup, the data read by the lookup is available during the running of the
10791 router as &$local_part_data$&. In addition, if the driver routes the address
10792 to a transport, the value is available in that transport. If the transport is
10793 handling multiple addresses, the value from the first address is used.
10794
10795 &$local_part_data$& is also set when the &%local_parts%& condition in an ACL
10796 matches a local part by means of a lookup. The data read by the lookup is
10797 available during the rest of the ACL statement. In all other situations, this
10798 variable expands to nothing.
10799
10800 .vitem &$local_part_prefix$&
10801 .vindex "&$local_part_prefix$&"
10802 When an address is being routed or delivered, and a
10803 specific prefix for the local part was recognized, it is available in this
10804 variable, having been removed from &$local_part$&.
10805
10806 .vitem &$local_part_suffix$&
10807 .vindex "&$local_part_suffix$&"
10808 When an address is being routed or delivered, and a
10809 specific suffix for the local part was recognized, it is available in this
10810 variable, having been removed from &$local_part$&.
10811
10812 .vitem &$local_scan_data$&
10813 .vindex "&$local_scan_data$&"
10814 This variable contains the text returned by the &[local_scan()]& function when
10815 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
10816
10817 .vitem &$local_user_gid$&
10818 .vindex "&$local_user_gid$&"
10819 See &$local_user_uid$&.
10820
10821 .vitem &$local_user_uid$&
10822 .vindex "&$local_user_uid$&"
10823 This variable and &$local_user_gid$& are set to the uid and gid after the
10824 &%check_local_user%& router precondition succeeds. This means that their values
10825 are available for the remaining preconditions (&%senders%&, &%require_files%&,
10826 and &%condition%&), for the &%address_data%& expansion, and for any
10827 router-specific expansions. At all other times, the values in these variables
10828 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
10829
10830 .vitem &$localhost_number$&
10831 .vindex "&$localhost_number$&"
10832 This contains the expanded value of the
10833 &%localhost_number%& option. The expansion happens after the main options have
10834 been read.
10835
10836 .vitem &$log_inodes$&
10837 .vindex "&$log_inodes$&"
10838 The number of free inodes in the disk partition where Exim's
10839 log files are being written. The value is recalculated whenever the variable is
10840 referenced. If the relevant file system does not have the concept of inodes,
10841 the value of is -1. See also the &%check_log_inodes%& option.
10842
10843 .vitem &$log_space$&
10844 .vindex "&$log_space$&"
10845 The amount of free space (as a number of kilobytes) in the disk
10846 partition where Exim's log files are being written. The value is recalculated
10847 whenever the variable is referenced. If the operating system does not have the
10848 ability to find the amount of free space (only true for experimental systems),
10849 the space value is -1. See also the &%check_log_space%& option.
10850
10851
10852 .vitem &$mailstore_basename$&
10853 .vindex "&$mailstore_basename$&"
10854 This variable is set only when doing deliveries in &"mailstore"& format in the
10855 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
10856 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
10857 contains the basename of the files that are being written, that is, the name
10858 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
10859 variable is empty.
10860
10861 .vitem &$malware_name$&
10862 .vindex "&$malware_name$&"
10863 This variable is available when Exim is compiled with the
10864 content-scanning extension. It is set to the name of the virus that was found
10865 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
10866
10867 .vitem &$max_received_linelength$&
10868 .vindex "&$max_received_linelength$&"
10869 .cindex "maximum" "line length"
10870 .cindex "line length" "maximum"
10871 This variable contains the number of bytes in the longest line that was
10872 received as part of the message, not counting the line termination
10873 character(s).
10874
10875 .vitem &$message_age$&
10876 .cindex "message" "age of"
10877 .vindex "&$message_age$&"
10878 This variable is set at the start of a delivery attempt to contain the number
10879 of seconds since the message was received. It does not change during a single
10880 delivery attempt.
10881
10882 .vitem &$message_body$&
10883 .cindex "body of message" "expansion variable"
10884 .cindex "message body" "in expansion"
10885 .cindex "binary zero" "in message body"
10886 .vindex "&$message_body$&"
10887 .oindex "&%message_body_visible%&"
10888 This variable contains the initial portion of a message's body while it is
10889 being delivered, and is intended mainly for use in filter files. The maximum
10890 number of characters of the body that are put into the variable is set by the
10891 &%message_body_visible%& configuration option; the default is 500.
10892
10893 .oindex "&%message_body_newlines%&"
10894 By default, newlines are converted into spaces in &$message_body$&, to make it
10895 easier to search for phrases that might be split over a line break. However,
10896 this can be disabled by setting &%message_body_newlines%& to be true. Binary
10897 zeros are always converted into spaces.
10898
10899 .vitem &$message_body_end$&
10900 .cindex "body of message" "expansion variable"
10901 .cindex "message body" "in expansion"
10902 .vindex "&$message_body_end$&"
10903 This variable contains the final portion of a message's
10904 body while it is being delivered. The format and maximum size are as for
10905 &$message_body$&.
10906
10907 .vitem &$message_body_size$&
10908 .cindex "body of message" "size"
10909 .cindex "message body" "size"
10910 .vindex "&$message_body_size$&"
10911 When a message is being delivered, this variable contains the size of the body
10912 in bytes. The count starts from the character after the blank line that
10913 separates the body from the header. Newlines are included in the count. See
10914 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
10915
10916 .vitem &$message_exim_id$&
10917 .vindex "&$message_exim_id$&"
10918 When a message is being received or delivered, this variable contains the
10919 unique message id that is generated and used by Exim to identify the message.
10920 An id is not created for a message until after its header has been successfully
10921 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
10922 line; it is the local id that Exim assigns to the message, for example:
10923 &`1BXTIK-0001yO-VA`&.
10924
10925 .vitem &$message_headers$&
10926 .vindex &$message_headers$&
10927 This variable contains a concatenation of all the header lines when a message
10928 is being processed, except for lines added by routers or transports. The header
10929 lines are separated by newline characters. Their contents are decoded in the
10930 same way as a header line that is inserted by &%bheader%&.
10931
10932 .vitem &$message_headers_raw$&
10933 .vindex &$message_headers_raw$&
10934 This variable is like &$message_headers$& except that no processing of the
10935 contents of header lines is done.
10936
10937 .vitem &$message_id$&
10938 This is an old name for &$message_exim_id$&, which is now deprecated.
10939
10940 .vitem &$message_linecount$&
10941 .vindex "&$message_linecount$&"
10942 This variable contains the total number of lines in the header and body of the
10943 message. Compare &$body_linecount$&, which is the count for the body only.
10944 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
10945 number of lines received. Before delivery happens (that is, before filters,
10946 routers, and transports run) the count is increased to include the
10947 &'Received:'& header line that Exim standardly adds, and also any other header
10948 lines that are added by ACLs. The blank line that separates the message header
10949 from the body is not counted. Here is an example of the use of this variable in
10950 a DATA ACL:
10951 .code
10952 deny message = Too many lines in message header
10953 condition = \
10954 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
10955 .endd
10956 In the MAIL and RCPT ACLs, the value is zero because at that stage the
10957 message has not yet been received.
10958
10959 .vitem &$message_size$&
10960 .cindex "size" "of message"
10961 .cindex "message" "size"
10962 .vindex "&$message_size$&"
10963 When a message is being processed, this variable contains its size in bytes. In
10964 most cases, the size includes those headers that were received with the
10965 message, but not those (such as &'Envelope-to:'&) that are added to individual
10966 deliveries as they are written. However, there is one special case: during the
10967 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
10968 doing a delivery in maildir format, the value of &$message_size$& is the
10969 precise size of the file that has been written. See also
10970 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
10971
10972 .cindex "RCPT" "value of &$message_size$&"
10973 While running an ACL at the time of an SMTP RCPT command, &$message_size$&
10974 contains the size supplied on the MAIL command, or -1 if no size was given. The
10975 value may not, of course, be truthful.
10976
10977 .vitem &$mime_$&&'xxx'&
10978 A number of variables whose names start with &$mime$& are
10979 available when Exim is compiled with the content-scanning extension. For
10980 details, see section &<<SECTscanmimepart>>&.
10981
10982 .vitem "&$n0$& &-- &$n9$&"
10983 These variables are counters that can be incremented by means
10984 of the &%add%& command in filter files.
10985
10986 .vitem &$original_domain$&
10987 .vindex "&$domain$&"
10988 .vindex "&$original_domain$&"
10989 When a top-level address is being processed for delivery, this contains the
10990 same value as &$domain$&. However, if a &"child"& address (for example,
10991 generated by an alias, forward, or filter file) is being processed, this
10992 variable contains the domain of the original address (lower cased). This
10993 differs from &$parent_domain$& only when there is more than one level of
10994 aliasing or forwarding. When more than one address is being delivered in a
10995 single transport run, &$original_domain$& is not set.
10996
10997 If a new address is created by means of a &%deliver%& command in a system
10998 filter, it is set up with an artificial &"parent"& address. This has the local
10999 part &'system-filter'& and the default qualify domain.
11000
11001 .vitem &$original_local_part$&
11002 .vindex "&$local_part$&"
11003 .vindex "&$original_local_part$&"
11004 When a top-level address is being processed for delivery, this contains the
11005 same value as &$local_part$&, unless a prefix or suffix was removed from the
11006 local part, because &$original_local_part$& always contains the full local
11007 part. When a &"child"& address (for example, generated by an alias, forward, or
11008 filter file) is being processed, this variable contains the full local part of
11009 the original address.
11010
11011 If the router that did the redirection processed the local part
11012 case-insensitively, the value in &$original_local_part$& is in lower case.
11013 This variable differs from &$parent_local_part$& only when there is more than
11014 one level of aliasing or forwarding. When more than one address is being
11015 delivered in a single transport run, &$original_local_part$& is not set.
11016
11017 If a new address is created by means of a &%deliver%& command in a system
11018 filter, it is set up with an artificial &"parent"& address. This has the local
11019 part &'system-filter'& and the default qualify domain.
11020
11021 .vitem &$originator_gid$&
11022 .cindex "gid (group id)" "of originating user"
11023 .cindex "sender" "gid"
11024 .vindex "&$caller_gid$&"
11025 .vindex "&$originator_gid$&"
11026 This variable contains the value of &$caller_gid$& that was set when the
11027 message was received. For messages received via the command line, this is the
11028 gid of the sending user. For messages received by SMTP over TCP/IP, this is
11029 normally the gid of the Exim user.
11030
11031 .vitem &$originator_uid$&
11032 .cindex "uid (user id)" "of originating user"
11033 .cindex "sender" "uid"
11034 .vindex "&$caller_uid$&"
11035 .vindex "&$originaltor_uid$&"
11036 The value of &$caller_uid$& that was set when the message was received. For
11037 messages received via the command line, this is the uid of the sending user.
11038 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
11039 user.
11040
11041 .vitem &$parent_domain$&
11042 .vindex "&$parent_domain$&"
11043 This variable is similar to &$original_domain$& (see
11044 above), except that it refers to the immediately preceding parent address.
11045
11046 .vitem &$parent_local_part$&
11047 .vindex "&$parent_local_part$&"
11048 This variable is similar to &$original_local_part$&
11049 (see above), except that it refers to the immediately preceding parent address.
11050
11051 .vitem &$pid$&
11052 .cindex "pid (process id)" "of current process"
11053 .vindex "&$pid$&"
11054 This variable contains the current process id.
11055
11056 .vitem &$pipe_addresses$&
11057 .cindex "filter" "transport filter"
11058 .cindex "transport" "filter"
11059 .vindex "&$pipe_addresses$&"
11060 This is not an expansion variable, but is mentioned here because the string
11061 &`$pipe_addresses`& is handled specially in the command specification for the
11062 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
11063 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
11064 It cannot be used in general expansion strings, and provokes an &"unknown
11065 variable"& error if encountered.
11066
11067 .vitem &$primary_hostname$&
11068 .vindex "&$primary_hostname$&"
11069 This variable contains the value set by &%primary_hostname%& in the
11070 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
11071 a single-component name, Exim calls &[gethostbyname()]& (or
11072 &[getipnodebyname()]& where available) in an attempt to acquire a fully
11073 qualified host name. See also &$smtp_active_hostname$&.
11074
11075
11076 .vitem &$prvscheck_address$&
11077 This variable is used in conjunction with the &%prvscheck%& expansion item,
11078 which is described in sections &<<SECTexpansionitems>>& and
11079 &<<SECTverifyPRVS>>&.
11080
11081 .vitem &$prvscheck_keynum$&
11082 This variable is used in conjunction with the &%prvscheck%& expansion item,
11083 which is described in sections &<<SECTexpansionitems>>& and
11084 &<<SECTverifyPRVS>>&.
11085
11086 .vitem &$prvscheck_result$&
11087 This variable is used in conjunction with the &%prvscheck%& expansion item,
11088 which is described in sections &<<SECTexpansionitems>>& and
11089 &<<SECTverifyPRVS>>&.
11090
11091 .vitem &$qualify_domain$&
11092 .vindex "&$qualify_domain$&"
11093 The value set for the &%qualify_domain%& option in the configuration file.
11094
11095 .vitem &$qualify_recipient$&
11096 .vindex "&$qualify_recipient$&"
11097 The value set for the &%qualify_recipient%& option in the configuration file,
11098 or if not set, the value of &$qualify_domain$&.
11099
11100 .vitem &$rcpt_count$&
11101 .vindex "&$rcpt_count$&"
11102 When a message is being received by SMTP, this variable contains the number of
11103 RCPT commands received for the current message. If this variable is used in a
11104 RCPT ACL, its value includes the current command.
11105
11106 .vitem &$rcpt_defer_count$&
11107 .vindex "&$rcpt_defer_count$&"
11108 .cindex "4&'xx'& responses" "count of"
11109 When a message is being received by SMTP, this variable contains the number of
11110 RCPT commands in the current message that have previously been rejected with a
11111 temporary (4&'xx'&) response.
11112
11113 .vitem &$rcpt_fail_count$&
11114 .vindex "&$rcpt_fail_count$&"
11115 When a message is being received by SMTP, this variable contains the number of
11116 RCPT commands in the current message that have previously been rejected with a
11117 permanent (5&'xx'&) response.
11118
11119 .vitem &$received_count$&
11120 .vindex "&$received_count$&"
11121 This variable contains the number of &'Received:'& header lines in the message,
11122 including the one added by Exim (so its value is always greater than zero). It
11123 is available in the DATA ACL, the non-SMTP ACL, and while routing and
11124 delivering.
11125
11126 .vitem &$received_for$&
11127 .vindex "&$received_for$&"
11128 If there is only a single recipient address in an incoming message, this
11129 variable contains that address when the &'Received:'& header line is being
11130 built. The value is copied after recipient rewriting has happened, but before
11131 the &[local_scan()]& function is run.
11132
11133 .vitem &$received_ip_address$&
11134 .vindex "&$received_ip_address$&"
11135 As soon as an Exim server starts processing an incoming TCP/IP connection, this
11136 variable is set to the address of the local IP interface, and &$received_port$&
11137 is set to the local port number. (The remote IP address and port are in
11138 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
11139 the port value is -1 unless it has been set using the &%-oMi%& command line
11140 option.
11141
11142 As well as being useful in ACLs (including the &"connect"& ACL), these variable
11143 could be used, for example, to make the file name for a TLS certificate depend
11144 on which interface and/or port is being used for the incoming connection. The
11145 values of &$received_ip_address$& and &$received_port$& are saved with any
11146 messages that are received, thus making these variables available at delivery
11147 time.
11148
11149 &*Note:*& There are no equivalent variables for outgoing connections, because
11150 the values are unknown (unless they are explicitly set by options of the
11151 &(smtp)& transport).
11152
11153 .vitem &$received_port$&
11154 .vindex "&$received_port$&"
11155 See &$received_ip_address$&.
11156
11157 .vitem &$received_protocol$&
11158 .vindex "&$received_protocol$&"
11159 When a message is being processed, this variable contains the name of the
11160 protocol by which it was received. Most of the names used by Exim are defined
11161 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
11162 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
11163 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
11164 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
11165 connection and the client was successfully authenticated.
11166
11167 Exim uses the protocol name &"smtps"& for the case when encryption is
11168 automatically set up on connection without the use of STARTTLS (see
11169 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
11170 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
11171 where the client initially uses EHLO, sets up an encrypted connection using
11172 STARTTLS, and then uses HELO afterwards.
11173
11174 The &%-oMr%& option provides a way of specifying a custom protocol name for
11175 messages that are injected locally by trusted callers. This is commonly used to
11176 identify messages that are being re-injected after some kind of scanning.
11177
11178 .vitem &$received_time$&
11179 .vindex "&$received_time$&"
11180 This variable contains the date and time when the current message was received,
11181 as a number of seconds since the start of the Unix epoch.
11182
11183 .vitem &$recipient_data$&
11184 .vindex "&$recipient_data$&"
11185 This variable is set after an indexing lookup success in an ACL &%recipients%&
11186 condition. It contains the data from the lookup, and the value remains set
11187 until the next &%recipients%& test. Thus, you can do things like this:
11188 .display
11189 &`require recipients = cdb*@;/some/file`&
11190 &`deny `&&'some further test involving'& &`$recipient_data`&
11191 .endd
11192 &*Warning*&: This variable is set only when a lookup is used as an indexing
11193 method in the address list, using the semicolon syntax as in the example above.
11194 The variable is not set for a lookup that is used as part of the string
11195 expansion that all such lists undergo before being interpreted.
11196
11197 .vitem &$recipient_verify_failure$&
11198 .vindex "&$recipient_verify_failure$&"
11199 In an ACL, when a recipient verification fails, this variable contains
11200 information about the failure. It is set to one of the following words:
11201
11202 .ilist
11203 &"qualify"&: The address was unqualified (no domain), and the message
11204 was neither local nor came from an exempted host.
11205
11206 .next
11207 &"route"&: Routing failed.
11208
11209 .next
11210 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
11211 or before the MAIL command (that is, on initial connection, HELO, or
11212 MAIL).
11213
11214 .next
11215 &"recipient"&: The RCPT command in a callout was rejected.
11216 .next
11217
11218 &"postmaster"&: The postmaster check in a callout was rejected.
11219 .endlist
11220
11221 The main use of this variable is expected to be to distinguish between
11222 rejections of MAIL and rejections of RCPT.
11223
11224 .vitem &$recipients$&
11225 .vindex "&$recipients$&"
11226 This variable contains a list of envelope recipients for a message. A comma and
11227 a space separate the addresses in the replacement text. However, the variable
11228 is not generally available, to prevent exposure of Bcc recipients in
11229 unprivileged users' filter files. You can use &$recipients$& only in these
11230 cases:
11231
11232 .olist
11233 In a system filter file.
11234 .next
11235 In the ACLs associated with the DATA command and with non-SMTP messages, that
11236 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
11237 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
11238 &%acl_not_smtp_mime%&.
11239 .next
11240 From within a &[local_scan()]& function.
11241 .endlist
11242
11243
11244 .vitem &$recipients_count$&
11245 .vindex "&$recipients_count$&"
11246 When a message is being processed, this variable contains the number of
11247 envelope recipients that came with the message. Duplicates are not excluded
11248 from the count. While a message is being received over SMTP, the number
11249 increases for each accepted recipient. It can be referenced in an ACL.
11250
11251
11252 .vitem &$regex_match_string$&
11253 .vindex "&$regex_match_string$&"
11254 This variable is set to contain the matching regular expression after a
11255 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
11256
11257
11258 .vitem &$reply_address$&
11259 .vindex "&$reply_address$&"
11260 When a message is being processed, this variable contains the contents of the
11261 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
11262 contents of the &'From:'& header line. Apart from the removal of leading
11263 white space, the value is not processed in any way. In particular, no RFC 2047
11264 decoding or character code translation takes place.
11265
11266 .vitem &$return_path$&
11267 .vindex "&$return_path$&"
11268 When a message is being delivered, this variable contains the return path &--
11269 the sender field that will be sent as part of the envelope. It is not enclosed
11270 in <> characters. At the start of routing an address, &$return_path$& has the
11271 same value as &$sender_address$&, but if, for example, an incoming message to a
11272 mailing list has been expanded by a router which specifies a different address
11273 for bounce messages, &$return_path$& subsequently contains the new bounce
11274 address, whereas &$sender_address$& always contains the original sender address
11275 that was received with the message. In other words, &$sender_address$& contains
11276 the incoming envelope sender, and &$return_path$& contains the outgoing
11277 envelope sender.
11278
11279 .vitem &$return_size_limit$&
11280 .vindex "&$return_size_limit$&"
11281 This is an obsolete name for &$bounce_return_size_limit$&.
11282
11283 .vitem &$runrc$&
11284 .cindex "return code" "from &%run%& expansion"
11285 .vindex "&$runrc$&"
11286 This variable contains the return code from a command that is run by the
11287 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
11288 assume the order in which option values are expanded, except for those
11289 preconditions whose order of testing is documented. Therefore, you cannot
11290 reliably expect to set &$runrc$& by the expansion of one option, and use it in
11291 another.
11292
11293 .vitem &$self_hostname$&
11294 .oindex "&%self%&" "value of host name"
11295 .vindex "&$self_hostname$&"
11296 When an address is routed to a supposedly remote host that turns out to be the
11297 local host, what happens is controlled by the &%self%& generic router option.
11298 One of its values causes the address to be passed to another router. When this
11299 happens, &$self_hostname$& is set to the name of the local host that the
11300 original router encountered. In other circumstances its contents are null.
11301
11302 .vitem &$sender_address$&
11303 .vindex "&$sender_address$&"
11304 When a message is being processed, this variable contains the sender's address
11305 that was received in the message's envelope. The case of letters in the address
11306 is retained, in both the local part and the domain. For bounce messages, the
11307 value of this variable is the empty string. See also &$return_path$&.
11308
11309 .vitem &$sender_address_data$&
11310 .vindex "&$address_data$&"
11311 .vindex "&$sender_address_data$&"
11312 If &$address_data$& is set when the routers are called from an ACL to verify a
11313 sender address, the final value is preserved in &$sender_address_data$&, to
11314 distinguish it from data from a recipient address. The value does not persist
11315 after the end of the current ACL statement. If you want to preserve it for
11316 longer, you can save it in an ACL variable.
11317
11318 .vitem &$sender_address_domain$&
11319 .vindex "&$sender_address_domain$&"
11320 The domain portion of &$sender_address$&.
11321
11322 .vitem &$sender_address_local_part$&
11323 .vindex "&$sender_address_local_part$&"
11324 The local part portion of &$sender_address$&.
11325
11326 .vitem &$sender_data$&
11327 .vindex "&$sender_data$&"
11328 This variable is set after a lookup success in an ACL &%senders%& condition or
11329 in a router &%senders%& option. It contains the data from the lookup, and the
11330 value remains set until the next &%senders%& test. Thus, you can do things like
11331 this:
11332 .display
11333 &`require senders = cdb*@;/some/file`&
11334 &`deny `&&'some further test involving'& &`$sender_data`&
11335 .endd
11336 &*Warning*&: This variable is set only when a lookup is used as an indexing
11337 method in the address list, using the semicolon syntax as in the example above.
11338 The variable is not set for a lookup that is used as part of the string
11339 expansion that all such lists undergo before being interpreted.
11340
11341 .vitem &$sender_fullhost$&
11342 .vindex "&$sender_fullhost$&"
11343 When a message is received from a remote host, this variable contains the host
11344 name and IP address in a single string. It ends with the IP address in square
11345 brackets, followed by a colon and a port number if the logging of ports is
11346 enabled. The format of the rest of the string depends on whether the host
11347 issued a HELO or EHLO SMTP command, and whether the host name was verified by
11348 looking up its IP address. (Looking up the IP address can be forced by the
11349 &%host_lookup%& option, independent of verification.) A plain host name at the
11350 start of the string is a verified host name; if this is not present,
11351 verification either failed or was not requested. A host name in parentheses is
11352 the argument of a HELO or EHLO command. This is omitted if it is identical to
11353 the verified host name or to the host's IP address in square brackets.
11354
11355 .vitem &$sender_helo_name$&
11356 .vindex "&$sender_helo_name$&"
11357 When a message is received from a remote host that has issued a HELO or EHLO
11358 command, the argument of that command is placed in this variable. It is also
11359 set if HELO or EHLO is used when a message is received using SMTP locally via
11360 the &%-bs%& or &%-bS%& options.
11361
11362 .vitem &$sender_host_address$&
11363 .vindex "&$sender_host_address$&"
11364 When a message is received from a remote host, this variable contains that
11365 host's IP address. For locally submitted messages, it is empty.
11366
11367 .vitem &$sender_host_authenticated$&
11368 .vindex "&$sender_host_authenticated$&"
11369 This variable contains the name (not the public name) of the authenticator
11370 driver that successfully authenticated the client from which the message was
11371 received. It is empty if there was no successful authentication. See also
11372 &$authenticated_id$&.
11373
11374 .vitem &$sender_host_name$&
11375 .vindex "&$sender_host_name$&"
11376 When a message is received from a remote host, this variable contains the
11377 host's name as obtained by looking up its IP address. For messages received by
11378 other means, this variable is empty.
11379
11380 .vindex "&$host_lookup_failed$&"
11381 If the host name has not previously been looked up, a reference to
11382 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
11383 A looked up name is accepted only if it leads back to the original IP address
11384 via a forward lookup. If either the reverse or the forward lookup fails to find
11385 any data, or if the forward lookup does not yield the original IP address,
11386 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
11387
11388 .vindex "&$host_lookup_deferred$&"
11389 However, if either of the lookups cannot be completed (for example, there is a
11390 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
11391 &$host_lookup_failed$& remains set to &"0"&.
11392
11393 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
11394 host name again if there is a subsequent reference to &$sender_host_name$&
11395 in the same Exim process, but it does try again if &$host_lookup_deferred$&
11396 is set to &"1"&.
11397
11398 Exim does not automatically look up every calling host's name. If you want
11399 maximum efficiency, you should arrange your configuration so that it avoids
11400 these lookups altogether. The lookup happens only if one or more of the
11401 following are true:
11402
11403 .ilist
11404 A string containing &$sender_host_name$& is expanded.
11405 .next
11406 The calling host matches the list in &%host_lookup%&. In the default
11407 configuration, this option is set to *, so it must be changed if lookups are
11408 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
11409 .next
11410 Exim needs the host name in order to test an item in a host list. The items
11411 that require this are described in sections &<<SECThoslispatnam>>& and
11412 &<<SECThoslispatnamsk>>&.
11413 .next
11414 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
11415 In this case, the host name is required to compare with the name quoted in any
11416 EHLO or HELO commands that the client issues.
11417 .next
11418 The remote host issues a EHLO or HELO command that quotes one of the
11419 domains in &%helo_lookup_domains%&. The default value of this option is
11420 . ==== As this is a nested list, any displays it contains must be indented
11421 . ==== as otherwise they are too far to the left.
11422 .code
11423 helo_lookup_domains = @ : @[]
11424 .endd
11425 which causes a lookup if a remote host (incorrectly) gives the server's name or
11426 IP address in an EHLO or HELO command.
11427 .endlist
11428
11429
11430 .vitem &$sender_host_port$&
11431 .vindex "&$sender_host_port$&"
11432 When a message is received from a remote host, this variable contains the port
11433 number that was used on the remote host.
11434
11435 .vitem &$sender_ident$&
11436 .vindex "&$sender_ident$&"
11437 When a message is received from a remote host, this variable contains the
11438 identification received in response to an RFC 1413 request. When a message has
11439 been received locally, this variable contains the login name of the user that
11440 called Exim.
11441
11442 .vitem &$sender_rate_$&&'xxx'&
11443 A number of variables whose names begin &$sender_rate_$& are set as part of the
11444 &%ratelimit%& ACL condition. Details are given in section
11445 &<<SECTratelimiting>>&.
11446
11447 .vitem &$sender_rcvhost$&
11448 .cindex "DNS" "reverse lookup"
11449 .cindex "reverse DNS lookup"
11450 .vindex "&$sender_rcvhost$&"
11451 This is provided specifically for use in &'Received:'& headers. It starts with
11452 either the verified host name (as obtained from a reverse DNS lookup) or, if
11453 there is no verified host name, the IP address in square brackets. After that
11454 there may be text in parentheses. When the first item is a verified host name,
11455 the first thing in the parentheses is the IP address in square brackets,
11456 followed by a colon and a port number if port logging is enabled. When the
11457 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
11458 the parentheses.
11459
11460 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
11461 was used and its argument was not identical to the real host name or IP
11462 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
11463 all three items are present in the parentheses, a newline and tab are inserted
11464 into the string, to improve the formatting of the &'Received:'& header.
11465
11466 .vitem &$sender_verify_failure$&
11467 .vindex "&$sender_verify_failure$&"
11468 In an ACL, when a sender verification fails, this variable contains information
11469 about the failure. The details are the same as for
11470 &$recipient_verify_failure$&.
11471
11472 .vitem &$sending_ip_address$&
11473 .vindex "&$sending_ip_address$&"
11474 This variable is set whenever an outgoing SMTP connection to another host has
11475 been set up. It contains the IP address of the local interface that is being
11476 used. This is useful if a host that has more than one IP address wants to take
11477 on different personalities depending on which one is being used. For incoming
11478 connections, see &$received_ip_address$&.
11479
11480 .vitem &$sending_port$&
11481 .vindex "&$sending_port$&"
11482 This variable is set whenever an outgoing SMTP connection to another host has
11483 been set up. It contains the local port that is being used. For incoming
11484 connections, see &$received_port$&.
11485
11486 .vitem &$smtp_active_hostname$&
11487 .vindex "&$smtp_active_hostname$&"
11488 During an incoming SMTP session, this variable contains the value of the active
11489 host name, as specified by the &%smtp_active_hostname%& option. The value of
11490 &$smtp_active_hostname$& is saved with any message that is received, so its
11491 value can be consulted during routing and delivery.
11492
11493 .vitem &$smtp_command$&
11494 .vindex "&$smtp_command$&"
11495 During the processing of an incoming SMTP command, this variable contains the
11496 entire command. This makes it possible to distinguish between HELO and EHLO in
11497 the HELO ACL, and also to distinguish between commands such as these:
11498 .code
11499 MAIL FROM:<>
11500 MAIL FROM: <>
11501 .endd
11502 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
11503 command, the address in &$smtp_command$& is the original address before any
11504 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
11505 the address after SMTP-time rewriting.
11506
11507 .vitem &$smtp_command_argument$&
11508 .cindex "SMTP" "command, argument for"
11509 .vindex "&$smtp_command_argument$&"
11510 While an ACL is running to check an SMTP command, this variable contains the
11511 argument, that is, the text that follows the command name, with leading white
11512 space removed. Following the introduction of &$smtp_command$&, this variable is
11513 somewhat redundant, but is retained for backwards compatibility.
11514
11515 .vitem &$smtp_count_at_connection_start$&
11516 .vindex "&$smtp_count_at_connection_start$&"
11517 This variable is set greater than zero only in processes spawned by the Exim
11518 daemon for handling incoming SMTP connections. The name is deliberately long,
11519 in order to emphasize what the contents are. When the daemon accepts a new
11520 connection, it increments this variable. A copy of the variable is passed to
11521 the child process that handles the connection, but its value is fixed, and
11522 never changes. It is only an approximation of how many incoming connections
11523 there actually are, because many other connections may come and go while a
11524 single connection is being processed. When a child process terminates, the
11525 daemon decrements its copy of the variable.
11526
11527 .vitem "&$sn0$& &-- &$sn9$&"
11528 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
11529 that were current at the end of the system filter file. This allows a system
11530 filter file to set values that can be tested in users' filter files. For
11531 example, a system filter could set a value indicating how likely it is that a
11532 message is junk mail.
11533
11534 .vitem &$spam_$&&'xxx'&
11535 A number of variables whose names start with &$spam$& are available when Exim
11536 is compiled with the content-scanning extension. For details, see section
11537 &<<SECTscanspamass>>&.
11538
11539
11540 .vitem &$spool_directory$&
11541 .vindex "&$spool_directory$&"
11542 The name of Exim's spool directory.
11543
11544 .vitem &$spool_inodes$&
11545 .vindex "&$spool_inodes$&"
11546 The number of free inodes in the disk partition where Exim's spool files are
11547 being written. The value is recalculated whenever the variable is referenced.
11548 If the relevant file system does not have the concept of inodes, the value of
11549 is -1. See also the &%check_spool_inodes%& option.
11550
11551 .vitem &$spool_space$&
11552 .vindex "&$spool_space$&"
11553 The amount of free space (as a number of kilobytes) in the disk partition where
11554 Exim's spool files are being written. The value is recalculated whenever the
11555 variable is referenced. If the operating system does not have the ability to
11556 find the amount of free space (only true for experimental systems), the space
11557 value is -1. For example, to check in an ACL that there is at least 50
11558 megabytes free on the spool, you could write:
11559 .code
11560 condition = ${if > {$spool_space}{50000}}
11561 .endd
11562 See also the &%check_spool_space%& option.
11563
11564
11565 .vitem &$thisaddress$&
11566 .vindex "&$thisaddress$&"
11567 This variable is set only during the processing of the &%foranyaddress%&
11568 command in a filter file. Its use is explained in the description of that
11569 command, which can be found in the separate document entitled &'Exim's
11570 interfaces to mail filtering'&.
11571
11572 .vitem &$tls_certificate_verified$&
11573 .vindex "&$tls_certificate_verified$&"
11574 This variable is set to &"1"& if a TLS certificate was verified when the
11575 message was received, and &"0"& otherwise.
11576
11577 .vitem &$tls_cipher$&
11578 .vindex "&$tls_cipher$&"
11579 When a message is received from a remote host over an encrypted SMTP
11580 connection, this variable is set to the cipher suite that was negotiated, for
11581 example DES-CBC3-SHA. In other circumstances, in particular, for message
11582 received over unencrypted connections, the variable is empty. Testing
11583 &$tls_cipher$& for emptiness is one way of distinguishing between encrypted and
11584 non-encrypted connections during ACL processing.
11585
11586 The &$tls_cipher$& variable retains its value during message delivery, except
11587 when an outward SMTP delivery takes place via the &(smtp)& transport. In this
11588 case, &$tls_cipher$& is cleared before any outgoing SMTP connection is made,
11589 and then set to the outgoing cipher suite if one is negotiated. See chapter
11590 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
11591 details of the &(smtp)& transport.
11592
11593 .vitem &$tls_peerdn$&
11594 .vindex "&$tls_peerdn$&"
11595 When a message is received from a remote host over an encrypted SMTP
11596 connection, and Exim is configured to request a certificate from the client,
11597 the value of the Distinguished Name of the certificate is made available in the
11598 &$tls_peerdn$& during subsequent processing. Like &$tls_cipher$&, the
11599 value is retained during message delivery, except during outbound SMTP
11600 deliveries.
11601
11602 .vitem &$tod_bsdinbox$&
11603 .vindex "&$tod_bsdinbox$&"
11604 The time of day and the date, in the format required for BSD-style mailbox
11605 files, for example: Thu Oct 17 17:14:09 1995.
11606
11607 .vitem &$tod_epoch$&
11608 .vindex "&$tod_epoch$&"
11609 The time and date as a number of seconds since the start of the Unix epoch.
11610
11611 .vitem &$tod_full$&
11612 .vindex "&$tod_full$&"
11613 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
11614 +0100. The timezone is always given as a numerical offset from UTC, with
11615 positive values used for timezones that are ahead (east) of UTC, and negative
11616 values for those that are behind (west).
11617
11618 .vitem &$tod_log$&
11619 .vindex "&$tod_log$&"
11620 The time and date in the format used for writing Exim's log files, for example:
11621 1995-10-12 15:32:29, but without a timezone.
11622
11623 .vitem &$tod_logfile$&
11624 .vindex "&$tod_logfile$&"
11625 This variable contains the date in the format yyyymmdd. This is the format that
11626 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
11627 flag.
11628
11629 .vitem &$tod_zone$&
11630 .vindex "&$tod_zone$&"
11631 This variable contains the numerical value of the local timezone, for example:
11632 -0500.
11633
11634 .vitem &$tod_zulu$&
11635 .vindex "&$tod_zulu$&"
11636 This variable contains the UTC date and time in &"Zulu"& format, as specified
11637 by ISO 8601, for example: 20030221154023Z.
11638
11639 .vitem &$value$&
11640 .vindex "&$value$&"
11641 This variable contains the result of an expansion lookup, extraction operation,
11642 or external command, as described above. It is also used during a
11643 &*reduce*& expansion.
11644
11645 .vitem &$version_number$&
11646 .vindex "&$version_number$&"
11647 The version number of Exim.
11648
11649 .vitem &$warn_message_delay$&
11650 .vindex "&$warn_message_delay$&"
11651 This variable is set only during the creation of a message warning about a
11652 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
11653
11654 .vitem &$warn_message_recipients$&
11655 .vindex "&$warn_message_recipients$&"
11656 This variable is set only during the creation of a message warning about a
11657 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
11658 .endlist
11659 .ecindex IIDstrexp
11660
11661
11662
11663 . ////////////////////////////////////////////////////////////////////////////
11664 . ////////////////////////////////////////////////////////////////////////////
11665
11666 .chapter "Embedded Perl" "CHAPperl"
11667 .scindex IIDperl "Perl" "calling from Exim"
11668 Exim can be built to include an embedded Perl interpreter. When this is done,
11669 Perl subroutines can be called as part of the string expansion process. To make
11670 use of the Perl support, you need version 5.004 or later of Perl installed on
11671 your system. To include the embedded interpreter in the Exim binary, include
11672 the line
11673 .code
11674 EXIM_PERL = perl.o
11675 .endd
11676 in your &_Local/Makefile_& and then build Exim in the normal way.
11677
11678
11679 .section "Setting up so Perl can be used" "SECID85"
11680 .oindex "&%perl_startup%&"
11681 Access to Perl subroutines is via a global configuration option called
11682 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
11683 no &%perl_startup%& option in the Exim configuration file then no Perl
11684 interpreter is started and there is almost no overhead for Exim (since none of
11685 the Perl library will be paged in unless used). If there is a &%perl_startup%&
11686 option then the associated value is taken to be Perl code which is executed in
11687 a newly created Perl interpreter.
11688
11689 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
11690 need backslashes before any characters to escape special meanings. The option
11691 should usually be something like
11692 .code
11693 perl_startup = do '/etc/exim.pl'
11694 .endd
11695 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
11696 use from Exim. Exim can be configured either to start up a Perl interpreter as
11697 soon as it is entered, or to wait until the first time it is needed. Starting
11698 the interpreter at the beginning ensures that it is done while Exim still has
11699 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
11700 fact used in a particular run. Also, note that this does not mean that Exim is
11701 necessarily running as root when Perl is called at a later time. By default,
11702 the interpreter is started only when it is needed, but this can be changed in
11703 two ways:
11704
11705 .ilist
11706 .oindex "&%perl_at_start%&"
11707 Setting &%perl_at_start%& (a boolean option) in the configuration requests
11708 a startup when Exim is entered.
11709 .next
11710 The command line option &%-ps%& also requests a startup when Exim is entered,
11711 overriding the setting of &%perl_at_start%&.
11712 .endlist
11713
11714 There is also a command line option &%-pd%& (for delay) which suppresses the
11715 initial startup, even if &%perl_at_start%& is set.
11716
11717
11718 .section "Calling Perl subroutines" "SECID86"
11719 When the configuration file includes a &%perl_startup%& option you can make use
11720 of the string expansion item to call the Perl subroutines that are defined
11721 by the &%perl_startup%& code. The operator is used in any of the following
11722 forms:
11723 .code
11724 ${perl{foo}}
11725 ${perl{foo}{argument}}
11726 ${perl{foo}{argument1}{argument2} ... }
11727 .endd
11728 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
11729 arguments may be passed. Passing more than this results in an expansion failure
11730 with an error message of the form
11731 .code
11732 Too many arguments passed to Perl subroutine "foo" (max is 8)
11733 .endd
11734 The return value of the Perl subroutine is evaluated in a scalar context before
11735 it is passed back to Exim to be inserted into the expanded string. If the
11736 return value is &'undef'&, the expansion is forced to fail in the same way as
11737 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
11738 by obeying Perl's &%die%& function, the expansion fails with the error message
11739 that was passed to &%die%&.
11740
11741
11742 .section "Calling Exim functions from Perl" "SECID87"
11743 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
11744 is available to call back into Exim's string expansion function. For example,
11745 the Perl code
11746 .code
11747 my $lp = Exim::expand_string('$local_part');
11748 .endd
11749 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
11750 Note those are single quotes and not double quotes to protect against
11751 &$local_part$& being interpolated as a Perl variable.
11752
11753 If the string expansion is forced to fail by a &"fail"& item, the result of
11754 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
11755 expansion string, the Perl call from the original expansion string fails with
11756 an appropriate error message, in the same way as if &%die%& were used.
11757
11758 .cindex "debugging" "from embedded Perl"
11759 .cindex "log" "writing from embedded Perl"
11760 Two other Exim functions are available for use from within Perl code.
11761 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
11762 debugging is enabled. If you want a newline at the end, you must supply it.
11763 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
11764 timestamp. In this case, you should not supply a terminating newline.
11765
11766
11767 .section "Use of standard output and error by Perl" "SECID88"
11768 .cindex "Perl" "standard output and error"
11769 You should not write to the standard error or output streams from within your
11770 Perl code, as it is not defined how these are set up. In versions of Exim
11771 before 4.50, it is possible for the standard output or error to refer to the
11772 SMTP connection during message reception via the daemon. Writing to this stream
11773 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
11774 error streams are connected to &_/dev/null_& in the daemon. The chaos is
11775 avoided, but the output is lost.
11776
11777 .cindex "Perl" "use of &%warn%&"
11778 The Perl &%warn%& statement writes to the standard error stream by default.
11779 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
11780 you have no control. When Exim starts up the Perl interpreter, it arranges for
11781 output from the &%warn%& statement to be written to the Exim main log. You can
11782 change this by including appropriate Perl magic somewhere in your Perl code.
11783 For example, to discard &%warn%& output completely, you need this:
11784 .code
11785 $SIG{__WARN__} = sub { };
11786 .endd
11787 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
11788 example, the code for the subroutine is empty, so it does nothing, but you can
11789 include any Perl code that you like. The text of the &%warn%& message is passed
11790 as the first subroutine argument.
11791 .ecindex IIDperl
11792
11793
11794 . ////////////////////////////////////////////////////////////////////////////
11795 . ////////////////////////////////////////////////////////////////////////////
11796
11797 .chapter "Starting the daemon and the use of network interfaces" &&&
11798 "CHAPinterfaces" &&&
11799 "Starting the daemon"
11800 .cindex "daemon" "starting"
11801 .cindex "interface" "listening"
11802 .cindex "network interface"
11803 .cindex "interface" "network"
11804 .cindex "IP address" "for listening"
11805 .cindex "daemon" "listening IP addresses"
11806 .cindex "TCP/IP" "setting listening interfaces"
11807 .cindex "TCP/IP" "setting listening ports"
11808 A host that is connected to a TCP/IP network may have one or more physical
11809 hardware network interfaces. Each of these interfaces may be configured as one
11810 or more &"logical"& interfaces, which are the entities that a program actually
11811 works with. Each of these logical interfaces is associated with an IP address.
11812 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
11813 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
11814 knowledge about the host's interfaces for use in three different circumstances:
11815
11816 .olist
11817 When a listening daemon is started, Exim needs to know which interfaces
11818 and ports to listen on.
11819 .next
11820 When Exim is routing an address, it needs to know which IP addresses
11821 are associated with local interfaces. This is required for the correct
11822 processing of MX lists by removing the local host and others with the
11823 same or higher priority values. Also, Exim needs to detect cases
11824 when an address is routed to an IP address that in fact belongs to the
11825 local host. Unless the &%self%& router option or the &%allow_localhost%&
11826 option of the smtp transport is set (as appropriate), this is treated
11827 as an error situation.
11828 .next
11829 When Exim connects to a remote host, it may need to know which interface to use
11830 for the outgoing connection.
11831 .endlist
11832
11833
11834 Exim's default behaviour is likely to be appropriate in the vast majority
11835 of cases. If your host has only one interface, and you want all its IP
11836 addresses to be treated in the same way, and you are using only the
11837 standard SMTP port, you should not need to take any special action. The
11838 rest of this chapter does not apply to you.
11839
11840 In a more complicated situation you may want to listen only on certain
11841 interfaces, or on different ports, and for this reason there are a number of
11842 options that can be used to influence Exim's behaviour. The rest of this
11843 chapter describes how they operate.
11844
11845 When a message is received over TCP/IP, the interface and port that were
11846 actually used are set in &$received_ip_address$& and &$received_port$&.
11847
11848
11849
11850 .section "Starting a listening daemon" "SECID89"
11851 When a listening daemon is started (by means of the &%-bd%& command line
11852 option), the interfaces and ports on which it listens are controlled by the
11853 following options:
11854
11855 .ilist
11856 &%daemon_smtp_ports%& contains a list of default ports. (For backward
11857 compatibility, this option can also be specified in the singular.)
11858 .next
11859 &%local_interfaces%& contains list of interface IP addresses on which to
11860 listen. Each item may optionally also specify a port.
11861 .endlist
11862
11863 The default list separator in both cases is a colon, but this can be changed as
11864 described in section &<<SECTlistconstruct>>&. When IPv6 addresses are involved,
11865 it is usually best to change the separator to avoid having to double all the
11866 colons. For example:
11867 .code
11868 local_interfaces = <; 127.0.0.1 ; \
11869 192.168.23.65 ; \
11870 ::1 ; \
11871 3ffe:ffff:836f::fe86:a061
11872 .endd
11873 There are two different formats for specifying a port along with an IP address
11874 in &%local_interfaces%&:
11875
11876 .olist
11877 The port is added onto the address with a dot separator. For example, to listen
11878 on port 1234 on two different IP addresses:
11879 .code
11880 local_interfaces = <; 192.168.23.65.1234 ; \
11881 3ffe:ffff:836f::fe86:a061.1234
11882 .endd
11883 .next
11884 The IP address is enclosed in square brackets, and the port is added
11885 with a colon separator, for example:
11886 .code
11887 local_interfaces = <; [192.168.23.65]:1234 ; \
11888 [3ffe:ffff:836f::fe86:a061]:1234
11889 .endd
11890 .endlist
11891
11892 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
11893 default setting contains just one port:
11894 .code
11895 daemon_smtp_ports = smtp
11896 .endd
11897 If more than one port is listed, each interface that does not have its own port
11898 specified listens on all of them. Ports that are listed in
11899 &%daemon_smtp_ports%& can be identified either by name (defined in
11900 &_/etc/services_&) or by number. However, when ports are given with individual
11901 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
11902
11903
11904
11905 .section "Special IP listening addresses" "SECID90"
11906 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
11907 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
11908 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
11909 instead of setting up separate listening sockets for each interface. The
11910 default value of &%local_interfaces%& is
11911 .code
11912 local_interfaces = 0.0.0.0
11913 .endd
11914 when Exim is built without IPv6 support; otherwise it is:
11915 .code
11916 local_interfaces = <; ::0 ; 0.0.0.0
11917 .endd
11918 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
11919
11920
11921
11922 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
11923 The &%-oX%& command line option can be used to override the values of
11924 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
11925 instance. Another way of doing this would be to use macros and the &%-D%&
11926 option. However, &%-oX%& can be used by any admin user, whereas modification of
11927 the runtime configuration by &%-D%& is allowed only when the caller is root or
11928 exim.
11929
11930 The value of &%-oX%& is a list of items. The default colon separator can be
11931 changed in the usual way if required. If there are any items that do not
11932 contain dots or colons (that is, are not IP addresses), the value of
11933 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
11934 items that do contain dots or colons, the value of &%local_interfaces%& is
11935 replaced by those items. Thus, for example,
11936 .code
11937 -oX 1225
11938 .endd
11939 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
11940 whereas
11941 .code
11942 -oX 192.168.34.5.1125
11943 .endd
11944 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
11945 (However, since &%local_interfaces%& now contains no items without ports, the
11946 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
11947
11948
11949
11950 .section "Support for the obsolete SSMTP (or SMTPS) protocol" "SECTsupobssmt"
11951 .cindex "ssmtp protocol"
11952 .cindex "smtps protocol"
11953 .cindex "SMTP" "ssmtp protocol"
11954 .cindex "SMTP" "smtps protocol"
11955 Exim supports the obsolete SSMTP protocol (also known as SMTPS) that was used
11956 before the STARTTLS command was standardized for SMTP. Some legacy clients
11957 still use this protocol. If the &%tls_on_connect_ports%& option is set to a
11958 list of port numbers, connections to those ports must use SSMTP. The most
11959 common use of this option is expected to be
11960 .code
11961 tls_on_connect_ports = 465
11962 .endd
11963 because 465 is the usual port number used by the legacy clients. There is also
11964 a command line option &%-tls-on-connect%&, which forces all ports to behave in
11965 this way when a daemon is started.
11966
11967 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
11968 daemon to listen on those ports. You must still specify them in
11969 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
11970 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
11971 connections via the daemon.)
11972
11973
11974
11975
11976 .section "IPv6 address scopes" "SECID92"
11977 .cindex "IPv6" "address scopes"
11978 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
11979 can, in principle, have the same link-local IPv6 address on different
11980 interfaces. Thus, additional information is needed, over and above the IP
11981 address, to distinguish individual interfaces. A convention of using a
11982 percent sign followed by something (often the interface name) has been
11983 adopted in some cases, leading to addresses like this:
11984 .code
11985 fe80::202:b3ff:fe03:45c1%eth0
11986 .endd
11987 To accommodate this usage, a percent sign followed by an arbitrary string is
11988 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
11989 to convert a textual IPv6 address for actual use. This function recognizes the
11990 percent convention in operating systems that support it, and it processes the
11991 address appropriately. Unfortunately, some older libraries have problems with
11992 &[getaddrinfo()]&. If
11993 .code
11994 IPV6_USE_INET_PTON=yes
11995 .endd
11996 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
11997 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
11998 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
11999 function.) Of course, this means that the additional functionality of
12000 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
12001
12002 .section "Disabling IPv6" "SECID93"
12003 .cindex "IPv6" "disabling"
12004 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
12005 run on a host whose kernel does not support IPv6. The binary will fall back to
12006 using IPv4, but it may waste resources looking up AAAA records, and trying to
12007 connect to IPv6 addresses, causing delays to mail delivery. If you set the
12008 .oindex "&%disable_ipv6%&"
12009 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
12010 activities take place. AAAA records are never looked up, and any IPv6 addresses
12011 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
12012 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
12013 to handle IPv6 literal addresses.
12014
12015 On the other hand, when IPv6 is in use, there may be times when you want to
12016 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
12017 option to globally suppress the lookup of AAAA records for specified domains,
12018 and you can use the &%ignore_target_hosts%& generic router option to ignore
12019 IPv6 addresses in an individual router.
12020
12021
12022
12023 .section "Examples of starting a listening daemon" "SECID94"
12024 The default case in an IPv6 environment is
12025 .code
12026 daemon_smtp_ports = smtp
12027 local_interfaces = <; ::0 ; 0.0.0.0
12028 .endd
12029 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
12030 Either one or two sockets may be used, depending on the characteristics of
12031 the TCP/IP stack. (This is complicated and messy; for more information,
12032 read the comments in the &_daemon.c_& source file.)
12033
12034 To specify listening on ports 25 and 26 on all interfaces:
12035 .code
12036 daemon_smtp_ports = 25 : 26
12037 .endd
12038 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
12039 .code
12040 local_interfaces = <; ::0.25 ; ::0.26 \
12041 0.0.0.0.25 ; 0.0.0.0.26
12042 .endd
12043 To listen on the default port on all IPv4 interfaces, and on port 26 on the
12044 IPv4 loopback address only:
12045 .code
12046 local_interfaces = 0.0.0.0 : 127.0.0.1.26
12047 .endd
12048 To specify listening on the default port on specific interfaces only:
12049 .code
12050 local_interfaces = 192.168.34.67 : 192.168.34.67
12051 .endd
12052 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
12053
12054
12055
12056 .section "Recognizing the local host" "SECTreclocipadd"
12057 The &%local_interfaces%& option is also used when Exim needs to determine
12058 whether or not an IP address refers to the local host. That is, the IP
12059 addresses of all the interfaces on which a daemon is listening are always
12060 treated as local.
12061
12062 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
12063 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
12064 available interfaces from the operating system, and extracts the relevant
12065 (that is, IPv4 or IPv6) addresses to use for checking.
12066
12067 Some systems set up large numbers of virtual interfaces in order to provide
12068 many virtual web servers. In this situation, you may want to listen for
12069 email on only a few of the available interfaces, but nevertheless treat all
12070 interfaces as local when routing. You can do this by setting
12071 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
12072 &"all"& wildcard values. These addresses are recognized as local, but are not
12073 used for listening. Consider this example:
12074 .code
12075 local_interfaces = <; 127.0.0.1 ; ::1 ; \
12076 192.168.53.235 ; \
12077 3ffe:2101:12:1:a00:20ff:fe86:a061
12078
12079 extra_local_interfaces = <; ::0 ; 0.0.0.0
12080 .endd
12081 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
12082 address, but all available interface addresses are treated as local when
12083 Exim is routing.
12084
12085 In some environments the local host name may be in an MX list, but with an IP
12086 address that is not assigned to any local interface. In other cases it may be
12087 desirable to treat other host names as if they referred to the local host. Both
12088 these cases can be handled by setting the &%hosts_treat_as_local%& option.
12089 This contains host names rather than IP addresses. When a host is referenced
12090 during routing, either via an MX record or directly, it is treated as the local
12091 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
12092 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
12093
12094
12095
12096 .section "Delivering to a remote host" "SECID95"
12097 Delivery to a remote host is handled by the smtp transport. By default, it
12098 allows the system's TCP/IP functions to choose which interface to use (if
12099 there is more than one) when connecting to a remote host. However, the
12100 &%interface%& option can be set to specify which interface is used. See the
12101 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
12102 details.
12103
12104
12105
12106
12107 . ////////////////////////////////////////////////////////////////////////////
12108 . ////////////////////////////////////////////////////////////////////////////
12109
12110 .chapter "Main configuration" "CHAPmainconfig"
12111 .scindex IIDconfima "configuration file" "main section"
12112 .scindex IIDmaiconf "main configuration"
12113 The first part of the run time configuration file contains three types of item:
12114
12115 .ilist
12116 Macro definitions: These lines start with an upper case letter. See section
12117 &<<SECTmacrodefs>>& for details of macro processing.
12118 .next
12119 Named list definitions: These lines start with one of the words &"domainlist"&,
12120 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
12121 section &<<SECTnamedlists>>&.
12122 .next
12123 Main configuration settings: Each setting occupies one line of the file
12124 (with possible continuations). If any setting is preceded by the word
12125 &"hide"&, the &%-bP%& command line option displays its value to admin users
12126 only. See section &<<SECTcos>>& for a description of the syntax of these option
12127 settings.
12128 .endlist
12129
12130 This chapter specifies all the main configuration options, along with their
12131 types and default values. For ease of finding a particular option, they appear
12132 in alphabetical order in section &<<SECTalomo>>& below. However, because there
12133 are now so many options, they are first listed briefly in functional groups, as
12134 an aid to finding the name of the option you are looking for. Some options are
12135 listed in more than one group.
12136
12137 .section "Miscellaneous" "SECID96"
12138 .table2
12139 .row &%bi_command%& "to run for &%-bi%& command line option"
12140 .row &%disable_ipv6%& "do no IPv6 processing"
12141 .row &%keep_malformed%& "for broken files &-- should not happen"
12142 .row &%localhost_number%& "for unique message ids in clusters"
12143 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
12144 .row &%message_body_visible%& "how much to show in &$message_body$&"
12145 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
12146 .row &%print_topbitchars%& "top-bit characters are printing"
12147 .row &%timezone%& "force time zone"
12148 .endtable
12149
12150
12151 .section "Exim parameters" "SECID97"
12152 .table2
12153 .row &%exim_group%& "override compiled-in value"
12154 .row &%exim_path%& "override compiled-in value"
12155 .row &%exim_user%& "override compiled-in value"
12156 .row &%primary_hostname%& "default from &[uname()]&"
12157 .row &%split_spool_directory%& "use multiple directories"
12158 .row &%spool_directory%& "override compiled-in value"
12159 .endtable
12160
12161
12162
12163 .section "Privilege controls" "SECID98"
12164 .table2
12165 .row &%admin_groups%& "groups that are Exim admin users"
12166 .row &%deliver_drop_privilege%& "drop root for delivery processes"
12167 .row &%local_from_check%& "insert &'Sender:'& if necessary"
12168 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
12169 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
12170 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
12171 .row &%never_users%& "do not run deliveries as these"
12172 .row &%prod_requires_admin%& "forced delivery requires admin user"
12173 .row &%queue_list_requires_admin%& "queue listing requires admin user"
12174 .row &%trusted_groups%& "groups that are trusted"
12175 .row &%trusted_users%& "users that are trusted"
12176 .endtable
12177
12178
12179
12180 .section "Logging" "SECID99"
12181 .table2
12182 .row &%hosts_connection_nolog%& "exemption from connect logging"
12183 .row &%log_file_path%& "override compiled-in value"
12184 .row &%log_selector%& "set/unset optional logging"
12185 .row &%log_timezone%& "add timezone to log lines"
12186 .row &%message_logs%& "create per-message logs"
12187 .row &%preserve_message_logs%& "after message completion"
12188 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
12189 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
12190 .row &%syslog_facility%& "set syslog &""facility""& field"
12191 .row &%syslog_processname%& "set syslog &""ident""& field"
12192 .row &%syslog_timestamp%& "timestamp syslog lines"
12193 .row &%write_rejectlog%& "control use of message log"
12194 .endtable
12195
12196
12197
12198 .section "Frozen messages" "SECID100"
12199 .table2
12200 .row &%auto_thaw%& "sets time for retrying frozen messages"
12201 .row &%freeze_tell%& "send message when freezing"
12202 .row &%move_frozen_messages%& "to another directory"
12203 .row &%timeout_frozen_after%& "keep frozen messages only so long"
12204 .endtable
12205
12206
12207
12208 .section "Data lookups" "SECID101"
12209 .table2
12210 .row &%ibase_servers%& "InterBase servers"
12211 .row &%ldap_default_servers%& "used if no server in query"
12212 .row &%ldap_version%& "set protocol version"
12213 .row &%lookup_open_max%& "lookup files held open"
12214 .row &%mysql_servers%& "default MySQL servers"
12215 .row &%oracle_servers%& "Oracle servers"
12216 .row &%pgsql_servers%& "default PostgreSQL servers"
12217 .row &%sqlite_lock_timeout%& "as it says"
12218 .endtable
12219
12220
12221
12222 .section "Message ids" "SECID102"
12223 .table2
12224 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
12225 .row &%message_id_header_text%& "ditto"
12226 .endtable
12227
12228
12229
12230 .section "Embedded Perl Startup" "SECID103"
12231 .table2
12232 .row &%perl_at_start%& "always start the interpreter"
12233 .row &%perl_startup%& "code to obey when starting Perl"
12234 .endtable
12235
12236
12237
12238 .section "Daemon" "SECID104"
12239 .table2
12240 .row &%daemon_smtp_ports%& "default ports"
12241 .row &%daemon_startup_retries%& "number of times to retry"
12242 .row &%daemon_startup_sleep%& "time to sleep between tries"
12243 .row &%extra_local_interfaces%& "not necessarily listened on"
12244 .row &%local_interfaces%& "on which to listen, with optional ports"
12245 .row &%pid_file_path%& "override compiled-in value"
12246 .row &%queue_run_max%& "maximum simultaneous queue runners"
12247 .endtable
12248
12249
12250
12251 .section "Resource control" "SECID105"
12252 .table2
12253 .row &%check_log_inodes%& "before accepting a message"
12254 .row &%check_log_space%& "before accepting a message"
12255 .row &%check_spool_inodes%& "before accepting a message"
12256 .row &%check_spool_space%& "before accepting a message"
12257 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
12258 .row &%queue_only_load%& "queue incoming if load high"
12259 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
12260 .row &%queue_run_max%& "maximum simultaneous queue runners"
12261 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
12262 .row &%smtp_accept_max%& "simultaneous incoming connections"
12263 .row &%smtp_accept_max_nonmail%& "non-mail commands"
12264 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
12265 .row &%smtp_accept_max_per_connection%& "messages per connection"
12266 .row &%smtp_accept_max_per_host%& "connections from one host"
12267 .row &%smtp_accept_queue%& "queue mail if more connections"
12268 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
12269 connection"
12270 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
12271 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
12272 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
12273 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
12274 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
12275 .endtable
12276
12277
12278
12279 .section "Policy controls" "SECID106"
12280 .table2
12281 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
12282 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
12283 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
12284 .row &%acl_smtp_auth%& "ACL for AUTH"
12285 .row &%acl_smtp_connect%& "ACL for connection"
12286 .row &%acl_smtp_data%& "ACL for DATA"
12287 .row &%acl_smtp_etrn%& "ACL for ETRN"
12288 .row &%acl_smtp_expn%& "ACL for EXPN"
12289 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
12290 .row &%acl_smtp_mail%& "ACL for MAIL"
12291 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
12292 .row &%acl_smtp_mime%& "ACL for MIME parts"
12293 .row &%acl_smtp_predata%& "ACL for start of data"
12294 .row &%acl_smtp_quit%& "ACL for QUIT"
12295 .row &%acl_smtp_rcpt%& "ACL for RCPT"
12296 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
12297 .row &%acl_smtp_vrfy%& "ACL for VRFY"
12298 .row &%av_scanner%& "specify virus scanner"
12299 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
12300 words""&"
12301 .row &%dns_csa_search_limit%& "control CSA parent search depth"
12302 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
12303 .row &%header_maxsize%& "total size of message header"
12304 .row &%header_line_maxsize%& "individual header line limit"
12305 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
12306 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
12307 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
12308 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
12309 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
12310 .row &%host_lookup%& "host name looked up for these hosts"
12311 .row &%host_lookup_order%& "order of DNS and local name lookups"
12312 .row &%host_reject_connection%& "reject connection from these hosts"
12313 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
12314 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
12315 .row &%message_size_limit%& "for all messages"
12316 .row &%percent_hack_domains%& "recognize %-hack for these domains"
12317 .row &%spamd_address%& "set interface to SpamAssassin"
12318 .row &%strict_acl_vars%& "object to unset ACL variables"
12319 .endtable
12320
12321
12322
12323 .section "Callout cache" "SECID107"
12324 .table2
12325 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
12326 item"
12327 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
12328 item"
12329 .row &%callout_negative_expire%& "timeout for negative address cache item"
12330 .row &%callout_positive_expire%& "timeout for positive address cache item"
12331 .row &%callout_random_local_part%& "string to use for &""random""& testing"
12332 .endtable
12333
12334
12335
12336 .section "TLS" "SECID108"
12337 .table2
12338 .row &%gnutls_require_kx%& "control GnuTLS key exchanges"
12339 .row &%gnutls_require_mac%& "control GnuTLS MAC algorithms"
12340 .row &%gnutls_require_protocols%& "control GnuTLS protocols"
12341 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
12342 .row &%tls_certificate%& "location of server certificate"
12343 .row &%tls_crl%& "certificate revocation list"
12344 .row &%tls_dhparam%& "DH parameters for server"
12345 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
12346 .row &%tls_privatekey%& "location of server private key"
12347 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
12348 .row &%tls_require_ciphers%& "specify acceptable ciphers"
12349 .row &%tls_try_verify_hosts%& "try to verify client certificate"
12350 .row &%tls_verify_certificates%& "expected client certificates"
12351 .row &%tls_verify_hosts%& "insist on client certificate verify"
12352 .endtable
12353
12354
12355
12356 .section "Local user handling" "SECID109"
12357 .table2
12358 .row &%finduser_retries%& "useful in NIS environments"
12359 .row &%gecos_name%& "used when creating &'Sender:'&"
12360 .row &%gecos_pattern%& "ditto"
12361 .row &%max_username_length%& "for systems that truncate"
12362 .row &%unknown_login%& "used when no login name found"
12363 .row &%unknown_username%& "ditto"
12364 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
12365 .row &%uucp_from_sender%& "ditto"
12366 .endtable
12367
12368
12369
12370 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
12371 .table2
12372 .row &%header_maxsize%& "total size of message header"
12373 .row &%header_line_maxsize%& "individual header line limit"
12374 .row &%message_size_limit%& "applies to all messages"
12375 .row &%percent_hack_domains%& "recognize %-hack for these domains"
12376 .row &%received_header_text%& "expanded to make &'Received:'&"
12377 .row &%received_headers_max%& "for mail loop detection"
12378 .row &%recipients_max%& "limit per message"
12379 .row &%recipients_max_reject%& "permanently reject excess recipients"
12380 .endtable
12381
12382
12383
12384
12385 .section "Non-SMTP incoming messages" "SECID111"
12386 .table2
12387 .row &%receive_timeout%& "for non-SMTP messages"
12388 .endtable
12389
12390
12391
12392
12393
12394 .section "Incoming SMTP messages" "SECID112"
12395 See also the &'Policy controls'& section above.
12396
12397 .table2
12398 .row &%host_lookup%& "host name looked up for these hosts"
12399 .row &%host_lookup_order%& "order of DNS and local name lookups"
12400 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
12401 .row &%rfc1413_hosts%& "make ident calls to these hosts"
12402 .row &%rfc1413_query_timeout%& "zero disables ident calls"
12403 .row &%sender_unqualified_hosts%& "may send unqualified senders"
12404 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
12405 .row &%smtp_accept_max%& "simultaneous incoming connections"
12406 .row &%smtp_accept_max_nonmail%& "non-mail commands"
12407 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
12408 .row &%smtp_accept_max_per_connection%& "messages per connection"
12409 .row &%smtp_accept_max_per_host%& "connections from one host"
12410 .row &%smtp_accept_queue%& "queue mail if more connections"
12411 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
12412 connection"
12413 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
12414 .row &%smtp_active_hostname%& "host name to use in messages"
12415 .row &%smtp_banner%& "text for welcome banner"
12416 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
12417 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
12418 .row &%smtp_enforce_sync%& "of SMTP command/responses"
12419 .row &%smtp_etrn_command%& "what to run for ETRN"
12420 .row &%smtp_etrn_serialize%& "only one at once"
12421 .row &%smtp_load_reserve%& "only reserve hosts if this load"
12422 .row &%smtp_max_unknown_commands%& "before dropping connection"
12423 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
12424 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
12425 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
12426 .row &%smtp_receive_timeout%& "per command or data line"
12427 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
12428 .row &%smtp_return_error_details%& "give detail on rejections"
12429 .endtable
12430
12431
12432
12433 .section "SMTP extensions" "SECID113"
12434 .table2
12435 .row &%accept_8bitmime%& "advertise 8BITMIME"
12436 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
12437 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
12438 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
12439 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
12440 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
12441 .endtable
12442
12443
12444
12445 .section "Processing messages" "SECID114"
12446 .table2
12447 .row &%allow_domain_literals%& "recognize domain literal syntax"
12448 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
12449 .row &%allow_utf8_domains%& "in addresses"
12450 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
12451 words""&"
12452 .row &%delivery_date_remove%& "from incoming messages"
12453 .row &%envelope_to_remove%& "from incoming messages"
12454 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
12455 .row &%headers_charset%& "default for translations"
12456 .row &%qualify_domain%& "default for senders"
12457 .row &%qualify_recipient%& "default for recipients"
12458 .row &%return_path_remove%& "from incoming messages"
12459 .row &%strip_excess_angle_brackets%& "in addresses"
12460 .row &%strip_trailing_dot%& "at end of addresses"
12461 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
12462 .endtable
12463
12464
12465
12466 .section "System filter" "SECID115"
12467 .table2
12468 .row &%system_filter%& "locate system filter"
12469 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
12470 directory"
12471 .row &%system_filter_file_transport%& "transport for delivery to a file"
12472 .row &%system_filter_group%& "group for filter running"
12473 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
12474 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
12475 .row &%system_filter_user%& "user for filter running"
12476 .endtable
12477
12478
12479
12480 .section "Routing and delivery" "SECID116"
12481 .table2
12482 .row &%disable_ipv6%& "do no IPv6 processing"
12483 .row &%dns_again_means_nonexist%& "for broken domains"
12484 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
12485 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
12486 .row &%dns_retrans%& "parameter for resolver"
12487 .row &%dns_retry%& "parameter for resolver"
12488 .row &%hold_domains%& "hold delivery for these domains"
12489 .row &%local_interfaces%& "for routing checks"
12490 .row &%queue_domains%& "no immediate delivery for these"
12491 .row &%queue_only%& "no immediate delivery at all"
12492 .row &%queue_only_file%& "no immediate delivery if file exists"
12493 .row &%queue_only_load%& "no immediate delivery if load is high"
12494 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
12495 .row &%queue_only_override%& "allow command line to override"
12496 .row &%queue_run_in_order%& "order of arrival"
12497 .row &%queue_run_max%& "of simultaneous queue runners"
12498 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
12499 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
12500 .row &%remote_sort_domains%& "order of remote deliveries"
12501 .row &%retry_data_expire%& "timeout for retry data"
12502 .row &%retry_interval_max%& "safety net for retry rules"
12503 .endtable
12504
12505
12506
12507 .section "Bounce and warning messages" "SECID117"
12508 .table2
12509 .row &%bounce_message_file%& "content of bounce"
12510 .row &%bounce_message_text%& "content of bounce"
12511 .row &%bounce_return_body%& "include body if returning message"
12512 .row &%bounce_return_message%& "include original message in bounce"
12513 .row &%bounce_return_size_limit%& "limit on returned message"
12514 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
12515 .row &%dsn_from%& "set &'From:'& contents in bounces"
12516 .row &%errors_copy%& "copy bounce messages"
12517 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
12518 .row &%delay_warning%& "time schedule"
12519 .row &%delay_warning_condition%& "condition for warning messages"
12520 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
12521 .row &%smtp_return_error_details%& "give detail on rejections"
12522 .row &%warn_message_file%& "content of warning message"
12523 .endtable
12524
12525
12526
12527 .section "Alphabetical list of main options" "SECTalomo"
12528 Those options that undergo string expansion before use are marked with
12529 &dagger;.
12530
12531 .option accept_8bitmime main boolean false
12532 .cindex "8BITMIME"
12533 .cindex "8-bit characters"
12534 This option causes Exim to send 8BITMIME in its response to an SMTP
12535 EHLO command, and to accept the BODY= parameter on MAIL commands.
12536 However, though Exim is 8-bit clean, it is not a protocol converter, and it
12537 takes no steps to do anything special with messages received by this route.
12538 Consequently, this option is turned off by default.
12539
12540 .option acl_not_smtp main string&!! unset
12541 .cindex "&ACL;" "for non-SMTP messages"
12542 .cindex "non-SMTP messages" "ACLs for"
12543 This option defines the ACL that is run when a non-SMTP message has been
12544 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
12545 further details.
12546
12547 .option acl_not_smtp_mime main string&!! unset
12548 This option defines the ACL that is run for individual MIME parts of non-SMTP
12549 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
12550 SMTP messages.
12551
12552 .option acl_not_smtp_start main string&!! unset
12553 .cindex "&ACL;" "at start of non-SMTP message"
12554 .cindex "non-SMTP messages" "ACLs for"
12555 This option defines the ACL that is run before Exim starts reading a
12556 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
12557
12558 .option acl_smtp_auth main string&!! unset
12559 .cindex "&ACL;" "setting up for SMTP commands"
12560 .cindex "AUTH" "ACL for"
12561 This option defines the ACL that is run when an SMTP AUTH command is
12562 received. See chapter &<<CHAPACL>>& for further details.
12563
12564 .option acl_smtp_connect main string&!! unset
12565 .cindex "&ACL;" "on SMTP connection"
12566 This option defines the ACL that is run when an SMTP connection is received.
12567 See chapter &<<CHAPACL>>& for further details.
12568
12569 .option acl_smtp_data main string&!! unset
12570 .cindex "DATA" "ACL for"
12571 This option defines the ACL that is run after an SMTP DATA command has been
12572 processed and the message itself has been received, but before the final
12573 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
12574
12575 .option acl_smtp_etrn main string&!! unset
12576 .cindex "ETRN" "ACL for"
12577 This option defines the ACL that is run when an SMTP ETRN command is
12578 received. See chapter &<<CHAPACL>>& for further details.
12579
12580 .option acl_smtp_expn main string&!! unset
12581 .cindex "EXPN" "ACL for"
12582 This option defines the ACL that is run when an SMTP EXPN command is
12583 received. See chapter &<<CHAPACL>>& for further details.
12584
12585 .option acl_smtp_helo main string&!! unset
12586 .cindex "EHLO" "ACL for"
12587 .cindex "HELO" "ACL for"
12588 This option defines the ACL that is run when an SMTP EHLO or HELO
12589 command is received. See chapter &<<CHAPACL>>& for further details.
12590
12591
12592 .option acl_smtp_mail main string&!! unset
12593 .cindex "MAIL" "ACL for"
12594 This option defines the ACL that is run when an SMTP MAIL command is
12595 received. See chapter &<<CHAPACL>>& for further details.
12596
12597 .option acl_smtp_mailauth main string&!! unset
12598 .cindex "AUTH" "on MAIL command"
12599 This option defines the ACL that is run when there is an AUTH parameter on
12600 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
12601 &<<CHAPSMTPAUTH>>& for details of authentication.
12602
12603 .option acl_smtp_mime main string&!! unset
12604 .cindex "MIME content scanning" "ACL for"
12605 This option is available when Exim is built with the content-scanning
12606 extension. It defines the ACL that is run for each MIME part in a message. See
12607 section &<<SECTscanmimepart>>& for details.
12608
12609 .option acl_smtp_predata main string&!! unset
12610 This option defines the ACL that is run when an SMTP DATA command is
12611 received, before the message itself is received. See chapter &<<CHAPACL>>& for
12612 further details.
12613
12614 .option acl_smtp_quit main string&!! unset
12615 .cindex "QUIT, ACL for"
12616 This option defines the ACL that is run when an SMTP QUIT command is
12617 received. See chapter &<<CHAPACL>>& for further details.
12618
12619 .option acl_smtp_rcpt main string&!! unset
12620 .cindex "RCPT" "ACL for"
12621 This option defines the ACL that is run when an SMTP RCPT command is
12622 received. See chapter &<<CHAPACL>>& for further details.
12623
12624 .option acl_smtp_starttls main string&!! unset
12625 .cindex "STARTTLS, ACL for"
12626 This option defines the ACL that is run when an SMTP STARTTLS command is
12627 received. See chapter &<<CHAPACL>>& for further details.
12628
12629 .option acl_smtp_vrfy main string&!! unset
12630 .cindex "VRFY" "ACL for"
12631 This option defines the ACL that is run when an SMTP VRFY command is
12632 received. See chapter &<<CHAPACL>>& for further details.
12633
12634 .option admin_groups main "string list&!!" unset
12635 .cindex "admin user"
12636 This option is expanded just once, at the start of Exim's processing. If the
12637 current group or any of the supplementary groups of an Exim caller is in this
12638 colon-separated list, the caller has admin privileges. If all your system
12639 programmers are in a specific group, for example, you can give them all Exim
12640 admin privileges by putting that group in &%admin_groups%&. However, this does
12641 not permit them to read Exim's spool files (whose group owner is the Exim gid).
12642 To permit this, you have to add individuals to the Exim group.
12643
12644 .option allow_domain_literals main boolean false
12645 .cindex "domain literal"
12646 If this option is set, the RFC 2822 domain literal format is permitted in
12647 email addresses. The option is not set by default, because the domain literal
12648 format is not normally required these days, and few people know about it. It
12649 has, however, been exploited by mail abusers.
12650
12651 Unfortunately, it seems that some DNS black list maintainers are using this
12652 format to report black listing to postmasters. If you want to accept messages
12653 addressed to your hosts by IP address, you need to set
12654 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
12655 domains (defined in the named domain list &%local_domains%& in the default
12656 configuration). This &"magic string"& matches the domain literal form of all
12657 the local host's IP addresses.
12658
12659
12660 .option allow_mx_to_ip main boolean false
12661 .cindex "MX record" "pointing to IP address"
12662 It appears that more and more DNS zone administrators are breaking the rules
12663 and putting domain names that look like IP addresses on the right hand side of
12664 MX records. Exim follows the rules and rejects this, giving an error message
12665 that explains the mis-configuration. However, some other MTAs support this
12666 practice, so to avoid &"Why can't Exim do this?"& complaints,
12667 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
12668 recommended, except when you have no other choice.
12669
12670 .option allow_utf8_domains main boolean false
12671 .cindex "domain" "UTF-8 characters in"
12672 .cindex "UTF-8" "in domain name"
12673 Lots of discussion is going on about internationalized domain names. One
12674 camp is strongly in favour of just using UTF-8 characters, and it seems
12675 that at least two other MTAs permit this. This option allows Exim users to
12676 experiment if they wish.
12677
12678 If it is set true, Exim's domain parsing function allows valid
12679 UTF-8 multicharacters to appear in domain name components, in addition to
12680 letters, digits, and hyphens. However, just setting this option is not
12681 enough; if you want to look up these domain names in the DNS, you must also
12682 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
12683 suitable setting is:
12684 .code
12685 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
12686 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
12687 .endd
12688 Alternatively, you can just disable this feature by setting
12689 .code
12690 dns_check_names_pattern =
12691 .endd
12692 That is, set the option to an empty string so that no check is done.
12693
12694
12695 .option auth_advertise_hosts main "host list&!!" *
12696 .cindex "authentication" "advertising"
12697 .cindex "AUTH" "advertising"
12698 If any server authentication mechanisms are configured, Exim advertises them in
12699 response to an EHLO command only if the calling host matches this list.
12700 Otherwise, Exim does not advertise AUTH.
12701 Exim does not accept AUTH commands from clients to which it has not
12702 advertised the availability of AUTH. The advertising of individual
12703 authentication mechanisms can be controlled by the use of the
12704 &%server_advertise_condition%& generic authenticator option on the individual
12705 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
12706
12707 Certain mail clients (for example, Netscape) require the user to provide a name
12708 and password for authentication if AUTH is advertised, even though it may
12709 not be needed (the host may accept messages from hosts on its local LAN without
12710 authentication, for example). The &%auth_advertise_hosts%& option can be used
12711 to make these clients more friendly by excluding them from the set of hosts to
12712 which Exim advertises AUTH.
12713
12714 .cindex "AUTH" "advertising when encrypted"
12715 If you want to advertise the availability of AUTH only when the connection
12716 is encrypted using TLS, you can make use of the fact that the value of this
12717 option is expanded, with a setting like this:
12718 .code
12719 auth_advertise_hosts = ${if eq{$tls_cipher}{}{}{*}}
12720 .endd
12721 .vindex "&$tls_cipher$&"
12722 If &$tls_cipher$& is empty, the session is not encrypted, and the result of
12723 the expansion is empty, thus matching no hosts. Otherwise, the result of the
12724 expansion is *, which matches all hosts.
12725
12726
12727 .option auto_thaw main time 0s
12728 .cindex "thawing messages"
12729 .cindex "unfreezing messages"
12730 If this option is set to a time greater than zero, a queue runner will try a
12731 new delivery attempt on any frozen message, other than a bounce message, if
12732 this much time has passed since it was frozen. This may result in the message
12733 being re-frozen if nothing has changed since the last attempt. It is a way of
12734 saying &"keep on trying, even though there are big problems"&.
12735
12736 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
12737 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
12738 thought to be very useful any more, and its use should probably be avoided.
12739
12740 .option av_scanner main string "see below"
12741 This option is available if Exim is built with the content-scanning extension.
12742 It specifies which anti-virus scanner to use. The default value is:
12743 .code
12744 sophie:/var/run/sophie
12745 .endd
12746 If the value of &%av_scanner%& starts with dollar character, it is expanded
12747 before use. See section &<<SECTscanvirus>>& for further details.
12748
12749
12750
12751 .option bi_command main string unset
12752 .oindex "&%-bi%&"
12753 This option supplies the name of a command that is run when Exim is called with
12754 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
12755 just the command name, it is not a complete command line. If an argument is
12756 required, it must come from the &%-oA%& command line option.
12757
12758
12759 .option bounce_message_file main string unset
12760 .cindex "bounce message" "customizing"
12761 .cindex "customizing" "bounce message"
12762 This option defines a template file containing paragraphs of text to be used
12763 for constructing bounce messages. Details of the file's contents are given in
12764 chapter &<<CHAPemsgcust>>&. See also &%warn_message_file%&.
12765
12766
12767 .option bounce_message_text main string unset
12768 When this option is set, its contents are included in the default bounce
12769 message immediately after &"This message was created automatically by mail
12770 delivery software."& It is not used if &%bounce_message_file%& is set.
12771
12772 .option bounce_return_body main boolean true
12773 .cindex "bounce message" "including body"
12774 This option controls whether the body of an incoming message is included in a
12775 bounce message when &%bounce_return_message%& is true. The default setting
12776 causes the entire message, both header and body, to be returned (subject to the
12777 value of &%bounce_return_size_limit%&). If this option is false, only the
12778 message header is included. In the case of a non-SMTP message containing an
12779 error that is detected during reception, only those header lines preceding the
12780 point at which the error was detected are returned.
12781 .cindex "bounce message" "including original"
12782
12783 .option bounce_return_message main boolean true
12784 If this option is set false, none of the original message is included in
12785 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
12786 &%bounce_return_body%&.
12787
12788
12789 .option bounce_return_size_limit main integer 100K
12790 .cindex "size" "of bounce, limit"
12791 .cindex "bounce message" "size limit"
12792 .cindex "limit" "bounce message size"
12793 This option sets a limit in bytes on the size of messages that are returned to
12794 senders as part of bounce messages when &%bounce_return_message%& is true. The
12795 limit should be less than the value of the global &%message_size_limit%& and of
12796 any &%message_size_limit%& settings on transports, to allow for the bounce text
12797 that Exim generates. If this option is set to zero there is no limit.
12798
12799 When the body of any message that is to be included in a bounce message is
12800 greater than the limit, it is truncated, and a comment pointing this out is
12801 added at the top. The actual cutoff may be greater than the value given, owing
12802 to the use of buffering for transferring the message in chunks (typically 8K in
12803 size). The idea is to save bandwidth on those undeliverable 15-megabyte
12804 messages.
12805
12806 .option bounce_sender_authentication main string unset
12807 .cindex "bounce message" "sender authentication"
12808 .cindex "authentication" "bounce message"
12809 .cindex "AUTH" "on bounce message"
12810 This option provides an authenticated sender address that is sent with any
12811 bounce messages generated by Exim that are sent over an authenticated SMTP
12812 connection. A typical setting might be:
12813 .code
12814 bounce_sender_authentication = mailer-daemon@my.domain.example
12815 .endd
12816 which would cause bounce messages to be sent using the SMTP command:
12817 .code
12818 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
12819 .endd
12820 The value of &%bounce_sender_authentication%& must always be a complete email
12821 address.
12822
12823 .option callout_domain_negative_expire main time 3h
12824 .cindex "caching" "callout timeouts"
12825 .cindex "callout" "caching timeouts"
12826 This option specifies the expiry time for negative callout cache data for a
12827 domain. See section &<<SECTcallver>>& for details of callout verification, and
12828 section &<<SECTcallvercache>>& for details of the caching.
12829
12830
12831 .option callout_domain_positive_expire main time 7d
12832 This option specifies the expiry time for positive callout cache data for a
12833 domain. See section &<<SECTcallver>>& for details of callout verification, and
12834 section &<<SECTcallvercache>>& for details of the caching.
12835
12836
12837 .option callout_negative_expire main time 2h
12838 This option specifies the expiry time for negative callout cache data for an
12839 address. See section &<<SECTcallver>>& for details of callout verification, and
12840 section &<<SECTcallvercache>>& for details of the caching.
12841
12842
12843 .option callout_positive_expire main time 24h
12844 This option specifies the expiry time for positive callout cache data for an
12845 address. See section &<<SECTcallver>>& for details of callout verification, and
12846 section &<<SECTcallvercache>>& for details of the caching.
12847
12848
12849 .option callout_random_local_part main string&!! "see below"
12850 This option defines the &"random"& local part that can be used as part of
12851 callout verification. The default value is
12852 .code
12853 $primary_host_name-$tod_epoch-testing
12854 .endd
12855 See section &<<CALLaddparcall>>& for details of how this value is used.
12856
12857
12858 .option check_log_inodes main integer 0
12859 See &%check_spool_space%& below.
12860
12861
12862 .option check_log_space main integer 0
12863 See &%check_spool_space%& below.
12864
12865 .oindex "&%check_rfc2047_length%&"
12866 .cindex "RFC 2047" "disabling length check"
12867 .option check_rfc2047_length main boolean true
12868 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
12869 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
12870 word; strings to be encoded that exceed this length are supposed to use
12871 multiple encoded words. By default, Exim does not recognize encoded words that
12872 exceed the maximum length. However, it seems that some software, in violation
12873 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
12874 set false, Exim recognizes encoded words of any length.
12875
12876
12877 .option check_spool_inodes main integer 0
12878 See &%check_spool_space%& below.
12879
12880
12881 .option check_spool_space main integer 0
12882 .cindex "checking disk space"
12883 .cindex "disk space, checking"
12884 .cindex "spool directory" "checking space"
12885 The four &%check_...%& options allow for checking of disk resources before a
12886 message is accepted.
12887
12888 .vindex "&$log_inodes$&"
12889 .vindex "&$log_space$&"
12890 .vindex "&$spool_inodes$&"
12891 .vindex "&$spool_space$&"
12892 When any of these options are set, they apply to all incoming messages. If you
12893 want to apply different checks to different kinds of message, you can do so by
12894 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
12895 &$spool_space$& in an ACL with appropriate additional conditions.
12896
12897
12898 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
12899 either value is greater than zero, for example:
12900 .code
12901 check_spool_space = 10M
12902 check_spool_inodes = 100
12903 .endd
12904 The spool partition is the one that contains the directory defined by
12905 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
12906 transit.
12907
12908 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
12909 files are written if either is greater than zero. These should be set only if
12910 &%log_file_path%& and &%spool_directory%& refer to different partitions.
12911
12912 If there is less space or fewer inodes than requested, Exim refuses to accept
12913 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
12914 error response to the MAIL command. If ESMTP is in use and there was a
12915 SIZE parameter on the MAIL command, its value is added to the
12916 &%check_spool_space%& value, and the check is performed even if
12917 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
12918
12919 The values for &%check_spool_space%& and &%check_log_space%& are held as a
12920 number of kilobytes. If a non-multiple of 1024 is specified, it is rounded up.
12921
12922 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
12923 failure a message is written to stderr and Exim exits with a non-zero code, as
12924 it obviously cannot send an error message of any kind.
12925
12926 .option daemon_smtp_ports main string &`smtp`&
12927 .cindex "port" "for daemon"
12928 .cindex "TCP/IP" "setting listening ports"
12929 This option specifies one or more default SMTP ports on which the Exim daemon
12930 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
12931 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
12932
12933 .option daemon_startup_retries main integer 9
12934 .cindex "daemon startup, retrying"
12935 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
12936 the daemon at startup when it cannot immediately bind a listening socket
12937 (typically because the socket is already in use): &%daemon_startup_retries%&
12938 defines the number of retries after the first failure, and
12939 &%daemon_startup_sleep%& defines the length of time to wait between retries.
12940
12941 .option daemon_startup_sleep main time 30s
12942 See &%daemon_startup_retries%&.
12943
12944 .option delay_warning main "time list" 24h
12945 .cindex "warning of delay"
12946 .cindex "delay warning, specifying"
12947 When a message is delayed, Exim sends a warning message to the sender at
12948 intervals specified by this option. The data is a colon-separated list of times
12949 after which to send warning messages. If the value of the option is an empty
12950 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
12951 message has been on the queue for longer than the last time, the last interval
12952 between the times is used to compute subsequent warning times. For example,
12953 with
12954 .code
12955 delay_warning = 4h:8h:24h
12956 .endd
12957 the first message is sent after 4 hours, the second after 8 hours, and
12958 the third one after 24 hours. After that, messages are sent every 16 hours,
12959 because that is the interval between the last two times on the list. If you set
12960 just one time, it specifies the repeat interval. For example, with:
12961 .code
12962 delay_warning = 6h
12963 .endd
12964 messages are repeated every six hours. To stop warnings after a given time, set
12965 a very large time at the end of the list. For example:
12966 .code
12967 delay_warning = 2h:12h:99d
12968 .endd
12969
12970 .option delay_warning_condition main string&!! "see below"
12971 .vindex "&$domain$&"
12972 The string is expanded at the time a warning message might be sent. If all the
12973 deferred addresses have the same domain, it is set in &$domain$& during the
12974 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
12975 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
12976 &"false"& (the comparison being done caselessly) then the warning message is
12977 not sent. The default is:
12978 .code
12979 delay_warning_condition = ${if or {\
12980 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
12981 { match{$h_precedence:}{(?i)bulk|list|junk} }\
12982 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
12983 } {no}{yes}}
12984 .endd
12985 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
12986 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
12987 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
12988 &"auto-replied"& in an &'Auto-Submitted:'& header.
12989
12990 .option deliver_drop_privilege main boolean false
12991 .cindex "unprivileged delivery"
12992 .cindex "delivery" "unprivileged"
12993 If this option is set true, Exim drops its root privilege at the start of a
12994 delivery process, and runs as the Exim user throughout. This severely restricts
12995 the kinds of local delivery that are possible, but is viable in certain types
12996 of configuration. There is a discussion about the use of root privilege in
12997 chapter &<<CHAPsecurity>>&.
12998
12999 .option deliver_queue_load_max main fixed-point unset
13000 .cindex "load average"
13001 .cindex "queue runner" "abandoning"
13002 When this option is set, a queue run is abandoned if the system load average
13003 becomes greater than the value of the option. The option has no effect on
13004 ancient operating systems on which Exim cannot determine the load average.
13005 See also &%queue_only_load%& and &%smtp_load_reserve%&.
13006
13007
13008 .option delivery_date_remove main boolean true
13009 .cindex "&'Delivery-date:'& header line"
13010 Exim's transports have an option for adding a &'Delivery-date:'& header to a
13011 message when it is delivered, in exactly the same way as &'Return-path:'& is
13012 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
13013 should not be present in incoming messages, and this option causes them to be
13014 removed at the time the message is received, to avoid any problems that might
13015 occur when a delivered message is subsequently sent on to some other recipient.
13016
13017 .option disable_fsync main boolean false
13018 .cindex "&[fsync()]&, disabling"
13019 This option is available only if Exim was built with the compile-time option
13020 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
13021 a runtime configuration generates an &"unknown option"& error. You should not
13022 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
13023 really, really, really understand what you are doing. &'No pre-compiled
13024 distributions of Exim should ever make this option available.'&
13025
13026 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
13027 updated files' data to be written to disc before continuing. Unexpected events
13028 such as crashes and power outages may cause data to be lost or scrambled.
13029 Here be Dragons. &*Beware.*&
13030
13031
13032 .option disable_ipv6 main boolean false
13033 .cindex "IPv6" "disabling"
13034 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
13035 activities take place. AAAA records are never looked up, and any IPv6 addresses
13036 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
13037 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
13038 to handle IPv6 literal addresses.
13039
13040
13041 .option dns_again_means_nonexist main "domain list&!!" unset
13042 .cindex "DNS" "&""try again""& response; overriding"
13043 DNS lookups give a &"try again"& response for the DNS errors
13044 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
13045 keep trying to deliver a message, or to give repeated temporary errors to
13046 incoming mail. Sometimes the effect is caused by a badly set up name server and
13047 may persist for a long time. If a domain which exhibits this problem matches
13048 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
13049 This option should be used with care. You can make it apply to reverse lookups
13050 by a setting such as this:
13051 .code
13052 dns_again_means_nonexist = *.in-addr.arpa
13053 .endd
13054 This option applies to all DNS lookups that Exim does. It also applies when the
13055 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
13056 since these are most likely to be caused by DNS lookup problems. The
13057 &(dnslookup)& router has some options of its own for controlling what happens
13058 when lookups for MX or SRV records give temporary errors. These more specific
13059 options are applied after this global option.
13060
13061 .option dns_check_names_pattern main string "see below"
13062 .cindex "DNS" "pre-check of name syntax"
13063 When this option is set to a non-empty string, it causes Exim to check domain
13064 names for characters that are not allowed in host names before handing them to
13065 the DNS resolver, because some resolvers give temporary errors for names that
13066 contain unusual characters. If a domain name contains any unwanted characters,
13067 a &"not found"& result is forced, and the resolver is not called. The check is
13068 done by matching the domain name against a regular expression, which is the
13069 value of this option. The default pattern is
13070 .code
13071 dns_check_names_pattern = \
13072 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
13073 .endd
13074 which permits only letters, digits, slashes, and hyphens in components, but
13075 they must start and end with a letter or digit. Slashes are not, in fact,
13076 permitted in host names, but they are found in certain NS records (which can be
13077 accessed in Exim by using a &%dnsdb%& lookup). If you set
13078 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
13079 empty string.
13080
13081 .option dns_csa_search_limit main integer 5
13082 This option controls the depth of parental searching for CSA SRV records in the
13083 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
13084
13085 .option dns_csa_use_reverse main boolean true
13086 This option controls whether or not an IP address, given as a CSA domain, is
13087 reversed and looked up in the reverse DNS, as described in more detail in
13088 section &<<SECTverifyCSA>>&.
13089
13090 .option dns_ipv4_lookup main "domain list&!!" unset
13091 .cindex "IPv6" "DNS lookup for AAAA records"
13092 .cindex "DNS" "IPv6 lookup for AAAA records"
13093 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
13094 looks for IPv6 address records (AAAA records) as well as IPv4 address records
13095 (A records) when trying to find IP addresses for hosts, unless the host's
13096 domain matches this list.
13097
13098 This is a fudge to help with name servers that give big delays or otherwise do
13099 not work for the AAAA record type. In due course, when the world's name
13100 servers have all been upgraded, there should be no need for this option.
13101
13102
13103 .option dns_retrans main time 0s
13104 .cindex "DNS" "resolver options"
13105 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
13106 retransmission and retry parameters for DNS lookups. Values of zero (the
13107 defaults) leave the system default settings unchanged. The first value is the
13108 time between retries, and the second is the number of retries. It isn't
13109 totally clear exactly how these settings affect the total time a DNS lookup may
13110 take. I haven't found any documentation about timeouts on DNS lookups; these
13111 parameter values are available in the external resolver interface structure,
13112 but nowhere does it seem to describe how they are used or what you might want
13113 to set in them.
13114
13115
13116 .option dns_retry main integer 0
13117 See &%dns_retrans%& above.
13118
13119
13120 .option drop_cr main boolean false
13121 This is an obsolete option that is now a no-op. It used to affect the way Exim
13122 handled CR and LF characters in incoming messages. What happens now is
13123 described in section &<<SECTlineendings>>&.
13124
13125 .option dsn_from main "string&!!" "see below"
13126 .cindex "&'From:'& header line" "in bounces"
13127 .cindex "bounce messages" "&'From:'& line, specifying"
13128 This option can be used to vary the contents of &'From:'& header lines in
13129 bounces and other automatically generated messages (&"Delivery Status
13130 Notifications"& &-- hence the name of the option). The default setting is:
13131 .code
13132 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
13133 .endd
13134 The value is expanded every time it is needed. If the expansion fails, a
13135 panic is logged, and the default value is used.
13136
13137 .option envelope_to_remove main boolean true
13138 .cindex "&'Envelope-to:'& header line"
13139 Exim's transports have an option for adding an &'Envelope-to:'& header to a
13140 message when it is delivered, in exactly the same way as &'Return-path:'& is
13141 handled. &'Envelope-to:'& records the original recipient address from the
13142 messages's envelope that caused the delivery to happen. Such headers should not
13143 be present in incoming messages, and this option causes them to be removed at
13144 the time the message is received, to avoid any problems that might occur when a
13145 delivered message is subsequently sent on to some other recipient.
13146
13147
13148 .option errors_copy main "string list&!!" unset
13149 .cindex "bounce message" "copy to other address"
13150 .cindex "copy of bounce message"
13151 Setting this option causes Exim to send bcc copies of bounce messages that it
13152 generates to other addresses. &*Note*&: This does not apply to bounce messages
13153 coming from elsewhere. The value of the option is a colon-separated list of
13154 items. Each item consists of a pattern, terminated by white space, followed by
13155 a comma-separated list of email addresses. If a pattern contains spaces, it
13156 must be enclosed in double quotes.
13157
13158 Each pattern is processed in the same way as a single item in an address list
13159 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
13160 the bounce message, the message is copied to the addresses on the list. The
13161 items are scanned in order, and once a matching one is found, no further items
13162 are examined. For example:
13163 .code
13164 errors_copy = spqr@mydomain postmaster@mydomain.example :\
13165 rqps@mydomain hostmaster@mydomain.example,\
13166 postmaster@mydomain.example
13167 .endd
13168 .vindex "&$domain$&"
13169 .vindex "&$local_part$&"
13170 The address list is expanded before use. The expansion variables &$local_part$&
13171 and &$domain$& are set from the original recipient of the error message, and if
13172 there was any wildcard matching in the pattern, the expansion
13173 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
13174 variables &$0$&, &$1$&, etc. are set in the normal way.
13175
13176
13177 .option errors_reply_to main string unset
13178 .cindex "bounce message" "&'Reply-to:'& in"
13179 By default, Exim's bounce and delivery warning messages contain the header line
13180 .display
13181 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
13182 .endd
13183 .oindex &%quota_warn_message%&
13184 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
13185 A warning message that is generated by the &%quota_warn_message%& option in an
13186 &(appendfile)& transport may contain its own &'From:'& header line that
13187 overrides the default.
13188
13189 Experience shows that people reply to bounce messages. If the
13190 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
13191 and warning messages. For example:
13192 .code
13193 errors_reply_to = postmaster@my.domain.example
13194 .endd
13195 The value of the option is not expanded. It must specify a valid RFC 2822
13196 address. However, if a warning message that is generated by the
13197 &%quota_warn_message%& option in an &(appendfile)& transport contain its
13198 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
13199 not used.
13200
13201
13202 .option exim_group main string "compile-time configured"
13203 .cindex "gid (group id)" "Exim's own"
13204 .cindex "Exim group"
13205 This option changes the gid under which Exim runs when it gives up root
13206 privilege. The default value is compiled into the binary. The value of this
13207 option is used only when &%exim_user%& is also set. Unless it consists entirely
13208 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
13209 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
13210 security issues.
13211
13212
13213 .option exim_path main string "see below"
13214 .cindex "Exim binary, path name"
13215 This option specifies the path name of the Exim binary, which is used when Exim
13216 needs to re-exec itself. The default is set up to point to the file &'exim'& in
13217 the directory configured at compile time by the BIN_DIRECTORY setting. It
13218 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
13219 other place.
13220 &*Warning*&: Do not use a macro to define the value of this option, because
13221 you will break those Exim utilities that scan the configuration file to find
13222 where the binary is. (They then use the &%-bP%& option to extract option
13223 settings such as the value of &%spool_directory%&.)
13224
13225
13226 .option exim_user main string "compile-time configured"
13227 .cindex "uid (user id)" "Exim's own"
13228 .cindex "Exim user"
13229 This option changes the uid under which Exim runs when it gives up root
13230 privilege. The default value is compiled into the binary. Ownership of the run
13231 time configuration file and the use of the &%-C%& and &%-D%& command line
13232 options is checked against the values in the binary, not what is set here.
13233
13234 Unless it consists entirely of digits, the string is looked up using
13235 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
13236 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
13237 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
13238
13239
13240 .option extra_local_interfaces main "string list" unset
13241 This option defines network interfaces that are to be considered local when
13242 routing, but which are not used for listening by the daemon. See section
13243 &<<SECTreclocipadd>>& for details.
13244
13245
13246 . Allow this long option name to split; give it unsplit as a fifth argument
13247 . for the automatic .oindex that is generated by .option.
13248
13249 .option "extract_addresses_remove_ &~&~arguments" main boolean true &&&
13250 extract_addresses_remove_arguments
13251 .oindex "&%-t%&"
13252 .cindex "command line" "addresses with &%-t%&"
13253 .cindex "Sendmail compatibility" "&%-t%& option"
13254 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
13255 are present on the command line when the &%-t%& option is used to build an
13256 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
13257 line addresses are removed from the recipients list. This is also how Smail
13258 behaves. However, other Sendmail documentation (the O'Reilly book) states that
13259 command line addresses are added to those obtained from the header lines. When
13260 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
13261 argument headers. If it is set false, Exim adds rather than removes argument
13262 addresses.
13263
13264
13265 .option finduser_retries main integer 0
13266 .cindex "NIS, retrying user lookups"
13267 On systems running NIS or other schemes in which user and group information is
13268 distributed from a remote system, there can be times when &[getpwnam()]& and
13269 related functions fail, even when given valid data, because things time out.
13270 Unfortunately these failures cannot be distinguished from genuine &"not found"&
13271 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
13272 many extra times to find a user or a group, waiting for one second between
13273 retries.
13274
13275 .cindex "&_/etc/passwd_&" "multiple reading of"
13276 You should not set this option greater than zero if your user information is in
13277 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
13278 search the file multiple times for non-existent users, and also cause delay.
13279
13280
13281
13282 .option freeze_tell main "string list, comma separated" unset
13283 .cindex "freezing messages" "sending a message when freezing"
13284 On encountering certain errors, or when configured to do so in a system filter,
13285 ACL, or special router, Exim freezes a message. This means that no further
13286 delivery attempts take place until an administrator thaws the message, or the
13287 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
13288 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
13289 warning message whenever it freezes something, unless the message it is
13290 freezing is a locally-generated bounce message. (Without this exception there
13291 is the possibility of looping.) The warning message is sent to the addresses
13292 supplied as the comma-separated value of this option. If several of the
13293 message's addresses cause freezing, only a single message is sent. If the
13294 freezing was automatic, the reason(s) for freezing can be found in the message
13295 log. If you configure freezing in a filter or ACL, you must arrange for any
13296 logging that you require.
13297
13298
13299 .option gecos_name main string&!! unset
13300 .cindex "HP-UX"
13301 .cindex "&""gecos""& field, parsing"
13302 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
13303 password file to hold other information in addition to users' real names. Exim
13304 looks up this field for use when it is creating &'Sender:'& or &'From:'&
13305 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
13306 of the field are used unchanged, except that, if an ampersand is encountered,
13307 it is replaced by the user's login name with the first character forced to
13308 upper case, since this is a convention that is observed on many systems.
13309
13310 When these options are set, &%gecos_pattern%& is treated as a regular
13311 expression that is to be applied to the field (again with && replaced by the
13312 login name), and if it matches, &%gecos_name%& is expanded and used as the
13313 user's name.
13314
13315 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
13316 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
13317 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
13318 name terminates at the first comma, the following can be used:
13319 .code
13320 gecos_pattern = ([^,]*)
13321 gecos_name = $1
13322 .endd
13323
13324 .option gecos_pattern main string unset
13325 See &%gecos_name%& above.
13326
13327
13328 .option gnutls_require_kx main string unset
13329 This option controls the key exchange mechanisms when GnuTLS is used in an Exim
13330 server. For details, see section &<<SECTreqciphgnu>>&.
13331
13332 .option gnutls_require_mac main string unset
13333 This option controls the MAC algorithms when GnuTLS is used in an Exim
13334 server. For details, see section &<<SECTreqciphgnu>>&.
13335
13336 .option gnutls_require_protocols main string unset
13337 This option controls the protocols when GnuTLS is used in an Exim
13338 server. For details, see section &<<SECTreqciphgnu>>&.
13339
13340
13341 .option headers_charset main string "see below"
13342 This option sets a default character set for translating from encoded MIME
13343 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
13344 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
13345 ultimate default is ISO-8859-1. For more details see the description of header
13346 insertions in section &<<SECTexpansionitems>>&.
13347
13348
13349
13350 .option header_maxsize main integer "see below"
13351 .cindex "header section" "maximum size of"
13352 .cindex "limit" "size of message header section"
13353 This option controls the overall maximum size of a message's header
13354 section. The default is the value of HEADER_MAXSIZE in
13355 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
13356 sections are rejected.
13357
13358
13359 .option header_line_maxsize main integer 0
13360 .cindex "header lines" "maximum size of"
13361 .cindex "limit" "size of one header line"
13362 This option limits the length of any individual header line in a message, after
13363 all the continuations have been joined together. Messages with individual
13364 header lines that are longer than the limit are rejected. The default value of
13365 zero means &"no limit"&.
13366
13367
13368
13369
13370 .option helo_accept_junk_hosts main "host list&!!" unset
13371 .cindex "HELO" "accepting junk data"
13372 .cindex "EHLO" "accepting junk data"
13373 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
13374 mail, and gives an error response for invalid data. Unfortunately, there are
13375 some SMTP clients that send syntactic junk. They can be accommodated by setting
13376 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
13377 if you want to do semantic checking.
13378 See also &%helo_allow_chars%& for a way of extending the permitted character
13379 set.
13380
13381
13382 .option helo_allow_chars main string unset
13383 .cindex "HELO" "underscores in"
13384 .cindex "EHLO" "underscores in"
13385 .cindex "underscore in EHLO/HELO"
13386 This option can be set to a string of rogue characters that are permitted in
13387 all EHLO and HELO names in addition to the standard letters, digits,
13388 hyphens, and dots. If you really must allow underscores, you can set
13389 .code
13390 helo_allow_chars = _
13391 .endd
13392 Note that the value is one string, not a list.
13393
13394
13395 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
13396 .cindex "HELO" "forcing reverse lookup"
13397 .cindex "EHLO" "forcing reverse lookup"
13398 If the domain given by a client in a HELO or EHLO command matches this
13399 list, a reverse lookup is done in order to establish the host's true name. The
13400 default forces a lookup if the client host gives the server's name or any of
13401 its IP addresses (in brackets), something that broken clients have been seen to
13402 do.
13403
13404
13405 .option helo_try_verify_hosts main "host list&!!" unset
13406 .cindex "HELO verifying" "optional"
13407 .cindex "EHLO" "verifying, optional"
13408 By default, Exim just checks the syntax of HELO and EHLO commands (see
13409 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
13410 to do more extensive checking of the data supplied by these commands. The ACL
13411 condition &`verify`& &`=`& &`helo`& is provided to make this possible.
13412 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
13413 to force the check to occur. From release 4.53 onwards, this is no longer
13414 necessary. If the check has not been done before &`verify`& &`=`& &`helo`& is
13415 encountered, it is done at that time. Consequently, this option is obsolete.
13416 Its specification is retained here for backwards compatibility.
13417
13418 When an EHLO or HELO command is received, if the calling host matches
13419 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
13420 EHLO command either:
13421
13422 .ilist
13423 is an IP literal matching the calling address of the host, or
13424 .next
13425 .cindex "DNS" "reverse lookup"
13426 .cindex "reverse DNS lookup"
13427 matches the host name that Exim obtains by doing a reverse lookup of the
13428 calling host address, or
13429 .next
13430 when looked up using &[gethostbyname()]& (or &[getipnodebyname()]& when
13431 available) yields the calling host address.
13432 .endlist
13433
13434 However, the EHLO or HELO command is not rejected if any of the checks
13435 fail. Processing continues, but the result of the check is remembered, and can
13436 be detected later in an ACL by the &`verify`& &`=`& &`helo`& condition.
13437
13438 .option helo_verify_hosts main "host list&!!" unset
13439 .cindex "HELO verifying" "mandatory"
13440 .cindex "EHLO" "verifying, mandatory"
13441 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
13442 backwards compatibility. For hosts that match this option, Exim checks the host
13443 name given in the HELO or EHLO in the same way as for
13444 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
13445 rejected with a 550 error, and entries are written to the main and reject logs.
13446 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
13447 error.
13448
13449 .option hold_domains main "domain list&!!" unset
13450 .cindex "domain" "delaying delivery"
13451 .cindex "delivery" "delaying certain domains"
13452 This option allows mail for particular domains to be held on the queue
13453 manually. The option is overridden if a message delivery is forced with the
13454 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
13455 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
13456 item in &%hold_domains%&, no routing or delivery for that address is done, and
13457 it is deferred every time the message is looked at.
13458
13459 This option is intended as a temporary operational measure for delaying the
13460 delivery of mail while some problem is being sorted out, or some new
13461 configuration tested. If you just want to delay the processing of some
13462 domains until a queue run occurs, you should use &%queue_domains%& or
13463 &%queue_smtp_domains%&, not &%hold_domains%&.
13464
13465 A setting of &%hold_domains%& does not override Exim's code for removing
13466 messages from the queue if they have been there longer than the longest retry
13467 time in any retry rule. If you want to hold messages for longer than the normal
13468 retry times, insert a dummy retry rule with a long retry time.
13469
13470
13471 .option host_lookup main "host list&!!" unset
13472 .cindex "host name" "lookup, forcing"
13473 Exim does not look up the name of a calling host from its IP address unless it
13474 is required to compare against some host list, or the host matches
13475 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
13476 option (which normally contains IP addresses rather than host names). The
13477 default configuration file contains
13478 .code
13479 host_lookup = *
13480 .endd
13481 which causes a lookup to happen for all hosts. If the expense of these lookups
13482 is felt to be too great, the setting can be changed or removed.
13483
13484 After a successful reverse lookup, Exim does a forward lookup on the name it
13485 has obtained, to verify that it yields the IP address that it started with. If
13486 this check fails, Exim behaves as if the name lookup failed.
13487
13488 .vindex "&$host_lookup_failed$&"
13489 .vindex "&$sender_host_name$&"
13490 After any kind of failure, the host name (in &$sender_host_name$&) remains
13491 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
13492 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and &`verify`& &`=`&
13493 &`reverse_host_lookup`& in ACLs.
13494
13495
13496 .option host_lookup_order main "string list" &`bydns:byaddr`&
13497 This option specifies the order of different lookup methods when Exim is trying
13498 to find a host name from an IP address. The default is to do a DNS lookup
13499 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
13500 if that fails. You can change the order of these lookups, or omit one entirely,
13501 if you want.
13502
13503 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
13504 multiple PTR records in the DNS and the IP address is not listed in
13505 &_/etc/hosts_&. Different operating systems give different results in this
13506 case. That is why the default tries a DNS lookup first.
13507
13508
13509
13510 .option host_reject_connection main "host list&!!" unset
13511 .cindex "host" "rejecting connections from"
13512 If this option is set, incoming SMTP calls from the hosts listed are rejected
13513 as soon as the connection is made.
13514 This option is obsolete, and retained only for backward compatibility, because
13515 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
13516 connections immediately.
13517
13518 The ability to give an immediate rejection (either by this option or using an
13519 ACL) is provided for use in unusual cases. Many hosts will just try again,
13520 sometimes without much delay. Normally, it is better to use an ACL to reject
13521 incoming messages at a later stage, such as after RCPT commands. See
13522 chapter &<<CHAPACL>>&.
13523
13524
13525 .option hosts_connection_nolog main "host list&!!" unset
13526 .cindex "host" "not logging connections from"
13527 This option defines a list of hosts for which connection logging does not
13528 happen, even though the &%smtp_connection%& log selector is set. For example,
13529 you might want not to log SMTP connections from local processes, or from
13530 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
13531 the daemon; you should therefore strive to restrict its value to a short inline
13532 list of IP addresses and networks. To disable logging SMTP connections from
13533 local processes, you must create a host list with an empty item. For example:
13534 .code
13535 hosts_connection_nolog = :
13536 .endd
13537 If the &%smtp_connection%& log selector is not set, this option has no effect.
13538
13539
13540
13541 .option hosts_treat_as_local main "domain list&!!" unset
13542 .cindex "local host" "domains treated as"
13543 .cindex "host" "treated as local"
13544 If this option is set, any host names that match the domain list are treated as
13545 if they were the local host when Exim is scanning host lists obtained from MX
13546 records
13547 or other sources. Note that the value of this option is a domain list, not a
13548 host list, because it is always used to check host names, not IP addresses.
13549
13550 This option also applies when Exim is matching the special items
13551 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
13552 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
13553 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
13554 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
13555 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
13556 interfaces and recognizing the local host.
13557
13558
13559 .option ibase_servers main "string list" unset
13560 .cindex "InterBase" "server list"
13561 This option provides a list of InterBase servers and associated connection data,
13562 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
13563 The option is available only if Exim has been built with InterBase support.
13564
13565
13566
13567 .option ignore_bounce_errors_after main time 10w
13568 .cindex "bounce message" "discarding"
13569 .cindex "discarding bounce message"
13570 This option affects the processing of bounce messages that cannot be delivered,
13571 that is, those that suffer a permanent delivery failure. (Bounce messages that
13572 suffer temporary delivery failures are of course retried in the usual way.)
13573
13574 After a permanent delivery failure, bounce messages are frozen,
13575 because there is no sender to whom they can be returned. When a frozen bounce
13576 message has been on the queue for more than the given time, it is unfrozen at
13577 the next queue run, and a further delivery is attempted. If delivery fails
13578 again, the bounce message is discarded. This makes it possible to keep failed
13579 bounce messages around for a shorter time than the normal maximum retry time
13580 for frozen messages. For example,
13581 .code
13582 ignore_bounce_errors_after = 12h
13583 .endd
13584 retries failed bounce message deliveries after 12 hours, discarding any further
13585 failures. If the value of this option is set to a zero time period, bounce
13586 failures are discarded immediately. Setting a very long time (as in the default
13587 value) has the effect of disabling this option. For ways of automatically
13588 dealing with other kinds of frozen message, see &%auto_thaw%& and
13589 &%timeout_frozen_after%&.
13590
13591
13592 .option ignore_fromline_hosts main "host list&!!" unset
13593 .cindex "&""From""& line"
13594 .cindex "UUCP" "&""From""& line"
13595 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
13596 the headers of a message. By default this is treated as the start of the
13597 message's body, which means that any following headers are not recognized as
13598 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
13599 match those hosts that insist on sending it. If the sender is actually a local
13600 process rather than a remote host, and is using &%-bs%& to inject the messages,
13601 &%ignore_fromline_local%& must be set to achieve this effect.
13602
13603
13604 .option ignore_fromline_local main boolean false
13605 See &%ignore_fromline_hosts%& above.
13606
13607
13608 .option keep_malformed main time 4d
13609 This option specifies the length of time to keep messages whose spool files
13610 have been corrupted in some way. This should, of course, never happen. At the
13611 next attempt to deliver such a message, it gets removed. The incident is
13612 logged.
13613
13614
13615 .option ldap_default_servers main "string list" unset
13616 .cindex "LDAP" "default servers"
13617 This option provides a list of LDAP servers which are tried in turn when an
13618 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
13619 details of LDAP queries. This option is available only when Exim has been built
13620 with LDAP support.
13621
13622
13623 .option ldap_version main integer unset
13624 .cindex "LDAP" "protocol version, forcing"
13625 This option can be used to force Exim to set a specific protocol version for
13626 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
13627 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
13628 the LDAP headers; otherwise it is 2. This option is available only when Exim
13629 has been built with LDAP support.
13630
13631
13632
13633 .option local_from_check main boolean true
13634 .cindex "&'Sender:'& header line" "disabling addition of"
13635 .cindex "&'From:'& header line" "disabling checking of"
13636 When a message is submitted locally (that is, not over a TCP/IP connection) by
13637 an untrusted user, Exim removes any existing &'Sender:'& header line, and
13638 checks that the &'From:'& header line matches the login of the calling user and
13639 the domain specified by &%qualify_domain%&.
13640
13641 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
13642 locally submitted message is automatically qualified by Exim, unless the
13643 &%-bnq%& command line option is used.
13644
13645 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
13646 on the local part. If the &'From:'& header line does not match, Exim adds a
13647 &'Sender:'& header with an address constructed from the calling user's login
13648 and the default qualify domain.
13649
13650 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
13651 and no &'Sender:'& header is ever added. If, in addition, you want to retain
13652 &'Sender:'& header lines supplied by untrusted users, you must also set
13653 &%local_sender_retain%& to be true.
13654
13655 .cindex "envelope sender"
13656 These options affect only the header lines in the message. The envelope sender
13657 is still forced to be the login id at the qualify domain unless
13658 &%untrusted_set_sender%& permits the user to supply an envelope sender.
13659
13660 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
13661 request similar header line checking. See section &<<SECTthesenhea>>&, which
13662 has more details about &'Sender:'& processing.
13663
13664
13665
13666
13667 .option local_from_prefix main string unset
13668 When Exim checks the &'From:'& header line of locally submitted messages for
13669 matching the login id (see &%local_from_check%& above), it can be configured to
13670 ignore certain prefixes and suffixes in the local part of the address. This is
13671 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
13672 appropriate lists, in the same form as the &%local_part_prefix%& and
13673 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
13674 example, if
13675 .code
13676 local_from_prefix = *-
13677 .endd
13678 is set, a &'From:'& line containing
13679 .code
13680 From: anything-user@your.domain.example
13681 .endd
13682 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
13683 matches the actual sender address that is constructed from the login name and
13684 qualify domain.
13685
13686
13687 .option local_from_suffix main string unset
13688 See &%local_from_prefix%& above.
13689
13690
13691 .option local_interfaces main "string list" "see below"
13692 This option controls which network interfaces are used by the daemon for
13693 listening; they are also used to identify the local host when routing. Chapter
13694 &<<CHAPinterfaces>>& contains a full description of this option and the related
13695 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
13696 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
13697 &%local_interfaces%& is
13698 .code
13699 local_interfaces = 0.0.0.0
13700 .endd
13701 when Exim is built without IPv6 support; otherwise it is
13702 .code
13703 local_interfaces = <; ::0 ; 0.0.0.0
13704 .endd
13705
13706 .option local_scan_timeout main time 5m
13707 .cindex "timeout" "for &[local_scan()]& function"
13708 .cindex "&[local_scan()]& function" "timeout"
13709 This timeout applies to the &[local_scan()]& function (see chapter
13710 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
13711 the incoming message is rejected with a temporary error if it is an SMTP
13712 message. For a non-SMTP message, the message is dropped and Exim ends with a
13713 non-zero code. The incident is logged on the main and reject logs.
13714
13715
13716
13717 .option local_sender_retain main boolean false
13718 .cindex "&'Sender:'& header line" "retaining from local submission"
13719 When a message is submitted locally (that is, not over a TCP/IP connection) by
13720 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
13721 do not want this to happen, you must set &%local_sender_retain%&, and you must
13722 also set &%local_from_check%& to be false (Exim will complain if you do not).
13723 See also the ACL modifier &`control = suppress_local_fixups`&. Section
13724 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
13725
13726
13727
13728
13729 .option localhost_number main string&!! unset
13730 .cindex "host" "locally unique number for"
13731 .cindex "message ids" "with multiple hosts"
13732 .vindex "&$localhost_number$&"
13733 Exim's message ids are normally unique only within the local host. If
13734 uniqueness among a set of hosts is required, each host must set a different
13735 value for the &%localhost_number%& option. The string is expanded immediately
13736 after reading the configuration file (so that a number can be computed from the
13737 host name, for example) and the result of the expansion must be a number in the
13738 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
13739 systems). This is available in subsequent string expansions via the variable
13740 &$localhost_number$&. When &%localhost_number is set%&, the final two
13741 characters of the message id, instead of just being a fractional part of the
13742 time, are computed from the time and the local host number as described in
13743 section &<<SECTmessiden>>&.
13744
13745
13746
13747 .option log_file_path main "string list&!!" "set at compile time"
13748 .cindex "log" "file path for"
13749 This option sets the path which is used to determine the names of Exim's log
13750 files, or indicates that logging is to be to syslog, or both. It is expanded
13751 when Exim is entered, so it can, for example, contain a reference to the host
13752 name. If no specific path is set for the log files at compile or run time, they
13753 are written in a sub-directory called &_log_& in Exim's spool directory.
13754 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
13755 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
13756 used. If this string is fixed at your installation (contains no expansion
13757 variables) it is recommended that you do not set this option in the
13758 configuration file, but instead supply the path using LOG_FILE_PATH in
13759 &_Local/Makefile_& so that it is available to Exim for logging errors detected
13760 early on &-- in particular, failure to read the configuration file.
13761
13762
13763 .option log_selector main string unset
13764 .cindex "log" "selectors"
13765 This option can be used to reduce or increase the number of things that Exim
13766 writes to its log files. Its argument is made up of names preceded by plus or
13767 minus characters. For example:
13768 .code
13769 log_selector = +arguments -retry_defer
13770 .endd
13771 A list of possible names and what they control is given in the chapter on
13772 logging, in section &<<SECTlogselector>>&.
13773
13774
13775 .option log_timezone main boolean false
13776 .cindex "log" "timezone for entries"
13777 .vindex "&$tod_log$&"
13778 .vindex "&$tod_zone$&"
13779 By default, the timestamps on log lines are in local time without the
13780 timezone. This means that if your timezone changes twice a year, the timestamps
13781 in log lines are ambiguous for an hour when the clocks go back. One way of
13782 avoiding this problem is to set the timezone to UTC. An alternative is to set
13783 &%log_timezone%& true. This turns on the addition of the timezone offset to
13784 timestamps in log lines. Turning on this option can add quite a lot to the size
13785 of log files because each line is extended by 6 characters. Note that the
13786 &$tod_log$& variable contains the log timestamp without the zone, but there is
13787 another variable called &$tod_zone$& that contains just the timezone offset.
13788
13789
13790 .option lookup_open_max main integer 25
13791 .cindex "too many open files"
13792 .cindex "open files, too many"
13793 .cindex "file" "too many open"
13794 .cindex "lookup" "maximum open files"
13795 .cindex "limit" "open files for lookups"
13796 This option limits the number of simultaneously open files for single-key
13797 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
13798 Exim normally keeps these files open during routing, because often the same
13799 file is required several times. If the limit is reached, Exim closes the least
13800 recently used file. Note that if you are using the &'ndbm'& library, it
13801 actually opens two files for each logical DBM database, though it still counts
13802 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
13803 open files"& errors with NDBM, you need to reduce the value of
13804 &%lookup_open_max%&.
13805
13806
13807 .option max_username_length main integer 0
13808 .cindex "length of login name"
13809 .cindex "user name" "maximum length"
13810 .cindex "limit" "user name length"
13811 Some operating systems are broken in that they truncate long arguments to
13812 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
13813 this option is set greater than zero, any attempt to call &[getpwnam()]& with
13814 an argument that is longer behaves as if &[getpwnam()]& failed.
13815
13816
13817 .option message_body_newlines main bool false
13818 .cindex "message body" "newlines in variables"
13819 .cindex "newline" "in message body variables"
13820 .vindex "&$message_body$&"
13821 .vindex "&$message_body_end$&"
13822 By default, newlines in the message body are replaced by spaces when setting
13823 the &$message_body$& and &$message_body_end$& expansion variables. If this
13824 option is set true, this no longer happens.
13825
13826
13827 .option message_body_visible main integer 500
13828 .cindex "body of message" "visible size"
13829 .cindex "message body" "visible size"
13830 .vindex "&$message_body$&"
13831 .vindex "&$message_body_end$&"
13832 This option specifies how much of a message's body is to be included in the
13833 &$message_body$& and &$message_body_end$& expansion variables.
13834
13835
13836 .option message_id_header_domain main string&!! unset
13837 .cindex "&'Message-ID:'& header line"
13838 If this option is set, the string is expanded and used as the right hand side
13839 (domain) of the &'Message-ID:'& header that Exim creates if a
13840 locally-originated incoming message does not have one. &"Locally-originated"&
13841 means &"not received over TCP/IP."&
13842 Otherwise, the primary host name is used.
13843 Only letters, digits, dot and hyphen are accepted; any other characters are
13844 replaced by hyphens. If the expansion is forced to fail, or if the result is an
13845 empty string, the option is ignored.
13846
13847
13848 .option message_id_header_text main string&!! unset
13849 If this variable is set, the string is expanded and used to augment the text of
13850 the &'Message-id:'& header that Exim creates if a locally-originated incoming
13851 message does not have one. The text of this header is required by RFC 2822 to
13852 take the form of an address. By default, Exim uses its internal message id as
13853 the local part, and the primary host name as the domain. If this option is set,
13854 it is expanded, and provided the expansion is not forced to fail, and does not
13855 yield an empty string, the result is inserted into the header immediately
13856 before the @, separated from the internal message id by a dot. Any characters
13857 that are illegal in an address are automatically converted into hyphens. This
13858 means that variables such as &$tod_log$& can be used, because the spaces and
13859 colons will become hyphens.
13860
13861
13862 .option message_logs main boolean true
13863 .cindex "message logs" "disabling"
13864 .cindex "log" "message log; disabling"
13865 If this option is turned off, per-message log files are not created in the
13866 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
13867 Exim, by reducing the number of files involved in handling a message from a
13868 minimum of four (header spool file, body spool file, delivery journal, and
13869 per-message log) to three. The other major I/O activity is Exim's main log,
13870 which is not affected by this option.
13871
13872
13873 .option message_size_limit main string&!! 50M
13874 .cindex "message" "size limit"
13875 .cindex "limit" "message size"
13876 .cindex "size" "of message, limit"
13877 This option limits the maximum size of message that Exim will process. The
13878 value is expanded for each incoming connection so, for example, it can be made
13879 to depend on the IP address of the remote host for messages arriving via
13880 TCP/IP. After expansion, the value must be a sequence of decimal digits,
13881 optionally followed by K or M.
13882
13883 &*Note*&: This limit cannot be made to depend on a message's sender or any
13884 other properties of an individual message, because it has to be advertised in
13885 the server's response to EHLO. String expansion failure causes a temporary
13886 error. A value of zero means no limit, but its use is not recommended. See also
13887 &%bounce_return_size_limit%&.
13888
13889 Incoming SMTP messages are failed with a 552 error if the limit is
13890 exceeded; locally-generated messages either get a stderr message or a delivery
13891 failure message to the sender, depending on the &%-oe%& setting. Rejection of
13892 an oversized message is logged in both the main and the reject logs. See also
13893 the generic transport option &%message_size_limit%&, which limits the size of
13894 message that an individual transport can process.
13895
13896
13897 .option move_frozen_messages main boolean false
13898 .cindex "frozen messages" "moving"
13899 This option, which is available only if Exim has been built with the setting
13900 .code
13901 SUPPORT_MOVE_FROZEN_MESSAGES=yes
13902 .endd
13903 in &_Local/Makefile_&, causes frozen messages and their message logs to be
13904 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
13905 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
13906 standard utilities for handling such moved messages, and they do not show up in
13907 lists generated by &%-bp%& or by the Exim monitor.
13908
13909
13910 .option mua_wrapper main boolean false
13911 Setting this option true causes Exim to run in a very restrictive mode in which
13912 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
13913 contains a full description of this facility.
13914
13915
13916
13917 .option mysql_servers main "string list" unset
13918 .cindex "MySQL" "server list"
13919 This option provides a list of MySQL servers and associated connection data, to
13920 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
13921 option is available only if Exim has been built with MySQL support.
13922
13923
13924 .option never_users main "string list&!!" unset
13925 This option is expanded just once, at the start of Exim's processing. Local
13926 message deliveries are normally run in processes that are setuid to the
13927 recipient, and remote deliveries are normally run under Exim's own uid and gid.
13928 It is usually desirable to prevent any deliveries from running as root, as a
13929 safety precaution.
13930
13931 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
13932 list of users that must not be used for local deliveries. This list is fixed in
13933 the binary and cannot be overridden by the configuration file. By default, it
13934 contains just the single user name &"root"&. The &%never_users%& runtime option
13935 can be used to add more users to the fixed list.
13936
13937 If a message is to be delivered as one of the users on the fixed list or the
13938 &%never_users%& list, an error occurs, and delivery is deferred. A common
13939 example is
13940 .code
13941 never_users = root:daemon:bin
13942 .endd
13943 Including root is redundant if it is also on the fixed list, but it does no
13944 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
13945 transport driver.
13946
13947
13948 .option oracle_servers main "string list" unset
13949 .cindex "Oracle" "server list"
13950 This option provides a list of Oracle servers and associated connection data,
13951 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
13952 The option is available only if Exim has been built with Oracle support.
13953
13954
13955 .option percent_hack_domains main "domain list&!!" unset
13956 .cindex "&""percent hack""&"
13957 .cindex "source routing" "in email address"
13958 .cindex "address" "source-routed"
13959 The &"percent hack"& is the convention whereby a local part containing a
13960 percent sign is re-interpreted as a new email address, with the percent
13961 replaced by @. This is sometimes called &"source routing"&, though that term is
13962 also applied to RFC 2822 addresses that begin with an @ character. If this
13963 option is set, Exim implements the percent facility for those domains listed,
13964 but no others. This happens before an incoming SMTP address is tested against
13965 an ACL.
13966
13967 &*Warning*&: The &"percent hack"& has often been abused by people who are
13968 trying to get round relaying restrictions. For this reason, it is best avoided
13969 if at all possible. Unfortunately, a number of less security-conscious MTAs
13970 implement it unconditionally. If you are running Exim on a gateway host, and
13971 routing mail through to internal MTAs without processing the local parts, it is
13972 a good idea to reject recipient addresses with percent characters in their
13973 local parts. Exim's default configuration does this.
13974
13975
13976 .option perl_at_start main boolean false
13977 This option is available only when Exim is built with an embedded Perl
13978 interpreter. See chapter &<<CHAPperl>>& for details of its use.
13979
13980
13981 .option perl_startup main string unset
13982 This option is available only when Exim is built with an embedded Perl
13983 interpreter. See chapter &<<CHAPperl>>& for details of its use.
13984
13985
13986 .option pgsql_servers main "string list" unset
13987 .cindex "PostgreSQL lookup type" "server list"
13988 This option provides a list of PostgreSQL servers and associated connection
13989 data, to be used in conjunction with &(pgsql)& lookups (see section
13990 &<<SECID72>>&). The option is available only if Exim has been built with
13991 PostgreSQL support.
13992
13993
13994 .option pid_file_path main string&!! "set at compile time"
13995 .cindex "daemon" "pid file path"
13996 .cindex "pid file, path for"
13997 This option sets the name of the file to which the Exim daemon writes its
13998 process id. The string is expanded, so it can contain, for example, references
13999 to the host name:
14000 .code
14001 pid_file_path = /var/log/$primary_hostname/exim.pid
14002 .endd
14003 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
14004 spool directory.
14005 The value set by the option can be overridden by the &%-oP%& command line
14006 option. A pid file is not written if a &"non-standard"& daemon is run by means
14007 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
14008
14009
14010 .option pipelining_advertise_hosts main "host list&!!" *
14011 .cindex "PIPELINING" "suppressing advertising"
14012 This option can be used to suppress the advertisement of the SMTP
14013 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
14014 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
14015 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
14016 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
14017 that clients will use it; &"out of order"& commands that are &"expected"& do
14018 not count as protocol errors (see &%smtp_max_synprot_errors%&).
14019
14020
14021 .option preserve_message_logs main boolean false
14022 .cindex "message logs" "preserving"
14023 If this option is set, message log files are not deleted when messages are
14024 completed. Instead, they are moved to a sub-directory of the spool directory
14025 called &_msglog.OLD_&, where they remain available for statistical or debugging
14026 purposes. This is a dangerous option to set on systems with any appreciable
14027 volume of mail. Use with care!
14028
14029
14030 .option primary_hostname main string "see below"
14031 .cindex "name" "of local host"
14032 .cindex "host" "name of local"
14033 .cindex "local host" "name of"
14034 .vindex "&$primary_hostname$&"
14035 This specifies the name of the current host. It is used in the default EHLO or
14036 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
14037 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
14038 The value is also used by default in some SMTP response messages from an Exim
14039 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
14040
14041 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
14042 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
14043 contains only one component, Exim passes it to &[gethostbyname()]& (or
14044 &[getipnodebyname()]& when available) in order to obtain the fully qualified
14045 version. The variable &$primary_hostname$& contains the host name, whether set
14046 explicitly by this option, or defaulted.
14047
14048
14049 .option print_topbitchars main boolean false
14050 .cindex "printing characters"
14051 .cindex "8-bit characters"
14052 By default, Exim considers only those characters whose codes lie in the range
14053 32&--126 to be printing characters. In a number of circumstances (for example,
14054 when writing log entries) non-printing characters are converted into escape
14055 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
14056 is set, code values of 128 and above are also considered to be printing
14057 characters.
14058
14059 This option also affects the header syntax checks performed by the
14060 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
14061 the user's full name when constructing From: and Sender: addresses (as
14062 described in section &<<SECTconstr>>&). Setting this option can cause
14063 Exim to generate eight bit message headers that do not conform to the
14064 standards.
14065
14066
14067 .option process_log_path main string unset
14068 .cindex "process log path"
14069 .cindex "log" "process log"
14070 .cindex "&'exiwhat'&"
14071 This option sets the name of the file to which an Exim process writes its
14072 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
14073 utility script. If this option is unset, the file called &_exim-process.info_&
14074 in Exim's spool directory is used. The ability to specify the name explicitly
14075 can be useful in environments where two different Exims are running, using
14076 different spool directories.
14077
14078
14079 .option prod_requires_admin main boolean true
14080 .oindex "&%-M%&"
14081 .oindex "&%-R%&"
14082 .oindex "&%-q%&"
14083 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
14084 admin user unless &%prod_requires_admin%& is set false. See also
14085 &%queue_list_requires_admin%&.
14086
14087
14088 .option qualify_domain main string "see below"
14089 .cindex "domain" "for qualifying addresses"
14090 .cindex "address" "qualification"
14091 This option specifies the domain name that is added to any envelope sender
14092 addresses that do not have a domain qualification. It also applies to
14093 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
14094 are accepted by default only for locally-generated messages. Qualification is
14095 also applied to addresses in header lines such as &'From:'& and &'To:'& for
14096 locally-generated messages, unless the &%-bnq%& command line option is used.
14097
14098 Messages from external sources must always contain fully qualified addresses,
14099 unless the sending host matches &%sender_unqualified_hosts%& or
14100 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
14101 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
14102 necessary. Internally, Exim always works with fully qualified envelope
14103 addresses. If &%qualify_domain%& is not set, it defaults to the
14104 &%primary_hostname%& value.
14105
14106
14107 .option qualify_recipient main string "see below"
14108 This option allows you to specify a different domain for qualifying recipient
14109 addresses to the one that is used for senders. See &%qualify_domain%& above.
14110
14111
14112
14113 .option queue_domains main "domain list&!!" unset
14114 .cindex "domain" "specifying non-immediate delivery"
14115 .cindex "queueing incoming messages"
14116 .cindex "message" "queueing certain domains"
14117 This option lists domains for which immediate delivery is not required.
14118 A delivery process is started whenever a message is received, but only those
14119 domains that do not match are processed. All other deliveries wait until the
14120 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
14121
14122
14123 .option queue_list_requires_admin main boolean true
14124 .oindex "&%-bp%&"
14125 The &%-bp%& command-line option, which lists the messages that are on the
14126 queue, requires the caller to be an admin user unless
14127 &%queue_list_requires_admin%& is set false. See also &%prod_requires_admin%&.
14128
14129
14130 .option queue_only main boolean false
14131 .cindex "queueing incoming messages"
14132 .cindex "message" "queueing unconditionally"
14133 If &%queue_only%& is set, a delivery process is not automatically started
14134 whenever a message is received. Instead, the message waits on the queue for the
14135 next queue run. Even if &%queue_only%& is false, incoming messages may not get
14136 delivered immediately when certain conditions (such as heavy load) occur.
14137
14138 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
14139 and &%-odi%& command line options override &%queue_only%& unless
14140 &%queue_only_override%& is set false. See also &%queue_only_file%&,
14141 &%queue_only_load%&, and &%smtp_accept_queue%&.
14142
14143
14144 .option queue_only_file main string unset
14145 .cindex "queueing incoming messages"
14146 .cindex "message" "queueing by file existence"
14147 This option can be set to a colon-separated list of absolute path names, each
14148 one optionally preceded by &"smtp"&. When Exim is receiving a message,
14149 it tests for the existence of each listed path using a call to &[stat()]&. For
14150 each path that exists, the corresponding queueing option is set.
14151 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
14152 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
14153 .code
14154 queue_only_file = smtp/some/file
14155 .endd
14156 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
14157 &_/some/file_& exists.
14158
14159
14160 .option queue_only_load main fixed-point unset
14161 .cindex "load average"
14162 .cindex "queueing incoming messages"
14163 .cindex "message" "queueing by load"
14164 If the system load average is higher than this value, incoming messages from
14165 all sources are queued, and no automatic deliveries are started. If this
14166 happens during local or remote SMTP input, all subsequent messages received on
14167 the same SMTP connection are queued by default, whatever happens to the load in
14168 the meantime, but this can be changed by setting &%queue_only_load_latch%&
14169 false.
14170
14171 Deliveries will subsequently be performed by queue runner processes. This
14172 option has no effect on ancient operating systems on which Exim cannot
14173 determine the load average. See also &%deliver_queue_load_max%& and
14174 &%smtp_load_reserve%&.
14175
14176
14177 .option queue_only_load_latch main boolean true
14178 .cindex "load average" "re-evaluating per message"
14179 When this option is true (the default), once one message has been queued
14180 because the load average is higher than the value set by &%queue_only_load%&,
14181 all subsequent messages received on the same SMTP connection are also queued.
14182 This is a deliberate choice; even though the load average may fall below the
14183 threshold, it doesn't seem right to deliver later messages on the same
14184 connection when not delivering earlier ones. However, there are special
14185 circumstances such as very long-lived connections from scanning appliances
14186 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
14187 should be set false. This causes the value of the load average to be
14188 re-evaluated for each message.
14189
14190
14191 .option queue_only_override main boolean true
14192 .cindex "queueing incoming messages"
14193 When this option is true, the &%-od%&&'x'& command line options override the
14194 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
14195 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
14196 to override; they are accepted, but ignored.
14197
14198
14199 .option queue_run_in_order main boolean false
14200 .cindex "queue runner" "processing messages in order"
14201 If this option is set, queue runs happen in order of message arrival instead of
14202 in an arbitrary order. For this to happen, a complete list of the entire queue
14203 must be set up before the deliveries start. When the queue is all held in a
14204 single directory (the default), a single list is created for both the ordered
14205 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
14206 single list is not created when &%queue_run_in_order%& is false. In this case,
14207 the sub-directories are processed one at a time (in a random order), and this
14208 avoids setting up one huge list for the whole queue. Thus, setting
14209 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
14210 when the queue is large, because of the extra work in setting up the single,
14211 large list. In most situations, &%queue_run_in_order%& should not be set.
14212
14213
14214
14215 .option queue_run_max main integer 5
14216 .cindex "queue runner" "maximum number of"
14217 This controls the maximum number of queue runner processes that an Exim daemon
14218 can run simultaneously. This does not mean that it starts them all at once,
14219 but rather that if the maximum number are still running when the time comes to
14220 start another one, it refrains from starting another one. This can happen with
14221 very large queues and/or very sluggish deliveries. This option does not,
14222 however, interlock with other processes, so additional queue runners can be
14223 started by other means, or by killing and restarting the daemon.
14224
14225 Setting this option to zero does not suppress queue runs; rather, it disables
14226 the limit, allowing any number of simultaneous queue runner processes to be
14227 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
14228 the daemon's command line.
14229
14230 .option queue_smtp_domains main "domain list&!!" unset
14231 .cindex "queueing incoming messages"
14232 .cindex "message" "queueing remote deliveries"
14233 When this option is set, a delivery process is started whenever a message is
14234 received, routing is performed, and local deliveries take place.
14235 However, if any SMTP deliveries are required for domains that match
14236 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
14237 message waits on the queue for the next queue run. Since routing of the message
14238 has taken place, Exim knows to which remote hosts it must be delivered, and so
14239 when the queue run happens, multiple messages for the same host are delivered
14240 over a single SMTP connection. The &%-odqs%& command line option causes all
14241 SMTP deliveries to be queued in this way, and is equivalent to setting
14242 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
14243 &%queue_domains%&.
14244
14245
14246 .option receive_timeout main time 0s
14247 .cindex "timeout" "for non-SMTP input"
14248 This option sets the timeout for accepting a non-SMTP message, that is, the
14249 maximum time that Exim waits when reading a message on the standard input. If
14250 the value is zero, it will wait for ever. This setting is overridden by the
14251 &%-or%& command line option. The timeout for incoming SMTP messages is
14252 controlled by &%smtp_receive_timeout%&.
14253
14254 .option received_header_text main string&!! "see below"
14255 .cindex "customizing" "&'Received:'& header"
14256 .cindex "&'Received:'& header line" "customizing"
14257 This string defines the contents of the &'Received:'& message header that is
14258 added to each message, except for the timestamp, which is automatically added
14259 on at the end (preceded by a semicolon). The string is expanded each time it is
14260 used. If the expansion yields an empty string, no &'Received:'& header line is
14261 added to the message. Otherwise, the string should start with the text
14262 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
14263 header lines. The default setting is:
14264
14265 .code
14266 received_header_text = Received: \
14267 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
14268 {${if def:sender_ident \
14269 {from ${quote_local_part:$sender_ident} }}\
14270 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
14271 by $primary_hostname \
14272 ${if def:received_protocol {with $received_protocol}} \
14273 ${if def:tls_cipher {($tls_cipher)\n\t}}\
14274 (Exim $version_number)\n\t\
14275 ${if def:sender_address \
14276 {(envelope-from <$sender_address>)\n\t}}\
14277 id $message_exim_id\
14278 ${if def:received_for {\n\tfor $received_for}}
14279 .endd
14280
14281 The reference to the TLS cipher is omitted when Exim is built without TLS
14282 support. The use of conditional expansions ensures that this works for both
14283 locally generated messages and messages received from remote hosts, giving
14284 header lines such as the following:
14285 .code
14286 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
14287 by marley.carol.example with esmtp (Exim 4.00)
14288 (envelope-from <bob@carol.example>)
14289 id 16IOWa-00019l-00
14290 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
14291 Received: by scrooge.carol.example with local (Exim 4.00)
14292 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
14293 .endd
14294 Until the body of the message has been received, the timestamp is the time when
14295 the message started to be received. Once the body has arrived, and all policy
14296 checks have taken place, the timestamp is updated to the time at which the
14297 message was accepted.
14298
14299
14300 .option received_headers_max main integer 30
14301 .cindex "loop" "prevention"
14302 .cindex "mail loop prevention"
14303 .cindex "&'Received:'& header line" "counting"
14304 When a message is to be delivered, the number of &'Received:'& headers is
14305 counted, and if it is greater than this parameter, a mail loop is assumed to
14306 have occurred, the delivery is abandoned, and an error message is generated.
14307 This applies to both local and remote deliveries.
14308
14309
14310 .option recipient_unqualified_hosts main "host list&!!" unset
14311 .cindex "unqualified addresses"
14312 .cindex "host" "unqualified addresses from"
14313 This option lists those hosts from which Exim is prepared to accept unqualified
14314 recipient addresses in message envelopes. The addresses are made fully
14315 qualified by the addition of the &%qualify_recipient%& value. This option also
14316 affects message header lines. Exim does not reject unqualified recipient
14317 addresses in headers, but it qualifies them only if the message came from a
14318 host that matches &%recipient_unqualified_hosts%&,
14319 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
14320 option was not set.
14321
14322
14323 .option recipients_max main integer 0
14324 .cindex "limit" "number of recipients"
14325 .cindex "recipient" "maximum number"
14326 If this option is set greater than zero, it specifies the maximum number of
14327 original recipients for any message. Additional recipients that are generated
14328 by aliasing or forwarding do not count. SMTP messages get a 452 response for
14329 all recipients over the limit; earlier recipients are delivered as normal.
14330 Non-SMTP messages with too many recipients are failed, and no deliveries are
14331 done.
14332
14333 .cindex "RCPT" "maximum number of incoming"
14334 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
14335 RCPT commands in a single message.
14336
14337
14338 .option recipients_max_reject main boolean false
14339 If this option is set true, Exim rejects SMTP messages containing too many
14340 recipients by giving 552 errors to the surplus RCPT commands, and a 554
14341 error to the eventual DATA command. Otherwise (the default) it gives a 452
14342 error to the surplus RCPT commands and accepts the message on behalf of the
14343 initial set of recipients. The remote server should then re-send the message
14344 for the remaining recipients at a later time.
14345
14346
14347 .option remote_max_parallel main integer 2
14348 .cindex "delivery" "parallelism for remote"
14349 This option controls parallel delivery of one message to a number of remote
14350 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
14351 does all the remote deliveries for a message one by one. Otherwise, if a single
14352 message has to be delivered to more than one remote host, or if several copies
14353 have to be sent to the same remote host, up to &%remote_max_parallel%&
14354 deliveries are done simultaneously. If more than &%remote_max_parallel%&
14355 deliveries are required, the maximum number of processes are started, and as
14356 each one finishes, another is begun. The order of starting processes is the
14357 same as if sequential delivery were being done, and can be controlled by the
14358 &%remote_sort_domains%& option. If parallel delivery takes place while running
14359 with debugging turned on, the debugging output from each delivery process is
14360 tagged with its process id.
14361
14362 This option controls only the maximum number of parallel deliveries for one
14363 message in one Exim delivery process. Because Exim has no central queue
14364 manager, there is no way of controlling the total number of simultaneous
14365 deliveries if the configuration allows a delivery attempt as soon as a message
14366 is received.
14367
14368 .cindex "number of deliveries"
14369 .cindex "delivery" "maximum number of"
14370 If you want to control the total number of deliveries on the system, you
14371 need to set the &%queue_only%& option. This ensures that all incoming messages
14372 are added to the queue without starting a delivery process. Then set up an Exim
14373 daemon to start queue runner processes at appropriate intervals (probably
14374 fairly often, for example, every minute), and limit the total number of queue
14375 runners by setting the &%queue_run_max%& parameter. Because each queue runner
14376 delivers only one message at a time, the maximum number of deliveries that can
14377 then take place at once is &%queue_run_max%& multiplied by
14378 &%remote_max_parallel%&.
14379
14380 If it is purely remote deliveries you want to control, use
14381 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
14382 doing the SMTP routing before queueing, so that several messages for the same
14383 host will eventually get delivered down the same connection.
14384
14385
14386 .option remote_sort_domains main "domain list&!!" unset
14387 .cindex "sorting remote deliveries"
14388 .cindex "delivery" "sorting remote"
14389 When there are a number of remote deliveries for a message, they are sorted by
14390 domain into the order given by this list. For example,
14391 .code
14392 remote_sort_domains = *.cam.ac.uk:*.uk
14393 .endd
14394 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
14395 then to those in the &%uk%& domain, then to any others.
14396
14397
14398 .option retry_data_expire main time 7d
14399 .cindex "hints database" "data expiry"
14400 This option sets a &"use before"& time on retry information in Exim's hints
14401 database. Any older retry data is ignored. This means that, for example, once a
14402 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
14403 past failures.
14404
14405
14406 .option retry_interval_max main time 24h
14407 .cindex "retry" "limit on interval"
14408 .cindex "limit" "on retry interval"
14409 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
14410 intervals between delivery attempts for messages that cannot be delivered
14411 straight away. This option sets an overall limit to the length of time between
14412 retries. It cannot be set greater than 24 hours; any attempt to do so forces
14413 the default value.
14414
14415
14416 .option return_path_remove main boolean true
14417 .cindex "&'Return-path:'& header line" "removing"
14418 RFC 2821, section 4.4, states that an SMTP server must insert a
14419 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
14420 The &'Return-path:'& header preserves the sender address as received in the
14421 MAIL command. This description implies that this header should not be present
14422 in an incoming message. If &%return_path_remove%& is true, any existing
14423 &'Return-path:'& headers are removed from messages at the time they are
14424 received. Exim's transports have options for adding &'Return-path:'& headers at
14425 the time of delivery. They are normally used only for final local deliveries.
14426
14427
14428 .option return_size_limit main integer 100K
14429 This option is an obsolete synonym for &%bounce_return_size_limit%&.
14430
14431
14432 .option rfc1413_hosts main "host list&!!" *
14433 .cindex "RFC 1413"
14434 .cindex "host" "for RFC 1413 calls"
14435 RFC 1413 identification calls are made to any client host which matches an item
14436 in the list.
14437
14438 .option rfc1413_query_timeout main time 5s
14439 .cindex "RFC 1413" "query timeout"
14440 .cindex "timeout" "for RFC 1413 call"
14441 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
14442 no RFC 1413 calls are ever made.
14443
14444
14445 .option sender_unqualified_hosts main "host list&!!" unset
14446 .cindex "unqualified addresses"
14447 .cindex "host" "unqualified addresses from"
14448 This option lists those hosts from which Exim is prepared to accept unqualified
14449 sender addresses. The addresses are made fully qualified by the addition of
14450 &%qualify_domain%&. This option also affects message header lines. Exim does
14451 not reject unqualified addresses in headers that contain sender addresses, but
14452 it qualifies them only if the message came from a host that matches
14453 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
14454 using TCP/IP), and the &%-bnq%& option was not set.
14455
14456
14457 .option smtp_accept_keepalive main boolean true
14458 .cindex "keepalive" "on incoming connection"
14459 This option controls the setting of the SO_KEEPALIVE option on incoming
14460 TCP/IP socket connections. When set, it causes the kernel to probe idle
14461 connections periodically, by sending packets with &"old"& sequence numbers. The
14462 other end of the connection should send an acknowledgment if the connection is
14463 still okay or a reset if the connection has been aborted. The reason for doing
14464 this is that it has the beneficial effect of freeing up certain types of
14465 connection that can get stuck when the remote host is disconnected without
14466 tidying up the TCP/IP call properly. The keepalive mechanism takes several
14467 hours to detect unreachable hosts.
14468
14469
14470
14471 .option smtp_accept_max main integer 20
14472 .cindex "limit" "incoming SMTP connections"
14473 .cindex "SMTP" "incoming connection count"
14474 .cindex "inetd"
14475 This option specifies the maximum number of simultaneous incoming SMTP calls
14476 that Exim will accept. It applies only to the listening daemon; there is no
14477 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
14478 value is set to zero, no limit is applied. However, it is required to be
14479 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
14480 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
14481
14482 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
14483 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
14484 that limit has not been reached for the client host, &%smtp_accept_reserve%&
14485 and &%smtp_load_reserve%& are then checked before accepting the connection.
14486
14487
14488 .option smtp_accept_max_nonmail main integer 10
14489 .cindex "limit" "non-mail SMTP commands"
14490 .cindex "SMTP" "limiting non-mail commands"
14491 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
14492 the connection if there are too many. This option defines &"too many"&. The
14493 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
14494 client looping sending EHLO, for example. The check is applied only if the
14495 client host matches &%smtp_accept_max_nonmail_hosts%&.
14496
14497 When a new message is expected, one occurrence of RSET is not counted. This
14498 allows a client to send one RSET between messages (this is not necessary,
14499 but some clients do it). Exim also allows one uncounted occurrence of HELO
14500 or EHLO, and one occurrence of STARTTLS between messages. After
14501 starting up a TLS session, another EHLO is expected, and so it too is not
14502 counted. The first occurrence of AUTH in a connection, or immediately
14503 following STARTTLS is not counted. Otherwise, all commands other than
14504 MAIL, RCPT, DATA, and QUIT are counted.
14505
14506
14507 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
14508 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
14509 check by setting this option. The default value makes it apply to all hosts. By
14510 changing the value, you can exclude any badly-behaved hosts that you have to
14511 live with.
14512
14513
14514 . Allow this long option name to split; give it unsplit as a fifth argument
14515 . for the automatic .oindex that is generated by .option.
14516
14517 .option "smtp_accept_max_per_ &~&~connection" main integer 1000 &&&
14518 smtp_accept_max_per_connection
14519 .cindex "SMTP" "limiting incoming message count"
14520 .cindex "limit" "messages per SMTP connection"
14521 The value of this option limits the number of MAIL commands that Exim is
14522 prepared to accept over a single SMTP connection, whether or not each command
14523 results in the transfer of a message. After the limit is reached, a 421
14524 response is given to subsequent MAIL commands. This limit is a safety
14525 precaution against a client that goes mad (incidents of this type have been
14526 seen).
14527
14528
14529 .option smtp_accept_max_per_host main string&!! unset
14530 .cindex "limit" "SMTP connections from one host"
14531 .cindex "host" "limiting SMTP connections from"
14532 This option restricts the number of simultaneous IP connections from a single
14533 host (strictly, from a single IP address) to the Exim daemon. The option is
14534 expanded, to enable different limits to be applied to different hosts by
14535 reference to &$sender_host_address$&. Once the limit is reached, additional
14536 connection attempts from the same host are rejected with error code 421. This
14537 is entirely independent of &%smtp_accept_reserve%&. The option's default value
14538 of zero imposes no limit. If this option is set greater than zero, it is
14539 required that &%smtp_accept_max%& be non-zero.
14540
14541 &*Warning*&: When setting this option you should not use any expansion
14542 constructions that take an appreciable amount of time. The expansion and test
14543 happen in the main daemon loop, in order to reject additional connections
14544 without forking additional processes (otherwise a denial-of-service attack
14545 could cause a vast number or processes to be created). While the daemon is
14546 doing this processing, it cannot accept any other incoming connections.
14547
14548
14549
14550 .option smtp_accept_queue main integer 0
14551 .cindex "SMTP" "incoming connection count"
14552 .cindex "queueing incoming messages"
14553 .cindex "message" "queueing by SMTP connection count"
14554 If the number of simultaneous incoming SMTP connections being handled via the
14555 listening daemon exceeds this value, messages received by SMTP are just placed
14556 on the queue; no delivery processes are started automatically. The count is
14557 fixed at the start of an SMTP connection. It cannot be updated in the
14558 subprocess that receives messages, and so the queueing or not queueing applies
14559 to all messages received in the same connection.
14560
14561 A value of zero implies no limit, and clearly any non-zero value is useful only
14562 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
14563 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
14564 various &%-od%&&'x'& command line options.
14565
14566
14567 . Allow this long option name to split; give it unsplit as a fifth argument
14568 . for the automatic .oindex that is generated by .option.
14569
14570 .option "smtp_accept_queue_per_ &~&~connection" main integer 10 &&&
14571 smtp_accept_queue_per_connection
14572 .cindex "queueing incoming messages"
14573 .cindex "message" "queueing by message count"
14574 This option limits the number of delivery processes that Exim starts
14575 automatically when receiving messages via SMTP, whether via the daemon or by
14576 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
14577 and the number of messages received in a single SMTP session exceeds this
14578 number, subsequent messages are placed on the queue, but no delivery processes
14579 are started. This helps to limit the number of Exim processes when a server
14580 restarts after downtime and there is a lot of mail waiting for it on other
14581 systems. On large systems, the default should probably be increased, and on
14582 dial-in client systems it should probably be set to zero (that is, disabled).
14583
14584
14585 .option smtp_accept_reserve main integer 0
14586 .cindex "SMTP" "incoming call count"
14587 .cindex "host" "reserved"
14588 When &%smtp_accept_max%& is set greater than zero, this option specifies a
14589 number of SMTP connections that are reserved for connections from the hosts
14590 that are specified in &%smtp_reserve_hosts%&. The value set in
14591 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
14592 restricted to this number of connections; the option specifies a minimum number
14593 of connection slots for them, not a maximum. It is a guarantee that this group
14594 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
14595 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
14596 individual host.
14597
14598 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
14599 set to 5, once there are 45 active connections (from any hosts), new
14600 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
14601 provided the other criteria for acceptance are met.
14602
14603
14604 .option smtp_active_hostname main string&!! unset
14605 .cindex "host" "name in SMTP responses"
14606 .cindex "SMTP" "host name in responses"
14607 .vindex "&$primary_hostname$&"
14608 This option is provided for multi-homed servers that want to masquerade as
14609 several different hosts. At the start of an incoming SMTP connection, its value
14610 is expanded and used instead of the value of &$primary_hostname$& in SMTP
14611 responses. For example, it is used as domain name in the response to an
14612 incoming HELO or EHLO command.
14613
14614 .vindex "&$smtp_active_hostname$&"
14615 The active hostname is placed in the &$smtp_active_hostname$& variable, which
14616 is saved with any messages that are received. It is therefore available for use
14617 in routers and transports when the message is later delivered.
14618
14619 If this option is unset, or if its expansion is forced to fail, or if the
14620 expansion results in an empty string, the value of &$primary_hostname$& is
14621 used. Other expansion failures cause a message to be written to the main and
14622 panic logs, and the SMTP command receives a temporary error. Typically, the
14623 value of &%smtp_active_hostname%& depends on the incoming interface address.
14624 For example:
14625 .code
14626 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
14627 {cox.mydomain}{box.mydomain}}
14628 .endd
14629
14630 Although &$smtp_active_hostname$& is primarily concerned with incoming
14631 messages, it is also used as the default for HELO commands in callout
14632 verification if there is no remote transport from which to obtain a
14633 &%helo_data%& value.
14634
14635 .option smtp_banner main string&!! "see below"
14636 .cindex "SMTP" "welcome banner"
14637 .cindex "banner for SMTP"
14638 .cindex "welcome banner for SMTP"
14639 .cindex "customizing" "SMTP banner"
14640 This string, which is expanded every time it is used, is output as the initial
14641 positive response to an SMTP connection. The default setting is:
14642 .code
14643 smtp_banner = $smtp_active_hostname ESMTP Exim \
14644 $version_number $tod_full
14645 .endd
14646 Failure to expand the string causes a panic error. If you want to create a
14647 multiline response to the initial SMTP connection, use &"\n"& in the string at
14648 appropriate points, but not at the end. Note that the 220 code is not included
14649 in this string. Exim adds it automatically (several times in the case of a
14650 multiline response).
14651
14652
14653 .option smtp_check_spool_space main boolean true
14654 .cindex "checking disk space"
14655 .cindex "disk space, checking"
14656 .cindex "spool directory" "checking space"
14657 When this option is set, if an incoming SMTP session encounters the SIZE
14658 option on a MAIL command, it checks that there is enough space in the
14659 spool directory's partition to accept a message of that size, while still
14660 leaving free the amount specified by &%check_spool_space%& (even if that value
14661 is zero). If there isn't enough space, a temporary error code is returned.
14662
14663
14664 .option smtp_connect_backlog main integer 20
14665 .cindex "connection backlog"
14666 .cindex "SMTP" "connection backlog"
14667 .cindex "backlog of connections"
14668 This option specifies a maximum number of waiting SMTP connections. Exim passes
14669 this value to the TCP/IP system when it sets up its listener. Once this number
14670 of connections are waiting for the daemon's attention, subsequent connection
14671 attempts are refused at the TCP/IP level. At least, that is what the manuals
14672 say; in some circumstances such connection attempts have been observed to time
14673 out instead. For large systems it is probably a good idea to increase the
14674 value (to 50, say). It also gives some protection against denial-of-service
14675 attacks by SYN flooding.
14676
14677
14678 .option smtp_enforce_sync main boolean true
14679 .cindex "SMTP" "synchronization checking"
14680 .cindex "synchronization checking in SMTP"
14681 The SMTP protocol specification requires the client to wait for a response from
14682 the server at certain points in the dialogue. Without PIPELINING these
14683 synchronization points are after every command; with PIPELINING they are
14684 fewer, but they still exist.
14685
14686 Some spamming sites send out a complete set of SMTP commands without waiting
14687 for any response. Exim protects against this by rejecting a message if the
14688 client has sent further input when it should not have. The error response &"554
14689 SMTP synchronization error"& is sent, and the connection is dropped. Testing
14690 for this error cannot be perfect because of transmission delays (unexpected
14691 input may be on its way but not yet received when Exim checks). However, it
14692 does detect many instances.
14693
14694 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
14695 If you want to disable the check selectively (for example, only for certain
14696 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
14697 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
14698
14699
14700
14701 .option smtp_etrn_command main string&!! unset
14702 .cindex "ETRN" "command to be run"
14703 .vindex "&$domain$&"
14704 If this option is set, the given command is run whenever an SMTP ETRN
14705 command is received from a host that is permitted to issue such commands (see
14706 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
14707 are independently expanded. The expansion variable &$domain$& is set to the
14708 argument of the ETRN command, and no syntax checking is done on it. For
14709 example:
14710 .code
14711 smtp_etrn_command = /etc/etrn_command $domain \
14712 $sender_host_address
14713 .endd
14714 A new process is created to run the command, but Exim does not wait for it to
14715 complete. Consequently, its status cannot be checked. If the command cannot be
14716 run, a line is written to the panic log, but the ETRN caller still receives
14717 a 250 success response. Exim is normally running under its own uid when
14718 receiving SMTP, so it is not possible for it to change the uid before running
14719 the command.
14720
14721
14722 .option smtp_etrn_serialize main boolean true
14723 .cindex "ETRN" "serializing"
14724 When this option is set, it prevents the simultaneous execution of more than
14725 one identical command as a result of ETRN in an SMTP connection. See
14726 section &<<SECTETRN>>& for details.
14727
14728
14729 .option smtp_load_reserve main fixed-point unset
14730 .cindex "load average"
14731 If the system load average ever gets higher than this, incoming SMTP calls are
14732 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
14733 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
14734 the load is over the limit. The option has no effect on ancient operating
14735 systems on which Exim cannot determine the load average. See also
14736 &%deliver_queue_load_max%& and &%queue_only_load%&.
14737
14738
14739
14740 .option smtp_max_synprot_errors main integer 3
14741 .cindex "SMTP" "limiting syntax and protocol errors"
14742 .cindex "limit" "SMTP syntax and protocol errors"
14743 Exim rejects SMTP commands that contain syntax or protocol errors. In
14744 particular, a syntactically invalid email address, as in this command:
14745 .code
14746 RCPT TO:<abc xyz@a.b.c>
14747 .endd
14748 causes immediate rejection of the command, before any other tests are done.
14749 (The ACL cannot be run if there is no valid address to set up for it.) An
14750 example of a protocol error is receiving RCPT before MAIL. If there are
14751 too many syntax or protocol errors in one SMTP session, the connection is
14752 dropped. The limit is set by this option.
14753
14754 .cindex "PIPELINING" "expected errors"
14755 When the PIPELINING extension to SMTP is in use, some protocol errors are
14756 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
14757 Exim assumes that PIPELINING will be used if it advertises it (see
14758 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
14759 not count towards the limit.
14760
14761
14762
14763 .option smtp_max_unknown_commands main integer 3
14764 .cindex "SMTP" "limiting unknown commands"
14765 .cindex "limit" "unknown SMTP commands"
14766 If there are too many unrecognized commands in an incoming SMTP session, an
14767 Exim server drops the connection. This is a defence against some kinds of abuse
14768 that subvert web
14769 clients
14770 into making connections to SMTP ports; in these circumstances, a number of
14771 non-SMTP command lines are sent first.
14772
14773
14774
14775 .option smtp_ratelimit_hosts main "host list&!!" unset
14776 .cindex "SMTP" "rate limiting"
14777 .cindex "limit" "rate of message arrival"
14778 .cindex "RCPT" "rate limiting"
14779 Some sites find it helpful to be able to limit the rate at which certain hosts
14780 can send them messages, and the rate at which an individual message can specify
14781 recipients.
14782
14783 Exim has two rate-limiting facilities. This section describes the older
14784 facility, which can limit rates within a single connection. The newer
14785 &%ratelimit%& ACL condition can limit rates across all connections. See section
14786 &<<SECTratelimiting>>& for details of the newer facility.
14787
14788 When a host matches &%smtp_ratelimit_hosts%&, the values of
14789 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
14790 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
14791 respectively. Each option, if set, must contain a set of four comma-separated
14792 values:
14793
14794 .ilist
14795 A threshold, before which there is no rate limiting.
14796 .next
14797 An initial time delay. Unlike other times in Exim, numbers with decimal
14798 fractional parts are allowed here.
14799 .next
14800 A factor by which to increase the delay each time.
14801 .next
14802 A maximum value for the delay. This should normally be less than 5 minutes,
14803 because after that time, the client is liable to timeout the SMTP command.
14804 .endlist
14805
14806 For example, these settings have been used successfully at the site which
14807 first suggested this feature, for controlling mail from their customers:
14808 .code
14809 smtp_ratelimit_mail = 2,0.5s,1.05,4m
14810 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
14811 .endd
14812 The first setting specifies delays that are applied to MAIL commands after
14813 two have been received over a single connection. The initial delay is 0.5
14814 seconds, increasing by a factor of 1.05 each time. The second setting applies
14815 delays to RCPT commands when more than four occur in a single message.
14816
14817
14818 .option smtp_ratelimit_mail main string unset
14819 See &%smtp_ratelimit_hosts%& above.
14820
14821
14822 .option smtp_ratelimit_rcpt main string unset
14823 See &%smtp_ratelimit_hosts%& above.
14824
14825
14826 .option smtp_receive_timeout main time 5m
14827 .cindex "timeout" "for SMTP input"
14828 .cindex "SMTP" "input timeout"
14829 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
14830 input, including batch SMTP. If a line of input (either an SMTP command or a
14831 data line) is not received within this time, the SMTP connection is dropped and
14832 the message is abandoned.
14833 A line is written to the log containing one of the following messages:
14834 .code
14835 SMTP command timeout on connection from...
14836 SMTP data timeout on connection from...
14837 .endd
14838 The former means that Exim was expecting to read an SMTP command; the latter
14839 means that it was in the DATA phase, reading the contents of a message.
14840
14841
14842 .oindex "&%-os%&"
14843 The value set by this option can be overridden by the
14844 &%-os%& command-line option. A setting of zero time disables the timeout, but
14845 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
14846 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
14847 timeout is controlled by &%receive_timeout%& and &%-or%&.
14848
14849
14850 .option smtp_reserve_hosts main "host list&!!" unset
14851 This option defines hosts for which SMTP connections are reserved; see
14852 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
14853
14854
14855 .option smtp_return_error_details main boolean false
14856 .cindex "SMTP" "details policy failures"
14857 .cindex "policy control" "rejection, returning details"
14858 In the default state, Exim uses bland messages such as
14859 &"Administrative prohibition"& when it rejects SMTP commands for policy
14860 reasons. Many sysadmins like this because it gives away little information
14861 to spammers. However, some other sysadmins who are applying strict checking
14862 policies want to give out much fuller information about failures. Setting
14863 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
14864 example, instead of &"Administrative prohibition"&, it might give:
14865 .code
14866 550-Rejected after DATA: '>' missing at end of address:
14867 550 failing address in "From" header is: <user@dom.ain
14868 .endd
14869
14870 .option spamd_address main string "see below"
14871 This option is available when Exim is compiled with the content-scanning
14872 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
14873 The default value is
14874 .code
14875 127.0.0.1 783
14876 .endd
14877 See section &<<SECTscanspamass>>& for more details.
14878
14879
14880
14881 .option split_spool_directory main boolean false
14882 .cindex "multiple spool directories"
14883 .cindex "spool directory" "split"
14884 .cindex "directories, multiple"
14885 If this option is set, it causes Exim to split its input directory into 62
14886 subdirectories, each with a single alphanumeric character as its name. The
14887 sixth character of the message id is used to allocate messages to
14888 subdirectories; this is the least significant base-62 digit of the time of
14889 arrival of the message.
14890
14891 Splitting up the spool in this way may provide better performance on systems
14892 where there are long mail queues, by reducing the number of files in any one
14893 directory. The msglog directory is also split up in a similar way to the input
14894 directory; however, if &%preserve_message_logs%& is set, all old msglog files
14895 are still placed in the single directory &_msglog.OLD_&.
14896
14897 It is not necessary to take any special action for existing messages when
14898 changing &%split_spool_directory%&. Exim notices messages that are in the
14899 &"wrong"& place, and continues to process them. If the option is turned off
14900 after a period of being on, the subdirectories will eventually empty and be
14901 automatically deleted.
14902
14903 When &%split_spool_directory%& is set, the behaviour of queue runner processes
14904 changes. Instead of creating a list of all messages in the queue, and then
14905 trying to deliver each one in turn, it constructs a list of those in one
14906 sub-directory and tries to deliver them, before moving on to the next
14907 sub-directory. The sub-directories are processed in a random order. This
14908 spreads out the scanning of the input directories, and uses less memory. It is
14909 particularly beneficial when there are lots of messages on the queue. However,
14910 if &%queue_run_in_order%& is set, none of this new processing happens. The
14911 entire queue has to be scanned and sorted before any deliveries can start.
14912
14913
14914 .option spool_directory main string&!! "set at compile time"
14915 .cindex "spool directory" "path to"
14916 This defines the directory in which Exim keeps its spool, that is, the messages
14917 it is waiting to deliver. The default value is taken from the compile-time
14918 configuration setting, if there is one. If not, this option must be set. The
14919 string is expanded, so it can contain, for example, a reference to
14920 &$primary_hostname$&.
14921
14922 If the spool directory name is fixed on your installation, it is recommended
14923 that you set it at build time rather than from this option, particularly if the
14924 log files are being written to the spool directory (see &%log_file_path%&).
14925 Otherwise log files cannot be used for errors that are detected early on, such
14926 as failures in the configuration file.
14927
14928 By using this option to override the compiled-in path, it is possible to run
14929 tests of Exim without using the standard spool.
14930
14931 .option sqlite_lock_timeout main time 5s
14932 .cindex "sqlite lookup type" "lock timeout"
14933 This option controls the timeout that the &(sqlite)& lookup uses when trying to
14934 access an SQLite database. See section &<<SECTsqlite>>& for more details.
14935
14936 .option strict_acl_vars main boolean false
14937 .cindex "&ACL;" "variables, handling unset"
14938 This option controls what happens if a syntactically valid but undefined ACL
14939 variable is referenced. If it is false (the default), an empty string
14940 is substituted; if it is true, an error is generated. See section
14941 &<<SECTaclvariables>>& for details of ACL variables.
14942
14943 .option strip_excess_angle_brackets main boolean false
14944 .cindex "angle brackets, excess"
14945 If this option is set, redundant pairs of angle brackets round &"route-addr"&
14946 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
14947 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
14948 passed on to another MTA, the excess angle brackets are not passed on. If this
14949 option is not set, multiple pairs of angle brackets cause a syntax error.
14950
14951
14952 .option strip_trailing_dot main boolean false
14953 .cindex "trailing dot on domain"
14954 .cindex "dot" "trailing on domain"
14955 If this option is set, a trailing dot at the end of a domain in an address is
14956 ignored. If this is in the envelope and the message is passed on to another
14957 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
14958 domain causes a syntax error.
14959 However, addresses in header lines are checked only when an ACL requests header
14960 syntax checking.
14961
14962
14963 .option syslog_duplication main boolean true
14964 .cindex "syslog" "duplicate log lines; suppressing"
14965 When Exim is logging to syslog, it writes the log lines for its three
14966 separate logs at different syslog priorities so that they can in principle
14967 be separated on the logging hosts. Some installations do not require this
14968 separation, and in those cases, the duplication of certain log lines is a
14969 nuisance. If &%syslog_duplication%& is set false, only one copy of any
14970 particular log line is written to syslog. For lines that normally go to
14971 both the main log and the reject log, the reject log version (possibly
14972 containing message header lines) is written, at LOG_NOTICE priority.
14973 Lines that normally go to both the main and the panic log are written at
14974 the LOG_ALERT priority.
14975
14976
14977 .option syslog_facility main string unset
14978 .cindex "syslog" "facility; setting"
14979 This option sets the syslog &"facility"& name, used when Exim is logging to
14980 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
14981 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
14982 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
14983 details of Exim's logging.
14984
14985
14986
14987 .option syslog_processname main string &`exim`&
14988 .cindex "syslog" "process name; setting"
14989 This option sets the syslog &"ident"& name, used when Exim is logging to
14990 syslog. The value must be no longer than 32 characters. See chapter
14991 &<<CHAPlog>>& for details of Exim's logging.
14992
14993
14994
14995 .option syslog_timestamp main boolean true
14996 .cindex "syslog" "timestamps"
14997 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
14998 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
14999 details of Exim's logging.
15000
15001
15002 .option system_filter main string&!! unset
15003 .cindex "filter" "system filter"
15004 .cindex "system filter" "specifying"
15005 .cindex "Sieve filter" "not available for system filter"
15006 This option specifies an Exim filter file that is applied to all messages at
15007 the start of each delivery attempt, before any routing is done. System filters
15008 must be Exim filters; they cannot be Sieve filters. If the system filter
15009 generates any deliveries to files or pipes, or any new mail messages, the
15010 appropriate &%system_filter_..._transport%& option(s) must be set, to define
15011 which transports are to be used. Details of this facility are given in chapter
15012 &<<CHAPsystemfilter>>&.
15013
15014
15015 .option system_filter_directory_transport main string&!! unset
15016 .vindex "&$address_file$&"
15017 This sets the name of the transport driver that is to be used when the
15018 &%save%& command in a system message filter specifies a path ending in &"/"&,
15019 implying delivery of each message into a separate file in some directory.
15020 During the delivery, the variable &$address_file$& contains the path name.
15021
15022
15023 .option system_filter_file_transport main string&!! unset
15024 .cindex "file" "transport for system filter"
15025 This sets the name of the transport driver that is to be used when the &%save%&
15026 command in a system message filter specifies a path not ending in &"/"&. During
15027 the delivery, the variable &$address_file$& contains the path name.
15028
15029 .option system_filter_group main string unset
15030 .cindex "gid (group id)" "system filter"
15031 This option is used only when &%system_filter_user%& is also set. It sets the
15032 gid under which the system filter is run, overriding any gid that is associated
15033 with the user. The value may be numerical or symbolic.
15034
15035 .option system_filter_pipe_transport main string&!! unset
15036 .cindex "&(pipe)& transport" "for system filter"
15037 .vindex "&$address_pipe$&"
15038 This specifies the transport driver that is to be used when a &%pipe%& command
15039 is used in a system filter. During the delivery, the variable &$address_pipe$&
15040 contains the pipe command.
15041
15042
15043 .option system_filter_reply_transport main string&!! unset
15044 .cindex "&(autoreply)& transport" "for system filter"
15045 This specifies the transport driver that is to be used when a &%mail%& command
15046 is used in a system filter.
15047
15048 .option system_filter_user main string unset
15049 .cindex "uid (user id)" "system filter"
15050 If this option is not set, the system filter is run in the main Exim delivery
15051 process, as root. When the option is set, the system filter runs in a separate
15052 process, as the given user. Unless the string consists entirely of digits, it
15053 is looked up in the password data. Failure to find the named user causes a
15054 configuration error. The gid is either taken from the password data, or
15055 specified by &%system_filter_group%&. When the uid is specified numerically,
15056 &%system_filter_group%& is required to be set.
15057
15058 If the system filter generates any pipe, file, or reply deliveries, the uid
15059 under which the filter is run is used when transporting them, unless a
15060 transport option overrides. Normally you should set &%system_filter_user%& if
15061 your system filter generates these kinds of delivery.
15062
15063
15064 .option tcp_nodelay main boolean true
15065 .cindex "daemon" "TCP_NODELAY on sockets"
15066 .cindex "Nagle algorithm"
15067 .cindex "TCP_NODELAY on listening sockets"
15068 If this option is set false, it stops the Exim daemon setting the
15069 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
15070 turns off the &"Nagle algorithm"&, which is a way of improving network
15071 performance in interactive (character-by-character) situations. Turning it off
15072 should improve Exim's performance a bit, so that is what happens by default.
15073 However, it appears that some broken clients cannot cope, and time out. Hence
15074 this option. It affects only those sockets that are set up for listening by the
15075 daemon. Sockets created by the smtp transport for delivering mail always set
15076 TCP_NODELAY.
15077
15078
15079 .option timeout_frozen_after main time 0s
15080 .cindex "frozen messages" "timing out"
15081 .cindex "timeout" "frozen messages"
15082 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
15083 message of any kind that has been on the queue for longer than the given time
15084 is automatically cancelled at the next queue run. If the frozen message is a
15085 bounce message, it is just discarded; otherwise, a bounce is sent to the
15086 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
15087 If you want to timeout frozen bounce messages earlier than other kinds of
15088 frozen message, see &%ignore_bounce_errors_after%&.
15089
15090 &*Note:*& the default value of zero means no timeouts; with this setting,
15091 frozen messages remain on the queue forever (except for any frozen bounce
15092 messages that are released by &%ignore_bounce_errors_after%&).
15093
15094
15095 .option timezone main string unset
15096 .cindex "timezone, setting"
15097 The value of &%timezone%& is used to set the environment variable TZ while
15098 running Exim (if it is different on entry). This ensures that all timestamps
15099 created by Exim are in the required timezone. If you want all your timestamps
15100 to be in UTC (aka GMT) you should set
15101 .code
15102 timezone = UTC
15103 .endd
15104 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
15105 or, if that is not set, from the value of the TZ environment variable when Exim
15106 is built. If &%timezone%& is set to the empty string, either at build or run
15107 time, any existing TZ variable is removed from the environment when Exim
15108 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
15109 unfortunately not all, operating systems.
15110
15111
15112 .option tls_advertise_hosts main "host list&!!" unset
15113 .cindex "TLS" "advertising"
15114 .cindex "encryption" "on SMTP connection"
15115 .cindex "SMTP" "encrypted connection"
15116 When Exim is built with support for TLS encrypted connections, the availability
15117 of the STARTTLS command to set up an encrypted session is advertised in
15118 response to EHLO only to those client hosts that match this option. See
15119 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
15120
15121
15122 .option tls_certificate main string&!! unset
15123 .cindex "TLS" "server certificate; location of"
15124 .cindex "certificate" "server, location of"
15125 The value of this option is expanded, and must then be the absolute path to a
15126 file which contains the server's certificates. The server's private key is also
15127 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
15128 &<<CHAPTLS>>& for further details.
15129
15130 &*Note*&: The certificates defined by this option are used only when Exim is
15131 receiving incoming messages as a server. If you want to supply certificates for
15132 use when sending messages as a client, you must set the &%tls_certificate%&
15133 option in the relevant &(smtp)& transport.
15134
15135
15136 .option tls_crl main string&!! unset
15137 .cindex "TLS" "server certificate revocation list"
15138 .cindex "certificate" "revocation list for server"
15139 This option specifies a certificate revocation list. The expanded value must
15140 be the name of a file that contains a CRL in PEM format.
15141
15142
15143 .option tls_dhparam main string&!! unset
15144 .cindex "TLS" "D-H parameters for server"
15145 The value of this option is expanded, and must then be the absolute path to
15146 a file which contains the server's DH parameter values.
15147 This is used only for OpenSSL. When Exim is linked with GnuTLS, this option is
15148 ignored. See section &<<SECTopenvsgnu>>& for further details.
15149
15150
15151 .option tls_on_connect_ports main "string list" unset
15152 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
15153 operate the obsolete SSMTP (SMTPS) protocol, where a TLS session is immediately
15154 set up without waiting for the client to issue a STARTTLS command. For
15155 further details, see section &<<SECTsupobssmt>>&.
15156
15157
15158
15159 .option tls_privatekey main string&!! unset
15160 .cindex "TLS" "server private key; location of"
15161 The value of this option is expanded, and must then be the absolute path to a
15162 file which contains the server's private key. If this option is unset, or if
15163 the expansion is forced to fail, or the result is an empty string, the private
15164 key is assumed to be in the same file as the server's certificates. See chapter
15165 &<<CHAPTLS>>& for further details.
15166
15167
15168 .option tls_remember_esmtp main boolean false
15169 .cindex "TLS" "esmtp state; remembering"
15170 .cindex "TLS" "broken clients"
15171 If this option is set true, Exim violates the RFCs by remembering that it is in
15172 &"esmtp"& state after successfully negotiating a TLS session. This provides
15173 support for broken clients that fail to send a new EHLO after starting a
15174 TLS session.
15175
15176
15177 .option tls_require_ciphers main string&!! unset
15178 .cindex "TLS" "requiring specific ciphers"
15179 .cindex "cipher" "requiring specific"
15180 This option controls which ciphers can be used for incoming TLS connections.
15181 The &(smtp)& transport has an option of the same name for controlling outgoing
15182 connections. This option is expanded for each connection, so can be varied for
15183 different clients if required. The value of this option must be a list of
15184 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
15185 in somewhat different ways. If GnuTLS is being used, the client controls the
15186 preference order of the available ciphers. Details are given in sections
15187 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
15188
15189
15190 .option tls_try_verify_hosts main "host list&!!" unset
15191 .cindex "TLS" "client certificate verification"
15192 .cindex "certificate" "verification of client"
15193 See &%tls_verify_hosts%& below.
15194
15195
15196 .option tls_verify_certificates main string&!! unset
15197 .cindex "TLS" "client certificate verification"
15198 .cindex "certificate" "verification of client"
15199 The value of this option is expanded, and must then be the absolute path to
15200 a file containing permitted certificates for clients that
15201 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&. Alternatively, if you
15202 are using OpenSSL, you can set &%tls_verify_certificates%& to the name of a
15203 directory containing certificate files. This does not work with GnuTLS; the
15204 option must be set to the name of a single file if you are using GnuTLS.
15205
15206
15207 .option tls_verify_hosts main "host list&!!" unset
15208 .cindex "TLS" "client certificate verification"
15209 .cindex "certificate" "verification of client"
15210 This option, along with &%tls_try_verify_hosts%&, controls the checking of
15211 certificates from clients. The expected certificates are defined by
15212 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
15213 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
15214 &%tls_verify_certificates%& is not set.
15215
15216 Any client that matches &%tls_verify_hosts%& is constrained by
15217 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
15218 present one of the listed certificates. If it does not, the connection is
15219 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
15220 the host to use TLS. It can still send SMTP commands through unencrypted
15221 connections. Forcing a client to use TLS has to be done separately using an
15222 ACL to reject inappropriate commands when the connection is not encrypted.
15223
15224 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
15225 matches this option (but not &%tls_verify_hosts%&), Exim requests a
15226 certificate and checks it against &%tls_verify_certificates%&, but does not
15227 abort the connection if there is no certificate or if it does not match. This
15228 state can be detected in an ACL, which makes it possible to implement policies
15229 such as &"accept for relay only if a verified certificate has been received,
15230 but accept for local delivery if encrypted, even without a verified
15231 certificate"&.
15232
15233 Client hosts that match neither of these lists are not asked to present
15234 certificates.
15235
15236
15237 .option trusted_groups main "string list&!!" unset
15238 .cindex "trusted groups"
15239 .cindex "groups" "trusted"
15240 This option is expanded just once, at the start of Exim's processing. If this
15241 option is set, any process that is running in one of the listed groups, or
15242 which has one of them as a supplementary group, is trusted. The groups can be
15243 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
15244 details of what trusted callers are permitted to do. If neither
15245 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
15246 are trusted.
15247
15248 .option trusted_users main "string list&!!" unset
15249 .cindex "trusted users"
15250 .cindex "user" "trusted"
15251 This option is expanded just once, at the start of Exim's processing. If this
15252 option is set, any process that is running as one of the listed users is
15253 trusted. The users can be specified numerically or by name. See section
15254 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
15255 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
15256 Exim user are trusted.
15257
15258 .option unknown_login main string&!! unset
15259 .cindex "uid (user id)" "unknown caller"
15260 .vindex "&$caller_uid$&"
15261 This is a specialized feature for use in unusual configurations. By default, if
15262 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
15263 gives up. The &%unknown_login%& option can be used to set a login name to be
15264 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
15265 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
15266 is used for the user's real name (gecos field), unless this has been set by the
15267 &%-F%& option.
15268
15269 .option unknown_username main string unset
15270 See &%unknown_login%&.
15271
15272 .option untrusted_set_sender main "address list&!!" unset
15273 .cindex "trusted users"
15274 .cindex "sender" "setting by untrusted user"
15275 .cindex "untrusted user setting sender"
15276 .cindex "user" "untrusted setting sender"
15277 .cindex "envelope sender"
15278 When an untrusted user submits a message to Exim using the standard input, Exim
15279 normally creates an envelope sender address from the user's login and the
15280 default qualification domain. Data from the &%-f%& option (for setting envelope
15281 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
15282 is used) is ignored.
15283
15284 However, untrusted users are permitted to set an empty envelope sender address,
15285 to declare that a message should never generate any bounces. For example:
15286 .code
15287 exim -f '<>' user@domain.example
15288 .endd
15289 .vindex "&$sender_ident$&"
15290 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
15291 other envelope sender addresses in a controlled way. When it is set, untrusted
15292 users are allowed to set envelope sender addresses that match any of the
15293 patterns in the list. Like all address lists, the string is expanded. The
15294 identity of the user is in &$sender_ident$&, so you can, for example, restrict
15295 users to setting senders that start with their login ids
15296 followed by a hyphen
15297 by a setting like this:
15298 .code
15299 untrusted_set_sender = ^$sender_ident-
15300 .endd
15301 If you want to allow untrusted users to set envelope sender addresses without
15302 restriction, you can use
15303 .code
15304 untrusted_set_sender = *
15305 .endd
15306 The &%untrusted_set_sender%& option applies to all forms of local input, but
15307 only to the setting of the envelope sender. It does not permit untrusted users
15308 to use the other options which trusted user can use to override message
15309 parameters. Furthermore, it does not stop Exim from removing an existing
15310 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
15311 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
15312 overriding these actions. The handling of the &'Sender:'& header is also
15313 described in section &<<SECTthesenhea>>&.
15314
15315 The log line for a message's arrival shows the envelope sender following
15316 &"<="&. For local messages, the user's login always follows, after &"U="&. In
15317 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
15318 envelope sender address, the user's login is shown in parentheses after the
15319 sender address.
15320
15321
15322 .option uucp_from_pattern main string "see below"
15323 .cindex "&""From""& line"
15324 .cindex "UUCP" "&""From""& line"
15325 Some applications that pass messages to an MTA via a command line interface use
15326 an initial line starting with &"From&~"& to pass the envelope sender. In
15327 particular, this is used by UUCP software. Exim recognizes such a line by means
15328 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
15329 matches, the sender address is constructed by expanding the contents of
15330 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
15331 default pattern recognizes lines in the following two forms:
15332 .code
15333 From ph10 Fri Jan 5 12:35 GMT 1996
15334 From ph10 Fri, 7 Jan 97 14:00:00 GMT
15335 .endd
15336 The pattern can be seen by running
15337 .code
15338 exim -bP uucp_from_pattern
15339 .endd
15340 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
15341 year in the second case. The first word after &"From&~"& is matched in the
15342 regular expression by a parenthesized subpattern. The default value for
15343 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
15344 (&"ph10"& in the example above) as the message's sender. See also
15345 &%ignore_fromline_hosts%&.
15346
15347
15348 .option uucp_from_sender main string&!! &`$1`&
15349 See &%uucp_from_pattern%& above.
15350
15351
15352 .option warn_message_file main string unset
15353 .cindex "warning of delay" "customizing the message"
15354 .cindex "customizing" "warning message"
15355 This option defines a template file containing paragraphs of text to be used
15356 for constructing the warning message which is sent by Exim when a message has
15357 been on the queue for a specified amount of time, as specified by
15358 &%delay_warning%&. Details of the file's contents are given in chapter
15359 &<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
15360
15361
15362 .option write_rejectlog main boolean true
15363 .cindex "reject log" "disabling"
15364 If this option is set false, Exim no longer writes anything to the reject log.
15365 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
15366 .ecindex IIDconfima
15367 .ecindex IIDmaiconf
15368
15369
15370
15371
15372 . ////////////////////////////////////////////////////////////////////////////
15373 . ////////////////////////////////////////////////////////////////////////////
15374
15375 .chapter "Generic options for routers" "CHAProutergeneric"
15376 .scindex IIDgenoprou1 "options" "generic; for routers"
15377 .scindex IIDgenoprou2 "generic options" "router"
15378 This chapter describes the generic options that apply to all routers.
15379 Those that are preconditions are marked with &Dagger; in the &"use"& field.
15380
15381 For a general description of how a router operates, see sections
15382 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
15383 which the preconditions are tested. The order of expansion of the options that
15384 provide data for a transport is: &%errors_to%&, &%headers_add%&,
15385 &%headers_remove%&, &%transport%&.
15386
15387
15388
15389 .option address_data routers string&!! unset
15390 .cindex "router" "data attached to address"
15391 The string is expanded just before the router is run, that is, after all the
15392 precondition tests have succeeded. If the expansion is forced to fail, the
15393 router declines, the value of &%address_data%& remains unchanged, and the
15394 &%more%& option controls what happens next. Other expansion failures cause
15395 delivery of the address to be deferred.
15396
15397 .vindex "&$address_data$&"
15398 When the expansion succeeds, the value is retained with the address, and can be
15399 accessed using the variable &$address_data$& in the current router, subsequent
15400 routers, and the eventual transport.
15401
15402 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
15403 that runs a user's filter file, the contents of &$address_data$& are accessible
15404 in the filter. This is not normally a problem, because such data is usually
15405 either not confidential or it &"belongs"& to the current user, but if you do
15406 put confidential data into &$address_data$& you need to remember this point.
15407
15408 Even if the router declines or passes, the value of &$address_data$& remains
15409 with the address, though it can be changed by another &%address_data%& setting
15410 on a subsequent router. If a router generates child addresses, the value of
15411 &$address_data$& propagates to them. This also applies to the special kind of
15412 &"child"& that is generated by a router with the &%unseen%& option.
15413
15414 The idea of &%address_data%& is that you can use it to look up a lot of data
15415 for the address once, and then pick out parts of the data later. For example,
15416 you could use a single LDAP lookup to return a string of the form
15417 .code
15418 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
15419 .endd
15420 In the transport you could pick out the mailbox by a setting such as
15421 .code
15422 file = ${extract{mailbox}{$address_data}}
15423 .endd
15424 This makes the configuration file less messy, and also reduces the number of
15425 lookups (though Exim does cache lookups).
15426
15427 .vindex "&$sender_address_data$&"
15428 .vindex "&$address_data$&"
15429 The &%address_data%& facility is also useful as a means of passing information
15430 from one router to another, and from a router to a transport. In addition, if
15431 &$address_data$& is set by a router when verifying a recipient address from an
15432 ACL, it remains available for use in the rest of the ACL statement. After
15433 verifying a sender, the value is transferred to &$sender_address_data$&.
15434
15435
15436
15437 .option address_test routers&!? boolean true
15438 .oindex "&%-bt%&"
15439 .cindex "router" "skipping when address testing"
15440 If this option is set false, the router is skipped when routing is being tested
15441 by means of the &%-bt%& command line option. This can be a convenience when
15442 your first router sends messages to an external scanner, because it saves you
15443 having to set the &"already scanned"& indicator when testing real address
15444 routing.
15445
15446
15447
15448 .option cannot_route_message routers string&!! unset
15449 .cindex "router" "customizing &""cannot route""& message"
15450 .cindex "customizing" "&""cannot route""& message"
15451 This option specifies a text message that is used when an address cannot be
15452 routed because Exim has run out of routers. The default message is
15453 &"Unrouteable address"&. This option is useful only on routers that have
15454 &%more%& set false, or on the very last router in a configuration, because the
15455 value that is used is taken from the last router that is considered. This
15456 includes a router that is skipped because its preconditions are not met, as
15457 well as a router that declines. For example, using the default configuration,
15458 you could put:
15459 .code
15460 cannot_route_message = Remote domain not found in DNS
15461 .endd
15462 on the first router, which is a &(dnslookup)& router with &%more%& set false,
15463 and
15464 .code
15465 cannot_route_message = Unknown local user
15466 .endd
15467 on the final router that checks for local users. If string expansion fails for
15468 this option, the default message is used. Unless the expansion failure was
15469 explicitly forced, a message about the failure is written to the main and panic
15470 logs, in addition to the normal message about the routing failure.
15471
15472
15473 .option caseful_local_part routers boolean false
15474 .cindex "case of local parts"
15475 .cindex "router" "case of local parts"
15476 By default, routers handle the local parts of addresses in a case-insensitive
15477 manner, though the actual case is preserved for transmission with the message.
15478 If you want the case of letters to be significant in a router, you must set
15479 this option true. For individual router options that contain address or local
15480 part lists (for example, &%local_parts%&), case-sensitive matching can be
15481 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
15482 more details.
15483
15484 .vindex "&$local_part$&"
15485 .vindex "&$original_local_part$&"
15486 .vindex "&$parent_local_part$&"
15487 The value of the &$local_part$& variable is forced to lower case while a
15488 router is running unless &%caseful_local_part%& is set. When a router assigns
15489 an address to a transport, the value of &$local_part$& when the transport runs
15490 is the same as it was in the router. Similarly, when a router generates child
15491 addresses by aliasing or forwarding, the values of &$original_local_part$&
15492 and &$parent_local_part$& are those that were used by the redirecting router.
15493
15494 This option applies to the processing of an address by a router. When a
15495 recipient address is being processed in an ACL, there is a separate &%control%&
15496 modifier that can be used to specify case-sensitive processing within the ACL
15497 (see section &<<SECTcontrols>>&).
15498
15499
15500
15501 .option check_local_user routers&!? boolean false
15502 .cindex "local user, checking in router"
15503 .cindex "router" "checking for local user"
15504 .cindex "&_/etc/passwd_&"
15505 .vindex "&$home$&"
15506 When this option is true, Exim checks that the local part of the recipient
15507 address (with affixes removed if relevant) is the name of an account on the
15508 local system. The check is done by calling the &[getpwnam()]& function rather
15509 than trying to read &_/etc/passwd_& directly. This means that other methods of
15510 holding password data (such as NIS) are supported. If the local part is a local
15511 user, &$home$& is set from the password data, and can be tested in other
15512 preconditions that are evaluated after this one (the order of evaluation is
15513 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
15514 overridden by &%router_home_directory%&. If the local part is not a local user,
15515 the router is skipped.
15516
15517 If you want to check that the local part is either the name of a local user
15518 or matches something else, you cannot combine &%check_local_user%& with a
15519 setting of &%local_parts%&, because that specifies the logical &'and'& of the
15520 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
15521 setting to achieve this. For example:
15522 .code
15523 local_parts = passwd;$local_part : lsearch;/etc/other/users
15524 .endd
15525 Note, however, that the side effects of &%check_local_user%& (such as setting
15526 up a home directory) do not occur when a &(passwd)& lookup is used in a
15527 &%local_parts%& (or any other) precondition.
15528
15529
15530
15531 .option condition routers&!? string&!! unset
15532 .cindex "router" "customized precondition"
15533 This option specifies a general precondition test that has to succeed for the
15534 router to be called. The &%condition%& option is the last precondition to be
15535 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
15536 result is a forced failure, or an empty string, or one of the strings &"0"& or
15537 &"no"& or &"false"& (checked without regard to the case of the letters), the
15538 router is skipped, and the address is offered to the next one.
15539
15540 If the result is any other value, the router is run (as this is the last
15541 precondition to be evaluated, all the other preconditions must be true).
15542
15543 The &%condition%& option provides a means of applying custom conditions to the
15544 running of routers. Note that in the case of a simple conditional expansion,
15545 the default expansion values are exactly what is wanted. For example:
15546 .code
15547 condition = ${if >{$message_age}{600}}
15548 .endd
15549 Because of the default behaviour of the string expansion, this is equivalent to
15550 .code
15551 condition = ${if >{$message_age}{600}{true}{}}
15552 .endd
15553 If the expansion fails (other than forced failure) delivery is deferred. Some
15554 of the other precondition options are common special cases that could in fact
15555 be specified using &%condition%&.
15556
15557
15558
15559 .option debug_print routers string&!! unset
15560 .cindex "testing" "variables in drivers"
15561 If this option is set and debugging is enabled (see the &%-d%& command line
15562 option), the string is expanded and included in the debugging output.
15563 If expansion of the string fails, the error message is written to the debugging
15564 output, and Exim carries on processing.
15565 This option is provided to help with checking out the values of variables and
15566 so on when debugging router configurations. For example, if a &%condition%&
15567 option appears not to be working, &%debug_print%& can be used to output the
15568 variables it references. The output happens after checks for &%domains%&,
15569 &%local_parts%&, and &%check_local_user%& but before any other preconditions
15570 are tested. A newline is added to the text if it does not end with one.
15571
15572
15573
15574 .option disable_logging routers boolean false
15575 If this option is set true, nothing is logged for any routing errors
15576 or for any deliveries caused by this router. You should not set this option
15577 unless you really, really know what you are doing. See also the generic
15578 transport option of the same name.
15579
15580
15581 .option domains routers&!? "domain list&!!" unset
15582 .cindex "router" "restricting to specific domains"
15583 .vindex "&$domain_data$&"
15584 If this option is set, the router is skipped unless the current domain matches
15585 the list. If the match is achieved by means of a file lookup, the data that the
15586 lookup returned for the domain is placed in &$domain_data$& for use in string
15587 expansions of the driver's private options. See section &<<SECTrouprecon>>& for
15588 a list of the order in which preconditions are evaluated.
15589
15590
15591
15592 .option driver routers string unset
15593 This option must always be set. It specifies which of the available routers is
15594 to be used.
15595
15596
15597
15598 .option errors_to routers string&!! unset
15599 .cindex "envelope sender"
15600 .cindex "router" "changing address for errors"
15601 If a router successfully handles an address, it may assign the address to a
15602 transport for delivery or it may generate child addresses. In both cases, if
15603 there is a delivery problem during later processing, the resulting bounce
15604 message is sent to the address that results from expanding this string,
15605 provided that the address verifies successfully. The &%errors_to%& option is
15606 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
15607
15608 The &%errors_to%& setting associated with an address can be overridden if it
15609 subsequently passes through other routers that have their own &%errors_to%&
15610 settings, or if the message is delivered by a transport with a &%return_path%&
15611 setting.
15612
15613 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
15614 the expansion fails to verify, the errors address associated with the incoming
15615 address is used. At top level, this is the envelope sender. A non-forced
15616 expansion failure causes delivery to be deferred.
15617
15618 If an address for which &%errors_to%& has been set ends up being delivered over
15619 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
15620 any bounces that are generated by other MTAs on the delivery route are also
15621 sent there. You can set &%errors_to%& to the empty string by either of these
15622 settings:
15623 .code
15624 errors_to =
15625 errors_to = ""
15626 .endd
15627 An expansion item that yields an empty string has the same effect. If you do
15628 this, a locally detected delivery error for addresses processed by this router
15629 no longer gives rise to a bounce message; the error is discarded. If the
15630 address is delivered to a remote host, the return path is set to &`<>`&, unless
15631 overridden by the &%return_path%& option on the transport.
15632
15633 .vindex "&$address_data$&"
15634 If for some reason you want to discard local errors, but use a non-empty
15635 MAIL command for remote delivery, you can preserve the original return
15636 path in &$address_data$& in the router, and reinstate it in the transport by
15637 setting &%return_path%&.
15638
15639 The most common use of &%errors_to%& is to direct mailing list bounces to the
15640 manager of the list, as described in section &<<SECTmailinglists>>&, or to
15641 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
15642
15643
15644
15645 .option expn routers&!? boolean true
15646 .cindex "address" "testing"
15647 .cindex "testing" "addresses"
15648 .cindex "EXPN" "router skipping"
15649 .cindex "router" "skipping for EXPN"
15650 If this option is turned off, the router is skipped when testing an address
15651 as a result of processing an SMTP EXPN command. You might, for example,
15652 want to turn it off on a router for users' &_.forward_& files, while leaving it
15653 on for the system alias file.
15654 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
15655 are evaluated.
15656
15657 The use of the SMTP EXPN command is controlled by an ACL (see chapter
15658 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
15659 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
15660
15661
15662
15663 .option fail_verify routers boolean false
15664 .cindex "router" "forcing verification failure"
15665 Setting this option has the effect of setting both &%fail_verify_sender%& and
15666 &%fail_verify_recipient%& to the same value.
15667
15668
15669
15670 .option fail_verify_recipient routers boolean false
15671 If this option is true and an address is accepted by this router when
15672 verifying a recipient, verification fails.
15673
15674
15675
15676 .option fail_verify_sender routers boolean false
15677 If this option is true and an address is accepted by this router when
15678 verifying a sender, verification fails.
15679
15680
15681
15682 .option fallback_hosts routers "string list" unset
15683 .cindex "router" "fallback hosts"
15684 .cindex "fallback" "hosts specified on router"
15685 String expansion is not applied to this option. The argument must be a
15686 colon-separated list of host names or IP addresses. The list separator can be
15687 changed (see section &<<SECTlistconstruct>>&), and a port can be specified with
15688 each name or address. In fact, the format of each item is exactly the same as
15689 defined for the list of hosts in a &(manualroute)& router (see section
15690 &<<SECTformatonehostitem>>&).
15691
15692 If a router queues an address for a remote transport, this host list is
15693 associated with the address, and used instead of the transport's fallback host
15694 list. If &%hosts_randomize%& is set on the transport, the order of the list is
15695 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
15696 transport for further details.
15697
15698
15699 .option group routers string&!! "see below"
15700 .cindex "gid (group id)" "local delivery"
15701 .cindex "local transports" "uid and gid"
15702 .cindex "transport" "local"
15703 .cindex "router" "setting group"
15704 When a router queues an address for a transport, and the transport does not
15705 specify a group, the group given here is used when running the delivery
15706 process.
15707 The group may be specified numerically or by name. If expansion fails, the
15708 error is logged and delivery is deferred.
15709 The default is unset, unless &%check_local_user%& is set, when the default
15710 is taken from the password information. See also &%initgroups%& and &%user%&
15711 and the discussion in chapter &<<CHAPenvironment>>&.
15712
15713
15714
15715 .option headers_add routers string&!! unset
15716 .cindex "header lines" "adding"
15717 .cindex "router" "adding header lines"
15718 This option specifies a string of text that is expanded at routing time, and
15719 associated with any addresses that are accepted by the router. However, this
15720 option has no effect when an address is just being verified. The way in which
15721 the text is used to add header lines at transport time is described in section
15722 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
15723 message is in the process of being transported. This means that references to
15724 header lines in string expansions in the transport's configuration do not
15725 &"see"& the added header lines.
15726
15727 The &%headers_add%& option is expanded after &%errors_to%&, but before
15728 &%headers_remove%& and &%transport%&. If the expanded string is empty, or if
15729 the expansion is forced to fail, the option has no effect. Other expansion
15730 failures are treated as configuration errors.
15731
15732 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
15733 router that has the &%one_time%& option set.
15734
15735 .cindex "duplicate addresses"
15736 .oindex "&%unseen%&"
15737 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
15738 additions are deleted when the address is passed on to subsequent routers.
15739 For a &%redirect%& router, if a generated address is the same as the incoming
15740 address, this can lead to duplicate addresses with different header
15741 modifications. Exim does not do duplicate deliveries (except, in certain
15742 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
15743 which of the duplicates is discarded, so this ambiguous situation should be
15744 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
15745
15746
15747
15748 .option headers_remove routers string&!! unset
15749 .cindex "header lines" "removing"
15750 .cindex "router" "removing header lines"
15751 This option specifies a string of text that is expanded at routing time, and
15752 associated with any addresses that are accepted by the router. However, this
15753 option has no effect when an address is just being verified. The way in which
15754 the text is used to remove header lines at transport time is described in
15755 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
15756 the message is in the process of being transported. This means that references
15757 to header lines in string expansions in the transport's configuration still
15758 &"see"& the original header lines.
15759
15760 The &%headers_remove%& option is expanded after &%errors_to%& and
15761 &%headers_add%&, but before &%transport%&. If the expansion is forced to fail,
15762 the option has no effect. Other expansion failures are treated as configuration
15763 errors.
15764
15765 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
15766 router that has the &%one_time%& option set.
15767
15768 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
15769 removal requests are deleted when the address is passed on to subsequent
15770 routers, and this can lead to problems with duplicates -- see the similar
15771 warning for &%headers_add%& above.
15772
15773
15774 .option ignore_target_hosts routers "host list&!!" unset
15775 .cindex "IP address" "discarding"
15776 .cindex "router" "discarding IP addresses"
15777 Although this option is a host list, it should normally contain IP address
15778 entries rather than names. If any host that is looked up by the router has an
15779 IP address that matches an item in this list, Exim behaves as if that IP
15780 address did not exist. This option allows you to cope with rogue DNS entries
15781 like
15782 .code
15783 remote.domain.example. A 127.0.0.1
15784 .endd
15785 by setting
15786 .code
15787 ignore_target_hosts = 127.0.0.1
15788 .endd
15789 on the relevant router. If all the hosts found by a &(dnslookup)& router are
15790 discarded in this way, the router declines. In a conventional configuration, an
15791 attempt to mail to such a domain would normally provoke the &"unrouteable
15792 domain"& error, and an attempt to verify an address in the domain would fail.
15793 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
15794 router declines if presented with one of the listed addresses.
15795
15796 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
15797 means of the first or the second of the following settings, respectively:
15798 .code
15799 ignore_target_hosts = 0.0.0.0/0
15800 ignore_target_hosts = <; 0::0/0
15801 .endd
15802 The pattern in the first line matches all IPv4 addresses, whereas the pattern
15803 in the second line matches all IPv6 addresses.
15804
15805 This option may also be useful for ignoring link-local and site-local IPv6
15806 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
15807 is expanded before use as a list, it is possible to make it dependent on the
15808 domain that is being routed.
15809
15810 .vindex "&$host_address$&"
15811 During its expansion, &$host_address$& is set to the IP address that is being
15812 checked.
15813
15814 .option initgroups routers boolean false
15815 .cindex "additional groups"
15816 .cindex "groups" "additional"
15817 .cindex "local transports" "uid and gid"
15818 .cindex "transport" "local"
15819 If the router queues an address for a transport, and this option is true, and
15820 the uid supplied by the router is not overridden by the transport, the
15821 &[initgroups()]& function is called when running the transport to ensure that
15822 any additional groups associated with the uid are set up. See also &%group%&
15823 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
15824
15825
15826
15827 .option local_part_prefix routers&!? "string list" unset
15828 .cindex "router" "prefix for local part"
15829 .cindex "prefix" "for local part, used in router"
15830 If this option is set, the router is skipped unless the local part starts with
15831 one of the given strings, or &%local_part_prefix_optional%& is true. See
15832 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
15833 evaluated.
15834
15835 The list is scanned from left to right, and the first prefix that matches is
15836 used. A limited form of wildcard is available; if the prefix begins with an
15837 asterisk, it matches the longest possible sequence of arbitrary characters at
15838 the start of the local part. An asterisk should therefore always be followed by
15839 some character that does not occur in normal local parts.
15840 .cindex "multiple mailboxes"
15841 .cindex "mailbox" "multiple"
15842 Wildcarding can be used to set up multiple user mailboxes, as described in
15843 section &<<SECTmulbox>>&.
15844
15845 .vindex "&$local_part$&"
15846 .vindex "&$local_part_prefix$&"
15847 During the testing of the &%local_parts%& option, and while the router is
15848 running, the prefix is removed from the local part, and is available in the
15849 expansion variable &$local_part_prefix$&. When a message is being delivered, if
15850 the router accepts the address, this remains true during subsequent delivery by
15851 a transport. In particular, the local part that is transmitted in the RCPT
15852 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
15853 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
15854 the relevant transport.
15855
15856 When an address is being verified, &%local_part_prefix%& affects only the
15857 behaviour of the router. If the callout feature of verification is in use, this
15858 means that the full address, including the prefix, will be used during the
15859 callout.
15860
15861 The prefix facility is commonly used to handle local parts of the form
15862 &%owner-something%&. Another common use is to support local parts of the form
15863 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
15864 to tell a user their forwarding is broken &-- by placing a router like this one
15865 immediately before the router that handles &_.forward_& files:
15866 .code
15867 real_localuser:
15868 driver = accept
15869 local_part_prefix = real-
15870 check_local_user
15871 transport = local_delivery
15872 .endd
15873 For security, it would probably be a good idea to restrict the use of this
15874 router to locally-generated messages, using a condition such as this:
15875 .code
15876 condition = ${if match {$sender_host_address}\
15877 {\N^(|127\.0\.0\.1)$\N}}
15878 .endd
15879
15880 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
15881 both conditions must be met if not optional. Care must be taken if wildcards
15882 are used in both a prefix and a suffix on the same router. Different
15883 separator characters must be used to avoid ambiguity.
15884
15885
15886 .option local_part_prefix_optional routers boolean false
15887 See &%local_part_prefix%& above.
15888
15889
15890
15891 .option local_part_suffix routers&!? "string list" unset
15892 .cindex "router" "suffix for local part"
15893 .cindex "suffix for local part" "used in router"
15894 This option operates in the same way as &%local_part_prefix%&, except that the
15895 local part must end (rather than start) with the given string, the
15896 &%local_part_suffix_optional%& option determines whether the suffix is
15897 mandatory, and the wildcard * character, if present, must be the last
15898 character of the suffix. This option facility is commonly used to handle local
15899 parts of the form &%something-request%& and multiple user mailboxes of the form
15900 &%username-foo%&.
15901
15902
15903 .option local_part_suffix_optional routers boolean false
15904 See &%local_part_suffix%& above.
15905
15906
15907
15908 .option local_parts routers&!? "local part list&!!" unset
15909 .cindex "router" "restricting to specific local parts"
15910 .cindex "local part" "checking in router"
15911 The router is run only if the local part of the address matches the list.
15912 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
15913 are evaluated, and
15914 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
15915 string is expanded, it is possible to make it depend on the domain, for
15916 example:
15917 .code
15918 local_parts = dbm;/usr/local/specials/$domain
15919 .endd
15920 .vindex "&$local_part_data$&"
15921 If the match is achieved by a lookup, the data that the lookup returned
15922 for the local part is placed in the variable &$local_part_data$& for use in
15923 expansions of the router's private options. You might use this option, for
15924 example, if you have a large number of local virtual domains, and you want to
15925 send all postmaster mail to the same place without having to set up an alias in
15926 each virtual domain:
15927 .code
15928 postmaster:
15929 driver = redirect
15930 local_parts = postmaster
15931 data = postmaster@real.domain.example
15932 .endd
15933
15934
15935 .option log_as_local routers boolean "see below"
15936 .cindex "log" "delivery line"
15937 .cindex "delivery" "log line format"
15938 Exim has two logging styles for delivery, the idea being to make local
15939 deliveries stand out more visibly from remote ones. In the &"local"& style, the
15940 recipient address is given just as the local part, without a domain. The use of
15941 this style is controlled by this option. It defaults to true for the &(accept)&
15942 router, and false for all the others. This option applies only when a
15943 router assigns an address to a transport. It has no effect on routers that
15944 redirect addresses.
15945
15946
15947
15948 .option more routers boolean&!! true
15949 The result of string expansion for this option must be a valid boolean value,
15950 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
15951 result causes an error, and delivery is deferred. If the expansion is forced to
15952 fail, the default value for the option (true) is used. Other failures cause
15953 delivery to be deferred.
15954
15955 If this option is set false, and the router declines to handle the address, no
15956 further routers are tried, routing fails, and the address is bounced.
15957 .oindex "&%self%&"
15958 However, if the router explicitly passes an address to the following router by
15959 means of the setting
15960 .code
15961 self = pass
15962 .endd
15963 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
15964 does not affect the behaviour if one of the precondition tests fails. In that
15965 case, the address is always passed to the next router.
15966
15967 Note that &%address_data%& is not considered to be a precondition. If its
15968 expansion is forced to fail, the router declines, and the value of &%more%&
15969 controls what happens next.
15970
15971
15972 .option pass_on_timeout routers boolean false
15973 .cindex "timeout" "of router"
15974 .cindex "router" "timeout"
15975 If a router times out during a host lookup, it normally causes deferral of the
15976 address. If &%pass_on_timeout%& is set, the address is passed on to the next
15977 router, overriding &%no_more%&. This may be helpful for systems that are
15978 intermittently connected to the Internet, or those that want to pass to a smart
15979 host any messages that cannot immediately be delivered.
15980
15981 There are occasional other temporary errors that can occur while doing DNS
15982 lookups. They are treated in the same way as a timeout, and this option
15983 applies to all of them.
15984
15985
15986
15987 .option pass_router routers string unset
15988 .cindex "router" "go to after &""pass""&"
15989 Routers that recognize the generic &%self%& option (&(dnslookup)&,
15990 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
15991 routing to continue, and overriding a false setting of &%more%&. When one of
15992 these routers returns &"pass"&, the address is normally handed on to the next
15993 router in sequence. This can be changed by setting &%pass_router%& to the name
15994 of another router. However (unlike &%redirect_router%&) the named router must
15995 be below the current router, to avoid loops. Note that this option applies only
15996 to the special case of &"pass"&. It does not apply when a router returns
15997 &"decline"& because it cannot handle an address.
15998
15999
16000
16001 .option redirect_router routers string unset
16002 .cindex "router" "start at after redirection"
16003 Sometimes an administrator knows that it is pointless to reprocess addresses
16004 generated from alias or forward files with the same router again. For
16005 example, if an alias file translates real names into login ids there is no
16006 point searching the alias file a second time, especially if it is a large file.
16007
16008 The &%redirect_router%& option can be set to the name of any router instance.
16009 It causes the routing of any generated addresses to start at the named router
16010 instead of at the first router. This option has no effect if the router in
16011 which it is set does not generate new addresses.
16012
16013
16014
16015 .option require_files routers&!? "string list&!!" unset
16016 .cindex "file" "requiring for router"
16017 .cindex "router" "requiring file existence"
16018 This option provides a general mechanism for predicating the running of a
16019 router on the existence or non-existence of certain files or directories.
16020 Before running a router, as one of its precondition tests, Exim works its way
16021 through the &%require_files%& list, expanding each item separately.
16022
16023 Because the list is split before expansion, any colons in expansion items must
16024 be doubled, or the facility for using a different list separator must be used.
16025 If any expansion is forced to fail, the item is ignored. Other expansion
16026 failures cause routing of the address to be deferred.
16027
16028 If any expanded string is empty, it is ignored. Otherwise, except as described
16029 below, each string must be a fully qualified file path, optionally preceded by
16030 &"!"&. The paths are passed to the &[stat()]& function to test for the
16031 existence of the files or directories. The router is skipped if any paths not
16032 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
16033
16034 .cindex "NFS"
16035 If &[stat()]& cannot determine whether a file exists or not, delivery of
16036 the message is deferred. This can happen when NFS-mounted filesystems are
16037 unavailable.
16038
16039 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
16040 options, so you cannot use it to check for the existence of a file in which to
16041 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
16042 full list of the order in which preconditions are evaluated.) However, as
16043 these options are all expanded, you can use the &%exists%& expansion condition
16044 to make such tests. The &%require_files%& option is intended for checking files
16045 that the router may be going to use internally, or which are needed by a
16046 transport (for example &_.procmailrc_&).
16047
16048 During delivery, the &[stat()]& function is run as root, but there is a
16049 facility for some checking of the accessibility of a file by another user.
16050 This is not a proper permissions check, but just a &"rough"& check that
16051 operates as follows:
16052
16053 If an item in a &%require_files%& list does not contain any forward slash
16054 characters, it is taken to be the user (and optional group, separated by a
16055 comma) to be checked for subsequent files in the list. If no group is specified
16056 but the user is specified symbolically, the gid associated with the uid is
16057 used. For example:
16058 .code
16059 require_files = mail:/some/file
16060 require_files = $local_part:$home/.procmailrc
16061 .endd
16062 If a user or group name in a &%require_files%& list does not exist, the
16063 &%require_files%& condition fails.
16064
16065 Exim performs the check by scanning along the components of the file path, and
16066 checking the access for the given uid and gid. It checks for &"x"& access on
16067 directories, and &"r"& access on the final file. Note that this means that file
16068 access control lists, if the operating system has them, are ignored.
16069
16070 &*Warning 1*&: When the router is being run to verify addresses for an
16071 incoming SMTP message, Exim is not running as root, but under its own uid. This
16072 may affect the result of a &%require_files%& check. In particular, &[stat()]&
16073 may yield the error EACCES (&"Permission denied"&). This means that the Exim
16074 user is not permitted to read one of the directories on the file's path.
16075
16076 &*Warning 2*&: Even when Exim is running as root while delivering a message,
16077 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
16078 without root access. In this case, if a check for access by a particular user
16079 is requested, Exim creates a subprocess that runs as that user, and tries the
16080 check again in that process.
16081
16082 The default action for handling an unresolved EACCES is to consider it to
16083 be caused by a configuration error, and routing is deferred because the
16084 existence or non-existence of the file cannot be determined. However, in some
16085 circumstances it may be desirable to treat this condition as if the file did
16086 not exist. If the file name (or the exclamation mark that precedes the file
16087 name for non-existence) is preceded by a plus sign, the EACCES error is treated
16088 as if the file did not exist. For example:
16089 .code
16090 require_files = +/some/file
16091 .endd
16092 If the router is not an essential part of verification (for example, it
16093 handles users' &_.forward_& files), another solution is to set the &%verify%&
16094 option false so that the router is skipped when verifying.
16095
16096
16097
16098 .option retry_use_local_part routers boolean "see below"
16099 .cindex "hints database" "retry keys"
16100 .cindex "local part" "in retry keys"
16101 When a delivery suffers a temporary routing failure, a retry record is created
16102 in Exim's hints database. For addresses whose routing depends only on the
16103 domain, the key for the retry record should not involve the local part, but for
16104 other addresses, both the domain and the local part should be included.
16105 Usually, remote routing is of the former kind, and local routing is of the
16106 latter kind.
16107
16108 This option controls whether the local part is used to form the key for retry
16109 hints for addresses that suffer temporary errors while being handled by this
16110 router. The default value is true for any router that has &%check_local_user%&
16111 set, and false otherwise. Note that this option does not apply to hints keys
16112 for transport delays; they are controlled by a generic transport option of the
16113 same name.
16114
16115 The setting of &%retry_use_local_part%& applies only to the router on which it
16116 appears. If the router generates child addresses, they are routed
16117 independently; this setting does not become attached to them.
16118
16119
16120
16121 .option router_home_directory routers string&!! unset
16122 .cindex "router" "home directory for"
16123 .cindex "home directory" "for router"
16124 .vindex "&$home$&"
16125 This option sets a home directory for use while the router is running. (Compare
16126 &%transport_home_directory%&, which sets a home directory for later
16127 transporting.) In particular, if used on a &(redirect)& router, this option
16128 sets a value for &$home$& while a filter is running. The value is expanded;
16129 forced expansion failure causes the option to be ignored &-- other failures
16130 cause the router to defer.
16131
16132 Expansion of &%router_home_directory%& happens immediately after the
16133 &%check_local_user%& test (if configured), before any further expansions take
16134 place.
16135 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16136 are evaluated.)
16137 While the router is running, &%router_home_directory%& overrides the value of
16138 &$home$& that came from &%check_local_user%&.
16139
16140 When a router accepts an address and assigns it to a local transport (including
16141 the cases when a &(redirect)& router generates a pipe, file, or autoreply
16142 delivery), the home directory setting for the transport is taken from the first
16143 of these values that is set:
16144
16145 .ilist
16146 The &%home_directory%& option on the transport;
16147 .next
16148 The &%transport_home_directory%& option on the router;
16149 .next
16150 The password data if &%check_local_user%& is set on the router;
16151 .next
16152 The &%router_home_directory%& option on the router.
16153 .endlist
16154
16155 In other words, &%router_home_directory%& overrides the password data for the
16156 router, but not for the transport.
16157
16158
16159
16160 .option self routers string freeze
16161 .cindex "MX record" "pointing to local host"
16162 .cindex "local host" "MX pointing to"
16163 This option applies to those routers that use a recipient address to find a
16164 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
16165 and &(manualroute)& routers.
16166 Certain configurations of the &(queryprogram)& router can also specify a list
16167 of remote hosts.
16168 Usually such routers are configured to send the message to a remote host via an
16169 &(smtp)& transport. The &%self%& option specifies what happens when the first
16170 host on the list turns out to be the local host.
16171 The way in which Exim checks for the local host is described in section
16172 &<<SECTreclocipadd>>&.
16173
16174 Normally this situation indicates either an error in Exim's configuration (for
16175 example, the router should be configured not to process this domain), or an
16176 error in the DNS (for example, the MX should not point to this host). For this
16177 reason, the default action is to log the incident, defer the address, and
16178 freeze the message. The following alternatives are provided for use in special
16179 cases:
16180
16181 .vlist
16182 .vitem &%defer%&
16183 Delivery of the message is tried again later, but the message is not frozen.
16184
16185 .vitem "&%reroute%&: <&'domain'&>"
16186 The domain is changed to the given domain, and the address is passed back to
16187 be reprocessed by the routers. No rewriting of headers takes place. This
16188 behaviour is essentially a redirection.
16189
16190 .vitem "&%reroute: rewrite:%& <&'domain'&>"
16191 The domain is changed to the given domain, and the address is passed back to be
16192 reprocessed by the routers. Any headers that contain the original domain are
16193 rewritten.
16194
16195 .vitem &%pass%&
16196 .oindex "&%more%&"
16197 .vindex "&$self_hostname$&"
16198 The router passes the address to the next router, or to the router named in the
16199 &%pass_router%& option if it is set. This overrides &%no_more%&. During
16200 subsequent routing and delivery, the variable &$self_hostname$& contains the
16201 name of the local host that the router encountered. This can be used to
16202 distinguish between different cases for hosts with multiple names. The
16203 combination
16204 .code
16205 self = pass
16206 no_more
16207 .endd
16208 ensures that only those addresses that routed to the local host are passed on.
16209 Without &%no_more%&, addresses that were declined for other reasons would also
16210 be passed to the next router.
16211
16212 .vitem &%fail%&
16213 Delivery fails and an error report is generated.
16214
16215 .vitem &%send%&
16216 .cindex "local host" "sending to"
16217 The anomaly is ignored and the address is queued for the transport. This
16218 setting should be used with extreme caution. For an &(smtp)& transport, it
16219 makes sense only in cases where the program that is listening on the SMTP port
16220 is not this version of Exim. That is, it must be some other MTA, or Exim with a
16221 different configuration file that handles the domain in another way.
16222 .endlist
16223
16224
16225
16226 .option senders routers&!? "address list&!!" unset
16227 .cindex "router" "checking senders"
16228 If this option is set, the router is skipped unless the message's sender
16229 address matches something on the list.
16230 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16231 are evaluated.
16232
16233 There are issues concerning verification when the running of routers is
16234 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
16235 setting, it sets the sender to the null string. When using the &%-bt%& option
16236 to check a configuration file, it is necessary also to use the &%-f%& option to
16237 set an appropriate sender. For incoming mail, the sender is unset when
16238 verifying the sender, but is available when verifying any recipients. If the
16239 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
16240 matters.
16241
16242
16243 .option translate_ip_address routers string&!! unset
16244 .cindex "IP address" "translating"
16245 .cindex "packet radio"
16246 .cindex "router" "IP address translation"
16247 There exist some rare networking situations (for example, packet radio) where
16248 it is helpful to be able to translate IP addresses generated by normal routing
16249 mechanisms into other IP addresses, thus performing a kind of manual IP
16250 routing. This should be done only if the normal IP routing of the TCP/IP stack
16251 is inadequate or broken. Because this is an extremely uncommon requirement, the
16252 code to support this option is not included in the Exim binary unless
16253 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
16254
16255 .vindex "&$host_address$&"
16256 The &%translate_ip_address%& string is expanded for every IP address generated
16257 by the router, with the generated address set in &$host_address$&. If the
16258 expansion is forced to fail, no action is taken.
16259 For any other expansion error, delivery of the message is deferred.
16260 If the result of the expansion is an IP address, that replaces the original
16261 address; otherwise the result is assumed to be a host name &-- this is looked
16262 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
16263 produce one or more replacement IP addresses. For example, to subvert all IP
16264 addresses in some specific networks, this could be added to a router:
16265 .code
16266 translate_ip_address = \
16267 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
16268 {$value}fail}}
16269 .endd
16270 The file would contain lines like
16271 .code
16272 10.2.3.128/26 some.host
16273 10.8.4.34/26 10.44.8.15
16274 .endd
16275 You should not make use of this facility unless you really understand what you
16276 are doing.
16277
16278
16279
16280 .option transport routers string&!! unset
16281 This option specifies the transport to be used when a router accepts an address
16282 and sets it up for delivery. A transport is never needed if a router is used
16283 only for verification. The value of the option is expanded at routing time,
16284 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
16285 and result must be the name of one of the configured transports. If it is not,
16286 delivery is deferred.
16287
16288 The &%transport%& option is not used by the &(redirect)& router, but it does
16289 have some private options that set up transports for pipe and file deliveries
16290 (see chapter &<<CHAPredirect>>&).
16291
16292
16293
16294 .option transport_current_directory routers string&!! unset
16295 .cindex "current directory for local transport"
16296 This option associates a current directory with any address that is routed
16297 to a local transport. This can happen either because a transport is
16298 explicitly configured for the router, or because it generates a delivery to a
16299 file or a pipe. During the delivery process (that is, at transport time), this
16300 option string is expanded and is set as the current directory, unless
16301 overridden by a setting on the transport.
16302 If the expansion fails for any reason, including forced failure, an error is
16303 logged, and delivery is deferred.
16304 See chapter &<<CHAPenvironment>>& for details of the local delivery
16305 environment.
16306
16307
16308
16309
16310 .option transport_home_directory routers string&!! "see below"
16311 .cindex "home directory" "for local transport"
16312 This option associates a home directory with any address that is routed to a
16313 local transport. This can happen either because a transport is explicitly
16314 configured for the router, or because it generates a delivery to a file or a
16315 pipe. During the delivery process (that is, at transport time), the option
16316 string is expanded and is set as the home directory, unless overridden by a
16317 setting of &%home_directory%& on the transport.
16318 If the expansion fails for any reason, including forced failure, an error is
16319 logged, and delivery is deferred.
16320
16321 If the transport does not specify a home directory, and
16322 &%transport_home_directory%& is not set for the router, the home directory for
16323 the transport is taken from the password data if &%check_local_user%& is set for
16324 the router. Otherwise it is taken from &%router_home_directory%& if that option
16325 is set; if not, no home directory is set for the transport.
16326
16327 See chapter &<<CHAPenvironment>>& for further details of the local delivery
16328 environment.
16329
16330
16331
16332
16333 .option unseen routers boolean&!! false
16334 .cindex "router" "carrying on after success"
16335 The result of string expansion for this option must be a valid boolean value,
16336 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
16337 result causes an error, and delivery is deferred. If the expansion is forced to
16338 fail, the default value for the option (false) is used. Other failures cause
16339 delivery to be deferred.
16340
16341 When this option is set true, routing does not cease if the router accepts the
16342 address. Instead, a copy of the incoming address is passed to the next router,
16343 overriding a false setting of &%more%&. There is little point in setting
16344 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
16345 the value of &%unseen%& contains expansion items (and therefore, presumably, is
16346 sometimes true and sometimes false).
16347
16348 .cindex "copy of message (&%unseen%& option)"
16349 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
16350 qualifier in filter files. It can be used to cause copies of messages to be
16351 delivered to some other destination, while also carrying out a normal delivery.
16352 In effect, the current address is made into a &"parent"& that has two children
16353 &-- one that is delivered as specified by this router, and a clone that goes on
16354 to be routed further. For this reason, &%unseen%& may not be combined with the
16355 &%one_time%& option in a &(redirect)& router.
16356
16357 &*Warning*&: Header lines added to the address (or specified for removal) by
16358 this router or by previous routers affect the &"unseen"& copy of the message
16359 only. The clone that continues to be processed by further routers starts with
16360 no added headers and none specified for removal. For a &%redirect%& router, if
16361 a generated address is the same as the incoming address, this can lead to
16362 duplicate addresses with different header modifications. Exim does not do
16363 duplicate deliveries (except, in certain circumstances, to pipes -- see section
16364 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
16365 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
16366 &%redirect%& router may be of help.
16367
16368 Unlike the handling of header modifications, any data that was set by the
16369 &%address_data%& option in the current or previous routers &'is'& passed on to
16370 subsequent routers.
16371
16372
16373 .option user routers string&!! "see below"
16374 .cindex "uid (user id)" "local delivery"
16375 .cindex "local transports" "uid and gid"
16376 .cindex "transport" "local"
16377 .cindex "router" "user for filter processing"
16378 .cindex "filter" "user for processing"
16379 When a router queues an address for a transport, and the transport does not
16380 specify a user, the user given here is used when running the delivery process.
16381 The user may be specified numerically or by name. If expansion fails, the
16382 error is logged and delivery is deferred.
16383 This user is also used by the &(redirect)& router when running a filter file.
16384 The default is unset, except when &%check_local_user%& is set. In this case,
16385 the default is taken from the password information. If the user is specified as
16386 a name, and &%group%& is not set, the group associated with the user is used.
16387 See also &%initgroups%& and &%group%& and the discussion in chapter
16388 &<<CHAPenvironment>>&.
16389
16390
16391
16392 .option verify routers&!? boolean true
16393 Setting this option has the effect of setting &%verify_sender%& and
16394 &%verify_recipient%& to the same value.
16395
16396
16397 .option verify_only routers&!? boolean false
16398 .cindex "EXPN" "with &%verify_only%&"
16399 .oindex "&%-bv%&"
16400 .cindex "router" "used only when verifying"
16401 If this option is set, the router is used only when verifying an address or
16402 testing with the &%-bv%& option, not when actually doing a delivery, testing
16403 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
16404 restricted to verifying only senders or recipients by means of
16405 &%verify_sender%& and &%verify_recipient%&.
16406
16407 &*Warning*&: When the router is being run to verify addresses for an incoming
16408 SMTP message, Exim is not running as root, but under its own uid. If the router
16409 accesses any files, you need to make sure that they are accessible to the Exim
16410 user or group.
16411
16412
16413 .option verify_recipient routers&!? boolean true
16414 If this option is false, the router is skipped when verifying recipient
16415 addresses
16416 or testing recipient verification using &%-bv%&.
16417 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16418 are evaluated.
16419
16420
16421 .option verify_sender routers&!? boolean true
16422 If this option is false, the router is skipped when verifying sender addresses
16423 or testing sender verification using &%-bvs%&.
16424 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16425 are evaluated.
16426 .ecindex IIDgenoprou1
16427 .ecindex IIDgenoprou2
16428
16429
16430
16431
16432
16433
16434 . ////////////////////////////////////////////////////////////////////////////
16435 . ////////////////////////////////////////////////////////////////////////////
16436
16437 .chapter "The accept router" "CHID4"
16438 .cindex "&(accept)& router"
16439 .cindex "routers" "&(accept)&"
16440 The &(accept)& router has no private options of its own. Unless it is being
16441 used purely for verification (see &%verify_only%&) a transport is required to
16442 be defined by the generic &%transport%& option. If the preconditions that are
16443 specified by generic options are met, the router accepts the address and queues
16444 it for the given transport. The most common use of this router is for setting
16445 up deliveries to local mailboxes. For example:
16446 .code
16447 localusers:
16448 driver = accept
16449 domains = mydomain.example
16450 check_local_user
16451 transport = local_delivery
16452 .endd
16453 The &%domains%& condition in this example checks the domain of the address, and
16454 &%check_local_user%& checks that the local part is the login of a local user.
16455 When both preconditions are met, the &(accept)& router runs, and queues the
16456 address for the &(local_delivery)& transport.
16457
16458
16459
16460
16461
16462
16463 . ////////////////////////////////////////////////////////////////////////////
16464 . ////////////////////////////////////////////////////////////////////////////
16465
16466 .chapter "The dnslookup router" "CHAPdnslookup"
16467 .scindex IIDdnsrou1 "&(dnslookup)& router"
16468 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
16469 The &(dnslookup)& router looks up the hosts that handle mail for the
16470 recipient's domain in the DNS. A transport must always be set for this router,
16471 unless &%verify_only%& is set.
16472
16473 If SRV support is configured (see &%check_srv%& below), Exim first searches for
16474 SRV records. If none are found, or if SRV support is not configured,
16475 MX records are looked up. If no MX records exist, address records are sought.
16476 However, &%mx_domains%& can be set to disable the direct use of address
16477 records.
16478
16479 MX records of equal priority are sorted by Exim into a random order. Exim then
16480 looks for address records for the host names obtained from MX or SRV records.
16481 When a host has more than one IP address, they are sorted into a random order,
16482 except that IPv6 addresses are always sorted before IPv4 addresses. If all the
16483 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
16484 generic option, the router declines.
16485
16486 Unless they have the highest priority (lowest MX value), MX records that point
16487 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
16488 are discarded, together with any other MX records of equal or lower priority.
16489
16490 .cindex "MX record" "pointing to local host"
16491 .cindex "local host" "MX pointing to"
16492 .oindex "&%self%&" "in &(dnslookup)& router"
16493 If the host pointed to by the highest priority MX record, or looked up as an
16494 address record, is the local host, or matches &%hosts_treat_as_local%&, what
16495 happens is controlled by the generic &%self%& option.
16496
16497
16498 .section "Problems with DNS lookups" "SECTprowitdnsloo"
16499 There have been problems with DNS servers when SRV records are looked up.
16500 Some mis-behaving servers return a DNS error or timeout when a non-existent
16501 SRV record is sought. Similar problems have in the past been reported for
16502 MX records. The global &%dns_again_means_nonexist%& option can help with this
16503 problem, but it is heavy-handed because it is a global option.
16504
16505 For this reason, there are two options, &%srv_fail_domains%& and
16506 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
16507 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
16508 an attempt to look up an SRV or MX record causes one of these results, and the
16509 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
16510 such record"&. In the case of an SRV lookup, this means that the router
16511 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
16512 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
16513 case routing fails.
16514
16515
16516
16517
16518 .section "Private options for dnslookup" "SECID118"
16519 .cindex "options" "&(dnslookup)& router"
16520 The private options for the &(dnslookup)& router are as follows:
16521
16522 .option check_secondary_mx dnslookup boolean false
16523 .cindex "MX record" "checking for secondary"
16524 If this option is set, the router declines unless the local host is found in
16525 (and removed from) the list of hosts obtained by MX lookup. This can be used to
16526 process domains for which the local host is a secondary mail exchanger
16527 differently to other domains. The way in which Exim decides whether a host is
16528 the local host is described in section &<<SECTreclocipadd>>&.
16529
16530
16531 .option check_srv dnslookup string&!! unset
16532 .cindex "SRV record" "enabling use of"
16533 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
16534 addition to MX and address records. The support is disabled by default. To
16535 enable SRV support, set the &%check_srv%& option to the name of the service
16536 required. For example,
16537 .code
16538 check_srv = smtp
16539 .endd
16540 looks for SRV records that refer to the normal smtp service. The option is
16541 expanded, so the service name can vary from message to message or address
16542 to address. This might be helpful if SRV records are being used for a
16543 submission service. If the expansion is forced to fail, the &%check_srv%&
16544 option is ignored, and the router proceeds to look for MX records in the
16545 normal way.
16546
16547 When the expansion succeeds, the router searches first for SRV records for
16548 the given service (it assumes TCP protocol). A single SRV record with a
16549 host name that consists of just a single dot indicates &"no such service for
16550 this domain"&; if this is encountered, the router declines. If other kinds of
16551 SRV record are found, they are used to construct a host list for delivery
16552 according to the rules of RFC 2782. MX records are not sought in this case.
16553
16554 When no SRV records are found, MX records (and address records) are sought in
16555 the traditional way. In other words, SRV records take precedence over MX
16556 records, just as MX records take precedence over address records. Note that
16557 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
16558 defined it. It is apparently believed that MX records are sufficient for email
16559 and that SRV records should not be used for this purpose. However, SRV records
16560 have an additional &"weight"& feature which some people might find useful when
16561 trying to split an SMTP load between hosts of different power.
16562
16563 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
16564 when there is a DNS lookup error.
16565
16566
16567
16568 .option mx_domains dnslookup "domain list&!!" unset
16569 .cindex "MX record" "required to exist"
16570 .cindex "SRV record" "required to exist"
16571 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
16572 record in order to be recognized. (The name of this option could be improved.)
16573 For example, if all the mail hosts in &'fict.example'& are known to have MX
16574 records, except for those in &'discworld.fict.example'&, you could use this
16575 setting:
16576 .code
16577 mx_domains = ! *.discworld.fict.example : *.fict.example
16578 .endd
16579 This specifies that messages addressed to a domain that matches the list but
16580 has no MX record should be bounced immediately instead of being routed using
16581 the address record.
16582
16583
16584 .option mx_fail_domains dnslookup "domain list&!!" unset
16585 If the DNS lookup for MX records for one of the domains in this list causes a
16586 DNS lookup error, Exim behaves as if no MX records were found. See section
16587 &<<SECTprowitdnsloo>>& for more discussion.
16588
16589
16590
16591
16592 .option qualify_single dnslookup boolean true
16593 .cindex "DNS" "resolver options"
16594 .cindex "DNS" "qualifying single-component names"
16595 When this option is true, the resolver option RES_DEFNAMES is set for DNS
16596 lookups. Typically, but not standardly, this causes the resolver to qualify
16597 single-component names with the default domain. For example, on a machine
16598 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
16599 &'thesaurus.ref.example'& inside the resolver. For details of what your
16600 resolver actually does, consult your man pages for &'resolver'& and
16601 &'resolv.conf'&.
16602
16603
16604
16605 .option rewrite_headers dnslookup boolean true
16606 .cindex "rewriting" "header lines"
16607 .cindex "header lines" "rewriting"
16608 If the domain name in the address that is being processed is not fully
16609 qualified, it may be expanded to its full form by a DNS lookup. For example, if
16610 an address is specified as &'dormouse@teaparty'&, the domain might be
16611 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
16612 occur as a result of setting the &%widen_domains%& option. If
16613 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
16614 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
16615 header lines of the message are rewritten with the full domain name.
16616
16617 This option should be turned off only when it is known that no message is
16618 ever going to be sent outside an environment where the abbreviation makes
16619 sense.
16620
16621 When an MX record is looked up in the DNS and matches a wildcard record, name
16622 servers normally return a record containing the name that has been looked up,
16623 making it impossible to detect whether a wildcard was present or not. However,
16624 some name servers have recently been seen to return the wildcard entry. If the
16625 name returned by a DNS lookup begins with an asterisk, it is not used for
16626 header rewriting.
16627
16628
16629 .option same_domain_copy_routing dnslookup boolean false
16630 .cindex "address" "copying routing"
16631 Addresses with the same domain are normally routed by the &(dnslookup)& router
16632 to the same list of hosts. However, this cannot be presumed, because the router
16633 options and preconditions may refer to the local part of the address. By
16634 default, therefore, Exim routes each address in a message independently. DNS
16635 servers run caches, so repeated DNS lookups are not normally expensive, and in
16636 any case, personal messages rarely have more than a few recipients.
16637
16638 If you are running mailing lists with large numbers of subscribers at the same
16639 domain, and you are using a &(dnslookup)& router which is independent of the
16640 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
16641 lookups for identical domains in one message. In this case, when &(dnslookup)&
16642 routes an address to a remote transport, any other unrouted addresses in the
16643 message that have the same domain are automatically given the same routing
16644 without processing them independently,
16645 provided the following conditions are met:
16646
16647 .ilist
16648 No router that processed the address specified &%headers_add%& or
16649 &%headers_remove%&.
16650 .next
16651 The router did not change the address in any way, for example, by &"widening"&
16652 the domain.
16653 .endlist
16654
16655
16656
16657
16658 .option search_parents dnslookup boolean false
16659 .cindex "DNS" "resolver options"
16660 When this option is true, the resolver option RES_DNSRCH is set for DNS
16661 lookups. This is different from the &%qualify_single%& option in that it
16662 applies to domains containing dots. Typically, but not standardly, it causes
16663 the resolver to search for the name in the current domain and in parent
16664 domains. For example, on a machine in the &'fict.example'& domain, if looking
16665 up &'teaparty.wonderland'& failed, the resolver would try
16666 &'teaparty.wonderland.fict.example'&. For details of what your resolver
16667 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
16668
16669 Setting this option true can cause problems in domains that have a wildcard MX
16670 record, because any domain that does not have its own MX record matches the
16671 local wildcard.
16672
16673
16674
16675 .option srv_fail_domains dnslookup "domain list&!!" unset
16676 If the DNS lookup for SRV records for one of the domains in this list causes a
16677 DNS lookup error, Exim behaves as if no SRV records were found. See section
16678 &<<SECTprowitdnsloo>>& for more discussion.
16679
16680
16681
16682
16683 .option widen_domains dnslookup "string list" unset
16684 .cindex "domain" "partial; widening"
16685 If a DNS lookup fails and this option is set, each of its strings in turn is
16686 added onto the end of the domain, and the lookup is tried again. For example,
16687 if
16688 .code
16689 widen_domains = fict.example:ref.example
16690 .endd
16691 is set and a lookup of &'klingon.dictionary'& fails,
16692 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
16693 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
16694 and &%search_parents%& options can cause some widening to be undertaken inside
16695 the DNS resolver. &%widen_domains%& is not applied to sender addresses
16696 when verifying, unless &%rewrite_headers%& is false (not the default).
16697
16698
16699 .section "Effect of qualify_single and search_parents" "SECID119"
16700 When a domain from an envelope recipient is changed by the resolver as a result
16701 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
16702 corresponding address in the message's header lines unless &%rewrite_headers%&
16703 is set false. Exim then re-routes the address, using the full domain.
16704
16705 These two options affect only the DNS lookup that takes place inside the router
16706 for the domain of the address that is being routed. They do not affect lookups
16707 such as that implied by
16708 .code
16709 domains = @mx_any
16710 .endd
16711 that may happen while processing a router precondition before the router is
16712 entered. No widening ever takes place for these lookups.
16713 .ecindex IIDdnsrou1
16714 .ecindex IIDdnsrou2
16715
16716
16717
16718
16719
16720
16721
16722
16723
16724 . ////////////////////////////////////////////////////////////////////////////
16725 . ////////////////////////////////////////////////////////////////////////////
16726
16727 .chapter "The ipliteral router" "CHID5"
16728 .cindex "&(ipliteral)& router"
16729 .cindex "domain literal" "routing"
16730 .cindex "routers" "&(ipliteral)&"
16731 This router has no private options. Unless it is being used purely for
16732 verification (see &%verify_only%&) a transport is required to be defined by the
16733 generic &%transport%& option. The router accepts the address if its domain part
16734 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
16735 router handles the address
16736 .code
16737 root@[192.168.1.1]
16738 .endd
16739 by setting up delivery to the host with that IP address. IPv4 domain literals
16740 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
16741 are similar, but the address is preceded by &`ipv6:`&. For example:
16742 .code
16743 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
16744 .endd
16745 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
16746 grounds that sooner or later somebody will try it.
16747
16748 .oindex "&%self%&" "in &(ipliteral)& router"
16749 If the IP address matches something in &%ignore_target_hosts%&, the router
16750 declines. If an IP literal turns out to refer to the local host, the generic
16751 &%self%& option determines what happens.
16752
16753 The RFCs require support for domain literals; however, their use is
16754 controversial in today's Internet. If you want to use this router, you must
16755 also set the main configuration option &%allow_domain_literals%&. Otherwise,
16756 Exim will not recognize the domain literal syntax in addresses.
16757
16758
16759
16760 . ////////////////////////////////////////////////////////////////////////////
16761 . ////////////////////////////////////////////////////////////////////////////
16762
16763 .chapter "The iplookup router" "CHID6"
16764 .cindex "&(iplookup)& router"
16765 .cindex "routers" "&(iplookup)&"
16766 The &(iplookup)& router was written to fulfil a specific requirement in
16767 Cambridge University (which in fact no longer exists). For this reason, it is
16768 not included in the binary of Exim by default. If you want to include it, you
16769 must set
16770 .code
16771 ROUTER_IPLOOKUP=yes
16772 .endd
16773 in your &_Local/Makefile_& configuration file.
16774
16775 The &(iplookup)& router routes an address by sending it over a TCP or UDP
16776 connection to one or more specific hosts. The host can then return the same or
16777 a different address &-- in effect rewriting the recipient address in the
16778 message's envelope. The new address is then passed on to subsequent routers. If
16779 this process fails, the address can be passed on to other routers, or delivery
16780 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
16781 must not be specified for it.
16782
16783 .cindex "options" "&(iplookup)& router"
16784 .option hosts iplookup string unset
16785 This option must be supplied. Its value is a colon-separated list of host
16786 names. The hosts are looked up using &[gethostbyname()]&
16787 (or &[getipnodebyname()]& when available)
16788 and are tried in order until one responds to the query. If none respond, what
16789 happens is controlled by &%optional%&.
16790
16791
16792 .option optional iplookup boolean false
16793 If &%optional%& is true, if no response is obtained from any host, the address
16794 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
16795 delivery to the address is deferred.
16796
16797
16798 .option port iplookup integer 0
16799 .cindex "port" "&(iplookup)& router"
16800 This option must be supplied. It specifies the port number for the TCP or UDP
16801 call.
16802
16803
16804 .option protocol iplookup string udp
16805 This option can be set to &"udp"& or &"tcp"& to specify which of the two
16806 protocols is to be used.
16807
16808
16809 .option query iplookup string&!! "see below"
16810 This defines the content of the query that is sent to the remote hosts. The
16811 default value is:
16812 .code
16813 $local_part@$domain $local_part@$domain
16814 .endd
16815 The repetition serves as a way of checking that a response is to the correct
16816 query in the default case (see &%response_pattern%& below).
16817
16818
16819 .option reroute iplookup string&!! unset
16820 If this option is not set, the rerouted address is precisely the byte string
16821 returned by the remote host, up to the first white space, if any. If set, the
16822 string is expanded to form the rerouted address. It can include parts matched
16823 in the response by &%response_pattern%& by means of numeric variables such as
16824 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
16825 whether or not a pattern is in use. In all cases, the rerouted address must end
16826 up in the form &'local_part@domain'&.
16827
16828
16829 .option response_pattern iplookup string unset
16830 This option can be set to a regular expression that is applied to the string
16831 returned from the remote host. If the pattern does not match the response, the
16832 router declines. If &%response_pattern%& is not set, no checking of the
16833 response is done, unless the query was defaulted, in which case there is a
16834 check that the text returned after the first white space is the original
16835 address. This checks that the answer that has been received is in response to
16836 the correct question. For example, if the response is just a new domain, the
16837 following could be used:
16838 .code
16839 response_pattern = ^([^@]+)$
16840 reroute = $local_part@$1
16841 .endd
16842
16843 .option timeout iplookup time 5s
16844 This specifies the amount of time to wait for a response from the remote
16845 machine. The same timeout is used for the &[connect()]& function for a TCP
16846 call. It does not apply to UDP.
16847
16848
16849
16850
16851 . ////////////////////////////////////////////////////////////////////////////
16852 . ////////////////////////////////////////////////////////////////////////////
16853
16854 .chapter "The manualroute router" "CHID7"
16855 .scindex IIDmanrou1 "&(manualroute)& router"
16856 .scindex IIDmanrou2 "routers" "&(manualroute)&"
16857 .cindex "domain" "manually routing"
16858 The &(manualroute)& router is so-called because it provides a way of manually
16859 routing an address according to its domain. It is mainly used when you want to
16860 route addresses to remote hosts according to your own rules, bypassing the
16861 normal DNS routing that looks up MX records. However, &(manualroute)& can also
16862 route to local transports, a facility that may be useful if you want to save
16863 messages for dial-in hosts in local files.
16864
16865 The &(manualroute)& router compares a list of domain patterns with the domain
16866 it is trying to route. If there is no match, the router declines. Each pattern
16867 has associated with it a list of hosts and some other optional data, which may
16868 include a transport. The combination of a pattern and its data is called a
16869 &"routing rule"&. For patterns that do not have an associated transport, the
16870 generic &%transport%& option must specify a transport, unless the router is
16871 being used purely for verification (see &%verify_only%&).
16872
16873 .vindex "&$host$&"
16874 In the case of verification, matching the domain pattern is sufficient for the
16875 router to accept the address. When actually routing an address for delivery,
16876 an address that matches a domain pattern is queued for the associated
16877 transport. If the transport is not a local one, a host list must be associated
16878 with the pattern; IP addresses are looked up for the hosts, and these are
16879 passed to the transport along with the mail address. For local transports, a
16880 host list is optional. If it is present, it is passed in &$host$& as a single
16881 text string.
16882
16883 The list of routing rules can be provided as an inline string in
16884 &%route_list%&, or the data can be obtained by looking up the domain in a file
16885 or database by setting &%route_data%&. Only one of these settings may appear in
16886 any one instance of &(manualroute)&. The format of routing rules is described
16887 below, following the list of private options.
16888
16889
16890 .section "Private options for manualroute" "SECTprioptman"
16891
16892 .cindex "options" "&(manualroute)& router"
16893 The private options for the &(manualroute)& router are as follows:
16894
16895 .option host_all_ignored manualroute string defer
16896 See &%host_find_failed%&.
16897
16898 .option host_find_failed manualroute string freeze
16899 This option controls what happens when &(manualroute)& tries to find an IP
16900 address for a host, and the host does not exist. The option can be set to one
16901 of the following values:
16902 .code
16903 decline
16904 defer
16905 fail
16906 freeze
16907 ignore
16908 pass
16909 .endd
16910 The default (&"freeze"&) assumes that this state is a serious configuration
16911 error. The difference between &"pass"& and &"decline"& is that the former
16912 forces the address to be passed to the next router (or the router defined by
16913 &%pass_router%&),
16914 .oindex "&%more%&"
16915 overriding &%no_more%&, whereas the latter passes the address to the next
16916 router only if &%more%& is true.
16917
16918 The value &"ignore"& causes Exim to completely ignore a host whose IP address
16919 cannot be found. If all the hosts in the list are ignored, the behaviour is
16920 controlled by the &%host_all_ignored%& option. This takes the same values
16921 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
16922
16923 The &%host_find_failed%& option applies only to a definite &"does not exist"&
16924 state; if a host lookup gets a temporary error, delivery is deferred unless the
16925 generic &%pass_on_timeout%& option is set.
16926
16927
16928 .option hosts_randomize manualroute boolean false
16929 .cindex "randomized host list"
16930 .cindex "host" "list of; randomized"
16931 If this option is set, the order of the items in a host list in a routing rule
16932 is randomized each time the list is used, unless an option in the routing rule
16933 overrides (see below). Randomizing the order of a host list can be used to do
16934 crude load sharing. However, if more than one mail address is routed by the
16935 same router to the same host list, the host lists are considered to be the same
16936 (even though they may be randomized into different orders) for the purpose of
16937 deciding whether to batch the deliveries into a single SMTP transaction.
16938
16939 When &%hosts_randomize%& is true, a host list may be split
16940 into groups whose order is separately randomized. This makes it possible to
16941 set up MX-like behaviour. The boundaries between groups are indicated by an
16942 item that is just &`+`& in the host list. For example:
16943 .code
16944 route_list = * host1:host2:host3:+:host4:host5
16945 .endd
16946 The order of the first three hosts and the order of the last two hosts is
16947 randomized for each use, but the first three always end up before the last two.
16948 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
16949 randomized host list is passed to an &(smtp)& transport that also has
16950 &%hosts_randomize set%&, the list is not re-randomized.
16951
16952
16953 .option route_data manualroute string&!! unset
16954 If this option is set, it must expand to yield the data part of a routing rule.
16955 Typically, the expansion string includes a lookup based on the domain. For
16956 example:
16957 .code
16958 route_data = ${lookup{$domain}dbm{/etc/routes}}
16959 .endd
16960 If the expansion is forced to fail, or the result is an empty string, the
16961 router declines. Other kinds of expansion failure cause delivery to be
16962 deferred.
16963
16964
16965 .option route_list manualroute "string list" unset
16966 This string is a list of routing rules, in the form defined below. Note that,
16967 unlike most string lists, the items are separated by semicolons. This is so
16968 that they may contain colon-separated host lists.
16969
16970
16971 .option same_domain_copy_routing manualroute boolean false
16972 .cindex "address" "copying routing"
16973 Addresses with the same domain are normally routed by the &(manualroute)&
16974 router to the same list of hosts. However, this cannot be presumed, because the
16975 router options and preconditions may refer to the local part of the address. By
16976 default, therefore, Exim routes each address in a message independently. DNS
16977 servers run caches, so repeated DNS lookups are not normally expensive, and in
16978 any case, personal messages rarely have more than a few recipients.
16979
16980 If you are running mailing lists with large numbers of subscribers at the same
16981 domain, and you are using a &(manualroute)& router which is independent of the
16982 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
16983 lookups for identical domains in one message. In this case, when
16984 &(manualroute)& routes an address to a remote transport, any other unrouted
16985 addresses in the message that have the same domain are automatically given the
16986 same routing without processing them independently. However, this is only done
16987 if &%headers_add%& and &%headers_remove%& are unset.
16988
16989
16990
16991
16992 .section "Routing rules in route_list" "SECID120"
16993 The value of &%route_list%& is a string consisting of a sequence of routing
16994 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
16995 entered as two semicolons. Alternatively, the list separator can be changed as
16996 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
16997 Empty rules are ignored. The format of each rule is
16998 .display
16999 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
17000 .endd
17001 The following example contains two rules, each with a simple domain pattern and
17002 no options:
17003 .code
17004 route_list = \
17005 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
17006 thes.ref.example mail-3.ref.example:mail-4.ref.example
17007 .endd
17008 The three parts of a rule are separated by white space. The pattern and the
17009 list of hosts can be enclosed in quotes if necessary, and if they are, the
17010 usual quoting rules apply. Each rule in a &%route_list%& must start with a
17011 single domain pattern, which is the only mandatory item in the rule. The
17012 pattern is in the same format as one item in a domain list (see section
17013 &<<SECTdomainlist>>&),
17014 except that it may not be the name of an interpolated file.
17015 That is, it may be wildcarded, or a regular expression, or a file or database
17016 lookup (with semicolons doubled, because of the use of semicolon as a separator
17017 in a &%route_list%&).
17018
17019 The rules in &%route_list%& are searched in order until one of the patterns
17020 matches the domain that is being routed. The list of hosts and then options are
17021 then used as described below. If there is no match, the router declines. When
17022 &%route_list%& is set, &%route_data%& must not be set.
17023
17024
17025
17026 .section "Routing rules in route_data" "SECID121"
17027 The use of &%route_list%& is convenient when there are only a small number of
17028 routing rules. For larger numbers, it is easier to use a file or database to
17029 hold the routing information, and use the &%route_data%& option instead.
17030 The value of &%route_data%& is a list of hosts, followed by (optional) options.
17031 Most commonly, &%route_data%& is set as a string that contains an
17032 expansion lookup. For example, suppose we place two routing rules in a file
17033 like this:
17034 .code
17035 dict.ref.example: mail-1.ref.example:mail-2.ref.example
17036 thes.ref.example: mail-3.ref.example:mail-4.ref.example
17037 .endd
17038 This data can be accessed by setting
17039 .code
17040 route_data = ${lookup{$domain}lsearch{/the/file/name}}
17041 .endd
17042 Failure of the lookup results in an empty string, causing the router to
17043 decline. However, you do not have to use a lookup in &%route_data%&. The only
17044 requirement is that the result of expanding the string is a list of hosts,
17045 possibly followed by options, separated by white space. The list of hosts must
17046 be enclosed in quotes if it contains white space.
17047
17048
17049
17050
17051 .section "Format of the list of hosts" "SECID122"
17052 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
17053 always separately expanded before use. If the expansion fails, the router
17054 declines. The result of the expansion must be a colon-separated list of names
17055 and/or IP addresses, optionally also including ports. The format of each item
17056 in the list is described in the next section. The list separator can be changed
17057 as described in section &<<SECTlistconstruct>>&.
17058
17059 If the list of hosts was obtained from a &%route_list%& item, the following
17060 variables are set during its expansion:
17061
17062 .ilist
17063 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
17064 If the domain was matched against a regular expression, the numeric variables
17065 &$1$&, &$2$&, etc. may be set. For example:
17066 .code
17067 route_list = ^domain(\d+) host-$1.text.example
17068 .endd
17069 .next
17070 &$0$& is always set to the entire domain.
17071 .next
17072 &$1$& is also set when partial matching is done in a file lookup.
17073
17074 .next
17075 .vindex "&$value$&"
17076 If the pattern that matched the domain was a lookup item, the data that was
17077 looked up is available in the expansion variable &$value$&. For example:
17078 .code
17079 route_list = lsearch;;/some/file.routes $value
17080 .endd
17081 .endlist
17082
17083 Note the doubling of the semicolon in the pattern that is necessary because
17084 semicolon is the default route list separator.
17085
17086
17087
17088 .section "Format of one host item" "SECTformatonehostitem"
17089 Each item in the list of hosts is either a host name or an IP address,
17090 optionally with an attached port number. When no port is given, an IP address
17091 is not enclosed in brackets. When a port is specified, it overrides the port
17092 specification on the transport. The port is separated from the name or address
17093 by a colon. This leads to some complications:
17094
17095 .ilist
17096 Because colon is the default separator for the list of hosts, either
17097 the colon that specifies a port must be doubled, or the list separator must
17098 be changed. The following two examples have the same effect:
17099 .code
17100 route_list = * "host1.tld::1225 : host2.tld::1226"
17101 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
17102 .endd
17103 .next
17104 When IPv6 addresses are involved, it gets worse, because they contain
17105 colons of their own. To make this case easier, it is permitted to
17106 enclose an IP address (either v4 or v6) in square brackets if a port
17107 number follows. For example:
17108 .code
17109 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
17110 .endd
17111 .endlist
17112
17113 .section "How the list of hosts is used" "SECThostshowused"
17114 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
17115 the hosts is tried, in the order specified, when carrying out the SMTP
17116 delivery. However, the order can be changed by setting the &%hosts_randomize%&
17117 option, either on the router (see section &<<SECTprioptman>>& above), or on the
17118 transport.
17119
17120 Hosts may be listed by name or by IP address. An unadorned name in the list of
17121 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
17122 interpreted as an indirection to a sublist of hosts obtained by looking up MX
17123 records in the DNS. For example:
17124 .code
17125 route_list = * x.y.z:p.q.r/MX:e.f.g
17126 .endd
17127 If this feature is used with a port specifier, the port must come last. For
17128 example:
17129 .code
17130 route_list = * dom1.tld/mx::1225
17131 .endd
17132 If the &%hosts_randomize%& option is set, the order of the items in the list is
17133 randomized before any lookups are done. Exim then scans the list; for any name
17134 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
17135 be an interface on the local host and the item is not the first in the list,
17136 Exim discards it and any subsequent items. If it is the first item, what
17137 happens is controlled by the
17138 .oindex "&%self%&" "in &(manualroute)& router"
17139 &%self%& option of the router.
17140
17141 A name on the list that is followed by &`/MX`& is replaced with the list of
17142 hosts obtained by looking up MX records for the name. This is always a DNS
17143 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
17144 below) are not relevant here. The order of these hosts is determined by the
17145 preference values in the MX records, according to the usual rules. Because
17146 randomizing happens before the MX lookup, it does not affect the order that is
17147 defined by MX preferences.
17148
17149 If the local host is present in the sublist obtained from MX records, but is
17150 not the most preferred host in that list, it and any equally or less
17151 preferred hosts are removed before the sublist is inserted into the main list.
17152
17153 If the local host is the most preferred host in the MX list, what happens
17154 depends on where in the original list of hosts the &`/MX`& item appears. If it
17155 is not the first item (that is, there are previous hosts in the main list),
17156 Exim discards this name and any subsequent items in the main list.
17157
17158 If the MX item is first in the list of hosts, and the local host is the
17159 most preferred host, what happens is controlled by the &%self%& option of the
17160 router.
17161
17162 DNS failures when lookup up the MX records are treated in the same way as DNS
17163 failures when looking up IP addresses: &%pass_on_timeout%& and
17164 &%host_find_failed%& are used when relevant.
17165
17166 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
17167 whether obtained from an MX lookup or not.
17168
17169
17170
17171 .section "How the options are used" "SECThowoptused"
17172 The options are a sequence of words; in practice no more than three are ever
17173 present. One of the words can be the name of a transport; this overrides the
17174 &%transport%& option on the router for this particular routing rule only. The
17175 other words (if present) control randomization of the list of hosts on a
17176 per-rule basis, and how the IP addresses of the hosts are to be found when
17177 routing to a remote transport. These options are as follows:
17178
17179 .ilist
17180 &%randomize%&: randomize the order of the hosts in this list, overriding the
17181 setting of &%hosts_randomize%& for this routing rule only.
17182 .next
17183 &%no_randomize%&: do not randomize the order of the hosts in this list,
17184 overriding the setting of &%hosts_randomize%& for this routing rule only.
17185 .next
17186 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
17187 find IP addresses. This function may ultimately cause a DNS lookup, but it may
17188 also look in &_/etc/hosts_& or other sources of information.
17189 .next
17190 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
17191 no address records are found. If there is a temporary DNS error (such as a
17192 timeout), delivery is deferred.
17193 .endlist
17194
17195 For example:
17196 .code
17197 route_list = domain1 host1:host2:host3 randomize bydns;\
17198 domain2 host4:host5
17199 .endd
17200 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
17201 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
17202 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
17203 or &[gethostbyname()]&, and the result of the lookup is the result of that
17204 call.
17205
17206 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
17207 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
17208 instead of TRY_AGAIN. That is why the default action is to try a DNS
17209 lookup first. Only if that gives a definite &"no such host"& is the local
17210 function called.
17211
17212
17213
17214 If no IP address for a host can be found, what happens is controlled by the
17215 &%host_find_failed%& option.
17216
17217 .vindex "&$host$&"
17218 When an address is routed to a local transport, IP addresses are not looked up.
17219 The host list is passed to the transport in the &$host$& variable.
17220
17221
17222
17223 .section "Manualroute examples" "SECID123"
17224 In some of the examples that follow, the presence of the &%remote_smtp%&
17225 transport, as defined in the default configuration file, is assumed:
17226
17227 .ilist
17228 .cindex "smart host" "example router"
17229 The &(manualroute)& router can be used to forward all external mail to a
17230 &'smart host'&. If you have set up, in the main part of the configuration, a
17231 named domain list that contains your local domains, for example:
17232 .code
17233 domainlist local_domains = my.domain.example
17234 .endd
17235 You can arrange for all other domains to be routed to a smart host by making
17236 your first router something like this:
17237 .code
17238 smart_route:
17239 driver = manualroute
17240 domains = !+local_domains
17241 transport = remote_smtp
17242 route_list = * smarthost.ref.example
17243 .endd
17244 This causes all non-local addresses to be sent to the single host
17245 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
17246 they are tried in order
17247 (but you can use &%hosts_randomize%& to vary the order each time).
17248 Another way of configuring the same thing is this:
17249 .code
17250 smart_route:
17251 driver = manualroute
17252 transport = remote_smtp
17253 route_list = !+local_domains smarthost.ref.example
17254 .endd
17255 There is no difference in behaviour between these two routers as they stand.
17256 However, they behave differently if &%no_more%& is added to them. In the first
17257 example, the router is skipped if the domain does not match the &%domains%&
17258 precondition; the following router is always tried. If the router runs, it
17259 always matches the domain and so can never decline. Therefore, &%no_more%&
17260 would have no effect. In the second case, the router is never skipped; it
17261 always runs. However, if it doesn't match the domain, it declines. In this case
17262 &%no_more%& would prevent subsequent routers from running.
17263
17264 .next
17265 .cindex "mail hub example"
17266 A &'mail hub'& is a host which receives mail for a number of domains via MX
17267 records in the DNS and delivers it via its own private routing mechanism. Often
17268 the final destinations are behind a firewall, with the mail hub being the one
17269 machine that can connect to machines both inside and outside the firewall. The
17270 &(manualroute)& router is usually used on a mail hub to route incoming messages
17271 to the correct hosts. For a small number of domains, the routing can be inline,
17272 using the &%route_list%& option, but for a larger number a file or database
17273 lookup is easier to manage.
17274
17275 If the domain names are in fact the names of the machines to which the mail is
17276 to be sent by the mail hub, the configuration can be quite simple. For
17277 example:
17278 .code
17279 hub_route:
17280 driver = manualroute
17281 transport = remote_smtp
17282 route_list = *.rhodes.tvs.example $domain
17283 .endd
17284 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
17285 whose names are the same as the mail domains. A similar approach can be taken
17286 if the host name can be obtained from the domain name by a string manipulation
17287 that the expansion facilities can handle. Otherwise, a lookup based on the
17288 domain can be used to find the host:
17289 .code
17290 through_firewall:
17291 driver = manualroute
17292 transport = remote_smtp
17293 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
17294 .endd
17295 The result of the lookup must be the name or IP address of the host (or
17296 hosts) to which the address is to be routed. If the lookup fails, the route
17297 data is empty, causing the router to decline. The address then passes to the
17298 next router.
17299
17300 .next
17301 .cindex "batched SMTP output example"
17302 .cindex "SMTP" "batched outgoing; example"
17303 You can use &(manualroute)& to deliver messages to pipes or files in batched
17304 SMTP format for onward transportation by some other means. This is one way of
17305 storing mail for a dial-up host when it is not connected. The route list entry
17306 can be as simple as a single domain name in a configuration like this:
17307 .code
17308 save_in_file:
17309 driver = manualroute
17310 transport = batchsmtp_appendfile
17311 route_list = saved.domain.example
17312 .endd
17313 though often a pattern is used to pick up more than one domain. If there are
17314 several domains or groups of domains with different transport requirements,
17315 different transports can be listed in the routing information:
17316 .code
17317 save_in_file:
17318 driver = manualroute
17319 route_list = \
17320 *.saved.domain1.example $domain batch_appendfile; \
17321 *.saved.domain2.example \
17322 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
17323 batch_pipe
17324 .endd
17325 .vindex "&$domain$&"
17326 .vindex "&$host$&"
17327 The first of these just passes the domain in the &$host$& variable, which
17328 doesn't achieve much (since it is also in &$domain$&), but the second does a
17329 file lookup to find a value to pass, causing the router to decline to handle
17330 the address if the lookup fails.
17331
17332 .next
17333 .cindex "UUCP" "example of router for"
17334 Routing mail directly to UUCP software is a specific case of the use of
17335 &(manualroute)& in a gateway to another mail environment. This is an example of
17336 one way it can be done:
17337 .code
17338 # Transport
17339 uucp:
17340 driver = pipe
17341 user = nobody
17342 command = /usr/local/bin/uux -r - \
17343 ${substr_-5:$host}!rmail ${local_part}
17344 return_fail_output = true
17345
17346 # Router
17347 uucphost:
17348 transport = uucp
17349 driver = manualroute
17350 route_data = \
17351 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
17352 .endd
17353 The file &_/usr/local/exim/uucphosts_& contains entries like
17354 .code
17355 darksite.ethereal.example: darksite.UUCP
17356 .endd
17357 It can be set up more simply without adding and removing &".UUCP"& but this way
17358 makes clear the distinction between the domain name
17359 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
17360 .endlist
17361 .ecindex IIDmanrou1
17362 .ecindex IIDmanrou2
17363
17364
17365
17366
17367
17368
17369
17370
17371 . ////////////////////////////////////////////////////////////////////////////
17372 . ////////////////////////////////////////////////////////////////////////////
17373
17374 .chapter "The queryprogram router" "CHAPdriverlast"
17375 .scindex IIDquerou1 "&(queryprogram)& router"
17376 .scindex IIDquerou2 "routers" "&(queryprogram)&"
17377 .cindex "routing" "by external program"
17378 The &(queryprogram)& router routes an address by running an external command
17379 and acting on its output. This is an expensive way to route, and is intended
17380 mainly for use in lightly-loaded systems, or for performing experiments.
17381 However, if it is possible to use the precondition options (&%domains%&,
17382 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
17383 be used in special cases, even on a busy host. There are the following private
17384 options:
17385 .cindex "options" "&(queryprogram)& router"
17386
17387 .option command queryprogram string&!! unset
17388 This option must be set. It specifies the command that is to be run. The
17389 command is split up into a command name and arguments, and then each is
17390 expanded separately (exactly as for a &(pipe)& transport, described in chapter
17391 &<<CHAPpipetransport>>&).
17392
17393
17394 .option command_group queryprogram string unset
17395 .cindex "gid (group id)" "in &(queryprogram)& router"
17396 This option specifies a gid to be set when running the command while routing an
17397 address for deliver. It must be set if &%command_user%& specifies a numerical
17398 uid. If it begins with a digit, it is interpreted as the numerical value of the
17399 gid. Otherwise it is looked up using &[getgrnam()]&.
17400
17401
17402 .option command_user queryprogram string unset
17403 .cindex "uid (user id)" "for &(queryprogram)&"
17404 This option must be set. It specifies the uid which is set when running the
17405 command while routing an address for delivery. If the value begins with a digit,
17406 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
17407 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
17408 not set, a value for the gid also.
17409
17410 &*Warning:*& Changing uid and gid is possible only when Exim is running as
17411 root, which it does during a normal delivery in a conventional configuration.
17412 However, when an address is being verified during message reception, Exim is
17413 usually running as the Exim user, not as root. If the &(queryprogram)& router
17414 is called from a non-root process, Exim cannot change uid or gid before running
17415 the command. In this circumstance the command runs under the current uid and
17416 gid.
17417
17418
17419 .option current_directory queryprogram string /
17420 This option specifies an absolute path which is made the current directory
17421 before running the command.
17422
17423
17424 .option timeout queryprogram time 1h
17425 If the command does not complete within the timeout period, its process group
17426 is killed and the message is frozen. A value of zero time specifies no
17427 timeout.
17428
17429
17430 The standard output of the command is connected to a pipe, which is read when
17431 the command terminates. It should consist of a single line of output,
17432 containing up to five fields, separated by white space. The maximum length of
17433 the line is 1023 characters. Longer lines are silently truncated. The first
17434 field is one of the following words (case-insensitive):
17435
17436 .ilist
17437 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
17438 below).
17439 .next
17440 &'Decline'&: the router declines; pass the address to the next router, unless
17441 &%no_more%& is set.
17442 .next
17443 &'Fail'&: routing failed; do not pass the address to any more routers. Any
17444 subsequent text on the line is an error message. If the router is run as part
17445 of address verification during an incoming SMTP message, the message is
17446 included in the SMTP response.
17447 .next
17448 &'Defer'&: routing could not be completed at this time; try again later. Any
17449 subsequent text on the line is an error message which is logged. It is not
17450 included in any SMTP response.
17451 .next
17452 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
17453 .next
17454 &'Pass'&: pass the address to the next router (or the router specified by
17455 &%pass_router%&), overriding &%no_more%&.
17456 .next
17457 &'Redirect'&: the message is redirected. The remainder of the line is a list of
17458 new addresses, which are routed independently, starting with the first router,
17459 or the router specified by &%redirect_router%&, if set.
17460 .endlist
17461
17462 When the first word is &'accept'&, the remainder of the line consists of a
17463 number of keyed data values, as follows (split into two lines here, to fit on
17464 the page):
17465 .code
17466 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
17467 LOOKUP=byname|bydns DATA=<text>
17468 .endd
17469 The data items can be given in any order, and all are optional. If no transport
17470 is included, the transport specified by the generic &%transport%& option is
17471 used. The list of hosts and the lookup type are needed only if the transport is
17472 an &(smtp)& transport that does not itself supply a list of hosts.
17473
17474 The format of the list of hosts is the same as for the &(manualroute)& router.
17475 As well as host names and IP addresses with optional port numbers, as described
17476 in section &<<SECTformatonehostitem>>&, it may contain names followed by
17477 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
17478 (see section &<<SECThostshowused>>&).
17479
17480 If the lookup type is not specified, Exim behaves as follows when trying to
17481 find an IP address for each host: First, a DNS lookup is done. If this yields
17482 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
17483 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
17484 result of the lookup is the result of that call.
17485
17486 .vindex "&$address_data$&"
17487 If the DATA field is set, its value is placed in the &$address_data$&
17488 variable. For example, this return line
17489 .code
17490 accept hosts=x1.y.example:x2.y.example data="rule1"
17491 .endd
17492 routes the address to the default transport, passing a list of two hosts. When
17493 the transport runs, the string &"rule1"& is in &$address_data$&.
17494 .ecindex IIDquerou1
17495 .ecindex IIDquerou2
17496
17497
17498
17499
17500 . ////////////////////////////////////////////////////////////////////////////
17501 . ////////////////////////////////////////////////////////////////////////////
17502
17503 .chapter "The redirect router" "CHAPredirect"
17504 .scindex IIDredrou1 "&(redirect)& router"
17505 .scindex IIDredrou2 "routers" "&(redirect)&"
17506 .cindex "alias file" "in a &(redirect)& router"
17507 .cindex "address redirection" "&(redirect)& router"
17508 The &(redirect)& router handles several kinds of address redirection. Its most
17509 common uses are for resolving local part aliases from a central alias file
17510 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
17511 files, but it has many other potential uses. The incoming address can be
17512 redirected in several different ways:
17513
17514 .ilist
17515 It can be replaced by one or more new addresses which are themselves routed
17516 independently.
17517 .next
17518 It can be routed to be delivered to a given file or directory.
17519 .next
17520 It can be routed to be delivered to a specified pipe command.
17521 .next
17522 It can cause an automatic reply to be generated.
17523 .next
17524 It can be forced to fail, optionally with a custom error message.
17525 .next
17526 It can be temporarily deferred, optionally with a custom message.
17527 .next
17528 It can be discarded.
17529 .endlist
17530
17531 The generic &%transport%& option must not be set for &(redirect)& routers.
17532 However, there are some private options which define transports for delivery to
17533 files and pipes, and for generating autoreplies. See the &%file_transport%&,
17534 &%pipe_transport%& and &%reply_transport%& descriptions below.
17535
17536
17537
17538 .section "Redirection data" "SECID124"
17539 The router operates by interpreting a text string which it obtains either by
17540 expanding the contents of the &%data%& option, or by reading the entire
17541 contents of a file whose name is given in the &%file%& option. These two
17542 options are mutually exclusive. The first is commonly used for handling system
17543 aliases, in a configuration like this:
17544 .code
17545 system_aliases:
17546 driver = redirect
17547 data = ${lookup{$local_part}lsearch{/etc/aliases}}
17548 .endd
17549 If the lookup fails, the expanded string in this example is empty. When the
17550 expansion of &%data%& results in an empty string, the router declines. A forced
17551 expansion failure also causes the router to decline; other expansion failures
17552 cause delivery to be deferred.
17553
17554 A configuration using &%file%& is commonly used for handling users'
17555 &_.forward_& files, like this:
17556 .code
17557 userforward:
17558 driver = redirect
17559 check_local_user
17560 file = $home/.forward
17561 no_verify
17562 .endd
17563 If the file does not exist, or causes no action to be taken (for example, it is
17564 empty or consists only of comments), the router declines. &*Warning*&: This
17565 is not the case when the file contains syntactically valid items that happen to
17566 yield empty addresses, for example, items containing only RFC 2822 address
17567 comments.
17568
17569
17570
17571 .section "Forward files and address verification" "SECID125"
17572 .cindex "address redirection" "while verifying"
17573 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
17574 &_.forward_& files, as in the example above. There are two reasons for this:
17575
17576 .ilist
17577 When Exim is receiving an incoming SMTP message from a remote host, it is
17578 running under the Exim uid, not as root. Exim is unable to change uid to read
17579 the file as the user, and it may not be able to read it as the Exim user. So in
17580 practice the router may not be able to operate.
17581 .next
17582 However, even when the router can operate, the existence of a &_.forward_& file
17583 is unimportant when verifying an address. What should be checked is whether the
17584 local part is a valid user name or not. Cutting out the redirection processing
17585 saves some resources.
17586 .endlist
17587
17588
17589
17590
17591
17592
17593 .section "Interpreting redirection data" "SECID126"
17594 .cindex "Sieve filter" "specifying in redirection data"
17595 .cindex "filter" "specifying in redirection data"
17596 The contents of the data string, whether obtained from &%data%& or &%file%&,
17597 can be interpreted in two different ways:
17598
17599 .ilist
17600 If the &%allow_filter%& option is set true, and the data begins with the text
17601 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
17602 &'filtering'& instructions in the form of an Exim or Sieve filter file,
17603 respectively. Details of the syntax and semantics of filter files are described
17604 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
17605 document is intended for use by end users.
17606 .next
17607 Otherwise, the data must be a comma-separated list of redirection items, as
17608 described in the next section.
17609 .endlist
17610
17611 When a message is redirected to a file (a &"mail folder"&), the file name given
17612 in a non-filter redirection list must always be an absolute path. A filter may
17613 generate a relative path &-- how this is handled depends on the transport's
17614 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
17615 for the &(appendfile)& transport.
17616
17617
17618
17619 .section "Items in a non-filter redirection list" "SECTitenonfilred"
17620 .cindex "address redirection" "non-filter list items"
17621 When the redirection data is not an Exim or Sieve filter, for example, if it
17622 comes from a conventional alias or forward file, it consists of a list of
17623 addresses, file names, pipe commands, or certain special items (see section
17624 &<<SECTspecitredli>>& below). The special items can be individually enabled or
17625 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
17626 depending on their default values. The items in the list are separated by
17627 commas or newlines.
17628 If a comma is required in an item, the entire item must be enclosed in double
17629 quotes.
17630
17631 Lines starting with a # character are comments, and are ignored, and # may
17632 also appear following a comma, in which case everything between the # and the
17633 next newline character is ignored.
17634
17635 If an item is entirely enclosed in double quotes, these are removed. Otherwise
17636 double quotes are retained because some forms of mail address require their use
17637 (but never to enclose the entire address). In the following description,
17638 &"item"& refers to what remains after any surrounding double quotes have been
17639 removed.
17640
17641 .vindex "&$local_part$&"
17642 &*Warning*&: If you use an Exim expansion to construct a redirection address,
17643 and the expansion contains a reference to &$local_part$&, you should make use
17644 of the &%quote_local_part%& expansion operator, in case the local part contains
17645 special characters. For example, to redirect all mail for the domain
17646 &'obsolete.example'&, retaining the existing local part, you could use this
17647 setting:
17648 .code
17649 data = ${quote_local_part:$local_part}@newdomain.example
17650 .endd
17651
17652
17653 .section "Redirecting to a local mailbox" "SECTredlocmai"
17654 .cindex "routing" "loops in"
17655 .cindex "loop" "while routing, avoidance of"
17656 .cindex "address redirection" "to local mailbox"
17657 A redirection item may safely be the same as the address currently under
17658 consideration. This does not cause a routing loop, because a router is
17659 automatically skipped if any ancestor of the address that is being processed
17660 is the same as the current address and was processed by the current router.
17661 Such an address is therefore passed to the following routers, so it is handled
17662 as if there were no redirection. When making this loop-avoidance test, the
17663 complete local part, including any prefix or suffix, is used.
17664
17665 .cindex "address redirection" "local part without domain"
17666 Specifying the same local part without a domain is a common usage in personal
17667 filter files when the user wants to have messages delivered to the local
17668 mailbox and also forwarded elsewhere. For example, the user whose login is
17669 &'cleo'& might have a &_.forward_& file containing this:
17670 .code
17671 cleo, cleopatra@egypt.example
17672 .endd
17673 .cindex "backslash in alias file"
17674 .cindex "alias file" "backslash in"
17675 For compatibility with other MTAs, such unqualified local parts may be
17676 preceded by &"\"&, but this is not a requirement for loop prevention. However,
17677 it does make a difference if more than one domain is being handled
17678 synonymously.
17679
17680 If an item begins with &"\"& and the rest of the item parses as a valid RFC
17681 2822 address that does not include a domain, the item is qualified using the
17682 domain of the incoming address. In the absence of a leading &"\"&, unqualified
17683 addresses are qualified using the value in &%qualify_recipient%&, but you can
17684 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
17685
17686 Care must be taken if there are alias names for local users.
17687 Consider an MTA handling a single local domain where the system alias file
17688 contains:
17689 .code
17690 Sam.Reman: spqr
17691 .endd
17692 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
17693 messages in the local mailbox, and also forward copies elsewhere. He creates
17694 this forward file:
17695 .code
17696 Sam.Reman, spqr@reme.elsewhere.example
17697 .endd
17698 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
17699 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
17700 second time round, because it has previously routed it,
17701 and the following routers presumably cannot handle the alias. The forward file
17702 should really contain
17703 .code
17704 spqr, spqr@reme.elsewhere.example
17705 .endd
17706 but because this is such a common error, the &%check_ancestor%& option (see
17707 below) exists to provide a way to get round it. This is normally set on a
17708 &(redirect)& router that is handling users' &_.forward_& files.
17709
17710
17711
17712 .section "Special items in redirection lists" "SECTspecitredli"
17713 In addition to addresses, the following types of item may appear in redirection
17714 lists (that is, in non-filter redirection data):
17715
17716 .ilist
17717 .cindex "pipe" "in redirection list"
17718 .cindex "address redirection" "to pipe"
17719 An item is treated as a pipe command if it begins with &"|"& and does not parse
17720 as a valid RFC 2822 address that includes a domain. A transport for running the
17721 command must be specified by the &%pipe_transport%& option.
17722 Normally, either the router or the transport specifies a user and a group under
17723 which to run the delivery. The default is to use the Exim user and group.
17724
17725 Single or double quotes can be used for enclosing the individual arguments of
17726 the pipe command; no interpretation of escapes is done for single quotes. If
17727 the command contains a comma character, it is necessary to put the whole item
17728 in double quotes, for example:
17729 .code
17730 "|/some/command ready,steady,go"
17731 .endd
17732 since items in redirection lists are terminated by commas. Do not, however,
17733 quote just the command. An item such as
17734 .code
17735 |"/some/command ready,steady,go"
17736 .endd
17737 is interpreted as a pipe with a rather strange command name, and no arguments.
17738
17739 .next
17740 .cindex "file" "in redirection list"
17741 .cindex "address redirection" "to file"
17742 An item is interpreted as a path name if it begins with &"/"& and does not
17743 parse as a valid RFC 2822 address that includes a domain. For example,
17744 .code
17745 /home/world/minbari
17746 .endd
17747 is treated as a file name, but
17748 .code
17749 /s=molari/o=babylon/@x400gate.way
17750 .endd
17751 is treated as an address. For a file name, a transport must be specified using
17752 the &%file_transport%& option. However, if the generated path name ends with a
17753 forward slash character, it is interpreted as a directory name rather than a
17754 file name, and &%directory_transport%& is used instead.
17755
17756 Normally, either the router or the transport specifies a user and a group under
17757 which to run the delivery. The default is to use the Exim user and group.
17758
17759 .cindex "&_/dev/null_&"
17760 However, if a redirection item is the path &_/dev/null_&, delivery to it is
17761 bypassed at a high level, and the log entry shows &"**bypassed**"&
17762 instead of a transport name. In this case the user and group are not used.
17763
17764 .next
17765 .cindex "included address list"
17766 .cindex "address redirection" "included external list"
17767 If an item is of the form
17768 .code
17769 :include:<path name>
17770 .endd
17771 a list of further items is taken from the given file and included at that
17772 point. &*Note*&: Such a file can not be a filter file; it is just an
17773 out-of-line addition to the list. The items in the included list are separated
17774 by commas or newlines and are not subject to expansion. If this is the first
17775 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
17776 the alias name. This example is incorrect:
17777 .code
17778 list1 :include:/opt/lists/list1
17779 .endd
17780 It must be given as
17781 .code
17782 list1: :include:/opt/lists/list1
17783 .endd
17784 .next
17785 .cindex "address redirection" "to black hole"
17786 Sometimes you want to throw away mail to a particular local part. Making the
17787 &%data%& option expand to an empty string does not work, because that causes
17788 the router to decline. Instead, the alias item
17789 .cindex "black hole"
17790 .cindex "abandoning mail"
17791 &':blackhole:'& can be used. It does what its name implies. No delivery is
17792 done, and no error message is generated. This has the same effect as specifing
17793 &_/dev/null_& as a destination, but it can be independently disabled.
17794
17795 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
17796 delivery is done for the original local part, even if other redirection items
17797 are present. If you are generating a multi-item list (for example, by reading a
17798 database) and need the ability to provide a no-op item, you must use
17799 &_/dev/null_&.
17800
17801 .next
17802 .cindex "delivery" "forcing failure"
17803 .cindex "delivery" "forcing deferral"
17804 .cindex "failing delivery" "forcing"
17805 .cindex "deferred delivery, forcing"
17806 .cindex "customizing" "failure message"
17807 An attempt to deliver a particular address can be deferred or forced to fail by
17808 redirection items of the form
17809 .code
17810 :defer:
17811 :fail:
17812 .endd
17813 respectively. When a redirection list contains such an item, it applies to the
17814 entire redirection; any other items in the list are ignored (&':blackhole:'& is
17815 different). Any text following &':fail:'& or &':defer:'& is placed in the error
17816 text associated with the failure. For example, an alias file might contain:
17817 .code
17818 X.Employee: :fail: Gone away, no forwarding address
17819 .endd
17820 In the case of an address that is being verified from an ACL or as the subject
17821 of a
17822 .cindex "VRFY" "error text, display of"
17823 VRFY command, the text is included in the SMTP error response by
17824 default.
17825 .cindex "EXPN" "error text, display of"
17826 The text is not included in the response to an EXPN command. In non-SMTP cases
17827 the text is included in the error message that Exim generates.
17828
17829 .cindex "SMTP" "error codes"
17830 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
17831 &':fail:'&. However, if the message starts with three digits followed by a
17832 space, optionally followed by an extended code of the form &'n.n.n'&, also
17833 followed by a space, and the very first digit is the same as the default error
17834 code, the code from the message is used instead. If the very first digit is
17835 incorrect, a panic error is logged, and the default code is used. You can
17836 suppress the use of the supplied code in a redirect router by setting the
17837 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
17838 ignored.
17839
17840 .vindex "&$acl_verify_message$&"
17841 In an ACL, an explicitly provided message overrides the default, but the
17842 default message is available in the variable &$acl_verify_message$& and can
17843 therefore be included in a custom message if this is desired.
17844
17845 Normally the error text is the rest of the redirection list &-- a comma does
17846 not terminate it &-- but a newline does act as a terminator. Newlines are not
17847 normally present in alias expansions. In &(lsearch)& lookups they are removed
17848 as part of the continuation process, but they may exist in other kinds of
17849 lookup and in &':include:'& files.
17850
17851 During routing for message delivery (as opposed to verification), a redirection
17852 containing &':fail:'& causes an immediate failure of the incoming address,
17853 whereas &':defer:'& causes the message to remain on the queue so that a
17854 subsequent delivery attempt can happen at a later time. If an address is
17855 deferred for too long, it will ultimately fail, because the normal retry
17856 rules still apply.
17857
17858 .next
17859 .cindex "alias file" "exception to default"
17860 Sometimes it is useful to use a single-key search type with a default (see
17861 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
17862 for exceptions to the default. These can be handled by aliasing them to
17863 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
17864 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
17865 results in an empty redirection list has the same effect.
17866 .endlist
17867
17868
17869 .section "Duplicate addresses" "SECTdupaddr"
17870 .cindex "duplicate addresses"
17871 .cindex "address duplicate, discarding"
17872 .cindex "pipe" "duplicated"
17873 Exim removes duplicate addresses from the list to which it is delivering, so as
17874 to deliver just one copy to each address. This does not apply to deliveries
17875 routed to pipes by different immediate parent addresses, but an indirect
17876 aliasing scheme of the type
17877 .code
17878 pipe: |/some/command $local_part
17879 localpart1: pipe
17880 localpart2: pipe
17881 .endd
17882 does not work with a message that is addressed to both local parts, because
17883 when the second is aliased to the intermediate local part &"pipe"& it gets
17884 discarded as being the same as a previously handled address. However, a scheme
17885 such as
17886 .code
17887 localpart1: |/some/command $local_part
17888 localpart2: |/some/command $local_part
17889 .endd
17890 does result in two different pipe deliveries, because the immediate parents of
17891 the pipes are distinct.
17892
17893
17894
17895 .section "Repeated redirection expansion" "SECID128"
17896 .cindex "repeated redirection expansion"
17897 .cindex "address redirection" "repeated for each delivery attempt"
17898 When a message cannot be delivered to all of its recipients immediately,
17899 leading to two or more delivery attempts, redirection expansion is carried out
17900 afresh each time for those addresses whose children were not all previously
17901 delivered. If redirection is being used as a mailing list, this can lead to new
17902 members of the list receiving copies of old messages. The &%one_time%& option
17903 can be used to avoid this.
17904
17905
17906 .section "Errors in redirection lists" "SECID129"
17907 .cindex "address redirection" "errors"
17908 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
17909 error is skipped, and an entry is written to the main log. This may be useful
17910 for mailing lists that are automatically managed. Otherwise, if an error is
17911 detected while generating the list of new addresses, the original address is
17912 deferred. See also &%syntax_errors_to%&.
17913
17914
17915
17916 .section "Private options for the redirect router" "SECID130"
17917
17918 .cindex "options" "&(redirect)& router"
17919 The private options for the &(redirect)& router are as follows:
17920
17921
17922 .option allow_defer redirect boolean false
17923 Setting this option allows the use of &':defer:'& in non-filter redirection
17924 data, or the &%defer%& command in an Exim filter file.
17925
17926
17927 .option allow_fail redirect boolean false
17928 .cindex "failing delivery" "from filter"
17929 If this option is true, the &':fail:'& item can be used in a redirection list,
17930 and the &%fail%& command may be used in an Exim filter file.
17931
17932
17933 .option allow_filter redirect boolean false
17934 .cindex "filter" "enabling use of"
17935 .cindex "Sieve filter" "enabling use of"
17936 Setting this option allows Exim to interpret redirection data that starts with
17937 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
17938 are some features of Exim filter files that some administrators may wish to
17939 lock out; see the &%forbid_filter_%&&'xxx'& options below.
17940
17941 It is also possible to lock out Exim filters or Sieve filters while allowing
17942 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
17943
17944
17945 The filter is run using the uid and gid set by the generic &%user%& and
17946 &%group%& options. These take their defaults from the password data if
17947 &%check_local_user%& is set, so in the normal case of users' personal filter
17948 files, the filter is run as the relevant user. When &%allow_filter%& is set
17949 true, Exim insists that either &%check_local_user%& or &%user%& is set.
17950
17951
17952
17953 .option allow_freeze redirect boolean false
17954 .cindex "freezing messages" "allowing in filter"
17955 Setting this option allows the use of the &%freeze%& command in an Exim filter.
17956 This command is more normally encountered in system filters, and is disabled by
17957 default for redirection filters because it isn't something you usually want to
17958 let ordinary users do.
17959
17960
17961
17962 .option check_ancestor redirect boolean false
17963 This option is concerned with handling generated addresses that are the same
17964 as some address in the list of redirection ancestors of the current address.
17965 Although it is turned off by default in the code, it is set in the default
17966 configuration file for handling users' &_.forward_& files. It is recommended
17967 for this use of the &(redirect)& router.
17968
17969 When &%check_ancestor%& is set, if a generated address (including the domain)
17970 is the same as any ancestor of the current address, it is replaced by a copy of
17971 the current address. This helps in the case where local part A is aliased to B,
17972 and B has a &_.forward_& file pointing back to A. For example, within a single
17973 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
17974 &_&~jb/.forward_& contains:
17975 .code
17976 \Joe.Bloggs, <other item(s)>
17977 .endd
17978 Without the &%check_ancestor%& setting, either local part (&"jb"& or
17979 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
17980 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
17981 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
17982 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
17983 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
17984 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
17985 original address. See also the &%repeat_use%& option below.
17986
17987
17988 .option check_group redirect boolean "see below"
17989 When the &%file%& option is used, the group owner of the file is checked only
17990 when this option is set. The permitted groups are those listed in the
17991 &%owngroups%& option, together with the user's default group if
17992 &%check_local_user%& is set. If the file has the wrong group, routing is
17993 deferred. The default setting for this option is true if &%check_local_user%&
17994 is set and the &%modemask%& option permits the group write bit, or if the
17995 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
17996
17997
17998
17999 .option check_owner redirect boolean "see below"
18000 When the &%file%& option is used, the owner of the file is checked only when
18001 this option is set. If &%check_local_user%& is set, the local user is
18002 permitted; otherwise the owner must be one of those listed in the &%owners%&
18003 option. The default value for this option is true if &%check_local_user%& or
18004 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
18005
18006
18007 .option data redirect string&!! unset
18008 This option is mutually exclusive with &%file%&. One or other of them must be
18009 set, but not both. The contents of &%data%& are expanded, and then used as the
18010 list of forwarding items, or as a set of filtering instructions. If the
18011 expansion is forced to fail, or the result is an empty string or a string that
18012 has no effect (consists entirely of comments), the router declines.
18013
18014 When filtering instructions are used, the string must begin with &"#Exim
18015 filter"&, and all comments in the string, including this initial one, must be
18016 terminated with newline characters. For example:
18017 .code
18018 data = #Exim filter\n\
18019 if $h_to: contains Exim then save $home/mail/exim endif
18020 .endd
18021 If you are reading the data from a database where newlines cannot be included,
18022 you can use the &${sg}$& expansion item to turn the escape string of your
18023 choice into a newline.
18024
18025
18026 .option directory_transport redirect string&!! unset
18027 A &(redirect)& router sets up a direct delivery to a directory when a path name
18028 ending with a slash is specified as a new &"address"&. The transport used is
18029 specified by this option, which, after expansion, must be the name of a
18030 configured transport. This should normally be an &(appendfile)& transport.
18031
18032
18033 .option file redirect string&!! unset
18034 This option specifies the name of a file that contains the redirection data. It
18035 is mutually exclusive with the &%data%& option. The string is expanded before
18036 use; if the expansion is forced to fail, the router declines. Other expansion
18037 failures cause delivery to be deferred. The result of a successful expansion
18038 must be an absolute path. The entire file is read and used as the redirection
18039 data. If the data is an empty string or a string that has no effect (consists
18040 entirely of comments), the router declines.
18041
18042 .cindex "NFS" "checking for file existence"
18043 If the attempt to open the file fails with a &"does not exist"& error, Exim
18044 runs a check on the containing directory,
18045 unless &%ignore_enotdir%& is true (see below).
18046 If the directory does not appear to exist, delivery is deferred. This can
18047 happen when users' &_.forward_& files are in NFS-mounted directories, and there
18048 is a mount problem. If the containing directory does exist, but the file does
18049 not, the router declines.
18050
18051
18052 .option file_transport redirect string&!! unset
18053 .vindex "&$address_file$&"
18054 A &(redirect)& router sets up a direct delivery to a file when a path name not
18055 ending in a slash is specified as a new &"address"&. The transport used is
18056 specified by this option, which, after expansion, must be the name of a
18057 configured transport. This should normally be an &(appendfile)& transport. When
18058 it is running, the file name is in &$address_file$&.
18059
18060
18061 .option filter_prepend_home redirect boolean true
18062 When this option is true, if a &(save)& command in an Exim filter specifies a
18063 relative path, and &$home$& is defined, it is automatically prepended to the
18064 relative path. If this option is set false, this action does not happen. The
18065 relative path is then passed to the transport unmodified.
18066
18067
18068 .option forbid_blackhole redirect boolean false
18069 If this option is true, the &':blackhole:'& item may not appear in a
18070 redirection list.
18071
18072
18073 .option forbid_exim_filter redirect boolean false
18074 If this option is set true, only Sieve filters are permitted when
18075 &%allow_filter%& is true.
18076
18077
18078
18079
18080 .option forbid_file redirect boolean false
18081 .cindex "delivery" "to file; forbidding"
18082 .cindex "Sieve filter" "forbidding delivery to a file"
18083 .cindex "Sieve filter" "&""keep""& facility; disabling"
18084 If this option is true, this router may not generate a new address that
18085 specifies delivery to a local file or directory, either from a filter or from a
18086 conventional forward file. This option is forced to be true if &%one_time%& is
18087 set. It applies to Sieve filters as well as to Exim filters, but if true, it
18088 locks out the Sieve's &"keep"& facility.
18089
18090
18091 .option forbid_filter_dlfunc redirect boolean false
18092 .cindex "filter" "locking out certain features"
18093 If this option is true, string expansions in Exim filters are not allowed to
18094 make use of the &%dlfunc%& expansion facility to run dynamically loaded
18095 functions.
18096
18097 .option forbid_filter_existstest redirect boolean false
18098 .cindex "expansion" "statting a file"
18099 If this option is true, string expansions in Exim filters are not allowed to
18100 make use of the &%exists%& condition or the &%stat%& expansion item.
18101
18102 .option forbid_filter_logwrite redirect boolean false
18103 If this option is true, use of the logging facility in Exim filters is not
18104 permitted. Logging is in any case available only if the filter is being run
18105 under some unprivileged uid (which is normally the case for ordinary users'
18106 &_.forward_& files).
18107
18108
18109 .option forbid_filter_lookup redirect boolean false
18110 If this option is true, string expansions in Exim filter files are not allowed
18111 to make use of &%lookup%& items.
18112
18113
18114 .option forbid_filter_perl redirect boolean false
18115 This option has an effect only if Exim is built with embedded Perl support. If
18116 it is true, string expansions in Exim filter files are not allowed to make use
18117 of the embedded Perl support.
18118
18119
18120 .option forbid_filter_readfile redirect boolean false
18121 If this option is true, string expansions in Exim filter files are not allowed
18122 to make use of &%readfile%& items.
18123
18124
18125 .option forbid_filter_readsocket redirect boolean false
18126 If this option is true, string expansions in Exim filter files are not allowed
18127 to make use of &%readsocket%& items.
18128
18129
18130 .option forbid_filter_reply redirect boolean false
18131 If this option is true, this router may not generate an automatic reply
18132 message. Automatic replies can be generated only from Exim or Sieve filter
18133 files, not from traditional forward files. This option is forced to be true if
18134 &%one_time%& is set.
18135
18136
18137 .option forbid_filter_run redirect boolean false
18138 If this option is true, string expansions in Exim filter files are not allowed
18139 to make use of &%run%& items.
18140
18141
18142 .option forbid_include redirect boolean false
18143 If this option is true, items of the form
18144 .code
18145 :include:<path name>
18146 .endd
18147 are not permitted in non-filter redirection lists.
18148
18149
18150 .option forbid_pipe redirect boolean false
18151 .cindex "delivery" "to pipe; forbidding"
18152 If this option is true, this router may not generate a new address which
18153 specifies delivery to a pipe, either from an Exim filter or from a conventional
18154 forward file. This option is forced to be true if &%one_time%& is set.
18155
18156
18157 .option forbid_sieve_filter redirect boolean false
18158 If this option is set true, only Exim filters are permitted when
18159 &%allow_filter%& is true.
18160
18161
18162 .cindex "SMTP" "error codes"
18163 .option forbid_smtp_code redirect boolean false
18164 If this option is set true, any SMTP error codes that are present at the start
18165 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
18166 the default codes (451 and 550, respectively) are always used.
18167
18168
18169
18170
18171 .option hide_child_in_errmsg redirect boolean false
18172 .cindex "bounce message" "redirection details; suppressing"
18173 If this option is true, it prevents Exim from quoting a child address if it
18174 generates a bounce or delay message for it. Instead it says &"an address
18175 generated from <&'the top level address'&>"&. Of course, this applies only to
18176 bounces generated locally. If a message is forwarded to another host, &'its'&
18177 bounce may well quote the generated address.
18178
18179
18180 .option ignore_eacces redirect boolean false
18181 .cindex "EACCES"
18182 If this option is set and an attempt to open a redirection file yields the
18183 EACCES error (permission denied), the &(redirect)& router behaves as if the
18184 file did not exist.
18185
18186
18187 .option ignore_enotdir redirect boolean false
18188 .cindex "ENOTDIR"
18189 If this option is set and an attempt to open a redirection file yields the
18190 ENOTDIR error (something on the path is not a directory), the &(redirect)&
18191 router behaves as if the file did not exist.
18192
18193 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
18194 router that has the &%file%& option set discovers that the file does not exist
18195 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
18196 against unmounted NFS directories. If the parent can not be statted, delivery
18197 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
18198 is set, because that option tells Exim to ignore &"something on the path is not
18199 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
18200 that some operating systems give ENOENT where others give ENOTDIR.
18201
18202
18203
18204 .option include_directory redirect string unset
18205 If this option is set, the path names of any &':include:'& items in a
18206 redirection list must start with this directory.
18207
18208
18209 .option modemask redirect "octal integer" 022
18210 This specifies mode bits which must not be set for a file specified by the
18211 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
18212
18213
18214 .option one_time redirect boolean false
18215 .cindex "one-time aliasing/forwarding expansion"
18216 .cindex "alias file" "one-time expansion"
18217 .cindex "forward file" "one-time expansion"
18218 .cindex "mailing lists" "one-time expansion"
18219 .cindex "address redirection" "one-time expansion"
18220 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
18221 files each time it tries to deliver a message causes a problem when one or more
18222 of the generated addresses fails be delivered at the first attempt. The problem
18223 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
18224 but of what happens when the redirection list changes during the time that the
18225 message is on Exim's queue. This is particularly true in the case of mailing
18226 lists, where new subscribers might receive copies of messages that were posted
18227 before they subscribed.
18228
18229 If &%one_time%& is set and any addresses generated by the router fail to
18230 deliver at the first attempt, the failing addresses are added to the message as
18231 &"top level"& addresses, and the parent address that generated them is marked
18232 &"delivered"&. Thus, redirection does not happen again at the next delivery
18233 attempt.
18234
18235 &*Warning 1*&: Any header line addition or removal that is specified by this
18236 router would be lost if delivery did not succeed at the first attempt. For this
18237 reason, the &%headers_add%& and &%headers_remove%& generic options are not
18238 permitted when &%one_time%& is set.
18239
18240 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
18241 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
18242 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
18243
18244 &*Warning 3*&: The &%unseen%& generic router option may not be set with
18245 &%one_time%&.
18246
18247 The original top-level address is remembered with each of the generated
18248 addresses, and is output in any log messages. However, any intermediate parent
18249 addresses are not recorded. This makes a difference to the log only if
18250 &%all_parents%& log selector is set. It is expected that &%one_time%& will
18251 typically be used for mailing lists, where there is normally just one level of
18252 expansion.
18253
18254
18255 .option owners redirect "string list" unset
18256 .cindex "ownership" "alias file"
18257 .cindex "ownership" "forward file"
18258 .cindex "alias file" "ownership"
18259 .cindex "forward file" "ownership"
18260 This specifies a list of permitted owners for the file specified by &%file%&.
18261 This list is in addition to the local user when &%check_local_user%& is set.
18262 See &%check_owner%& above.
18263
18264
18265 .option owngroups redirect "string list" unset
18266 This specifies a list of permitted groups for the file specified by &%file%&.
18267 The list is in addition to the local user's primary group when
18268 &%check_local_user%& is set. See &%check_group%& above.
18269
18270
18271 .option pipe_transport redirect string&!! unset
18272 .vindex "&$address_pipe$&"
18273 A &(redirect)& router sets up a direct delivery to a pipe when a string
18274 starting with a vertical bar character is specified as a new &"address"&. The
18275 transport used is specified by this option, which, after expansion, must be the
18276 name of a configured transport. This should normally be a &(pipe)& transport.
18277 When the transport is run, the pipe command is in &$address_pipe$&.
18278
18279
18280 .option qualify_domain redirect string&!! unset
18281 .vindex "&$qualify_recipient$&"
18282 If this option is set, and an unqualified address (one without a domain) is
18283 generated, and that address would normally be qualified by the global setting
18284 in &%qualify_recipient%&, it is instead qualified with the domain specified by
18285 expanding this string. If the expansion fails, the router declines. If you want
18286 to revert to the default, you can have the expansion generate
18287 &$qualify_recipient$&.
18288
18289 This option applies to all unqualified addresses generated by Exim filters,
18290 but for traditional &_.forward_& files, it applies only to addresses that are
18291 not preceded by a backslash. Sieve filters cannot generate unqualified
18292 addresses.
18293
18294 .option qualify_preserve_domain redirect boolean false
18295 .cindex "domain" "in redirection; preserving"
18296 .cindex "preserving domain in redirection"
18297 .cindex "address redirection" "domain; preserving"
18298 If this option is set, the router's local &%qualify_domain%& option must not be
18299 set (a configuration error occurs if it is). If an unqualified address (one
18300 without a domain) is generated, it is qualified with the domain of the parent
18301 address (the immediately preceding ancestor) instead of the global
18302 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
18303 this applies whether or not the address is preceded by a backslash.
18304
18305
18306 .option repeat_use redirect boolean true
18307 If this option is set false, the router is skipped for a child address that has
18308 any ancestor that was routed by this router. This test happens before any of
18309 the other preconditions are tested. Exim's default anti-looping rules skip
18310 only when the ancestor is the same as the current address. See also
18311 &%check_ancestor%& above and the generic &%redirect_router%& option.
18312
18313
18314 .option reply_transport redirect string&!! unset
18315 A &(redirect)& router sets up an automatic reply when a &%mail%& or
18316 &%vacation%& command is used in a filter file. The transport used is specified
18317 by this option, which, after expansion, must be the name of a configured
18318 transport. This should normally be an &(autoreply)& transport. Other transports
18319 are unlikely to do anything sensible or useful.
18320
18321
18322 .option rewrite redirect boolean true
18323 .cindex "address redirection" "disabling rewriting"
18324 If this option is set false, addresses generated by the router are not
18325 subject to address rewriting. Otherwise, they are treated like new addresses
18326 and are rewritten according to the global rewriting rules.
18327
18328
18329 .option sieve_subaddress redirect string&!! unset
18330 The value of this option is passed to a Sieve filter to specify the
18331 :subaddress part of an address.
18332
18333 .option sieve_useraddress redirect string&!! unset
18334 The value of this option is passed to a Sieve filter to specify the :user part
18335 of an address. However, if it is unset, the entire original local part
18336 (including any prefix or suffix) is used for :user.
18337
18338
18339 .option sieve_vacation_directory redirect string&!! unset
18340 .cindex "Sieve filter" "vacation directory"
18341 To enable the &"vacation"& extension for Sieve filters, you must set
18342 &%sieve_vacation_directory%& to the directory where vacation databases are held
18343 (do not put anything else in that directory), and ensure that the
18344 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
18345 needs their own directory; Exim will create it if necessary.
18346
18347
18348
18349 .option skip_syntax_errors redirect boolean false
18350 .cindex "forward file" "broken"
18351 .cindex "address redirection" "broken files"
18352 .cindex "alias file" "broken"
18353 .cindex "broken alias or forward files"
18354 .cindex "ignoring faulty addresses"
18355 .cindex "skipping faulty addresses"
18356 .cindex "error" "skipping bad syntax"
18357 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
18358 non-filter redirection data are skipped, and each failing address is logged. If
18359 &%syntax_errors_to%& is set, a message is sent to the address it defines,
18360 giving details of the failures. If &%syntax_errors_text%& is set, its contents
18361 are expanded and placed at the head of the error message generated by
18362 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
18363 be the same address as the generic &%errors_to%& option. The
18364 &%skip_syntax_errors%& option is often used when handling mailing lists.
18365
18366 If all the addresses in a redirection list are skipped because of syntax
18367 errors, the router declines to handle the original address, and it is passed to
18368 the following routers.
18369
18370 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
18371 error in the filter causes filtering to be abandoned without any action being
18372 taken. The incident is logged, and the router declines to handle the address,
18373 so it is passed to the following routers.
18374
18375 .cindex "Sieve filter" "syntax errors in"
18376 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
18377 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
18378 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
18379
18380 &%skip_syntax_errors%& can be used to specify that errors in users' forward
18381 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
18382 option, used with an address that does not get redirected, can be used to
18383 notify users of these errors, by means of a router like this:
18384 .code
18385 userforward:
18386 driver = redirect
18387 allow_filter
18388 check_local_user
18389 file = $home/.forward
18390 file_transport = address_file
18391 pipe_transport = address_pipe
18392 reply_transport = address_reply
18393 no_verify
18394 skip_syntax_errors
18395 syntax_errors_to = real-$local_part@$domain
18396 syntax_errors_text = \
18397 This is an automatically generated message. An error has\n\
18398 been found in your .forward file. Details of the error are\n\
18399 reported below. While this error persists, you will receive\n\
18400 a copy of this message for every message that is addressed\n\
18401 to you. If your .forward file is a filter file, or if it is\n\
18402 a non-filter file containing no valid forwarding addresses,\n\
18403 a copy of each incoming message will be put in your normal\n\
18404 mailbox. If a non-filter file contains at least one valid\n\
18405 forwarding address, forwarding to the valid addresses will\n\
18406 happen, and those will be the only deliveries that occur.
18407 .endd
18408 You also need a router to ensure that local addresses that are prefixed by
18409 &`real-`& are recognized, but not forwarded or filtered. For example, you could
18410 put this immediately before the &(userforward)& router:
18411 .code
18412 real_localuser:
18413 driver = accept
18414 check_local_user
18415 local_part_prefix = real-
18416 transport = local_delivery
18417 .endd
18418 For security, it would probably be a good idea to restrict the use of this
18419 router to locally-generated messages, using a condition such as this:
18420 .code
18421 condition = ${if match {$sender_host_address}\
18422 {\N^(|127\.0\.0\.1)$\N}}
18423 .endd
18424
18425
18426 .option syntax_errors_text redirect string&!! unset
18427 See &%skip_syntax_errors%& above.
18428
18429
18430 .option syntax_errors_to redirect string unset
18431 See &%skip_syntax_errors%& above.
18432 .ecindex IIDredrou1
18433 .ecindex IIDredrou2
18434
18435
18436
18437
18438
18439
18440 . ////////////////////////////////////////////////////////////////////////////
18441 . ////////////////////////////////////////////////////////////////////////////
18442
18443 .chapter "Environment for running local transports" "CHAPenvironment" &&&
18444 "Environment for local transports"
18445 .scindex IIDenvlotra1 "local transports" "environment for"
18446 .scindex IIDenvlotra2 "environment for local transports"
18447 .scindex IIDenvlotra3 "transport" "local; environment for"
18448 Local transports handle deliveries to files and pipes. (The &(autoreply)&
18449 transport can be thought of as similar to a pipe.) Exim always runs transports
18450 in subprocesses, under specified uids and gids. Typical deliveries to local
18451 mailboxes run under the uid and gid of the local user.
18452
18453 Exim also sets a specific current directory while running the transport; for
18454 some transports a home directory setting is also relevant. The &(pipe)&
18455 transport is the only one that sets up environment variables; see section
18456 &<<SECTpipeenv>>& for details.
18457
18458 The values used for the uid, gid, and the directories may come from several
18459 different places. In many cases, the router that handles the address associates
18460 settings with that address as a result of its &%check_local_user%&, &%group%&,
18461 or &%user%& options. However, values may also be given in the transport's own
18462 configuration, and these override anything that comes from the router.
18463
18464
18465
18466 .section "Concurrent deliveries" "SECID131"
18467 .cindex "concurrent deliveries"
18468 .cindex "simultaneous deliveries"
18469 If two different messages for the same local recipient arrive more or less
18470 simultaneously, the two delivery processes are likely to run concurrently. When
18471 the &(appendfile)& transport is used to write to a file, Exim applies locking
18472 rules to stop concurrent processes from writing to the same file at the same
18473 time.
18474
18475 However, when you use a &(pipe)& transport, it is up to you to arrange any
18476 locking that is needed. Here is a silly example:
18477 .code
18478 my_transport:
18479 driver = pipe
18480 command = /bin/sh -c 'cat >>/some/file'
18481 .endd
18482 This is supposed to write the message at the end of the file. However, if two
18483 messages arrive at the same time, the file will be scrambled. You can use the
18484 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
18485 file using the same algorithm that Exim itself uses.
18486
18487
18488
18489
18490 .section "Uids and gids" "SECTenvuidgid"
18491 .cindex "local transports" "uid and gid"
18492 .cindex "transport" "local; uid and gid"
18493 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
18494 overrides any group that the router set in the address, even if &%user%& is not
18495 set for the transport. This makes it possible, for example, to run local mail
18496 delivery under the uid of the recipient (set by the router), but in a special
18497 group (set by the transport). For example:
18498 .code
18499 # Routers ...
18500 # User/group are set by check_local_user in this router
18501 local_users:
18502 driver = accept
18503 check_local_user
18504 transport = group_delivery
18505
18506 # Transports ...
18507 # This transport overrides the group
18508 group_delivery:
18509 driver = appendfile
18510 file = /var/spool/mail/$local_part
18511 group = mail
18512 .endd
18513 If &%user%& is set for a transport, its value overrides what is set in the
18514 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
18515 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
18516 set.
18517
18518 .oindex "&%initgroups%&"
18519 When the uid is taken from the transport's configuration, the &[initgroups()]&
18520 function is called for the groups associated with that uid if the
18521 &%initgroups%& option is set for the transport. When the uid is not specified
18522 by the transport, but is associated with the address by a router, the option
18523 for calling &[initgroups()]& is taken from the router configuration.
18524
18525 .cindex "&(pipe)& transport" "uid for"
18526 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
18527 is set and &%user%& is not set, the uid of the process that called Exim to
18528 receive the message is used, and if &%group%& is not set, the corresponding
18529 original gid is also used.
18530
18531 This is the detailed preference order for obtaining a gid; the first of the
18532 following that is set is used:
18533
18534 .ilist
18535 A &%group%& setting of the transport;
18536 .next
18537 A &%group%& setting of the router;
18538 .next
18539 A gid associated with a user setting of the router, either as a result of
18540 &%check_local_user%& or an explicit non-numeric &%user%& setting;
18541 .next
18542 The group associated with a non-numeric &%user%& setting of the transport;
18543 .next
18544 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
18545 the uid is the creator's uid;
18546 .next
18547 The Exim gid if the Exim uid is being used as a default.
18548 .endlist
18549
18550 If, for example, the user is specified numerically on the router and there are
18551 no group settings, no gid is available. In this situation, an error occurs.
18552 This is different for the uid, for which there always is an ultimate default.
18553 The first of the following that is set is used:
18554
18555 .ilist
18556 A &%user%& setting of the transport;
18557 .next
18558 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
18559 .next
18560 A &%user%& setting of the router;
18561 .next
18562 A &%check_local_user%& setting of the router;
18563 .next
18564 The Exim uid.
18565 .endlist
18566
18567 Of course, an error will still occur if the uid that is chosen is on the
18568 &%never_users%& list.
18569
18570
18571
18572
18573
18574 .section "Current and home directories" "SECID132"
18575 .cindex "current directory for local transport"
18576 .cindex "home directory" "for local transport"
18577 .cindex "transport" "local; home directory for"
18578 .cindex "transport" "local; current directory for"
18579 Routers may set current and home directories for local transports by means of
18580 the &%transport_current_directory%& and &%transport_home_directory%& options.
18581 However, if the transport's &%current_directory%& or &%home_directory%& options
18582 are set, they override the router's values. In detail, the home directory
18583 for a local transport is taken from the first of these values that is set:
18584
18585 .ilist
18586 The &%home_directory%& option on the transport;
18587 .next
18588 The &%transport_home_directory%& option on the router;
18589 .next
18590 The password data if &%check_local_user%& is set on the router;
18591 .next
18592 The &%router_home_directory%& option on the router.
18593 .endlist
18594
18595 The current directory is taken from the first of these values that is set:
18596
18597 .ilist
18598 The &%current_directory%& option on the transport;
18599 .next
18600 The &%transport_current_directory%& option on the router.
18601 .endlist
18602
18603
18604 If neither the router nor the transport sets a current directory, Exim uses the
18605 value of the home directory, if it is set. Otherwise it sets the current
18606 directory to &_/_& before running a local transport.
18607
18608
18609
18610 .section "Expansion variables derived from the address" "SECID133"
18611 .vindex "&$domain$&"
18612 .vindex "&$local_part$&"
18613 .vindex "&$original_domain$&"
18614 Normally a local delivery is handling a single address, and in that case the
18615 variables such as &$domain$& and &$local_part$& are set during local
18616 deliveries. However, in some circumstances more than one address may be handled
18617 at once (for example, while writing batch SMTP for onward transmission by some
18618 other means). In this case, the variables associated with the local part are
18619 never set, &$domain$& is set only if all the addresses have the same domain,
18620 and &$original_domain$& is never set.
18621 .ecindex IIDenvlotra1
18622 .ecindex IIDenvlotra2
18623 .ecindex IIDenvlotra3
18624
18625
18626
18627
18628
18629
18630
18631 . ////////////////////////////////////////////////////////////////////////////
18632 . ////////////////////////////////////////////////////////////////////////////
18633
18634 .chapter "Generic options for transports" "CHAPtransportgeneric"
18635 .scindex IIDgenoptra1 "generic options" "transport"
18636 .scindex IIDgenoptra2 "options" "generic; for transports"
18637 .scindex IIDgenoptra3 "transport" "generic options for"
18638 The following generic options apply to all transports:
18639
18640
18641 .option body_only transports boolean false
18642 .cindex "transport" "body only"
18643 .cindex "message" "transporting body only"
18644 .cindex "body of message" "transporting"
18645 If this option is set, the message's headers are not transported. It is
18646 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
18647 or &(pipe)& transports, the settings of &%message_prefix%& and
18648 &%message_suffix%& should be checked, because this option does not
18649 automatically suppress them.
18650
18651
18652 .option current_directory transports string&!! unset
18653 .cindex "transport" "current directory for"
18654 This specifies the current directory that is to be set while running the
18655 transport, overriding any value that may have been set by the router.
18656 If the expansion fails for any reason, including forced failure, an error is
18657 logged, and delivery is deferred.
18658
18659
18660 .option disable_logging transports boolean false
18661 If this option is set true, nothing is logged for any
18662 deliveries by the transport or for any
18663 transport errors. You should not set this option unless you really, really know
18664 what you are doing.
18665
18666
18667 .option debug_print transports string&!! unset
18668 .cindex "testing" "variables in drivers"
18669 If this option is set and debugging is enabled (see the &%-d%& command line
18670 option), the string is expanded and included in the debugging output when the
18671 transport is run.
18672 If expansion of the string fails, the error message is written to the debugging
18673 output, and Exim carries on processing.
18674 This facility is provided to help with checking out the values of variables and
18675 so on when debugging driver configurations. For example, if a &%headers_add%&
18676 option is not working properly, &%debug_print%& could be used to output the
18677 variables it references. A newline is added to the text if it does not end with
18678 one.
18679
18680
18681 .option delivery_date_add transports boolean false
18682 .cindex "&'Delivery-date:'& header line"
18683 If this option is true, a &'Delivery-date:'& header is added to the message.
18684 This gives the actual time the delivery was made. As this is not a standard
18685 header, Exim has a configuration option (&%delivery_date_remove%&) which
18686 requests its removal from incoming messages, so that delivered messages can
18687 safely be resent to other recipients.
18688
18689
18690 .option driver transports string unset
18691 This specifies which of the available transport drivers is to be used.
18692 There is no default, and this option must be set for every transport.
18693
18694
18695 .option envelope_to_add transports boolean false
18696 .cindex "&'Envelope-to:'& header line"
18697 If this option is true, an &'Envelope-to:'& header is added to the message.
18698 This gives the original address(es) in the incoming envelope that caused this
18699 delivery to happen. More than one address may be present if the transport is
18700 configured to handle several addresses at once, or if more than one original
18701 address was redirected to the same final address. As this is not a standard
18702 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
18703 its removal from incoming messages, so that delivered messages can safely be
18704 resent to other recipients.
18705
18706
18707 .option group transports string&!! "Exim group"
18708 .cindex "transport" "group; specifying"
18709 This option specifies a gid for running the transport process, overriding any
18710 value that the router supplies, and also overriding any value associated with
18711 &%user%& (see below).
18712
18713
18714 .option headers_add transports string&!! unset
18715 .cindex "header lines" "adding in transport"
18716 .cindex "transport" "header lines; adding"
18717 This option specifies a string of text that is expanded and added to the header
18718 portion of a message as it is transported, as described in section
18719 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
18720 routers. If the result of the expansion is an empty string, or if the expansion
18721 is forced to fail, no action is taken. Other expansion failures are treated as
18722 errors and cause the delivery to be deferred.
18723
18724
18725
18726 .option headers_only transports boolean false
18727 .cindex "transport" "header lines only"
18728 .cindex "message" "transporting headers only"
18729 .cindex "header lines" "transporting"
18730 If this option is set, the message's body is not transported. It is mutually
18731 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
18732 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
18733 checked, since this option does not automatically suppress them.
18734
18735
18736 .option headers_remove transports string&!! unset
18737 .cindex "header lines" "removing"
18738 .cindex "transport" "header lines; removing"
18739 This option specifies a string that is expanded into a list of header names;
18740 these headers are omitted from the message as it is transported, as described
18741 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
18742 routers. If the result of the expansion is an empty string, or if the expansion
18743 is forced to fail, no action is taken. Other expansion failures are treated as
18744 errors and cause the delivery to be deferred.
18745
18746
18747
18748 .option headers_rewrite transports string unset
18749 .cindex "transport" "header lines; rewriting"
18750 .cindex "rewriting" "at transport time"
18751 This option allows addresses in header lines to be rewritten at transport time,
18752 that is, as the message is being copied to its destination. The contents of the
18753 option are a colon-separated list of rewriting rules. Each rule is in exactly
18754 the same form as one of the general rewriting rules that are applied when a
18755 message is received. These are described in chapter &<<CHAPrewrite>>&. For
18756 example,
18757 .code
18758 headers_rewrite = a@b c@d f : \
18759 x@y w@z
18760 .endd
18761 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
18762 &'w@z'& in all address-bearing header lines. The rules are applied to the
18763 header lines just before they are written out at transport time, so they affect
18764 only those copies of the message that pass through the transport. However, only
18765 the message's original header lines, and any that were added by a system
18766 filter, are rewritten. If a router or transport adds header lines, they are not
18767 affected by this option. These rewriting rules are &'not'& applied to the
18768 envelope. You can change the return path using &%return_path%&, but you cannot
18769 change envelope recipients at this time.
18770
18771
18772 .option home_directory transports string&!! unset
18773 .cindex "transport" "home directory for"
18774 .vindex "&$home$&"
18775 This option specifies a home directory setting for a local transport,
18776 overriding any value that may be set by the router. The home directory is
18777 placed in &$home$& while expanding the transport's private options. It is also
18778 used as the current directory if no current directory is set by the
18779 &%current_directory%& option on the transport or the
18780 &%transport_current_directory%& option on the router. If the expansion fails
18781 for any reason, including forced failure, an error is logged, and delivery is
18782 deferred.
18783
18784
18785 .option initgroups transports boolean false
18786 .cindex "additional groups"
18787 .cindex "groups" "additional"
18788 .cindex "transport" "group; additional"
18789 If this option is true and the uid for the delivery process is provided by the
18790 transport, the &[initgroups()]& function is called when running the transport
18791 to ensure that any additional groups associated with the uid are set up.
18792
18793
18794 .option message_size_limit transports string&!! 0
18795 .cindex "limit" "message size per transport"
18796 .cindex "size" "of message, limit"
18797 .cindex "transport" "message size; limiting"
18798 This option controls the size of messages passed through the transport. It is
18799 expanded before use; the result of the expansion must be a sequence of decimal
18800 digits, optionally followed by K or M. If the expansion fails for any reason,
18801 including forced failure, or if the result is not of the required form,
18802 delivery is deferred. If the value is greater than zero and the size of a
18803 message exceeds this limit, the address is failed. If there is any chance that
18804 the resulting bounce message could be routed to the same transport, you should
18805 ensure that &%return_size_limit%& is less than the transport's
18806 &%message_size_limit%&, as otherwise the bounce message will fail to get
18807 delivered.
18808
18809
18810
18811 .option rcpt_include_affixes transports boolean false
18812 .cindex "prefix" "for local part, including in envelope"
18813 .cindex "suffix for local part" "including in envelope"
18814 .cindex "local part" "prefix"
18815 .cindex "local part" "suffix"
18816 When this option is false (the default), and an address that has had any
18817 affixes (prefixes or suffixes) removed from the local part is delivered by any
18818 form of SMTP or LMTP, the affixes are not included. For example, if a router
18819 that contains
18820 .code
18821 local_part_prefix = *-
18822 .endd
18823 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
18824 is delivered with
18825 .code
18826 RCPT TO:<xyz@some.domain>
18827 .endd
18828 This is also the case when an ACL-time callout is being used to verify a
18829 recipient address. However, if &%rcpt_include_affixes%& is set true, the
18830 whole local part is included in the RCPT command. This option applies to BSMTP
18831 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
18832 &(lmtp)& and &(smtp)& transports.
18833
18834
18835 .option retry_use_local_part transports boolean "see below"
18836 .cindex "hints database" "retry keys"
18837 When a delivery suffers a temporary failure, a retry record is created
18838 in Exim's hints database. For remote deliveries, the key for the retry record
18839 is based on the name and/or IP address of the failing remote host. For local
18840 deliveries, the key is normally the entire address, including both the local
18841 part and the domain. This is suitable for most common cases of local delivery
18842 temporary failure &-- for example, exceeding a mailbox quota should delay only
18843 deliveries to that mailbox, not to the whole domain.
18844
18845 However, in some special cases you may want to treat a temporary local delivery
18846 as a failure associated with the domain, and not with a particular local part.
18847 (For example, if you are storing all mail for some domain in files.) You can do
18848 this by setting &%retry_use_local_part%& false.
18849
18850 For all the local transports, its default value is true. For remote transports,
18851 the default value is false for tidiness, but changing the value has no effect
18852 on a remote transport in the current implementation.
18853
18854
18855 .option return_path transports string&!! unset
18856 .cindex "envelope sender"
18857 .cindex "transport" "return path; changing"
18858 .cindex "return path" "changing in transport"
18859 If this option is set, the string is expanded at transport time and replaces
18860 the existing return path (envelope sender) value in the copy of the message
18861 that is being delivered. An empty return path is permitted. This feature is
18862 designed for remote deliveries, where the value of this option is used in the
18863 SMTP MAIL command. If you set &%return_path%& for a local transport, the
18864 only effect is to change the address that is placed in the &'Return-path:'&
18865 header line, if one is added to the message (see the next option).
18866
18867 &*Note:*& A changed return path is not logged unless you add
18868 &%return_path_on_delivery%& to the log selector.
18869
18870 .vindex "&$return_path$&"
18871 The expansion can refer to the existing value via &$return_path$&. This is
18872 either the message's envelope sender, or an address set by the
18873 &%errors_to%& option on a router. If the expansion is forced to fail, no
18874 replacement occurs; if it fails for another reason, delivery is deferred. This
18875 option can be used to support VERP (Variable Envelope Return Paths) &-- see
18876 section &<<SECTverp>>&.
18877
18878 &*Note*&: If a delivery error is detected locally, including the case when a
18879 remote server rejects a message at SMTP time, the bounce message is not sent to
18880 the value of this option. It is sent to the previously set errors address.
18881 This defaults to the incoming sender address, but can be changed by setting
18882 &%errors_to%& in a router.
18883
18884
18885
18886 .option return_path_add transports boolean false
18887 .cindex "&'Return-path:'& header line"
18888 If this option is true, a &'Return-path:'& header is added to the message.
18889 Although the return path is normally available in the prefix line of BSD
18890 mailboxes, this is commonly not displayed by MUAs, and so the user does not
18891 have easy access to it.
18892
18893 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
18894 the delivery SMTP server makes the final delivery"&. This implies that this
18895 header should not be present in incoming messages. Exim has a configuration
18896 option, &%return_path_remove%&, which requests removal of this header from
18897 incoming messages, so that delivered messages can safely be resent to other
18898 recipients.
18899
18900
18901 .option shadow_condition transports string&!! unset
18902 See &%shadow_transport%& below.
18903
18904
18905 .option shadow_transport transports string unset
18906 .cindex "shadow transport"
18907 .cindex "transport" "shadow"
18908 A local transport may set the &%shadow_transport%& option to the name of
18909 another local transport. Shadow remote transports are not supported.
18910
18911 Whenever a delivery to the main transport succeeds, and either
18912 &%shadow_condition%& is unset, or its expansion does not result in the empty
18913 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
18914 passed to the shadow transport, with the same delivery address or addresses. If
18915 expansion fails, no action is taken except that non-forced expansion failures
18916 cause a log line to be written.
18917
18918 The result of the shadow transport is discarded and does not affect the
18919 subsequent processing of the message. Only a single level of shadowing is
18920 provided; the &%shadow_transport%& option is ignored on any transport when it
18921 is running as a shadow. Options concerned with output from pipes are also
18922 ignored. The log line for the successful delivery has an item added on the end,
18923 of the form
18924 .code
18925 ST=<shadow transport name>
18926 .endd
18927 If the shadow transport did not succeed, the error message is put in
18928 parentheses afterwards. Shadow transports can be used for a number of different
18929 purposes, including keeping more detailed log information than Exim normally
18930 provides, and implementing automatic acknowledgment policies based on message
18931 headers that some sites insist on.
18932
18933
18934 .option transport_filter transports string&!! unset
18935 .cindex "transport" "filter"
18936 .cindex "filter" "transport filter"
18937 This option sets up a filtering (in the Unix shell sense) process for messages
18938 at transport time. It should not be confused with mail filtering as set up by
18939 individual users or via a system filter.
18940
18941 When the message is about to be written out, the command specified by
18942 &%transport_filter%& is started up in a separate, parallel process, and
18943 the entire message, including the header lines, is passed to it on its standard
18944 input (this in fact is done from a third process, to avoid deadlock). The
18945 command must be specified as an absolute path.
18946
18947 The lines of the message that are written to the transport filter are
18948 terminated by newline (&"\n"&). The message is passed to the filter before any
18949 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
18950 lines beginning with a dot, and also before any processing implied by the
18951 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
18952 &(pipe)& transports.
18953
18954 The standard error for the filter process is set to the same destination as its
18955 standard output; this is read and written to the message's ultimate
18956 destination. The process that writes the message to the filter, the
18957 filter itself, and the original process that reads the result and delivers it
18958 are all run in parallel, like a shell pipeline.
18959
18960 The filter can perform any transformations it likes, but of course should take
18961 care not to break RFC 2822 syntax. A demonstration Perl script is provided in
18962 &_util/transport-filter.pl_&; this makes a few arbitrary modifications just to
18963 show the possibilities. Exim does not check the result, except to test for a
18964 final newline when SMTP is in use. All messages transmitted over SMTP must end
18965 with a newline, so Exim supplies one if it is missing.
18966
18967 .cindex "content scanning" "per user"
18968 A transport filter can be used to provide content-scanning on a per-user basis
18969 at delivery time if the only required effect of the scan is to modify the
18970 message. For example, a content scan could insert a new header line containing
18971 a spam score. This could be interpreted by a filter in the user's MUA. It is
18972 not possible to discard a message at this stage.
18973
18974 .cindex "SMTP" "SIZE"
18975 A problem might arise if the filter increases the size of a message that is
18976 being sent down an SMTP connection. If the receiving SMTP server has indicated
18977 support for the SIZE parameter, Exim will have sent the size of the message
18978 at the start of the SMTP session. If what is actually sent is substantially
18979 more, the server might reject the message. This can be worked round by setting
18980 the &%size_addition%& option on the &(smtp)& transport, either to allow for
18981 additions to the message, or to disable the use of SIZE altogether.
18982
18983 .vindex "&$pipe_addresses$&"
18984 The value of the &%transport_filter%& option is the command string for starting
18985 the filter, which is run directly from Exim, not under a shell. The string is
18986 parsed by Exim in the same way as a command string for the &(pipe)& transport:
18987 Exim breaks it up into arguments and then expands each argument separately (see
18988 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
18989 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
18990 of arguments, one for each address that applies to this delivery. (This isn't
18991 an ideal name for this feature here, but as it was already implemented for the
18992 &(pipe)& transport, it seemed sensible not to change it.)
18993
18994 .vindex "&$host$&"
18995 .vindex "&$host_address$&"
18996 The expansion variables &$host$& and &$host_address$& are available when the
18997 transport is a remote one. They contain the name and IP address of the host to
18998 which the message is being sent. For example:
18999 .code
19000 transport_filter = /some/directory/transport-filter.pl \
19001 $host $host_address $sender_address $pipe_addresses
19002 .endd
19003
19004 Two problems arise if you want to use more complicated expansion items to
19005 generate transport filter commands, both of which due to the fact that the
19006 command is split up &'before'& expansion.
19007 .ilist
19008 If an expansion item contains white space, you must quote it, so that it is all
19009 part of the same command item. If the entire option setting is one such
19010 expansion item, you have to take care what kind of quoting you use. For
19011 example:
19012 .code
19013 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
19014 .endd
19015 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
19016 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
19017 stripped by Exim when it read the option's value. When the value is used, if
19018 the single quotes were missing, the line would be split into two items,
19019 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
19020 Exim tried to expand the first one.
19021 .next
19022 Except for the special case of &$pipe_addresses$& that is mentioned above, an
19023 expansion cannot generate multiple arguments, or a command name followed by
19024 arguments. Consider this example:
19025 .code
19026 transport_filter = ${lookup{$host}lsearch{/a/file}\
19027 {$value}{/bin/cat}}
19028 .endd
19029 The result of the lookup is interpreted as the name of the command, even
19030 if it contains white space. The simplest way round this is to use a shell:
19031 .code
19032 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
19033 {$value}{/bin/cat}}
19034 .endd
19035 .endlist
19036
19037 The filter process is run under the same uid and gid as the normal delivery.
19038 For remote deliveries this is the Exim uid/gid by default. The command should
19039 normally yield a zero return code. Transport filters are not supposed to fail.
19040 A non-zero code is taken to mean that the transport filter encountered some
19041 serious problem. Delivery of the message is deferred; the message remains on
19042 the queue and is tried again later. It is not possible to cause a message to be
19043 bounced from a transport filter.
19044
19045 If a transport filter is set on an autoreply transport, the original message is
19046 passed through the filter as it is being copied into the newly generated
19047 message, which happens if the &%return_message%& option is set.
19048
19049
19050 .option transport_filter_timeout transports time 5m
19051 .cindex "transport" "filter, timeout"
19052 When Exim is reading the output of a transport filter, it a applies a timeout
19053 that can be set by this option. Exceeding the timeout is normally treated as a
19054 temporary delivery failure. However, if a transport filter is used with a
19055 &(pipe)& transport, a timeout in the transport filter is treated in the same
19056 way as a timeout in the pipe command itself. By default, a timeout is a hard
19057 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
19058 becomes a temporary error.
19059
19060
19061 .option user transports string&!! "Exim user"
19062 .cindex "uid (user id)" "local delivery"
19063 .cindex "transport" "user, specifying"
19064 This option specifies the user under whose uid the delivery process is to be
19065 run, overriding any uid that may have been set by the router. If the user is
19066 given as a name, the uid is looked up from the password data, and the
19067 associated group is taken as the value of the gid to be used if the &%group%&
19068 option is not set.
19069
19070 For deliveries that use local transports, a user and group are normally
19071 specified explicitly or implicitly (for example, as a result of
19072 &%check_local_user%&) by the router or transport.
19073
19074 .cindex "hints database" "access by remote transport"
19075 For remote transports, you should leave this option unset unless you really are
19076 sure you know what you are doing. When a remote transport is running, it needs
19077 to be able to access Exim's hints databases, because each host may have its own
19078 retry data.
19079 .ecindex IIDgenoptra1
19080 .ecindex IIDgenoptra2
19081 .ecindex IIDgenoptra3
19082
19083
19084
19085
19086
19087
19088 . ////////////////////////////////////////////////////////////////////////////
19089 . ////////////////////////////////////////////////////////////////////////////
19090
19091 .chapter "Address batching in local transports" "CHAPbatching" &&&
19092 "Address batching"
19093 .cindex "transport" "local; address batching in"
19094 The only remote transport (&(smtp)&) is normally configured to handle more than
19095 one address at a time, so that when several addresses are routed to the same
19096 remote host, just one copy of the message is sent. Local transports, however,
19097 normally handle one address at a time. That is, a separate instance of the
19098 transport is run for each address that is routed to the transport. A separate
19099 copy of the message is delivered each time.
19100
19101 .cindex "batched local delivery"
19102 .oindex "&%batch_max%&"
19103 .oindex "&%batch_id%&"
19104 In special cases, it may be desirable to handle several addresses at once in a
19105 local transport, for example:
19106
19107 .ilist
19108 In an &(appendfile)& transport, when storing messages in files for later
19109 delivery by some other means, a single copy of the message with multiple
19110 recipients saves space.
19111 .next
19112 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
19113 a single copy saves time, and is the normal way LMTP is expected to work.
19114 .next
19115 In a &(pipe)& transport, when passing the message
19116 to a scanner program or
19117 to some other delivery mechanism such as UUCP, multiple recipients may be
19118 acceptable.
19119 .endlist
19120
19121 These three local transports all have the same options for controlling multiple
19122 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
19123 repeating the information for each transport, these options are described here.
19124
19125 The &%batch_max%& option specifies the maximum number of addresses that can be
19126 delivered together in a single run of the transport. Its default value is one
19127 (no batching). When more than one address is routed to a transport that has a
19128 &%batch_max%& value greater than one, the addresses are delivered in a batch
19129 (that is, in a single run of the transport with multiple recipients), subject
19130 to certain conditions:
19131
19132 .ilist
19133 .vindex "&$local_part$&"
19134 If any of the transport's options contain a reference to &$local_part$&, no
19135 batching is possible.
19136 .next
19137 .vindex "&$domain$&"
19138 If any of the transport's options contain a reference to &$domain$&, only
19139 addresses with the same domain are batched.
19140 .next
19141 .cindex "customizing" "batching condition"
19142 If &%batch_id%& is set, it is expanded for each address, and only those
19143 addresses with the same expanded value are batched. This allows you to specify
19144 customized batching conditions. Failure of the expansion for any reason,
19145 including forced failure, disables batching, but it does not stop the delivery
19146 from taking place.
19147 .next
19148 Batched addresses must also have the same errors address (where to send
19149 delivery errors), the same header additions and removals, the same user and
19150 group for the transport, and if a host list is present, the first host must
19151 be the same.
19152 .endlist
19153
19154 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
19155 both when the file or pipe command is specified in the transport, and when it
19156 is specified by a &(redirect)& router, but all the batched addresses must of
19157 course be routed to the same file or pipe command. These two transports have an
19158 option called &%use_bsmtp%&, which causes them to deliver the message in
19159 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
19160 &%check_string%& and &%escape_string%& options are forced to the values
19161 .code
19162 check_string = "."
19163 escape_string = ".."
19164 .endd
19165 when batched SMTP is in use. A full description of the batch SMTP mechanism is
19166 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
19167 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
19168
19169 .cindex "&'Envelope-to:'& header line"
19170 If the generic &%envelope_to_add%& option is set for a batching transport, the
19171 &'Envelope-to:'& header that is added to the message contains all the addresses
19172 that are being processed together. If you are using a batching &(appendfile)&
19173 transport without &%use_bsmtp%&, the only way to preserve the recipient
19174 addresses is to set the &%envelope_to_add%& option.
19175
19176 .cindex "&(pipe)& transport" "with multiple addresses"
19177 .vindex "&$pipe_addresses$&"
19178 If you are using a &(pipe)& transport without BSMTP, and setting the
19179 transport's &%command%& option, you can include &$pipe_addresses$& as part of
19180 the command. This is not a true variable; it is a bit of magic that causes each
19181 of the recipient addresses to be inserted into the command as a separate
19182 argument. This provides a way of accessing all the addresses that are being
19183 delivered in the batch. &*Note:*& This is not possible for pipe commands that
19184 are specified by a &(redirect)& router.
19185
19186
19187
19188
19189 . ////////////////////////////////////////////////////////////////////////////
19190 . ////////////////////////////////////////////////////////////////////////////
19191
19192 .chapter "The appendfile transport" "CHAPappendfile"
19193 .scindex IIDapptra1 "&(appendfile)& transport"
19194 .scindex IIDapptra2 "transports" "&(appendfile)&"
19195 .cindex "directory creation"
19196 .cindex "creating directories"
19197 The &(appendfile)& transport delivers a message by appending it to an existing
19198 file, or by creating an entirely new file in a specified directory. Single
19199 files to which messages are appended can be in the traditional Unix mailbox
19200 format, or optionally in the MBX format supported by the Pine MUA and
19201 University of Washington IMAP daemon, &'inter alia'&. When each message is
19202 being delivered as a separate file, &"maildir"& format can optionally be used
19203 to give added protection against failures that happen part-way through the
19204 delivery. A third form of separate-file delivery known as &"mailstore"& is also
19205 supported. For all file formats, Exim attempts to create as many levels of
19206 directory as necessary, provided that &%create_directory%& is set.
19207
19208 The code for the optional formats is not included in the Exim binary by
19209 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
19210 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
19211 included.
19212
19213 .cindex "quota" "system"
19214 Exim recognizes system quota errors, and generates an appropriate message. Exim
19215 also supports its own quota control within the transport, for use when the
19216 system facility is unavailable or cannot be used for some reason.
19217
19218 If there is an error while appending to a file (for example, quota exceeded or
19219 partition filled), Exim attempts to reset the file's length and last
19220 modification time back to what they were before. If there is an error while
19221 creating an entirely new file, the new file is removed.
19222
19223 Before appending to a file, a number of security checks are made, and the
19224 file is locked. A detailed description is given below, after the list of
19225 private options.
19226
19227 The &(appendfile)& transport is most commonly used for local deliveries to
19228 users' mailboxes. However, it can also be used as a pseudo-remote transport for
19229 putting messages into files for remote delivery by some means other than Exim.
19230 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
19231 option).
19232
19233
19234
19235 .section "The file and directory options" "SECTfildiropt"
19236 The &%file%& option specifies a single file, to which the message is appended;
19237 the &%directory%& option specifies a directory, in which a new file containing
19238 the message is created. Only one of these two options can be set, and for
19239 normal deliveries to mailboxes, one of them &'must'& be set.
19240
19241 .vindex "&$address_file$&"
19242 .vindex "&$local_part$&"
19243 However, &(appendfile)& is also used for delivering messages to files or
19244 directories whose names (or parts of names) are obtained from alias,
19245 forwarding, or filtering operations (for example, a &%save%& command in a
19246 user's Exim filter). When such a transport is running, &$local_part$& contains
19247 the local part that was aliased or forwarded, and &$address_file$& contains the
19248 name (or partial name) of the file or directory generated by the redirection
19249 operation. There are two cases:
19250
19251 .ilist
19252 If neither &%file%& nor &%directory%& is set, the redirection operation
19253 must specify an absolute path (one that begins with &`/`&). This is the most
19254 common case when users with local accounts use filtering to sort mail into
19255 different folders. See for example, the &(address_file)& transport in the
19256 default configuration. If the path ends with a slash, it is assumed to be the
19257 name of a directory. A delivery to a directory can also be forced by setting
19258 &%maildir_format%& or &%mailstore_format%&.
19259 .next
19260 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
19261 used to determine the file or directory name for the delivery. Normally, the
19262 contents of &$address_file$& are used in some way in the string expansion.
19263 .endlist
19264
19265
19266 .cindex "Sieve filter" "configuring &(appendfile)&"
19267 .cindex "Sieve filter" "relative mailbox path handling"
19268 As an example of the second case, consider an environment where users do not
19269 have home directories. They may be permitted to use Exim filter commands of the
19270 form:
19271 .code
19272 save folder23
19273 .endd
19274 or Sieve filter commands of the form:
19275 .code
19276 require "fileinto";
19277 fileinto "folder23";
19278 .endd
19279 In this situation, the expansion of &%file%& or &%directory%& in the transport
19280 must transform the relative path into an appropriate absolute file name. In the
19281 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
19282 is used as a result of a &"keep"& action in the filter. This example shows one
19283 way of handling this requirement:
19284 .code
19285 file = ${if eq{$address_file}{inbox} \
19286 {/var/mail/$local_part} \
19287 {${if eq{${substr_0_1:$address_file}}{/} \
19288 {$address_file} \
19289 {$home/mail/$address_file} \
19290 }} \
19291 }
19292 .endd
19293 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
19294 location, absolute paths are used without change, and other folders are in the
19295 &_mail_& directory within the home directory.
19296
19297 &*Note 1*&: While processing an Exim filter, a relative path such as
19298 &_folder23_& is turned into an absolute path if a home directory is known to
19299 the router. In particular, this is the case if &%check_local_user%& is set. If
19300 you want to prevent this happening at routing time, you can set
19301 &%router_home_directory%& empty. This forces the router to pass the relative
19302 path to the transport.
19303
19304 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
19305 the &%file%& or &%directory%& option is still used if it is set.
19306
19307
19308
19309
19310 .section "Private options for appendfile" "SECID134"
19311 .cindex "options" "&(appendfile)& transport"
19312
19313
19314
19315 .option allow_fifo appendfile boolean false
19316 .cindex "fifo (named pipe)"
19317 .cindex "named pipe (fifo)"
19318 .cindex "pipe" "named (fifo)"
19319 Setting this option permits delivery to named pipes (FIFOs) as well as to
19320 regular files. If no process is reading the named pipe at delivery time, the
19321 delivery is deferred.
19322
19323
19324 .option allow_symlink appendfile boolean false
19325 .cindex "symbolic link" "to mailbox"
19326 .cindex "mailbox" "symbolic link"
19327 By default, &(appendfile)& will not deliver if the path name for the file is
19328 that of a symbolic link. Setting this option relaxes that constraint, but there
19329 are security issues involved in the use of symbolic links. Be sure you know
19330 what you are doing if you set this. Details of exactly what this option affects
19331 are included in the discussion which follows this list of options.
19332
19333
19334 .option batch_id appendfile string&!! unset
19335 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
19336 However, batching is automatically disabled for &(appendfile)& deliveries that
19337 happen as a result of forwarding or aliasing or other redirection directly to a
19338 file.
19339
19340
19341 .option batch_max appendfile integer 1
19342 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
19343
19344
19345 .option check_group appendfile boolean false
19346 When this option is set, the group owner of the file defined by the &%file%&
19347 option is checked to see that it is the same as the group under which the
19348 delivery process is running. The default setting is false because the default
19349 file mode is 0600, which means that the group is irrelevant.
19350
19351
19352 .option check_owner appendfile boolean true
19353 When this option is set, the owner of the file defined by the &%file%& option
19354 is checked to ensure that it is the same as the user under which the delivery
19355 process is running.
19356
19357
19358 .option check_string appendfile string "see below"
19359 .cindex "&""From""& line"
19360 As &(appendfile)& writes the message, the start of each line is tested for
19361 matching &%check_string%&, and if it does, the initial matching characters are
19362 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
19363 a literal string, not a regular expression, and the case of any letters it
19364 contains is significant.
19365
19366 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
19367 are forced to &"."& and &".."& respectively, and any settings in the
19368 configuration are ignored. Otherwise, they default to &"From&~"& and
19369 &">From&~"& when the &%file%& option is set, and unset when any of the
19370 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
19371
19372 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
19373 suitable for traditional &"BSD"& mailboxes, where a line beginning with
19374 &"From&~"& indicates the start of a new message. All four options need changing
19375 if another format is used. For example, to deliver to mailboxes in MMDF format:
19376 .cindex "MMDF format mailbox"
19377 .cindex "mailbox" "MMDF format"
19378 .code
19379 check_string = "\1\1\1\1\n"
19380 escape_string = "\1\1\1\1 \n"
19381 message_prefix = "\1\1\1\1\n"
19382 message_suffix = "\1\1\1\1\n"
19383 .endd
19384 .option create_directory appendfile boolean true
19385 .cindex "directory creation"
19386 When this option is true, Exim attempts to create any missing superior
19387 directories for the file that it is about to write. A created directory's mode
19388 is given by the &%directory_mode%& option.
19389
19390 The group ownership of a newly created directory is highly dependent on the
19391 operating system (and possibly the file system) that is being used. For
19392 example, in Solaris, if the parent directory has the setgid bit set, its group
19393 is propagated to the child; if not, the currently set group is used. However,
19394 in FreeBSD, the parent's group is always used.
19395
19396
19397
19398 .option create_file appendfile string anywhere
19399 This option constrains the location of files and directories that are created
19400 by this transport. It applies to files defined by the &%file%& option and
19401 directories defined by the &%directory%& option. In the case of maildir
19402 delivery, it applies to the top level directory, not the maildir directories
19403 beneath.
19404
19405 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
19406 &"belowhome"&. In the second and third cases, a home directory must have been
19407 set for the transport. This option is not useful when an explicit file name is
19408 given for normal mailbox deliveries. It is intended for the case when file
19409 names are generated from users' &_.forward_& files. These are usually handled
19410 by an &(appendfile)& transport called &%address_file%&. See also
19411 &%file_must_exist%&.
19412
19413
19414 .option directory appendfile string&!! unset
19415 This option is mutually exclusive with the &%file%& option, but one of &%file%&
19416 or &%directory%& must be set, unless the delivery is the direct result of a
19417 redirection (see section &<<SECTfildiropt>>&).
19418
19419 When &%directory%& is set, the string is expanded, and the message is delivered
19420 into a new file or files in or below the given directory, instead of being
19421 appended to a single mailbox file. A number of different formats are provided
19422 (see &%maildir_format%& and &%mailstore_format%&), and see section
19423 &<<SECTopdir>>& for further details of this form of delivery.
19424
19425
19426 .option directory_file appendfile string&!! "see below"
19427 .cindex "base62"
19428 .vindex "&$inode$&"
19429 When &%directory%& is set, but neither &%maildir_format%& nor
19430 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
19431 whose name is obtained by expanding this string. The default value is:
19432 .code
19433 q${base62:$tod_epoch}-$inode
19434 .endd
19435 This generates a unique name from the current time, in base 62 form, and the
19436 inode of the file. The variable &$inode$& is available only when expanding this
19437 option.
19438
19439
19440 .option directory_mode appendfile "octal integer" 0700
19441 If &(appendfile)& creates any directories as a result of the
19442 &%create_directory%& option, their mode is specified by this option.
19443
19444
19445 .option escape_string appendfile string "see description"
19446 See &%check_string%& above.
19447
19448
19449 .option file appendfile string&!! unset
19450 This option is mutually exclusive with the &%directory%& option, but one of
19451 &%file%& or &%directory%& must be set, unless the delivery is the direct result
19452 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
19453 specifies a single file, to which the message is appended. One or more of
19454 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
19455 &%file%&.
19456
19457 .cindex "NFS" "lock file"
19458 .cindex "locking files"
19459 .cindex "lock files"
19460 If you are using more than one host to deliver over NFS into the same
19461 mailboxes, you should always use lock files.
19462
19463 The string value is expanded for each delivery, and must yield an absolute
19464 path. The most common settings of this option are variations on one of these
19465 examples:
19466 .code
19467 file = /var/spool/mail/$local_part
19468 file = /home/$local_part/inbox
19469 file = $home/inbox
19470 .endd
19471 .cindex "&""sticky""& bit"
19472 In the first example, all deliveries are done into the same directory. If Exim
19473 is configured to use lock files (see &%use_lockfile%& below) it must be able to
19474 create a file in the directory, so the &"sticky"& bit must be turned on for
19475 deliveries to be possible, or alternatively the &%group%& option can be used to
19476 run the delivery under a group id which has write access to the directory.
19477
19478
19479
19480 .option file_format appendfile string unset
19481 .cindex "file" "mailbox; checking existing format"
19482 This option requests the transport to check the format of an existing file
19483 before adding to it. The check consists of matching a specific string at the
19484 start of the file. The value of the option consists of an even number of
19485 colon-separated strings. The first of each pair is the test string, and the
19486 second is the name of a transport. If the transport associated with a matched
19487 string is not the current transport, control is passed over to the other
19488 transport. For example, suppose the standard &(local_delivery)& transport has
19489 this added to it:
19490 .code
19491 file_format = "From : local_delivery :\
19492 \1\1\1\1\n : local_mmdf_delivery"
19493 .endd
19494 Mailboxes that begin with &"From"& are still handled by this transport, but if
19495 a mailbox begins with four binary ones followed by a newline, control is passed
19496 to a transport called &%local_mmdf_delivery%&, which presumably is configured
19497 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
19498 is assumed to match the current transport. If the start of a mailbox doesn't
19499 match any string, or if the transport named for a given string is not defined,
19500 delivery is deferred.
19501
19502
19503 .option file_must_exist appendfile boolean false
19504 If this option is true, the file specified by the &%file%& option must exist.
19505 A temporary error occurs if it does not, causing delivery to be deferred.
19506 If this option is false, the file is created if it does not exist.
19507
19508
19509 .option lock_fcntl_timeout appendfile time 0s
19510 .cindex "timeout" "mailbox locking"
19511 .cindex "mailbox" "locking, blocking and non-blocking"
19512 .cindex "locking files"
19513 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
19514 when locking an open mailbox file. If the call fails, the delivery process
19515 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
19516 Non-blocking calls are used so that the file is not kept open during the wait
19517 for the lock; the reason for this is to make it as safe as possible for
19518 deliveries over NFS in the case when processes might be accessing an NFS
19519 mailbox without using a lock file. This should not be done, but
19520 misunderstandings and hence misconfigurations are not unknown.
19521
19522 On a busy system, however, the performance of a non-blocking lock approach is
19523 not as good as using a blocking lock with a timeout. In this case, the waiting
19524 is done inside the system call, and Exim's delivery process acquires the lock
19525 and can proceed as soon as the previous lock holder releases it.
19526
19527 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
19528 timeout, are used. There may still be some retrying: the maximum number of
19529 retries is
19530 .code
19531 (lock_retries * lock_interval) / lock_fcntl_timeout
19532 .endd
19533 rounded up to the next whole number. In other words, the total time during
19534 which &(appendfile)& is trying to get a lock is roughly the same, unless
19535 &%lock_fcntl_timeout%& is set very large.
19536
19537 You should consider setting this option if you are getting a lot of delayed
19538 local deliveries because of errors of the form
19539 .code
19540 failed to lock mailbox /some/file (fcntl)
19541 .endd
19542
19543 .option lock_flock_timeout appendfile time 0s
19544 This timeout applies to file locking when using &[flock()]& (see
19545 &%use_flock%&); the timeout operates in a similar manner to
19546 &%lock_fcntl_timeout%&.
19547
19548
19549 .option lock_interval appendfile time 3s
19550 This specifies the time to wait between attempts to lock the file. See below
19551 for details of locking.
19552
19553
19554 .option lock_retries appendfile integer 10
19555 This specifies the maximum number of attempts to lock the file. A value of zero
19556 is treated as 1. See below for details of locking.
19557
19558
19559 .option lockfile_mode appendfile "octal integer" 0600
19560 This specifies the mode of the created lock file, when a lock file is being
19561 used (see &%use_lockfile%& and &%use_mbx_lock%&).
19562
19563
19564 .option lockfile_timeout appendfile time 30m
19565 .cindex "timeout" "mailbox locking"
19566 When a lock file is being used (see &%use_lockfile%&), if a lock file already
19567 exists and is older than this value, it is assumed to have been left behind by
19568 accident, and Exim attempts to remove it.
19569
19570
19571 .option mailbox_filecount appendfile string&!! unset
19572 .cindex "mailbox" "specifying size of"
19573 .cindex "size" "of mailbox"
19574 If this option is set, it is expanded, and the result is taken as the current
19575 number of files in the mailbox. It must be a decimal number, optionally
19576 followed by K or M. This provides a way of obtaining this information from an
19577 external source that maintains the data.
19578
19579
19580 .option mailbox_size appendfile string&!! unset
19581 .cindex "mailbox" "specifying size of"
19582 .cindex "size" "of mailbox"
19583 If this option is set, it is expanded, and the result is taken as the current
19584 size the mailbox. It must be a decimal number, optionally followed by K or M.
19585 This provides a way of obtaining this information from an external source that
19586 maintains the data. This is likely to be helpful for maildir deliveries where
19587 it is computationally expensive to compute the size of a mailbox.
19588
19589
19590
19591 .option maildir_format appendfile boolean false
19592 .cindex "maildir format" "specifying"
19593 If this option is set with the &%directory%& option, the delivery is into a new
19594 file, in the &"maildir"& format that is used by other mail software. When the
19595 transport is activated directly from a &(redirect)& router (for example, the
19596 &(address_file)& transport in the default configuration), setting
19597 &%maildir_format%& causes the path received from the router to be treated as a
19598 directory, whether or not it ends with &`/`&. This option is available only if
19599 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
19600 &<<SECTmaildirdelivery>>& below for further details.
19601
19602
19603 .option maildir_quota_directory_regex appendfile string "See below"
19604 .cindex "maildir format" "quota; directories included in"
19605 .cindex "quota" "maildir; directories included in"
19606 This option is relevant only when &%maildir_use_size_file%& is set. It defines
19607 a regular expression for specifying directories, relative to the quota
19608 directory (see &%quota_directory%&), that should be included in the quota
19609 calculation. The default value is:
19610 .code
19611 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
19612 .endd
19613 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
19614 (directories whose names begin with a dot). If you want to exclude the
19615 &_Trash_&
19616 folder from the count (as some sites do), you need to change this setting to
19617 .code
19618 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
19619 .endd
19620 This uses a negative lookahead in the regular expression to exclude the
19621 directory whose name is &_.Trash_&. When a directory is excluded from quota
19622 calculations, quota processing is bypassed for any messages that are delivered
19623 directly into that directory.
19624
19625
19626 .option maildir_retries appendfile integer 10
19627 This option specifies the number of times to retry when writing a file in
19628 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
19629
19630
19631 .option maildir_tag appendfile string&!! unset
19632 This option applies only to deliveries in maildir format, and is described in
19633 section &<<SECTmaildirdelivery>>& below.
19634
19635
19636 .option maildir_use_size_file appendfile boolean false
19637 .cindex "maildir format" "&_maildirsize_& file"
19638 Setting this option true enables support for &_maildirsize_& files. Exim
19639 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
19640 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
19641 value is zero. See &%maildir_quota_directory_regex%& above and section
19642 &<<SECTmaildirdelivery>>& below for further details.
19643
19644 .option maildirfolder_create_regex appendfile string unset
19645 .cindex "maildir format" "&_maildirfolder_& file"
19646 .cindex "&_maildirfolder_&, creating"
19647 The value of this option is a regular expression. If it is unset, it has no
19648 effect. Otherwise, before a maildir delivery takes place, the pattern is
19649 matched against the name of the maildir directory, that is, the directory
19650 containing the &_new_& and &_tmp_& subdirectories that will be used for the
19651 delivery. If there is a match, Exim checks for the existence of a file called
19652 &_maildirfolder_& in the directory, and creates it if it does not exist.
19653 See section &<<SECTmaildirdelivery>>& for more details.
19654
19655
19656 .option mailstore_format appendfile boolean false
19657 .cindex "mailstore format" "specifying"
19658 If this option is set with the &%directory%& option, the delivery is into two
19659 new files in &"mailstore"& format. The option is available only if
19660 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
19661 below for further details.
19662
19663
19664 .option mailstore_prefix appendfile string&!! unset
19665 This option applies only to deliveries in mailstore format, and is described in
19666 section &<<SECTopdir>>& below.
19667
19668
19669 .option mailstore_suffix appendfile string&!! unset
19670 This option applies only to deliveries in mailstore format, and is described in
19671 section &<<SECTopdir>>& below.
19672
19673
19674 .option mbx_format appendfile boolean false
19675 .cindex "locking files"
19676 .cindex "file" "locking"
19677 .cindex "file" "MBX format"
19678 .cindex "MBX format, specifying"
19679 This option is available only if Exim has been compiled with SUPPORT_MBX
19680 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
19681 the message is appended to the mailbox file in MBX format instead of
19682 traditional Unix format. This format is supported by Pine4 and its associated
19683 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
19684
19685 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
19686 automatically changed by the use of &%mbx_format%&. They should normally be set
19687 empty when using MBX format, so this option almost always appears in this
19688 combination:
19689 .code
19690 mbx_format = true
19691 message_prefix =
19692 message_suffix =
19693 .endd
19694 If none of the locking options are mentioned in the configuration,
19695 &%use_mbx_lock%& is assumed and the other locking options default to false. It
19696 is possible to specify the other kinds of locking with &%mbx_format%&, but
19697 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
19698 interworks with &'c-client'&, providing for shared access to the mailbox. It
19699 should not be used if any program that does not use this form of locking is
19700 going to access the mailbox, nor should it be used if the mailbox file is NFS
19701 mounted, because it works only when the mailbox is accessed from a single host.
19702
19703 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
19704 the standard version of &'c-client'&, because as long as it has a mailbox open
19705 (this means for the whole of a Pine or IMAP session), Exim will not be able to
19706 append messages to it.
19707
19708
19709 .option message_prefix appendfile string&!! "see below"
19710 .cindex "&""From""& line"
19711 The string specified here is expanded and output at the start of every message.
19712 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
19713 in which case it is:
19714 .code
19715 message_prefix = "From ${if def:return_path{$return_path}\
19716 {MAILER-DAEMON}} $tod_bsdinbox\n"
19717 .endd
19718 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
19719 &`\n`& to &`\r\n`& in &%message_prefix%&.
19720
19721 .option message_suffix appendfile string&!! "see below"
19722 The string specified here is expanded and output at the end of every message.
19723 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
19724 in which case it is a single newline character. The suffix can be suppressed by
19725 setting
19726 .code
19727 message_suffix =
19728 .endd
19729 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
19730 &`\n`& to &`\r\n`& in &%message_suffix%&.
19731
19732 .option mode appendfile "octal integer" 0600
19733 If the output file is created, it is given this mode. If it already exists and
19734 has wider permissions, they are reduced to this mode. If it has narrower
19735 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
19736 if the delivery is the result of a &%save%& command in a filter file specifying
19737 a particular mode, the mode of the output file is always forced to take that
19738 value, and this option is ignored.
19739
19740
19741 .option mode_fail_narrower appendfile boolean true
19742 This option applies in the case when an existing mailbox file has a narrower
19743 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
19744 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
19745 continues with the delivery attempt, using the existing mode of the file.
19746
19747
19748 .option notify_comsat appendfile boolean false
19749 If this option is true, the &'comsat'& daemon is notified after every
19750 successful delivery to a user mailbox. This is the daemon that notifies logged
19751 on users about incoming mail.
19752
19753
19754 .option quota appendfile string&!! unset
19755 .cindex "quota" "imposed by Exim"
19756 This option imposes a limit on the size of the file to which Exim is appending,
19757 or to the total space used in the directory tree when the &%directory%& option
19758 is set. In the latter case, computation of the space used is expensive, because
19759 all the files in the directory (and any sub-directories) have to be
19760 individually inspected and their sizes summed. (See &%quota_size_regex%& and
19761 &%maildir_use_size_file%& for ways to avoid this in environments where users
19762 have no shell access to their mailboxes).
19763
19764 As there is no interlock against two simultaneous deliveries into a
19765 multi-file mailbox, it is possible for the quota to be overrun in this case.
19766 For single-file mailboxes, of course, an interlock is a necessity.
19767
19768 A file's size is taken as its &'used'& value. Because of blocking effects, this
19769 may be a lot less than the actual amount of disk space allocated to the file.
19770 If the sizes of a number of files are being added up, the rounding effect can
19771 become quite noticeable, especially on systems that have large block sizes.
19772 Nevertheless, it seems best to stick to the &'used'& figure, because this is
19773 the obvious value which users understand most easily.
19774
19775 The value of the option is expanded, and must then be a numerical value
19776 (decimal point allowed), optionally followed by one of the letters K, M, or G,
19777 for kilobytes, megabytes, or gigabytes. If Exim is running on a system with
19778 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
19779 be handled.
19780
19781 &*Note*&: A value of zero is interpreted as &"no quota"&.
19782
19783 The expansion happens while Exim is running as root, before it changes uid for
19784 the delivery. This means that files that are inaccessible to the end user can
19785 be used to hold quota values that are looked up in the expansion. When delivery
19786 fails because this quota is exceeded, the handling of the error is as for
19787 system quota failures.
19788
19789 By default, Exim's quota checking mimics system quotas, and restricts the
19790 mailbox to the specified maximum size, though the value is not accurate to the
19791 last byte, owing to separator lines and additional headers that may get added
19792 during message delivery. When a mailbox is nearly full, large messages may get
19793 refused even though small ones are accepted, because the size of the current
19794 message is added to the quota when the check is made. This behaviour can be
19795 changed by setting &%quota_is_inclusive%& false. When this is done, the check
19796 for exceeding the quota does not include the current message. Thus, deliveries
19797 continue until the quota has been exceeded; thereafter, no further messages are
19798 delivered. See also &%quota_warn_threshold%&.
19799
19800
19801 .option quota_directory appendfile string&!! unset
19802 This option defines the directory to check for quota purposes when delivering
19803 into individual files. The default is the delivery directory, or, if a file
19804 called &_maildirfolder_& exists in a maildir directory, the parent of the
19805 delivery directory.
19806
19807
19808 .option quota_filecount appendfile string&!! 0
19809 This option applies when the &%directory%& option is set. It limits the total
19810 number of files in the directory (compare the inode limit in system quotas). It
19811 can only be used if &%quota%& is also set. The value is expanded; an expansion
19812 failure causes delivery to be deferred. A value of zero is interpreted as
19813 &"no quota"&.
19814
19815
19816 .option quota_is_inclusive appendfile boolean true
19817 See &%quota%& above.
19818
19819
19820 .option quota_size_regex appendfile string unset
19821 This option applies when one of the delivery modes that writes a separate file
19822 for each message is being used. When Exim wants to find the size of one of
19823 these files in order to test the quota, it first checks &%quota_size_regex%&.
19824 If this is set to a regular expression that matches the file name, and it
19825 captures one string, that string is interpreted as a representation of the
19826 file's size. The value of &%quota_size_regex%& is not expanded.
19827
19828 This feature is useful only when users have no shell access to their mailboxes
19829 &-- otherwise they could defeat the quota simply by renaming the files. This
19830 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
19831 the file length to the file name. For example:
19832 .code
19833 maildir_tag = ,S=$message_size
19834 quota_size_regex = ,S=(\d+)
19835 .endd
19836 An alternative to &$message_size$& is &$message_linecount$&, which contains the
19837 number of lines in the message.
19838
19839 The regular expression should not assume that the length is at the end of the
19840 file name (even though &%maildir_tag%& puts it there) because maildir MUAs
19841 sometimes add other information onto the ends of message file names.
19842
19843
19844
19845 .option quota_warn_message appendfile string&!! "see below"
19846 See below for the use of this option. If it is not set when
19847 &%quota_warn_threshold%& is set, it defaults to
19848 .code
19849 quota_warn_message = "\
19850 To: $local_part@$domain\n\
19851 Subject: Your mailbox\n\n\
19852 This message is automatically created \
19853 by mail delivery software.\n\n\
19854 The size of your mailbox has exceeded \
19855 a warning threshold that is\n\
19856 set by the system administrator.\n"
19857 .endd
19858
19859
19860 .option quota_warn_threshold appendfile string&!! 0
19861 .cindex "quota" "warning threshold"
19862 .cindex "mailbox" "size warning"
19863 .cindex "size" "of mailbox"
19864 This option is expanded in the same way as &%quota%& (see above). If the
19865 resulting value is greater than zero, and delivery of the message causes the
19866 size of the file or total space in the directory tree to cross the given
19867 threshold, a warning message is sent. If &%quota%& is also set, the threshold
19868 may be specified as a percentage of it by following the value with a percent
19869 sign. For example:
19870 .code
19871 quota = 10M
19872 quota_warn_threshold = 75%
19873 .endd
19874 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
19875 percent sign is ignored.
19876
19877 The warning message itself is specified by the &%quota_warn_message%& option,
19878 and it must start with a &'To:'& header line containing the recipient(s) of the
19879 warning message. These do not necessarily have to include the recipient(s) of
19880 the original message. A &'Subject:'& line should also normally be supplied. You
19881 can include any other header lines that you want. If you do not include a
19882 &'From:'& line, the default is:
19883 .code
19884 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
19885 .endd
19886 .oindex &%errors_reply_to%&
19887 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
19888 option.
19889
19890 The &%quota%& option does not have to be set in order to use this option; they
19891 are independent of one another except when the threshold is specified as a
19892 percentage.
19893
19894
19895 .option use_bsmtp appendfile boolean false
19896 .cindex "envelope sender"
19897 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
19898 format, with the envelope sender and recipient(s) included as SMTP commands. If
19899 you want to include a leading HELO command with such messages, you can do
19900 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
19901 for details of batch SMTP.
19902
19903
19904 .option use_crlf appendfile boolean false
19905 .cindex "carriage return"
19906 .cindex "linefeed"
19907 This option causes lines to be terminated with the two-character CRLF sequence
19908 (carriage return, linefeed) instead of just a linefeed character. In the case
19909 of batched SMTP, the byte sequence written to the file is then an exact image
19910 of what would be sent down a real SMTP connection.
19911
19912 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
19913 (which are used to supply the traditional &"From&~"& and blank line separators
19914 in Berkeley-style mailboxes) are written verbatim, so must contain their own
19915 carriage return characters if these are needed. In cases where these options
19916 have non-empty defaults, the values end with a single linefeed, so they must be
19917 changed to end with &`\r\n`& if &%use_crlf%& is set.
19918
19919
19920 .option use_fcntl_lock appendfile boolean "see below"
19921 This option controls the use of the &[fcntl()]& function to lock a file for
19922 exclusive use when a message is being appended. It is set by default unless
19923 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
19924 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
19925 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
19926
19927
19928 .option use_flock_lock appendfile boolean false
19929 This option is provided to support the use of &[flock()]& for file locking, for
19930 the few situations where it is needed. Most modern operating systems support
19931 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
19932 each other. Exim uses &[fcntl()]& locking by default.
19933
19934 This option is required only if you are using an operating system where
19935 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
19936 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
19937 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
19938
19939 .cindex "Solaris" "&[flock()]& support"
19940 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
19941 have it (and some, I think, provide a not quite right version built on top of
19942 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
19943 the ability to use it, and any attempt to do so will cause a configuration
19944 error.
19945
19946 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
19947 is just being mapped onto &[fcntl()]& by the OS).
19948
19949
19950 .option use_lockfile appendfile boolean "see below"
19951 If this option is turned off, Exim does not attempt to create a lock file when
19952 appending to a mailbox file. In this situation, the only locking is by
19953 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
19954 sure that every MUA that is ever going to look at your users' mailboxes uses
19955 &[fcntl()]& rather than a lock file, and even then only when you are not
19956 delivering over NFS from more than one host.
19957
19958 .cindex "NFS" "lock file"
19959 In order to append to an NFS file safely from more than one host, it is
19960 necessary to take out a lock &'before'& opening the file, and the lock file
19961 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
19962 file corruption.
19963
19964 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
19965 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
19966 except when &%mbx_format%& is set.
19967
19968
19969 .option use_mbx_lock appendfile boolean "see below"
19970 This option is available only if Exim has been compiled with SUPPORT_MBX
19971 set in &_Local/Makefile_&. Setting the option specifies that special MBX
19972 locking rules be used. It is set by default if &%mbx_format%& is set and none
19973 of the locking options are mentioned in the configuration. The locking rules
19974 are the same as are used by the &'c-client'& library that underlies Pine and
19975 the IMAP4 and POP daemons that come with it (see the discussion below). The
19976 rules allow for shared access to the mailbox. However, this kind of locking
19977 does not work when the mailbox is NFS mounted.
19978
19979 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
19980 &%use_flock_lock%& to control what kind of locking is used in implementing the
19981 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
19982 without &%use_fcntl_lock%& or &%use_flock_lock%&.
19983
19984
19985
19986
19987 .section "Operational details for appending" "SECTopappend"
19988 .cindex "appending to a file"
19989 .cindex "file" "appending"
19990 Before appending to a file, the following preparations are made:
19991
19992 .ilist
19993 If the name of the file is &_/dev/null_&, no action is taken, and a success
19994 return is given.
19995
19996 .next
19997 .cindex "directory creation"
19998 If any directories on the file's path are missing, Exim creates them if the
19999 &%create_directory%& option is set. A created directory's mode is given by the
20000 &%directory_mode%& option.
20001
20002 .next
20003 If &%file_format%& is set, the format of an existing file is checked. If this
20004 indicates that a different transport should be used, control is passed to that
20005 transport.
20006
20007 .next
20008 .cindex "file" "locking"
20009 .cindex "locking files"
20010 .cindex "NFS" "lock file"
20011 If &%use_lockfile%& is set, a lock file is built in a way that will work
20012 reliably over NFS, as follows:
20013
20014 .olist
20015 Create a &"hitching post"& file whose name is that of the lock file with the
20016 current time, primary host name, and process id added, by opening for writing
20017 as a new file. If this fails with an access error, delivery is deferred.
20018 .next
20019 Close the hitching post file, and hard link it to the lock file name.
20020 .next
20021 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
20022 Unlink the hitching post name.
20023 .next
20024 Otherwise, use &[stat()]& to get information about the hitching post file, and
20025 then unlink hitching post name. If the number of links is exactly two, creation
20026 of the lock file succeeded but something (for example, an NFS server crash and
20027 restart) caused this fact not to be communicated to the &[link()]& call.
20028 .next
20029 If creation of the lock file failed, wait for &%lock_interval%& and try again,
20030 up to &%lock_retries%& times. However, since any program that writes to a
20031 mailbox should complete its task very quickly, it is reasonable to time out old
20032 lock files that are normally the result of user agent and system crashes. If an
20033 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
20034 it before trying again.
20035 .endlist olist
20036
20037 .next
20038 A call is made to &[lstat()]& to discover whether the main file exists, and if
20039 so, what its characteristics are. If &[lstat()]& fails for any reason other
20040 than non-existence, delivery is deferred.
20041
20042 .next
20043 .cindex "symbolic link" "to mailbox"
20044 .cindex "mailbox" "symbolic link"
20045 If the file does exist and is a symbolic link, delivery is deferred, unless the
20046 &%allow_symlink%& option is set, in which case the ownership of the link is
20047 checked, and then &[stat()]& is called to find out about the real file, which
20048 is then subjected to the checks below. The check on the top-level link
20049 ownership prevents one user creating a link for another's mailbox in a sticky
20050 directory, though allowing symbolic links in this case is definitely not a good
20051 idea. If there is a chain of symbolic links, the intermediate ones are not
20052 checked.
20053
20054 .next
20055 If the file already exists but is not a regular file, or if the file's owner
20056 and group (if the group is being checked &-- see &%check_group%& above) are
20057 different from the user and group under which the delivery is running,
20058 delivery is deferred.
20059
20060 .next
20061 If the file's permissions are more generous than specified, they are reduced.
20062 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
20063 is set false, in which case the delivery is tried using the existing
20064 permissions.
20065
20066 .next
20067 The file's inode number is saved, and the file is then opened for appending.
20068 If this fails because the file has vanished, &(appendfile)& behaves as if it
20069 hadn't existed (see below). For any other failures, delivery is deferred.
20070
20071 .next
20072 If the file is opened successfully, check that the inode number hasn't
20073 changed, that it is still a regular file, and that the owner and permissions
20074 have not changed. If anything is wrong, defer delivery and freeze the message.
20075
20076 .next
20077 If the file did not exist originally, defer delivery if the &%file_must_exist%&
20078 option is set. Otherwise, check that the file is being created in a permitted
20079 directory if the &%create_file%& option is set (deferring on failure), and then
20080 open for writing as a new file, with the O_EXCL and O_CREAT options,
20081 except when dealing with a symbolic link (the &%allow_symlink%& option must be
20082 set). In this case, which can happen if the link points to a non-existent file,
20083 the file is opened for writing using O_CREAT but not O_EXCL, because
20084 that prevents link following.
20085
20086 .next
20087 .cindex "loop" "while file testing"
20088 If opening fails because the file exists, obey the tests given above for
20089 existing files. However, to avoid looping in a situation where the file is
20090 being continuously created and destroyed, the exists/not-exists loop is broken
20091 after 10 repetitions, and the message is then frozen.
20092
20093 .next
20094 If opening fails with any other error, defer delivery.
20095
20096 .next
20097 .cindex "file" "locking"
20098 .cindex "locking files"
20099 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
20100 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
20101 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
20102 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
20103 file, and an exclusive lock on the file whose name is
20104 .code
20105 /tmp/.<device-number>.<inode-number>
20106 .endd
20107 using the device and inode numbers of the open mailbox file, in accordance with
20108 the MBX locking rules. This file is created with a mode that is specified by
20109 the &%lockfile_mode%& option.
20110
20111 If Exim fails to lock the file, there are two possible courses of action,
20112 depending on the value of the locking timeout. This is obtained from
20113 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
20114
20115 If the timeout value is zero, the file is closed, Exim waits for
20116 &%lock_interval%&, and then goes back and re-opens the file as above and tries
20117 to lock it again. This happens up to &%lock_retries%& times, after which the
20118 delivery is deferred.
20119
20120 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
20121 &[flock()]& are used (with the given timeout), so there has already been some
20122 waiting involved by the time locking fails. Nevertheless, Exim does not give up
20123 immediately. It retries up to
20124 .code
20125 (lock_retries * lock_interval) / <timeout>
20126 .endd
20127 times (rounded up).
20128 .endlist
20129
20130 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
20131 and/or &[flock()]& locks) and then deletes the lock file if one was created.
20132
20133
20134 .section "Operational details for delivery to a new file" "SECTopdir"
20135 .cindex "delivery" "to single file"
20136 .cindex "&""From""& line"
20137 When the &%directory%& option is set instead of &%file%&, each message is
20138 delivered into a newly-created file or set of files. When &(appendfile)& is
20139 activated directly from a &(redirect)& router, neither &%file%& nor
20140 &%directory%& is normally set, because the path for delivery is supplied by the
20141 router. (See for example, the &(address_file)& transport in the default
20142 configuration.) In this case, delivery is to a new file if either the path name
20143 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
20144
20145 No locking is required while writing the message to a new file, so the various
20146 locking options of the transport are ignored. The &"From"& line that by default
20147 separates messages in a single file is not normally needed, nor is the escaping
20148 of message lines that start with &"From"&, and there is no need to ensure a
20149 newline at the end of each message. Consequently, the default values for
20150 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
20151 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
20152
20153 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
20154 the files in the delivery directory by default. However, you can specify a
20155 different directory by setting &%quota_directory%&. Also, for maildir
20156 deliveries (see below) the &_maildirfolder_& convention is honoured.
20157
20158
20159 .cindex "maildir format"
20160 .cindex "mailstore format"
20161 There are three different ways in which delivery to individual files can be
20162 done, controlled by the settings of the &%maildir_format%& and
20163 &%mailstore_format%& options. Note that code to support maildir or mailstore
20164 formats is not included in the binary unless SUPPORT_MAILDIR or
20165 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
20166
20167 .cindex "directory creation"
20168 In all three cases an attempt is made to create the directory and any necessary
20169 sub-directories if they do not exist, provided that the &%create_directory%&
20170 option is set (the default). The location of a created directory can be
20171 constrained by setting &%create_file%&. A created directory's mode is given by
20172 the &%directory_mode%& option. If creation fails, or if the
20173 &%create_directory%& option is not set when creation is required, delivery is
20174 deferred.
20175
20176
20177
20178 .section "Maildir delivery" "SECTmaildirdelivery"
20179 .cindex "maildir format" "description of"
20180 If the &%maildir_format%& option is true, Exim delivers each message by writing
20181 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
20182 directory that is defined by the &%directory%& option (the &"delivery
20183 directory"&). If the delivery is successful, the file is renamed into the
20184 &_new_& subdirectory.
20185
20186 In the file name, <&'stime'&> is the current time of day in seconds, and
20187 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
20188 Exim checks that the time-of-day clock has moved on by at least one microsecond
20189 before terminating the delivery process. This guarantees uniqueness for the
20190 file name. However, as a precaution, Exim calls &[stat()]& for the file before
20191 opening it. If any response other than ENOENT (does not exist) is given,
20192 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
20193
20194 Before Exim carries out a maildir delivery, it ensures that subdirectories
20195 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
20196 do not exist, Exim tries to create them and any superior directories in their
20197 path, subject to the &%create_directory%& and &%create_file%& options. If the
20198 &%maildirfolder_create_regex%& option is set, and the regular expression it
20199 contains matches the delivery directory, Exim also ensures that a file called
20200 &_maildirfolder_& exists in the delivery directory. If a missing directory or
20201 &_maildirfolder_& file cannot be created, delivery is deferred.
20202
20203 These features make it possible to use Exim to create all the necessary files
20204 and directories in a maildir mailbox, including subdirectories for maildir++
20205 folders. Consider this example:
20206 .code
20207 maildir_format = true
20208 directory = /var/mail/$local_part\
20209 ${if eq{$local_part_suffix}{}{}\
20210 {/.${substr_1:$local_part_suffix}}}
20211 maildirfolder_create_regex = /\.[^/]+$
20212 .endd
20213 If &$local_part_suffix$& is empty (there was no suffix for the local part),
20214 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
20215 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
20216 not match this name, so Exim will not look for or create the file
20217 &_/var/mail/pimbo/maildirfolder_&, though it will create
20218 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
20219
20220 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
20221 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
20222 does match &%maildirfolder_create_regex%&. In this case, Exim will create
20223 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
20224 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
20225
20226 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
20227 not inadvertently match the toplevel maildir directory, because a
20228 &_maildirfolder_& file at top level would completely break quota calculations.
20229
20230 .cindex "quota" "in maildir delivery"
20231 .cindex "maildir++"
20232 If Exim is required to check a &%quota%& setting before a maildir delivery, and
20233 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
20234 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
20235 Exim assumes the directory is a maildir++ folder directory, which is one level
20236 down from the user's top level mailbox directory. This causes it to start at
20237 the parent directory instead of the current directory when calculating the
20238 amount of space used.
20239
20240 One problem with delivering into a multi-file mailbox is that it is
20241 computationally expensive to compute the size of the mailbox for quota
20242 checking. Various approaches have been taken to reduce the amount of work
20243 needed. The next two sections describe two of them. A third alternative is to
20244 use some external process for maintaining the size data, and use the expansion
20245 of the &%mailbox_size%& option as a way of importing it into Exim.
20246
20247
20248
20249
20250 .section "Using tags to record message sizes" "SECID135"
20251 If &%maildir_tag%& is set, the string is expanded for each delivery.
20252 When the maildir file is renamed into the &_new_& sub-directory, the
20253 tag is added to its name. However, if adding the tag takes the length of the
20254 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
20255 the tag is dropped and the maildir file is created with no tag.
20256
20257 .vindex "&$message_size$&"
20258 Tags can be used to encode the size of files in their names; see
20259 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
20260 happens after the message has been written. The value of the &$message_size$&
20261 variable is set to the number of bytes actually written. If the expansion is
20262 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
20263 be deferred. The expanded tag may contain any printing characters except &"/"&.
20264 Non-printing characters in the string are ignored; if the resulting string is
20265 empty, it is ignored. If it starts with an alphanumeric character, a leading
20266 colon is inserted.
20267
20268
20269
20270 .section "Using a maildirsize file" "SECID136"
20271 .cindex "quota" "in maildir delivery"
20272 .cindex "maildir format" "&_maildirsize_& file"
20273 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
20274 storing quota and message size information in a file called &_maildirsize_&
20275 within the toplevel maildir directory. If this file does not exist, Exim
20276 creates it, setting the quota from the &%quota%& option of the transport. If
20277 the maildir directory itself does not exist, it is created before any attempt
20278 to write a &_maildirsize_& file.
20279
20280 The &_maildirsize_& file is used to hold information about the sizes of
20281 messages in the maildir, thus speeding up quota calculations. The quota value
20282 in the file is just a cache; if the quota is changed in the transport, the new
20283 value overrides the cached value when the next message is delivered. The cache
20284 is maintained for the benefit of other programs that access the maildir and
20285 need to know the quota.
20286
20287 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
20288 file is maintained (with a zero quota setting), but no quota is imposed.
20289
20290 A regular expression is available for controlling which directories in the
20291 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
20292 See the description of the &%maildir_quota_directory_regex%& option above for
20293 details.
20294
20295
20296 .section "Mailstore delivery" "SECID137"
20297 .cindex "mailstore format" "description of"
20298 If the &%mailstore_format%& option is true, each message is written as two
20299 files in the given directory. A unique base name is constructed from the
20300 message id and the current delivery process, and the files that are written use
20301 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
20302 contains the message's envelope, and the &_.msg_& file contains the message
20303 itself. The base name is placed in the variable &$mailstore_basename$&.
20304
20305 During delivery, the envelope is first written to a file with the suffix
20306 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
20307 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
20308 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
20309 file before accessing either of them. An alternative approach is to wait for
20310 the absence of a &_.tmp_& file.
20311
20312 The envelope file starts with any text defined by the &%mailstore_prefix%&
20313 option, expanded and terminated by a newline if there isn't one. Then follows
20314 the sender address on one line, then all the recipient addresses, one per line.
20315 There can be more than one recipient only if the &%batch_max%& option is set
20316 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
20317 appended to the file, followed by a newline if it does not end with one.
20318
20319 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
20320 failure, it is ignored. Other expansion errors are treated as serious
20321 configuration errors, and delivery is deferred. The variable
20322 &$mailstore_basename$& is available for use during these expansions.
20323
20324
20325 .section "Non-special new file delivery" "SECID138"
20326 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
20327 file is created directly in the named directory. For example, when delivering
20328 messages into files in batched SMTP format for later delivery to some host (see
20329 section &<<SECTbatchSMTP>>&), a setting such as
20330 .code
20331 directory = /var/bsmtp/$host
20332 .endd
20333 might be used. A message is written to a file with a temporary name, which is
20334 then renamed when the delivery is complete. The final name is obtained by
20335 expanding the contents of the &%directory_file%& option.
20336 .ecindex IIDapptra1
20337 .ecindex IIDapptra2
20338
20339
20340
20341
20342
20343
20344 . ////////////////////////////////////////////////////////////////////////////
20345 . ////////////////////////////////////////////////////////////////////////////
20346
20347 .chapter "The autoreply transport" "CHID8"
20348 .scindex IIDauttra1 "transports" "&(autoreply)&"
20349 .scindex IIDauttra2 "&(autoreply)& transport"
20350 The &(autoreply)& transport is not a true transport in that it does not cause
20351 the message to be transmitted. Instead, it generates a new mail message as an
20352 automatic reply to the incoming message. &'References:'& and
20353 &'Auto-Submitted:'& header lines are included. These are constructed according
20354 to the rules in RFCs 2822 and 3834, respectively.
20355
20356 If the router that passes the message to this transport does not have the
20357 &%unseen%& option set, the original message (for the current recipient) is not
20358 delivered anywhere. However, when the &%unseen%& option is set on the router
20359 that passes the message to this transport, routing of the address continues, so
20360 another router can set up a normal message delivery.
20361
20362
20363 The &(autoreply)& transport is usually run as the result of mail filtering, a
20364 &"vacation"& message being the standard example. However, it can also be run
20365 directly from a router like any other transport. To reduce the possibility of
20366 message cascades, messages created by the &(autoreply)& transport always have
20367 empty envelope sender addresses, like bounce messages.
20368
20369 The parameters of the message to be sent can be specified in the configuration
20370 by options described below. However, these are used only when the address
20371 passed to the transport does not contain its own reply information. When the
20372 transport is run as a consequence of a
20373 &%mail%&
20374 or &%vacation%& command in a filter file, the parameters of the message are
20375 supplied by the filter, and passed with the address. The transport's options
20376 that define the message are then ignored (so they are not usually set in this
20377 case). The message is specified entirely by the filter or by the transport; it
20378 is never built from a mixture of options. However, the &%file_optional%&,
20379 &%mode%&, and &%return_message%& options apply in all cases.
20380
20381 &(Autoreply)& is implemented as a local transport. When used as a result of a
20382 command in a user's filter file, &(autoreply)& normally runs under the uid and
20383 gid of the user, and with appropriate current and home directories (see chapter
20384 &<<CHAPenvironment>>&).
20385
20386 There is a subtle difference between routing a message to a &(pipe)& transport
20387 that generates some text to be returned to the sender, and routing it to an
20388 &(autoreply)& transport. This difference is noticeable only if more than one
20389 address from the same message is so handled. In the case of a pipe, the
20390 separate outputs from the different addresses are gathered up and returned to
20391 the sender in a single message, whereas if &(autoreply)& is used, a separate
20392 message is generated for each address that is passed to it.
20393
20394 Non-printing characters are not permitted in the header lines generated for the
20395 message that &(autoreply)& creates, with the exception of newlines that are
20396 immediately followed by white space. If any non-printing characters are found,
20397 the transport defers.
20398 Whether characters with the top bit set count as printing characters or not is
20399 controlled by the &%print_topbitchars%& global option.
20400
20401 If any of the generic options for manipulating headers (for example,
20402 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
20403 of the original message that is included in the generated message when
20404 &%return_message%& is set. They do not apply to the generated message itself.
20405
20406 .vindex "&$sender_address$&"
20407 If the &(autoreply)& transport receives return code 2 from Exim when it submits
20408 the message, indicating that there were no recipients, it does not treat this
20409 as an error. This means that autoreplies sent to &$sender_address$& when this
20410 is empty (because the incoming message is a bounce message) do not cause
20411 problems. They are just discarded.
20412
20413
20414
20415 .section "Private options for autoreply" "SECID139"
20416 .cindex "options" "&(autoreply)& transport"
20417
20418 .option bcc autoreply string&!! unset
20419 This specifies the addresses that are to receive &"blind carbon copies"& of the
20420 message when the message is specified by the transport.
20421
20422
20423 .option cc autoreply string&!! unset
20424 This specifies recipients of the message and the contents of the &'Cc:'& header
20425 when the message is specified by the transport.
20426
20427
20428 .option file autoreply string&!! unset
20429 The contents of the file are sent as the body of the message when the message
20430 is specified by the transport. If both &%file%& and &%text%& are set, the text
20431 string comes first.
20432
20433
20434 .option file_expand autoreply boolean false
20435 If this is set, the contents of the file named by the &%file%& option are
20436 subjected to string expansion as they are added to the message.
20437
20438
20439 .option file_optional autoreply boolean false
20440 If this option is true, no error is generated if the file named by the &%file%&
20441 option or passed with the address does not exist or cannot be read.
20442
20443
20444 .option from autoreply string&!! unset
20445 This specifies the contents of the &'From:'& header when the message is
20446 specified by the transport.
20447
20448
20449 .option headers autoreply string&!! unset
20450 This specifies additional RFC 2822 headers that are to be added to the message
20451 when the message is specified by the transport. Several can be given by using
20452 &"\n"& to separate them. There is no check on the format.
20453
20454
20455 .option log autoreply string&!! unset
20456 This option names a file in which a record of every message sent is logged when
20457 the message is specified by the transport.
20458
20459
20460 .option mode autoreply "octal integer" 0600
20461 If either the log file or the &"once"& file has to be created, this mode is
20462 used.
20463
20464
20465 .option never_mail autoreply "address list&!!" unset
20466 If any run of the transport creates a message with a recipient that matches any
20467 item in the list, that recipient is quietly discarded. If all recipients are
20468 discarded, no message is created. This applies both when the recipients are
20469 generated by a filter and when they are specified in the transport.
20470
20471
20472
20473 .option once autoreply string&!! unset
20474 This option names a file or DBM database in which a record of each &'To:'&
20475 recipient is kept when the message is specified by the transport. &*Note*&:
20476 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
20477
20478 If &%once%& is unset, or is set to an empty string, the message is always sent.
20479 By default, if &%once%& is set to a non-empty file name, the message
20480 is not sent if a potential recipient is already listed in the database.
20481 However, if the &%once_repeat%& option specifies a time greater than zero, the
20482 message is sent if that much time has elapsed since a message was last sent to
20483 this recipient. A setting of zero time for &%once_repeat%& (the default)
20484 prevents a message from being sent a second time &-- in this case, zero means
20485 infinity.
20486
20487 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
20488 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
20489 greater than zero, it changes the way Exim implements the &%once%& option.
20490 Instead of using a DBM file to record every recipient it sends to, it uses a
20491 regular file, whose size will never get larger than the given value.
20492
20493 In the file, Exim keeps a linear list of recipient addresses and the times at
20494 which they were sent messages. If the file is full when a new address needs to
20495 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
20496 means that a given recipient may receive multiple messages, but at
20497 unpredictable intervals that depend on the rate of turnover of addresses in the
20498 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
20499
20500
20501 .option once_file_size autoreply integer 0
20502 See &%once%& above.
20503
20504
20505 .option once_repeat autoreply time&!! 0s
20506 See &%once%& above.
20507 After expansion, the value of this option must be a valid time value.
20508
20509
20510 .option reply_to autoreply string&!! unset
20511 This specifies the contents of the &'Reply-To:'& header when the message is
20512 specified by the transport.
20513
20514
20515 .option return_message autoreply boolean false
20516 If this is set, a copy of the original message is returned with the new
20517 message, subject to the maximum size set in the &%return_size_limit%& global
20518 configuration option.
20519
20520
20521 .option subject autoreply string&!! unset
20522 This specifies the contents of the &'Subject:'& header when the message is
20523 specified by the transport. It is tempting to quote the original subject in
20524 automatic responses. For example:
20525 .code
20526 subject = Re: $h_subject:
20527 .endd
20528 There is a danger in doing this, however. It may allow a third party to
20529 subscribe your users to an opt-in mailing list, provided that the list accepts
20530 bounce messages as subscription confirmations. Well-managed lists require a
20531 non-bounce message to confirm a subscription, so the danger is relatively
20532 small.
20533
20534
20535
20536 .option text autoreply string&!! unset
20537 This specifies a single string to be used as the body of the message when the
20538 message is specified by the transport. If both &%text%& and &%file%& are set,
20539 the text comes first.
20540
20541
20542 .option to autoreply string&!! unset
20543 This specifies recipients of the message and the contents of the &'To:'& header
20544 when the message is specified by the transport.
20545 .ecindex IIDauttra1
20546 .ecindex IIDauttra2
20547
20548
20549
20550
20551 . ////////////////////////////////////////////////////////////////////////////
20552 . ////////////////////////////////////////////////////////////////////////////
20553
20554 .chapter "The lmtp transport" "CHAPLMTP"
20555 .cindex "transports" "&(lmtp)&"
20556 .cindex "&(lmtp)& transport"
20557 .cindex "LMTP" "over a pipe"
20558 .cindex "LMTP" "over a socket"
20559 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
20560 specified command
20561 or by interacting with a Unix domain socket.
20562 This transport is something of a cross between the &(pipe)& and &(smtp)&
20563 transports. Exim also has support for using LMTP over TCP/IP; this is
20564 implemented as an option for the &(smtp)& transport. Because LMTP is expected
20565 to be of minority interest, the default build-time configure in &_src/EDITME_&
20566 has it commented out. You need to ensure that
20567 .code
20568 TRANSPORT_LMTP=yes
20569 .endd
20570 .cindex "options" "&(lmtp)& transport"
20571 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
20572 included in the Exim binary. The private options of the &(lmtp)& transport are
20573 as follows:
20574
20575 .option batch_id lmtp string&!! unset
20576 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
20577
20578
20579 .option batch_max lmtp integer 1
20580 This limits the number of addresses that can be handled in a single delivery.
20581 Most LMTP servers can handle several addresses at once, so it is normally a
20582 good idea to increase this value. See the description of local delivery
20583 batching in chapter &<<CHAPbatching>>&.
20584
20585
20586 .option command lmtp string&!! unset
20587 This option must be set if &%socket%& is not set. The string is a command which
20588 is run in a separate process. It is split up into a command name and list of
20589 arguments, each of which is separately expanded (so expansion cannot change the
20590 number of arguments). The command is run directly, not via a shell. The message
20591 is passed to the new process using the standard input and output to operate the
20592 LMTP protocol.
20593
20594 .option ignore_quota lmtp boolean false
20595 .cindex "LMTP" "ignoring quota errors"
20596 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
20597 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
20598 in its response to the LHLO command.
20599
20600 .option socket lmtp string&!! unset
20601 This option must be set if &%command%& is not set. The result of expansion must
20602 be the name of a Unix domain socket. The transport connects to the socket and
20603 delivers the message to it using the LMTP protocol.
20604
20605
20606 .option timeout lmtp time 5m
20607 The transport is aborted if the created process or Unix domain socket does not
20608 respond to LMTP commands or message input within this timeout. Delivery
20609 is deferred, and will be tried again later. Here is an example of a typical
20610 LMTP transport:
20611 .code
20612 lmtp:
20613 driver = lmtp
20614 command = /some/local/lmtp/delivery/program
20615 batch_max = 20
20616 user = exim
20617 .endd
20618 This delivers up to 20 addresses at a time, in a mixture of domains if
20619 necessary, running as the user &'exim'&.
20620
20621
20622
20623 . ////////////////////////////////////////////////////////////////////////////
20624 . ////////////////////////////////////////////////////////////////////////////
20625
20626 .chapter "The pipe transport" "CHAPpipetransport"
20627 .scindex IIDpiptra1 "transports" "&(pipe)&"
20628 .scindex IIDpiptra2 "&(pipe)& transport"
20629 The &(pipe)& transport is used to deliver messages via a pipe to a command
20630 running in another process. One example is the use of &(pipe)& as a
20631 pseudo-remote transport for passing messages to some other delivery mechanism
20632 (such as UUCP). Another is the use by individual users to automatically process
20633 their incoming messages. The &(pipe)& transport can be used in one of the
20634 following ways:
20635
20636 .ilist
20637 .vindex "&$local_part$&"
20638 A router routes one address to a transport in the normal way, and the
20639 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
20640 contains the local part of the address (as usual), and the command that is run
20641 is specified by the &%command%& option on the transport.
20642 .next
20643 .vindex "&$pipe_addresses$&"
20644 If the &%batch_max%& option is set greater than 1 (the default is 1), the
20645 transport can handle more than one address in a single run. In this case, when
20646 more than one address is routed to the transport, &$local_part$& is not set
20647 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
20648 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
20649 that are routed to the transport.
20650 .next
20651 .vindex "&$address_pipe$&"
20652 A router redirects an address directly to a pipe command (for example, from an
20653 alias or forward file). In this case, &$address_pipe$& contains the text of the
20654 pipe command, and the &%command%& option on the transport is ignored. If only
20655 one address is being transported (&%batch_max%& is not greater than one, or
20656 only one address was redirected to this pipe command), &$local_part$& contains
20657 the local part that was redirected.
20658 .endlist
20659
20660
20661 The &(pipe)& transport is a non-interactive delivery method. Exim can also
20662 deliver messages over pipes using the LMTP interactive protocol. This is
20663 implemented by the &(lmtp)& transport.
20664
20665 In the case when &(pipe)& is run as a consequence of an entry in a local user's
20666 &_.forward_& file, the command runs under the uid and gid of that user. In
20667 other cases, the uid and gid have to be specified explicitly, either on the
20668 transport or on the router that handles the address. Current and &"home"&
20669 directories are also controllable. See chapter &<<CHAPenvironment>>& for
20670 details of the local delivery environment and chapter &<<CHAPbatching>>&
20671 for a discussion of local delivery batching.
20672
20673
20674 .section "Concurrent delivery" "SECID140"
20675 If two messages arrive at almost the same time, and both are routed to a pipe
20676 delivery, the two pipe transports may be run concurrently. You must ensure that
20677 any pipe commands you set up are robust against this happening. If the commands
20678 write to a file, the &%exim_lock%& utility might be of use.
20679
20680
20681
20682
20683 .section "Returned status and data" "SECID141"
20684 .cindex "&(pipe)& transport" "returned data"
20685 If the command exits with a non-zero return code, the delivery is deemed to
20686 have failed, unless either the &%ignore_status%& option is set (in which case
20687 the return code is treated as zero), or the return code is one of those listed
20688 in the &%temp_errors%& option, which are interpreted as meaning &"try again
20689 later"&. In this case, delivery is deferred. Details of a permanent failure are
20690 logged, but are not included in the bounce message, which merely contains
20691 &"local delivery failed"&.
20692
20693 If the return code is greater than 128 and the command being run is a shell
20694 script, it normally means that the script was terminated by a signal whose
20695 value is the return code minus 128.
20696
20697 If Exim is unable to run the command (that is, if &[execve()]& fails), the
20698 return code is set to 127. This is the value that a shell returns if it is
20699 asked to run a non-existent command. The wording for the log line suggests that
20700 a non-existent command may be the problem.
20701
20702 The &%return_output%& option can affect the result of a pipe delivery. If it is
20703 set and the command produces any output on its standard output or standard
20704 error streams, the command is considered to have failed, even if it gave a zero
20705 return code or if &%ignore_status%& is set. The output from the command is
20706 included as part of the bounce message. The &%return_fail_output%& option is
20707 similar, except that output is returned only when the command exits with a
20708 failure return code, that is, a value other than zero or a code that matches
20709 &%temp_errors%&.
20710
20711
20712
20713 .section "How the command is run" "SECThowcommandrun"
20714 .cindex "&(pipe)& transport" "path for command"
20715 The command line is (by default) broken down into a command name and arguments
20716 by the &(pipe)& transport itself. The &%allow_commands%& and
20717 &%restrict_to_path%& options can be used to restrict the commands that may be
20718 run.
20719
20720 .cindex "quoting" "in pipe command"
20721 Unquoted arguments are delimited by white space. If an argument appears in
20722 double quotes, backslash is interpreted as an escape character in the usual
20723 way. If an argument appears in single quotes, no escaping is done.
20724
20725 String expansion is applied to the command line except when it comes from a
20726 traditional &_.forward_& file (commands from a filter file are expanded). The
20727 expansion is applied to each argument in turn rather than to the whole line.
20728 For this reason, any string expansion item that contains white space must be
20729 quoted so as to be contained within a single argument. A setting such as
20730 .code
20731 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
20732 .endd
20733 will not work, because the expansion item gets split between several
20734 arguments. You have to write
20735 .code
20736 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
20737 .endd
20738 to ensure that it is all in one argument. The expansion is done in this way,
20739 argument by argument, so that the number of arguments cannot be changed as a
20740 result of expansion, and quotes or backslashes in inserted variables do not
20741 interact with external quoting. However, this leads to problems if you want to
20742 generate multiple arguments (or the command name plus arguments) from a single
20743 expansion. In this situation, the simplest solution is to use a shell. For
20744 example:
20745 .code
20746 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
20747 .endd
20748
20749 .cindex "transport" "filter"
20750 .cindex "filter" "transport filter"
20751 .vindex "&$pipe_addresses$&"
20752 Special handling takes place when an argument consists of precisely the text
20753 &`$pipe_addresses`&. This is not a general expansion variable; the only
20754 place this string is recognized is when it appears as an argument for a pipe or
20755 transport filter command. It causes each address that is being handled to be
20756 inserted in the argument list at that point &'as a separate argument'&. This
20757 avoids any problems with spaces or shell metacharacters, and is of use when a
20758 &(pipe)& transport is handling groups of addresses in a batch.
20759
20760 After splitting up into arguments and expansion, the resulting command is run
20761 in a subprocess directly from the transport, &'not'& under a shell. The
20762 message that is being delivered is supplied on the standard input, and the
20763 standard output and standard error are both connected to a single pipe that is
20764 read by Exim. The &%max_output%& option controls how much output the command
20765 may produce, and the &%return_output%& and &%return_fail_output%& options
20766 control what is done with it.
20767
20768 Not running the command under a shell (by default) lessens the security risks
20769 in cases when a command from a user's filter file is built out of data that was
20770 taken from an incoming message. If a shell is required, it can of course be
20771 explicitly specified as the command to be run. However, there are circumstances
20772 where existing commands (for example, in &_.forward_& files) expect to be run
20773 under a shell and cannot easily be modified. To allow for these cases, there is
20774 an option called &%use_shell%&, which changes the way the &(pipe)& transport
20775 works. Instead of breaking up the command line as just described, it expands it
20776 as a single string and passes the result to &_/bin/sh_&. The
20777 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
20778 with &%use_shell%&, and the whole mechanism is inherently less secure.
20779
20780
20781
20782 .section "Environment variables" "SECTpipeenv"
20783 .cindex "&(pipe)& transport" "environment for command"
20784 .cindex "environment for pipe transport"
20785 The environment variables listed below are set up when the command is invoked.
20786 This list is a compromise for maximum compatibility with other MTAs. Note that
20787 the &%environment%& option can be used to add additional variables to this
20788 environment.
20789 .display
20790 &`DOMAIN `& the domain of the address
20791 &`HOME `& the home directory, if set
20792 &`HOST `& the host name when called from a router (see below)
20793 &`LOCAL_PART `& see below
20794 &`LOCAL_PART_PREFIX `& see below
20795 &`LOCAL_PART_SUFFIX `& see below
20796 &`LOGNAME `& see below
20797 &`MESSAGE_ID `& Exim's local ID for the message
20798 &`PATH `& as specified by the &%path%& option below
20799 &`QUALIFY_DOMAIN `& the sender qualification domain
20800 &`RECIPIENT `& the complete recipient address
20801 &`SENDER `& the sender of the message (empty if a bounce)
20802 &`SHELL `& &`/bin/sh`&
20803 &`TZ `& the value of the &%timezone%& option, if set
20804 &`USER `& see below
20805 .endd
20806 When a &(pipe)& transport is called directly from (for example) an &(accept)&
20807 router, LOCAL_PART is set to the local part of the address. When it is
20808 called as a result of a forward or alias expansion, LOCAL_PART is set to
20809 the local part of the address that was expanded. In both cases, any affixes are
20810 removed from the local part, and made available in LOCAL_PART_PREFIX and
20811 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
20812 same value as LOCAL_PART for compatibility with other MTAs.
20813
20814 .cindex "HOST"
20815 HOST is set only when a &(pipe)& transport is called from a router that
20816 associates hosts with an address, typically when using &(pipe)& as a
20817 pseudo-remote transport. HOST is set to the first host name specified by
20818 the router.
20819
20820 .cindex "HOME"
20821 If the transport's generic &%home_directory%& option is set, its value is used
20822 for the HOME environment variable. Otherwise, a home directory may be set
20823 by the router's &%transport_home_directory%& option, which defaults to the
20824 user's home directory if &%check_local_user%& is set.
20825
20826
20827 .section "Private options for pipe" "SECID142"
20828 .cindex "options" "&(pipe)& transport"
20829
20830
20831
20832 .option allow_commands pipe "string list&!!" unset
20833 .cindex "&(pipe)& transport" "permitted commands"
20834 The string is expanded, and is then interpreted as a colon-separated list of
20835 permitted commands. If &%restrict_to_path%& is not set, the only commands
20836 permitted are those in the &%allow_commands%& list. They need not be absolute
20837 paths; the &%path%& option is still used for relative paths. If
20838 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
20839 in the &%allow_commands%& list, or a name without any slashes that is found on
20840 the path. In other words, if neither &%allow_commands%& nor
20841 &%restrict_to_path%& is set, there is no restriction on the command, but
20842 otherwise only commands that are permitted by one or the other are allowed. For
20843 example, if
20844 .code
20845 allow_commands = /usr/bin/vacation
20846 .endd
20847 and &%restrict_to_path%& is not set, the only permitted command is
20848 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
20849 &%use_shell%& is set.
20850
20851
20852 .option batch_id pipe string&!! unset
20853 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
20854
20855
20856 .option batch_max pipe integer 1
20857 This limits the number of addresses that can be handled in a single delivery.
20858 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
20859
20860
20861 .option check_string pipe string unset
20862 As &(pipe)& writes the message, the start of each line is tested for matching
20863 &%check_string%&, and if it does, the initial matching characters are replaced
20864 by the contents of &%escape_string%&, provided both are set. The value of
20865 &%check_string%& is a literal string, not a regular expression, and the case of
20866 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
20867 of &%check_string%& and &%escape_string%& are forced to values that implement
20868 the SMTP escaping protocol. Any settings made in the configuration file are
20869 ignored.
20870
20871
20872 .option command pipe string&!! unset
20873 This option need not be set when &(pipe)& is being used to deliver to pipes
20874 obtained directly from address redirections. In other cases, the option must be
20875 set, to provide a command to be run. It need not yield an absolute path (see
20876 the &%path%& option below). The command is split up into separate arguments by
20877 Exim, and each argument is separately expanded, as described in section
20878 &<<SECThowcommandrun>>& above.
20879
20880
20881 .option environment pipe string&!! unset
20882 .cindex "&(pipe)& transport" "environment for command"
20883 .cindex "environment for &(pipe)& transport"
20884 This option is used to add additional variables to the environment in which the
20885 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
20886 a string which is expanded, and then interpreted as a colon-separated list of
20887 environment settings of the form <&'name'&>=<&'value'&>.
20888
20889
20890 .option escape_string pipe string unset
20891 See &%check_string%& above.
20892
20893
20894 .option freeze_exec_fail pipe boolean false
20895 .cindex "exec failure"
20896 .cindex "failure of exec"
20897 .cindex "&(pipe)& transport" "failure of exec"
20898 Failure to exec the command in a pipe transport is by default treated like
20899 any other failure while running the command. However, if &%freeze_exec_fail%&
20900 is set, failure to exec is treated specially, and causes the message to be
20901 frozen, whatever the setting of &%ignore_status%&.
20902
20903
20904 .option ignore_status pipe boolean false
20905 If this option is true, the status returned by the subprocess that is set up to
20906 run the command is ignored, and Exim behaves as if zero had been returned.
20907 Otherwise, a non-zero status or termination by signal causes an error return
20908 from the transport unless the status value is one of those listed in
20909 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
20910
20911 &*Note*&: This option does not apply to timeouts, which do not return a status.
20912 See the &%timeout_defer%& option for how timeouts are handled.
20913
20914 .option log_defer_output pipe boolean false
20915 .cindex "&(pipe)& transport" "logging output"
20916 If this option is set, and the status returned by the command is
20917 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
20918 and any output was produced, the first line of it is written to the main log.
20919
20920
20921 .option log_fail_output pipe boolean false
20922 If this option is set, and the command returns any output, and also ends with a
20923 return code that is neither zero nor one of the return codes listed in
20924 &%temp_errors%& (that is, the delivery failed), the first line of output is
20925 written to the main log. This option and &%log_output%& are mutually exclusive.
20926 Only one of them may be set.
20927
20928
20929
20930 .option log_output pipe boolean false
20931 If this option is set and the command returns any output, the first line of
20932 output is written to the main log, whatever the return code. This option and
20933 &%log_fail_output%& are mutually exclusive. Only one of them may be set.
20934
20935
20936
20937 .option max_output pipe integer 20K
20938 This specifies the maximum amount of output that the command may produce on its
20939 standard output and standard error file combined. If the limit is exceeded, the
20940 process running the command is killed. This is intended as a safety measure to
20941 catch runaway processes. The limit is applied independently of the settings of
20942 the options that control what is done with such output (for example,
20943 &%return_output%&). Because of buffering effects, the amount of output may
20944 exceed the limit by a small amount before Exim notices.
20945
20946
20947 .option message_prefix pipe string&!! "see below"
20948 The string specified here is expanded and output at the start of every message.
20949 The default is unset if &%use_bsmtp%& is set. Otherwise it is
20950 .code
20951 message_prefix = \
20952 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
20953 ${tod_bsdinbox}\n
20954 .endd
20955 .cindex "Cyrus"
20956 .cindex "&%tmail%&"
20957 .cindex "&""From""& line"
20958 This is required by the commonly used &_/usr/bin/vacation_& program.
20959 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
20960 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
20961 setting
20962 .code
20963 message_prefix =
20964 .endd
20965 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
20966 &`\n`& to &`\r\n`& in &%message_prefix%&.
20967
20968
20969 .option message_suffix pipe string&!! "see below"
20970 The string specified here is expanded and output at the end of every message.
20971 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
20972 The suffix can be suppressed by setting
20973 .code
20974 message_suffix =
20975 .endd
20976 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
20977 &`\n`& to &`\r\n`& in &%message_suffix%&.
20978
20979
20980 .option path pipe string "see below"
20981 This option specifies the string that is set up in the PATH environment
20982 variable of the subprocess. The default is:
20983 .code
20984 /bin:/usr/bin
20985 .endd
20986 If the &%command%& option does not yield an absolute path name, the command is
20987 sought in the PATH directories, in the usual way. &*Warning*&: This does not
20988 apply to a command specified as a transport filter.
20989
20990
20991 .option pipe_as_creator pipe boolean false
20992 .cindex "uid (user id)" "local delivery"
20993 If the generic &%user%& option is not set and this option is true, the delivery
20994 process is run under the uid that was in force when Exim was originally called
20995 to accept the message. If the group id is not otherwise set (via the generic
20996 &%group%& option), the gid that was in force when Exim was originally called to
20997 accept the message is used.
20998
20999
21000 .option restrict_to_path pipe boolean false
21001 When this option is set, any command name not listed in &%allow_commands%& must
21002 contain no slashes. The command is searched for only in the directories listed
21003 in the &%path%& option. This option is intended for use in the case when a pipe
21004 command has been generated from a user's &_.forward_& file. This is usually
21005 handled by a &(pipe)& transport called &%address_pipe%&.
21006
21007
21008 .option return_fail_output pipe boolean false
21009 If this option is true, and the command produced any output and ended with a
21010 return code other than zero or one of the codes listed in &%temp_errors%& (that
21011 is, the delivery failed), the output is returned in the bounce message.
21012 However, if the message has a null sender (that is, it is itself a bounce
21013 message), output from the command is discarded. This option and
21014 &%return_output%& are mutually exclusive. Only one of them may be set.
21015
21016
21017
21018 .option return_output pipe boolean false
21019 If this option is true, and the command produced any output, the delivery is
21020 deemed to have failed whatever the return code from the command, and the output
21021 is returned in the bounce message. Otherwise, the output is just discarded.
21022 However, if the message has a null sender (that is, it is a bounce message),
21023 output from the command is always discarded, whatever the setting of this
21024 option. This option and &%return_fail_output%& are mutually exclusive. Only one
21025 of them may be set.
21026
21027
21028
21029 .option temp_errors pipe "string list" "see below"
21030 .cindex "&(pipe)& transport" "temporary failure"
21031 This option contains either a colon-separated list of numbers, or a single
21032 asterisk. If &%ignore_status%& is false
21033 and &%return_output%& is not set,
21034 and the command exits with a non-zero return code, the failure is treated as
21035 temporary and the delivery is deferred if the return code matches one of the
21036 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
21037 codes are treated as permanent errors. The default setting contains the codes
21038 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
21039 compiled on a system that does not define these macros, it assumes values of 75
21040 and 73, respectively.
21041
21042
21043 .option timeout pipe time 1h
21044 If the command fails to complete within this time, it is killed. This normally
21045 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
21046 specifies no timeout. In order to ensure that any subprocesses created by the
21047 command are also killed, Exim makes the initial process a process group leader,
21048 and kills the whole process group on a timeout. However, this can be defeated
21049 if one of the processes starts a new process group.
21050
21051 .option timeout_defer pipe boolean false
21052 A timeout in a &(pipe)& transport, either in the command that the transport
21053 runs, or in a transport filter that is associated with it, is by default
21054 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
21055 is set true, both kinds of timeout become temporary errors, causing the
21056 delivery to be deferred.
21057
21058 .option umask pipe "octal integer" 022
21059 This specifies the umask setting for the subprocess that runs the command.
21060
21061
21062 .option use_bsmtp pipe boolean false
21063 .cindex "envelope sender"
21064 If this option is set true, the &(pipe)& transport writes messages in &"batch
21065 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
21066 commands. If you want to include a leading HELO command with such messages,
21067 you can do so by setting the &%message_prefix%& option. See section
21068 &<<SECTbatchSMTP>>& for details of batch SMTP.
21069
21070 .option use_classresources pipe boolean false
21071 .cindex "class resources (BSD)"
21072 This option is available only when Exim is running on FreeBSD, NetBSD, or
21073 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
21074 resource limits when a &(pipe)& transport is run to perform a delivery. The
21075 limits for the uid under which the pipe is to run are obtained from the login
21076 class database.
21077
21078
21079 .option use_crlf pipe boolean false
21080 .cindex "carriage return"
21081 .cindex "linefeed"
21082 This option causes lines to be terminated with the two-character CRLF sequence
21083 (carriage return, linefeed) instead of just a linefeed character. In the case
21084 of batched SMTP, the byte sequence written to the pipe is then an exact image
21085 of what would be sent down a real SMTP connection.
21086
21087 The contents of the &%message_prefix%& and &%message_suffix%& options are
21088 written verbatim, so must contain their own carriage return characters if these
21089 are needed. When &%use_bsmtp%& is not set, the default values for both
21090 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
21091 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
21092
21093
21094 .option use_shell pipe boolean false
21095 .vindex "&$pipe_addresses$&"
21096 If this option is set, it causes the command to be passed to &_/bin/sh_&
21097 instead of being run directly from the transport, as described in section
21098 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
21099 where the command is expected to be run under a shell and cannot easily be
21100 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
21101 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
21102 command is expanded as a single string, and handed to &_/bin/sh_& as data for
21103 its &%-c%& option.
21104
21105
21106
21107 .section "Using an external local delivery agent" "SECID143"
21108 .cindex "local delivery" "using an external agent"
21109 .cindex "&'procmail'&"
21110 .cindex "external local delivery"
21111 .cindex "delivery" "&'procmail'&"
21112 .cindex "delivery" "by external agent"
21113 The &(pipe)& transport can be used to pass all messages that require local
21114 delivery to a separate local delivery agent such as &%procmail%&. When doing
21115 this, care must be taken to ensure that the pipe is run under an appropriate
21116 uid and gid. In some configurations one wants this to be a uid that is trusted
21117 by the delivery agent to supply the correct sender of the message. It may be
21118 necessary to recompile or reconfigure the delivery agent so that it trusts an
21119 appropriate user. The following is an example transport and router
21120 configuration for &%procmail%&:
21121 .code
21122 # transport
21123 procmail_pipe:
21124 driver = pipe
21125 command = /usr/local/bin/procmail -d $local_part
21126 return_path_add
21127 delivery_date_add
21128 envelope_to_add
21129 check_string = "From "
21130 escape_string = ">From "
21131 user = $local_part
21132 group = mail
21133
21134 # router
21135 procmail:
21136 driver = accept
21137 check_local_user
21138 transport = procmail_pipe
21139 .endd
21140 In this example, the pipe is run as the local user, but with the group set to
21141 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
21142 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
21143 user to supply a correct sender address. If you do not specify either a
21144 &%group%& or a &%user%& option, the pipe command is run as the local user. The
21145 home directory is the user's home directory by default.
21146
21147 &*Note*&: The command that the pipe transport runs does &'not'& begin with
21148 .code
21149 IFS=" "
21150 .endd
21151 as shown in some &%procmail%& documentation, because Exim does not by default
21152 use a shell to run pipe commands.
21153
21154 .cindex "Cyrus"
21155 The next example shows a transport and a router for a system where local
21156 deliveries are handled by the Cyrus IMAP server.
21157 .code
21158 # transport
21159 local_delivery_cyrus:
21160 driver = pipe
21161 command = /usr/cyrus/bin/deliver \
21162 -m ${substr_1:$local_part_suffix} -- $local_part
21163 user = cyrus
21164 group = mail
21165 return_output
21166 log_output
21167 message_prefix =
21168 message_suffix =
21169
21170 # router
21171 local_user_cyrus:
21172 driver = accept
21173 check_local_user
21174 local_part_suffix = .*
21175 transport = local_delivery_cyrus
21176 .endd
21177 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
21178 &%return_output%& to cause any text written by Cyrus to be returned to the
21179 sender.
21180 .ecindex IIDpiptra1
21181 .ecindex IIDpiptra2
21182
21183
21184 . ////////////////////////////////////////////////////////////////////////////
21185 . ////////////////////////////////////////////////////////////////////////////
21186
21187 .chapter "The smtp transport" "CHAPsmtptrans"
21188 .scindex IIDsmttra1 "transports" "&(smtp)&"
21189 .scindex IIDsmttra2 "&(smtp)& transport"
21190 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
21191 or LMTP protocol. The list of hosts to try can either be taken from the address
21192 that is being processed (having been set up by the router), or specified
21193 explicitly for the transport. Timeout and retry processing (see chapter
21194 &<<CHAPretry>>&) is applied to each IP address independently.
21195
21196
21197 .section "Multiple messages on a single connection" "SECID144"
21198 The sending of multiple messages over a single TCP/IP connection can arise in
21199 two ways:
21200
21201 .ilist
21202 If a message contains more than &%max_rcpt%& (see below) addresses that are
21203 routed to the same host, more than one copy of the message has to be sent to
21204 that host. In this situation, multiple copies may be sent in a single run of
21205 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
21206 does when it has too many addresses to send in one message also depends on the
21207 value of the global &%remote_max_parallel%& option. Details are given in
21208 section &<<SECToutSMTPTCP>>&.)
21209 .next
21210 .cindex "hints database" "remembering routing"
21211 When a message has been successfully delivered over a TCP/IP connection, Exim
21212 looks in its hints database to see if there are any other messages awaiting a
21213 connection to the same host. If there are, a new delivery process is started
21214 for one of them, and the current TCP/IP connection is passed on to it. The new
21215 process may in turn send multiple copies and possibly create yet another
21216 process.
21217 .endlist
21218
21219
21220 For each copy sent over the same TCP/IP connection, a sequence counter is
21221 incremented, and if it ever gets to the value of &%connection_max_messages%&,
21222 no further messages are sent over that connection.
21223
21224
21225
21226 .section "Use of the $host and $host_address variables" "SECID145"
21227 .vindex "&$host$&"
21228 .vindex "&$host_address$&"
21229 At the start of a run of the &(smtp)& transport, the values of &$host$& and
21230 &$host_address$& are the name and IP address of the first host on the host list
21231 passed by the router. However, when the transport is about to connect to a
21232 specific host, and while it is connected to that host, &$host$& and
21233 &$host_address$& are set to the values for that host. These are the values
21234 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
21235 &%serialize_hosts%&, and the various TLS options are expanded.
21236
21237
21238 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
21239 .vindex &$tls_cipher$&
21240 .vindex &$tls_peerdn$&
21241 At the start of a run of the &(smtp)& transport, the values of &$tls_cipher$&
21242 and &$tls_peerdn$& are the values that were set when the message was received.
21243 These are the values that are used for options that are expanded before any
21244 SMTP connections are made. Just before each connection is made, these two
21245 variables are emptied. If TLS is subsequently started, they are set to the
21246 appropriate values for the outgoing connection, and these are the values that
21247 are in force when any authenticators are run and when the
21248 &%authenticated_sender%& option is expanded.
21249
21250
21251 .section "Private options for smtp" "SECID146"
21252 .cindex "options" "&(smtp)& transport"
21253 The private options of the &(smtp)& transport are as follows:
21254
21255
21256 .option address_retry_include_sender smtp boolean true
21257 .cindex "4&'xx'& responses" "retrying after"
21258 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
21259 is the combination of sender and recipient that is delayed in subsequent queue
21260 runs until the retry time is reached. You can delay the recipient without
21261 reference to the sender (which is what earlier versions of Exim did), by
21262 setting &%address_retry_include_sender%& false. However, this can lead to
21263 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
21264
21265 .option allow_localhost smtp boolean false
21266 .cindex "local host" "sending to"
21267 .cindex "fallback" "hosts specified on transport"
21268 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
21269 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
21270 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
21271 the delivery anyway. This should be used only in special cases when the
21272 configuration ensures that no looping will result (for example, a differently
21273 configured Exim is listening on the port to which the message is sent).
21274
21275
21276 .option authenticated_sender smtp string&!! unset
21277 .cindex "Cyrus"
21278 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
21279 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
21280 overriding any existing authenticated sender value. If the string expansion is
21281 forced to fail, the option is ignored. Other expansion failures cause delivery
21282 to be deferred. If the result of expansion is an empty string, that is also
21283 ignored.
21284
21285 The expansion happens after the outgoing connection has been made and TLS
21286 started, if required. This means that the &$host$&, &$host_address$&,
21287 &$tls_cipher$&, and &$tls_peerdn$& variables are set according to the
21288 particular connection.
21289
21290 If the SMTP session is not authenticated, the expansion of
21291 &%authenticated_sender%& still happens (and can cause the delivery to be
21292 deferred if it fails), but no AUTH= item is added to MAIL commands
21293 unless &%authenticated_sender_force%& is true.
21294
21295 This option allows you to use the &(smtp)& transport in LMTP mode to
21296 deliver mail to Cyrus IMAP and provide the proper local part as the
21297 &"authenticated sender"&, via a setting such as:
21298 .code
21299 authenticated_sender = $local_part
21300 .endd
21301 This removes the need for IMAP subfolders to be assigned special ACLs to
21302 allow direct delivery to those subfolders.
21303
21304 Because of expected uses such as that just described for Cyrus (when no
21305 domain is involved), there is no checking on the syntax of the provided
21306 value.
21307
21308
21309 .option authenticated_sender_force smtp boolean false
21310 If this option is set true, the &%authenticated_sender%& option's value
21311 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
21312 authenticated as a client.
21313
21314
21315 .option command_timeout smtp time 5m
21316 This sets a timeout for receiving a response to an SMTP command that has been
21317 sent out. It is also used when waiting for the initial banner line from the
21318 remote host. Its value must not be zero.
21319
21320
21321 .option connect_timeout smtp time 5m
21322 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
21323 to a remote host. A setting of zero allows the system timeout (typically
21324 several minutes) to act. To have any effect, the value of this option must be
21325 less than the system timeout. However, it has been observed that on some
21326 systems there is no system timeout, which is why the default value for this
21327 option is 5 minutes, a value recommended by RFC 1123.
21328
21329
21330 .option connection_max_messages smtp integer 500
21331 .cindex "SMTP" "passed connection"
21332 .cindex "SMTP" "multiple deliveries"
21333 .cindex "multiple SMTP deliveries"
21334 This controls the maximum number of separate message deliveries that are sent
21335 over a single TCP/IP connection. If the value is zero, there is no limit.
21336 For testing purposes, this value can be overridden by the &%-oB%& command line
21337 option.
21338
21339
21340 .option data_timeout smtp time 5m
21341 This sets a timeout for the transmission of each block in the data portion of
21342 the message. As a result, the overall timeout for a message depends on the size
21343 of the message. Its value must not be zero. See also &%final_timeout%&.
21344
21345
21346 .option delay_after_cutoff smtp boolean true
21347 This option controls what happens when all remote IP addresses for a given
21348 domain have been inaccessible for so long that they have passed their retry
21349 cutoff times.
21350
21351 In the default state, if the next retry time has not been reached for any of
21352 them, the address is bounced without trying any deliveries. In other words,
21353 Exim delays retrying an IP address after the final cutoff time until a new
21354 retry time is reached, and can therefore bounce an address without ever trying
21355 a delivery, when machines have been down for a long time. Some people are
21356 unhappy at this prospect, so...
21357
21358 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
21359 addresses are past their final cutoff time, Exim tries to deliver to those
21360 IP addresses that have not been tried since the message arrived. If there are
21361 none, of if they all fail, the address is bounced. In other words, it does not
21362 delay when a new message arrives, but immediately tries those expired IP
21363 addresses that haven't been tried since the message arrived. If there is a
21364 continuous stream of messages for the dead hosts, unsetting
21365 &%delay_after_cutoff%& means that there will be many more attempts to deliver
21366 to them.
21367
21368
21369 .option dns_qualify_single smtp boolean true
21370 If the &%hosts%& or &%fallback_hosts%& option is being used,
21371 and the &%gethostbyname%& option is false,
21372 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
21373 in chapter &<<CHAPdnslookup>>& for more details.
21374
21375
21376 .option dns_search_parents smtp boolean false
21377 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
21378 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
21379 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
21380 details.
21381
21382
21383
21384 .option fallback_hosts smtp "string list" unset
21385 .cindex "fallback" "hosts specified on transport"
21386 String expansion is not applied to this option. The argument must be a
21387 colon-separated list of host names or IP addresses, optionally also including
21388 port numbers, though the separator can be changed, as described in section
21389 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
21390 item in a &%route_list%& setting for the &(manualroute)& router, as described
21391 in section &<<SECTformatonehostitem>>&.
21392
21393 Fallback hosts can also be specified on routers, which associate them with the
21394 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
21395 &%fallback_hosts%& specified on the transport is used only if the address does
21396 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
21397 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
21398 However, &%hosts_randomize%& does apply to fallback host lists.
21399
21400 If Exim is unable to deliver to any of the hosts for a particular address, and
21401 the errors are not permanent rejections, the address is put on a separate
21402 transport queue with its host list replaced by the fallback hosts, unless the
21403 address was routed via MX records and the current host was in the original MX
21404 list. In that situation, the fallback host list is not used.
21405
21406 Once normal deliveries are complete, the fallback queue is delivered by
21407 re-running the same transports with the new host lists. If several failing
21408 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
21409 copy of the message is sent.
21410
21411 The resolution of the host names on the fallback list is controlled by the
21412 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
21413 both to cases when the host list comes with the address and when it is taken
21414 from &%hosts%&. This option provides a &"use a smart host only if delivery
21415 fails"& facility.
21416
21417
21418 .option final_timeout smtp time 10m
21419 This is the timeout that applies while waiting for the response to the final
21420 line containing just &"."& that terminates a message. Its value must not be
21421 zero.
21422
21423 .option gethostbyname smtp boolean false
21424 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
21425 being used, names are looked up using &[gethostbyname()]&
21426 (or &[getipnodebyname()]& when available)
21427 instead of using the DNS. Of course, that function may in fact use the DNS, but
21428 it may also consult other sources of information such as &_/etc/hosts_&.
21429
21430 .option gnutls_require_kx main string unset
21431 This option controls the key exchange mechanisms when GnuTLS is used in an Exim
21432 client. For details, see section &<<SECTreqciphgnu>>&.
21433
21434 .option gnutls_require_mac main string unset
21435 This option controls the MAC algorithms when GnuTLS is used in an Exim
21436 client. For details, see section &<<SECTreqciphgnu>>&.
21437
21438 .option gnutls_require_protocols main string unset
21439 This option controls the protocols when GnuTLS is used in an Exim
21440 client. For details, see section &<<SECTreqciphgnu>>&.
21441
21442 .option helo_data smtp string&!! "see below"
21443 .cindex "HELO" "argument, setting"
21444 .cindex "EHLO" "argument, setting"
21445 .cindex "LHLO argument setting"
21446 The value of this option is expanded after a connection to a another host has
21447 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
21448 command that starts the outgoing SMTP or LMTP session. The default value of the
21449 option is:
21450 .code
21451 $primary_hostname
21452 .endd
21453 During the expansion, the variables &$host$& and &$host_address$& are set to
21454 the identity of the remote host, and the variables &$sending_ip_address$& and
21455 &$sending_port$& are set to the local IP address and port number that are being
21456 used. These variables can be used to generate different values for different
21457 servers or different local IP addresses. For example, if you want the string
21458 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
21459 interface address, you could use this:
21460 .code
21461 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
21462 {$primary_hostname}}
21463 .endd
21464 The use of &%helo_data%& applies both to sending messages and when doing
21465 callouts.
21466
21467 .option hosts smtp "string list&!!" unset
21468 Hosts are associated with an address by a router such as &(dnslookup)&, which
21469 finds the hosts by looking up the address domain in the DNS, or by
21470 &(manualroute)&, which has lists of hosts in its configuration. However,
21471 email addresses can be passed to the &(smtp)& transport by any router, and not
21472 all of them can provide an associated list of hosts.
21473
21474 The &%hosts%& option specifies a list of hosts to be used if the address being
21475 processed does not have any hosts associated with it. The hosts specified by
21476 &%hosts%& are also used, whether or not the address has its own hosts, if
21477 &%hosts_override%& is set.
21478
21479 The string is first expanded, before being interpreted as a colon-separated
21480 list of host names or IP addresses, possibly including port numbers. The
21481 separator may be changed to something other than colon, as described in section
21482 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
21483 item in a &%route_list%& setting for the &(manualroute)& router, as described
21484 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
21485 of the &(manualroute)& router is not available here.
21486
21487 If the expansion fails, delivery is deferred. Unless the failure was caused by
21488 the inability to complete a lookup, the error is logged to the panic log as
21489 well as the main log. Host names are looked up either by searching directly for
21490 address records in the DNS or by calling &[gethostbyname()]& (or
21491 &[getipnodebyname()]& when available), depending on the setting of the
21492 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
21493 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
21494 address are used.
21495
21496 During delivery, the hosts are tried in order, subject to their retry status,
21497 unless &%hosts_randomize%& is set.
21498
21499
21500 .option hosts_avoid_esmtp smtp "host list&!!" unset
21501 .cindex "ESMTP, avoiding use of"
21502 .cindex "HELO" "forcing use of"
21503 .cindex "EHLO" "avoiding use of"
21504 .cindex "PIPELINING" "avoiding the use of"
21505 This option is for use with broken hosts that announce ESMTP facilities (for
21506 example, PIPELINING) and then fail to implement them properly. When a host
21507 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
21508 start of the SMTP session. This means that it cannot use any of the ESMTP
21509 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
21510
21511
21512 .option hosts_avoid_pipelining smtp "host list&!!" unset
21513 .cindex "PIPELINING" "avoiding the use of"
21514 Exim will not use the SMTP PIPELINING extension when delivering to any host
21515 that matches this list, even if the server host advertises PIPELINING support.
21516
21517
21518 .option hosts_avoid_tls smtp "host list&!!" unset
21519 .cindex "TLS" "avoiding for certain hosts"
21520 Exim will not try to start a TLS session when delivering to any host that
21521 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
21522
21523
21524 .option hosts_max_try smtp integer 5
21525 .cindex "host" "maximum number to try"
21526 .cindex "limit" "number of hosts tried"
21527 .cindex "limit" "number of MX tried"
21528 .cindex "MX record" "maximum tried"
21529 This option limits the number of IP addresses that are tried for any one
21530 delivery in cases where there are temporary delivery errors. Section
21531 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
21532
21533
21534 .option hosts_max_try_hardlimit smtp integer 50
21535 This is an additional check on the maximum number of IP addresses that Exim
21536 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
21537 why it exists.
21538
21539
21540
21541 .option hosts_nopass_tls smtp "host list&!!" unset
21542 .cindex "TLS" "passing connection"
21543 .cindex "multiple SMTP deliveries"
21544 .cindex "TLS" "multiple message deliveries"
21545 For any host that matches this list, a connection on which a TLS session has
21546 been started will not be passed to a new delivery process for sending another
21547 message on the same connection. See section &<<SECTmulmessam>>& for an
21548 explanation of when this might be needed.
21549
21550
21551 .option hosts_override smtp boolean false
21552 If this option is set and the &%hosts%& option is also set, any hosts that are
21553 attached to the address are ignored, and instead the hosts specified by the
21554 &%hosts%& option are always used. This option does not apply to
21555 &%fallback_hosts%&.
21556
21557
21558 .option hosts_randomize smtp boolean false
21559 .cindex "randomized host list"
21560 .cindex "host" "list of; randomized"
21561 .cindex "fallback" "randomized hosts"
21562 If this option is set, and either the list of hosts is taken from the
21563 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
21564 were not obtained from MX records (this includes fallback hosts from the
21565 router), and were not randomized by the router, the order of trying the hosts
21566 is randomized each time the transport runs. Randomizing the order of a host
21567 list can be used to do crude load sharing.
21568
21569 When &%hosts_randomize%& is true, a host list may be split into groups whose
21570 order is separately randomized. This makes it possible to set up MX-like
21571 behaviour. The boundaries between groups are indicated by an item that is just
21572 &`+`& in the host list. For example:
21573 .code
21574 hosts = host1:host2:host3:+:host4:host5
21575 .endd
21576 The order of the first three hosts and the order of the last two hosts is
21577 randomized for each use, but the first three always end up before the last two.
21578 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
21579
21580 .option hosts_require_auth smtp "host list&!!" unset
21581 .cindex "authentication" "required by client"
21582 This option provides a list of servers for which authentication must succeed
21583 before Exim will try to transfer a message. If authentication fails for
21584 servers which are not in this list, Exim tries to send unauthenticated. If
21585 authentication fails for one of these servers, delivery is deferred. This
21586 temporary error is detectable in the retry rules, so it can be turned into a
21587 hard failure if required. See also &%hosts_try_auth%&, and chapter
21588 &<<CHAPSMTPAUTH>>& for details of authentication.
21589
21590
21591 .option hosts_require_tls smtp "host list&!!" unset
21592 .cindex "TLS" "requiring for certain servers"
21593 Exim will insist on using a TLS session when delivering to any host that
21594 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
21595 &*Note*&: This option affects outgoing mail only. To insist on TLS for
21596 incoming messages, use an appropriate ACL.
21597
21598 .option hosts_try_auth smtp "host list&!!" unset
21599 .cindex "authentication" "optional in client"
21600 This option provides a list of servers to which, provided they announce
21601 authentication support, Exim will attempt to authenticate as a client when it
21602 connects. If authentication fails, Exim will try to transfer the message
21603 unauthenticated. See also &%hosts_require_auth%&, and chapter
21604 &<<CHAPSMTPAUTH>>& for details of authentication.
21605
21606 .option interface smtp "string list&!!" unset
21607 .cindex "bind IP address"
21608 .cindex "IP address" "binding"
21609 .vindex "&$host$&"
21610 .vindex "&$host_address$&"
21611 This option specifies which interface to bind to when making an outgoing SMTP
21612 call. The value is an IP address, not an interface name such as
21613 &`eth0`&. Do not confuse this with the interface address that was used when a
21614 message was received, which is in &$received_ip_address$&, formerly known as
21615 &$interface_address$&. The name was changed to minimize confusion with the
21616 outgoing interface address. There is no variable that contains an outgoing
21617 interface address because, unless it is set by this option, its value is
21618 unknown.
21619
21620 During the expansion of the &%interface%& option the variables &$host$& and
21621 &$host_address$& refer to the host to which a connection is about to be made
21622 during the expansion of the string. Forced expansion failure, or an empty
21623 string result causes the option to be ignored. Otherwise, after expansion, the
21624 string must be a list of IP addresses, colon-separated by default, but the
21625 separator can be changed in the usual way. For example:
21626 .code
21627 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
21628 .endd
21629 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
21630 connection. If none of them are the correct type, the option is ignored. If
21631 &%interface%& is not set, or is ignored, the system's IP functions choose which
21632 interface to use if the host has more than one.
21633
21634
21635 .option keepalive smtp boolean true
21636 .cindex "keepalive" "on outgoing connection"
21637 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
21638 connections. When set, it causes the kernel to probe idle connections
21639 periodically, by sending packets with &"old"& sequence numbers. The other end
21640 of the connection should send a acknowledgment if the connection is still okay
21641 or a reset if the connection has been aborted. The reason for doing this is
21642 that it has the beneficial effect of freeing up certain types of connection
21643 that can get stuck when the remote host is disconnected without tidying up the
21644 TCP/IP call properly. The keepalive mechanism takes several hours to detect
21645 unreachable hosts.
21646
21647
21648 .option lmtp_ignore_quota smtp boolean false
21649 .cindex "LMTP" "ignoring quota errors"
21650 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
21651 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
21652 has advertised support for IGNOREQUOTA in its response to the LHLO command.
21653
21654 .option max_rcpt smtp integer 100
21655 .cindex "RCPT" "maximum number of outgoing"
21656 This option limits the number of RCPT commands that are sent in a single
21657 SMTP message transaction. Each set of addresses is treated independently, and
21658 so can cause parallel connections to the same host if &%remote_max_parallel%&
21659 permits this.
21660
21661
21662 .option multi_domain smtp boolean true
21663 .vindex "&$domain$&"
21664 When this option is set, the &(smtp)& transport can handle a number of
21665 addresses containing a mixture of different domains provided they all resolve
21666 to the same list of hosts. Turning the option off restricts the transport to
21667 handling only one domain at a time. This is useful if you want to use
21668 &$domain$& in an expansion for the transport, because it is set only when there
21669 is a single domain involved in a remote delivery.
21670
21671
21672 .option port smtp string&!! "see below"
21673 .cindex "port" "sending TCP/IP"
21674 .cindex "TCP/IP" "setting outgoing port"
21675 This option specifies the TCP/IP port on the server to which Exim connects.
21676 &*Note:*& Do not confuse this with the port that was used when a message was
21677 received, which is in &$received_port$&, formerly known as &$interface_port$&.
21678 The name was changed to minimize confusion with the outgoing port. There is no
21679 variable that contains an outgoing port.
21680
21681 If the value of this option begins with a digit it is taken as a port number;
21682 otherwise it is looked up using &[getservbyname()]&. The default value is
21683 normally &"smtp"&, but if &%protocol%& is set to &"lmtp"&, the default is
21684 &"lmtp"&. If the expansion fails, or if a port number cannot be found, delivery
21685 is deferred.
21686
21687
21688
21689 .option protocol smtp string smtp
21690 .cindex "LMTP" "over TCP/IP"
21691 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
21692 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
21693 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
21694 deliveries into closed message stores. Exim also has support for running LMTP
21695 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
21696
21697
21698 .option retry_include_ip_address smtp boolean true
21699 Exim normally includes both the host name and the IP address in the key it
21700 constructs for indexing retry data after a temporary delivery failure. This
21701 means that when one of several IP addresses for a host is failing, it gets
21702 tried periodically (controlled by the retry rules), but use of the other IP
21703 addresses is not affected.
21704
21705 However, in some dialup environments hosts are assigned a different IP address
21706 each time they connect. In this situation the use of the IP address as part of
21707 the retry key leads to undesirable behaviour. Setting this option false causes
21708 Exim to use only the host name. This should normally be done on a separate
21709 instance of the &(smtp)& transport, set up specially to handle the dialup
21710 hosts.
21711
21712
21713 .option serialize_hosts smtp "host list&!!" unset
21714 .cindex "serializing connections"
21715 .cindex "host" "serializing connections"
21716 Because Exim operates in a distributed manner, if several messages for the same
21717 host arrive at around the same time, more than one simultaneous connection to
21718 the remote host can occur. This is not usually a problem except when there is a
21719 slow link between the hosts. In that situation it may be helpful to restrict
21720 Exim to one connection at a time. This can be done by setting
21721 &%serialize_hosts%& to match the relevant hosts.
21722
21723 .cindex "hints database" "serializing deliveries to a host"
21724 Exim implements serialization by means of a hints database in which a record is
21725 written whenever a process connects to one of the restricted hosts. The record
21726 is deleted when the connection is completed. Obviously there is scope for
21727 records to get left lying around if there is a system or program crash. To
21728 guard against this, Exim ignores any records that are more than six hours old.
21729
21730 If you set up this kind of serialization, you should also arrange to delete the
21731 relevant hints database whenever your system reboots. The names of the files
21732 start with &_misc_& and they are kept in the &_spool/db_& directory. There
21733 may be one or two files, depending on the type of DBM in use. The same files
21734 are used for ETRN serialization.
21735
21736
21737 .option size_addition smtp integer 1024
21738 .cindex "SMTP" "SIZE"
21739 .cindex "message" "size issue for transport filter"
21740 .cindex "size" "of message"
21741 .cindex "transport" "filter"
21742 .cindex "filter" "transport filter"
21743 If a remote SMTP server indicates that it supports the SIZE option of the
21744 MAIL command, Exim uses this to pass over the message size at the start of
21745 an SMTP transaction. It adds the value of &%size_addition%& to the value it
21746 sends, to allow for headers and other text that may be added during delivery by
21747 configuration options or in a transport filter. It may be necessary to increase
21748 this if a lot of text is added to messages.
21749
21750 Alternatively, if the value of &%size_addition%& is set negative, it disables
21751 the use of the SIZE option altogether.
21752
21753
21754 .option tls_certificate smtp string&!! unset
21755 .cindex "TLS" "client certificate, location of"
21756 .cindex "certificate" "client, location of"
21757 .vindex "&$host$&"
21758 .vindex "&$host_address$&"
21759 The value of this option must be the absolute path to a file which contains the
21760 client's certificate, for possible use when sending a message over an encrypted
21761 connection. The values of &$host$& and &$host_address$& are set to the name and
21762 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
21763 details of TLS.
21764
21765 &*Note*&: This option must be set if you want Exim to be able to use a TLS
21766 certificate when sending messages as a client. The global option of the same
21767 name specifies the certificate for Exim as a server; it is not automatically
21768 assumed that the same certificate should be used when Exim is operating as a
21769 client.
21770
21771
21772 .option tls_crl smtp string&!! unset
21773 .cindex "TLS" "client certificate revocation list"
21774 .cindex "certificate" "revocation list for client"
21775 This option specifies a certificate revocation list. The expanded value must
21776 be the name of a file that contains a CRL in PEM format.
21777
21778
21779 .option tls_privatekey smtp string&!! unset
21780 .cindex "TLS" "client private key, location of"
21781 .vindex "&$host$&"
21782 .vindex "&$host_address$&"
21783 The value of this option must be the absolute path to a file which contains the
21784 client's private key. This is used when sending a message over an encrypted
21785 connection using a client certificate. The values of &$host$& and
21786 &$host_address$& are set to the name and address of the server during the
21787 expansion. If this option is unset, or the expansion is forced to fail, or the
21788 result is an empty string, the private key is assumed to be in the same file as
21789 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
21790
21791
21792 .option tls_require_ciphers smtp string&!! unset
21793 .cindex "TLS" "requiring specific ciphers"
21794 .cindex "cipher" "requiring specific"
21795 .vindex "&$host$&"
21796 .vindex "&$host_address$&"
21797 The value of this option must be a list of permitted cipher suites, for use
21798 when setting up an outgoing encrypted connection. (There is a global option of
21799 the same name for controlling incoming connections.) The values of &$host$& and
21800 &$host_address$& are set to the name and address of the server during the
21801 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
21802 is used in different ways by OpenSSL and GnuTLS (see sections
21803 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
21804 ciphers is a preference order.
21805
21806
21807
21808 .option tls_tempfail_tryclear smtp boolean true
21809 .cindex "4&'xx'& responses" "to STARTTLS"
21810 When the server host is not in &%hosts_require_tls%&, and there is a problem in
21811 setting up a TLS session, this option determines whether or not Exim should try
21812 to deliver the message unencrypted. If it is set false, delivery to the
21813 current host is deferred; if there are other hosts, they are tried. If this
21814 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
21815 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
21816 TLS negotiation fails, Exim closes the current connection (because it is in an
21817 unknown state), opens a new one to the same host, and then tries the delivery
21818 in clear.
21819
21820
21821 .option tls_verify_certificates smtp string&!! unset
21822 .cindex "TLS" "server certificate verification"
21823 .cindex "certificate" "verification of server"
21824 .vindex "&$host$&"
21825 .vindex "&$host_address$&"
21826 The value of this option must be the absolute path to a file containing
21827 permitted server certificates, for use when setting up an encrypted connection.
21828 Alternatively, if you are using OpenSSL, you can set
21829 &%tls_verify_certificates%& to the name of a directory containing certificate
21830 files. This does not work with GnuTLS; the option must be set to the name of a
21831 single file if you are using GnuTLS. The values of &$host$& and
21832 &$host_address$& are set to the name and address of the server during the
21833 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
21834
21835
21836
21837
21838 .section "How the limits for the number of hosts to try are used" &&&
21839 "SECTvalhosmax"
21840 .cindex "host" "maximum number to try"
21841 .cindex "limit" "hosts; maximum number tried"
21842 There are two options that are concerned with the number of hosts that are
21843 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
21844 &%hosts_max_try_hardlimit%&.
21845
21846
21847 The &%hosts_max_try%& option limits the number of hosts that are tried
21848 for a single delivery. However, despite the term &"host"& in its name, the
21849 option actually applies to each IP address independently. In other words, a
21850 multihomed host is treated as several independent hosts, just as it is for
21851 retrying.
21852
21853 Many of the larger ISPs have multiple MX records which often point to
21854 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
21855 created as a result of routing one of these domains.
21856
21857 Trying every single IP address on such a long list does not seem sensible; if
21858 several at the top of the list fail, it is reasonable to assume there is some
21859 problem that is likely to affect all of them. Roughly speaking, the value of
21860 &%hosts_max_try%& is the maximum number that are tried before deferring the
21861 delivery. However, the logic cannot be quite that simple.
21862
21863 Firstly, IP addresses that are skipped because their retry times have not
21864 arrived do not count, and in addition, addresses that are past their retry
21865 limits are also not counted, even when they are tried. This means that when
21866 some IP addresses are past their retry limits, more than the value of
21867 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
21868 that all IP addresses are considered before timing out an email address (but
21869 see below for an exception).
21870
21871 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
21872 list to see if there is a subsequent host with a different (higher valued) MX.
21873 If there is, that host is considered next, and the current IP address is used
21874 but not counted. This behaviour helps in the case of a domain with a retry rule
21875 that hardly ever delays any hosts, as is now explained:
21876
21877 Consider the case of a long list of hosts with one MX value, and a few with a
21878 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
21879 hosts at the top of the list are tried at first. With the default retry rule,
21880 which specifies increasing retry times, the higher MX hosts are eventually
21881 tried when those at the top of the list are skipped because they have not
21882 reached their retry times.
21883
21884 However, it is common practice to put a fixed short retry time on domains for
21885 large ISPs, on the grounds that their servers are rarely down for very long.
21886 Unfortunately, these are exactly the domains that tend to resolve to long lists
21887 of hosts. The short retry time means that the lowest MX hosts are tried every
21888 time. The attempts may be in a different order because of random sorting, but
21889 without the special MX check, the higher MX hosts would never be tried until
21890 all the lower MX hosts had timed out (which might be several days), because
21891 there are always some lower MX hosts that have reached their retry times. With
21892 the special check, Exim considers at least one IP address from each MX value at
21893 every delivery attempt, even if the &%hosts_max_try%& limit has already been
21894 reached.
21895
21896 The above logic means that &%hosts_max_try%& is not a hard limit, and in
21897 particular, Exim normally eventually tries all the IP addresses before timing
21898 out an email address. When &%hosts_max_try%& was implemented, this seemed a
21899 reasonable thing to do. Recently, however, some lunatic DNS configurations have
21900 been set up with hundreds of IP addresses for some domains. It can
21901 take a very long time indeed for an address to time out in these cases.
21902
21903 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
21904 Exim never tries more than this number of IP addresses; if it hits this limit
21905 and they are all timed out, the email address is bounced, even though not all
21906 possible IP addresses have been tried.
21907 .ecindex IIDsmttra1
21908 .ecindex IIDsmttra2
21909
21910
21911
21912
21913
21914 . ////////////////////////////////////////////////////////////////////////////
21915 . ////////////////////////////////////////////////////////////////////////////
21916
21917 .chapter "Address rewriting" "CHAPrewrite"
21918 .scindex IIDaddrew "rewriting" "addresses"
21919 There are some circumstances in which Exim automatically rewrites domains in
21920 addresses. The two most common are when an address is given without a domain
21921 (referred to as an &"unqualified address"&) or when an address contains an
21922 abbreviated domain that is expanded by DNS lookup.
21923
21924 Unqualified envelope addresses are accepted only for locally submitted
21925 messages, or for messages that are received from hosts matching
21926 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
21927 appropriate. Unqualified addresses in header lines are qualified if they are in
21928 locally submitted messages, or messages from hosts that are permitted to send
21929 unqualified envelope addresses. Otherwise, unqualified addresses in header
21930 lines are neither qualified nor rewritten.
21931
21932 One situation in which Exim does &'not'& automatically rewrite a domain is
21933 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
21934 such a domain should be rewritten using the &"canonical"& name, and some MTAs
21935 do this. The new RFCs do not contain this suggestion.
21936
21937
21938 .section "Explicitly configured address rewriting" "SECID147"
21939 This chapter describes the rewriting rules that can be used in the
21940 main rewrite section of the configuration file, and also in the generic
21941 &%headers_rewrite%& option that can be set on any transport.
21942
21943 Some people believe that configured address rewriting is a Mortal Sin.
21944 Others believe that life is not possible without it. Exim provides the
21945 facility; you do not have to use it.
21946
21947 The main rewriting rules that appear in the &"rewrite"& section of the
21948 configuration file are applied to addresses in incoming messages, both envelope
21949 addresses and addresses in header lines. Each rule specifies the types of
21950 address to which it applies.
21951
21952 Whether or not addresses in header lines are rewritten depends on the origin of
21953 the headers and the type of rewriting. Global rewriting, that is, rewriting
21954 rules from the rewrite section of the configuration file, is applied only to
21955 those headers that were received with the message. Header lines that are added
21956 by ACLs or by a system filter or by individual routers or transports (which
21957 are specific to individual recipient addresses) are not rewritten by the global
21958 rules.
21959
21960 Rewriting at transport time, by means of the &%headers_rewrite%& option,
21961 applies all headers except those added by routers and transports. That is, as
21962 well as the headers that were received with the message, it also applies to
21963 headers that were added by an ACL or a system filter.
21964
21965
21966 In general, rewriting addresses from your own system or domain has some
21967 legitimacy. Rewriting other addresses should be done only with great care and
21968 in special circumstances. The author of Exim believes that rewriting should be
21969 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
21970 Although it can sometimes be used as a routing tool, this is very strongly
21971 discouraged.
21972
21973 There are two commonly encountered circumstances where rewriting is used, as
21974 illustrated by these examples:
21975
21976 .ilist
21977 The company whose domain is &'hitch.fict.example'& has a number of hosts that
21978 exchange mail with each other behind a firewall, but there is only a single
21979 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
21980 &'hitch.fict.example'& when sending mail off-site.
21981 .next
21982 A host rewrites the local parts of its own users so that, for example,
21983 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
21984 .endlist
21985
21986
21987
21988 .section "When does rewriting happen?" "SECID148"
21989 .cindex "rewriting" "timing of"
21990 .cindex "&ACL;" "rewriting addresses in"
21991 Configured address rewriting can take place at several different stages of a
21992 message's processing.
21993
21994 .vindex "&$sender_address$&"
21995 At the start of an ACL for MAIL, the sender address may have been rewritten
21996 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
21997 ordinary rewrite rules have yet been applied. If, however, the sender address
21998 is verified in the ACL, it is rewritten before verification, and remains
21999 rewritten thereafter. The subsequent value of &$sender_address$& is the
22000 rewritten address. This also applies if sender verification happens in a
22001 RCPT ACL. Otherwise, when the sender address is not verified, it is
22002 rewritten as soon as a message's header lines have been received.
22003
22004 .vindex "&$domain$&"
22005 .vindex "&$local_part$&"
22006 Similarly, at the start of an ACL for RCPT, the current recipient's address
22007 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
22008 rewrite rules have yet been applied to it. However, the behaviour is different
22009 from the sender address when a recipient is verified. The address is rewritten
22010 for the verification, but the rewriting is not remembered at this stage. The
22011 value of &$local_part$& and &$domain$& after verification are always the same
22012 as they were before (that is, they contain the unrewritten &-- except for
22013 SMTP-time rewriting &-- address).
22014
22015 As soon as a message's header lines have been received, all the envelope
22016 recipient addresses are permanently rewritten, and rewriting is also applied to
22017 the addresses in the header lines (if configured). This happens before adding
22018 any header lines that were specified in MAIL or RCPT ACLs, and
22019 .cindex "&[local_scan()]& function" "address rewriting; timing of"
22020 before the DATA ACL and &[local_scan()]& functions are run.
22021
22022 When an address is being routed, either for delivery or for verification,
22023 rewriting is applied immediately to child addresses that are generated by
22024 redirection, unless &%no_rewrite%& is set on the router.
22025
22026 .cindex "envelope sender" "rewriting at transport time"
22027 .cindex "rewriting" "at transport time"
22028 .cindex "header lines" "rewriting at transport time"
22029 At transport time, additional rewriting of addresses in header lines can be
22030 specified by setting the generic &%headers_rewrite%& option on a transport.
22031 This option contains rules that are identical in form to those in the rewrite
22032 section of the configuration file. They are applied to the original message
22033 header lines and any that were added by ACLs or a system filter. They are not
22034 applied to header lines that are added by routers or the transport.
22035
22036 The outgoing envelope sender can be rewritten by means of the &%return_path%&
22037 transport option. However, it is not possible to rewrite envelope recipients at
22038 transport time.
22039
22040
22041
22042
22043 .section "Testing the rewriting rules that apply on input" "SECID149"
22044 .cindex "rewriting" "testing"
22045 .cindex "testing" "rewriting"
22046 Exim's input rewriting configuration appears in a part of the run time
22047 configuration file headed by &"begin rewrite"&. It can be tested by the
22048 &%-brw%& command line option. This takes an address (which can be a full RFC
22049 2822 address) as its argument. The output is a list of how the address would be
22050 transformed by the rewriting rules for each of the different places it might
22051 appear in an incoming message, that is, for each different header and for the
22052 envelope sender and recipient fields. For example,
22053 .code
22054 exim -brw ph10@exim.workshop.example
22055 .endd
22056 might produce the output
22057 .code
22058 sender: Philip.Hazel@exim.workshop.example
22059 from: Philip.Hazel@exim.workshop.example
22060 to: ph10@exim.workshop.example
22061 cc: ph10@exim.workshop.example
22062 bcc: ph10@exim.workshop.example
22063 reply-to: Philip.Hazel@exim.workshop.example
22064 env-from: Philip.Hazel@exim.workshop.example
22065 env-to: ph10@exim.workshop.example
22066 .endd
22067 which shows that rewriting has been set up for that address when used in any of
22068 the source fields, but not when it appears as a recipient address. At the
22069 present time, there is no equivalent way of testing rewriting rules that are
22070 set for a particular transport.
22071
22072
22073 .section "Rewriting rules" "SECID150"
22074 .cindex "rewriting" "rules"
22075 The rewrite section of the configuration file consists of lines of rewriting
22076 rules in the form
22077 .display
22078 <&'source pattern'&> <&'replacement'&> <&'flags'&>
22079 .endd
22080 Rewriting rules that are specified for the &%headers_rewrite%& generic
22081 transport option are given as a colon-separated list. Each item in the list
22082 takes the same form as a line in the main rewriting configuration (except that
22083 any colons must be doubled, of course).
22084
22085 The formats of source patterns and replacement strings are described below.
22086 Each is terminated by white space, unless enclosed in double quotes, in which
22087 case normal quoting conventions apply inside the quotes. The flags are single
22088 characters which may appear in any order. Spaces and tabs between them are
22089 ignored.
22090
22091 For each address that could potentially be rewritten, the rules are scanned in
22092 order, and replacements for the address from earlier rules can themselves be
22093 replaced by later rules (but see the &"q"& and &"R"& flags).
22094
22095 The order in which addresses are rewritten is undefined, may change between
22096 releases, and must not be relied on, with one exception: when a message is
22097 received, the envelope sender is always rewritten first, before any header
22098 lines are rewritten. For example, the replacement string for a rewrite of an
22099 address in &'To:'& must not assume that the message's address in &'From:'& has
22100 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
22101 that the envelope sender has already been rewritten.
22102
22103 .vindex "&$domain$&"
22104 .vindex "&$local_part$&"
22105 The variables &$local_part$& and &$domain$& can be used in the replacement
22106 string to refer to the address that is being rewritten. Note that lookup-driven
22107 rewriting can be done by a rule of the form
22108 .code
22109 *@* ${lookup ...
22110 .endd
22111 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
22112 refer to the address that is being rewritten.
22113
22114
22115 .section "Rewriting patterns" "SECID151"
22116 .cindex "rewriting" "patterns"
22117 .cindex "address list" "in a rewriting pattern"
22118 The source pattern in a rewriting rule is any item which may appear in an
22119 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
22120 single-item address list, which means that it is expanded before being tested
22121 against the address. As always, if you use a regular expression as a pattern,
22122 you must take care to escape dollar and backslash characters, or use the &`\N`&
22123 facility to suppress string expansion within the regular expression.
22124
22125 Domains in patterns should be given in lower case. Local parts in patterns are
22126 case-sensitive. If you want to do case-insensitive matching of local parts, you
22127 can use a regular expression that starts with &`^(?i)`&.
22128
22129 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
22130 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
22131 depending on the type of match which occurred. These can be used in the
22132 replacement string to insert portions of the incoming address. &$0$& always
22133 refers to the complete incoming address. When a regular expression is used, the
22134 numerical variables are set from its capturing subexpressions. For other types
22135 of pattern they are set as follows:
22136
22137 .ilist
22138 If a local part or domain starts with an asterisk, the numerical variables
22139 refer to the character strings matched by asterisks, with &$1$& associated with
22140 the first asterisk, and &$2$& with the second, if present. For example, if the
22141 pattern
22142 .code
22143 *queen@*.fict.example
22144 .endd
22145 is matched against the address &'hearts-queen@wonderland.fict.example'& then
22146 .code
22147 $0 = hearts-queen@wonderland.fict.example
22148 $1 = hearts-
22149 $2 = wonderland
22150 .endd
22151 Note that if the local part does not start with an asterisk, but the domain
22152 does, it is &$1$& that contains the wild part of the domain.
22153
22154 .next
22155 If the domain part of the pattern is a partial lookup, the wild and fixed parts
22156 of the domain are placed in the next available numerical variables. Suppose,
22157 for example, that the address &'foo@bar.baz.example'& is processed by a
22158 rewriting rule of the form
22159 .display
22160 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
22161 .endd
22162 and the key in the file that matches the domain is &`*.baz.example`&. Then
22163 .code
22164 $1 = foo
22165 $2 = bar
22166 $3 = baz.example
22167 .endd
22168 If the address &'foo@baz.example'& is looked up, this matches the same
22169 wildcard file entry, and in this case &$2$& is set to the empty string, but
22170 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
22171 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
22172 whole domain. For non-partial domain lookups, no numerical variables are set.
22173 .endlist
22174
22175
22176 .section "Rewriting replacements" "SECID152"
22177 .cindex "rewriting" "replacements"
22178 If the replacement string for a rule is a single asterisk, addresses that
22179 match the pattern and the flags are &'not'& rewritten, and no subsequent
22180 rewriting rules are scanned. For example,
22181 .code
22182 hatta@lookingglass.fict.example * f
22183 .endd
22184 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
22185 &'From:'& headers.
22186
22187 .vindex "&$domain$&"
22188 .vindex "&$local_part$&"
22189 If the replacement string is not a single asterisk, it is expanded, and must
22190 yield a fully qualified address. Within the expansion, the variables
22191 &$local_part$& and &$domain$& refer to the address that is being rewritten.
22192 Any letters they contain retain their original case &-- they are not lower
22193 cased. The numerical variables are set up according to the type of pattern that
22194 matched the address, as described above. If the expansion is forced to fail by
22195 the presence of &"fail"& in a conditional or lookup item, rewriting by the
22196 current rule is abandoned, but subsequent rules may take effect. Any other
22197 expansion failure causes the entire rewriting operation to be abandoned, and an
22198 entry written to the panic log.
22199
22200
22201
22202 .section "Rewriting flags" "SECID153"
22203 There are three different kinds of flag that may appear on rewriting rules:
22204
22205 .ilist
22206 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
22207 c, f, h, r, s, t.
22208 .next
22209 A flag that specifies rewriting at SMTP time: S.
22210 .next
22211 Flags that control the rewriting process: Q, q, R, w.
22212 .endlist
22213
22214 For rules that are part of the &%headers_rewrite%& generic transport option,
22215 E, F, T, and S are not permitted.
22216
22217
22218
22219 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
22220 "SECID154"
22221 .cindex "rewriting" "flags"
22222 If none of the following flag letters, nor the &"S"& flag (see section
22223 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
22224 and to both the sender and recipient fields of the envelope, whereas a
22225 transport-time rewriting rule just applies to all headers. Otherwise, the
22226 rewriting rule is skipped unless the relevant addresses are being processed.
22227 .display
22228 &`E`& rewrite all envelope fields
22229 &`F`& rewrite the envelope From field
22230 &`T`& rewrite the envelope To field
22231 &`b`& rewrite the &'Bcc:'& header
22232 &`c`& rewrite the &'Cc:'& header
22233 &`f`& rewrite the &'From:'& header
22234 &`h`& rewrite all headers
22235 &`r`& rewrite the &'Reply-To:'& header
22236 &`s`& rewrite the &'Sender:'& header
22237 &`t`& rewrite the &'To:'& header
22238 .endd
22239 "All headers" means all of the headers listed above that can be selected
22240 individually, plus their &'Resent-'& versions. It does not include
22241 other headers such as &'Subject:'& etc.
22242
22243 You should be particularly careful about rewriting &'Sender:'& headers, and
22244 restrict this to special known cases in your own domains.
22245
22246
22247 .section "The SMTP-time rewriting flag" "SECTrewriteS"
22248 .cindex "SMTP" "rewriting malformed addresses"
22249 .cindex "RCPT" "rewriting argument of"
22250 .cindex "MAIL" "rewriting argument of"
22251 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
22252 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
22253 before any other processing; even before syntax checking. The pattern is
22254 required to be a regular expression, and it is matched against the whole of the
22255 data for the command, including any surrounding angle brackets.
22256
22257 .vindex "&$domain$&"
22258 .vindex "&$local_part$&"
22259 This form of rewrite rule allows for the handling of addresses that are not
22260 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
22261 input). Because the input is not required to be a syntactically valid address,
22262 the variables &$local_part$& and &$domain$& are not available during the
22263 expansion of the replacement string. The result of rewriting replaces the
22264 original address in the MAIL or RCPT command.
22265
22266
22267 .section "Flags controlling the rewriting process" "SECID155"
22268 There are four flags which control the way the rewriting process works. These
22269 take effect only when a rule is invoked, that is, when the address is of the
22270 correct type (matches the flags) and matches the pattern:
22271
22272 .ilist
22273 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
22274 unqualified local part. It is qualified with &%qualify_recipient%&. In the
22275 absence of &"Q"& the rewritten address must always include a domain.
22276 .next
22277 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
22278 even if no rewriting actually takes place because of a &"fail"& in the
22279 expansion. The &"q"& flag is not effective if the address is of the wrong type
22280 (does not match the flags) or does not match the pattern.
22281 .next
22282 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
22283 address, up to ten times. It can be combined with the &"q"& flag, to stop
22284 rewriting once it fails to match (after at least one successful rewrite).
22285 .next
22286 .cindex "rewriting" "whole addresses"
22287 When an address in a header is rewritten, the rewriting normally applies only
22288 to the working part of the address, with any comments and RFC 2822 &"phrase"&
22289 left unchanged. For example, rewriting might change
22290 .code
22291 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
22292 .endd
22293 into
22294 .code
22295 From: Ford Prefect <prefectf@hitch.fict.example>
22296 .endd
22297 .cindex "RFC 2047"
22298 Sometimes there is a need to replace the whole address item, and this can be
22299 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
22300 causes an address in a header line to be rewritten, the entire address is
22301 replaced, not just the working part. The replacement must be a complete RFC
22302 2822 address, including the angle brackets if necessary. If text outside angle
22303 brackets contains a character whose value is greater than 126 or less than 32
22304 (except for tab), the text is encoded according to RFC 2047. The character set
22305 is taken from &%headers_charset%&, which defaults to ISO-8859-1.
22306
22307 When the &"w"& flag is set on a rule that causes an envelope address to be
22308 rewritten, all but the working part of the replacement address is discarded.
22309 .endlist
22310
22311
22312 .section "Rewriting examples" "SECID156"
22313 Here is an example of the two common rewriting paradigms:
22314 .code
22315 *@*.hitch.fict.example $1@hitch.fict.example
22316 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
22317 {$value}fail}@hitch.fict.example bctfrF
22318 .endd
22319 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
22320 the string expansion to fail if the lookup does not succeed. In this context it
22321 has the effect of leaving the original address unchanged, but Exim goes on to
22322 consider subsequent rewriting rules, if any, because the &"q"& flag is not
22323 present in that rule. An alternative to &"fail"& would be to supply &$1$&
22324 explicitly, which would cause the rewritten address to be the same as before,
22325 at the cost of a small bit of processing. Not supplying either of these is an
22326 error, since the rewritten address would then contain no local part.
22327
22328 The first example above replaces the domain with a superior, more general
22329 domain. This may not be desirable for certain local parts. If the rule
22330 .code
22331 root@*.hitch.fict.example *
22332 .endd
22333 were inserted before the first rule, rewriting would be suppressed for the
22334 local part &'root'& at any domain ending in &'hitch.fict.example'&.
22335
22336 Rewriting can be made conditional on a number of tests, by making use of
22337 &${if$& in the expansion item. For example, to apply a rewriting rule only to
22338 messages that originate outside the local host:
22339 .code
22340 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
22341 {$1@hitch.fict.example}fail}"
22342 .endd
22343 The replacement string is quoted in this example because it contains white
22344 space.
22345
22346 .cindex "rewriting" "bang paths"
22347 .cindex "bang paths" "rewriting"
22348 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
22349 an address it treats it as an unqualified local part which it qualifies with
22350 the local qualification domain (if the source of the message is local or if the
22351 remote host is permitted to send unqualified addresses). Rewriting can
22352 sometimes be used to handle simple bang paths with a fixed number of
22353 components. For example, the rule
22354 .code
22355 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
22356 .endd
22357 rewrites a two-component bang path &'host.name!user'& as the domain address
22358 &'user@host.name'&. However, there is a security implication in using this as
22359 a global rewriting rule for envelope addresses. It can provide a backdoor
22360 method for using your system as a relay, because the incoming addresses appear
22361 to be local. If the bang path addresses are received via SMTP, it is safer to
22362 use the &"S"& flag to rewrite them as they are received, so that relay checking
22363 can be done on the rewritten addresses.
22364 .ecindex IIDaddrew
22365
22366
22367
22368
22369
22370 . ////////////////////////////////////////////////////////////////////////////
22371 . ////////////////////////////////////////////////////////////////////////////
22372
22373 .chapter "Retry configuration" "CHAPretry"
22374 .scindex IIDretconf1 "retry" "configuration, description of"
22375 .scindex IIDregconf2 "configuration file" "retry section"
22376 The &"retry"& section of the runtime configuration file contains a list of
22377 retry rules that control how often Exim tries to deliver messages that cannot
22378 be delivered at the first attempt. If there are no retry rules (the section is
22379 empty or not present), there are no retries. In this situation, temporary
22380 errors are treated as permanent. The default configuration contains a single,
22381 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
22382 line option can be used to test which retry rule will be used for a given
22383 address, domain and error.
22384
22385 The most common cause of retries is temporary failure to deliver to a remote
22386 host because the host is down, or inaccessible because of a network problem.
22387 Exim's retry processing in this case is applied on a per-host (strictly, per IP
22388 address) basis, not on a per-message basis. Thus, if one message has recently
22389 been delayed, delivery of a new message to the same host is not immediately
22390 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
22391 log selector is set, the message
22392 .cindex "retry" "time not reached"
22393 &"retry time not reached"& is written to the main log whenever a delivery is
22394 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
22395 the handling of errors during remote deliveries.
22396
22397 Retry processing applies to routing as well as to delivering, except as covered
22398 in the next paragraph. The retry rules do not distinguish between these
22399 actions. It is not possible, for example, to specify different behaviour for
22400 failures to route the domain &'snark.fict.example'& and failures to deliver to
22401 the host &'snark.fict.example'&. I didn't think anyone would ever need this
22402 added complication, so did not implement it. However, although they share the
22403 same retry rule, the actual retry times for routing and transporting a given
22404 domain are maintained independently.
22405
22406 When a delivery is not part of a queue run (typically an immediate delivery on
22407 receipt of a message), the routers are always run, and local deliveries are
22408 always attempted, even if retry times are set for them. This makes for better
22409 behaviour if one particular message is causing problems (for example, causing
22410 quota overflow, or provoking an error in a filter file). If such a delivery
22411 suffers a temporary failure, the retry data is updated as normal, and
22412 subsequent delivery attempts from queue runs occur only when the retry time for
22413 the local address is reached.
22414
22415 .section "Changing retry rules" "SECID157"
22416 If you change the retry rules in your configuration, you should consider
22417 whether or not to delete the retry data that is stored in Exim's spool area in
22418 files with names like &_db/retry_&. Deleting any of Exim's hints files is
22419 always safe; that is why they are called &"hints"&.
22420
22421 The hints retry data contains suggested retry times based on the previous
22422 rules. In the case of a long-running problem with a remote host, it might
22423 record the fact that the host has timed out. If your new rules increase the
22424 timeout time for such a host, you should definitely remove the old retry data
22425 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
22426 messages that it should now be retaining.
22427
22428
22429
22430 .section "Format of retry rules" "SECID158"
22431 .cindex "retry" "rules"
22432 Each retry rule occupies one line and consists of three or four parts,
22433 separated by white space: a pattern, an error name, an optional list of sender
22434 addresses, and a list of retry parameters. The pattern and sender lists must be
22435 enclosed in double quotes if they contain white space. The rules are searched
22436 in order until one is found where the pattern, error name, and sender list (if
22437 present) match the failing host or address, the error that occurred, and the
22438 message's sender, respectively.
22439
22440
22441 The pattern is any single item that may appear in an address list (see section
22442 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
22443 which means that it is expanded before being tested against the address that
22444 has been delayed. A negated address list item is permitted. Address
22445 list processing treats a plain domain name as if it were preceded by &"*@"&,
22446 which makes it possible for many retry rules to start with just a domain. For
22447 example,
22448 .code
22449 lookingglass.fict.example * F,24h,30m;
22450 .endd
22451 provides a rule for any address in the &'lookingglass.fict.example'& domain,
22452 whereas
22453 .code
22454 alice@lookingglass.fict.example * F,24h,30m;
22455 .endd
22456 applies only to temporary failures involving the local part &%alice%&.
22457 In practice, almost all rules start with a domain name pattern without a local
22458 part.
22459
22460 .cindex "regular expressions" "in retry rules"
22461 &*Warning*&: If you use a regular expression in a routing rule pattern, it
22462 must match a complete address, not just a domain, because that is how regular
22463 expressions work in address lists.
22464 .display
22465 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
22466 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
22467 .endd
22468
22469
22470 .section "Choosing which retry rule to use for address errors" "SECID159"
22471 When Exim is looking for a retry rule after a routing attempt has failed (for
22472 example, after a DNS timeout), each line in the retry configuration is tested
22473 against the complete address only if &%retry_use_local_part%& is set for the
22474 router. Otherwise, only the domain is used, except when matching against a
22475 regular expression, when the local part of the address is replaced with &"*"&.
22476 A domain on its own can match a domain pattern, or a pattern that starts with
22477 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
22478 &%check_local_user%& is true, and false for other routers.
22479
22480 Similarly, when Exim is looking for a retry rule after a local delivery has
22481 failed (for example, after a mailbox full error), each line in the retry
22482 configuration is tested against the complete address only if
22483 &%retry_use_local_part%& is set for the transport (it defaults true for all
22484 local transports).
22485
22486 .cindex "4&'xx'& responses" "retry rules for"
22487 However, when Exim is looking for a retry rule after a remote delivery attempt
22488 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
22489 whole address is always used as the key when searching the retry rules. The
22490 rule that is found is used to create a retry time for the combination of the
22491 failing address and the message's sender. It is the combination of sender and
22492 recipient that is delayed in subsequent queue runs until its retry time is
22493 reached. You can delay the recipient without regard to the sender by setting
22494 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
22495 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
22496 commands.
22497
22498
22499
22500 .section "Choosing which retry rule to use for host and message errors" &&&
22501 "SECID160"
22502 For a temporary error that is not related to an individual address (for
22503 example, a connection timeout), each line in the retry configuration is checked
22504 twice. First, the name of the remote host is used as a domain name (preceded by
22505 &"*@"& when matching a regular expression). If this does not match the line,
22506 the domain from the email address is tried in a similar fashion. For example,
22507 suppose the MX records for &'a.b.c.example'& are
22508 .code
22509 a.b.c.example MX 5 x.y.z.example
22510 MX 6 p.q.r.example
22511 MX 7 m.n.o.example
22512 .endd
22513 and the retry rules are
22514 .code
22515 p.q.r.example * F,24h,30m;
22516 a.b.c.example * F,4d,45m;
22517 .endd
22518 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
22519 first rule matches neither the host nor the domain, so Exim looks at the second
22520 rule. This does not match the host, but it does match the domain, so it is used
22521 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
22522 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
22523 first retry rule is used, because it matches the host.
22524
22525 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
22526 first rule to determine retry times, but for all the other hosts for the domain
22527 &'a.b.c.example'&, the second rule is used. The second rule is also used if
22528 routing to &'a.b.c.example'& suffers a temporary failure.
22529
22530 &*Note*&: The host name is used when matching the patterns, not its IP address.
22531 However, if a message is routed directly to an IP address without the use of a
22532 host name, for example, if a &(manualroute)& router contains a setting such as:
22533 .code
22534 route_list = *.a.example 192.168.34.23
22535 .endd
22536 then the &"host name"& that is used when searching for a retry rule is the
22537 textual form of the IP address.
22538
22539 .section "Retry rules for specific errors" "SECID161"
22540 .cindex "retry" "specific errors; specifying"
22541 The second field in a retry rule is the name of a particular error, or an
22542 asterisk, which matches any error. The errors that can be tested for are:
22543
22544 .vlist
22545 .vitem &%auth_failed%&
22546 Authentication failed when trying to send to a host in the
22547 &%hosts_require_auth%& list in an &(smtp)& transport.
22548
22549 .vitem &%data_4xx%&
22550 A 4&'xx'& error was received for an outgoing DATA command, either immediately
22551 after the command, or after sending the message's data.
22552
22553 .vitem &%mail_4xx%&
22554 A 4&'xx'& error was received for an outgoing MAIL command.
22555
22556 .vitem &%rcpt_4xx%&
22557 A 4&'xx'& error was received for an outgoing RCPT command.
22558 .endlist
22559
22560 For the three 4&'xx'& errors, either the first or both of the x's can be given
22561 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
22562 recognize 452 errors given to RCPT commands for addresses in a certain domain,
22563 and have retries every ten minutes with a one-hour timeout, you could set up a
22564 retry rule of this form:
22565 .code
22566 the.domain.name rcpt_452 F,1h,10m
22567 .endd
22568 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
22569 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
22570
22571 .vlist
22572 .vitem &%lost_connection%&
22573 A server unexpectedly closed the SMTP connection. There may, of course,
22574 legitimate reasons for this (host died, network died), but if it repeats a lot
22575 for the same host, it indicates something odd.
22576
22577 .vitem &%refused_MX%&
22578 A connection to a host obtained from an MX record was refused.
22579
22580 .vitem &%refused_A%&
22581 A connection to a host not obtained from an MX record was refused.
22582
22583 .vitem &%refused%&
22584 A connection was refused.
22585
22586 .vitem &%timeout_connect_MX%&
22587 A connection attempt to a host obtained from an MX record timed out.
22588
22589 .vitem &%timeout_connect_A%&
22590 A connection attempt to a host not obtained from an MX record timed out.
22591
22592 .vitem &%timeout_connect%&
22593 A connection attempt timed out.
22594
22595 .vitem &%timeout_MX%&
22596 There was a timeout while connecting or during an SMTP session with a host
22597 obtained from an MX record.
22598
22599 .vitem &%timeout_A%&
22600 There was a timeout while connecting or during an SMTP session with a host not
22601 obtained from an MX record.
22602
22603 .vitem &%timeout%&
22604 There was a timeout while connecting or during an SMTP session.
22605
22606 .vitem &%tls_required%&
22607 The server was required to use TLS (it matched &%hosts_require_tls%& in the
22608 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
22609 to STARTTLS, or there was a problem setting up the TLS connection.
22610
22611 .vitem &%quota%&
22612 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
22613 transport.
22614
22615 .vitem &%quota_%&<&'time'&>
22616 .cindex "quota" "error testing in retry rule"
22617 .cindex "retry" "quota error testing"
22618 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
22619 transport, and the mailbox has not been accessed for <&'time'&>. For example,
22620 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
22621 for four days.
22622 .endlist
22623
22624 .cindex "mailbox" "time of last read"
22625 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
22626 timeouts when the mailbox is full and is not being read by its owner. Ideally,
22627 it should be based on the last time that the user accessed the mailbox.
22628 However, it is not always possible to determine this. Exim uses the following
22629 heuristic rules:
22630
22631 .ilist
22632 If the mailbox is a single file, the time of last access (the &"atime"&) is
22633 used. As no new messages are being delivered (because the mailbox is over
22634 quota), Exim does not access the file, so this is the time of last user access.
22635 .next
22636 .cindex "maildir format" "time of last read"
22637 For a maildir delivery, the time of last modification of the &_new_&
22638 subdirectory is used. As the mailbox is over quota, no new files are created in
22639 the &_new_& subdirectory, because no new messages are being delivered. Any
22640 change to the &_new_& subdirectory is therefore assumed to be the result of an
22641 MUA moving a new message to the &_cur_& directory when it is first read. The
22642 time that is used is therefore the last time that the user read a new message.
22643 .next
22644 For other kinds of multi-file mailbox, the time of last access cannot be
22645 obtained, so a retry rule that uses this type of error field is never matched.
22646 .endlist
22647
22648 The quota errors apply both to system-enforced quotas and to Exim's own quota
22649 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
22650 when a local delivery is deferred because a partition is full (the ENOSPC
22651 error).
22652
22653
22654
22655 .section "Retry rules for specified senders" "SECID162"
22656 .cindex "retry" "rules; sender-specific"
22657 You can specify retry rules that apply only when the failing message has a
22658 specific sender. In particular, this can be used to define retry rules that
22659 apply only to bounce messages. The third item in a retry rule can be of this
22660 form:
22661 .display
22662 &`senders=`&<&'address list'&>
22663 .endd
22664 The retry timings themselves are then the fourth item. For example:
22665 .code
22666 * rcpt_4xx senders=: F,1h,30m
22667 .endd
22668 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
22669 host. If the address list contains white space, it must be enclosed in quotes.
22670 For example:
22671 .code
22672 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
22673 .endd
22674 &*Warning*&: This facility can be unhelpful if it is used for host errors
22675 (which do not depend on the recipient). The reason is that the sender is used
22676 only to match the retry rule. Once the rule has been found for a host error,
22677 its contents are used to set a retry time for the host, and this will apply to
22678 all messages, not just those with specific senders.
22679
22680 When testing retry rules using &%-brt%&, you can supply a sender using the
22681 &%-f%& command line option, like this:
22682 .code
22683 exim -f "" -brt user@dom.ain
22684 .endd
22685 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
22686 list is never matched.
22687
22688
22689
22690
22691
22692 .section "Retry parameters" "SECID163"
22693 .cindex "retry" "parameters in rules"
22694 The third (or fourth, if a senders list is present) field in a retry rule is a
22695 sequence of retry parameter sets, separated by semicolons. Each set consists of
22696 .display
22697 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
22698 .endd
22699 The letter identifies the algorithm for computing a new retry time; the cutoff
22700 time is the time beyond which this algorithm no longer applies, and the
22701 arguments vary the algorithm's action. The cutoff time is measured from the
22702 time that the first failure for the domain (combined with the local part if
22703 relevant) was detected, not from the time the message was received.
22704
22705 .cindex "retry" "algorithms"
22706 .cindex "retry" "fixed intervals"
22707 .cindex "retry" "increasing intervals"
22708 .cindex "retry" "random intervals"
22709 The available algorithms are:
22710
22711 .ilist
22712 &'F'&: retry at fixed intervals. There is a single time parameter specifying
22713 the interval.
22714 .next
22715 &'G'&: retry at geometrically increasing intervals. The first argument
22716 specifies a starting value for the interval, and the second a multiplier, which
22717 is used to increase the size of the interval at each retry.
22718 .next
22719 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
22720 retry, the previous interval is multiplied by the factor in order to get a
22721 maximum for the next interval. The minimum interval is the first argument of
22722 the parameter, and an actual interval is chosen randomly between them. Such a
22723 rule has been found to be helpful in cluster configurations when all the
22724 members of the cluster restart at once, and may therefore synchronize their
22725 queue processing times.
22726 .endlist
22727
22728 When computing the next retry time, the algorithm definitions are scanned in
22729 order until one whose cutoff time has not yet passed is reached. This is then
22730 used to compute a new retry time that is later than the current time. In the
22731 case of fixed interval retries, this simply means adding the interval to the
22732 current time. For geometrically increasing intervals, retry intervals are
22733 computed from the rule's parameters until one that is greater than the previous
22734 interval is found. The main configuration variable
22735 .cindex "limit" "retry interval"
22736 .cindex "retry" "interval, maximum"
22737 .oindex "&%retry_interval_max%&"
22738 &%retry_interval_max%& limits the maximum interval between retries. It
22739 cannot be set greater than &`24h`&, which is its default value.
22740
22741 A single remote domain may have a number of hosts associated with it, and each
22742 host may have more than one IP address. Retry algorithms are selected on the
22743 basis of the domain name, but are applied to each IP address independently. If,
22744 for example, a host has two IP addresses and one is unusable, Exim will
22745 generate retry times for it and will not try to use it until its next retry
22746 time comes. Thus the good IP address is likely to be tried first most of the
22747 time.
22748
22749 .cindex "hints database" "use for retrying"
22750 Retry times are hints rather than promises. Exim does not make any attempt to
22751 run deliveries exactly at the computed times. Instead, a queue runner process
22752 starts delivery processes for delayed messages periodically, and these attempt
22753 new deliveries only for those addresses that have passed their next retry time.
22754 If a new message arrives for a deferred address, an immediate delivery attempt
22755 occurs only if the address has passed its retry time. In the absence of new
22756 messages, the minimum time between retries is the interval between queue runner
22757 processes. There is not much point in setting retry times of five minutes if
22758 your queue runners happen only once an hour, unless there are a significant
22759 number of incoming messages (which might be the case on a system that is
22760 sending everything to a smart host, for example).
22761
22762 The data in the retry hints database can be inspected by using the
22763 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
22764 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
22765 &'exinext'& utility script can be used to find out what the next retry times
22766 are for the hosts associated with a particular mail domain, and also for local
22767 deliveries that have been deferred.
22768
22769
22770 .section "Retry rule examples" "SECID164"
22771 Here are some example retry rules:
22772 .code
22773 alice@wonderland.fict.example quota_5d F,7d,3h
22774 wonderland.fict.example quota_5d
22775 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
22776 lookingglass.fict.example * F,24h,30m;
22777 * refused_A F,2h,20m;
22778 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
22779 .endd
22780 The first rule sets up special handling for mail to
22781 &'alice@wonderland.fict.example'& when there is an over-quota error and the
22782 mailbox has not been read for at least 5 days. Retries continue every three
22783 hours for 7 days. The second rule handles over-quota errors for all other local
22784 parts at &'wonderland.fict.example'&; the absence of a local part has the same
22785 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
22786 fail are bounced immediately if the mailbox has not been read for at least 5
22787 days.
22788
22789 The third rule handles all other errors at &'wonderland.fict.example'&; retries
22790 happen every 15 minutes for an hour, then with geometrically increasing
22791 intervals until two days have passed since a delivery first failed. After the
22792 first hour there is a delay of one hour, then two hours, then four hours, and
22793 so on (this is a rather extreme example).
22794
22795 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
22796 They happen every 30 minutes for 24 hours only. The remaining two rules handle
22797 all other domains, with special action for connection refusal from hosts that
22798 were not obtained from an MX record.
22799
22800 The final rule in a retry configuration should always have asterisks in the
22801 first two fields so as to provide a general catch-all for any addresses that do
22802 not have their own special handling. This example tries every 15 minutes for 2
22803 hours, then with intervals starting at one hour and increasing by a factor of
22804 1.5 up to 16 hours, then every 8 hours up to 5 days.
22805
22806
22807
22808 .section "Timeout of retry data" "SECID165"
22809 .cindex "timeout" "of retry data"
22810 .oindex "&%retry_data_expire%&"
22811 .cindex "hints database" "data expiry"
22812 .cindex "retry" "timeout of data"
22813 Exim timestamps the data that it writes to its retry hints database. When it
22814 consults the data during a delivery it ignores any that is older than the value
22815 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
22816 been tried for 7 days, Exim will try to deliver to it immediately a message
22817 arrives, and if that fails, it will calculate a retry time as if it were
22818 failing for the first time.
22819
22820 This improves the behaviour for messages routed to rarely-used hosts such as MX
22821 backups. If such a host was down at one time, and happens to be down again when
22822 Exim tries a month later, using the old retry data would imply that it had been
22823 down all the time, which is not a justified assumption.
22824
22825 If a host really is permanently dead, this behaviour causes a burst of retries
22826 every now and again, but only if messages routed to it are rare. If there is a
22827 message at least once every 7 days the retry data never expires.
22828
22829
22830
22831
22832 .section "Long-term failures" "SECID166"
22833 .cindex "delivery failure, long-term"
22834 .cindex "retry" "after long-term failure"
22835 Special processing happens when an email address has been failing for so long
22836 that the cutoff time for the last algorithm is reached. For example, using the
22837 default retry rule:
22838 .code
22839 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
22840 .endd
22841 the cutoff time is four days. Reaching the retry cutoff is independent of how
22842 long any specific message has been failing; it is the length of continuous
22843 failure for the recipient address that counts.
22844
22845 When the cutoff time is reached for a local delivery, or for all the IP
22846 addresses associated with a remote delivery, a subsequent delivery failure
22847 causes Exim to give up on the address, and a bounce message is generated.
22848 In order to cater for new messages that use the failing address, a next retry
22849 time is still computed from the final algorithm, and is used as follows:
22850
22851 For local deliveries, one delivery attempt is always made for any subsequent
22852 messages. If this delivery fails, the address fails immediately. The
22853 post-cutoff retry time is not used.
22854
22855 If the delivery is remote, there are two possibilities, controlled by the
22856 .oindex "&%delay_after_cutoff%&"
22857 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
22858 default. Until the post-cutoff retry time for one of the IP addresses is
22859 reached, the failing email address is bounced immediately, without a delivery
22860 attempt taking place. After that time, one new delivery attempt is made to
22861 those IP addresses that are past their retry times, and if that still fails,
22862 the address is bounced and new retry times are computed.
22863
22864 In other words, when all the hosts for a given email address have been failing
22865 for a long time, Exim bounces rather then defers until one of the hosts' retry
22866 times is reached. Then it tries once, and bounces if that attempt fails. This
22867 behaviour ensures that few resources are wasted in repeatedly trying to deliver
22868 to a broken destination, but if the host does recover, Exim will eventually
22869 notice.
22870
22871 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
22872 addresses are past their final cutoff time, Exim tries to deliver to those IP
22873 addresses that have not been tried since the message arrived. If there are
22874 no suitable IP addresses, or if they all fail, the address is bounced. In other
22875 words, it does not delay when a new message arrives, but tries the expired
22876 addresses immediately, unless they have been tried since the message arrived.
22877 If there is a continuous stream of messages for the failing domains, setting
22878 &%delay_after_cutoff%& false means that there will be many more attempts to
22879 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
22880 true.
22881
22882 .section "Deliveries that work intermittently" "SECID167"
22883 .cindex "retry" "intermittently working deliveries"
22884 Some additional logic is needed to cope with cases where a host is
22885 intermittently available, or when a message has some attribute that prevents
22886 its delivery when others to the same address get through. In this situation,
22887 because some messages are successfully delivered, the &"retry clock"& for the
22888 host or address keeps getting reset by the successful deliveries, and so
22889 failing messages remain on the queue for ever because the cutoff time is never
22890 reached.
22891
22892 Two exceptional actions are applied to prevent this happening. The first
22893 applies to errors that are related to a message rather than a remote host.
22894 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
22895 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
22896 commands, and quota failures. For this type of error, if a message's arrival
22897 time is earlier than the &"first failed"& time for the error, the earlier time
22898 is used when scanning the retry rules to decide when to try next and when to
22899 time out the address.
22900
22901 The exceptional second action applies in all cases. If a message has been on
22902 the queue for longer than the cutoff time of any applicable retry rule for a
22903 given address, a delivery is attempted for that address, even if it is not yet
22904 time, and if this delivery fails, the address is timed out. A new retry time is
22905 not computed in this case, so that other messages for the same address are
22906 considered immediately.
22907 .ecindex IIDretconf1
22908 .ecindex IIDregconf2
22909
22910
22911
22912
22913
22914
22915 . ////////////////////////////////////////////////////////////////////////////
22916 . ////////////////////////////////////////////////////////////////////////////
22917
22918 .chapter "SMTP authentication" "CHAPSMTPAUTH"
22919 .scindex IIDauthconf1 "SMTP" "authentication configuration"
22920 .scindex IIDauthconf2 "authentication"
22921 The &"authenticators"& section of Exim's run time configuration is concerned
22922 with SMTP authentication. This facility is an extension to the SMTP protocol,
22923 described in RFC 2554, which allows a client SMTP host to authenticate itself
22924 to a server. This is a common way for a server to recognize clients that are
22925 permitted to use it as a relay. SMTP authentication is not of relevance to the
22926 transfer of mail between servers that have no managerial connection with each
22927 other.
22928
22929 .cindex "AUTH" "description of"
22930 Very briefly, the way SMTP authentication works is as follows:
22931
22932 .ilist
22933 The server advertises a number of authentication &'mechanisms'& in response to
22934 the client's EHLO command.
22935 .next
22936 The client issues an AUTH command, naming a specific mechanism. The command
22937 may, optionally, contain some authentication data.
22938 .next
22939 The server may issue one or more &'challenges'&, to which the client must send
22940 appropriate responses. In simple authentication mechanisms, the challenges are
22941 just prompts for user names and passwords. The server does not have to issue
22942 any challenges &-- in some mechanisms the relevant data may all be transmitted
22943 with the AUTH command.
22944 .next
22945 The server either accepts or denies authentication.
22946 .next
22947 If authentication succeeds, the client may optionally make use of the AUTH
22948 option on the MAIL command to pass an authenticated sender in subsequent
22949 mail transactions. Authentication lasts for the remainder of the SMTP
22950 connection.
22951 .next
22952 If authentication fails, the client may give up, or it may try a different
22953 authentication mechanism, or it may try transferring mail over the
22954 unauthenticated connection.
22955 .endlist
22956
22957 If you are setting up a client, and want to know which authentication
22958 mechanisms the server supports, you can use Telnet to connect to port 25 (the
22959 SMTP port) on the server, and issue an EHLO command. The response to this
22960 includes the list of supported mechanisms. For example:
22961 .display
22962 &`$ `&&*&`telnet server.example 25`&*&
22963 &`Trying 192.168.34.25...`&
22964 &`Connected to server.example.`&
22965 &`Escape character is &#x0027;^]&#x0027;.`&
22966 &`220 server.example ESMTP Exim 4.20 ...`&
22967 &*&`ehlo client.example`&*&
22968 &`250-server.example Hello client.example [10.8.4.5]`&
22969 &`250-SIZE 52428800`&
22970 &`250-PIPELINING`&
22971 &`250-AUTH PLAIN`&
22972 &`250 HELP`&
22973 .endd
22974 The second-last line of this example output shows that the server supports
22975 authentication using the PLAIN mechanism. In Exim, the different authentication
22976 mechanisms are configured by specifying &'authenticator'& drivers. Like the
22977 routers and transports, which authenticators are included in the binary is
22978 controlled by build-time definitions. The following are currently available,
22979 included by setting
22980 .code
22981 AUTH_CRAM_MD5=yes
22982 AUTH_CYRUS_SASL=yes
22983 AUTH_PLAINTEXT=yes
22984 AUTH_SPA=yes
22985 .endd
22986 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
22987 authentication mechanism (RFC 2195), and the second provides an interface to
22988 the Cyrus SASL authentication library. The third can be configured to support
22989 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
22990 not formally documented, but used by several MUAs. The fourth authenticator
22991 supports Microsoft's &'Secure Password Authentication'& mechanism.
22992
22993 The authenticators are configured using the same syntax as other drivers (see
22994 section &<<SECTfordricon>>&). If no authenticators are required, no
22995 authentication section need be present in the configuration file. Each
22996 authenticator can in principle have both server and client functions. When Exim
22997 is receiving SMTP mail, it is acting as a server; when it is sending out
22998 messages over SMTP, it is acting as a client. Authenticator configuration
22999 options are provided for use in both these circumstances.
23000
23001 To make it clear which options apply to which situation, the prefixes
23002 &%server_%& and &%client_%& are used on option names that are specific to
23003 either the server or the client function, respectively. Server and client
23004 functions are disabled if none of their options are set. If an authenticator is
23005 to be used for both server and client functions, a single definition, using
23006 both sets of options, is required. For example:
23007 .code
23008 cram:
23009 driver = cram_md5
23010 public_name = CRAM-MD5
23011 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
23012 client_name = ph10
23013 client_secret = secret2
23014 .endd
23015 The &%server_%& option is used when Exim is acting as a server, and the
23016 &%client_%& options when it is acting as a client.
23017
23018 Descriptions of the individual authenticators are given in subsequent chapters.
23019 The remainder of this chapter covers the generic options for the
23020 authenticators, followed by general discussion of the way authentication works
23021 in Exim.
23022
23023
23024
23025 .section "Generic options for authenticators" "SECID168"
23026 .cindex "authentication" "generic options"
23027 .cindex "options" "generic; for authenticators"
23028
23029 .option client_condition authenticators string&!! unset
23030 When Exim is authenticating as a client, it skips any authenticator whose
23031 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
23032 used, for example, to skip plain text authenticators when the connection is not
23033 encrypted by a setting such as:
23034 .code
23035 client_condition = ${if !eq{$tls_cipher}{}}
23036 .endd
23037 (Older documentation incorrectly states that &$tls_cipher$& contains the cipher
23038 used for incoming messages. In fact, during SMTP delivery, it contains the
23039 cipher used for the delivery.)
23040
23041
23042 .option driver authenticators string unset
23043 This option must always be set. It specifies which of the available
23044 authenticators is to be used.
23045
23046
23047 .option public_name authenticators string unset
23048 This option specifies the name of the authentication mechanism that the driver
23049 implements, and by which it is known to the outside world. These names should
23050 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
23051 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
23052 defaults to the driver's instance name.
23053
23054
23055 .option server_advertise_condition authenticators string&!! unset
23056 When a server is about to advertise an authentication mechanism, the condition
23057 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
23058 mechanism is not advertised.
23059 If the expansion fails, the mechanism is not advertised. If the failure was not
23060 forced, and was not caused by a lookup defer, the incident is logged.
23061 See section &<<SECTauthexiser>>& below for further discussion.
23062
23063
23064 .option server_condition authenticators string&!! unset
23065 This option must be set for a &%plaintext%& server authenticator, where it
23066 is used directly to control authentication. See section &<<SECTplainserver>>&
23067 for details.
23068
23069 For the other authenticators, &%server_condition%& can be used as an additional
23070 authentication or authorization mechanism that is applied after the other
23071 authenticator conditions succeed. If it is set, it is expanded when the
23072 authenticator would otherwise return a success code. If the expansion is forced
23073 to fail, authentication fails. Any other expansion failure causes a temporary
23074 error code to be returned. If the result of a successful expansion is an empty
23075 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
23076 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
23077 other result, a temporary error code is returned, with the expanded string as
23078 the error text.
23079
23080
23081 .option server_debug_print authenticators string&!! unset
23082 If this option is set and authentication debugging is enabled (see the &%-d%&
23083 command line option), the string is expanded and included in the debugging
23084 output when the authenticator is run as a server. This can help with checking
23085 out the values of variables.
23086 If expansion of the string fails, the error message is written to the debugging
23087 output, and Exim carries on processing.
23088
23089
23090 .option server_set_id authenticators string&!! unset
23091 .vindex "&$authenticated_id$&"
23092 When an Exim server successfully authenticates a client, this string is
23093 expanded using data from the authentication, and preserved for any incoming
23094 messages in the variable &$authenticated_id$&. It is also included in the log
23095 lines for incoming messages. For example, a user/password authenticator
23096 configuration might preserve the user name that was used to authenticate, and
23097 refer to it subsequently during delivery of the message.
23098 If expansion fails, the option is ignored.
23099
23100
23101 .option server_mail_auth_condition authenticators string&!! unset
23102 This option allows a server to discard authenticated sender addresses supplied
23103 as part of MAIL commands in SMTP connections that are authenticated by the
23104 driver on which &%server_mail_auth_condition%& is set. The option is not used
23105 as part of the authentication process; instead its (unexpanded) value is
23106 remembered for later use.
23107 How it is used is described in the following section.
23108
23109
23110
23111
23112
23113 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
23114 .cindex "authentication" "sender; authenticated"
23115 .cindex "AUTH" "on MAIL command"
23116 When a client supplied an AUTH= item on a MAIL command, Exim applies
23117 the following checks before accepting it as the authenticated sender of the
23118 message:
23119
23120 .ilist
23121 If the connection is not using extended SMTP (that is, HELO was used rather
23122 than EHLO), the use of AUTH= is a syntax error.
23123 .next
23124 If the value of the AUTH= parameter is &"<>"&, it is ignored.
23125 .next
23126 .vindex "&$authenticated_sender$&"
23127 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
23128 running, the value of &$authenticated_sender$& is set to the value obtained
23129 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
23130 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
23131 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
23132 given for the MAIL command.
23133 .next
23134 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
23135 is accepted and placed in &$authenticated_sender$& only if the client has
23136 authenticated.
23137 .next
23138 If the AUTH= value was accepted by either of the two previous rules, and
23139 the client has authenticated, and the authenticator has a setting for the
23140 &%server_mail_auth_condition%&, the condition is checked at this point. The
23141 valued that was saved from the authenticator is expanded. If the expansion
23142 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
23143 &$authenticated_sender$& is deleted. If the expansion yields any other value,
23144 the value of &$authenticated_sender$& is retained and passed on with the
23145 message.
23146 .endlist
23147
23148
23149 When &$authenticated_sender$& is set for a message, it is passed on to other
23150 hosts to which Exim authenticates as a client. Do not confuse this value with
23151 &$authenticated_id$&, which is a string obtained from the authentication
23152 process, and which is not usually a complete email address.
23153
23154 .vindex "&$sender_address$&"
23155 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
23156 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
23157 therefore make use of &$authenticated_sender$&. The converse is not true: the
23158 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
23159 ACL is run.
23160
23161
23162
23163 .section "Authentication on an Exim server" "SECTauthexiser"
23164 .cindex "authentication" "on an Exim server"
23165 When Exim receives an EHLO command, it advertises the public names of those
23166 authenticators that are configured as servers, subject to the following
23167 conditions:
23168
23169 .ilist
23170 The client host must match &%auth_advertise_hosts%& (default *).
23171 .next
23172 It the &%server_advertise_condition%& option is set, its expansion must not
23173 yield the empty string, &"0"&, &"no"&, or &"false"&.
23174 .endlist
23175
23176 The order in which the authenticators are defined controls the order in which
23177 the mechanisms are advertised.
23178
23179 Some mail clients (for example, some versions of Netscape) require the user to
23180 provide a name and password for authentication whenever AUTH is advertised,
23181 even though authentication may not in fact be needed (for example, Exim may be
23182 set up to allow unconditional relaying from the client by an IP address check).
23183 You can make such clients more friendly by not advertising AUTH to them.
23184 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
23185 that runs for RCPT) to relay without authentication, you should set
23186 .code
23187 auth_advertise_hosts = ! 10.9.8.0/24
23188 .endd
23189 so that no authentication mechanisms are advertised to them.
23190
23191 The &%server_advertise_condition%& controls the advertisement of individual
23192 authentication mechanisms. For example, it can be used to restrict the
23193 advertisement of a particular mechanism to encrypted connections, by a setting
23194 such as:
23195 .code
23196 server_advertise_condition = ${if eq{$tls_cipher}{}{no}{yes}}
23197 .endd
23198 .vindex "&$tls_cipher$&"
23199 If the session is encrypted, &$tls_cipher$& is not empty, and so the expansion
23200 yields &"yes"&, which allows the advertisement to happen.
23201
23202 When an Exim server receives an AUTH command from a client, it rejects it
23203 immediately if AUTH was not advertised in response to an earlier EHLO
23204 command. This is the case if
23205
23206 .ilist
23207 The client host does not match &%auth_advertise_hosts%&; or
23208 .next
23209 No authenticators are configured with server options; or
23210 .next
23211 Expansion of &%server_advertise_condition%& blocked the advertising of all the
23212 server authenticators.
23213 .endlist
23214
23215
23216 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
23217 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
23218 AUTH is accepted from any client host.
23219
23220 If AUTH is not rejected by the ACL, Exim searches its configuration for a
23221 server authentication mechanism that was advertised in response to EHLO and
23222 that matches the one named in the AUTH command. If it finds one, it runs
23223 the appropriate authentication protocol, and authentication either succeeds or
23224 fails. If there is no matching advertised mechanism, the AUTH command is
23225 rejected with a 504 error.
23226
23227 .vindex "&$received_protocol$&"
23228 .vindex "&$sender_host_authenticated$&"
23229 When a message is received from an authenticated host, the value of
23230 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
23231 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
23232 public name) of the authenticator driver that successfully authenticated the
23233 client from which the message was received. This variable is empty if there was
23234 no successful authentication.
23235
23236
23237
23238
23239 .section "Testing server authentication" "SECID169"
23240 .cindex "authentication" "testing a server"
23241 .cindex "AUTH" "testing a server"
23242 .cindex "base64 encoding" "creating authentication test data"
23243 Exim's &%-bh%& option can be useful for testing server authentication
23244 configurations. The data for the AUTH command has to be sent using base64
23245 encoding. A quick way to produce such data for testing is the following Perl
23246 script:
23247 .code
23248 use MIME::Base64;
23249 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
23250 .endd
23251 .cindex "binary zero" "in authentication data"
23252 This interprets its argument as a Perl string, and then encodes it. The
23253 interpretation as a Perl string allows binary zeros, which are required for
23254 some kinds of authentication, to be included in the data. For example, a
23255 command line to run this script on such data might be
23256 .code
23257 encode '\0user\0password'
23258 .endd
23259 Note the use of single quotes to prevent the shell interpreting the
23260 backslashes, so that they can be interpreted by Perl to specify characters
23261 whose code value is zero.
23262
23263 &*Warning 1*&: If either of the user or password strings starts with an octal
23264 digit, you must use three zeros instead of one after the leading backslash. If
23265 you do not, the octal digit that starts your string will be incorrectly
23266 interpreted as part of the code for the first character.
23267
23268 &*Warning 2*&: If there are characters in the strings that Perl interprets
23269 specially, you must use a Perl escape to prevent them being misinterpreted. For
23270 example, a command such as
23271 .code
23272 encode '\0user@domain.com\0pas$$word'
23273 .endd
23274 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
23275
23276 If you have the &%mimencode%& command installed, another way to do produce
23277 base64-encoded strings is to run the command
23278 .code
23279 echo -e -n `\0user\0password' | mimencode
23280 .endd
23281 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
23282 in the argument, and the &%-n%& option specifies no newline at the end of its
23283 output. However, not all versions of &%echo%& recognize these options, so you
23284 should check your version before relying on this suggestion.
23285
23286
23287
23288 .section "Authentication by an Exim client" "SECID170"
23289 .cindex "authentication" "on an Exim client"
23290 The &(smtp)& transport has two options called &%hosts_require_auth%& and
23291 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
23292 announces support for authentication, and the host matches an entry in either
23293 of these options, Exim (as a client) tries to authenticate as follows:
23294
23295 .ilist
23296 For each authenticator that is configured as a client, in the order in which
23297 they are defined in the configuration, it searches the authentication
23298 mechanisms announced by the server for one whose name matches the public name
23299 of the authenticator.
23300 .next
23301 .vindex "&$host$&"
23302 .vindex "&$host_address$&"
23303 When it finds one that matches, it runs the authenticator's client code. The
23304 variables &$host$& and &$host_address$& are available for any string expansions
23305 that the client might do. They are set to the server's name and IP address. If
23306 any expansion is forced to fail, the authentication attempt is abandoned, and
23307 Exim moves on to the next authenticator. Otherwise an expansion failure causes
23308 delivery to be deferred.
23309 .next
23310 If the result of the authentication attempt is a temporary error or a timeout,
23311 Exim abandons trying to send the message to the host for the moment. It will
23312 try again later. If there are any backup hosts available, they are tried in the
23313 usual way.
23314 .next
23315 If the response to authentication is a permanent error (5&'xx'& code), Exim
23316 carries on searching the list of authenticators and tries another one if
23317 possible. If all authentication attempts give permanent errors, or if there are
23318 no attempts because no mechanisms match (or option expansions force failure),
23319 what happens depends on whether the host matches &%hosts_require_auth%& or
23320 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
23321 delivery is deferred. The error can be detected in the retry rules, and thereby
23322 turned into a permanent error if you wish. In the second case, Exim tries to
23323 deliver the message unauthenticated.
23324 .endlist
23325
23326 .cindex "AUTH" "on MAIL command"
23327 When Exim has authenticated itself to a remote server, it adds the AUTH
23328 parameter to the MAIL commands it sends, if it has an authenticated sender for
23329 the message. If the message came from a remote host, the authenticated sender
23330 is the one that was receiving on an incoming MAIL command, provided that the
23331 incoming connection was authenticated and the &%server_mail_auth%& condition
23332 allowed the authenticated sender to be retained. If a local process calls Exim
23333 to send a message, the sender address that is built from the login name and
23334 &%qualify_domain%& is treated as authenticated. However, if the
23335 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
23336 the authenticated sender that was received with the message.
23337 .ecindex IIDauthconf1
23338 .ecindex IIDauthconf2
23339
23340
23341
23342
23343
23344
23345 . ////////////////////////////////////////////////////////////////////////////
23346 . ////////////////////////////////////////////////////////////////////////////
23347
23348 .chapter "The plaintext authenticator" "CHAPplaintext"
23349 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
23350 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
23351 The &(plaintext)& authenticator can be configured to support the PLAIN and
23352 LOGIN authentication mechanisms, both of which transfer authentication data as
23353 plain (unencrypted) text (though base64 encoded). The use of plain text is a
23354 security risk; you are strongly advised to insist on the use of SMTP encryption
23355 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
23356 use unencrypted plain text, you should not use the same passwords for SMTP
23357 connections as you do for login accounts.
23358
23359 .section "Plaintext options" "SECID171"
23360 .cindex "options" "&(plaintext)& authenticator (server)"
23361 When configured as a server, &(plaintext)& uses the following options:
23362
23363 .option server_condition authenticators string&!! unset
23364 This is actually a global authentication option, but it must be set in order to
23365 configure the &(plaintext)& driver as a server. Its use is described below.
23366
23367 .option server_prompts plaintext string&!! unset
23368 The contents of this option, after expansion, must be a colon-separated list of
23369 prompt strings. If expansion fails, a temporary authentication rejection is
23370 given.
23371
23372 .section "Using plaintext in a server" "SECTplainserver"
23373 .cindex "AUTH" "in &(plaintext)& authenticator"
23374 .cindex "binary zero" "in &(plaintext)& authenticator"
23375 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
23376 "in &(plaintext)& authenticator"
23377 .vindex "&$auth1$&, &$auth2$&, etc"
23378 .cindex "base64 encoding" "in &(plaintext)& authenticator"
23379
23380 When running as a server, &(plaintext)& performs the authentication test by
23381 expanding a string. The data sent by the client with the AUTH command, or in
23382 response to subsequent prompts, is base64 encoded, and so may contain any byte
23383 values when decoded. If any data is supplied with the command, it is treated as
23384 a list of strings, separated by NULs (binary zeros), the first three of which
23385 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
23386 (neither LOGIN nor PLAIN uses more than three strings).
23387
23388 For compatibility with previous releases of Exim, the values are also placed in
23389 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
23390 variables for this purpose is now deprecated, as it can lead to confusion in
23391 string expansions that also use them for other things.
23392
23393 If there are more strings in &%server_prompts%& than the number of strings
23394 supplied with the AUTH command, the remaining prompts are used to obtain more
23395 data. Each response from the client may be a list of NUL-separated strings.
23396
23397 .vindex "&$authenticated_id$&"
23398 Once a sufficient number of data strings have been received,
23399 &%server_condition%& is expanded. If the expansion is forced to fail,
23400 authentication fails. Any other expansion failure causes a temporary error code
23401 to be returned. If the result of a successful expansion is an empty string,
23402 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
23403 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
23404 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
23405 For any other result, a temporary error code is returned, with the expanded
23406 string as the error text.
23407
23408 &*Warning*&: If you use a lookup in the expansion to find the user's
23409 password, be sure to make the authentication fail if the user is unknown.
23410 There are good and bad examples at the end of the next section.
23411
23412
23413
23414 .section "The PLAIN authentication mechanism" "SECID172"
23415 .cindex "PLAIN authentication mechanism"
23416 .cindex "authentication" "PLAIN mechanism"
23417 .cindex "binary zero" "in &(plaintext)& authenticator"
23418 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
23419 sent as one item of data (that is, one combined string containing two NUL
23420 separators). The data is sent either as part of the AUTH command, or
23421 subsequently in response to an empty prompt from the server.
23422
23423 The second and third strings are a user name and a corresponding password.
23424 Using a single fixed user name and password as an example, this could be
23425 configured as follows:
23426 .code
23427 fixed_plain:
23428 driver = plaintext
23429 public_name = PLAIN
23430 server_prompts = :
23431 server_condition = \
23432 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
23433 server_set_id = $auth2
23434 .endd
23435 Note that the default result strings from &%if%& (&"true"& or an empty string)
23436 are exactly what we want here, so they need not be specified. Obviously, if the
23437 password contains expansion-significant characters such as dollar, backslash,
23438 or closing brace, they have to be escaped.
23439
23440 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
23441 the end of a string list are ignored). If all the data comes as part of the
23442 AUTH command, as is commonly the case, the prompt is not used. This
23443 authenticator is advertised in the response to EHLO as
23444 .code
23445 250-AUTH PLAIN
23446 .endd
23447 and a client host can authenticate itself by sending the command
23448 .code
23449 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
23450 .endd
23451 As this contains three strings (more than the number of prompts), no further
23452 data is required from the client. Alternatively, the client may just send
23453 .code
23454 AUTH PLAIN
23455 .endd
23456 to initiate authentication, in which case the server replies with an empty
23457 prompt. The client must respond with the combined data string.
23458
23459 The data string is base64 encoded, as required by the RFC. This example,
23460 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
23461 represents a zero byte. This is split up into three strings, the first of which
23462 is empty. The &%server_condition%& option in the authenticator checks that the
23463 second two are &`username`& and &`mysecret`& respectively.
23464
23465 Having just one fixed user name and password, as in this example, is not very
23466 realistic, though for a small organization with only a handful of
23467 authenticating clients it could make sense.
23468
23469 A more sophisticated instance of this authenticator could use the user name in
23470 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
23471 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
23472 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
23473 This is an incorrect example:
23474 .code
23475 server_condition = \
23476 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
23477 .endd
23478 The expansion uses the user name (&$auth2$&) as the key to look up a password,
23479 which it then compares to the supplied password (&$auth3$&). Why is this example
23480 incorrect? It works fine for existing users, but consider what happens if a
23481 non-existent user name is given. The lookup fails, but as no success/failure
23482 strings are given for the lookup, it yields an empty string. Thus, to defeat
23483 the authentication, all a client has to do is to supply a non-existent user
23484 name and an empty password. The correct way of writing this test is:
23485 .code
23486 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
23487 {${if eq{$value}{$auth3}}} {false}}
23488 .endd
23489 In this case, if the lookup succeeds, the result is checked; if the lookup
23490 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
23491 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
23492 always fails if its second argument is empty. However, the second way of
23493 writing the test makes the logic clearer.
23494
23495
23496 .section "The LOGIN authentication mechanism" "SECID173"
23497 .cindex "LOGIN authentication mechanism"
23498 .cindex "authentication" "LOGIN mechanism"
23499 The LOGIN authentication mechanism is not documented in any RFC, but is in use
23500 in a number of programs. No data is sent with the AUTH command. Instead, a
23501 user name and password are supplied separately, in response to prompts. The
23502 plaintext authenticator can be configured to support this as in this example:
23503 .code
23504 fixed_login:
23505 driver = plaintext
23506 public_name = LOGIN
23507 server_prompts = User Name : Password
23508 server_condition = \
23509 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
23510 server_set_id = $auth1
23511 .endd
23512 Because of the way plaintext operates, this authenticator accepts data supplied
23513 with the AUTH command (in contravention of the specification of LOGIN), but
23514 if the client does not supply it (as is the case for LOGIN clients), the prompt
23515 strings are used to obtain two data items.
23516
23517 Some clients are very particular about the precise text of the prompts. For
23518 example, Outlook Express is reported to recognize only &"Username:"& and
23519 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
23520 strings. It uses the &%ldapauth%& expansion condition to check the user
23521 name and password by binding to an LDAP server:
23522 .code
23523 login:
23524 driver = plaintext
23525 public_name = LOGIN
23526 server_prompts = Username:: : Password::
23527 server_condition = ${if and{{
23528 !eq{}{$auth1} }{ \
23529 ldapauth{user="cn=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
23530 pass=${quote:$auth2} \
23531 ldap://ldap.example.org/} }} }
23532 server_set_id = uid=$auth1,ou=people,o=example.org
23533 .endd
23534 We have to check that the username is not empty before using it, because LDAP
23535 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
23536 operator to correctly quote the DN for authentication. However, the basic
23537 &%quote%& operator, rather than any of the LDAP quoting operators, is the
23538 correct one to use for the password, because quoting is needed only to make
23539 the password conform to the Exim syntax. At the LDAP level, the password is an
23540 uninterpreted string.
23541
23542
23543
23544 .section "Support for different kinds of authentication" "SECID174"
23545 A number of string expansion features are provided for the purpose of
23546 interfacing to different ways of user authentication. These include checking
23547 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
23548 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
23549 &<<SECTexpcond>>&.
23550
23551
23552
23553
23554 .section "Using plaintext in a client" "SECID175"
23555 .cindex "options" "&(plaintext)& authenticator (client)"
23556 The &(plaintext)& authenticator has two client options:
23557
23558 .option client_ignore_invalid_base64 plaintext boolean false
23559 If the client receives a server prompt that is not a valid base64 string,
23560 authentication is abandoned by default. However, if this option is set true,
23561 the error in the challenge is ignored and the client sends the response as
23562 usual.
23563
23564 .option client_send plaintext string&!! unset
23565 The string is a colon-separated list of authentication data strings. Each
23566 string is independently expanded before being sent to the server. The first
23567 string is sent with the AUTH command; any more strings are sent in response
23568 to prompts from the server. Before each string is expanded, the value of the
23569 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
23570 with &$auth1$& for the first prompt. Up to three prompts are stored in this
23571 way. Thus, the prompt that is received in response to sending the first string
23572 (with the AUTH command) can be used in the expansion of the second string, and
23573 so on. If an invalid base64 string is received when
23574 &%client_ignore_invalid_base64%& is set, an empty string is put in the
23575 &$auth$&<&'n'&> variable.
23576
23577 &*Note*&: You cannot use expansion to create multiple strings, because
23578 splitting takes priority and happens first.
23579
23580 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
23581 the data, further processing is applied to each string before it is sent. If
23582 there are any single circumflex characters in the string, they are converted to
23583 NULs. Should an actual circumflex be required as data, it must be doubled in
23584 the string.
23585
23586 This is an example of a client configuration that implements the PLAIN
23587 authentication mechanism with a fixed user name and password:
23588 .code
23589 fixed_plain:
23590 driver = plaintext
23591 public_name = PLAIN
23592 client_send = ^username^mysecret
23593 .endd
23594 The lack of colons means that the entire text is sent with the AUTH
23595 command, with the circumflex characters converted to NULs. A similar example
23596 that uses the LOGIN mechanism is:
23597 .code
23598 fixed_login:
23599 driver = plaintext
23600 public_name = LOGIN
23601 client_send = : username : mysecret
23602 .endd
23603 The initial colon means that the first string is empty, so no data is sent with
23604 the AUTH command itself. The remaining strings are sent in response to
23605 prompts.
23606 .ecindex IIDplaiauth1
23607 .ecindex IIDplaiauth2
23608
23609
23610
23611
23612 . ////////////////////////////////////////////////////////////////////////////
23613 . ////////////////////////////////////////////////////////////////////////////
23614
23615 .chapter "The cram_md5 authenticator" "CHID9"
23616 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
23617 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
23618 .cindex "CRAM-MD5 authentication mechanism"
23619 .cindex "authentication" "CRAM-MD5 mechanism"
23620 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
23621 sends a challenge string to the client, and the response consists of a user
23622 name and the CRAM-MD5 digest of the challenge string combined with a secret
23623 string (password) which is known to both server and client. Thus, the secret
23624 is not sent over the network as plain text, which makes this authenticator more
23625 secure than &(plaintext)&. However, the downside is that the secret has to be
23626 available in plain text at either end.
23627
23628
23629 .section "Using cram_md5 as a server" "SECID176"
23630 .cindex "options" "&(cram_md5)& authenticator (server)"
23631 This authenticator has one server option, which must be set to configure the
23632 authenticator as a server:
23633
23634 .option server_secret cram_md5 string&!! unset
23635 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
23636 When the server receives the client's response, the user name is placed in
23637 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
23638 obtain the password for that user. The server then computes the CRAM-MD5 digest
23639 that the client should have sent, and checks that it received the correct
23640 string. If the expansion of &%server_secret%& is forced to fail, authentication
23641 fails. If the expansion fails for some other reason, a temporary error code is
23642 returned to the client.
23643
23644 For compatibility with previous releases of Exim, the user name is also placed
23645 in &$1$&. However, the use of this variables for this purpose is now
23646 deprecated, as it can lead to confusion in string expansions that also use
23647 numeric variables for other things.
23648
23649 For example, the following authenticator checks that the user name given by the
23650 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
23651 user name, authentication fails.
23652 .code
23653 fixed_cram:
23654 driver = cram_md5
23655 public_name = CRAM-MD5
23656 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
23657 server_set_id = $auth1
23658 .endd
23659 .vindex "&$authenticated_id$&"
23660 If authentication succeeds, the setting of &%server_set_id%& preserves the user
23661 name in &$authenticated_id$&. A more typical configuration might look up the
23662 secret string in a file, using the user name as the key. For example:
23663 .code
23664 lookup_cram:
23665 driver = cram_md5
23666 public_name = CRAM-MD5
23667 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
23668 {$value}fail}
23669 server_set_id = $auth1
23670 .endd
23671 Note that this expansion explicitly forces failure if the lookup fails
23672 because &$auth1$& contains an unknown user name.
23673
23674
23675 .section "Using cram_md5 as a client" "SECID177"
23676 .cindex "options" "&(cram_md5)& authenticator (client)"
23677 When used as a client, the &(cram_md5)& authenticator has two options:
23678
23679
23680
23681 .option client_name cram_md5 string&!! "the primary host name"
23682 This string is expanded, and the result used as the user name data when
23683 computing the response to the server's challenge.
23684
23685
23686 .option client_secret cram_md5 string&!! unset
23687 This option must be set for the authenticator to work as a client. Its value is
23688 expanded and the result used as the secret string when computing the response.
23689
23690
23691 .vindex "&$host$&"
23692 .vindex "&$host_address$&"
23693 Different user names and secrets can be used for different servers by referring
23694 to &$host$& or &$host_address$& in the options. Forced failure of either
23695 expansion string is treated as an indication that this authenticator is not
23696 prepared to handle this case. Exim moves on to the next configured client
23697 authenticator. Any other expansion failure causes Exim to give up trying to
23698 send the message to the current server.
23699
23700 A simple example configuration of a &(cram_md5)& authenticator, using fixed
23701 strings, is:
23702 .code
23703 fixed_cram:
23704 driver = cram_md5
23705 public_name = CRAM-MD5
23706 client_name = ph10
23707 client_secret = secret
23708 .endd
23709 .ecindex IIDcramauth1
23710 .ecindex IIDcramauth2
23711
23712
23713
23714 . ////////////////////////////////////////////////////////////////////////////
23715 . ////////////////////////////////////////////////////////////////////////////
23716
23717 .chapter "The cyrus_sasl authenticator" "CHID10"
23718 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
23719 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
23720 .cindex "Cyrus" "SASL library"
23721 .cindex "Kerberos"
23722 The code for this authenticator was provided by Matthew Byng-Maddick of A L
23723 Digital Ltd (&url(http://www.aldigital.co.uk)).
23724
23725 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
23726 library implementation of the RFC 2222 (&"Simple Authentication and Security
23727 Layer"&). This library supports a number of authentication mechanisms,
23728 including PLAIN and LOGIN, but also several others that Exim does not support
23729 directly. In particular, there is support for Kerberos authentication.
23730
23731 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
23732 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
23733 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
23734 name of the driver to determine which mechanism to support.
23735
23736 Where access to some kind of secret file is required, for example in GSSAPI
23737 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
23738 user, and that the Cyrus SASL library has no way of escalating privileges
23739 by default. You may also find you need to set environment variables,
23740 depending on the driver you are using.
23741
23742 The application name provided by Exim is &"exim"&, so various SASL options may
23743 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
23744 Kerberos, note that because of limitations in the GSSAPI interface,
23745 changing the server keytab might need to be communicated down to the Kerberos
23746 layer independently. The mechanism for doing so is dependent upon the Kerberos
23747 implementation. For example, for Heimdal, the environment variable KRB5_KTNAME
23748 may be set to point to an alternative keytab file. Exim will pass this
23749 variable through from its own inherited environment when started as root or the
23750 Exim user. The keytab file needs to be readable by the Exim user.
23751
23752
23753 .section "Using cyrus_sasl as a server" "SECID178"
23754 The &(cyrus_sasl)& authenticator has four private options. It puts the username
23755 (on a successful authentication) into &$auth1$&. For compatibility with
23756 previous releases of Exim, the username is also placed in &$1$&. However, the
23757 use of this variable for this purpose is now deprecated, as it can lead to
23758 confusion in string expansions that also use numeric variables for other
23759 things.
23760
23761
23762 .option server_hostname cyrus_sasl string&!! "see below"
23763 This option selects the hostname that is used when communicating with the
23764 library. The default value is &`$primary_hostname`&. It is up to the underlying
23765 SASL plug-in what it does with this data.
23766
23767
23768 .option server_mech cyrus_sasl string "see below"
23769 This option selects the authentication mechanism this driver should use. The
23770 default is the value of the generic &%public_name%& option. This option allows
23771 you to use a different underlying mechanism from the advertised name. For
23772 example:
23773 .code
23774 sasl:
23775 driver = cyrus_sasl
23776 public_name = X-ANYTHING
23777 server_mech = CRAM-MD5
23778 server_set_id = $auth1
23779 .endd
23780
23781 .option server_realm cyrus_sasl string unset
23782 This specifies the SASL realm that the server claims to be in.
23783
23784
23785 .option server_service cyrus_sasl string &`smtp`&
23786 This is the SASL service that the server claims to implement.
23787
23788
23789 For straightforward cases, you do not need to set any of the authenticator's
23790 private options. All you need to do is to specify an appropriate mechanism as
23791 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
23792 PLAIN, you could have two authenticators as follows:
23793 .code
23794 sasl_cram_md5:
23795 driver = cyrus_sasl
23796 public_name = CRAM-MD5
23797 server_set_id = $auth1
23798
23799 sasl_plain:
23800 driver = cyrus_sasl
23801 public_name = PLAIN
23802 server_set_id = $auth1
23803 .endd
23804 Cyrus SASL does implement the LOGIN authentication method, even though it is
23805 not a standard method. It is disabled by default in the source distribution,
23806 but it is present in many binary distributions.
23807 .ecindex IIDcyrauth1
23808 .ecindex IIDcyrauth2
23809
23810
23811
23812
23813 . ////////////////////////////////////////////////////////////////////////////
23814 . ////////////////////////////////////////////////////////////////////////////
23815 .chapter "The dovecot authenticator" "CHAPdovecot"
23816 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
23817 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
23818 This authenticator is an interface to the authentication facility of the
23819 Dovecot POP/IMAP server, which can support a number of authentication methods.
23820 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
23821 to use the same mechanisms for SMTP authentication. This is a server
23822 authenticator only. There is only one option:
23823
23824 .option server_socket dovecot string unset
23825
23826 This option must specify the socket that is the interface to Dovecot
23827 authentication. The &%public_name%& option must specify an authentication
23828 mechanism that Dovecot is configured to support. You can have several
23829 authenticators for different mechanisms. For example:
23830 .code
23831 dovecot_plain:
23832 driver = dovecot
23833 public_name = PLAIN
23834 server_socket = /var/run/dovecot/auth-client
23835 server_set_id = $auth1
23836
23837 dovecot_ntlm:
23838 driver = dovecot
23839 public_name = NTLM
23840 server_socket = /var/run/dovecot/auth-client
23841 server_set_id = $auth1
23842 .endd
23843 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
23844 &$received_ip_address$& (that is, the connection is local), the &"secured"&
23845 option is passed in the Dovecot authentication command. If, for a TLS
23846 connection, a client certificate has been verified, the &"valid-client-cert"&
23847 option is passed. When authentication succeeds, the identity of the user
23848 who authenticated is placed in &$auth1$&.
23849 .ecindex IIDdcotauth1
23850 .ecindex IIDdcotauth2
23851
23852
23853 . ////////////////////////////////////////////////////////////////////////////
23854 . ////////////////////////////////////////////////////////////////////////////
23855
23856 .chapter "The spa authenticator" "CHAPspa"
23857 .scindex IIDspaauth1 "&(spa)& authenticator"
23858 .scindex IIDspaauth2 "authenticators" "&(spa)&"
23859 .cindex "authentication" "Microsoft Secure Password"
23860 .cindex "authentication" "NTLM"
23861 .cindex "Microsoft Secure Password Authentication"
23862 .cindex "NTLM authentication"
23863 The &(spa)& authenticator provides client support for Microsoft's &'Secure
23864 Password Authentication'& mechanism,
23865 which is also sometimes known as NTLM (NT LanMan). The code for client side of
23866 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
23867 taken from the Samba project (&url(http://www.samba.org)). The code for the
23868 server side was subsequently contributed by Tom Kistner. The mechanism works as
23869 follows:
23870
23871 .ilist
23872 After the AUTH command has been accepted, the client sends an SPA
23873 authentication request based on the user name and optional domain.
23874 .next
23875 The server sends back a challenge.
23876 .next
23877 The client builds a challenge response which makes use of the user's password
23878 and sends it to the server, which then accepts or rejects it.
23879 .endlist
23880
23881 Encryption is used to protect the password in transit.
23882
23883
23884
23885 .section "Using spa as a server" "SECID179"
23886 .cindex "options" "&(spa)& authenticator (server)"
23887 The &(spa)& authenticator has just one server option:
23888
23889 .option server_password spa string&!! unset
23890 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
23891 This option is expanded, and the result must be the cleartext password for the
23892 authenticating user, whose name is at this point in &$auth1$&. For
23893 compatibility with previous releases of Exim, the user name is also placed in
23894 &$1$&. However, the use of this variable for this purpose is now deprecated, as
23895 it can lead to confusion in string expansions that also use numeric variables
23896 for other things. For example:
23897 .code
23898 spa:
23899 driver = spa
23900 public_name = NTLM
23901 server_password = \
23902 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
23903 .endd
23904 If the expansion is forced to fail, authentication fails. Any other expansion
23905 failure causes a temporary error code to be returned.
23906
23907
23908
23909
23910
23911 .section "Using spa as a client" "SECID180"
23912 .cindex "options" "&(spa)& authenticator (client)"
23913 The &(spa)& authenticator has the following client options:
23914
23915
23916
23917 .option client_domain spa string&!! unset
23918 This option specifies an optional domain for the authentication.
23919
23920
23921 .option client_password spa string&!! unset
23922 This option specifies the user's password, and must be set.
23923
23924
23925 .option client_username spa string&!! unset
23926 This option specifies the user name, and must be set. Here is an example of a
23927 configuration of this authenticator for use with the mail servers at
23928 &'msn.com'&:
23929 .code
23930 msn:
23931 driver = spa
23932 public_name = MSN
23933 client_username = msn/msn_username
23934 client_password = msn_plaintext_password
23935 client_domain = DOMAIN_OR_UNSET
23936 .endd
23937 .ecindex IIDspaauth1
23938 .ecindex IIDspaauth2
23939
23940
23941
23942
23943
23944 . ////////////////////////////////////////////////////////////////////////////
23945 . ////////////////////////////////////////////////////////////////////////////
23946
23947 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
23948 "Encrypted SMTP connections"
23949 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
23950 .scindex IIDencsmtp2 "SMTP" "encryption"
23951 .cindex "TLS" "on SMTP connection"
23952 .cindex "OpenSSL"
23953 .cindex "GnuTLS"
23954 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
23955 Sockets Layer), is implemented by making use of the OpenSSL library or the
23956 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
23957 cryptographic code in the Exim distribution itself for implementing TLS. In
23958 order to use this feature you must install OpenSSL or GnuTLS, and then build a
23959 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
23960 You also need to understand the basic concepts of encryption at a managerial
23961 level, and in particular, the way that public keys, private keys, and
23962 certificates are used.
23963
23964 RFC 3207 defines how SMTP connections can make use of encryption. Once a
23965 connection is established, the client issues a STARTTLS command. If the
23966 server accepts this, the client and the server negotiate an encryption
23967 mechanism. If the negotiation succeeds, the data that subsequently passes
23968 between them is encrypted.
23969
23970 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
23971 and if so, what cipher suite is in use, whether the client supplied a
23972 certificate, and whether or not that certificate was verified. This makes it
23973 possible for an Exim server to deny or accept certain commands based on the
23974 encryption state.
23975
23976 &*Warning*&: Certain types of firewall and certain anti-virus products can
23977 disrupt TLS connections. You need to turn off SMTP scanning for these products
23978 in order to get TLS to work.
23979
23980
23981
23982 .section "Support for the legacy &""ssmtp""& (aka &""smtps""&) protocol" &&&
23983 "SECID284"
23984 .cindex "ssmtp protocol"
23985 .cindex "smtps protocol"
23986 .cindex "SMTP" "ssmtp protocol"
23987 .cindex "SMTP" "smtps protocol"
23988 Early implementations of encrypted SMTP used a different TCP port from normal
23989 SMTP, and expected an encryption negotiation to start immediately, instead of
23990 waiting for a STARTTLS command from the client using the standard SMTP
23991 port. The protocol was called &"ssmtp"& or &"smtps"&, and port 465 was
23992 allocated for this purpose.
23993
23994 This approach was abandoned when encrypted SMTP was standardized, but there are
23995 still some legacy clients that use it. Exim supports these clients by means of
23996 the &%tls_on_connect_ports%& global option. Its value must be a list of port
23997 numbers; the most common use is expected to be:
23998 .code
23999 tls_on_connect_ports = 465
24000 .endd
24001 The port numbers specified by this option apply to all SMTP connections, both
24002 via the daemon and via &'inetd'&. You still need to specify all the ports that
24003 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
24004 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
24005 an extra port &-- rather, it specifies different behaviour on a port that is
24006 defined elsewhere.
24007
24008 There is also a &%-tls-on-connect%& command line option. This overrides
24009 &%tls_on_connect_ports%&; it forces the legacy behaviour for all ports.
24010
24011
24012
24013
24014
24015
24016 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
24017 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
24018 The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
24019 followed later, when the first versions of GnuTLS were released. To build Exim
24020 to use GnuTLS, you need to set
24021 .code
24022 USE_GNUTLS=yes
24023 .endd
24024 in Local/Makefile, in addition to
24025 .code
24026 SUPPORT_TLS=yes
24027 .endd
24028 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
24029 include files and libraries for GnuTLS can be found.
24030
24031 There are some differences in usage when using GnuTLS instead of OpenSSL:
24032
24033 .ilist
24034 The &%tls_verify_certificates%& option must contain the name of a file, not the
24035 name of a directory (for OpenSSL it can be either).
24036 .next
24037 The &%tls_dhparam%& option is ignored, because early versions of GnuTLS had no
24038 facility for varying its Diffie-Hellman parameters. I understand that this has
24039 changed, but Exim has not been updated to provide this facility.
24040 .next
24041 .vindex "&$tls_peerdn$&"
24042 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
24043 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
24044 affects the value of the &$tls_peerdn$& variable.
24045 .next
24046 OpenSSL identifies cipher suites using hyphens as separators, for example:
24047 DES-CBC3-SHA. GnuTLS uses underscores, for example: RSA_ARCFOUR_SHA. What is
24048 more, OpenSSL complains if underscores are present in a cipher list. To make
24049 life simpler, Exim changes underscores to hyphens for OpenSSL and hyphens to
24050 underscores for GnuTLS when processing lists of cipher suites in the
24051 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
24052 option).
24053 .next
24054 The &%tls_require_ciphers%& options operate differently, as described in the
24055 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
24056 .endlist
24057
24058
24059 .section "GnuTLS parameter computation" "SECID181"
24060 GnuTLS uses RSA and D-H parameters that may take a substantial amount of time
24061 to compute. It is unreasonable to re-compute them for every TLS session.
24062 Therefore, Exim keeps this data in a file in its spool directory, called
24063 &_gnutls-params_&. The file is owned by the Exim user and is readable only by
24064 its owner. Every Exim process that start up GnuTLS reads the RSA and D-H
24065 parameters from this file. If the file does not exist, the first Exim process
24066 that needs it computes the data and writes it to a temporary file which is
24067 renamed once it is complete. It does not matter if several Exim processes do
24068 this simultaneously (apart from wasting a few resources). Once a file is in
24069 place, new Exim processes immediately start using it.
24070
24071 For maximum security, the parameters that are stored in this file should be
24072 recalculated periodically, the frequency depending on your paranoia level.
24073 Arranging this is easy in principle; just delete the file when you want new
24074 values to be computed. However, there may be a problem. The calculation of new
24075 parameters needs random numbers, and these are obtained from &_/dev/random_&.
24076 If the system is not very active, &_/dev/random_& may delay returning data
24077 until enough randomness (entropy) is available. This may cause Exim to hang for
24078 a substantial amount of time, causing timeouts on incoming connections.
24079
24080 The solution is to generate the parameters externally to Exim. They are stored
24081 in &_gnutls-params_& in PEM format, which means that they can be generated
24082 externally using the &(certtool)& command that is part of GnuTLS.
24083
24084 To replace the parameters with new ones, instead of deleting the file
24085 and letting Exim re-create it, you can generate new parameters using
24086 &(certtool)& and, when this has been done, replace Exim's cache file by
24087 renaming. The relevant commands are something like this:
24088 .code
24089 # rm -f new-params
24090 # touch new-params
24091 # chown exim:exim new-params
24092 # chmod 0400 new-params
24093 # certtool --generate-privkey --bits 512 >new-params
24094 # echo "" >>new-params
24095 # certtool --generate-dh-params --bits 1024 >> new-params
24096 # mv new-params gnutls-params
24097 .endd
24098 If Exim never has to generate the parameters itself, the possibility of
24099 stalling is removed.
24100
24101
24102 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
24103 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
24104 .oindex "&%tls_require_ciphers%&" "OpenSSL"
24105 There is a function in the OpenSSL library that can be passed a list of cipher
24106 suites before the cipher negotiation takes place. This specifies which ciphers
24107 are acceptable. The list is colon separated and may contain names like
24108 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
24109 directly to this function call. The following quotation from the OpenSSL
24110 documentation specifies what forms of item are allowed in the cipher string:
24111
24112 .ilist
24113 It can consist of a single cipher suite such as RC4-SHA.
24114 .next
24115 It can represent a list of cipher suites containing a certain algorithm,
24116 or cipher suites of a certain type. For example SHA1 represents all
24117 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
24118 SSL v3 algorithms.
24119 .next
24120 Lists of cipher suites can be combined in a single cipher string using
24121 the + character. This is used as a logical and operation. For example
24122 SHA1+DES represents all cipher suites containing the SHA1 and the DES
24123 algorithms.
24124 .endlist
24125
24126 Each cipher string can be optionally preceded by one of the characters &`!`&,
24127 &`-`& or &`+`&.
24128 .ilist
24129 If &`!`& is used, the ciphers are permanently deleted from the list. The
24130 ciphers deleted can never reappear in the list even if they are explicitly
24131 stated.
24132 .next
24133 If &`-`& is used, the ciphers are deleted from the list, but some or all
24134 of the ciphers can be added again by later options.
24135 .next
24136 If &`+`& is used, the ciphers are moved to the end of the list. This
24137 option does not add any new ciphers; it just moves matching existing ones.
24138 .endlist
24139
24140 If none of these characters is present, the string is interpreted as
24141 a list of ciphers to be appended to the current preference list. If the list
24142 includes any ciphers already present they will be ignored: that is, they will
24143 not be moved to the end of the list.
24144 .endlist
24145
24146
24147
24148 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
24149 "SECTreqciphgnu"
24150 .cindex "GnuTLS" "specifying parameters for"
24151 .cindex "TLS" "specifying ciphers (GnuTLS)"
24152 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
24153 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
24154 .cindex "TLS" "specifying protocols (GnuTLS)"
24155 .oindex "&%tls_require_ciphers%&" "GnuTLS"
24156 The GnuTLS library allows the caller to specify separate lists of permitted key
24157 exchange methods, main cipher algorithms, MAC algorithms, and protocols.
24158 Unfortunately, these lists are numerical, and the library does not have a
24159 function for turning names into numbers. Consequently, lists of recognized
24160 names have to be built into the application. The permitted key exchange
24161 methods, ciphers, and MAC algorithms may be used in any combination to form a
24162 cipher suite. This is unlike OpenSSL, where complete cipher suite names are
24163 passed to its control function.
24164
24165 For compatibility with OpenSSL, the &%tls_require_ciphers%& option can be set
24166 to complete cipher suite names such as RSA_ARCFOUR_SHA, but for GnuTLS this
24167 option controls only the cipher algorithms. Exim searches each item in the
24168 list for the name of an available algorithm. For example, if the list
24169 contains RSA_AES_SHA, then AES is recognized, and the behaviour is exactly
24170 the same as if just AES were given.
24171
24172 .oindex "&%gnutls_require_kx%&"
24173 .oindex "&%gnutls_require_mac%&"
24174 .oindex "&%gnutls_require_protocols%&"
24175 There are additional options called &%gnutls_require_kx%&,
24176 &%gnutls_require_mac%&, and &%gnutls_require_protocols%& that can be used to
24177 restrict the key exchange methods, MAC algorithms, and protocols, respectively.
24178 These options are ignored if OpenSSL is in use.
24179
24180 All four options are available as global options, controlling how Exim
24181 behaves as a server, and also as options of the &(smtp)& transport, controlling
24182 how Exim behaves as a client. All the values are string expanded. After
24183 expansion, the values must be colon-separated lists, though the separator
24184 can be changed in the usual way.
24185
24186 Each of the four lists starts out with a default set of algorithms. If the
24187 first item in a list does &'not'& start with an exclamation mark, all the
24188 default items are deleted. In this case, only those that are explicitly
24189 specified can be used. If the first item in a list &'does'& start with an
24190 exclamation mark, the defaults are left on the list.
24191
24192 Then, any item that starts with an exclamation mark causes the relevant
24193 entry to be removed from the list, and any item that does not start with an
24194 exclamation mark causes a new entry to be added to the list. Unrecognized
24195 items in the list are ignored. Thus:
24196 .code
24197 tls_require_ciphers = !ARCFOUR
24198 .endd
24199 allows all the defaults except ARCFOUR, whereas
24200 .code
24201 tls_require_ciphers = AES : 3DES
24202 .endd
24203 allows only cipher suites that use AES or 3DES.
24204
24205 For &%tls_require_ciphers%& the recognized names are AES_256, AES_128, AES
24206 (both of the preceding), 3DES, ARCFOUR_128, ARCFOUR_40, and ARCFOUR (both of
24207 the preceding). The default list does not contain all of these; it just has
24208 AES_256, AES_128, 3DES, and ARCFOUR_128.
24209
24210 For &%gnutls_require_kx%&, the recognized names are DHE_RSA, RSA (which
24211 includes DHE_RSA), DHE_DSS, and DHE (which includes both DHE_RSA and
24212 DHE_DSS). The default list contains RSA, DHE_DSS, DHE_RSA.
24213
24214 For &%gnutls_require_mac%&, the recognized names are SHA (synonym SHA1), and
24215 MD5. The default list contains SHA, MD5.
24216
24217 For &%gnutls_require_protocols%&, the recognized names are TLS1 and SSL3.
24218 The default list contains TLS1, SSL3.
24219
24220 In a server, the order of items in these lists is unimportant. The server
24221 advertises the availability of all the relevant cipher suites. However, in a
24222 client, the order in the &%tls_require_ciphers%& list specifies a preference
24223 order for the cipher algorithms. The first one in the client's list that is
24224 also advertised by the server is tried first. The default order is as listed
24225 above.
24226
24227
24228
24229 .section "Configuring an Exim server to use TLS" "SECID182"
24230 .cindex "TLS" "configuring an Exim server"
24231 When Exim has been built with TLS support, it advertises the availability of
24232 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
24233 but not to any others. The default value of this option is unset, which means
24234 that STARTTLS is not advertised at all. This default is chosen because you
24235 need to set some other options in order to make TLS available, and also it is
24236 sensible for systems that want to use TLS only as a client.
24237
24238 If a client issues a STARTTLS command and there is some configuration
24239 problem in the server, the command is rejected with a 454 error. If the client
24240 persists in trying to issue SMTP commands, all except QUIT are rejected
24241 with the error
24242 .code
24243 554 Security failure
24244 .endd
24245 If a STARTTLS command is issued within an existing TLS session, it is
24246 rejected with a 554 error code.
24247
24248 To enable TLS operations on a server, you must set &%tls_advertise_hosts%& to
24249 match some hosts. You can, of course, set it to * to match all hosts.
24250 However, this is not all you need to do. TLS sessions to a server won't work
24251 without some further configuration at the server end.
24252
24253 It is rumoured that all existing clients that support TLS/SSL use RSA
24254 encryption. To make this work you need to set, in the server,
24255 .code
24256 tls_certificate = /some/file/name
24257 tls_privatekey = /some/file/name
24258 .endd
24259 These options are, in fact, expanded strings, so you can make them depend on
24260 the identity of the client that is connected if you wish. The first file
24261 contains the server's X509 certificate, and the second contains the private key
24262 that goes with it. These files need to be readable by the Exim user, and must
24263 always be given as full path names. They can be the same file if both the
24264 certificate and the key are contained within it. If &%tls_privatekey%& is not
24265 set, or if its expansion is forced to fail or results in an empty string, this
24266 is assumed to be the case. The certificate file may also contain intermediate
24267 certificates that need to be sent to the client to enable it to authenticate
24268 the server's certificate.
24269
24270 If you do not understand about certificates and keys, please try to find a
24271 source of this background information, which is not Exim-specific. (There are a
24272 few comments below in section &<<SECTcerandall>>&.)
24273
24274 &*Note*&: These options do not apply when Exim is operating as a client &--
24275 they apply only in the case of a server. If you need to use a certificate in an
24276 Exim client, you must set the options of the same names in an &(smtp)&
24277 transport.
24278
24279 With just these options, an Exim server will be able to use TLS. It does not
24280 require the client to have a certificate (but see below for how to insist on
24281 this). There is one other option that may be needed in other situations. If
24282 .code
24283 tls_dhparam = /some/file/name
24284 .endd
24285 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
24286 with the parameters contained in the file. This increases the set of cipher
24287 suites that the server supports. See the command
24288 .code
24289 openssl dhparam
24290 .endd
24291 for a way of generating this data. At present, &%tls_dhparam%& is used only
24292 when Exim is linked with OpenSSL. It is ignored if GnuTLS is being used.
24293
24294 The strings supplied for these three options are expanded every time a client
24295 host connects. It is therefore possible to use different certificates and keys
24296 for different hosts, if you so wish, by making use of the client's IP address
24297 in &$sender_host_address$& to control the expansion. If a string expansion is
24298 forced to fail, Exim behaves as if the option is not set.
24299
24300 .cindex "cipher" "logging"
24301 .cindex "log" "TLS cipher"
24302 .vindex "&$tls_cipher$&"
24303 The variable &$tls_cipher$& is set to the cipher suite that was negotiated for
24304 an incoming TLS connection. It is included in the &'Received:'& header of an
24305 incoming message (by default &-- you can, of course, change this), and it is
24306 also included in the log line that records a message's arrival, keyed by
24307 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
24308 condition can be used to test for specific cipher suites in ACLs.
24309 (For outgoing SMTP deliveries, &$tls_cipher$& is reset &-- see section
24310 &<<SECID185>>&.)
24311
24312 Once TLS has been established, the ACLs that run for subsequent SMTP commands
24313 can check the name of the cipher suite and vary their actions accordingly. The
24314 cipher suite names vary, depending on which TLS library is being used. For
24315 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
24316 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
24317 documentation for more details.
24318
24319
24320 .section "Requesting and verifying client certificates" "SECID183"
24321 .cindex "certificate" "verification of client"
24322 .cindex "TLS" "client certificate verification"
24323 If you want an Exim server to request a certificate when negotiating a TLS
24324 session with a client, you must set either &%tls_verify_hosts%& or
24325 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
24326 apply to all TLS connections. For any host that matches one of these options,
24327 Exim requests a certificate as part of the setup of the TLS session. The
24328 contents of the certificate are verified by comparing it with a list of
24329 expected certificates. These must be available in a file or,
24330 for OpenSSL only (not GnuTLS), a directory, identified by
24331 &%tls_verify_certificates%&.
24332
24333 A file can contain multiple certificates, concatenated end to end. If a
24334 directory is used
24335 (OpenSSL only),
24336 each certificate must be in a separate file, with a name (or a symbolic link)
24337 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
24338 certificate. You can compute the relevant hash by running the command
24339 .code
24340 openssl x509 -hash -noout -in /cert/file
24341 .endd
24342 where &_/cert/file_& contains a single certificate.
24343
24344 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
24345 what happens if the client does not supply a certificate, or if the certificate
24346 does not match any of the certificates in the collection named by
24347 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
24348 attempt to set up a TLS session is aborted, and the incoming connection is
24349 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
24350 session continues. ACLs that run for subsequent SMTP commands can detect the
24351 fact that no certificate was verified, and vary their actions accordingly. For
24352 example, you can insist on a certificate before accepting a message for
24353 relaying, but not when the message is destined for local delivery.
24354
24355 .vindex "&$tls_peerdn$&"
24356 When a client supplies a certificate (whether it verifies or not), the value of
24357 the Distinguished Name of the certificate is made available in the variable
24358 &$tls_peerdn$& during subsequent processing of the message.
24359
24360 .cindex "log" "distinguished name"
24361 Because it is often a long text string, it is not included in the log line or
24362 &'Received:'& header by default. You can arrange for it to be logged, keyed by
24363 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
24364 &%received_header_text%& to change the &'Received:'& header. When no
24365 certificate is supplied, &$tls_peerdn$& is empty.
24366
24367
24368 .section "Revoked certificates" "SECID184"
24369 .cindex "TLS" "revoked certificates"
24370 .cindex "revocation list"
24371 .cindex "certificate" "revocation list"
24372 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
24373 certificates are revoked. If you have such a list, you can pass it to an Exim
24374 server using the global option called &%tls_crl%& and to an Exim client using
24375 an identically named option for the &(smtp)& transport. In each case, the value
24376 of the option is expanded and must then be the name of a file that contains a
24377 CRL in PEM format.
24378
24379
24380 .section "Configuring an Exim client to use TLS" "SECID185"
24381 .cindex "cipher" "logging"
24382 .cindex "log" "TLS cipher"
24383 .cindex "log" "distinguished name"
24384 .cindex "TLS" "configuring an Exim client"
24385 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
24386 deliveries as well as to incoming, the latter one causing logging of the
24387 server certificate's DN. The remaining client configuration for TLS is all
24388 within the &(smtp)& transport.
24389
24390 It is not necessary to set any options to have TLS work in the &(smtp)&
24391 transport. If Exim is built with TLS support, and TLS is advertised by a
24392 server, the &(smtp)& transport always tries to start a TLS session. However,
24393 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
24394 transport) to a list of server hosts for which TLS should not be used.
24395
24396 If you do not want Exim to attempt to send messages unencrypted when an attempt
24397 to set up an encrypted connection fails in any way, you can set
24398 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
24399 those hosts, delivery is always deferred if an encrypted connection cannot be
24400 set up. If there are any other hosts for the address, they are tried in the
24401 usual way.
24402
24403 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
24404 the message unencrypted. It always does this if the response to STARTTLS is
24405 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
24406 session after a success response code, what happens is controlled by the
24407 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
24408 delivery to this host is deferred, and other hosts (if available) are tried. If
24409 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
24410 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
24411 negotiation fails, Exim closes the current connection (because it is in an
24412 unknown state), opens a new one to the same host, and then tries the delivery
24413 unencrypted.
24414
24415 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
24416 transport provide the client with a certificate, which is passed to the server
24417 if it requests it. If the server is Exim, it will request a certificate only if
24418 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client. &*Note*&:
24419 These options must be set in the &(smtp)& transport for Exim to use TLS when it
24420 is operating as a client. Exim does not assume that a server certificate (set
24421 by the global options of the same name) should also be used when operating as a
24422 client.
24423
24424 If &%tls_verify_certificates%& is set, it must name a file or,
24425 for OpenSSL only (not GnuTLS), a directory, that contains a collection of
24426 expected server certificates. The client verifies the server's certificate
24427 against this collection, taking into account any revoked certificates that are
24428 in the list defined by &%tls_crl%&.
24429
24430 If
24431 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
24432 list of permitted cipher suites. If either of these checks fails, delivery to
24433 the current host is abandoned, and the &(smtp)& transport tries to deliver to
24434 alternative hosts, if any.
24435
24436 .vindex "&$host$&"
24437 .vindex "&$host_address$&"
24438 All the TLS options in the &(smtp)& transport are expanded before use, with
24439 &$host$& and &$host_address$& containing the name and address of the server to
24440 which the client is connected. Forced failure of an expansion causes Exim to
24441 behave as if the relevant option were unset.
24442
24443 .vindex &$tls_cipher$&
24444 .vindex &$tls_peerdn$&
24445 Before an SMTP connection is established, the &$tls_cipher$& and &$tls_peerdn$&
24446 variables are emptied. (Until the first connection, they contain the values
24447 that were set when the message was received.) If STARTTLS is subsequently
24448 successfully obeyed, these variables are set to the relevant values for the
24449 outgoing connection.
24450
24451
24452
24453 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
24454 "SECTmulmessam"
24455 .cindex "multiple SMTP deliveries with TLS"
24456 .cindex "TLS" "multiple message deliveries"
24457 Exim sends multiple messages down the same TCP/IP connection by starting up
24458 an entirely new delivery process for each message, passing the socket from
24459 one process to the next. This implementation does not fit well with the use
24460 of TLS, because there is quite a lot of state information associated with a TLS
24461 connection, not just a socket identification. Passing all the state information
24462 to a new process is not feasible. Consequently, Exim shuts down an existing TLS
24463 session before passing the socket to a new process. The new process may then
24464 try to start a new TLS session, and if successful, may try to re-authenticate
24465 if AUTH is in use, before sending the next message.
24466
24467 The RFC is not clear as to whether or not an SMTP session continues in clear
24468 after TLS has been shut down, or whether TLS may be restarted again later, as
24469 just described. However, if the server is Exim, this shutdown and
24470 reinitialization works. It is not known which (if any) other servers operate
24471 successfully if the client closes a TLS session and continues with unencrypted
24472 SMTP, but there are certainly some that do not work. For such servers, Exim
24473 should not pass the socket to another process, because the failure of the
24474 subsequent attempt to use it would cause Exim to record a temporary host error,
24475 and delay other deliveries to that host.
24476
24477 To test for this case, Exim sends an EHLO command to the server after
24478 closing down the TLS session. If this fails in any way, the connection is
24479 closed instead of being passed to a new delivery process, but no retry
24480 information is recorded.
24481
24482 There is also a manual override; you can set &%hosts_nopass_tls%& on the
24483 &(smtp)& transport to match those hosts for which Exim should not pass
24484 connections to new processes if TLS has been used.
24485
24486
24487
24488
24489 .section "Certificates and all that" "SECTcerandall"
24490 .cindex "certificate" "references to discussion"
24491 In order to understand fully how TLS works, you need to know about
24492 certificates, certificate signing, and certificate authorities. This is not the
24493 place to give a tutorial, especially as I do not know very much about it
24494 myself. Some helpful introduction can be found in the FAQ for the SSL addition
24495 to Apache, currently at
24496 .display
24497 &url(http://www.modssl.org/docs/2.7/ssl_faq.html#ToC24)
24498 .endd
24499 Other parts of the &'modssl'& documentation are also helpful, and have
24500 links to further files.
24501 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
24502 0-201-61598-3), contains both introductory and more in-depth descriptions.
24503 Some sample programs taken from the book are available from
24504 .display
24505 &url(http://www.rtfm.com/openssl-examples/)
24506 .endd
24507
24508
24509 .section "Certificate chains" "SECID186"
24510 The file named by &%tls_certificate%& may contain more than one
24511 certificate. This is useful in the case where the certificate that is being
24512 sent is validated by an intermediate certificate which the other end does
24513 not have. Multiple certificates must be in the correct order in the file.
24514 First the host's certificate itself, then the first intermediate
24515 certificate to validate the issuer of the host certificate, then the next
24516 intermediate certificate to validate the issuer of the first intermediate
24517 certificate, and so on, until finally (optionally) the root certificate.
24518 The root certificate must already be trusted by the recipient for
24519 validation to succeed, of course, but if it's not preinstalled, sending the
24520 root certificate along with the rest makes it available for the user to
24521 install if the receiving end is a client MUA that can interact with a user.
24522
24523
24524 .section "Self-signed certificates" "SECID187"
24525 .cindex "certificate" "self-signed"
24526 You can create a self-signed certificate using the &'req'& command provided
24527 with OpenSSL, like this:
24528 .code
24529 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
24530 -days 9999 -nodes
24531 .endd
24532 &_file1_& and &_file2_& can be the same file; the key and the certificate are
24533 delimited and so can be identified independently. The &%-days%& option
24534 specifies a period for which the certificate is valid. The &%-nodes%& option is
24535 important: if you do not set it, the key is encrypted with a passphrase
24536 that you are prompted for, and any use that is made of the key causes more
24537 prompting for the passphrase. This is not helpful if you are going to use
24538 this certificate and key in an MTA, where prompting is not possible.
24539
24540 A self-signed certificate made in this way is sufficient for testing, and
24541 may be adequate for all your requirements if you are mainly interested in
24542 encrypting transfers, and not in secure identification.
24543
24544 However, many clients require that the certificate presented by the server be a
24545 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
24546 certificate. In this situation, the self-signed certificate described above
24547 must be installed on the client host as a trusted root &'certification
24548 authority'& (CA), and the certificate used by Exim must be a user certificate
24549 signed with that self-signed certificate.
24550
24551 For information on creating self-signed CA certificates and using them to sign
24552 user certificates, see the &'General implementation overview'& chapter of the
24553 Open-source PKI book, available online at
24554 &url(http://ospkibook.sourceforge.net/).
24555 .ecindex IIDencsmtp1
24556 .ecindex IIDencsmtp2
24557
24558
24559
24560 . ////////////////////////////////////////////////////////////////////////////
24561 . ////////////////////////////////////////////////////////////////////////////
24562
24563 .chapter "Access control lists" "CHAPACL"
24564 .scindex IIDacl "&ACL;" "description"
24565 .cindex "control of incoming mail"
24566 .cindex "message" "controlling incoming"
24567 .cindex "policy control" "access control lists"
24568 Access Control Lists (ACLs) are defined in a separate section of the run time
24569 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
24570 name, terminated by a colon. Here is a complete ACL section that contains just
24571 one very small ACL:
24572 .code
24573 begin acl
24574 small_acl:
24575 accept hosts = one.host.only
24576 .endd
24577 You can have as many lists as you like in the ACL section, and the order in
24578 which they appear does not matter. The lists are self-terminating.
24579
24580 The majority of ACLs are used to control Exim's behaviour when it receives
24581 certain SMTP commands. This applies both to incoming TCP/IP connections, and
24582 when a local process submits a message using SMTP by specifying the &%-bs%&
24583 option. The most common use is for controlling which recipients are accepted
24584 in incoming messages. In addition, you can define an ACL that is used to check
24585 local non-SMTP messages. The default configuration file contains an example of
24586 a realistic ACL for checking RCPT commands. This is discussed in chapter
24587 &<<CHAPdefconfil>>&.
24588
24589
24590 .section "Testing ACLs" "SECID188"
24591 The &%-bh%& command line option provides a way of testing your ACL
24592 configuration locally by running a fake SMTP session with which you interact.
24593 The host &'relay-test.mail-abuse.org'& provides a service for checking your
24594 relaying configuration (see section &<<SECTcheralcon>>& for more details).
24595
24596
24597
24598 .section "Specifying when ACLs are used" "SECID189"
24599 .cindex "&ACL;" "options for specifying"
24600 In order to cause an ACL to be used, you have to name it in one of the relevant
24601 options in the main part of the configuration. These options are:
24602 .cindex "AUTH" "ACL for"
24603 .cindex "DATA" "ACLs for"
24604 .cindex "ETRN" "ACL for"
24605 .cindex "EXPN" "ACL for"
24606 .cindex "HELO" "ACL for"
24607 .cindex "EHLO" "ACL for"
24608 .cindex "MAIL" "ACL for"
24609 .cindex "QUIT, ACL for"
24610 .cindex "RCPT" "ACL for"
24611 .cindex "STARTTLS, ACL for"
24612 .cindex "VRFY" "ACL for"
24613 .cindex "SMTP" "connection, ACL for"
24614 .cindex "non-SMTP messages" "ACLs for"
24615 .cindex "MIME content scanning" "ACL for"
24616
24617 .table2 140pt
24618 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
24619 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
24620 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
24621 .irow &%acl_smtp_auth%& "ACL for AUTH"
24622 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
24623 .irow &%acl_smtp_data%& "ACL after DATA is complete"
24624 .irow &%acl_smtp_etrn%& "ACL for ETRN"
24625 .irow &%acl_smtp_expn%& "ACL for EXPN"
24626 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
24627 .irow &%acl_smtp_mail%& "ACL for MAIL"
24628 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
24629 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
24630 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
24631 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
24632 .irow &%acl_smtp_quit%& "ACL for QUIT"
24633 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
24634 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
24635 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
24636 .endtable
24637
24638 For example, if you set
24639 .code
24640 acl_smtp_rcpt = small_acl
24641 .endd
24642 the little ACL defined above is used whenever Exim receives a RCPT command
24643 in an SMTP dialogue. The majority of policy tests on incoming messages can be
24644 done when RCPT commands arrive. A rejection of RCPT should cause the
24645 sending MTA to give up on the recipient address contained in the RCPT
24646 command, whereas rejection at other times may cause the client MTA to keep on
24647 trying to deliver the message. It is therefore recommended that you do as much
24648 testing as possible at RCPT time.
24649
24650
24651 .section "The non-SMTP ACLs" "SECID190"
24652 .cindex "non-SMTP messages" "ACLs for"
24653 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
24654 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
24655 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
24656 the state of the SMTP connection such as encryption and authentication) are not
24657 relevant and are forbidden in these ACLs. However, the sender and recipients
24658 are known, so the &%senders%& and &%sender_domains%& conditions and the
24659 &$sender_address$& and &$recipients$& variables can be used. Variables such as
24660 &$authenticated_sender$& are also available. You can specify added header lines
24661 in any of these ACLs.
24662
24663 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
24664 non-SMTP message, before any of the message has been read. (This is the
24665 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
24666 batched SMTP input, it runs after the DATA command has been reached. The
24667 result of this ACL is ignored; it cannot be used to reject a message. If you
24668 really need to, you could set a value in an ACL variable here and reject based
24669 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
24670 controls, and in particular, it can be used to set
24671 .code
24672 control = suppress_local_fixups
24673 .endd
24674 This cannot be used in the other non-SMTP ACLs because by the time they are
24675 run, it is too late.
24676
24677 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
24678 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
24679
24680 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
24681 kind of rejection is treated as permanent, because there is no way of sending a
24682 temporary error for these kinds of message.
24683
24684
24685 .section "The SMTP connect ACL" "SECID191"
24686 .cindex "SMTP" "connection, ACL for"
24687 .oindex &%smtp_banner%&
24688 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
24689 session, after the test specified by &%host_reject_connection%& (which is now
24690 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
24691 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
24692 the message override the banner message that is otherwise specified by the
24693 &%smtp_banner%& option.
24694
24695
24696 .section "The EHLO/HELO ACL" "SECID192"
24697 .cindex "EHLO" "ACL for"
24698 .cindex "HELO" "ACL for"
24699 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
24700 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
24701 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
24702 Note that a client may issue more than one EHLO or HELO command in an SMTP
24703 session, and indeed is required to issue a new EHLO or HELO after successfully
24704 setting up encryption following a STARTTLS command.
24705
24706 If the command is accepted by an &%accept%& verb that has a &%message%&
24707 modifier, the message may not contain more than one line (it will be truncated
24708 at the first newline and a panic logged if it does). Such a message cannot
24709 affect the EHLO options that are listed on the second and subsequent lines of
24710 an EHLO response.
24711
24712
24713 .section "The DATA ACLs" "SECID193"
24714 .cindex "DATA" "ACLs for"
24715 Two ACLs are associated with the DATA command, because it is two-stage
24716 command, with two responses being sent to the client.
24717 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
24718 is obeyed. This gives you control after all the RCPT commands, but before
24719 the message itself is received. It offers the opportunity to give a negative
24720 response to the DATA command before the data is transmitted. Header lines
24721 added by MAIL or RCPT ACLs are not visible at this time, but any that
24722 are defined here are visible when the &%acl_smtp_data%& ACL is run.
24723
24724 You cannot test the contents of the message, for example, to verify addresses
24725 in the headers, at RCPT time or when the DATA command is received. Such
24726 tests have to appear in the ACL that is run after the message itself has been
24727 received, before the final response to the DATA command is sent. This is
24728 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
24729 associated with the DATA command.
24730
24731 For both of these ACLs, it is not possible to reject individual recipients. An
24732 error response rejects the entire message. Unfortunately, it is known that some
24733 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
24734 before or after the data) correctly &-- they keep the message on their queues
24735 and try again later, but that is their problem, though it does waste some of
24736 your resources.
24737
24738
24739 .section "The SMTP MIME ACL" "SECID194"
24740 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
24741 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
24742
24743
24744 .section "The QUIT ACL" "SECTQUITACL"
24745 .cindex "QUIT, ACL for"
24746 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
24747 does not affect the response code to QUIT, which is always 221. Thus, the ACL
24748 does not in fact control any access. For this reason, the only verbs that are
24749 permitted are &%accept%& and &%warn%&.
24750
24751 This ACL can be used for tasks such as custom logging at the end of an SMTP
24752 session. For example, you can use ACL variables in other ACLs to count
24753 messages, recipients, etc., and log the totals at QUIT time using one or
24754 more &%logwrite%& modifiers on a &%warn%& verb.
24755
24756 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
24757 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
24758
24759 You do not need to have a final &%accept%&, but if you do, you can use a
24760 &%message%& modifier to specify custom text that is sent as part of the 221
24761 response to QUIT.
24762
24763 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
24764 failure (for example, failure to open a log file, or when Exim is bombing out
24765 because it has detected an unrecoverable error), all SMTP commands from the
24766 client are given temporary error responses until QUIT is received or the
24767 connection is closed. In these special cases, the QUIT ACL does not run.
24768
24769
24770
24771 .section "The not-QUIT ACL" "SECTNOTQUITACL"
24772 The not-QUIT ACL, specified by &%smtp_notquit_acl%&, is run in most cases when
24773 an SMTP session ends without sending QUIT. However, when Exim itself is is bad
24774 trouble, such as being unable to write to its log files, this ACL is not run,
24775 because it might try to do things (such as write to log files) that make the
24776 situation even worse.
24777
24778 Like the QUIT ACL, this ACL is provided to make it possible to do customized
24779 logging or to gather statistics, and its outcome is ignored. The &%delay%&
24780 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
24781 and &%warn%&.
24782
24783 .vindex &$smtp_notquit_reason$&
24784 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
24785 to a string that indicates the reason for the termination of the SMTP
24786 connection. The possible values are:
24787 .table2
24788 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
24789 .irow &`bad-commands`& "Too many unknown or non-mail commands"
24790 .irow &`command-timeout`& "Timeout while reading SMTP commands"
24791 .irow &`connection-lost`& "The SMTP connection has been lost"
24792 .irow &`data-timeout`& "Timeout while reading message data"
24793 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
24794 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
24795 .irow &`signal-exit`& "SIGTERM or SIGINT"
24796 .irow &`synchronization-error`& "SMTP synchronization error"
24797 .irow &`tls-failed`& "TLS failed to start"
24798 .endtable
24799 In most cases when an SMTP connection is closed without having received QUIT,
24800 Exim sends an SMTP response message before actually closing the connection.
24801 With the exception of the &`acl-drop`& case, the default message can be
24802 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
24803 &%drop%& verb in another ACL, it is the message from the other ACL that is
24804 used.
24805
24806
24807 .section "Finding an ACL to use" "SECID195"
24808 .cindex "&ACL;" "finding which to use"
24809 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
24810 you can use different ACLs in different circumstances. For example,
24811 .code
24812 acl_smtp_rcpt = ${if ={25}{$interface_port} \
24813 {acl_check_rcpt} {acl_check_rcpt_submit} }
24814 .endd
24815 In the default configuration file there are some example settings for
24816 providing an RFC 4409 message submission service on port 587 and a
24817 non-standard &"smtps"& service on port 465. You can use a string
24818 expansion like this to choose an ACL for MUAs on these ports which is
24819 more appropriate for this purpose than the default ACL on port 25.
24820
24821 The expanded string does not have to be the name of an ACL in the
24822 configuration file; there are other possibilities. Having expanded the
24823 string, Exim searches for an ACL as follows:
24824
24825 .ilist
24826 If the string begins with a slash, Exim uses it as a file name, and reads its
24827 contents as an ACL. The lines are processed in the same way as lines in the
24828 Exim configuration file. In particular, continuation lines are supported, blank
24829 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
24830 If the file does not exist or cannot be read, an error occurs (typically
24831 causing a temporary failure of whatever caused the ACL to be run). For example:
24832 .code
24833 acl_smtp_data = /etc/acls/\
24834 ${lookup{$sender_host_address}lsearch\
24835 {/etc/acllist}{$value}{default}}
24836 .endd
24837 This looks up an ACL file to use on the basis of the host's IP address, falling
24838 back to a default if the lookup fails. If an ACL is successfully read from a
24839 file, it is retained in memory for the duration of the Exim process, so that it
24840 can be re-used without having to re-read the file.
24841 .next
24842 If the string does not start with a slash, and does not contain any spaces,
24843 Exim searches the ACL section of the configuration for an ACL whose name
24844 matches the string.
24845 .next
24846 If no named ACL is found, or if the string contains spaces, Exim parses
24847 the string as an inline ACL. This can save typing in cases where you just
24848 want to have something like
24849 .code
24850 acl_smtp_vrfy = accept
24851 .endd
24852 in order to allow free use of the VRFY command. Such a string may contain
24853 newlines; it is processed in the same way as an ACL that is read from a file.
24854 .endlist
24855
24856
24857
24858
24859 .section "ACL return codes" "SECID196"
24860 .cindex "&ACL;" "return codes"
24861 Except for the QUIT ACL, which does not affect the SMTP return code (see
24862 section &<<SECTQUITACL>>& above), the result of running an ACL is either
24863 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
24864 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
24865 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
24866 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
24867 This also causes a 4&'xx'& return code.
24868
24869 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
24870 &"deny"&, because there is no mechanism for passing temporary errors to the
24871 submitters of non-SMTP messages.
24872
24873
24874 ACLs that are relevant to message reception may also return &"discard"&. This
24875 has the effect of &"accept"&, but causes either the entire message or an
24876 individual recipient address to be discarded. In other words, it is a
24877 blackholing facility. Use it with care.
24878
24879 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
24880 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
24881 RCPT ACL is to discard just the one recipient address. If there are no
24882 recipients left when the message's data is received, the DATA ACL is not
24883 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
24884 remaining recipients. The &"discard"& return is not permitted for the
24885 &%acl_smtp_predata%& ACL.
24886
24887
24888 .cindex "&[local_scan()]& function" "when all recipients discarded"
24889 The &[local_scan()]& function is always run, even if there are no remaining
24890 recipients; it may create new recipients.
24891
24892
24893
24894 .section "Unset ACL options" "SECID197"
24895 .cindex "&ACL;" "unset options"
24896 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
24897 all the same. &*Note*&: These defaults apply only when the relevant ACL is
24898 not defined at all. For any defined ACL, the default action when control
24899 reaches the end of the ACL statements is &"deny"&.
24900
24901 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
24902 these two are ACLs that are used only for their side effects. They cannot be
24903 used to accept or reject anything.
24904
24905 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
24906 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
24907 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
24908 when the ACL is not defined is &"accept"&.
24909
24910 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
24911 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
24912 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
24913 messages over an SMTP connection. For an example, see the ACL in the default
24914 configuration file.
24915
24916
24917
24918
24919 .section "Data for message ACLs" "SECID198"
24920 .cindex "&ACL;" "data for message ACL"
24921 .vindex &$domain$&
24922 .vindex &$local_part$&
24923 .vindex &$sender_address$&
24924 .vindex &$sender_host_address$&
24925 .vindex &$smtp_command$&
24926 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
24927 that contain information about the host and the message's sender (for example,
24928 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
24929 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
24930 &$local_part$& are set from the argument address. The entire SMTP command
24931 is available in &$smtp_command$&.
24932
24933 When an ACL for the AUTH parameter of MAIL is running, the variables that
24934 contain information about the host are set, but &$sender_address$& is not yet
24935 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
24936 how it is used.
24937
24938 .vindex "&$message_size$&"
24939 The &$message_size$& variable is set to the value of the SIZE parameter on
24940 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
24941 that parameter is not given. The value is updated to the true message size by
24942 the time the final DATA ACL is run (after the message data has been
24943 received).
24944
24945 .vindex "&$rcpt_count$&"
24946 .vindex "&$recipients_count$&"
24947 The &$rcpt_count$& variable increases by one for each RCPT command received.
24948 The &$recipients_count$& variable increases by one each time a RCPT command is
24949 accepted, so while an ACL for RCPT is being processed, it contains the number
24950 of previously accepted recipients. At DATA time (for both the DATA ACLs),
24951 &$rcpt_count$& contains the total number of RCPT commands, and
24952 &$recipients_count$& contains the total number of accepted recipients.
24953
24954
24955
24956
24957
24958 .section "Data for non-message ACLs" "SECTdatfornon"
24959 .cindex "&ACL;" "data for non-message ACL"
24960 .vindex &$smtp_command_argument$&
24961 .vindex &$smtp_command$&
24962 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
24963 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
24964 and the entire SMTP command is available in &$smtp_command$&.
24965 These variables can be tested using a &%condition%& condition. For example,
24966 here is an ACL for use with AUTH, which insists that either the session is
24967 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
24968 does not permit authentication methods that use cleartext passwords on
24969 unencrypted connections.
24970 .code
24971 acl_check_auth:
24972 accept encrypted = *
24973 accept condition = ${if eq{${uc:$smtp_command_argument}}\
24974 {CRAM-MD5}}
24975 deny message = TLS encryption or CRAM-MD5 required
24976 .endd
24977 (Another way of applying this restriction is to arrange for the authenticators
24978 that use cleartext passwords not to be advertised when the connection is not
24979 encrypted. You can use the generic &%server_advertise_condition%& authenticator
24980 option to do this.)
24981
24982
24983
24984 .section "Format of an ACL" "SECID199"
24985 .cindex "&ACL;" "format of"
24986 .cindex "&ACL;" "verbs, definition of"
24987 An individual ACL consists of a number of statements. Each statement starts
24988 with a verb, optionally followed by a number of conditions and &"modifiers"&.
24989 Modifiers can change the way the verb operates, define error and log messages,
24990 set variables, insert delays, and vary the processing of accepted messages.
24991
24992 If all the conditions are met, the verb is obeyed. The same condition may be
24993 used (with different arguments) more than once in the same statement. This
24994 provides a means of specifying an &"and"& conjunction between conditions. For
24995 example:
24996 .code
24997 deny dnslists = list1.example
24998 dnslists = list2.example
24999 .endd
25000 If there are no conditions, the verb is always obeyed. Exim stops evaluating
25001 the conditions and modifiers when it reaches a condition that fails. What
25002 happens then depends on the verb (and in one case, on a special modifier). Not
25003 all the conditions make sense at every testing point. For example, you cannot
25004 test a sender address in the ACL that is run for a VRFY command.
25005
25006
25007 .section "ACL verbs" "SECID200"
25008 The ACL verbs are as follows:
25009
25010 .ilist
25011 .cindex "&%accept%& ACL verb"
25012 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
25013 of the conditions are not met, what happens depends on whether &%endpass%&
25014 appears among the conditions (for syntax see below). If the failing condition
25015 is before &%endpass%&, control is passed to the next ACL statement; if it is
25016 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
25017 check a RCPT command:
25018 .code
25019 accept domains = +local_domains
25020 endpass
25021 verify = recipient
25022 .endd
25023 If the recipient domain does not match the &%domains%& condition, control
25024 passes to the next statement. If it does match, the recipient is verified, and
25025 the command is accepted if verification succeeds. However, if verification
25026 fails, the ACL yields &"deny"&, because the failing condition is after
25027 &%endpass%&.
25028
25029 The &%endpass%& feature has turned out to be confusing to many people, so its
25030 use is not recommended nowadays. It is always possible to rewrite an ACL so
25031 that &%endpass%& is not needed, and it is no longer used in the default
25032 configuration.
25033
25034 .cindex "&%message%& ACL modifier" "with &%accept%&"
25035 If a &%message%& modifier appears on an &%accept%& statement, its action
25036 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
25037 (when an &%accept%& verb either accepts or passes control to the next
25038 statement), &%message%& can be used to vary the message that is sent when an
25039 SMTP command is accepted. For example, in a RCPT ACL you could have:
25040 .display
25041 &`accept `&<&'some conditions'&>
25042 &` message = OK, I will allow you through today`&
25043 .endd
25044 You can specify an SMTP response code, optionally followed by an &"extended
25045 response code"& at the start of the message, but the first digit must be the
25046 same as would be sent by default, which is 2 for an &%accept%& verb.
25047
25048 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
25049 an error message that is used when access is denied. This behaviour is retained
25050 for backward compatibility, but current &"best practice"& is to avoid the use
25051 of &%endpass%&.
25052
25053
25054 .next
25055 .cindex "&%defer%& ACL verb"
25056 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
25057 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
25058 &%defer%& is the same as &%deny%&, because there is no way of sending a
25059 temporary error. For a RCPT command, &%defer%& is much the same as using a
25060 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
25061 be used in any ACL, and even for a recipient it might be a simpler approach.
25062
25063
25064 .next
25065 .cindex "&%deny%& ACL verb"
25066 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
25067 the conditions are not met, control is passed to the next ACL statement. For
25068 example,
25069 .code
25070 deny dnslists = blackholes.mail-abuse.org
25071 .endd
25072 rejects commands from hosts that are on a DNS black list.
25073
25074
25075 .next
25076 .cindex "&%discard%& ACL verb"
25077 &%discard%&: This verb behaves like &%accept%&, except that it returns
25078 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
25079 that are concerned with receiving messages. When all the conditions are true,
25080 the sending entity receives a &"success"& response. However, &%discard%& causes
25081 recipients to be discarded. If it is used in an ACL for RCPT, just the one
25082 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
25083 message's recipients are discarded. Recipients that are discarded before DATA
25084 do not appear in the log line when the &%log_recipients%& log selector is set.
25085
25086 If the &%log_message%& modifier is set when &%discard%& operates,
25087 its contents are added to the line that is automatically written to the log.
25088 The &%message%& modifier operates exactly as it does for &%accept%&.
25089
25090
25091 .next
25092 .cindex "&%drop%& ACL verb"
25093 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
25094 forcibly closed after the 5&'xx'& error message has been sent. For example:
25095 .code
25096 drop message = I don't take more than 20 RCPTs
25097 condition = ${if > {$rcpt_count}{20}}
25098 .endd
25099 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
25100 The connection is always dropped after sending a 550 response.
25101
25102 .next
25103 .cindex "&%require%& ACL verb"
25104 &%require%&: If all the conditions are met, control is passed to the next ACL
25105 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
25106 example, when checking a RCPT command,
25107 .code
25108 require message = Sender did not verify
25109 verify = sender
25110 .endd
25111 passes control to subsequent statements only if the message's sender can be
25112 verified. Otherwise, it rejects the command. Note the positioning of the
25113 &%message%& modifier, before the &%verify%& condition. The reason for this is
25114 discussed in section &<<SECTcondmodproc>>&.
25115
25116 .next
25117 .cindex "&%warn%& ACL verb"
25118 &%warn%&: If all the conditions are true, a line specified by the
25119 &%log_message%& modifier is written to Exim's main log. Control always passes
25120 to the next ACL statement. If any condition is false, the log line is not
25121 written. If an identical log line is requested several times in the same
25122 message, only one copy is actually written to the log. If you want to force
25123 duplicates to be written, use the &%logwrite%& modifier instead.
25124
25125 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
25126 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
25127 &%logwrite%&, and &%add_header%&) that appear before the first failing
25128 condition. There is more about adding header lines in section
25129 &<<SECTaddheadacl>>&.
25130
25131 If any condition on a &%warn%& statement cannot be completed (that is, there is
25132 some sort of defer), the log line specified by &%log_message%& is not written.
25133 This does not include the case of a forced failure from a lookup, which
25134 is considered to be a successful completion. After a defer, no further
25135 conditions or modifiers in the &%warn%& statement are processed. The incident
25136 is logged, and the ACL continues to be processed, from the next statement
25137 onwards.
25138
25139
25140 .vindex "&$acl_verify_message$&"
25141 When one of the &%warn%& conditions is an address verification that fails, the
25142 text of the verification failure message is in &$acl_verify_message$&. If you
25143 want this logged, you must set it up explicitly. For example:
25144 .code
25145 warn !verify = sender
25146 log_message = sender verify failed: $acl_verify_message
25147 .endd
25148 .endlist
25149
25150 At the end of each ACL there is an implicit unconditional &%deny%&.
25151
25152 As you can see from the examples above, the conditions and modifiers are
25153 written one to a line, with the first one on the same line as the verb, and
25154 subsequent ones on following lines. If you have a very long condition, you can
25155 continue it onto several physical lines by the usual backslash continuation
25156 mechanism. It is conventional to align the conditions vertically.
25157
25158
25159
25160 .section "ACL variables" "SECTaclvariables"
25161 .cindex "&ACL;" "variables"
25162 There are some special variables that can be set during ACL processing. They
25163 can be used to pass information between different ACLs, different invocations
25164 of the same ACL in the same SMTP connection, and between ACLs and the routers,
25165 transports, and filters that are used to deliver a message. The names of these
25166 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
25167 an underscore, but the remainder of the name can be any sequence of
25168 alphanumeric characters and underscores that you choose. There is no limit on
25169 the number of ACL variables. The two sets act as follows:
25170 .ilist
25171 The values of those variables whose names begin with &$acl_c$& persist
25172 throughout an SMTP connection. They are never reset. Thus, a value that is set
25173 while receiving one message is still available when receiving the next message
25174 on the same SMTP connection.
25175 .next
25176 The values of those variables whose names begin with &$acl_m$& persist only
25177 while a message is being received. They are reset afterwards. They are also
25178 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
25179 .endlist
25180
25181 When a message is accepted, the current values of all the ACL variables are
25182 preserved with the message and are subsequently made available at delivery
25183 time. The ACL variables are set by a modifier called &%set%&. For example:
25184 .code
25185 accept hosts = whatever
25186 set acl_m4 = some value
25187 accept authenticated = *
25188 set acl_c_auth = yes
25189 .endd
25190 &*Note*&: A leading dollar sign is not used when naming a variable that is to
25191 be set. If you want to set a variable without taking any action, you can use a
25192 &%warn%& verb without any other modifiers or conditions.
25193
25194 .oindex &%strict_acl_vars%&
25195 What happens if a syntactically valid but undefined ACL variable is
25196 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
25197 false (the default), an empty string is substituted; if it is true, an
25198 error is generated.
25199
25200 Versions of Exim before 4.64 have a limited set of numbered variables, but
25201 their names are compatible, so there is no problem with upgrading.
25202
25203
25204 .section "Condition and modifier processing" "SECTcondmodproc"
25205 .cindex "&ACL;" "conditions; processing"
25206 .cindex "&ACL;" "modifiers; processing"
25207 An exclamation mark preceding a condition negates its result. For example:
25208 .code
25209 deny domains = *.dom.example
25210 !verify = recipient
25211 .endd
25212 causes the ACL to return &"deny"& if the recipient domain ends in
25213 &'dom.example'& and the recipient address cannot be verified. Sometimes
25214 negation can be used on the right-hand side of a condition. For example, these
25215 two statements are equivalent:
25216 .code
25217 deny hosts = !192.168.3.4
25218 deny !hosts = 192.168.3.4
25219 .endd
25220 However, for many conditions (&%verify%& being a good example), only left-hand
25221 side negation of the whole condition is possible.
25222
25223 The arguments of conditions and modifiers are expanded. A forced failure
25224 of an expansion causes a condition to be ignored, that is, it behaves as if the
25225 condition is true. Consider these two statements:
25226 .code
25227 accept senders = ${lookup{$host_name}lsearch\
25228 {/some/file}{$value}fail}
25229 accept senders = ${lookup{$host_name}lsearch\
25230 {/some/file}{$value}{}}
25231 .endd
25232 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
25233 the returned list is searched, but if the lookup fails the behaviour is
25234 different in the two cases. The &%fail%& in the first statement causes the
25235 condition to be ignored, leaving no further conditions. The &%accept%& verb
25236 therefore succeeds. The second statement, however, generates an empty list when
25237 the lookup fails. No sender can match an empty list, so the condition fails,
25238 and therefore the &%accept%& also fails.
25239
25240 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
25241 specify actions that are taken as the conditions for a statement are checked;
25242 others specify text for messages that are used when access is denied or a
25243 warning is generated. The &%control%& modifier affects the way an incoming
25244 message is handled.
25245
25246 The positioning of the modifiers in an ACL statement important, because the
25247 processing of a verb ceases as soon as its outcome is known. Only those
25248 modifiers that have already been encountered will take effect. For example,
25249 consider this use of the &%message%& modifier:
25250 .code
25251 require message = Can't verify sender
25252 verify = sender
25253 message = Can't verify recipient
25254 verify = recipient
25255 message = This message cannot be used
25256 .endd
25257 If sender verification fails, Exim knows that the result of the statement is
25258 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
25259 so its text is used as the error message. If sender verification succeeds, but
25260 recipient verification fails, the second message is used. If recipient
25261 verification succeeds, the third message becomes &"current"&, but is never used
25262 because there are no more conditions to cause failure.
25263
25264 For the &%deny%& verb, on the other hand, it is always the last &%message%&
25265 modifier that is used, because all the conditions must be true for rejection to
25266 happen. Specifying more than one &%message%& modifier does not make sense, and
25267 the message can even be specified after all the conditions. For example:
25268 .code
25269 deny hosts = ...
25270 !senders = *@my.domain.example
25271 message = Invalid sender from client host
25272 .endd
25273 The &"deny"& result does not happen until the end of the statement is reached,
25274 by which time Exim has set up the message.
25275
25276
25277
25278 .section "ACL modifiers" "SECTACLmodi"
25279 .cindex "&ACL;" "modifiers; list of"
25280 The ACL modifiers are as follows:
25281
25282 .vlist
25283 .vitem &*add_header*&&~=&~<&'text'&>
25284 This modifier specifies one or more header lines that are to be added to an
25285 incoming message, assuming, of course, that the message is ultimately
25286 accepted. For details, see section &<<SECTaddheadacl>>&.
25287
25288 .vitem &*continue*&&~=&~<&'text'&>
25289 .cindex "&%continue%& ACL modifier"
25290 .cindex "database" "updating in ACL"
25291 This modifier does nothing of itself, and processing of the ACL always
25292 continues with the next condition or modifier. The value of &%continue%& is in
25293 the side effects of expanding its argument. Typically this could be used to
25294 update a database. It is really just a syntactic tidiness, to avoid having to
25295 write rather ugly lines like this:
25296 .display
25297 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
25298 .endd
25299 Instead, all you need is
25300 .display
25301 &`continue = `&<&'some expansion'&>
25302 .endd
25303
25304 .vitem &*control*&&~=&~<&'text'&>
25305 .cindex "&%control%& ACL modifier"
25306 This modifier affects the subsequent processing of the SMTP connection or of an
25307 incoming message that is accepted. The effect of the first type of control
25308 lasts for the duration of the connection, whereas the effect of the second type
25309 lasts only until the current message has been received. The message-specific
25310 controls always apply to the whole message, not to individual recipients,
25311 even if the &%control%& modifier appears in a RCPT ACL.
25312
25313 As there are now quite a few controls that can be applied, they are described
25314 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
25315 in several different ways. For example:
25316
25317 . ==== As this is a nested list, any displays it contains must be indented
25318 . ==== as otherwise they are too far to the left. That comment applies only
25319 . ==== when xmlto and fop are used; formatting with sdop gets it right either
25320 . ==== way.
25321
25322 .ilist
25323 It can be at the end of an &%accept%& statement:
25324 .code
25325 accept ...some conditions
25326 control = queue_only
25327 .endd
25328 In this case, the control is applied when this statement yields &"accept"&, in
25329 other words, when the conditions are all true.
25330
25331 .next
25332 It can be in the middle of an &%accept%& statement:
25333 .code
25334 accept ...some conditions...
25335 control = queue_only
25336 ...some more conditions...
25337 .endd
25338 If the first set of conditions are true, the control is applied, even if the
25339 statement does not accept because one of the second set of conditions is false.
25340 In this case, some subsequent statement must yield &"accept"& for the control
25341 to be relevant.
25342
25343 .next
25344 It can be used with &%warn%& to apply the control, leaving the
25345 decision about accepting or denying to a subsequent verb. For
25346 example:
25347 .code
25348 warn ...some conditions...
25349 control = freeze
25350 accept ...
25351 .endd
25352 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
25353 &%logwrite%&, so it does not add anything to the message and does not write a
25354 log entry.
25355
25356 .next
25357 If you want to apply a control unconditionally, you can use it with a
25358 &%require%& verb. For example:
25359 .code
25360 require control = no_multiline_responses
25361 .endd
25362 .endlist
25363
25364 .vitem &*delay*&&~=&~<&'time'&>
25365 .cindex "&%delay%& ACL modifier"
25366 .oindex "&%-bh%&"
25367 This modifier may appear in any ACL. It causes Exim to wait for the time
25368 interval before proceeding. However, when testing Exim using the &%-bh%&
25369 option, the delay is not actually imposed (an appropriate message is output
25370 instead). The time is given in the usual Exim notation, and the delay happens
25371 as soon as the modifier is processed. In an SMTP session, pending output is
25372 flushed before the delay is imposed.
25373
25374 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
25375 example:
25376 .code
25377 deny ...some conditions...
25378 delay = 30s
25379 .endd
25380 The delay happens if all the conditions are true, before the statement returns
25381 &"deny"&. Compare this with:
25382 .code
25383 deny delay = 30s
25384 ...some conditions...
25385 .endd
25386 which waits for 30s before processing the conditions. The &%delay%& modifier
25387 can also be used with &%warn%& and together with &%control%&:
25388 .code
25389 warn ...some conditions...
25390 delay = 2m
25391 control = freeze
25392 accept ...
25393 .endd
25394
25395 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
25396 responses to several commands are no longer buffered and sent in one packet (as
25397 they would normally be) because all output is flushed before imposing the
25398 delay. This optimization is disabled so that a number of small delays do not
25399 appear to the client as one large aggregated delay that might provoke an
25400 unwanted timeout. You can, however, disable output flushing for &%delay%& by
25401 using a &%control%& modifier to set &%no_delay_flush%&.
25402
25403
25404 .vitem &*endpass*&
25405 .cindex "&%endpass%& ACL modifier"
25406 This modifier, which has no argument, is recognized only in &%accept%& and
25407 &%discard%& statements. It marks the boundary between the conditions whose
25408 failure causes control to pass to the next statement, and the conditions whose
25409 failure causes the ACL to return &"deny"&. This concept has proved to be
25410 confusing to some people, so the use of &%endpass%& is no longer recommended as
25411 &"best practice"&. See the description of &%accept%& above for more details.
25412
25413
25414 .vitem &*log_message*&&~=&~<&'text'&>
25415 .cindex "&%log_message%& ACL modifier"
25416 This modifier sets up a message that is used as part of the log message if the
25417 ACL denies access or a &%warn%& statement's conditions are true. For example:
25418 .code
25419 require log_message = wrong cipher suite $tls_cipher
25420 encrypted = DES-CBC3-SHA
25421 .endd
25422 &%log_message%& is also used when recipients are discarded by &%discard%&. For
25423 example:
25424 .display
25425 &`discard `&<&'some conditions'&>
25426 &` log_message = Discarded $local_part@$domain because...`&
25427 .endd
25428 When access is denied, &%log_message%& adds to any underlying error message
25429 that may exist because of a condition failure. For example, while verifying a
25430 recipient address, a &':fail:'& redirection might have already set up a
25431 message.
25432
25433 The message may be defined before the conditions to which it applies, because
25434 the string expansion does not happen until Exim decides that access is to be
25435 denied. This means that any variables that are set by the condition are
25436 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
25437 variables are set after a DNS black list lookup succeeds. If the expansion of
25438 &%log_message%& fails, or if the result is an empty string, the modifier is
25439 ignored.
25440
25441 .vindex "&$acl_verify_message$&"
25442 If you want to use a &%warn%& statement to log the result of an address
25443 verification, you can use &$acl_verify_message$& to include the verification
25444 error message.
25445
25446 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
25447 the start of the logged message. If the same warning log message is requested
25448 more than once while receiving a single email message, only one copy is
25449 actually logged. If you want to log multiple copies, use &%logwrite%& instead
25450 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
25451 is logged for a successful &%warn%& statement.
25452
25453 If &%log_message%& is not present and there is no underlying error message (for
25454 example, from the failure of address verification), but &%message%& is present,
25455 the &%message%& text is used for logging rejections. However, if any text for
25456 logging contains newlines, only the first line is logged. In the absence of
25457 both &%log_message%& and &%message%&, a default built-in message is used for
25458 logging rejections.
25459
25460
25461 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
25462 .cindex "&%log_reject_target%& ACL modifier"
25463 .cindex "logging in ACL" "specifying which log"
25464 This modifier makes it possible to specify which logs are used for messages
25465 about ACL rejections. Its argument is a colon-separated list of words that can
25466 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
25467 may be empty, in which case a rejection is not logged at all. For example, this
25468 ACL fragment writes no logging information when access is denied:
25469 .display
25470 &`deny `&<&'some conditions'&>
25471 &` log_reject_target =`&
25472 .endd
25473 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
25474 permanent and temporary rejections.
25475
25476
25477 .vitem &*logwrite*&&~=&~<&'text'&>
25478 .cindex "&%logwrite%& ACL modifier"
25479 .cindex "logging in ACL" "immediate"
25480 This modifier writes a message to a log file as soon as it is encountered when
25481 processing an ACL. (Compare &%log_message%&, which, except in the case of
25482 &%warn%& and &%discard%&, is used only if the ACL statement denies
25483 access.) The &%logwrite%& modifier can be used to log special incidents in
25484 ACLs. For example:
25485 .display
25486 &`accept `&<&'some special conditions'&>
25487 &` control = freeze`&
25488 &` logwrite = froze message because ...`&
25489 .endd
25490 By default, the message is written to the main log. However, it may begin
25491 with a colon, followed by a comma-separated list of log names, and then
25492 another colon, to specify exactly which logs are to be written. For
25493 example:
25494 .code
25495 logwrite = :main,reject: text for main and reject logs
25496 logwrite = :panic: text for panic log only
25497 .endd
25498
25499
25500 .vitem &*message*&&~=&~<&'text'&>
25501 .cindex "&%message%& ACL modifier"
25502 This modifier sets up a text string that is expanded and used as a response
25503 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
25504 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
25505 there is some complication if &%endpass%& is involved; see the description of
25506 &%accept%& for details.)
25507
25508 The expansion of the message happens at the time Exim decides that the ACL is
25509 to end, not at the time it processes &%message%&. If the expansion fails, or
25510 generates an empty string, the modifier is ignored. Here is an example where
25511 &%message%& must be specified first, because the ACL ends with a rejection if
25512 the &%hosts%& condition fails:
25513 .code
25514 require message = Host not recognized
25515 hosts = 10.0.0.0/8
25516 .endd
25517 (Once a condition has failed, no further conditions or modifiers are
25518 processed.)
25519
25520 .cindex "SMTP" "error codes"
25521 .oindex "&%smtp_banner%&
25522 For ACLs that are triggered by SMTP commands, the message is returned as part
25523 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
25524 is meaningful only for SMTP, as no message is returned when a non-SMTP message
25525 is accepted. In the case of the connect ACL, accepting with a message modifier
25526 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
25527 accept message may not contain more than one line (otherwise it will be
25528 truncated at the first newline and a panic logged), and it cannot affect the
25529 EHLO options.
25530
25531 When SMTP is involved, the message may begin with an overriding response code,
25532 consisting of three digits optionally followed by an &"extended response code"&
25533 of the form &'n.n.n'&, each code being followed by a space. For example:
25534 .code
25535 deny message = 599 1.2.3 Host not welcome
25536 hosts = 192.168.34.0/24
25537 .endd
25538 The first digit of the supplied response code must be the same as would be sent
25539 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
25540 access, but for the predata ACL, note that the default success code is 354, not
25541 2&'xx'&.
25542
25543 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
25544 the message modifier cannot override the 221 response code.
25545
25546 The text in a &%message%& modifier is literal; any quotes are taken as
25547 literals, but because the string is expanded, backslash escapes are processed
25548 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
25549 response.
25550
25551 .vindex "&$acl_verify_message$&"
25552 If &%message%& is used on a statement that verifies an address, the message
25553 specified overrides any message that is generated by the verification process.
25554 However, the original message is available in the variable
25555 &$acl_verify_message$&, so you can incorporate it into your message if you
25556 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
25557 routers to be passed back as part of the SMTP response, you should either not
25558 use a &%message%& modifier, or make use of &$acl_verify_message$&.
25559
25560 For compatibility with previous releases of Exim, a &%message%& modifier that
25561 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
25562 modifier, but this usage is now deprecated. However, &%message%& acts only when
25563 all the conditions are true, wherever it appears in an ACL command, whereas
25564 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
25565 &%warn%& in an ACL that is not concerned with receiving a message, it has no
25566 effect.
25567
25568
25569 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
25570 .cindex "&%set%& ACL modifier"
25571 This modifier puts a value into one of the ACL variables (see section
25572 &<<SECTaclvariables>>&).
25573 .endlist
25574
25575
25576
25577
25578
25579 .section "Use of the control modifier" "SECTcontrols"
25580 .cindex "&%control%& ACL modifier"
25581 The &%control%& modifier supports the following settings:
25582
25583 .vlist
25584 .vitem &*control&~=&~allow_auth_unadvertised*&
25585 This modifier allows a client host to use the SMTP AUTH command even when it
25586 has not been advertised in response to EHLO. Furthermore, because there are
25587 apparently some really broken clients that do this, Exim will accept AUTH after
25588 HELO (rather than EHLO) when this control is set. It should be used only if you
25589 really need it, and you should limit its use to those broken clients that do
25590 not work without it. For example:
25591 .code
25592 warn hosts = 192.168.34.25
25593 control = allow_auth_unadvertised
25594 .endd
25595 Normally, when an Exim server receives an AUTH command, it checks the name of
25596 the authentication mechanism that is given in the command to ensure that it
25597 matches an advertised mechanism. When this control is set, the check that a
25598 mechanism has been advertised is bypassed. Any configured mechanism can be used
25599 by the client. This control is permitted only in the connection and HELO ACLs.
25600
25601
25602 .vitem &*control&~=&~caseful_local_part*& &&&
25603 &*control&~=&~caselower_local_part*&
25604 .cindex "&ACL;" "case of local part in"
25605 .cindex "case of local parts"
25606 .vindex "&$local_part$&"
25607 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
25608 (that is, during RCPT processing). By default, the contents of &$local_part$&
25609 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
25610 any uppercase letters in the original local part are restored in &$local_part$&
25611 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
25612 is encountered.
25613
25614 These controls affect only the current recipient. Moreover, they apply only to
25615 local part handling that takes place directly in the ACL (for example, as a key
25616 in lookups). If a test to verify the recipient is obeyed, the case-related
25617 handling of the local part during the verification is controlled by the router
25618 configuration (see the &%caseful_local_part%& generic router option).
25619
25620 This facility could be used, for example, to add a spam score to local parts
25621 containing upper case letters. For example, using &$acl_m4$& to accumulate the
25622 spam score:
25623 .code
25624 warn control = caseful_local_part
25625 set acl_m4 = ${eval:\
25626 $acl_m4 + \
25627 ${if match{$local_part}{[A-Z]}{1}{0}}\
25628 }
25629 control = caselower_local_part
25630 .endd
25631 Notice that we put back the lower cased version afterwards, assuming that
25632 is what is wanted for subsequent tests.
25633
25634 .vitem &*control&~=&~enforce_sync*& &&&
25635 &*control&~=&~no_enforce_sync*&
25636 .cindex "SMTP" "synchronization checking"
25637 .cindex "synchronization checking in SMTP"
25638 These controls make it possible to be selective about when SMTP synchronization
25639 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
25640 state of the switch (it is true by default). See the description of this option
25641 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
25642
25643 The effect of these two controls lasts for the remainder of the SMTP
25644 connection. They can appear in any ACL except the one for the non-SMTP
25645 messages. The most straightforward place to put them is in the ACL defined by
25646 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
25647 before the first synchronization check. The expected use is to turn off the
25648 synchronization checks for badly-behaved hosts that you nevertheless need to
25649 work with.
25650
25651
25652 .vitem &*control&~=&~fakedefer/*&<&'message'&>
25653 .cindex "fake defer"
25654 .cindex "defer, fake"
25655 This control works in exactly the same way as &%fakereject%& (described below)
25656 except that it causes an SMTP 450 response after the message data instead of a
25657 550 response. You must take care when using &%fakedefer%& because it causes the
25658 messages to be duplicated when the sender retries. Therefore, you should not
25659 use &%fakedefer%& if the message is to be delivered normally.
25660
25661 .vitem &*control&~=&~fakereject/*&<&'message'&>
25662 .cindex "fake rejection"
25663 .cindex "rejection, fake"
25664 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
25665 words, only when an SMTP message is being received. If Exim accepts the
25666 message, instead the final 250 response, a 550 rejection message is sent.
25667 However, Exim proceeds to deliver the message as normal. The control applies
25668 only to the current message, not to any subsequent ones that may be received in
25669 the same SMTP connection.
25670
25671 The text for the 550 response is taken from the &%control%& modifier. If no
25672 message is supplied, the following is used:
25673 .code
25674 550-Your message has been rejected but is being
25675 550-kept for evaluation.
25676 550-If it was a legitimate message, it may still be
25677 550 delivered to the target recipient(s).
25678 .endd
25679 This facility should be used with extreme caution.
25680
25681 .vitem &*control&~=&~freeze*&
25682 .cindex "frozen messages" "forcing in ACL"
25683 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
25684 other words, only when a message is being received. If the message is accepted,
25685 it is placed on Exim's queue and frozen. The control applies only to the
25686 current message, not to any subsequent ones that may be received in the same
25687 SMTP connection.
25688
25689 This modifier can optionally be followed by &`/no_tell`&. If the global option
25690 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
25691 is told about the freezing), provided all the &*control=freeze*& modifiers that
25692 are obeyed for the current message have the &`/no_tell`& option.
25693
25694 .vitem &*control&~=&~no_delay_flush*&
25695 .cindex "SMTP" "output flushing, disabling for delay"
25696 Exim normally flushes SMTP output before implementing a delay in an ACL, to
25697 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
25698 use. This control, as long as it is encountered before the &%delay%& modifier,
25699 disables such output flushing.
25700
25701 .vitem &*control&~=&~no_callout_flush*&
25702 .cindex "SMTP" "output flushing, disabling for callout"
25703 Exim normally flushes SMTP output before performing a callout in an ACL, to
25704 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
25705 use. This control, as long as it is encountered before the &%verify%& condition
25706 that causes the callout, disables such output flushing.
25707
25708 .vitem &*control&~=&~no_mbox_unspool*&
25709 This control is available when Exim is compiled with the content scanning
25710 extension. Content scanning may require a copy of the current message, or parts
25711 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
25712 or spam scanner. Normally, such copies are deleted when they are no longer
25713 needed. If this control is set, the copies are not deleted. The control applies
25714 only to the current message, not to any subsequent ones that may be received in
25715 the same SMTP connection. It is provided for debugging purposes and is unlikely
25716 to be useful in production.
25717
25718 .vitem &*control&~=&~no_multiline_responses*&
25719 .cindex "multiline responses, suppressing"
25720 This control is permitted for any ACL except the one for non-SMTP messages.
25721 It seems that there are broken clients in use that cannot handle multiline
25722 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
25723
25724 If this control is set, multiline SMTP responses from ACL rejections are
25725 suppressed. One way of doing this would have been to put out these responses as
25726 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
25727 (&"use multiline responses for more"& it says &-- ha!), and some of the
25728 responses might get close to that. So this facility, which is after all only a
25729 sop to broken clients, is implemented by doing two very easy things:
25730
25731 .ilist
25732 Extra information that is normally output as part of a rejection caused by
25733 sender verification failure is omitted. Only the final line (typically &"sender
25734 verification failed"&) is sent.
25735 .next
25736 If a &%message%& modifier supplies a multiline response, only the first
25737 line is output.
25738 .endlist
25739
25740 The setting of the switch can, of course, be made conditional on the
25741 calling host. Its effect lasts until the end of the SMTP connection.
25742
25743 .vitem &*control&~=&~no_pipelining*&
25744 .cindex "PIPELINING" "suppressing advertising"
25745 This control turns off the advertising of the PIPELINING extension to SMTP in
25746 the current session. To be useful, it must be obeyed before Exim sends its
25747 response to an EHLO command. Therefore, it should normally appear in an ACL
25748 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
25749 &%pipelining_advertise_hosts%&.
25750
25751 .vitem &*control&~=&~queue_only*&
25752 .oindex "&%queue_only%&"
25753 .cindex "queueing incoming messages"
25754 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
25755 other words, only when a message is being received. If the message is accepted,
25756 it is placed on Exim's queue and left there for delivery by a subsequent queue
25757 runner. No immediate delivery process is started. In other words, it has the
25758 effect as the &%queue_only%& global option. However, the control applies only
25759 to the current message, not to any subsequent ones that may be received in the
25760 same SMTP connection.
25761
25762 .vitem &*control&~=&~submission/*&<&'options'&>
25763 .cindex "message" "submission"
25764 .cindex "submission mode"
25765 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
25766 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
25767 the current message is a submission from a local MUA. In this case, Exim
25768 operates in &"submission mode"&, and applies certain fixups to the message if
25769 necessary. For example, it add a &'Date:'& header line if one is not present.
25770 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
25771 late (the message has already been created).
25772
25773 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
25774 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
25775 submission mode; the available options for this control are described there.
25776 The control applies only to the current message, not to any subsequent ones
25777 that may be received in the same SMTP connection.
25778
25779 .vitem &*control&~=&~suppress_local_fixups*&
25780 .cindex "submission fixups, suppressing"
25781 This control applies to locally submitted (non TCP/IP) messages, and is the
25782 complement of &`control`& &`=`& &`submission`&. It disables the fixups that are
25783 normally applied to locally-submitted messages. Specifically:
25784
25785 .ilist
25786 Any &'Sender:'& header line is left alone (in this respect, it is a
25787 dynamic version of &%local_sender_retain%&).
25788 .next
25789 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
25790 .next
25791 There is no check that &'From:'& corresponds to the actual sender.
25792 .endlist ilist
25793
25794 This control may be useful when a remotely-originated message is accepted,
25795 passed to some scanning program, and then re-submitted for delivery. It can be
25796 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
25797 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
25798 data is read.
25799
25800 &*Note:*& This control applies only to the current message, not to any others
25801 that are being submitted at the same time using &%-bs%& or &%-bS%&.
25802 .endlist vlist
25803
25804
25805 .section "Summary of message fixup control" "SECTsummesfix"
25806 All four possibilities for message fixups can be specified:
25807
25808 .ilist
25809 Locally submitted, fixups applied: the default.
25810 .next
25811 Locally submitted, no fixups applied: use &`control`& &`=`&
25812 &`suppress_local_fixups`&.
25813 .next
25814 Remotely submitted, no fixups applied: the default.
25815 .next
25816 Remotely submitted, fixups applied: use &`control`& &`=`& &`submission`&.
25817 .endlist
25818
25819
25820
25821 .section "Adding header lines in ACLs" "SECTaddheadacl"
25822 .cindex "header lines" "adding in an ACL"
25823 .cindex "header lines" "position of added lines"
25824 .cindex "&%message%& ACL modifier"
25825 The &%add_header%& modifier can be used to add one or more extra header lines
25826 to an incoming message, as in this example:
25827 .code
25828 warn dnslists = sbl.spamhaus.org : \
25829 dialup.mail-abuse.org
25830 add_header = X-blacklisted-at: $dnslist_domain
25831 .endd
25832 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
25833 MIME, and non-SMTP ACLs (in other words, those that are concerned with
25834 receiving a message). The message must ultimately be accepted for
25835 &%add_header%& to have any significant effect. You can use &%add_header%& with
25836 any ACL verb, including &%deny%& (though this is potentially useful only in a
25837 RCPT ACL).
25838
25839 If the data for the &%add_header%& modifier contains one or more newlines that
25840 are not followed by a space or a tab, it is assumed to contain multiple header
25841 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
25842 front of any line that is not a valid header line.
25843
25844 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
25845 They are added to the message before processing the DATA and MIME ACLs.
25846 However, if an identical header line is requested more than once, only one copy
25847 is actually added to the message. Further header lines may be accumulated
25848 during the DATA and MIME ACLs, after which they are added to the message, again
25849 with duplicates suppressed. Thus, it is possible to add two identical header
25850 lines to an SMTP message, but only if one is added before DATA and one after.
25851 In the case of non-SMTP messages, new headers are accumulated during the
25852 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
25853 message is rejected after DATA or by the non-SMTP ACL, all added header lines
25854 are included in the entry that is written to the reject log.
25855
25856 .cindex "header lines" "added; visibility of"
25857 Header lines are not visible in string expansions until they are added to the
25858 message. It follows that header lines defined in the MAIL, RCPT, and predata
25859 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
25860 header lines that are added by the DATA or MIME ACLs are not visible in those
25861 ACLs. Because of this restriction, you cannot use header lines as a way of
25862 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
25863 this, you can use ACL variables, as described in section
25864 &<<SECTaclvariables>>&.
25865
25866 The &%add_header%& modifier acts immediately it is encountered during the
25867 processing of an ACL. Notice the difference between these two cases:
25868 .display
25869 &`accept add_header = ADDED: some text`&
25870 &` `&<&'some condition'&>
25871
25872 &`accept `&<&'some condition'&>
25873 &` add_header = ADDED: some text`&
25874 .endd
25875 In the first case, the header line is always added, whether or not the
25876 condition is true. In the second case, the header line is added only if the
25877 condition is true. Multiple occurrences of &%add_header%& may occur in the same
25878 ACL statement. All those that are encountered before a condition fails are
25879 honoured.
25880
25881 .cindex "&%warn%& ACL verb"
25882 For compatibility with previous versions of Exim, a &%message%& modifier for a
25883 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
25884 effect only if all the conditions are true, even if it appears before some of
25885 them. Furthermore, only the last occurrence of &%message%& is honoured. This
25886 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
25887 are present on a &%warn%& verb, both are processed according to their
25888 specifications.
25889
25890 By default, new header lines are added to a message at the end of the existing
25891 header lines. However, you can specify that any particular header line should
25892 be added right at the start (before all the &'Received:'& lines), immediately
25893 after the first block of &'Received:'& lines, or immediately before any line
25894 that is not a &'Received:'& or &'Resent-something:'& header.
25895
25896 This is done by specifying &":at_start:"&, &":after_received:"&, or
25897 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
25898 header line, respectively. (Header text cannot start with a colon, as there has
25899 to be a header name first.) For example:
25900 .code
25901 warn add_header = \
25902 :after_received:X-My-Header: something or other...
25903 .endd
25904 If more than one header line is supplied in a single &%add_header%& modifier,
25905 each one is treated independently and can therefore be placed differently. If
25906 you add more than one line at the start, or after the Received: block, they end
25907 up in reverse order.
25908
25909 &*Warning*&: This facility currently applies only to header lines that are
25910 added in an ACL. It does NOT work for header lines that are added in a
25911 system filter or in a router or transport.
25912
25913
25914
25915
25916 .section "ACL conditions" "SECTaclconditions"
25917 .cindex "&ACL;" "conditions; list of"
25918 Some of conditions listed in this section are available only when Exim is
25919 compiled with the content-scanning extension. They are included here briefly
25920 for completeness. More detailed descriptions can be found in the discussion on
25921 content scanning in chapter &<<CHAPexiscan>>&.
25922
25923 Not all conditions are relevant in all circumstances. For example, testing
25924 senders and recipients does not make sense in an ACL that is being run as the
25925 result of the arrival of an ETRN command, and checks on message headers can be
25926 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
25927 can use the same condition (with different parameters) more than once in the
25928 same ACL statement. This provides a way of specifying an &"and"& conjunction.
25929 The conditions are as follows:
25930
25931
25932 .vlist
25933 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
25934 .cindex "&ACL;" "nested"
25935 .cindex "&ACL;" "indirect"
25936 .cindex "&%acl%& ACL condition"
25937 The possible values of the argument are the same as for the
25938 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
25939 &"accept"& the condition is true; if it returns &"deny"& the condition is
25940 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
25941 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
25942 condition false. This means that further processing of the &%warn%& verb
25943 ceases, but processing of the ACL continues.
25944
25945 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
25946 the connection is dropped. If it returns &"discard"&, the verb must be
25947 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
25948 conditions are tested.
25949
25950 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
25951 loops. This condition allows you to use different ACLs in different
25952 circumstances. For example, different ACLs can be used to handle RCPT commands
25953 for different local users or different local domains.
25954
25955 .vitem &*authenticated&~=&~*&<&'string&~list'&>
25956 .cindex "&%authenticated%& ACL condition"
25957 .cindex "authentication" "ACL checking"
25958 .cindex "&ACL;" "testing for authentication"
25959 If the SMTP connection is not authenticated, the condition is false. Otherwise,
25960 the name of the authenticator is tested against the list. To test for
25961 authentication by any authenticator, you can set
25962 .code
25963 authenticated = *
25964 .endd
25965
25966 .vitem &*condition&~=&~*&<&'string'&>
25967 .cindex "&%condition%& ACL condition"
25968 .cindex "customizing" "ACL condition"
25969 .cindex "&ACL;" "customized test"
25970 .cindex "&ACL;" "testing, customized"
25971 This feature allows you to make up custom conditions. If the result of
25972 expanding the string is an empty string, the number zero, or one of the strings
25973 &"no"& or &"false"&, the condition is false. If the result is any non-zero
25974 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
25975 any other value, some error is assumed to have occurred, and the ACL returns
25976 &"defer"&. However, if the expansion is forced to fail, the condition is
25977 ignored. The effect is to treat it as true, whether it is positive or
25978 negative.
25979
25980 .vitem &*decode&~=&~*&<&'location'&>
25981 .cindex "&%decode%& ACL condition"
25982 This condition is available only when Exim is compiled with the
25983 content-scanning extension, and it is allowed only in the ACL defined by
25984 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
25985 If all goes well, the condition is true. It is false only if there are
25986 problems such as a syntax error or a memory shortage. For more details, see
25987 chapter &<<CHAPexiscan>>&.
25988
25989 .vitem &*demime&~=&~*&<&'extension&~list'&>
25990 .cindex "&%demime%& ACL condition"
25991 This condition is available only when Exim is compiled with the
25992 content-scanning extension. Its use is described in section
25993 &<<SECTdemimecond>>&.
25994
25995 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
25996 .cindex "&%dnslists%& ACL condition"
25997 .cindex "DNS list" "in ACL"
25998 .cindex "black list (DNS)"
25999 .cindex "&ACL;" "testing a DNS list"
26000 This condition checks for entries in DNS black lists. These are also known as
26001 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
26002 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
26003 different variants of this condition to describe briefly here. See sections
26004 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
26005
26006 .vitem &*domains&~=&~*&<&'domain&~list'&>
26007 .cindex "&%domains%& ACL condition"
26008 .cindex "domain" "ACL checking"
26009 .cindex "&ACL;" "testing a recipient domain"
26010 .vindex "&$domain_data$&"
26011 This condition is relevant only after a RCPT command. It checks that the domain
26012 of the recipient address is in the domain list. If percent-hack processing is
26013 enabled, it is done before this test is done. If the check succeeds with a
26014 lookup, the result of the lookup is placed in &$domain_data$& until the next
26015 &%domains%& test.
26016
26017 &*Note carefully*& (because many people seem to fall foul of this): you cannot
26018 use &%domains%& in a DATA ACL.
26019
26020
26021 .vitem &*encrypted&~=&~*&<&'string&~list'&>
26022 .cindex "&%encrypted%& ACL condition"
26023 .cindex "encryption" "checking in an ACL"
26024 .cindex "&ACL;" "testing for encryption"
26025 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
26026 name of the cipher suite in use is tested against the list. To test for
26027 encryption without testing for any specific cipher suite(s), set
26028 .code
26029 encrypted = *
26030 .endd
26031
26032
26033 .vitem &*hosts&~=&~*&<&'&~host&~list'&>
26034 .cindex "&%hosts%& ACL condition"
26035 .cindex "host" "ACL checking"
26036 .cindex "&ACL;" "testing the client host"
26037 This condition tests that the calling host matches the host list. If you have
26038 name lookups or wildcarded host names and IP addresses in the same host list,
26039 you should normally put the IP addresses first. For example, you could have:
26040 .code
26041 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
26042 .endd
26043 The lookup in this example uses the host name for its key. This is implied by
26044 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
26045 and it wouldn't matter which way round you had these two items.)
26046
26047 The reason for the problem with host names lies in the left-to-right way that
26048 Exim processes lists. It can test IP addresses without doing any DNS lookups,
26049 but when it reaches an item that requires a host name, it fails if it cannot
26050 find a host name to compare with the pattern. If the above list is given in the
26051 opposite order, the &%accept%& statement fails for a host whose name cannot be
26052 found, even if its IP address is 10.9.8.7.
26053
26054 If you really do want to do the name check first, and still recognize the IP
26055 address even if the name lookup fails, you can rewrite the ACL like this:
26056 .code
26057 accept hosts = dbm;/etc/friendly/hosts
26058 accept hosts = 10.9.8.7
26059 .endd
26060 The default action on failing to find the host name is to assume that the host
26061 is not in the list, so the first &%accept%& statement fails. The second
26062 statement can then check the IP address.
26063
26064 .vindex "&$host_data$&"
26065 If a &%hosts%& condition is satisfied by means of a lookup, the result
26066 of the lookup is made available in the &$host_data$& variable. This
26067 allows you, for example, to set up a statement like this:
26068 .code
26069 deny hosts = net-lsearch;/some/file
26070 message = $host_data
26071 .endd
26072 which gives a custom error message for each denied host.
26073
26074 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
26075 .cindex "&%local_parts%& ACL condition"
26076 .cindex "local part" "ACL checking"
26077 .cindex "&ACL;" "testing a local part"
26078 .vindex "&$local_part_data$&"
26079 This condition is relevant only after a RCPT command. It checks that the local
26080 part of the recipient address is in the list. If percent-hack processing is
26081 enabled, it is done before this test. If the check succeeds with a lookup, the
26082 result of the lookup is placed in &$local_part_data$&, which remains set until
26083 the next &%local_parts%& test.
26084
26085 .vitem &*malware&~=&~*&<&'option'&>
26086 .cindex "&%malware%& ACL condition"
26087 .cindex "&ACL;" "virus scanning"
26088 .cindex "&ACL;" "scanning for viruses"
26089 This condition is available only when Exim is compiled with the
26090 content-scanning extension. It causes the incoming message to be scanned for
26091 viruses. For details, see chapter &<<CHAPexiscan>>&.
26092
26093 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
26094 .cindex "&%mime_regex%& ACL condition"
26095 .cindex "&ACL;" "testing by regex matching"
26096 This condition is available only when Exim is compiled with the
26097 content-scanning extension, and it is allowed only in the ACL defined by
26098 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
26099 with any of the regular expressions. For details, see chapter
26100 &<<CHAPexiscan>>&.
26101
26102 .vitem &*ratelimit&~=&~*&<&'parameters'&>
26103 .cindex "rate limiting"
26104 This condition can be used to limit the rate at which a user or host submits
26105 messages. Details are given in section &<<SECTratelimiting>>&.
26106
26107 .vitem &*recipients&~=&~*&<&'address&~list'&>
26108 .cindex "&%recipients%& ACL condition"
26109 .cindex "recipient" "ACL checking"
26110 .cindex "&ACL;" "testing a recipient"
26111 This condition is relevant only after a RCPT command. It checks the entire
26112 recipient address against a list of recipients.
26113
26114 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
26115 .cindex "&%regex%& ACL condition"
26116 .cindex "&ACL;" "testing by regex matching"
26117 This condition is available only when Exim is compiled with the
26118 content-scanning extension, and is available only in the DATA, MIME, and
26119 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
26120 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
26121
26122 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
26123 .cindex "&%sender_domains%& ACL condition"
26124 .cindex "sender" "ACL checking"
26125 .cindex "&ACL;" "testing a sender domain"
26126 .vindex "&$domain$&"
26127 .vindex "&$sender_address_domain$&"
26128 This condition tests the domain of the sender of the message against the given
26129 domain list. &*Note*&: The domain of the sender address is in
26130 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
26131 of this condition. This is an exception to the general rule for testing domain
26132 lists. It is done this way so that, if this condition is used in an ACL for a
26133 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
26134 influence the sender checking.
26135
26136 &*Warning*&: It is a bad idea to use this condition on its own as a control on
26137 relaying, because sender addresses are easily, and commonly, forged.
26138
26139 .vitem &*senders&~=&~*&<&'address&~list'&>
26140 .cindex "&%senders%& ACL condition"
26141 .cindex "sender" "ACL checking"
26142 .cindex "&ACL;" "testing a sender"
26143 This condition tests the sender of the message against the given list. To test
26144 for a bounce message, which has an empty sender, set
26145 .code
26146 senders = :
26147 .endd
26148 &*Warning*&: It is a bad idea to use this condition on its own as a control on
26149 relaying, because sender addresses are easily, and commonly, forged.
26150
26151 .vitem &*spam&~=&~*&<&'username'&>
26152 .cindex "&%spam%& ACL condition"
26153 .cindex "&ACL;" "scanning for spam"
26154 This condition is available only when Exim is compiled with the
26155 content-scanning extension. It causes the incoming message to be scanned by
26156 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
26157
26158 .vitem &*verify&~=&~certificate*&
26159 .cindex "&%verify%& ACL condition"
26160 .cindex "TLS" "client certificate verification"
26161 .cindex "certificate" "verification of client"
26162 .cindex "&ACL;" "certificate verification"
26163 .cindex "&ACL;" "testing a TLS certificate"
26164 This condition is true in an SMTP session if the session is encrypted, and a
26165 certificate was received from the client, and the certificate was verified. The
26166 server requests a certificate only if the client matches &%tls_verify_hosts%&
26167 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
26168
26169 .vitem &*verify&~=&~csa*&
26170 .cindex "CSA verification"
26171 This condition checks whether the sending host (the client) is authorized to
26172 send email. Details of how this works are given in section
26173 &<<SECTverifyCSA>>&.
26174
26175 .vitem &*verify&~=&~header_sender/*&<&'options'&>
26176 .cindex "&%verify%& ACL condition"
26177 .cindex "&ACL;" "verifying sender in the header"
26178 .cindex "header lines" "verifying the sender in"
26179 .cindex "sender" "verifying in header"
26180 .cindex "verifying" "sender in header"
26181 This condition is relevant only in an ACL that is run after a message has been
26182 received, that is, in an ACL specified by &%acl_smtp_data%& or
26183 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
26184 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
26185 is loosely thought of as a &"sender"& address (hence the name of the test).
26186 However, an address that appears in one of these headers need not be an address
26187 that accepts bounce messages; only sender addresses in envelopes are required
26188 to accept bounces. Therefore, if you use the callout option on this check, you
26189 might want to arrange for a non-empty address in the MAIL command.
26190
26191 Details of address verification and the options are given later, starting at
26192 section &<<SECTaddressverification>>& (callouts are described in section
26193 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
26194 condition to restrict it to bounce messages only:
26195 .code
26196 deny senders = :
26197 message = A valid sender header is required for bounces
26198 !verify = header_sender
26199 .endd
26200
26201 .vitem &*verify&~=&~header_syntax*&
26202 .cindex "&%verify%& ACL condition"
26203 .cindex "&ACL;" "verifying header syntax"
26204 .cindex "header lines" "verifying syntax"
26205 .cindex "verifying" "header syntax"
26206 This condition is relevant only in an ACL that is run after a message has been
26207 received, that is, in an ACL specified by &%acl_smtp_data%& or
26208 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
26209 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
26210 and &'Bcc:'&). Unqualified addresses (local parts without domains) are
26211 permitted only in locally generated messages and from hosts that match
26212 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
26213 appropriate.
26214
26215 Note that this condition is a syntax check only. However, a common spamming
26216 ploy used to be to send syntactically invalid headers such as
26217 .code
26218 To: @
26219 .endd
26220 and this condition can be used to reject such messages, though they are not as
26221 common as they used to be.
26222
26223 .vitem &*verify&~=&~helo*&
26224 .cindex "&%verify%& ACL condition"
26225 .cindex "&ACL;" "verifying HELO/EHLO"
26226 .cindex "HELO" "verifying"
26227 .cindex "EHLO" "verifying"
26228 .cindex "verifying" "EHLO"
26229 .cindex "verifying" "HELO"
26230 This condition is true if a HELO or EHLO command has been received from the
26231 client host, and its contents have been verified. If there has been no previous
26232 attempt to verify the HELO/EHLO contents, it is carried out when this
26233 condition is encountered. See the description of the &%helo_verify_hosts%& and
26234 &%helo_try_verify_hosts%& options for details of how to request verification
26235 independently of this condition.
26236
26237 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
26238 option), this condition is always true.
26239
26240
26241 .vitem &*verify&~=&~not_blind*&
26242 .cindex "verifying" "not blind"
26243 .cindex "bcc recipients, verifying none"
26244 This condition checks that there are no blind (bcc) recipients in the message.
26245 Every envelope recipient must appear either in a &'To:'& header line or in a
26246 &'Cc:'& header line for this condition to be true. Local parts are checked
26247 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
26248 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
26249 used only in a DATA or non-SMTP ACL.
26250
26251 There are, of course, many legitimate messages that make use of blind (bcc)
26252 recipients. This check should not be used on its own for blocking messages.
26253
26254
26255 .vitem &*verify&~=&~recipient/*&<&'options'&>
26256 .cindex "&%verify%& ACL condition"
26257 .cindex "&ACL;" "verifying recipient"
26258 .cindex "recipient" "verifying"
26259 .cindex "verifying" "recipient"
26260 .vindex "&$address_data$&"
26261 This condition is relevant only after a RCPT command. It verifies the current
26262 recipient. Details of address verification are given later, starting at section
26263 &<<SECTaddressverification>>&. After a recipient has been verified, the value
26264 of &$address_data$& is the last value that was set while routing the address.
26265 This applies even if the verification fails. When an address that is being
26266 verified is redirected to a single address, verification continues with the new
26267 address, and in that case, the subsequent value of &$address_data$& is the
26268 value for the child address.
26269
26270 .vitem &*verify&~=&~reverse_host_lookup*&
26271 .cindex "&%verify%& ACL condition"
26272 .cindex "&ACL;" "verifying host reverse lookup"
26273 .cindex "host" "verifying reverse lookup"
26274 This condition ensures that a verified host name has been looked up from the IP
26275 address of the client host. (This may have happened already if the host name
26276 was needed for checking a host list, or if the host matched &%host_lookup%&.)
26277 Verification ensures that the host name obtained from a reverse DNS lookup, or
26278 one of its aliases, does, when it is itself looked up in the DNS, yield the
26279 original IP address.
26280
26281 If this condition is used for a locally generated message (that is, when there
26282 is no client host involved), it always succeeds.
26283
26284 .vitem &*verify&~=&~sender/*&<&'options'&>
26285 .cindex "&%verify%& ACL condition"
26286 .cindex "&ACL;" "verifying sender"
26287 .cindex "sender" "verifying"
26288 .cindex "verifying" "sender"
26289 This condition is relevant only after a MAIL or RCPT command, or after a
26290 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
26291 the message's sender is empty (that is, this is a bounce message), the
26292 condition is true. Otherwise, the sender address is verified.
26293
26294 .vindex "&$address_data$&"
26295 .vindex "&$sender_address_data$&"
26296 If there is data in the &$address_data$& variable at the end of routing, its
26297 value is placed in &$sender_address_data$& at the end of verification. This
26298 value can be used in subsequent conditions and modifiers in the same ACL
26299 statement. It does not persist after the end of the current statement. If you
26300 want to preserve the value for longer, you can save it in an ACL variable.
26301
26302 Details of verification are given later, starting at section
26303 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
26304 to avoid doing it more than once per message.
26305
26306 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
26307 .cindex "&%verify%& ACL condition"
26308 This is a variation of the previous option, in which a modified address is
26309 verified as a sender.
26310 .endlist
26311
26312
26313
26314 .section "Using DNS lists" "SECTmorednslists"
26315 .cindex "DNS list" "in ACL"
26316 .cindex "black list (DNS)"
26317 .cindex "&ACL;" "testing a DNS list"
26318 In its simplest form, the &%dnslists%& condition tests whether the calling host
26319 is on at least one of a number of DNS lists by looking up the inverted IP
26320 address in one or more DNS domains. For example, if the calling host's IP
26321 address is 192.168.62.43, and the ACL statement is
26322 .code
26323 deny dnslists = blackholes.mail-abuse.org : \
26324 dialups.mail-abuse.org
26325 .endd
26326 the following records are looked up:
26327 .code
26328 43.62.168.192.blackholes.mail-abuse.org
26329 43.62.168.192.dialups.mail-abuse.org
26330 .endd
26331 As soon as Exim finds an existing DNS record, processing of the list stops.
26332 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
26333 to test that a host is on more than one list (an &"and"& conjunction), you can
26334 use two separate conditions:
26335 .code
26336 deny dnslists = blackholes.mail-abuse.org
26337 dnslists = dialups.mail-abuse.org
26338 .endd
26339 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
26340 behaves as if the host does not match the list item, that is, as if the DNS
26341 record does not exist. If there are further items in the DNS list, they are
26342 processed.
26343
26344 This is usually the required action when &%dnslists%& is used with &%deny%&
26345 (which is the most common usage), because it prevents a DNS failure from
26346 blocking mail. However, you can change this behaviour by putting one of the
26347 following special items in the list:
26348 .display
26349 &`+include_unknown `& behave as if the item is on the list
26350 &`+exclude_unknown `& behave as if the item is not on the list (default)
26351 &`+defer_unknown `& give a temporary error
26352 .endd
26353 .cindex "&`+include_unknown`&"
26354 .cindex "&`+exclude_unknown`&"
26355 .cindex "&`+defer_unknown`&"
26356 Each of these applies to any subsequent items on the list. For example:
26357 .code
26358 deny dnslists = +defer_unknown : foo.bar.example
26359 .endd
26360 Testing the list of domains stops as soon as a match is found. If you want to
26361 warn for one list and block for another, you can use two different statements:
26362 .code
26363 deny dnslists = blackholes.mail-abuse.org
26364 warn message = X-Warn: sending host is on dialups list
26365 dnslists = dialups.mail-abuse.org
26366 .endd
26367 DNS list lookups are cached by Exim for the duration of the SMTP session,
26368 so a lookup based on the IP address is done at most once for any incoming
26369 connection. Exim does not share information between multiple incoming
26370 connections (but your local name server cache should be active).
26371
26372
26373
26374 .section "Specifying the IP address for a DNS list lookup" "SECID201"
26375 .cindex "DNS list" "keyed by explicit IP address"
26376 By default, the IP address that is used in a DNS list lookup is the IP address
26377 of the calling host. However, you can specify another IP address by listing it
26378 after the domain name, introduced by a slash. For example:
26379 .code
26380 deny dnslists = black.list.tld/192.168.1.2
26381 .endd
26382 This feature is not very helpful with explicit IP addresses; it is intended for
26383 use with IP addresses that are looked up, for example, the IP addresses of the
26384 MX hosts or nameservers of an email sender address. For an example, see section
26385 &<<SECTmulkeyfor>>& below.
26386
26387
26388
26389
26390 .section "DNS lists keyed on domain names" "SECID202"
26391 .cindex "DNS list" "keyed by domain name"
26392 There are some lists that are keyed on domain names rather than inverted IP
26393 addresses (see for example the &'domain based zones'& link at
26394 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
26395 with these lists. You can change the name that is looked up in a DNS list by
26396 listing it after the domain name, introduced by a slash. For example,
26397 .code
26398 deny message = Sender's domain is listed at $dnslist_domain
26399 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
26400 .endd
26401 This particular example is useful only in ACLs that are obeyed after the
26402 RCPT or DATA commands, when a sender address is available. If (for
26403 example) the message's sender is &'user@tld.example'& the name that is looked
26404 up by this example is
26405 .code
26406 tld.example.dsn.rfc-ignorant.org
26407 .endd
26408 A single &%dnslists%& condition can contain entries for both names and IP
26409 addresses. For example:
26410 .code
26411 deny dnslists = sbl.spamhaus.org : \
26412 dsn.rfc-ignorant.org/$sender_address_domain
26413 .endd
26414 The first item checks the sending host's IP address; the second checks a domain
26415 name. The whole condition is true if either of the DNS lookups succeeds.
26416
26417
26418
26419
26420 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
26421 .cindex "DNS list" "multiple keys for"
26422 The syntax described above for looking up explicitly-defined values (either
26423 names or IP addresses) in a DNS blacklist is a simplification. After the domain
26424 name for the DNS list, what follows the slash can in fact be a list of items.
26425 As with all lists in Exim, the default separator is a colon. However, because
26426 this is a sublist within the list of DNS blacklist domains, it is necessary
26427 either to double the separators like this:
26428 .code
26429 dnslists = black.list.tld/name.1::name.2
26430 .endd
26431 or to change the separator character, like this:
26432 .code
26433 dnslists = black.list.tld/<;name.1;name.2
26434 .endd
26435 If an item in the list is an IP address, it is inverted before the DNS
26436 blacklist domain is appended. If it is not an IP address, no inversion
26437 occurs. Consider this condition:
26438 .code
26439 dnslists = black.list.tld/<;192.168.1.2;a.domain
26440 .endd
26441 The DNS lookups that occur are:
26442 .code
26443 2.1.168.192.black.list.tld
26444 a.domain.black.list.tld
26445 .endd
26446 Once a DNS record has been found (that matches a specific IP return
26447 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
26448 are done. If there is a temporary DNS error, the rest of the sublist of domains
26449 or IP addresses is tried. A temporary error for the whole dnslists item occurs
26450 only if no other DNS lookup in this sublist succeeds. In other words, a
26451 successful lookup for any of the items in the sublist overrides a temporary
26452 error for a previous item.
26453
26454 The ability to supply a list of items after the slash is in some sense just a
26455 syntactic convenience. These two examples have the same effect:
26456 .code
26457 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
26458 dnslists = black.list.tld/a.domain::b.domain
26459 .endd
26460 However, when the data for the list is obtained from a lookup, the second form
26461 is usually much more convenient. Consider this example:
26462 .code
26463 deny message = The mail servers for the domain \
26464 $sender_address_domain \
26465 are listed at $dnslist_domain ($dnslist_value); \
26466 see $dnslist_text.
26467 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
26468 ${lookup dnsdb {>|mxh=\
26469 $sender_address_domain} }} }
26470 .endd
26471 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
26472 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
26473 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
26474 of expanding the condition might be something like this:
26475 .code
26476 dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|...
26477 .endd
26478 Thus, this example checks whether or not the IP addresses of the sender
26479 domain's mail servers are on the Spamhaus black list.
26480
26481 The key that was used for a successful DNS list lookup is put into the variable
26482 &$dnslist_matched$& (see section &<<SECID204>>&).
26483
26484
26485
26486
26487 .section "Data returned by DNS lists" "SECID203"
26488 .cindex "DNS list" "data returned from"
26489 DNS lists are constructed using address records in the DNS. The original RBL
26490 just used the address 127.0.0.1 on the right hand side of each record, but the
26491 RBL+ list and some other lists use a number of values with different meanings.
26492 The values used on the RBL+ list are:
26493 .display
26494 127.1.0.1 RBL
26495 127.1.0.2 DUL
26496 127.1.0.3 DUL and RBL
26497 127.1.0.4 RSS
26498 127.1.0.5 RSS and RBL
26499 127.1.0.6 RSS and DUL
26500 127.1.0.7 RSS and DUL and RBL
26501 .endd
26502 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
26503 different values. Some DNS lists may return more than one address record;
26504 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
26505
26506
26507 .section "Variables set from DNS lists" "SECID204"
26508 .cindex "expansion" "variables, set from DNS list"
26509 .cindex "DNS list" "variables set from"
26510 .vindex "&$dnslist_domain$&"
26511 .vindex "&$dnslist_matched$&"
26512 .vindex "&$dnslist_text$&"
26513 .vindex "&$dnslist_value$&"
26514 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
26515 the name of the overall domain that matched (for example,
26516 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
26517 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
26518 the DNS record. When the key is an IP address, it is not reversed in
26519 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
26520 cases, for example:
26521 .code
26522 deny dnslists = spamhaus.example
26523 .endd
26524 the key is also available in another variable (in this case,
26525 &$sender_host_address$&). In more complicated cases, however, this is not true.
26526 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
26527 might generate a dnslists lookup like this:
26528 .code
26529 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
26530 .endd
26531 If this condition succeeds, the value in &$dnslist_matched$& might be
26532 &`192.168.6.7`& (for example).
26533
26534 If more than one address record is returned by the DNS lookup, all the IP
26535 addresses are included in &$dnslist_value$&, separated by commas and spaces.
26536 The variable &$dnslist_text$& contains the contents of any associated TXT
26537 record. For lists such as RBL+ the TXT record for a merged entry is often not
26538 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
26539 information.
26540
26541 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
26542 &-- although these appear before the condition in the ACL, they are not
26543 expanded until after it has failed. For example:
26544 .code
26545 deny hosts = !+local_networks
26546 message = $sender_host_address is listed \
26547 at $dnslist_domain
26548 dnslists = rbl-plus.mail-abuse.example
26549 .endd
26550
26551
26552
26553 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
26554 .cindex "DNS list" "matching specific returned data"
26555 You can add an equals sign and an IP address after a &%dnslists%& domain name
26556 in order to restrict its action to DNS records with a matching right hand side.
26557 For example,
26558 .code
26559 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
26560 .endd
26561 rejects only those hosts that yield 127.0.0.2. Without this additional data,
26562 any address record is considered to be a match. For the moment, we assume
26563 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
26564 describes how multiple records are handled.
26565
26566 More than one IP address may be given for checking, using a comma as a
26567 separator. These are alternatives &-- if any one of them matches, the
26568 &%dnslists%& condition is true. For example:
26569 .code
26570 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
26571 .endd
26572 If you want to specify a constraining address list and also specify names or IP
26573 addresses to be looked up, the constraining address list must be specified
26574 first. For example:
26575 .code
26576 deny dnslists = dsn.rfc-ignorant.org\
26577 =127.0.0.2/$sender_address_domain
26578 .endd
26579
26580 If the character &`&&`& is used instead of &`=`&, the comparison for each
26581 listed IP address is done by a bitwise &"and"& instead of by an equality test.
26582 In other words, the listed addresses are used as bit masks. The comparison is
26583 true if all the bits in the mask are present in the address that is being
26584 tested. For example:
26585 .code
26586 dnslists = a.b.c&0.0.0.3
26587 .endd
26588 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
26589 want to test whether one bit or another bit is present (as opposed to both
26590 being present), you must use multiple values. For example:
26591 .code
26592 dnslists = a.b.c&0.0.0.1,0.0.0.2
26593 .endd
26594 matches if the final component of the address is an odd number or two times
26595 an odd number.
26596
26597
26598
26599 .section "Negated DNS matching conditions" "SECID205"
26600 You can supply a negative list of IP addresses as part of a &%dnslists%&
26601 condition. Whereas
26602 .code
26603 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
26604 .endd
26605 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
26606 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
26607 .code
26608 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
26609 .endd
26610 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
26611 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
26612 words, the result of the test is inverted if an exclamation mark appears before
26613 the &`=`& (or the &`&&`&) sign.
26614
26615 &*Note*&: This kind of negation is not the same as negation in a domain,
26616 host, or address list (which is why the syntax is different).
26617
26618 If you are using just one list, the negation syntax does not gain you much. The
26619 previous example is precisely equivalent to
26620 .code
26621 deny dnslists = a.b.c
26622 !dnslists = a.b.c=127.0.0.2,127.0.0.3
26623 .endd
26624 However, if you are using multiple lists, the negation syntax is clearer.
26625 Consider this example:
26626 .code
26627 deny dnslists = sbl.spamhaus.org : \
26628 list.dsbl.org : \
26629 dnsbl.njabl.org!=127.0.0.3 : \
26630 relays.ordb.org
26631 .endd
26632 Using only positive lists, this would have to be:
26633 .code
26634 deny dnslists = sbl.spamhaus.org : \
26635 list.dsbl.org
26636 deny dnslists = dnsbl.njabl.org
26637 !dnslists = dnsbl.njabl.org=127.0.0.3
26638 deny dnslists = relays.ordb.org
26639 .endd
26640 which is less clear, and harder to maintain.
26641
26642
26643
26644
26645 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
26646 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
26647 thereby providing more than one IP address. When an item in a &%dnslists%& list
26648 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
26649 the match to specific results from the DNS lookup, there are two ways in which
26650 the checking can be handled. For example, consider the condition:
26651 .code
26652 dnslists = a.b.c=127.0.0.1
26653 .endd
26654 What happens if the DNS lookup for the incoming IP address yields both
26655 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
26656 condition true because at least one given value was found, or is it false
26657 because at least one of the found values was not listed? And how does this
26658 affect negated conditions? Both possibilities are provided for with the help of
26659 additional separators &`==`& and &`=&&`&.
26660
26661 .ilist
26662 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
26663 IP addresses matches one of the listed addresses. For the example above, the
26664 condition is true because 127.0.0.1 matches.
26665 .next
26666 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
26667 looked up IP addresses matches one of the listed addresses. If the condition is
26668 changed to:
26669 .code
26670 dnslists = a.b.c==127.0.0.1
26671 .endd
26672 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
26673 false because 127.0.0.2 is not listed. You would need to have:
26674 .code
26675 dnslists = a.b.c==127.0.0.1,127.0.0.2
26676 .endd
26677 for the condition to be true.
26678 .endlist
26679
26680 When &`!`& is used to negate IP address matching, it inverts the result, giving
26681 the precise opposite of the behaviour above. Thus:
26682 .ilist
26683 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
26684 addresses matches one of the listed addresses. Consider:
26685 .code
26686 dnslists = a.b.c!&0.0.0.1
26687 .endd
26688 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
26689 false because 127.0.0.1 matches.
26690 .next
26691 If &`!==`& or &`!=&&`& is used, the condition is true there is at least one
26692 looked up IP address that does not match. Consider:
26693 .code
26694 dnslists = a.b.c!=&0.0.0.1
26695 .endd
26696 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
26697 true, because 127.0.0.2 does not match. You would need to have:
26698 .code
26699 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
26700 .endd
26701 for the condition to be false.
26702 .endlist
26703 When the DNS lookup yields only a single IP address, there is no difference
26704 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
26705
26706
26707
26708
26709 .section "Detailed information from merged DNS lists" "SECTmordetinf"
26710 .cindex "DNS list" "information from merged"
26711 When the facility for restricting the matching IP values in a DNS list is used,
26712 the text from the TXT record that is set in &$dnslist_text$& may not reflect
26713 the true reason for rejection. This happens when lists are merged and the IP
26714 address in the A record is used to distinguish them; unfortunately there is
26715 only one TXT record. One way round this is not to use merged lists, but that
26716 can be inefficient because it requires multiple DNS lookups where one would do
26717 in the vast majority of cases when the host of interest is not on any of the
26718 lists.
26719
26720 A less inefficient way of solving this problem is available. If
26721 two domain names, comma-separated, are given, the second is used first to
26722 do an initial check, making use of any IP value restrictions that are set.
26723 If there is a match, the first domain is used, without any IP value
26724 restrictions, to get the TXT record. As a byproduct of this, there is also
26725 a check that the IP being tested is indeed on the first list. The first
26726 domain is the one that is put in &$dnslist_domain$&. For example:
26727 .code
26728 reject message = \
26729 rejected because $sender_host_address is blacklisted \
26730 at $dnslist_domain\n$dnslist_text
26731 dnslists = \
26732 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
26733 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
26734 .endd
26735 For the first blacklist item, this starts by doing a lookup in
26736 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
26737 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
26738 value, and as long as something is found, it looks for the corresponding TXT
26739 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
26740 The second blacklist item is processed similarly.
26741
26742 If you are interested in more than one merged list, the same list must be
26743 given several times, but because the results of the DNS lookups are cached,
26744 the DNS calls themselves are not repeated. For example:
26745 .code
26746 reject dnslists = \
26747 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
26748 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
26749 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
26750 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
26751 .endd
26752 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
26753 values matches (or if no record is found), this is the only lookup that is
26754 done. Only if there is a match is one of the more specific lists consulted.
26755
26756
26757
26758 .section "DNS lists and IPv6" "SECTmorednslistslast"
26759 .cindex "IPv6" "DNS black lists"
26760 .cindex "DNS list" "IPv6 usage"
26761 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
26762 nibble by nibble. For example, if the calling host's IP address is
26763 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
26764 .code
26765 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
26766 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
26767 .endd
26768 (split over two lines here to fit on the page). Unfortunately, some of the DNS
26769 lists contain wildcard records, intended for IPv4, that interact badly with
26770 IPv6. For example, the DNS entry
26771 .code
26772 *.3.some.list.example. A 127.0.0.1
26773 .endd
26774 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
26775 Unfortunately, it also matches the entire 3::/4 IPv6 network.
26776
26777 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
26778 &%condition%& condition, as in this example:
26779 .code
26780 deny condition = ${if isip4{$sender_host_address}}
26781 dnslists = some.list.example
26782 .endd
26783
26784 .section "Rate limiting incoming messages" "SECTratelimiting"
26785 .cindex "rate limiting" "client sending"
26786 .cindex "limiting client sending rates"
26787 .oindex "&%smtp_ratelimit_*%&"
26788 The &%ratelimit%& ACL condition can be used to measure and control the rate at
26789 which clients can send email. This is more powerful than the
26790 &%smtp_ratelimit_*%& options, because those options control the rate of
26791 commands in a single SMTP session only, whereas the &%ratelimit%& condition
26792 works across all connections (concurrent and sequential) from the same client
26793 host. The syntax of the &%ratelimit%& condition is:
26794 .display
26795 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
26796 .endd
26797 If the average client sending rate is less than &'m'& messages per time
26798 period &'p'& then the condition is false; otherwise it is true.
26799
26800 As a side-effect, the &%ratelimit%& condition sets the expansion variable
26801 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
26802 configured value of &'m'&, and &$sender_rate_period$& to the configured value
26803 of &'p'&.
26804
26805 The parameter &'p'& is the smoothing time constant, in the form of an Exim
26806 time interval, for example, &`8h`& for eight hours. A larger time constant
26807 means that it takes Exim longer to forget a client's past behaviour. The
26808 parameter &'m'& is the maximum number of messages that a client is permitted to
26809 send in each time interval. It also specifies the number of messages permitted
26810 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
26811 constant, you can allow a client to send more messages in a burst without
26812 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
26813 both small, messages must be sent at an even rate.
26814
26815 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
26816 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
26817 when deploying the &%ratelimit%& ACL condition. The script prints usage
26818 instructions when it is run with no arguments.
26819
26820 The key is used to look up the data for calculating the client's average
26821 sending rate. This data is stored in Exim's spool directory, alongside the
26822 retry and other hints databases. The default key is &$sender_host_address$&,
26823 which means Exim computes the sending rate of each client host IP address.
26824 By changing the key you can change how Exim identifies clients for the purpose
26825 of ratelimiting. For example, to limit the sending rate of each authenticated
26826 user, independent of the computer they are sending from, set the key to
26827 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
26828 example, &$authenticated_id$& is only meaningful if the client has
26829 authenticated (which you can check with the &%authenticated%& ACL condition).
26830
26831 The lookup key does not have to identify clients: If you want to limit the
26832 rate at which a recipient receives messages, you can use the key
26833 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
26834 ACL.
26835
26836 Internally, Exim appends the smoothing constant &'p'& and the options onto the
26837 lookup key because they alter the meaning of the stored data. This is not true
26838 for the limit &'m'&, so you can alter the configured maximum rate and Exim will
26839 still remember clients' past behaviour, but if you alter the other ratelimit
26840 parameters Exim forgets past behaviour.
26841
26842 Each &%ratelimit%& condition can have up to three options. One option
26843 specifies what Exim measures the rate of, and the second specifies how Exim
26844 handles excessively fast clients. The third option can be &`noupdate`&, to
26845 disable updating of the ratelimiting database (see section &<<rearatdat>>&).
26846 The options are separated by a slash, like the other parameters. They may
26847 appear in any order.
26848
26849 .section "Ratelimit options for what is being measured" "ratoptmea"
26850 The &%per_conn%& option limits the client's connection rate.
26851
26852 The &%per_mail%& option limits the client's rate of sending messages. This is
26853 the default if none of the &%per_*%& options is specified.
26854
26855 The &%per_byte%& option limits the sender's email bandwidth. Note that it is
26856 best to use this option in the DATA ACL; if it is used in an earlier ACL it
26857 relies on the SIZE parameter specified by the client in its MAIL command,
26858 which may be inaccurate or completely missing. You can follow the limit &'m'&
26859 in the configuration with K, M, or G to specify limits in kilobytes,
26860 megabytes, or gigabytes, respectively.
26861
26862 The &%per_rcpt%& option causes Exim to limit the rate at which
26863 recipients are accepted. To be effective, it would need to be used in
26864 either the &%acl_smtp_rcpt%& or the &%acl_not_smtp%& ACL. In the
26865 &%acl_smtp_rcpt%& ACL, the number of recipients is incremented by one.
26866 In the case of a locally submitted message in the &%acl_not_smtp%& ACL,
26867 the number of recipients is incremented by the &%$recipients_count%&
26868 for the entire message. Note that in either case the rate limiting
26869 engine will see a message with many recipients as a large high-speed
26870 burst.
26871
26872 The &%per_cmd%& option causes Exim to recompute the rate every time the
26873 condition is processed. This can be used to limit the SMTP command rate.
26874 This command is essentially an alias of &%per_rcpt%& to make it clear
26875 that the effect is to limit the rate at which individual commands,
26876 rather than recipients, are accepted.
26877
26878 .section "Ratelimit options for handling fast clients" "ratophanfas"
26879 If a client's average rate is greater than the maximum, the rate limiting
26880 engine can react in two possible ways, depending on the presence of the
26881 &%strict%& or &%leaky%& options. This is independent of the other
26882 counter-measures (such as rejecting the message) that may be specified by the
26883 rest of the ACL. The default mode is leaky, which avoids a sender's
26884 over-aggressive retry rate preventing it from getting any email through.
26885
26886 The &%strict%& option means that the client's recorded rate is always
26887 updated. The effect of this is that Exim measures the client's average rate
26888 of attempts to send email, which can be much higher than the maximum it is
26889 actually allowed. If the client is over the limit it may be subjected to
26890 counter-measures by the ACL until it slows down below the maximum rate. If
26891 the client stops attempting to send email for the time specified in the &'p'&
26892 parameter then its computed rate will decay exponentially to 37% of its peak
26893 value. You can work out the time (the number of smoothing periods) that a
26894 client is subjected to counter-measures after an over-limit burst with this
26895 formula:
26896 .code
26897 ln(peakrate/maxrate)
26898 .endd
26899 The &%leaky%& (default) option means that the client's recorded rate is not
26900 updated if it is above the limit. The effect of this is that Exim measures the
26901 client's average rate of successfully sent email, which cannot be greater than
26902 the maximum allowed. If the client is over the limit it may suffer some
26903 counter-measures (as specified in the ACL), but it will still be able to send
26904 email at the configured maximum rate, whatever the rate of its attempts. This
26905 is generally the better choice if you have clients that retry automatically.
26906
26907 .section "Using rate limiting" "useratlim"
26908 Exim's other ACL facilities are used to define what counter-measures are taken
26909 when the rate limit is exceeded. This might be anything from logging a warning
26910 (for example, while measuring existing sending rates in order to define
26911 policy), through time delays to slow down fast senders, up to rejecting the
26912 message. For example:
26913 .code
26914 # Log all senders' rates
26915 warn ratelimit = 0 / 1h / strict
26916 log_message = Sender rate $sender_rate / $sender_rate_period
26917
26918 # Slow down fast senders; note the need to truncate $sender_rate
26919 # at the decimal point.
26920 warn ratelimit = 100 / 1h / per_rcpt / strict
26921 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
26922 $sender_rate_limit }s
26923
26924 # Keep authenticated users under control
26925 deny authenticated = *
26926 ratelimit = 100 / 1d / strict / $authenticated_id
26927
26928 # System-wide rate limit
26929 defer message = Sorry, too busy. Try again later.
26930 ratelimit = 10 / 1s / $primary_hostname
26931
26932 # Restrict incoming rate from each host, with a default
26933 # set using a macro and special cases looked up in a table.
26934 defer message = Sender rate exceeds $sender_rate_limit \
26935 messages per $sender_rate_period
26936 ratelimit = ${lookup {$sender_host_address} \
26937 cdb {DB/ratelimits.cdb} \
26938 {$value} {RATELIMIT} }
26939 .endd
26940 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
26941 especially with the &%per_rcpt%& option, you may suffer from a performance
26942 bottleneck caused by locking on the ratelimit hints database. Apart from
26943 making your ACLs less complicated, you can reduce the problem by using a
26944 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
26945 this means that Exim will lose its hints data after a reboot (including retry
26946 hints, the callout cache, and ratelimit data).
26947
26948
26949 .section "Reading ratelimit data without updating" "rearatdat"
26950 .cindex "rate limitint" "reading data without updating"
26951 If the &%noupdate%& option is present on a &%ratelimit%& ACL condition, Exim
26952 computes the rate and checks the limit as normal, but it does not update the
26953 saved data. This means that, in relevant ACLs, it is possible to lookup the
26954 existence of a specified (or auto-generated) ratelimit key without incrementing
26955 the ratelimit counter for that key. In order for this to be useful, another ACL
26956 entry must set the rate for the same key (otherwise it will always be zero).
26957 For example:
26958 .code
26959 acl_check_connect:
26960 deny ratelimit = 100 / 5m / strict / noupdate
26961 log_message = RATE: $sender_rate/$sender_rate_period \
26962 (max $sender_rate_limit)
26963 .endd
26964 .display
26965 &'... some other logic and tests...'&
26966 .endd
26967 .code
26968 acl_check_mail:
26969 warn ratelimit = 100 / 5m / strict / per_cmd
26970 condition = ${if le{$sender_rate}{$sender_rate_limit}}
26971 logwrite = RATE UPDATE: $sender_rate/$sender_rate_period \
26972 (max $sender_rate_limit)
26973 .endd
26974 In this example, the rate is tested and used to deny access (when it is too
26975 high) in the connect ACL, but the actual computation of the remembered rate
26976 happens later, on a per-command basis, in another ACL.
26977
26978
26979
26980 .section "Address verification" "SECTaddressverification"
26981 .cindex "verifying address" "options for"
26982 .cindex "policy control" "address verification"
26983 Several of the &%verify%& conditions described in section
26984 &<<SECTaclconditions>>& cause addresses to be verified. Section
26985 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
26986 The verification conditions can be followed by options that modify the
26987 verification process. The options are separated from the keyword and from each
26988 other by slashes, and some of them contain parameters. For example:
26989 .code
26990 verify = sender/callout
26991 verify = recipient/defer_ok/callout=10s,defer_ok
26992 .endd
26993 The first stage of address verification, which always happens, is to run the
26994 address through the routers, in &"verify mode"&. Routers can detect the
26995 difference between verification and routing for delivery, and their actions can
26996 be varied by a number of generic options such as &%verify%& and &%verify_only%&
26997 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
26998 The available options are as follows:
26999
27000 .ilist
27001 If the &%callout%& option is specified, successful routing to one or more
27002 remote hosts is followed by a &"callout"& to those hosts as an additional
27003 check. Callouts and their sub-options are discussed in the next section.
27004 .next
27005 If there is a defer error while doing verification routing, the ACL
27006 normally returns &"defer"&. However, if you include &%defer_ok%& in the
27007 options, the condition is forced to be true instead. Note that this is a main
27008 verification option as well as a suboption for callouts.
27009 .next
27010 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
27011 discusses the reporting of sender address verification failures.
27012 .next
27013 The &%success_on_redirect%& option causes verification always to succeed
27014 immediately after a successful redirection. By default, if a redirection
27015 generates just one address, that address is also verified. See further
27016 discussion in section &<<SECTredirwhilveri>>&.
27017 .endlist
27018
27019 .cindex "verifying address" "differentiating failures"
27020 .vindex "&$recipient_verify_failure$&"
27021 .vindex "&$sender_verify_failure$&"
27022 .vindex "&$acl_verify_message$&"
27023 After an address verification failure, &$acl_verify_message$& contains the
27024 error message that is associated with the failure. It can be preserved by
27025 coding like this:
27026 .code
27027 warn !verify = sender
27028 set acl_m0 = $acl_verify_message
27029 .endd
27030 If you are writing your own custom rejection message or log message when
27031 denying access, you can use this variable to include information about the
27032 verification failure.
27033
27034 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
27035 appropriate) contains one of the following words:
27036
27037 .ilist
27038 &%qualify%&: The address was unqualified (no domain), and the message
27039 was neither local nor came from an exempted host.
27040 .next
27041 &%route%&: Routing failed.
27042 .next
27043 &%mail%&: Routing succeeded, and a callout was attempted; rejection
27044 occurred at or before the MAIL command (that is, on initial
27045 connection, HELO, or MAIL).
27046 .next
27047 &%recipient%&: The RCPT command in a callout was rejected.
27048 .next
27049 &%postmaster%&: The postmaster check in a callout was rejected.
27050 .endlist
27051
27052 The main use of these variables is expected to be to distinguish between
27053 rejections of MAIL and rejections of RCPT in callouts.
27054
27055
27056
27057
27058 .section "Callout verification" "SECTcallver"
27059 .cindex "verifying address" "by callout"
27060 .cindex "callout" "verification"
27061 .cindex "SMTP" "callout verification"
27062 For non-local addresses, routing verifies the domain, but is unable to do any
27063 checking of the local part. There are situations where some means of verifying
27064 the local part is desirable. One way this can be done is to make an SMTP
27065 &'callback'& to a delivery host for the sender address or a &'callforward'& to
27066 a subsequent host for a recipient address, to see if the host accepts the
27067 address. We use the term &'callout'& to cover both cases. Note that for a
27068 sender address, the callback is not to the client host that is trying to
27069 deliver the message, but to one of the hosts that accepts incoming mail for the
27070 sender's domain.
27071
27072 Exim does not do callouts by default. If you want them to happen, you must
27073 request them by setting appropriate options on the &%verify%& condition, as
27074 described below. This facility should be used with care, because it can add a
27075 lot of resource usage to the cost of verifying an address. However, Exim does
27076 cache the results of callouts, which helps to reduce the cost. Details of
27077 caching are in section &<<SECTcallvercache>>&.
27078
27079 Recipient callouts are usually used only between hosts that are controlled by
27080 the same administration. For example, a corporate gateway host could use
27081 callouts to check for valid recipients on an internal mailserver. A successful
27082 callout does not guarantee that a real delivery to the address would succeed;
27083 on the other hand, a failing callout does guarantee that a delivery would fail.
27084
27085 If the &%callout%& option is present on a condition that verifies an address, a
27086 second stage of verification occurs if the address is successfully routed to
27087 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
27088 &(manualroute)& router, where the router specifies the hosts. However, if a
27089 router that does not set up hosts routes to an &(smtp)& transport with a
27090 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
27091 &%hosts_override%& set, its hosts are always used, whether or not the router
27092 supplies a host list.
27093
27094 The port that is used is taken from the transport, if it is specified and is a
27095 remote transport. (For routers that do verification only, no transport need be
27096 specified.) Otherwise, the default SMTP port is used. If a remote transport
27097 specifies an outgoing interface, this is used; otherwise the interface is not
27098 specified. Likewise, the text that is used for the HELO command is taken from
27099 the transport's &%helo_data%& option; if there is no transport, the value of
27100 &$smtp_active_hostname$& is used.
27101
27102 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
27103 test whether a bounce message could be delivered to the sender address. The
27104 following SMTP commands are sent:
27105 .display
27106 &`HELO `&<&'local host name'&>
27107 &`MAIL FROM:<>`&
27108 &`RCPT TO:`&<&'the address to be tested'&>
27109 &`QUIT`&
27110 .endd
27111 LHLO is used instead of HELO if the transport's &%protocol%& option is
27112 set to &"lmtp"&.
27113
27114 A recipient callout check is similar. By default, it also uses an empty address
27115 for the sender. This default is chosen because most hosts do not make use of
27116 the sender address when verifying a recipient. Using the same address means
27117 that a single cache entry can be used for each recipient. Some sites, however,
27118 do make use of the sender address when verifying. These are catered for by the
27119 &%use_sender%& and &%use_postmaster%& options, described in the next section.
27120
27121 If the response to the RCPT command is a 2&'xx'& code, the verification
27122 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
27123 Exim tries the next host, if any. If there is a problem with all the remote
27124 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
27125 &%callout%& option is given, in which case the condition is forced to succeed.
27126
27127 .cindex "SMTP" "output flushing, disabling for callout"
27128 A callout may take a little time. For this reason, Exim normally flushes SMTP
27129 output before performing a callout in an ACL, to avoid unexpected timeouts in
27130 clients when the SMTP PIPELINING extension is in use. The flushing can be
27131 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
27132
27133
27134
27135
27136 .section "Additional parameters for callouts" "CALLaddparcall"
27137 .cindex "callout" "additional parameters for"
27138 The &%callout%& option can be followed by an equals sign and a number of
27139 optional parameters, separated by commas. For example:
27140 .code
27141 verify = recipient/callout=10s,defer_ok
27142 .endd
27143 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
27144 separate verify options, is retained for backwards compatibility, but is now
27145 deprecated. The additional parameters for &%callout%& are as follows:
27146
27147
27148 .vlist
27149 .vitem <&'a&~time&~interval'&>
27150 .cindex "callout" "timeout, specifying"
27151 This specifies the timeout that applies for the callout attempt to each host.
27152 For example:
27153 .code
27154 verify = sender/callout=5s
27155 .endd
27156 The default is 30 seconds. The timeout is used for each response from the
27157 remote host. It is also used for the initial connection, unless overridden by
27158 the &%connect%& parameter.
27159
27160
27161 .vitem &*connect&~=&~*&<&'time&~interval'&>
27162 .cindex "callout" "connection timeout, specifying"
27163 This parameter makes it possible to set a different (usually smaller) timeout
27164 for making the SMTP connection. For example:
27165 .code
27166 verify = sender/callout=5s,connect=1s
27167 .endd
27168 If not specified, this timeout defaults to the general timeout value.
27169
27170 .vitem &*defer_ok*&
27171 .cindex "callout" "defer, action on"
27172 When this parameter is present, failure to contact any host, or any other kind
27173 of temporary error, is treated as success by the ACL. However, the cache is not
27174 updated in this circumstance.
27175
27176 .vitem &*fullpostmaster*&
27177 .cindex "callout" "full postmaster check"
27178 This operates like the &%postmaster%& option (see below), but if the check for
27179 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
27180 accordance with the specification in RFC 2821. The RFC states that the
27181 unqualified address &'postmaster'& should be accepted.
27182
27183
27184 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
27185 .cindex "callout" "sender when verifying header"
27186 When verifying addresses in header lines using the &%header_sender%&
27187 verification option, Exim behaves by default as if the addresses are envelope
27188 sender addresses from a message. Callout verification therefore tests to see
27189 whether a bounce message could be delivered, by using an empty address in the
27190 MAIL command. However, it is arguable that these addresses might never be used
27191 as envelope senders, and could therefore justifiably reject bounce messages
27192 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
27193 address to use in the MAIL command. For example:
27194 .code
27195 require verify = header_sender/callout=mailfrom=abcd@x.y.z
27196 .endd
27197 This parameter is available only for the &%header_sender%& verification option.
27198
27199
27200 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
27201 .cindex "callout" "overall timeout, specifying"
27202 This parameter sets an overall timeout for performing a callout verification.
27203 For example:
27204 .code
27205 verify = sender/callout=5s,maxwait=30s
27206 .endd
27207 This timeout defaults to four times the callout timeout for individual SMTP
27208 commands. The overall timeout applies when there is more than one host that can
27209 be tried. The timeout is checked before trying the next host. This prevents
27210 very long delays if there are a large number of hosts and all are timing out
27211 (for example, when network connections are timing out).
27212
27213
27214 .vitem &*no_cache*&
27215 .cindex "callout" "cache, suppressing"
27216 .cindex "caching callout, suppressing"
27217 When this parameter is given, the callout cache is neither read nor updated.
27218
27219 .vitem &*postmaster*&
27220 .cindex "callout" "postmaster; checking"
27221 When this parameter is set, a successful callout check is followed by a similar
27222 check for the local part &'postmaster'& at the same domain. If this address is
27223 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
27224 the postmaster check is recorded in a cache record; if it is a failure, this is
27225 used to fail subsequent callouts for the domain without a connection being
27226 made, until the cache record expires.
27227
27228 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
27229 The postmaster check uses an empty sender in the MAIL command by default.
27230 You can use this parameter to do a postmaster check using a different address.
27231 For example:
27232 .code
27233 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
27234 .endd
27235 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
27236 one overrides. The &%postmaster%& parameter is equivalent to this example:
27237 .code
27238 require verify = sender/callout=postmaster_mailfrom=
27239 .endd
27240 &*Warning*&: The caching arrangements for postmaster checking do not take
27241 account of the sender address. It is assumed that either the empty address or
27242 a fixed non-empty address will be used. All that Exim remembers is that the
27243 postmaster check for the domain succeeded or failed.
27244
27245
27246 .vitem &*random*&
27247 .cindex "callout" "&""random""& check"
27248 When this parameter is set, before doing the normal callout check, Exim does a
27249 check for a &"random"& local part at the same domain. The local part is not
27250 really random &-- it is defined by the expansion of the option
27251 &%callout_random_local_part%&, which defaults to
27252 .code
27253 $primary_host_name-$tod_epoch-testing
27254 .endd
27255 The idea here is to try to determine whether the remote host accepts all local
27256 parts without checking. If it does, there is no point in doing callouts for
27257 specific local parts. If the &"random"& check succeeds, the result is saved in
27258 a cache record, and used to force the current and subsequent callout checks to
27259 succeed without a connection being made, until the cache record expires.
27260
27261 .vitem &*use_postmaster*&
27262 .cindex "callout" "sender for recipient check"
27263 This parameter applies to recipient callouts only. For example:
27264 .code
27265 deny !verify = recipient/callout=use_postmaster
27266 .endd
27267 .vindex "&$qualify_domain$&"
27268 It causes a non-empty postmaster address to be used in the MAIL command when
27269 performing the callout for the recipient, and also for a &"random"& check if
27270 that is configured. The local part of the address is &`postmaster`& and the
27271 domain is the contents of &$qualify_domain$&.
27272
27273 .vitem &*use_sender*&
27274 This option applies to recipient callouts only. For example:
27275 .code
27276 require verify = recipient/callout=use_sender
27277 .endd
27278 It causes the message's actual sender address to be used in the MAIL
27279 command when performing the callout, instead of an empty address. There is no
27280 need to use this option unless you know that the called hosts make use of the
27281 sender when checking recipients. If used indiscriminately, it reduces the
27282 usefulness of callout caching.
27283 .endlist
27284
27285 If you use any of the parameters that set a non-empty sender for the MAIL
27286 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
27287 &%use_sender%&), you should think about possible loops. Recipient checking is
27288 usually done between two hosts that are under the same management, and the host
27289 that receives the callouts is not normally configured to do callouts itself.
27290 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
27291 these circumstances.
27292
27293 However, if you use a non-empty sender address for a callout to an arbitrary
27294 host, there is the likelihood that the remote host will itself initiate a
27295 callout check back to your host. As it is checking what appears to be a message
27296 sender, it is likely to use an empty address in MAIL, thus avoiding a
27297 callout loop. However, to be on the safe side it would be best to set up your
27298 own ACLs so that they do not do sender verification checks when the recipient
27299 is the address you use for header sender or postmaster callout checking.
27300
27301 Another issue to think about when using non-empty senders for callouts is
27302 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
27303 by the sender/recipient combination; thus, for any given recipient, many more
27304 actual callouts are performed than when an empty sender or postmaster is used.
27305
27306
27307
27308
27309 .section "Callout caching" "SECTcallvercache"
27310 .cindex "hints database" "callout cache"
27311 .cindex "callout" "cache, description of"
27312 .cindex "caching" "callout"
27313 Exim caches the results of callouts in order to reduce the amount of resources
27314 used, unless you specify the &%no_cache%& parameter with the &%callout%&
27315 option. A hints database called &"callout"& is used for the cache. Two
27316 different record types are used: one records the result of a callout check for
27317 a specific address, and the other records information that applies to the
27318 entire domain (for example, that it accepts the local part &'postmaster'&).
27319
27320 When an original callout fails, a detailed SMTP error message is given about
27321 the failure. However, for subsequent failures use the cache data, this message
27322 is not available.
27323
27324 The expiry times for negative and positive address cache records are
27325 independent, and can be set by the global options &%callout_negative_expire%&
27326 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
27327
27328 If a host gives a negative response to an SMTP connection, or rejects any
27329 commands up to and including
27330 .code
27331 MAIL FROM:<>
27332 .endd
27333 (but not including the MAIL command with a non-empty address),
27334 any callout attempt is bound to fail. Exim remembers such failures in a
27335 domain cache record, which it uses to fail callouts for the domain without
27336 making new connections, until the domain record times out. There are two
27337 separate expiry times for domain cache records:
27338 &%callout_domain_negative_expire%& (default 3h) and
27339 &%callout_domain_positive_expire%& (default 7d).
27340
27341 Domain records expire when the negative expiry time is reached if callouts
27342 cannot be made for the domain, or if the postmaster check failed.
27343 Otherwise, they expire when the positive expiry time is reached. This
27344 ensures that, for example, a host that stops accepting &"random"& local parts
27345 will eventually be noticed.
27346
27347 The callout caching mechanism is based on the domain of the address that is
27348 being tested. If the domain routes to several hosts, it is assumed that their
27349 behaviour will be the same.
27350
27351
27352
27353 .section "Sender address verification reporting" "SECTsenaddver"
27354 .cindex "verifying" "suppressing error details"
27355 See section &<<SECTaddressverification>>& for a general discussion of
27356 verification. When sender verification fails in an ACL, the details of the
27357 failure are given as additional output lines before the 550 response to the
27358 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
27359 you might see:
27360 .code
27361 MAIL FROM:<xyz@abc.example>
27362 250 OK
27363 RCPT TO:<pqr@def.example>
27364 550-Verification failed for <xyz@abc.example>
27365 550-Called: 192.168.34.43
27366 550-Sent: RCPT TO:<xyz@abc.example>
27367 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
27368 550 Sender verification failed
27369 .endd
27370 If more than one RCPT command fails in the same way, the details are given
27371 only for the first of them. However, some administrators do not want to send
27372 out this much information. You can suppress the details by adding
27373 &`/no_details`& to the ACL statement that requests sender verification. For
27374 example:
27375 .code
27376 verify = sender/no_details
27377 .endd
27378
27379 .section "Redirection while verifying" "SECTredirwhilveri"
27380 .cindex "verifying" "redirection while"
27381 .cindex "address redirection" "while verifying"
27382 A dilemma arises when a local address is redirected by aliasing or forwarding
27383 during verification: should the generated addresses themselves be verified,
27384 or should the successful expansion of the original address be enough to verify
27385 it? By default, Exim takes the following pragmatic approach:
27386
27387 .ilist
27388 When an incoming address is redirected to just one child address, verification
27389 continues with the child address, and if that fails to verify, the original
27390 verification also fails.
27391 .next
27392 When an incoming address is redirected to more than one child address,
27393 verification does not continue. A success result is returned.
27394 .endlist
27395
27396 This seems the most reasonable behaviour for the common use of aliasing as a
27397 way of redirecting different local parts to the same mailbox. It means, for
27398 example, that a pair of alias entries of the form
27399 .code
27400 A.Wol: aw123
27401 aw123: :fail: Gone away, no forwarding address
27402 .endd
27403 work as expected, with both local parts causing verification failure. When a
27404 redirection generates more than one address, the behaviour is more like a
27405 mailing list, where the existence of the alias itself is sufficient for
27406 verification to succeed.
27407
27408 It is possible, however, to change the default behaviour so that all successful
27409 redirections count as successful verifications, however many new addresses are
27410 generated. This is specified by the &%success_on_redirect%& verification
27411 option. For example:
27412 .code
27413 require verify = recipient/success_on_redirect/callout=10s
27414 .endd
27415 In this example, verification succeeds if a router generates a new address, and
27416 the callout does not occur, because no address was routed to a remote host.
27417
27418 When verification is being tested via the &%-bv%& option, the treatment of
27419 redirections is as just described, unless the &%-v%& or any debugging option is
27420 also specified. In that case, full verification is done for every generated
27421 address and a report is output for each of them.
27422
27423
27424
27425 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
27426 .cindex "CSA" "verifying"
27427 Client SMTP Authorization is a system that allows a site to advertise
27428 which machines are and are not permitted to send email. This is done by placing
27429 special SRV records in the DNS; these are looked up using the client's HELO
27430 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
27431 Authorization checks in Exim are performed by the ACL condition:
27432 .code
27433 verify = csa
27434 .endd
27435 This fails if the client is not authorized. If there is a DNS problem, or if no
27436 valid CSA SRV record is found, or if the client is authorized, the condition
27437 succeeds. These three cases can be distinguished using the expansion variable
27438 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
27439 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
27440 be likely to cause problems for legitimate email.
27441
27442 The error messages produced by the CSA code include slightly more
27443 detail. If &$csa_status$& is &"defer"&, this may be because of problems
27444 looking up the CSA SRV record, or problems looking up the CSA target
27445 address record. There are four reasons for &$csa_status$& being &"fail"&:
27446
27447 .ilist
27448 The client's host name is explicitly not authorized.
27449 .next
27450 The client's IP address does not match any of the CSA target IP addresses.
27451 .next
27452 The client's host name is authorized but it has no valid target IP addresses
27453 (for example, the target's addresses are IPv6 and the client is using IPv4).
27454 .next
27455 The client's host name has no CSA SRV record but a parent domain has asserted
27456 that all subdomains must be explicitly authorized.
27457 .endlist
27458
27459 The &%csa%& verification condition can take an argument which is the domain to
27460 use for the DNS query. The default is:
27461 .code
27462 verify = csa/$sender_helo_name
27463 .endd
27464 This implementation includes an extension to CSA. If the query domain
27465 is an address literal such as [192.0.2.95], or if it is a bare IP
27466 address, Exim searches for CSA SRV records in the reverse DNS as if
27467 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
27468 meaningful to say:
27469 .code
27470 verify = csa/$sender_host_address
27471 .endd
27472 In fact, this is the check that Exim performs if the client does not say HELO.
27473 This extension can be turned off by setting the main configuration option
27474 &%dns_csa_use_reverse%& to be false.
27475
27476 If a CSA SRV record is not found for the domain itself, a search
27477 is performed through its parent domains for a record which might be
27478 making assertions about subdomains. The maximum depth of this search is limited
27479 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
27480 default. Exim does not look for CSA SRV records in a top level domain, so the
27481 default settings handle HELO domains as long as seven
27482 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
27483 of legitimate HELO domains.
27484
27485 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
27486 direct SRV lookups, this is not sufficient because of the extra parent domain
27487 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
27488 addresses into lookups in the reverse DNS space. The result of a successful
27489 lookup such as:
27490 .code
27491 ${lookup dnsdb {csa=$sender_helo_name}}
27492 .endd
27493 has two space-separated fields: an authorization code and a target host name.
27494 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
27495 authorization required but absent, or &"?"& for unknown.
27496
27497
27498
27499
27500 .section "Bounce address tag validation" "SECTverifyPRVS"
27501 .cindex "BATV, verifying"
27502 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
27503 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
27504 Genuine incoming bounce messages should therefore always be addressed to
27505 recipients that have a valid tag. This scheme is a way of detecting unwanted
27506 bounce messages caused by sender address forgeries (often called &"collateral
27507 spam"&), because the recipients of such messages do not include valid tags.
27508
27509 There are two expansion items to help with the implementation of the BATV
27510 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
27511 the original envelope sender address by using a simple key to add a hash of the
27512 address and some time-based randomizing information. The &%prvs%& expansion
27513 item creates a signed address, and the &%prvscheck%& expansion item checks one.
27514 The syntax of these expansion items is described in section
27515 &<<SECTexpansionitems>>&.
27516
27517 As an example, suppose the secret per-address keys are stored in an MySQL
27518 database. A query to look up the key for an address could be defined as a macro
27519 like this:
27520 .code
27521 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
27522 WHERE sender='${quote_mysql:$prvscheck_address}'\
27523 }{$value}}
27524 .endd
27525 Suppose also that the senders who make use of BATV are defined by an address
27526 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
27527 use this:
27528 .code
27529 # Bounces: drop unsigned addresses for BATV senders
27530 deny message = This address does not send an unsigned reverse path
27531 senders = :
27532 recipients = +batv_senders
27533
27534 # Bounces: In case of prvs-signed address, check signature.
27535 deny message = Invalid reverse path signature.
27536 senders = :
27537 condition = ${prvscheck {$local_part@$domain}\
27538 {PRVSCHECK_SQL}{1}}
27539 !condition = $prvscheck_result
27540 .endd
27541 The first statement rejects recipients for bounce messages that are addressed
27542 to plain BATV sender addresses, because it is known that BATV senders do not
27543 send out messages with plain sender addresses. The second statement rejects
27544 recipients that are prvs-signed, but with invalid signatures (either because
27545 the key is wrong, or the signature has timed out).
27546
27547 A non-prvs-signed address is not rejected by the second statement, because the
27548 &%prvscheck%& expansion yields an empty string if its first argument is not a
27549 prvs-signed address, thus causing the &%condition%& condition to be false. If
27550 the first argument is a syntactically valid prvs-signed address, the yield is
27551 the third string (in this case &"1"&), whether or not the cryptographic and
27552 timeout checks succeed. The &$prvscheck_result$& variable contains the result
27553 of the checks (empty for failure, &"1"& for success).
27554
27555 There are two more issues you must consider when implementing prvs-signing.
27556 Firstly, you need to ensure that prvs-signed addresses are not blocked by your
27557 ACLs. A prvs-signed address contains a slash character, but the default Exim
27558 configuration contains this statement in the RCPT ACL:
27559 .code
27560 deny message = Restricted characters in address
27561 domains = +local_domains
27562 local_parts = ^[.] : ^.*[@%!/|]
27563 .endd
27564 This is a conservative rule that blocks local parts that contain slashes. You
27565 should remove the slash in the last line.
27566
27567 Secondly, you have to ensure that the routers accept prvs-signed addresses and
27568 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
27569 router to remove the signature with a configuration along these lines:
27570 .code
27571 batv_redirect:
27572 driver = redirect
27573 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
27574 .endd
27575 This works because, if the third argument of &%prvscheck%& is empty, the result
27576 of the expansion of a prvs-signed address is the decoded value of the original
27577 address. This router should probably be the first of your routers that handles
27578 local addresses.
27579
27580 To create BATV-signed addresses in the first place, a transport of this form
27581 can be used:
27582 .code
27583 external_smtp_batv:
27584 driver = smtp
27585 return_path = ${prvs {$return_path} \
27586 {${lookup mysql{SELECT \
27587 secret FROM batv_prvs WHERE \
27588 sender='${quote_mysql:$sender_address}'} \
27589 {$value}fail}}}
27590 .endd
27591 If no key can be found for the existing return path, no signing takes place.
27592
27593
27594
27595 .section "Using an ACL to control relaying" "SECTrelaycontrol"
27596 .cindex "&ACL;" "relay control"
27597 .cindex "relaying" "control by ACL"
27598 .cindex "policy control" "relay control"
27599 An MTA is said to &'relay'& a message if it receives it from some host and
27600 delivers it directly to another host as a result of a remote address contained
27601 within it. Redirecting a local address via an alias or forward file and then
27602 passing the message on to another host is not relaying,
27603 .cindex "&""percent hack""&"
27604 but a redirection as a result of the &"percent hack"& is.
27605
27606 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
27607 A host which is acting as a gateway or an MX backup is concerned with incoming
27608 relaying from arbitrary hosts to a specific set of domains. On the other hand,
27609 a host which is acting as a smart host for a number of clients is concerned
27610 with outgoing relaying from those clients to the Internet at large. Often the
27611 same host is fulfilling both functions,
27612 . ///
27613 . as illustrated in the diagram below,
27614 . ///
27615 but in principle these two kinds of relaying are entirely independent. What is
27616 not wanted is the transmission of mail from arbitrary remote hosts through your
27617 system to arbitrary domains.
27618
27619
27620 You can implement relay control by means of suitable statements in the ACL that
27621 runs for each RCPT command. For convenience, it is often easiest to use
27622 Exim's named list facility to define the domains and hosts involved. For
27623 example, suppose you want to do the following:
27624
27625 .ilist
27626 Deliver a number of domains to mailboxes on the local host (or process them
27627 locally in some other way). Let's say these are &'my.dom1.example'& and
27628 &'my.dom2.example'&.
27629 .next
27630 Relay mail for a number of other domains for which you are the secondary MX.
27631 These might be &'friend1.example'& and &'friend2.example'&.
27632 .next
27633 Relay mail from the hosts on your local LAN, to whatever domains are involved.
27634 Suppose your LAN is 192.168.45.0/24.
27635 .endlist
27636
27637
27638 In the main part of the configuration, you put the following definitions:
27639 .code
27640 domainlist local_domains = my.dom1.example : my.dom2.example
27641 domainlist relay_domains = friend1.example : friend2.example
27642 hostlist relay_hosts = 192.168.45.0/24
27643 .endd
27644 Now you can use these definitions in the ACL that is run for every RCPT
27645 command:
27646 .code
27647 acl_check_rcpt:
27648 accept domains = +local_domains : +relay_domains
27649 accept hosts = +relay_hosts
27650 .endd
27651 The first statement accepts any RCPT command that contains an address in
27652 the local or relay domains. For any other domain, control passes to the second
27653 statement, which accepts the command only if it comes from one of the relay
27654 hosts. In practice, you will probably want to make your ACL more sophisticated
27655 than this, for example, by including sender and recipient verification. The
27656 default configuration includes a more comprehensive example, which is described
27657 in chapter &<<CHAPdefconfil>>&.
27658
27659
27660
27661 .section "Checking a relay configuration" "SECTcheralcon"
27662 .cindex "relaying" "checking control of"
27663 You can check the relay characteristics of your configuration in the same way
27664 that you can test any ACL behaviour for an incoming SMTP connection, by using
27665 the &%-bh%& option to run a fake SMTP session with which you interact.
27666
27667 For specifically testing for unwanted relaying, the host
27668 &'relay-test.mail-abuse.org'& provides a useful service. If you telnet to this
27669 host from the host on which Exim is running, using the normal telnet port, you
27670 will see a normal telnet connection message and then quite a long delay. Be
27671 patient. The remote host is making an SMTP connection back to your host, and
27672 trying a number of common probes to test for open relay vulnerability. The
27673 results of the tests will eventually appear on your terminal.
27674 .ecindex IIDacl
27675
27676
27677
27678 . ////////////////////////////////////////////////////////////////////////////
27679 . ////////////////////////////////////////////////////////////////////////////
27680
27681 .chapter "Content scanning at ACL time" "CHAPexiscan"
27682 .scindex IIDcosca "content scanning" "at ACL time"
27683 The extension of Exim to include content scanning at ACL time, formerly known
27684 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
27685 was integrated into the main source for Exim release 4.50, and Tom continues to
27686 maintain it. Most of the wording of this chapter is taken from Tom's
27687 specification.
27688
27689 It is also possible to scan the content of messages at other times. The
27690 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
27691 scanning after all the ACLs have run. A transport filter can be used to scan
27692 messages at delivery time (see the &%transport_filter%& option, described in
27693 chapter &<<CHAPtransportgeneric>>&).
27694
27695 If you want to include the ACL-time content-scanning features when you compile
27696 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
27697 &_Local/Makefile_&. When you do that, the Exim binary is built with:
27698
27699 .ilist
27700 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
27701 for all MIME parts for SMTP and non-SMTP messages, respectively.
27702 .next
27703 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
27704 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
27705 run at the end of message reception (the &%acl_smtp_data%& ACL).
27706 .next
27707 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
27708 of messages, or parts of messages, for debugging purposes.
27709 .next
27710 Additional expansion variables that are set in the new ACL and by the new
27711 conditions.
27712 .next
27713 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
27714 .endlist
27715
27716 There is another content-scanning configuration option for &_Local/Makefile_&,
27717 called WITH_OLD_DEMIME. If this is set, the old, deprecated &%demime%& ACL
27718 condition is compiled, in addition to all the other content-scanning features.
27719
27720 Content-scanning is continually evolving, and new features are still being
27721 added. While such features are still unstable and liable to incompatible
27722 changes, they are made available in Exim by setting options whose names begin
27723 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
27724 this manual. You can find out about them by reading the file called
27725 &_doc/experimental.txt_&.
27726
27727 All the content-scanning facilities work on a MBOX copy of the message that is
27728 temporarily created in a file called:
27729 .display
27730 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
27731 .endd
27732 The &_.eml_& extension is a friendly hint to virus scanners that they can
27733 expect an MBOX-like structure inside that file. The file is created when the
27734 first content scanning facility is called. Subsequent calls to content
27735 scanning conditions open the same file again. The directory is recursively
27736 removed when the &%acl_smtp_data%& ACL has finished running, unless
27737 .code
27738 control = no_mbox_unspool
27739 .endd
27740 has been encountered. When the MIME ACL decodes files, they are put into the
27741 same directory by default.
27742
27743
27744
27745 .section "Scanning for viruses" "SECTscanvirus"
27746 .cindex "virus scanning"
27747 .cindex "content scanning" "for viruses"
27748 .cindex "content scanning" "the &%malware%& condition"
27749 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
27750 It supports a &"generic"& interface to scanners called via the shell, and
27751 specialized interfaces for &"daemon"& type virus scanners, which are resident
27752 in memory and thus are much faster.
27753
27754 .oindex "&%av_scanner%&"
27755 You can set the &%av_scanner%& option in first part of the Exim configuration
27756 file to specify which scanner to use, together with any additional options that
27757 are needed. The basic syntax is as follows:
27758 .display
27759 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
27760 .endd
27761 If you do not set &%av_scanner%&, it defaults to
27762 .code
27763 av_scanner = sophie:/var/run/sophie
27764 .endd
27765 If the value of &%av_scanner%& starts with dollar character, it is expanded
27766 before use. The following scanner types are supported in this release:
27767
27768 .vlist
27769 .vitem &%aveserver%&
27770 .cindex "virus scanners" "Kaspersky"
27771 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
27772 at &url(http://www.kaspersky.com). This scanner type takes one option,
27773 which is the path to the daemon's UNIX socket. The default is shown in this
27774 example:
27775 .code
27776 av_scanner = aveserver:/var/run/aveserver
27777 .endd
27778
27779 .vitem &%clamd%&
27780 .cindex "virus scanners" "clamd"
27781 This daemon-type scanner is GPL and free. You can get it at
27782 &url(http://www.clamav.net/). Some older versions of clamd do not seem to
27783 unpack MIME containers, so it used to be recommended to unpack MIME attachments
27784 in the MIME ACL. This no longer believed to be necessary. One option is
27785 required: either the path and name of a UNIX socket file, or a hostname or IP
27786 number, and a port, separated by space, as in the second of these examples:
27787 .code
27788 av_scanner = clamd:/opt/clamd/socket
27789 av_scanner = clamd:192.168.2.100 1234
27790 .endd
27791 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
27792 contributing the code for this scanner.
27793
27794 .vitem &%cmdline%&
27795 .cindex "virus scanners" "command line interface"
27796 This is the keyword for the generic command line scanner interface. It can be
27797 used to attach virus scanners that are invoked from the shell. This scanner
27798 type takes 3 mandatory options:
27799
27800 .olist
27801 The full path and name of the scanner binary, with all command line options,
27802 and a placeholder (&`%s`&) for the directory to scan.
27803
27804 .next
27805 A regular expression to match against the STDOUT and STDERR output of the
27806 virus scanner. If the expression matches, a virus was found. You must make
27807 absolutely sure that this expression matches on &"virus found"&. This is called
27808 the &"trigger"& expression.
27809
27810 .next
27811 Another regular expression, containing exactly one pair of parentheses, to
27812 match the name of the virus found in the scanners output. This is called the
27813 &"name"& expression.
27814 .endlist olist
27815
27816 For example, Sophos Sweep reports a virus on a line like this:
27817 .code
27818 Virus 'W32/Magistr-B' found in file ./those.bat
27819 .endd
27820 For the trigger expression, we can match the phrase &"found in file"&. For the
27821 name expression, we want to extract the W32/Magistr-B string, so we can match
27822 for the single quotes left and right of it. Altogether, this makes the
27823 configuration setting:
27824 .code
27825 av_scanner = cmdline:\
27826 /path/to/sweep -ss -all -rec -archive %s:\
27827 found in file:'(.+)'
27828 .endd
27829 .vitem &%drweb%&
27830 .cindex "virus scanners" "DrWeb"
27831 The DrWeb daemon scanner (&url(http://www.sald.com/)) interface takes one
27832 argument, either a full path to a UNIX socket, or an IP address and port
27833 separated by white space, as in these examples:
27834 .code
27835 av_scanner = drweb:/var/run/drwebd.sock
27836 av_scanner = drweb:192.168.2.20 31337
27837 .endd
27838 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
27839 is used. Thanks to Alex Miller for contributing the code for this scanner.
27840
27841 .vitem &%fsecure%&
27842 .cindex "virus scanners" "F-Secure"
27843 The F-Secure daemon scanner (&url(http://www.f-secure.com)) takes one
27844 argument which is the path to a UNIX socket. For example:
27845 .code
27846 av_scanner = fsecure:/path/to/.fsav
27847 .endd
27848 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
27849 Thelmen for contributing the code for this scanner.
27850
27851 .vitem &%kavdaemon%&
27852 .cindex "virus scanners" "Kaspersky"
27853 This is the scanner daemon of Kaspersky Version 4. This version of the
27854 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
27855 scanner type takes one option, which is the path to the daemon's UNIX socket.
27856 For example:
27857 .code
27858 av_scanner = kavdaemon:/opt/AVP/AvpCtl
27859 .endd
27860 The default path is &_/var/run/AvpCtl_&.
27861
27862 .vitem &%mksd%&
27863 .cindex "virus scanners" "mksd"
27864 This is a daemon type scanner that is aimed mainly at Polish users, though some
27865 parts of documentation are now available in English. You can get it at
27866 &url(http://linux.mks.com.pl/). The only option for this scanner type is
27867 the maximum number of processes used simultaneously to scan the attachments,
27868 provided that the demime facility is employed and also provided that mksd has
27869 been run with at least the same number of child processes. For example:
27870 .code
27871 av_scanner = mksd:2
27872 .endd
27873 You can safely omit this option (the default value is 1).
27874
27875 .vitem &%sophie%&
27876 .cindex "virus scanners" "Sophos and Sophie"
27877 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
27878 You can get Sophie at &url(http://www.clanfield.info/sophie/). The only option
27879 for this scanner type is the path to the UNIX socket that Sophie uses for
27880 client communication. For example:
27881 .code
27882 av_scanner = sophie:/tmp/sophie
27883 .endd
27884 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
27885 the option.
27886 .endlist
27887
27888 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
27889 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
27890 ACL.
27891
27892 The &%av_scanner%& option is expanded each time &%malware%& is called. This
27893 makes it possible to use different scanners. See further below for an example.
27894 The &%malware%& condition caches its results, so when you use it multiple times
27895 for the same message, the actual scanning process is only carried out once.
27896 However, using expandable items in &%av_scanner%& disables this caching, in
27897 which case each use of the &%malware%& condition causes a new scan of the
27898 message.
27899
27900 The &%malware%& condition takes a right-hand argument that is expanded before
27901 use. It can then be one of
27902
27903 .ilist
27904 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
27905 The condition succeeds if a virus was found, and fail otherwise. This is the
27906 recommended usage.
27907 .next
27908 &"false"& or &"0"& or an empty string, in which case no scanning is done and
27909 the condition fails immediately.
27910 .next
27911 A regular expression, in which case the message is scanned for viruses. The
27912 condition succeeds if a virus is found and its name matches the regular
27913 expression. This allows you to take special actions on certain types of virus.
27914 .endlist
27915
27916 You can append &`/defer_ok`& to the &%malware%& condition to accept messages
27917 even if there is a problem with the virus scanner. Otherwise, such a problem
27918 causes the ACL to defer.
27919
27920 .vindex "&$malware_name$&"
27921 When a virus is found, the condition sets up an expansion variable called
27922 &$malware_name$& that contains the name of the virus. You can use it in a
27923 &%message%& modifier that specifies the error returned to the sender, and/or in
27924 logging data.
27925
27926 If your virus scanner cannot unpack MIME and TNEF containers itself, you should
27927 use the &%demime%& condition (see section &<<SECTdemimecond>>&) before the
27928 &%malware%& condition.
27929
27930 Here is a very simple scanning example:
27931 .code
27932 deny message = This message contains malware ($malware_name)
27933 demime = *
27934 malware = *
27935 .endd
27936 The next example accepts messages when there is a problem with the scanner:
27937 .code
27938 deny message = This message contains malware ($malware_name)
27939 demime = *
27940 malware = */defer_ok
27941 .endd
27942 The next example shows how to use an ACL variable to scan with both sophie and
27943 aveserver. It assumes you have set:
27944 .code
27945 av_scanner = $acl_m0
27946 .endd
27947 in the main Exim configuration.
27948 .code
27949 deny message = This message contains malware ($malware_name)
27950 set acl_m0 = sophie
27951 malware = *
27952
27953 deny message = This message contains malware ($malware_name)
27954 set acl_m0 = aveserver
27955 malware = *
27956 .endd
27957
27958
27959 .section "Scanning with SpamAssassin" "SECTscanspamass"
27960 .cindex "content scanning" "for spam"
27961 .cindex "spam scanning"
27962 .cindex "SpamAssassin"
27963 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
27964 score and a report for the message. You can get SpamAssassin at
27965 &url(http://www.spamassassin.org), or, if you have a working Perl
27966 installation, you can use CPAN by running:
27967 .code
27968 perl -MCPAN -e 'install Mail::SpamAssassin'
27969 .endd
27970 SpamAssassin has its own set of configuration files. Please review its
27971 documentation to see how you can tweak it. The default installation should work
27972 nicely, however.
27973
27974 .oindex "&%spamd_address%&"
27975 After having installed and configured SpamAssassin, start the &%spamd%& daemon.
27976 By default, it listens on 127.0.0.1, TCP port 783. If you use another host or
27977 port for &%spamd%&, you must set the &%spamd_address%& option in the global
27978 part of the Exim configuration as follows (example):
27979 .code
27980 spamd_address = 192.168.99.45 387
27981 .endd
27982 You do not need to set this option if you use the default. As of version 2.60,
27983 &%spamd%& also supports communication over UNIX sockets. If you want to use
27984 these, supply &%spamd_address%& with an absolute file name instead of a
27985 address/port pair:
27986 .code
27987 spamd_address = /var/run/spamd_socket
27988 .endd
27989 You can have multiple &%spamd%& servers to improve scalability. These can
27990 reside on other hardware reachable over the network. To specify multiple
27991 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
27992 option, separated with colons:
27993 .code
27994 spamd_address = 192.168.2.10 783 : \
27995 192.168.2.11 783 : \
27996 192.168.2.12 783
27997 .endd
27998 Up to 32 &%spamd%& servers are supported. The servers are queried in a random
27999 fashion. When a server fails to respond to the connection attempt, all other
28000 servers are tried until one succeeds. If no server responds, the &%spam%&
28001 condition defers.
28002
28003 &*Warning*&: It is not possible to use the UNIX socket connection method with
28004 multiple &%spamd%& servers.
28005
28006 The &%spamd_address%& variable is expanded before use if it starts with
28007 a dollar sign. In this case, the expansion may return a string that is
28008 used as the list so that multiple spamd servers can be the result of an
28009 expansion.
28010
28011 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
28012 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
28013 .code
28014 deny message = This message was classified as SPAM
28015 spam = joe
28016 .endd
28017 The right-hand side of the &%spam%& condition specifies a name. This is
28018 relevant if you have set up multiple SpamAssassin profiles. If you do not want
28019 to scan using a specific profile, but rather use the SpamAssassin system-wide
28020 default profile, you can scan for an unknown name, or simply use &"nobody"&.
28021 However, you must put something on the right-hand side.
28022
28023 The name allows you to use per-domain or per-user antispam profiles in
28024 principle, but this is not straightforward in practice, because a message may
28025 have multiple recipients, not necessarily all in the same domain. Because the
28026 &%spam%& condition has to be called from a DATA ACL in order to be able to
28027 read the contents of the message, the variables &$local_part$& and &$domain$&
28028 are not set.
28029
28030 The right-hand side of the &%spam%& condition is expanded before being used, so
28031 you can put lookups or conditions there. When the right-hand side evaluates to
28032 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
28033
28034
28035 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
28036 large ones may cause significant performance degradation. As most spam messages
28037 are quite small, it is recommended that you do not scan the big ones. For
28038 example:
28039 .code
28040 deny message = This message was classified as SPAM
28041 condition = ${if < {$message_size}{10K}}
28042 spam = nobody
28043 .endd
28044
28045 The &%spam%& condition returns true if the threshold specified in the user's
28046 SpamAssassin profile has been matched or exceeded. If you want to use the
28047 &%spam%& condition for its side effects (see the variables below), you can make
28048 it always return &"true"& by appending &`:true`& to the username.
28049
28050 .cindex "spam scanning" "returned variables"
28051 When the &%spam%& condition is run, it sets up a number of expansion
28052 variables. With the exception of &$spam_score_int$&, these are usable only
28053 within ACLs; their values are not retained with the message and so cannot be
28054 used at delivery time.
28055
28056 .vlist
28057 .vitem &$spam_score$&
28058 The spam score of the message, for example &"3.4"& or &"30.5"&. This is useful
28059 for inclusion in log or reject messages.
28060
28061 .vitem &$spam_score_int$&
28062 The spam score of the message, multiplied by ten, as an integer value. For
28063 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
28064 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
28065 The integer value is useful for numeric comparisons in
28066 conditions. This variable is special; its value is saved with the message, and
28067 written to Exim's spool file. This means that it can be used during the whole
28068 life of the message on your Exim system, in particular, in routers or
28069 transports during the later delivery phase.
28070
28071 .vitem &$spam_bar$&
28072 A string consisting of a number of &"+"& or &"-"& characters, representing the
28073 integer part of the spam score value. A spam score of 4.4 would have a
28074 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
28075 headers, since MUAs can match on such strings.
28076
28077 .vitem &$spam_report$&
28078 A multiline text table, containing the full SpamAssassin report for the
28079 message. Useful for inclusion in headers or reject messages.
28080 .endlist
28081
28082 The &%spam%& condition caches its results unless expansion in
28083 spamd_address was used. If you call it again with the same user name, it
28084 does not scan again, but rather returns the same values as before.
28085
28086 The &%spam%& condition returns DEFER if there is any error while running
28087 the message through SpamAssassin or if the expansion of spamd_address
28088 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
28089 statement block), append &`/defer_ok`& to the right-hand side of the
28090 spam condition, like this:
28091 .code
28092 deny message = This message was classified as SPAM
28093 spam = joe/defer_ok
28094 .endd
28095 This causes messages to be accepted even if there is a problem with &%spamd%&.
28096
28097 Here is a longer, commented example of the use of the &%spam%&
28098 condition:
28099 .code
28100 # put headers in all messages (no matter if spam or not)
28101 warn spam = nobody:true
28102 add_header = X-Spam-Score: $spam_score ($spam_bar)
28103 add_header = X-Spam-Report: $spam_report
28104
28105 # add second subject line with *SPAM* marker when message
28106 # is over threshold
28107 warn spam = nobody
28108 add_header = Subject: *SPAM* $h_Subject:
28109
28110 # reject spam at high scores (> 12)
28111 deny message = This message scored $spam_score spam points.
28112 spam = nobody:true
28113 condition = ${if >{$spam_score_int}{120}{1}{0}}
28114 .endd
28115
28116
28117
28118 .section "Scanning MIME parts" "SECTscanmimepart"
28119 .cindex "content scanning" "MIME parts"
28120 .cindex "MIME content scanning"
28121 .oindex "&%acl_smtp_mime%&"
28122 .oindex "&%acl_not_smtp_mime%&"
28123 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
28124 each MIME part of an SMTP message, including multipart types, in the sequence
28125 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
28126 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
28127 options may both refer to the same ACL if you want the same processing in both
28128 cases.
28129
28130 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
28131 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
28132 the case of a non-SMTP message. However, a MIME ACL is called only if the
28133 message contains a &'Content-Type:'& header line. When a call to a MIME
28134 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
28135 result code is sent to the client. In the case of an SMTP message, the
28136 &%acl_smtp_data%& ACL is not called when this happens.
28137
28138 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
28139 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
28140 condition to match against the raw MIME part. You can also use the
28141 &%mime_regex%& condition to match against the decoded MIME part (see section
28142 &<<SECTscanregex>>&).
28143
28144 At the start of a MIME ACL, a number of variables are set from the header
28145 information for the relevant MIME part. These are described below. The contents
28146 of the MIME part are not by default decoded into a disk file except for MIME
28147 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
28148 part into a disk file, you can use the &%decode%& condition. The general
28149 syntax is:
28150 .display
28151 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
28152 .endd
28153 The right hand side is expanded before use. After expansion,
28154 the value can be:
28155
28156 .olist
28157 &"0"& or &"false"&, in which case no decoding is done.
28158 .next
28159 The string &"default"&. In that case, the file is put in the temporary
28160 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
28161 a sequential file name consisting of the message id and a sequence number. The
28162 full path and name is available in &$mime_decoded_filename$& after decoding.
28163 .next
28164 A full path name starting with a slash. If the full name is an existing
28165 directory, it is used as a replacement for the default directory. The filename
28166 is then sequentially assigned. If the path does not exist, it is used as
28167 the full path and file name.
28168 .next
28169 If the string does not start with a slash, it is used as the
28170 filename, and the default path is then used.
28171 .endlist
28172 The &%decode%& condition normally succeeds. It is only false for syntax
28173 errors or unusual circumstances such as memory shortages. You can easily decode
28174 a file with its original, proposed filename using
28175 .code
28176 decode = $mime_filename
28177 .endd
28178 However, you should keep in mind that &$mime_filename$& might contain
28179 anything. If you place files outside of the default path, they are not
28180 automatically unlinked.
28181
28182 For RFC822 attachments (these are messages attached to messages, with a
28183 content-type of &"message/rfc822"&), the ACL is called again in the same manner
28184 as for the primary message, only that the &$mime_is_rfc822$& expansion
28185 variable is set (see below). Attached messages are always decoded to disk
28186 before being checked, and the files are unlinked once the check is done.
28187
28188 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
28189 used to match regular expressions against raw and decoded MIME parts,
28190 respectively. They are described in section &<<SECTscanregex>>&.
28191
28192 .cindex "MIME content scanning" "returned variables"
28193 The following list describes all expansion variables that are
28194 available in the MIME ACL:
28195
28196 .vlist
28197 .vitem &$mime_boundary$&
28198 If the current part is a multipart (see &$mime_is_multipart$&) below, it should
28199 have a boundary string, which is stored in this variable. If the current part
28200 has no boundary parameter in the &'Content-Type:'& header, this variable
28201 contains the empty string.
28202
28203 .vitem &$mime_charset$&
28204 This variable contains the character set identifier, if one was found in the
28205 &'Content-Type:'& header. Examples for charset identifiers are:
28206 .code
28207 us-ascii
28208 gb2312 (Chinese)
28209 iso-8859-1
28210 .endd
28211 Please note that this value is not normalized, so you should do matches
28212 case-insensitively.
28213
28214 .vitem &$mime_content_description$&
28215 This variable contains the normalized content of the &'Content-Description:'&
28216 header. It can contain a human-readable description of the parts content. Some
28217 implementations repeat the filename for attachments here, but they are usually
28218 only used for display purposes.
28219
28220 .vitem &$mime_content_disposition$&
28221 This variable contains the normalized content of the &'Content-Disposition:'&
28222 header. You can expect strings like &"attachment"& or &"inline"& here.
28223
28224 .vitem &$mime_content_id$&
28225 This variable contains the normalized content of the &'Content-ID:'& header.
28226 This is a unique ID that can be used to reference a part from another part.
28227
28228 .vitem &$mime_content_size$&
28229 This variable is set only after the &%decode%& modifier (see above) has been
28230 successfully run. It contains the size of the decoded part in kilobytes. The
28231 size is always rounded up to full kilobytes, so only a completely empty part
28232 has a &$mime_content_size$& of zero.
28233
28234 .vitem &$mime_content_transfer_encoding$&
28235 This variable contains the normalized content of the
28236 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
28237 type. Typical values are &"base64"& and &"quoted-printable"&.
28238
28239 .vitem &$mime_content_type$&
28240 If the MIME part has a &'Content-Type:'& header, this variable contains its
28241 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
28242 are some examples of popular MIME types, as they may appear in this variable:
28243 .code
28244 text/plain
28245 text/html
28246 application/octet-stream
28247 image/jpeg
28248 audio/midi
28249 .endd
28250 If the MIME part has no &'Content-Type:'& header, this variable contains the
28251 empty string.
28252
28253 .vitem &$mime_decoded_filename$&
28254 This variable is set only after the &%decode%& modifier (see above) has been
28255 successfully run. It contains the full path and file name of the file
28256 containing the decoded data.
28257 .endlist
28258
28259 .cindex "RFC 2047"
28260 .vlist
28261 .vitem &$mime_filename$&
28262 This is perhaps the most important of the MIME variables. It contains a
28263 proposed filename for an attachment, if one was found in either the
28264 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
28265 RFC2047 decoded, but no additional sanity checks are done. If no filename was
28266 found, this variable contains the empty string.
28267
28268 .vitem &$mime_is_coverletter$&
28269 This variable attempts to differentiate the &"cover letter"& of an e-mail from
28270 attached data. It can be used to clamp down on flashy or unnecessarily encoded
28271 content in the cover letter, while not restricting attachments at all.
28272
28273 The variable contains 1 (true) for a MIME part believed to be part of the
28274 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
28275 follows:
28276
28277 .olist
28278 The outermost MIME part of a message is always a cover letter.
28279
28280 .next
28281 If a multipart/alternative or multipart/related MIME part is a cover letter,
28282 so are all MIME subparts within that multipart.
28283
28284 .next
28285 If any other multipart is a cover letter, the first subpart is a cover letter,
28286 and the rest are attachments.
28287
28288 .next
28289 All parts contained within an attachment multipart are attachments.
28290 .endlist olist
28291
28292 As an example, the following will ban &"HTML mail"& (including that sent with
28293 alternative plain text), while allowing HTML files to be attached. HTML
28294 coverletter mail attached to non-HMTL coverletter mail will also be allowed:
28295 .code
28296 deny message = HTML mail is not accepted here
28297 !condition = $mime_is_rfc822
28298 condition = $mime_is_coverletter
28299 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
28300 .endd
28301 .vitem &$mime_is_multipart$&
28302 This variable has the value 1 (true) when the current part has the main type
28303 &"multipart"&, for example &"multipart/alternative"& or &"multipart/mixed"&.
28304 Since multipart entities only serve as containers for other parts, you may not
28305 want to carry out specific actions on them.
28306
28307 .vitem &$mime_is_rfc822$&
28308 This variable has the value 1 (true) if the current part is not a part of the
28309 checked message itself, but part of an attached message. Attached message
28310 decoding is fully recursive.
28311
28312 .vitem &$mime_part_count$&
28313 This variable is a counter that is raised for each processed MIME part. It
28314 starts at zero for the very first part (which is usually a multipart). The
28315 counter is per-message, so it is reset when processing RFC822 attachments (see
28316 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
28317 complete, so you can use it in the DATA ACL to determine the number of MIME
28318 parts of a message. For non-MIME messages, this variable contains the value -1.
28319 .endlist
28320
28321
28322
28323 .section "Scanning with regular expressions" "SECTscanregex"
28324 .cindex "content scanning" "with regular expressions"
28325 .cindex "regular expressions" "content scanning with"
28326 You can specify your own custom regular expression matches on the full body of
28327 the message, or on individual MIME parts.
28328
28329 The &%regex%& condition takes one or more regular expressions as arguments and
28330 matches them against the full message (when called in the DATA ACL) or a raw
28331 MIME part (when called in the MIME ACL). The &%regex%& condition matches
28332 linewise, with a maximum line length of 32K characters. That means you cannot
28333 have multiline matches with the &%regex%& condition.
28334
28335 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
28336 to 32K of decoded content (the whole content at once, not linewise). If the
28337 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
28338 is decoded automatically when &%mime_regex%& is executed (using default path
28339 and filename values). If the decoded data is larger than 32K, only the first
28340 32K characters are checked.
28341
28342 The regular expressions are passed as a colon-separated list. To include a
28343 literal colon, you must double it. Since the whole right-hand side string is
28344 expanded before being used, you must also escape dollar signs and backslashes
28345 with more backslashes, or use the &`\N`& facility to disable expansion.
28346 Here is a simple example that contains two regular expressions:
28347 .code
28348 deny message = contains blacklisted regex ($regex_match_string)
28349 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
28350 .endd
28351 The conditions returns true if any one of the regular expressions matches. The
28352 &$regex_match_string$& expansion variable is then set up and contains the
28353 matching regular expression.
28354
28355 &*Warning*&: With large messages, these conditions can be fairly
28356 CPU-intensive.
28357
28358
28359
28360
28361 .section "The demime condition" "SECTdemimecond"
28362 .cindex "content scanning" "MIME checking"
28363 .cindex "MIME content scanning"
28364 The &%demime%& ACL condition provides MIME unpacking, sanity checking and file
28365 extension blocking. It is usable only in the DATA and non-SMTP ACLs. The
28366 &%demime%& condition uses a simpler interface to MIME decoding than the MIME
28367 ACL functionality, but provides no additional facilities. Please note that this
28368 condition is deprecated and kept only for backward compatibility. You must set
28369 the WITH_OLD_DEMIME option in &_Local/Makefile_& at build time to be able to
28370 use the &%demime%& condition.
28371
28372 The &%demime%& condition unpacks MIME containers in the message. It detects
28373 errors in MIME containers and can match file extensions found in the message
28374 against a list. Using this facility produces files containing the unpacked MIME
28375 parts of the message in the temporary scan directory. If you do antivirus
28376 scanning, it is recommended that you use the &%demime%& condition before the
28377 antivirus (&%malware%&) condition.
28378
28379 On the right-hand side of the &%demime%& condition you can pass a
28380 colon-separated list of file extensions that it should match against. For
28381 example:
28382 .code
28383 deny message = Found blacklisted file attachment
28384 demime = vbs:com:bat:pif:prf:lnk
28385 .endd
28386 If one of the file extensions is found, the condition is true, otherwise it is
28387 false. If there is a temporary error while demimeing (for example, &"disk
28388 full"&), the condition defers, and the message is temporarily rejected (unless
28389 the condition is on a &%warn%& verb).
28390
28391 The right-hand side is expanded before being treated as a list, so you can have
28392 conditions and lookups there. If it expands to an empty string, &"false"&, or
28393 zero (&"0"&), no demimeing is done and the condition is false.
28394
28395 The &%demime%& condition set the following variables:
28396
28397 .vlist
28398 .vitem &$demime_errorlevel$&
28399 .vindex "&$demime_errorlevel$&"
28400 When an error is detected in a MIME container, this variable contains the
28401 severity of the error, as an integer number. The higher the value, the more
28402 severe the error (the current maximum value is 3). If this variable is unset or
28403 zero, no error occurred.
28404
28405 .vitem &$demime_reason$&
28406 .vindex "&$demime_reason$&"
28407 When &$demime_errorlevel$& is greater than zero, this variable contains a
28408 human-readable text string describing the MIME error that occurred.
28409 .endlist
28410
28411 .vlist
28412 .vitem &$found_extension$&
28413 .vindex "&$found_extension$&"
28414 When the &%demime%& condition is true, this variable contains the file
28415 extension it found.
28416 .endlist
28417
28418 Both &$demime_errorlevel$& and &$demime_reason$& are set by the first call of
28419 the &%demime%& condition, and are not changed on subsequent calls.
28420
28421 If you do not want to check for file extensions, but rather use the &%demime%&
28422 condition for unpacking or error checking purposes, pass &"*"& as the
28423 right-hand side value. Here is a more elaborate example of how to use this
28424 facility:
28425 .code
28426 # Reject messages with serious MIME container errors
28427 deny message = Found MIME error ($demime_reason).
28428 demime = *
28429 condition = ${if >{$demime_errorlevel}{2}{1}{0}}
28430
28431 # Reject known virus spreading file extensions.
28432 # Accepting these is pretty much braindead.
28433 deny message = contains $found_extension file (blacklisted).
28434 demime = com:vbs:bat:pif:scr
28435
28436 # Freeze .exe and .doc files. Postmaster can
28437 # examine them and eventually thaw them.
28438 deny log_message = Another $found_extension file.
28439 demime = exe:doc
28440 control = freeze
28441 .endd
28442 .ecindex IIDcosca
28443
28444
28445
28446
28447 . ////////////////////////////////////////////////////////////////////////////
28448 . ////////////////////////////////////////////////////////////////////////////
28449
28450 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
28451 "Local scan function"
28452 .scindex IIDlosca "&[local_scan()]& function" "description of"
28453 .cindex "customizing" "input scan using C function"
28454 .cindex "policy control" "by local scan function"
28455 In these days of email worms, viruses, and ever-increasing spam, some sites
28456 want to apply a lot of checking to messages before accepting them.
28457
28458 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
28459 passing messages to external virus and spam scanning software. You can also do
28460 a certain amount in Exim itself through string expansions and the &%condition%&
28461 condition in the ACL that runs after the SMTP DATA command or the ACL for
28462 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
28463
28464 To allow for further customization to a site's own requirements, there is the
28465 possibility of linking Exim with a private message scanning function, written
28466 in C. If you want to run code that is written in something other than C, you
28467 can of course use a little C stub to call it.
28468
28469 The local scan function is run once for every incoming message, at the point
28470 when Exim is just about to accept the message.
28471 It can therefore be used to control non-SMTP messages from local processes as
28472 well as messages arriving via SMTP.
28473
28474 Exim applies a timeout to calls of the local scan function, and there is an
28475 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
28476 Zero means &"no timeout"&.
28477 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
28478 before calling the local scan function, so that the most common types of crash
28479 are caught. If the timeout is exceeded or one of those signals is caught, the
28480 incoming message is rejected with a temporary error if it is an SMTP message.
28481 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
28482 code. The incident is logged on the main and reject logs.
28483
28484
28485
28486 .section "Building Exim to use a local scan function" "SECID207"
28487 .cindex "&[local_scan()]& function" "building Exim to use"
28488 To make use of the local scan function feature, you must tell Exim where your
28489 function is before building Exim, by setting LOCAL_SCAN_SOURCE in your
28490 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
28491 directory, so you might set
28492 .code
28493 LOCAL_SCAN_SOURCE=Local/local_scan.c
28494 .endd
28495 for example. The function must be called &[local_scan()]&. It is called by
28496 Exim after it has received a message, when the success return code is about to
28497 be sent. This is after all the ACLs have been run. The return code from your
28498 function controls whether the message is actually accepted or not. There is a
28499 commented template function (that just accepts the message) in the file
28500 _src/local_scan.c_.
28501
28502 If you want to make use of Exim's run time configuration file to set options
28503 for your &[local_scan()]& function, you must also set
28504 .code
28505 LOCAL_SCAN_HAS_OPTIONS=yes
28506 .endd
28507 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
28508
28509
28510
28511
28512 .section "API for local_scan()" "SECTapiforloc"
28513 .cindex "&[local_scan()]& function" "API description"
28514 You must include this line near the start of your code:
28515 .code
28516 #include "local_scan.h"
28517 .endd
28518 This header file defines a number of variables and other values, and the
28519 prototype for the function itself. Exim is coded to use unsigned char values
28520 almost exclusively, and one of the things this header defines is a shorthand
28521 for &`unsigned char`& called &`uschar`&.
28522 It also contains the following macro definitions, to simplify casting character
28523 strings and pointers to character strings:
28524 .code
28525 #define CS (char *)
28526 #define CCS (const char *)
28527 #define CSS (char **)
28528 #define US (unsigned char *)
28529 #define CUS (const unsigned char *)
28530 #define USS (unsigned char **)
28531 .endd
28532 The function prototype for &[local_scan()]& is:
28533 .code
28534 extern int local_scan(int fd, uschar **return_text);
28535 .endd
28536 The arguments are as follows:
28537
28538 .ilist
28539 &%fd%& is a file descriptor for the file that contains the body of the message
28540 (the -D file). The file is open for reading and writing, but updating it is not
28541 recommended. &*Warning*&: You must &'not'& close this file descriptor.
28542
28543 The descriptor is positioned at character 19 of the file, which is the first
28544 character of the body itself, because the first 19 characters are the message
28545 id followed by &`-D`& and a newline. If you rewind the file, you should use the
28546 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
28547 case this changes in some future version.
28548 .next
28549 &%return_text%& is an address which you can use to return a pointer to a text
28550 string at the end of the function. The value it points to on entry is NULL.
28551 .endlist
28552
28553 The function must return an &%int%& value which is one of the following macros:
28554
28555 .vlist
28556 .vitem &`LOCAL_SCAN_ACCEPT`&
28557 .vindex "&$local_scan_data$&"
28558 The message is accepted. If you pass back a string of text, it is saved with
28559 the message, and made available in the variable &$local_scan_data$&. No
28560 newlines are permitted (if there are any, they are turned into spaces) and the
28561 maximum length of text is 1000 characters.
28562
28563 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
28564 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
28565 queued without immediate delivery, and is frozen.
28566
28567 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
28568 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
28569 queued without immediate delivery.
28570
28571 .vitem &`LOCAL_SCAN_REJECT`&
28572 The message is rejected; the returned text is used as an error message which is
28573 passed back to the sender and which is also logged. Newlines are permitted &--
28574 they cause a multiline response for SMTP rejections, but are converted to
28575 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
28576 used.
28577
28578 .vitem &`LOCAL_SCAN_TEMPREJECT`&
28579 The message is temporarily rejected; the returned text is used as an error
28580 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
28581 problem"& is used.
28582
28583 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
28584 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
28585 message is not written to the reject log. It has the effect of unsetting the
28586 &%rejected_header%& log selector for just this rejection. If
28587 &%rejected_header%& is already unset (see the discussion of the
28588 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
28589 same as LOCAL_SCAN_REJECT.
28590
28591 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
28592 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
28593 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
28594 .endlist
28595
28596 If the message is not being received by interactive SMTP, rejections are
28597 reported by writing to &%stderr%& or by sending an email, as configured by the
28598 &%-oe%& command line options.
28599
28600
28601
28602 .section "Configuration options for local_scan()" "SECTconoptloc"
28603 .cindex "&[local_scan()]& function" "configuration options"
28604 It is possible to have option settings in the main configuration file
28605 that set values in static variables in the &[local_scan()]& module. If you
28606 want to do this, you must have the line
28607 .code
28608 LOCAL_SCAN_HAS_OPTIONS=yes
28609 .endd
28610 in your &_Local/Makefile_& when you build Exim. (This line is in
28611 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
28612 file, you must define static variables to hold the option values, and a table
28613 to define them.
28614
28615 The table must be a vector called &%local_scan_options%&, of type
28616 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
28617 and a pointer to the variable that holds the value. The entries must appear in
28618 alphabetical order. Following &%local_scan_options%& you must also define a
28619 variable called &%local_scan_options_count%& that contains the number of
28620 entries in the table. Here is a short example, showing two kinds of option:
28621 .code
28622 static int my_integer_option = 42;
28623 static uschar *my_string_option = US"a default string";
28624
28625 optionlist local_scan_options[] = {
28626 { "my_integer", opt_int, &my_integer_option },
28627 { "my_string", opt_stringptr, &my_string_option }
28628 };
28629
28630 int local_scan_options_count =
28631 sizeof(local_scan_options)/sizeof(optionlist);
28632 .endd
28633 The values of the variables can now be changed from Exim's runtime
28634 configuration file by including a local scan section as in this example:
28635 .code
28636 begin local_scan
28637 my_integer = 99
28638 my_string = some string of text...
28639 .endd
28640 The available types of option data are as follows:
28641
28642 .vlist
28643 .vitem &*opt_bool*&
28644 This specifies a boolean (true/false) option. The address should point to a
28645 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
28646 that are defined as &"1"& and &"0"&, respectively. If you want to detect
28647 whether such a variable has been set at all, you can initialize it to
28648 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
28649 values.)
28650
28651 .vitem &*opt_fixed*&
28652 This specifies a fixed point number, such as is used for load averages.
28653 The address should point to a variable of type &`int`&. The value is stored
28654 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
28655
28656 .vitem &*opt_int*&
28657 This specifies an integer; the address should point to a variable of type
28658 &`int`&. The value may be specified in any of the integer formats accepted by
28659 Exim.
28660
28661 .vitem &*opt_mkint*&
28662 This is the same as &%opt_int%&, except that when such a value is output in a
28663 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
28664 printed with the suffix K or M.
28665
28666 .vitem &*opt_octint*&
28667 This also specifies an integer, but the value is always interpreted as an
28668 octal integer, whether or not it starts with the digit zero, and it is
28669 always output in octal.
28670
28671 .vitem &*opt_stringptr*&
28672 This specifies a string value; the address must be a pointer to a
28673 variable that points to a string (for example, of type &`uschar *`&).
28674
28675 .vitem &*opt_time*&
28676 This specifies a time interval value. The address must point to a variable of
28677 type &`int`&. The value that is placed there is a number of seconds.
28678 .endlist
28679
28680 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
28681 out the values of all the &[local_scan()]& options.
28682
28683
28684
28685 .section "Available Exim variables" "SECID208"
28686 .cindex "&[local_scan()]& function" "available Exim variables"
28687 The header &_local_scan.h_& gives you access to a number of C variables. These
28688 are the only ones that are guaranteed to be maintained from release to release.
28689 Note, however, that you can obtain the value of any Exim expansion variable,
28690 including &$recipients$&, by calling &'expand_string()'&. The exported
28691 C variables are as follows:
28692
28693 .vlist
28694 .vitem &*int&~body_linecount*&
28695 This variable contains the number of lines in the message's body.
28696
28697 .vitem &*int&~body_zerocount*&
28698 This variable contains the number of binary zero bytes in the message's body.
28699
28700 .vitem &*unsigned&~int&~debug_selector*&
28701 This variable is set to zero when no debugging is taking place. Otherwise, it
28702 is a bitmap of debugging selectors. Two bits are identified for use in
28703 &[local_scan()]&; they are defined as macros:
28704
28705 .ilist
28706 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
28707 testing option that is not privileged &-- any caller may set it. All the
28708 other selector bits can be set only by admin users.
28709
28710 .next
28711 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
28712 by the &`+local_scan`& debug selector. It is not included in the default set
28713 of debugging bits.
28714 .endlist ilist
28715
28716 Thus, to write to the debugging output only when &`+local_scan`& has been
28717 selected, you should use code like this:
28718 .code
28719 if ((debug_selector & D_local_scan) != 0)
28720 debug_printf("xxx", ...);
28721 .endd
28722 .vitem &*uschar&~*expand_string_message*&
28723 After a failing call to &'expand_string()'& (returned value NULL), the
28724 variable &%expand_string_message%& contains the error message, zero-terminated.
28725
28726 .vitem &*header_line&~*header_list*&
28727 A pointer to a chain of header lines. The &%header_line%& structure is
28728 discussed below.
28729
28730 .vitem &*header_line&~*header_last*&
28731 A pointer to the last of the header lines.
28732
28733 .vitem &*uschar&~*headers_charset*&
28734 The value of the &%headers_charset%& configuration option.
28735
28736 .vitem &*BOOL&~host_checking*&
28737 This variable is TRUE during a host checking session that is initiated by the
28738 &%-bh%& command line option.
28739
28740 .vitem &*uschar&~*interface_address*&
28741 The IP address of the interface that received the message, as a string. This
28742 is NULL for locally submitted messages.
28743
28744 .vitem &*int&~interface_port*&
28745 The port on which this message was received. When testing with the &%-bh%&
28746 command line option, the value of this variable is -1 unless a port has been
28747 specified via the &%-oMi%& option.
28748
28749 .vitem &*uschar&~*message_id*&
28750 This variable contains Exim's message id for the incoming message (the value of
28751 &$message_exim_id$&) as a zero-terminated string.
28752
28753 .vitem &*uschar&~*received_protocol*&
28754 The name of the protocol by which the message was received.
28755
28756 .vitem &*int&~recipients_count*&
28757 The number of accepted recipients.
28758
28759 .vitem &*recipient_item&~*recipients_list*&
28760 .cindex "recipient" "adding in local scan"
28761 .cindex "recipient" "removing in local scan"
28762 The list of accepted recipients, held in a vector of length
28763 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
28764 can add additional recipients by calling &'receive_add_recipient()'& (see
28765 below). You can delete recipients by removing them from the vector and
28766 adjusting the value in &%recipients_count%&. In particular, by setting
28767 &%recipients_count%& to zero you remove all recipients. If you then return the
28768 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
28769 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
28770 and then call &'receive_add_recipient()'& as often as needed.
28771
28772 .vitem &*uschar&~*sender_address*&
28773 The envelope sender address. For bounce messages this is the empty string.
28774
28775 .vitem &*uschar&~*sender_host_address*&
28776 The IP address of the sending host, as a string. This is NULL for
28777 locally-submitted messages.
28778
28779 .vitem &*uschar&~*sender_host_authenticated*&
28780 The name of the authentication mechanism that was used, or NULL if the message
28781 was not received over an authenticated SMTP connection.
28782
28783 .vitem &*uschar&~*sender_host_name*&
28784 The name of the sending host, if known.
28785
28786 .vitem &*int&~sender_host_port*&
28787 The port on the sending host.
28788
28789 .vitem &*BOOL&~smtp_input*&
28790 This variable is TRUE for all SMTP input, including BSMTP.
28791
28792 .vitem &*BOOL&~smtp_batched_input*&
28793 This variable is TRUE for BSMTP input.
28794
28795 .vitem &*int&~store_pool*&
28796 The contents of this variable control which pool of memory is used for new
28797 requests. See section &<<SECTmemhanloc>>& for details.
28798 .endlist
28799
28800
28801 .section "Structure of header lines" "SECID209"
28802 The &%header_line%& structure contains the members listed below.
28803 You can add additional header lines by calling the &'header_add()'& function
28804 (see below). You can cause header lines to be ignored (deleted) by setting
28805 their type to *.
28806
28807
28808 .vlist
28809 .vitem &*struct&~header_line&~*next*&
28810 A pointer to the next header line, or NULL for the last line.
28811
28812 .vitem &*int&~type*&
28813 A code identifying certain headers that Exim recognizes. The codes are printing
28814 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
28815 Notice in particular that any header line whose type is * is not transmitted
28816 with the message. This flagging is used for header lines that have been
28817 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
28818 lines.) Effectively, * means &"deleted"&.
28819
28820 .vitem &*int&~slen*&
28821 The number of characters in the header line, including the terminating and any
28822 internal newlines.
28823
28824 .vitem &*uschar&~*text*&
28825 A pointer to the text of the header. It always ends with a newline, followed by
28826 a zero byte. Internal newlines are preserved.
28827 .endlist
28828
28829
28830
28831 .section "Structure of recipient items" "SECID210"
28832 The &%recipient_item%& structure contains these members:
28833
28834 .vlist
28835 .vitem &*uschar&~*address*&
28836 This is a pointer to the recipient address as it was received.
28837
28838 .vitem &*int&~pno*&
28839 This is used in later Exim processing when top level addresses are created by
28840 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
28841 and must always contain -1 at this stage.
28842
28843 .vitem &*uschar&~*errors_to*&
28844 If this value is not NULL, bounce messages caused by failing to deliver to the
28845 recipient are sent to the address it contains. In other words, it overrides the
28846 envelope sender for this one recipient. (Compare the &%errors_to%& generic
28847 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
28848 an unqualified address, Exim qualifies it using the domain from
28849 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
28850 is NULL for all recipients.
28851 .endlist
28852
28853
28854
28855 .section "Available Exim functions" "SECID211"
28856 .cindex "&[local_scan()]& function" "available Exim functions"
28857 The header &_local_scan.h_& gives you access to a number of Exim functions.
28858 These are the only ones that are guaranteed to be maintained from release to
28859 release:
28860
28861 .vlist
28862 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
28863 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
28864
28865 This function creates a child process that runs the command specified by
28866 &%argv%&. The environment for the process is specified by &%envp%&, which can
28867 be NULL if no environment variables are to be passed. A new umask is supplied
28868 for the process in &%newumask%&.
28869
28870 Pipes to the standard input and output of the new process are set up
28871 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
28872 standard error is cloned to the standard output. If there are any file
28873 descriptors &"in the way"& in the new process, they are closed. If the final
28874 argument is TRUE, the new process is made into a process group leader.
28875
28876 The function returns the pid of the new process, or -1 if things go wrong.
28877
28878 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
28879 This function waits for a child process to terminate, or for a timeout (in
28880 seconds) to expire. A timeout value of zero means wait as long as it takes. The
28881 return value is as follows:
28882
28883 .ilist
28884 >= 0
28885
28886 The process terminated by a normal exit and the value is the process
28887 ending status.
28888
28889 .next
28890 < 0 and > &--256
28891
28892 The process was terminated by a signal and the value is the negation of the
28893 signal number.
28894
28895 .next
28896 &--256
28897
28898 The process timed out.
28899 .next
28900 &--257
28901
28902 The was some other error in wait(); &%errno%& is still set.
28903 .endlist
28904
28905 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
28906 This function provide you with a means of submitting a new message to
28907 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
28908 want, but this packages it all up for you.) The function creates a pipe,
28909 forks a subprocess that is running
28910 .code
28911 exim -t -oem -oi -f <>
28912 .endd
28913 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
28914 that is connected to the standard input. The yield of the function is the PID
28915 of the subprocess. You can then write a message to the file descriptor, with
28916 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
28917
28918 When you have finished, call &'child_close()'& to wait for the process to
28919 finish and to collect its ending status. A timeout value of zero is usually
28920 fine in this circumstance. Unless you have made a mistake with the recipient
28921 addresses, you should get a return code of zero.
28922
28923
28924 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
28925 *sender_authentication)*&
28926 This function is a more sophisticated version of &'child_open()'&. The command
28927 that it runs is:
28928 .display
28929 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
28930 .endd
28931 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
28932
28933
28934 .vitem &*void&~debug_printf(char&~*,&~...)*&
28935 This is Exim's debugging function, with arguments as for &'(printf()'&. The
28936 output is written to the standard error stream. If no debugging is selected,
28937 calls to &'debug_printf()'& have no effect. Normally, you should make calls
28938 conditional on the &`local_scan`& debug selector by coding like this:
28939 .code
28940 if ((debug_selector & D_local_scan) != 0)
28941 debug_printf("xxx", ...);
28942 .endd
28943
28944 .vitem &*uschar&~*expand_string(uschar&~*string)*&
28945 This is an interface to Exim's string expansion code. The return value is the
28946 expanded string, or NULL if there was an expansion failure.
28947 The C variable &%expand_string_message%& contains an error message after an
28948 expansion failure. If expansion does not change the string, the return value is
28949 the pointer to the input string. Otherwise, the return value points to a new
28950 block of memory that was obtained by a call to &'store_get()'&. See section
28951 &<<SECTmemhanloc>>& below for a discussion of memory handling.
28952
28953 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
28954 This function allows you to an add additional header line at the end of the
28955 existing ones. The first argument is the type, and should normally be a space
28956 character. The second argument is a format string and any number of
28957 substitution arguments as for &[sprintf()]&. You may include internal newlines
28958 if you want, and you must ensure that the string ends with a newline.
28959
28960 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
28961 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
28962 This function adds a new header line at a specified point in the header
28963 chain. The header itself is specified as for &'header_add()'&.
28964
28965 If &%name%& is NULL, the new header is added at the end of the chain if
28966 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
28967 NULL, the header lines are searched for the first non-deleted header that
28968 matches the name. If one is found, the new header is added before it if
28969 &%after%& is false. If &%after%& is true, the new header is added after the
28970 found header and any adjacent subsequent ones with the same name (even if
28971 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
28972 option controls where the header is added. If it is true, addition is at the
28973 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
28974 headers, or at the top if there are no &'Received:'& headers, you could use
28975 .code
28976 header_add_at_position(TRUE, US"Received", TRUE,
28977 ' ', "X-xxx: ...");
28978 .endd
28979 Normally, there is always at least one non-deleted &'Received:'& header, but
28980 there may not be if &%received_header_text%& expands to an empty string.
28981
28982
28983 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
28984 This function removes header lines. If &%occurrence%& is zero or negative, all
28985 occurrences of the header are removed. If occurrence is greater than zero, that
28986 particular instance of the header is removed. If no header(s) can be found that
28987 match the specification, the function does nothing.
28988
28989
28990 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
28991 int&~length,&~BOOL&~notdel)*&"
28992 This function tests whether the given header has the given name. It is not just
28993 a string comparison, because white space is permitted between the name and the
28994 colon. If the &%notdel%& argument is true, a false return is forced for all
28995 &"deleted"& headers; otherwise they are not treated specially. For example:
28996 .code
28997 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
28998 .endd
28999 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
29000 .cindex "base64 encoding" "functions for &[local_scan()]& use"
29001 This function base64-encodes a string, which is passed by address and length.
29002 The text may contain bytes of any value, including zero. The result is passed
29003 back in dynamic memory that is obtained by calling &'store_get()'&. It is
29004 zero-terminated.
29005
29006 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
29007 This function decodes a base64-encoded string. Its arguments are a
29008 zero-terminated base64-encoded string and the address of a variable that is set
29009 to point to the result, which is in dynamic memory. The length of the decoded
29010 string is the yield of the function. If the input is invalid base64 data, the
29011 yield is -1. A zero byte is added to the end of the output string to make it
29012 easy to interpret as a C string (assuming it contains no zeros of its own). The
29013 added zero byte is not included in the returned count.
29014
29015 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
29016 This function checks for a match in a domain list. Domains are always
29017 matched caselessly. The return value is one of the following:
29018 .display
29019 &`OK `& match succeeded
29020 &`FAIL `& match failed
29021 &`DEFER `& match deferred
29022 .endd
29023 DEFER is usually caused by some kind of lookup defer, such as the
29024 inability to contact a database.
29025
29026 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
29027 BOOL&~caseless)*&"
29028 This function checks for a match in a local part list. The third argument
29029 controls case-sensitivity. The return values are as for
29030 &'lss_match_domain()'&.
29031
29032 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
29033 BOOL&~caseless)*&"
29034 This function checks for a match in an address list. The third argument
29035 controls the case-sensitivity of the local part match. The domain is always
29036 matched caselessly. The return values are as for &'lss_match_domain()'&.
29037
29038 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
29039 uschar&~*list)*&"
29040 This function checks for a match in a host list. The most common usage is
29041 expected to be
29042 .code
29043 lss_match_host(sender_host_name, sender_host_address, ...)
29044 .endd
29045 .vindex "&$sender_host_address$&"
29046 An empty address field matches an empty item in the host list. If the host name
29047 is NULL, the name corresponding to &$sender_host_address$& is automatically
29048 looked up if a host name is required to match an item in the list. The return
29049 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
29050 returns ERROR in the case when it had to look up a host name, but the lookup
29051 failed.
29052
29053 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
29054 *format,&~...)*&"
29055 This function writes to Exim's log files. The first argument should be zero (it
29056 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
29057 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
29058 them. It specifies to which log or logs the message is written. The remaining
29059 arguments are a format and relevant insertion arguments. The string should not
29060 contain any newlines, not even at the end.
29061
29062
29063 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
29064 This function adds an additional recipient to the message. The first argument
29065 is the recipient address. If it is unqualified (has no domain), it is qualified
29066 with the &%qualify_recipient%& domain. The second argument must always be -1.
29067
29068 This function does not allow you to specify a private &%errors_to%& address (as
29069 described with the structure of &%recipient_item%& above), because it pre-dates
29070 the addition of that field to the structure. However, it is easy to add such a
29071 value afterwards. For example:
29072 .code
29073 receive_add_recipient(US"monitor@mydom.example", -1);
29074 recipients_list[recipients_count-1].errors_to =
29075 US"postmaster@mydom.example";
29076 .endd
29077
29078 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
29079 This is a convenience function to remove a named recipient from the list of
29080 recipients. It returns true if a recipient was removed, and false if no
29081 matching recipient could be found. The argument must be a complete email
29082 address.
29083 .endlist
29084
29085
29086 .cindex "RFC 2047"
29087 .vlist
29088 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
29089 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
29090 This function decodes strings that are encoded according to RFC 2047. Typically
29091 these are the contents of header lines. First, each &"encoded word"& is decoded
29092 from the Q or B encoding into a byte-string. Then, if provided with the name of
29093 a charset encoding, and if the &[iconv()]& function is available, an attempt is
29094 made to translate the result to the named character set. If this fails, the
29095 binary string is returned with an error message.
29096
29097 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
29098 maximum MIME word length is enforced. The third argument is the target
29099 encoding, or NULL if no translation is wanted.
29100
29101 .cindex "binary zero" "in RFC 2047 decoding"
29102 .cindex "RFC 2047" "binary zero in"
29103 If a binary zero is encountered in the decoded string, it is replaced by the
29104 contents of the &%zeroval%& argument. For use with Exim headers, the value must
29105 not be 0 because header lines are handled as zero-terminated strings.
29106
29107 The function returns the result of processing the string, zero-terminated; if
29108 &%lenptr%& is not NULL, the length of the result is set in the variable to
29109 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
29110
29111 If an error is encountered, the function returns NULL and uses the &%error%&
29112 argument to return an error message. The variable pointed to by &%error%& is
29113 set to NULL if there is no error; it may be set non-NULL even when the function
29114 returns a non-NULL value if decoding was successful, but there was a problem
29115 with translation.
29116
29117
29118 .vitem &*int&~smtp_fflush(void)*&
29119 This function is used in conjunction with &'smtp_printf()'&, as described
29120 below.
29121
29122 .vitem &*void&~smtp_printf(char&~*,&~...)*&
29123 The arguments of this function are like &[printf()]&; it writes to the SMTP
29124 output stream. You should use this function only when there is an SMTP output
29125 stream, that is, when the incoming message is being received via interactive
29126 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
29127 is FALSE. If you want to test for an incoming message from another host (as
29128 opposed to a local process that used the &%-bs%& command line option), you can
29129 test the value of &%sender_host_address%&, which is non-NULL when a remote host
29130 is involved.
29131
29132 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
29133 output function, so it can be used for all forms of SMTP connection.
29134
29135 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
29136 must start with an appropriate response code: 550 if you are going to return
29137 LOCAL_SCAN_REJECT, 451 if you are going to return
29138 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
29139 initial lines of a multi-line response, the code must be followed by a hyphen
29140 to indicate that the line is not the final response line. You must also ensure
29141 that the lines you write terminate with CRLF. For example:
29142 .code
29143 smtp_printf("550-this is some extra info\r\n");
29144 return LOCAL_SCAN_REJECT;
29145 .endd
29146 Note that you can also create multi-line responses by including newlines in
29147 the data returned via the &%return_text%& argument. The added value of using
29148 &'smtp_printf()'& is that, for instance, you could introduce delays between
29149 multiple output lines.
29150
29151 The &'smtp_printf()'& function does not return any error indication, because it
29152 does not automatically flush pending output, and therefore does not test
29153 the state of the stream. (In the main code of Exim, flushing and error
29154 detection is done when Exim is ready for the next SMTP input command.) If
29155 you want to flush the output and check for an error (for example, the
29156 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
29157 arguments. It flushes the output stream, and returns a non-zero value if there
29158 is an error.
29159
29160 .vitem &*void&~*store_get(int)*&
29161 This function accesses Exim's internal store (memory) manager. It gets a new
29162 chunk of memory whose size is given by the argument. Exim bombs out if it ever
29163 runs out of memory. See the next section for a discussion of memory handling.
29164
29165 .vitem &*void&~*store_get_perm(int)*&
29166 This function is like &'store_get()'&, but it always gets memory from the
29167 permanent pool. See the next section for a discussion of memory handling.
29168
29169 .vitem &*uschar&~*string_copy(uschar&~*string)*&
29170 See below.
29171
29172 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
29173 See below.
29174
29175 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
29176 These three functions create strings using Exim's dynamic memory facilities.
29177 The first makes a copy of an entire string. The second copies up to a maximum
29178 number of characters, indicated by the second argument. The third uses a format
29179 and insertion arguments to create a new string. In each case, the result is a
29180 pointer to a new string in the current memory pool. See the next section for
29181 more discussion.
29182 .endlist
29183
29184
29185
29186 .section "More about Exim's memory handling" "SECTmemhanloc"
29187 .cindex "&[local_scan()]& function" "memory handling"
29188 No function is provided for freeing memory, because that is never needed.
29189 The dynamic memory that Exim uses when receiving a message is automatically
29190 recycled if another message is received by the same process (this applies only
29191 to incoming SMTP connections &-- other input methods can supply only one
29192 message at a time). After receiving the last message, a reception process
29193 terminates.
29194
29195 Because it is recycled, the normal dynamic memory cannot be used for holding
29196 data that must be preserved over a number of incoming messages on the same SMTP
29197 connection. However, Exim in fact uses two pools of dynamic memory; the second
29198 one is not recycled, and can be used for this purpose.
29199
29200 If you want to allocate memory that remains available for subsequent messages
29201 in the same SMTP connection, you should set
29202 .code
29203 store_pool = POOL_PERM
29204 .endd
29205 before calling the function that does the allocation. There is no need to
29206 restore the value if you do not need to; however, if you do want to revert to
29207 the normal pool, you can either restore the previous value of &%store_pool%& or
29208 set it explicitly to POOL_MAIN.
29209
29210 The pool setting applies to all functions that get dynamic memory, including
29211 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
29212 There is also a convenience function called &'store_get_perm()'& that gets a
29213 block of memory from the permanent pool while preserving the value of
29214 &%store_pool%&.
29215 .ecindex IIDlosca
29216
29217
29218
29219
29220 . ////////////////////////////////////////////////////////////////////////////
29221 . ////////////////////////////////////////////////////////////////////////////
29222
29223 .chapter "System-wide message filtering" "CHAPsystemfilter"
29224 .scindex IIDsysfil1 "filter" "system filter"
29225 .scindex IIDsysfil2 "filtering all mail"
29226 .scindex IIDsysfil3 "system filter"
29227 The previous chapters (on ACLs and the local scan function) describe checks
29228 that can be applied to messages before they are accepted by a host. There is
29229 also a mechanism for checking messages once they have been received, but before
29230 they are delivered. This is called the &'system filter'&.
29231
29232 The system filter operates in a similar manner to users' filter files, but it
29233 is run just once per message (however many recipients the message has).
29234 It should not normally be used as a substitute for routing, because &%deliver%&
29235 commands in a system router provide new envelope recipient addresses.
29236 The system filter must be an Exim filter. It cannot be a Sieve filter.
29237
29238 The system filter is run at the start of a delivery attempt, before any routing
29239 is done. If a message fails to be completely delivered at the first attempt,
29240 the system filter is run again at the start of every retry.
29241 If you want your filter to do something only once per message, you can make use
29242 of the &%first_delivery%& condition in an &%if%& command in the filter to
29243 prevent it happening on retries.
29244
29245 .vindex "&$domain$&"
29246 .vindex "&$local_part$&"
29247 &*Warning*&: Because the system filter runs just once, variables that are
29248 specific to individual recipient addresses, such as &$local_part$& and
29249 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
29250 you want to run a centrally-specified filter for each recipient address
29251 independently, you can do so by setting up a suitable &(redirect)& router, as
29252 described in section &<<SECTperaddfil>>& below.
29253
29254
29255 .section "Specifying a system filter" "SECID212"
29256 .cindex "uid (user id)" "system filter"
29257 .cindex "gid (group id)" "system filter"
29258 The name of the file that contains the system filter must be specified by
29259 setting &%system_filter%&. If you want the filter to run under a uid and gid
29260 other than root, you must also set &%system_filter_user%& and
29261 &%system_filter_group%& as appropriate. For example:
29262 .code
29263 system_filter = /etc/mail/exim.filter
29264 system_filter_user = exim
29265 .endd
29266 If a system filter generates any deliveries directly to files or pipes (via the
29267 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
29268 specified by setting &%system_filter_file_transport%& and
29269 &%system_filter_pipe_transport%&, respectively. Similarly,
29270 &%system_filter_reply_transport%& must be set to handle any messages generated
29271 by the &%reply%& command.
29272
29273
29274 .section "Testing a system filter" "SECID213"
29275 You can run simple tests of a system filter in the same way as for a user
29276 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
29277 are permitted only in system filters are recognized.
29278
29279 If you want to test the combined effect of a system filter and a user filter,
29280 you can use both &%-bF%& and &%-bf%& on the same command line.
29281
29282
29283
29284 .section "Contents of a system filter" "SECID214"
29285 The language used to specify system filters is the same as for users' filter
29286 files. It is described in the separate end-user document &'Exim's interface to
29287 mail filtering'&. However, there are some additional features that are
29288 available only in system filters; these are described in subsequent sections.
29289 If they are encountered in a user's filter file or when testing with &%-bf%&,
29290 they cause errors.
29291
29292 .cindex "frozen messages" "manual thaw; testing in filter"
29293 There are two special conditions which, though available in users' filter
29294 files, are designed for use in system filters. The condition &%first_delivery%&
29295 is true only for the first attempt at delivering a message, and
29296 &%manually_thawed%& is true only if the message has been frozen, and
29297 subsequently thawed by an admin user. An explicit forced delivery counts as a
29298 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
29299
29300 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
29301 specify an &"unseen"& (non-significant) delivery, and that delivery does not
29302 succeed, it will not be tried again.
29303 If you want Exim to retry an unseen delivery until it succeeds, you should
29304 arrange to set it up every time the filter runs.
29305
29306 When a system filter finishes running, the values of the variables &$n0$& &--
29307 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
29308 users' filter files. Thus a system filter can, for example, set up &"scores"&
29309 to which users' filter files can refer.
29310
29311
29312
29313 .section "Additional variable for system filters" "SECID215"
29314 .vindex "&$recipients$&"
29315 The expansion variable &$recipients$&, containing a list of all the recipients
29316 of the message (separated by commas and white space), is available in system
29317 filters. It is not available in users' filters for privacy reasons.
29318
29319
29320
29321 .section "Defer, freeze, and fail commands for system filters" "SECID216"
29322 .cindex "freezing messages"
29323 .cindex "message" "freezing"
29324 .cindex "message" "forced failure"
29325 .cindex "&%fail%&" "in system filter"
29326 .cindex "&%freeze%& in system filter"
29327 .cindex "&%defer%& in system filter"
29328 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
29329 always available in system filters, but are not normally enabled in users'
29330 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
29331 for the &(redirect)& router.) These commands can optionally be followed by the
29332 word &%text%& and a string containing an error message, for example:
29333 .code
29334 fail text "this message looks like spam to me"
29335 .endd
29336 The keyword &%text%& is optional if the next character is a double quote.
29337
29338 The &%defer%& command defers delivery of the original recipients of the
29339 message. The &%fail%& command causes all the original recipients to be failed,
29340 and a bounce message to be created. The &%freeze%& command suspends all
29341 delivery attempts for the original recipients. In all cases, any new deliveries
29342 that are specified by the filter are attempted as normal after the filter has
29343 run.
29344
29345 The &%freeze%& command is ignored if the message has been manually unfrozen and
29346 not manually frozen since. This means that automatic freezing by a system
29347 filter can be used as a way of checking out suspicious messages. If a message
29348 is found to be all right, manually unfreezing it allows it to be delivered.
29349
29350 .cindex "log" "&%fail%& command log line"
29351 .cindex "&%fail%&" "log line; reducing"
29352 The text given with a fail command is used as part of the bounce message as
29353 well as being written to the log. If the message is quite long, this can fill
29354 up a lot of log space when such failures are common. To reduce the size of the
29355 log message, Exim interprets the text in a special way if it starts with the
29356 two characters &`<<`& and contains &`>>`& later. The text between these two
29357 strings is written to the log, and the rest of the text is used in the bounce
29358 message. For example:
29359 .code
29360 fail "<<filter test 1>>Your message is rejected \
29361 because it contains attachments that we are \
29362 not prepared to receive."
29363 .endd
29364
29365 .cindex "loop" "caused by &%fail%&"
29366 Take great care with the &%fail%& command when basing the decision to fail on
29367 the contents of the message, because the bounce message will of course include
29368 the contents of the original message and will therefore trigger the &%fail%&
29369 command again (causing a mail loop) unless steps are taken to prevent this.
29370 Testing the &%error_message%& condition is one way to prevent this. You could
29371 use, for example
29372 .code
29373 if $message_body contains "this is spam" and not error_message
29374 then fail text "spam is not wanted here" endif
29375 .endd
29376 though of course that might let through unwanted bounce messages. The
29377 alternative is clever checking of the body and/or headers to detect bounces
29378 generated by the filter.
29379
29380 The interpretation of a system filter file ceases after a
29381 &%defer%&,
29382 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
29383 set up earlier in the filter file are honoured, so you can use a sequence such
29384 as
29385 .code
29386 mail ...
29387 freeze
29388 .endd
29389 to send a specified message when the system filter is freezing (or deferring or
29390 failing) a message. The normal deliveries for the message do not, of course,
29391 take place.
29392
29393
29394
29395 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
29396 .cindex "header lines" "adding; in system filter"
29397 .cindex "header lines" "removing; in system filter"
29398 .cindex "filter" "header lines; adding/removing"
29399 Two filter commands that are available only in system filters are:
29400 .code
29401 headers add <string>
29402 headers remove <string>
29403 .endd
29404 The argument for the &%headers add%& is a string that is expanded and then
29405 added to the end of the message's headers. It is the responsibility of the
29406 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
29407 space is ignored, and if the string is otherwise empty, or if the expansion is
29408 forced to fail, the command has no effect.
29409
29410 You can use &"\n"& within the string, followed by white space, to specify
29411 continued header lines. More than one header may be added in one command by
29412 including &"\n"& within the string without any following white space. For
29413 example:
29414 .code
29415 headers add "X-header-1: ....\n \
29416 continuation of X-header-1 ...\n\
29417 X-header-2: ...."
29418 .endd
29419 Note that the header line continuation white space after the first newline must
29420 be placed before the backslash that continues the input string, because white
29421 space after input continuations is ignored.
29422
29423 The argument for &%headers remove%& is a colon-separated list of header names.
29424 This command applies only to those headers that are stored with the message;
29425 those that are added at delivery time (such as &'Envelope-To:'& and
29426 &'Return-Path:'&) cannot be removed by this means. If there is more than one
29427 header with the same name, they are all removed.
29428
29429 The &%headers%& command in a system filter makes an immediate change to the set
29430 of header lines that was received with the message (with possible additions
29431 from ACL processing). Subsequent commands in the system filter operate on the
29432 modified set, which also forms the basis for subsequent message delivery.
29433 Unless further modified during routing or transporting, this set of headers is
29434 used for all recipients of the message.
29435
29436 During routing and transporting, the variables that refer to the contents of
29437 header lines refer only to those lines that are in this set. Thus, header lines
29438 that are added by a system filter are visible to users' filter files and to all
29439 routers and transports. This contrasts with the manipulation of header lines by
29440 routers and transports, which is not immediate, but which instead is saved up
29441 until the message is actually being written (see section
29442 &<<SECTheadersaddrem>>&).
29443
29444 If the message is not delivered at the first attempt, header lines that were
29445 added by the system filter are stored with the message, and so are still
29446 present at the next delivery attempt. Header lines that were removed are still
29447 present, but marked &"deleted"& so that they are not transported with the
29448 message. For this reason, it is usual to make the &%headers%& command
29449 conditional on &%first_delivery%& so that the set of header lines is not
29450 modified more than once.
29451
29452 Because header modification in a system filter acts immediately, you have to
29453 use an indirect approach if you want to modify the contents of a header line.
29454 For example:
29455 .code
29456 headers add "Old-Subject: $h_subject:"
29457 headers remove "Subject"
29458 headers add "Subject: new subject (was: $h_old-subject:)"
29459 headers remove "Old-Subject"
29460 .endd
29461
29462
29463
29464 .section "Setting an errors address in a system filter" "SECID217"
29465 .cindex "envelope sender"
29466 In a system filter, if a &%deliver%& command is followed by
29467 .code
29468 errors_to <some address>
29469 .endd
29470 in order to change the envelope sender (and hence the error reporting) for that
29471 delivery, any address may be specified. (In a user filter, only the current
29472 user's address can be set.) For example, if some mail is being monitored, you
29473 might use
29474 .code
29475 unseen deliver monitor@spying.example errors_to root@local.example
29476 .endd
29477 to take a copy which would not be sent back to the normal error reporting
29478 address if its delivery failed.
29479
29480
29481
29482 .section "Per-address filtering" "SECTperaddfil"
29483 .vindex "&$domain$&"
29484 .vindex "&$local_part$&"
29485 In contrast to the system filter, which is run just once per message for each
29486 delivery attempt, it is also possible to set up a system-wide filtering
29487 operation that runs once for each recipient address. In this case, variables
29488 such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
29489 filter file could be made dependent on them. This is an example of a router
29490 which implements such a filter:
29491 .code
29492 central_filter:
29493 check_local_user
29494 driver = redirect
29495 domains = +local_domains
29496 file = /central/filters/$local_part
29497 no_verify
29498 allow_filter
29499 allow_freeze
29500 .endd
29501 The filter is run in a separate process under its own uid. Therefore, either
29502 &%check_local_user%& must be set (as above), in which case the filter is run as
29503 the local user, or the &%user%& option must be used to specify which user to
29504 use. If both are set, &%user%& overrides.
29505
29506 Care should be taken to ensure that none of the commands in the filter file
29507 specify a significant delivery if the message is to go on to be delivered to
29508 its intended recipient. The router will not then claim to have dealt with the
29509 address, so it will be passed on to subsequent routers to be delivered in the
29510 normal way.
29511 .ecindex IIDsysfil1
29512 .ecindex IIDsysfil2
29513 .ecindex IIDsysfil3
29514
29515
29516
29517
29518
29519
29520 . ////////////////////////////////////////////////////////////////////////////
29521 . ////////////////////////////////////////////////////////////////////////////
29522
29523 .chapter "Message processing" "CHAPmsgproc"
29524 .scindex IIDmesproc "message" "general processing"
29525 Exim performs various transformations on the sender and recipient addresses of
29526 all messages that it handles, and also on the messages' header lines. Some of
29527 these are optional and configurable, while others always take place. All of
29528 this processing, except rewriting as a result of routing, and the addition or
29529 removal of header lines while delivering, happens when a message is received,
29530 before it is placed on Exim's queue.
29531
29532 Some of the automatic processing takes place by default only for
29533 &"locally-originated"& messages. This adjective is used to describe messages
29534 that are not received over TCP/IP, but instead are passed to an Exim process on
29535 its standard input. This includes the interactive &"local SMTP"& case that is
29536 set up by the &%-bs%& command line option.
29537
29538 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
29539 or ::1) are not considered to be locally-originated. Exim does not treat the
29540 loopback interface specially in any way.
29541
29542 If you want the loopback interface to be treated specially, you must ensure
29543 that there are appropriate entries in your ACLs.
29544
29545
29546
29547
29548 .section "Submission mode for non-local messages" "SECTsubmodnon"
29549 .cindex "message" "submission"
29550 .cindex "submission mode"
29551 Processing that happens automatically for locally-originated messages (unless
29552 &%suppress_local_fixups%& is set) can also be requested for messages that are
29553 received over TCP/IP. The term &"submission mode"& is used to describe this
29554 state. Submission mode is set by the modifier
29555 .code
29556 control = submission
29557 .endd
29558 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
29559 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
29560 a local submission, and is normally used when the source of the message is
29561 known to be an MUA running on a client host (as opposed to an MTA). For
29562 example, to set submission mode for messages originating on the IPv4 loopback
29563 interface, you could include the following in the MAIL ACL:
29564 .code
29565 warn hosts = 127.0.0.1
29566 control = submission
29567 .endd
29568 .cindex "&%sender_retain%& submission option"
29569 There are some options that can be used when setting submission mode. A slash
29570 is used to separate options. For example:
29571 .code
29572 control = submission/sender_retain
29573 .endd
29574 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
29575 true and &%local_from_check%& false for the current incoming message. The first
29576 of these allows an existing &'Sender:'& header in the message to remain, and
29577 the second suppresses the check to ensure that &'From:'& matches the
29578 authenticated sender. With this setting, Exim still fixes up messages by adding
29579 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
29580 attempt to check sender authenticity in header lines.
29581
29582 When &%sender_retain%& is not set, a submission mode setting may specify a
29583 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
29584 example:
29585 .code
29586 control = submission/domain=some.domain
29587 .endd
29588 The domain may be empty. How this value is used is described in sections
29589 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
29590 that allows you to specify the user's full name for inclusion in a created
29591 &'Sender:'& or &'From:'& header line. For example:
29592 .code
29593 accept authenticated = *
29594 control = submission/domain=wonderland.example/\
29595 name=${lookup {$authenticated_id} \
29596 lsearch {/etc/exim/namelist}}
29597 .endd
29598 Because the name may contain any characters, including slashes, the &%name%&
29599 option must be given last. The remainder of the string is used as the name. For
29600 the example above, if &_/etc/exim/namelist_& contains:
29601 .code
29602 bigegg: Humpty Dumpty
29603 .endd
29604 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
29605 line would be:
29606 .code
29607 Sender: Humpty Dumpty <bigegg@wonderland.example>
29608 .endd
29609 .cindex "return path" "in submission mode"
29610 By default, submission mode forces the return path to the same address as is
29611 used to create the &'Sender:'& header. However, if &%sender_retain%& is
29612 specified, the return path is also left unchanged.
29613
29614 &*Note*&: The changes caused by submission mode take effect after the predata
29615 ACL. This means that any sender checks performed before the fix-ups use the
29616 untrusted sender address specified by the user, not the trusted sender address
29617 specified by submission mode. Although this might be slightly unexpected, it
29618 does mean that you can configure ACL checks to spot that a user is trying to
29619 spoof another's address.
29620
29621 .section "Line endings" "SECTlineendings"
29622 .cindex "line endings"
29623 .cindex "carriage return"
29624 .cindex "linefeed"
29625 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
29626 linefeed) is the line ending for messages transmitted over the Internet using
29627 SMTP over TCP/IP. However, within individual operating systems, different
29628 conventions are used. For example, Unix-like systems use just LF, but others
29629 use CRLF or just CR.
29630
29631 Exim was designed for Unix-like systems, and internally, it stores messages
29632 using the system's convention of a single LF as a line terminator. When
29633 receiving a message, all line endings are translated to this standard format.
29634 Originally, it was thought that programs that passed messages directly to an
29635 MTA within an operating system would use that system's convention. Experience
29636 has shown that this is not the case; for example, there are Unix applications
29637 that use CRLF in this circumstance. For this reason, and for compatibility with
29638 other MTAs, the way Exim handles line endings for all messages is now as
29639 follows:
29640
29641 .ilist
29642 LF not preceded by CR is treated as a line ending.
29643 .next
29644 CR is treated as a line ending; if it is immediately followed by LF, the LF
29645 is ignored.
29646 .next
29647 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
29648 nor a local message in the state where a line containing only a dot is a
29649 terminator.
29650 .next
29651 If a bare CR is encountered within a header line, an extra space is added after
29652 the line terminator so as not to end the header line. The reasoning behind this
29653 is that bare CRs in header lines are most likely either to be mistakes, or
29654 people trying to play silly games.
29655 .next
29656 If the first header line received in a message ends with CRLF, a subsequent
29657 bare LF in a header line is treated in the same way as a bare CR in a header
29658 line.
29659 .endlist
29660
29661
29662
29663
29664
29665 .section "Unqualified addresses" "SECID218"
29666 .cindex "unqualified addresses"
29667 .cindex "address" "qualification"
29668 By default, Exim expects every envelope address it receives from an external
29669 host to be fully qualified. Unqualified addresses cause negative responses to
29670 SMTP commands. However, because SMTP is used as a means of transporting
29671 messages from MUAs running on personal workstations, there is sometimes a
29672 requirement to accept unqualified addresses from specific hosts or IP networks.
29673
29674 Exim has two options that separately control which hosts may send unqualified
29675 sender or recipient addresses in SMTP commands, namely
29676 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
29677 cases, if an unqualified address is accepted, it is qualified by adding the
29678 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
29679
29680 .oindex "&%qualify_domain%&"
29681 .oindex "&%qualify_recipient%&"
29682 Unqualified addresses in header lines are automatically qualified for messages
29683 that are locally originated, unless the &%-bnq%& option is given on the command
29684 line. For messages received over SMTP, unqualified addresses in header lines
29685 are qualified only if unqualified addresses are permitted in SMTP commands. In
29686 other words, such qualification is also controlled by
29687 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
29688
29689
29690
29691
29692 .section "The UUCP From line" "SECID219"
29693 .cindex "&""From""& line"
29694 .cindex "UUCP" "&""From""& line"
29695 .cindex "sender" "address"
29696 .oindex "&%uucp_from_pattern%&"
29697 .oindex "&%uucp_from_sender%&"
29698 .cindex "envelope sender"
29699 .cindex "Sendmail compatibility" "&""From""& line"
29700 Messages that have come from UUCP (and some other applications) often begin
29701 with a line containing the envelope sender and a timestamp, following the word
29702 &"From"&. Examples of two common formats are:
29703 .code
29704 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
29705 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
29706 .endd
29707 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
29708 Exim recognizes such lines at the start of messages that are submitted to it
29709 via the command line (that is, on the standard input). It does not recognize
29710 such lines in incoming SMTP messages, unless the sending host matches
29711 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
29712 and &%ignore_fromline_local%& is set. The recognition is controlled by a
29713 regular expression that is defined by the &%uucp_from_pattern%& option, whose
29714 default value matches the two common cases shown above and puts the address
29715 that follows &"From"& into &$1$&.
29716
29717 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
29718 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
29719 a trusted user, the message's sender address is constructed by expanding the
29720 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
29721 then parsed as an RFC 2822 address. If there is no domain, the local part is
29722 qualified with &%qualify_domain%& unless it is the empty string. However, if
29723 the command line &%-f%& option is used, it overrides the &"From"& line.
29724
29725 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
29726 sender address is not changed. This is also the case for incoming SMTP messages
29727 that are permitted to contain &"From"& lines.
29728
29729 Only one &"From"& line is recognized. If there is more than one, the second is
29730 treated as a data line that starts the body of the message, as it is not valid
29731 as a header line. This also happens if a &"From"& line is present in an
29732 incoming SMTP message from a source that is not permitted to send them.
29733
29734
29735
29736 .section "Resent- header lines" "SECID220"
29737 .cindex "&%Resent-%& header lines"
29738 RFC 2822 makes provision for sets of header lines starting with the string
29739 &`Resent-`& to be added to a message when it is resent by the original
29740 recipient to somebody else. These headers are &'Resent-Date:'&,
29741 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
29742 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
29743
29744 .blockquote
29745 &'Resent fields are strictly informational. They MUST NOT be used in the normal
29746 processing of replies or other such automatic actions on messages.'&
29747 .endblockquote
29748
29749 This leaves things a bit vague as far as other processing actions such as
29750 address rewriting are concerned. Exim treats &%Resent-%& header lines as
29751 follows:
29752
29753 .ilist
29754 A &'Resent-From:'& line that just contains the login id of the submitting user
29755 is automatically rewritten in the same way as &'From:'& (see below).
29756 .next
29757 If there's a rewriting rule for a particular header line, it is also applied to
29758 &%Resent-%& header lines of the same type. For example, a rule that rewrites
29759 &'From:'& also rewrites &'Resent-From:'&.
29760 .next
29761 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
29762 also removed.
29763 .next
29764 For a locally-submitted message,
29765 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
29766 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
29767 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
29768 included in log lines in this case.
29769 .next
29770 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
29771 &%Resent-%& header lines are present.
29772 .endlist
29773
29774
29775
29776
29777 .section "The Auto-Submitted: header line" "SECID221"
29778 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
29779 includes the header line:
29780 .code
29781 Auto-Submitted: auto-replied
29782 .endd
29783
29784 .section "The Bcc: header line" "SECID222"
29785 .cindex "&'Bcc:'& header line"
29786 If Exim is called with the &%-t%& option, to take recipient addresses from a
29787 message's header, it removes any &'Bcc:'& header line that may exist (after
29788 extracting its addresses). If &%-t%& is not present on the command line, any
29789 existing &'Bcc:'& is not removed.
29790
29791
29792 .section "The Date: header line" "SECID223"
29793 .cindex "&'Date:'& header line"
29794 If a locally-generated or submission-mode message has no &'Date:'& header line,
29795 Exim adds one, using the current date and time, unless the
29796 &%suppress_local_fixups%& control has been specified.
29797
29798 .section "The Delivery-date: header line" "SECID224"
29799 .cindex "&'Delivery-date:'& header line"
29800 .oindex "&%delivery_date_remove%&"
29801 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
29802 set. Exim can be configured to add them to the final delivery of messages. (See
29803 the generic &%delivery_date_add%& transport option.) They should not be present
29804 in messages in transit. If the &%delivery_date_remove%& configuration option is
29805 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
29806 messages.
29807
29808
29809 .section "The Envelope-to: header line" "SECID225"
29810 .cindex "&'Envelope-to:'& header line"
29811 .oindex "&%envelope_to_remove%&"
29812 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
29813 Exim can be configured to add them to the final delivery of messages. (See the
29814 generic &%envelope_to_add%& transport option.) They should not be present in
29815 messages in transit. If the &%envelope_to_remove%& configuration option is set
29816 (the default), Exim removes &'Envelope-to:'& header lines from incoming
29817 messages.
29818
29819
29820 .section "The From: header line" "SECTthefrohea"
29821 .cindex "&'From:'& header line"
29822 .cindex "Sendmail compatibility" "&""From""& line"
29823 .cindex "message" "submission"
29824 .cindex "submission mode"
29825 If a submission-mode message does not contain a &'From:'& header line, Exim
29826 adds one if either of the following conditions is true:
29827
29828 .ilist
29829 The envelope sender address is not empty (that is, this is not a bounce
29830 message). The added header line copies the envelope sender address.
29831 .next
29832 .vindex "&$authenticated_id$&"
29833 The SMTP session is authenticated and &$authenticated_id$& is not empty.
29834 .olist
29835 .vindex "&$qualify_domain$&"
29836 If no domain is specified by the submission control, the local part is
29837 &$authenticated_id$& and the domain is &$qualify_domain$&.
29838 .next
29839 If a non-empty domain is specified by the submission control, the local
29840 part is &$authenticated_id$&, and the domain is the specified domain.
29841 .next
29842 If an empty domain is specified by the submission control,
29843 &$authenticated_id$& is assumed to be the complete address.
29844 .endlist
29845 .endlist
29846
29847 A non-empty envelope sender takes precedence.
29848
29849 If a locally-generated incoming message does not contain a &'From:'& header
29850 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
29851 containing the sender's address. The calling user's login name and full name
29852 are used to construct the address, as described in section &<<SECTconstr>>&.
29853 They are obtained from the password data by calling &[getpwuid()]& (but see the
29854 &%unknown_login%& configuration option). The address is qualified with
29855 &%qualify_domain%&.
29856
29857 For compatibility with Sendmail, if an incoming, non-SMTP message has a
29858 &'From:'& header line containing just the unqualified login name of the calling
29859 user, this is replaced by an address containing the user's login name and full
29860 name as described in section &<<SECTconstr>>&.
29861
29862
29863 .section "The Message-ID: header line" "SECID226"
29864 .cindex "&'Message-ID:'& header line"
29865 .cindex "message" "submission"
29866 .oindex "&%message_id_header_text%&"
29867 If a locally-generated or submission-mode incoming message does not contain a
29868 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
29869 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
29870 to the message. If there are any &'Resent-:'& headers in the message, it
29871 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
29872 message id, preceded by the letter E to ensure it starts with a letter, and
29873 followed by @ and the primary host name. Additional information can be included
29874 in this header line by setting the &%message_id_header_text%& and/or
29875 &%message_id_header_domain%& options.
29876
29877
29878 .section "The Received: header line" "SECID227"
29879 .cindex "&'Received:'& header line"
29880 A &'Received:'& header line is added at the start of every message. The
29881 contents are defined by the &%received_header_text%& configuration option, and
29882 Exim automatically adds a semicolon and a timestamp to the configured string.
29883
29884 The &'Received:'& header is generated as soon as the message's header lines
29885 have been received. At this stage, the timestamp in the &'Received:'& header
29886 line is the time that the message started to be received. This is the value
29887 that is seen by the DATA ACL and by the &[local_scan()]& function.
29888
29889 Once a message is accepted, the timestamp in the &'Received:'& header line is
29890 changed to the time of acceptance, which is (apart from a small delay while the
29891 -H spool file is written) the earliest time at which delivery could start.
29892
29893
29894 .section "The References: header line" "SECID228"
29895 .cindex "&'References:'& header line"
29896 Messages created by the &(autoreply)& transport include a &'References:'&
29897 header line. This is constructed according to the rules that are described in
29898 section 3.64 of RFC 2822 (which states that replies should contain such a
29899 header line), and section 3.14 of RFC 3834 (which states that automatic
29900 responses are not different in this respect). However, because some mail
29901 processing software does not cope well with very long header lines, no more
29902 than 12 message IDs are copied from the &'References:'& header line in the
29903 incoming message. If there are more than 12, the first one and then the final
29904 11 are copied, before adding the message ID of the incoming message.
29905
29906
29907
29908 .section "The Return-path: header line" "SECID229"
29909 .cindex "&'Return-path:'& header line"
29910 .oindex "&%return_path_remove%&"
29911 &'Return-path:'& header lines are defined as something an MTA may insert when
29912 it does the final delivery of messages. (See the generic &%return_path_add%&
29913 transport option.) Therefore, they should not be present in messages in
29914 transit. If the &%return_path_remove%& configuration option is set (the
29915 default), Exim removes &'Return-path:'& header lines from incoming messages.
29916
29917
29918
29919 .section "The Sender: header line" "SECTthesenhea"
29920 .cindex "&'Sender:'& header line"
29921 .cindex "message" "submission"
29922 For a locally-originated message from an untrusted user, Exim may remove an
29923 existing &'Sender:'& header line, and it may add a new one. You can modify
29924 these actions by setting the &%local_sender_retain%& option true, the
29925 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
29926 control setting.
29927
29928 When a local message is received from an untrusted user and
29929 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
29930 control has not been set, a check is made to see if the address given in the
29931 &'From:'& header line is the correct (local) sender of the message. The address
29932 that is expected has the login name as the local part and the value of
29933 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
29934 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
29935 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
29936 line is added to the message.
29937
29938 If you set &%local_from_check%& false, this checking does not occur. However,
29939 the removal of an existing &'Sender:'& line still happens, unless you also set
29940 &%local_sender_retain%& to be true. It is not possible to set both of these
29941 options true at the same time.
29942
29943 .cindex "submission mode"
29944 By default, no processing of &'Sender:'& header lines is done for messages
29945 received over TCP/IP or for messages submitted by trusted users. However, when
29946 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
29947 not specified on the submission control, the following processing takes place:
29948
29949 .vindex "&$authenticated_id$&"
29950 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
29951 authenticated, and &$authenticated_id$& is not empty, a sender address is
29952 created as follows:
29953
29954 .ilist
29955 .vindex "&$qualify_domain$&"
29956 If no domain is specified by the submission control, the local part is
29957 &$authenticated_id$& and the domain is &$qualify_domain$&.
29958 .next
29959 If a non-empty domain is specified by the submission control, the local part
29960 is &$authenticated_id$&, and the domain is the specified domain.
29961 .next
29962 If an empty domain is specified by the submission control,
29963 &$authenticated_id$& is assumed to be the complete address.
29964 .endlist
29965
29966 This address is compared with the address in the &'From:'& header line. If they
29967 are different, a &'Sender:'& header line containing the created address is
29968 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
29969 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
29970
29971 .cindex "return path" "created from &'Sender:'&"
29972 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
29973 the message (the envelope sender address) is changed to be the same address,
29974 except in the case of submission mode when &%sender_retain%& is specified.
29975
29976
29977
29978 .section "Adding and removing header lines in routers and transports" &&&
29979 "SECTheadersaddrem"
29980 .cindex "header lines" "adding; in router or transport"
29981 .cindex "header lines" "removing; in router or transport"
29982 When a message is delivered, the addition and removal of header lines can be
29983 specified in a system filter, or on any of the routers and transports that
29984 process the message. Section &<<SECTaddremheasys>>& contains details about
29985 modifying headers in a system filter. Header lines can also be added in an ACL
29986 as a message is received (see section &<<SECTaddheadacl>>&).
29987
29988 In contrast to what happens in a system filter, header modifications that are
29989 specified on routers and transports apply only to the particular recipient
29990 addresses that are being processed by those routers and transports. These
29991 changes do not actually take place until a copy of the message is being
29992 transported. Therefore, they do not affect the basic set of header lines, and
29993 they do not affect the values of the variables that refer to header lines.
29994
29995 &*Note*&: In particular, this means that any expansions in the configuration of
29996 the transport cannot refer to the modified header lines, because such
29997 expansions all occur before the message is actually transported.
29998
29999 For both routers and transports, the result of expanding a &%headers_add%&
30000 option must be in the form of one or more RFC 2822 header lines, separated by
30001 newlines (coded as &"\n"&). For example:
30002 .code
30003 headers_add = X-added-header: added by $primary_hostname\n\
30004 X-added-second: another added header line
30005 .endd
30006 Exim does not check the syntax of these added header lines.
30007
30008 The result of expanding &%headers_remove%& must consist of a colon-separated
30009 list of header names. This is confusing, because header names themselves are
30010 often terminated by colons. In this case, the colons are the list separators,
30011 not part of the names. For example:
30012 .code
30013 headers_remove = return-receipt-to:acknowledge-to
30014 .endd
30015 When &%headers_add%& or &%headers_remove%& is specified on a router, its value
30016 is expanded at routing time, and then associated with all addresses that are
30017 accepted by that router, and also with any new addresses that it generates. If
30018 an address passes through several routers as a result of aliasing or
30019 forwarding, the changes are cumulative.
30020
30021 .oindex "&%unseen%&"
30022 However, this does not apply to multiple routers that result from the use of
30023 the &%unseen%& option. Any header modifications that were specified by the
30024 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
30025
30026 Addresses that end up with different &%headers_add%& or &%headers_remove%&
30027 settings cannot be delivered together in a batch, so a transport is always
30028 dealing with a set of addresses that have the same header-processing
30029 requirements.
30030
30031 The transport starts by writing the original set of header lines that arrived
30032 with the message, possibly modified by the system filter. As it writes out
30033 these lines, it consults the list of header names that were attached to the
30034 recipient address(es) by &%headers_remove%& options in routers, and it also
30035 consults the transport's own &%headers_remove%& option. Header lines whose
30036 names are on either of these lists are not written out. If there are multiple
30037 instances of any listed header, they are all skipped.
30038
30039 After the remaining original header lines have been written, new header
30040 lines that were specified by routers' &%headers_add%& options are written, in
30041 the order in which they were attached to the address. These are followed by any
30042 header lines specified by the transport's &%headers_add%& option.
30043
30044 This way of handling header line modifications in routers and transports has
30045 the following consequences:
30046
30047 .ilist
30048 The original set of header lines, possibly modified by the system filter,
30049 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
30050 to it, at all times.
30051 .next
30052 Header lines that are added by a router's
30053 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
30054 expansion syntax in subsequent routers or the transport.
30055 .next
30056 Conversely, header lines that are specified for removal by &%headers_remove%&
30057 in a router remain visible to subsequent routers and the transport.
30058 .next
30059 Headers added to an address by &%headers_add%& in a router cannot be removed by
30060 a later router or by a transport.
30061 .next
30062 An added header can refer to the contents of an original header that is to be
30063 removed, even it has the same name as the added header. For example:
30064 .code
30065 headers_remove = subject
30066 headers_add = Subject: new subject (was: $h_subject:)
30067 .endd
30068 .endlist
30069
30070 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
30071 for a &(redirect)& router that has the &%one_time%& option set.
30072
30073
30074
30075
30076
30077 .section "Constructed addresses" "SECTconstr"
30078 .cindex "address" "constructed"
30079 .cindex "constructed address"
30080 When Exim constructs a sender address for a locally-generated message, it uses
30081 the form
30082 .display
30083 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
30084 .endd
30085 For example:
30086 .code
30087 Zaphod Beeblebrox <zaphod@end.univ.example>
30088 .endd
30089 The user name is obtained from the &%-F%& command line option if set, or
30090 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
30091 &"gecos"& field from the password entry. If the &"gecos"& field contains an
30092 ampersand character, this is replaced by the login name with the first letter
30093 upper cased, as is conventional in a number of operating systems. See the
30094 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
30095 The &%unknown_username%& option can be used to specify user names in cases when
30096 there is no password file entry.
30097
30098 .cindex "RFC 2047"
30099 In all cases, the user name is made to conform to RFC 2822 by quoting all or
30100 parts of it if necessary. In addition, if it contains any non-printing
30101 characters, it is encoded as described in RFC 2047, which defines a way of
30102 including non-ASCII characters in header lines. The value of the
30103 &%headers_charset%& option specifies the name of the encoding that is used (the
30104 characters are assumed to be in this encoding). The setting of
30105 &%print_topbitchars%& controls whether characters with the top bit set (that
30106 is, with codes greater than 127) count as printing characters or not.
30107
30108
30109
30110 .section "Case of local parts" "SECID230"
30111 .cindex "case of local parts"
30112 .cindex "local part" "case of"
30113 RFC 2822 states that the case of letters in the local parts of addresses cannot
30114 be assumed to be non-significant. Exim preserves the case of local parts of
30115 addresses, but by default it uses a lower-cased form when it is routing,
30116 because on most Unix systems, usernames are in lower case and case-insensitive
30117 routing is required. However, any particular router can be made to use the
30118 original case for local parts by setting the &%caseful_local_part%& generic
30119 router option.
30120
30121 .cindex "mixed-case login names"
30122 If you must have mixed-case user names on your system, the best way to proceed,
30123 assuming you want case-independent handling of incoming email, is to set up
30124 your first router to convert incoming local parts in your domains to the
30125 correct case by means of a file lookup. For example:
30126 .code
30127 correct_case:
30128 driver = redirect
30129 domains = +local_domains
30130 data = ${lookup{$local_part}cdb\
30131 {/etc/usercased.cdb}{$value}fail}\
30132 @$domain
30133 .endd
30134 For this router, the local part is forced to lower case by the default action
30135 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
30136 up a new local part in the correct case. If you then set &%caseful_local_part%&
30137 on any subsequent routers which process your domains, they will operate on
30138 local parts with the correct case in a case-sensitive manner.
30139
30140
30141
30142 .section "Dots in local parts" "SECID231"
30143 .cindex "dot" "in local part"
30144 .cindex "local part" "dots in"
30145 RFC 2822 forbids empty components in local parts. That is, an unquoted local
30146 part may not begin or end with a dot, nor have two consecutive dots in the
30147 middle. However, it seems that many MTAs do not enforce this, so Exim permits
30148 empty components for compatibility.
30149
30150
30151
30152 .section "Rewriting addresses" "SECID232"
30153 .cindex "rewriting" "addresses"
30154 Rewriting of sender and recipient addresses, and addresses in headers, can
30155 happen automatically, or as the result of configuration options, as described
30156 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
30157 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
30158
30159 Automatic rewriting includes qualification, as mentioned above. The other case
30160 in which it can happen is when an incomplete non-local domain is given. The
30161 routing process may cause this to be expanded into the full domain name. For
30162 example, a header such as
30163 .code
30164 To: hare@teaparty
30165 .endd
30166 might get rewritten as
30167 .code
30168 To: hare@teaparty.wonderland.fict.example
30169 .endd
30170 Rewriting as a result of routing is the one kind of message processing that
30171 does not happen at input time, as it cannot be done until the address has
30172 been routed.
30173
30174 Strictly, one should not do &'any'& deliveries of a message until all its
30175 addresses have been routed, in case any of the headers get changed as a
30176 result of routing. However, doing this in practice would hold up many
30177 deliveries for unreasonable amounts of time, just because one address could not
30178 immediately be routed. Exim therefore does not delay other deliveries when
30179 routing of one or more addresses is deferred.
30180 .ecindex IIDmesproc
30181
30182
30183
30184 . ////////////////////////////////////////////////////////////////////////////
30185 . ////////////////////////////////////////////////////////////////////////////
30186
30187 .chapter "SMTP processing" "CHAPSMTP"
30188 .scindex IIDsmtpproc1 "SMTP" "processing details"
30189 .scindex IIDsmtpproc2 "LMTP" "processing details"
30190 Exim supports a number of different ways of using the SMTP protocol, and its
30191 LMTP variant, which is an interactive protocol for transferring messages into a
30192 closed mail store application. This chapter contains details of how SMTP is
30193 processed. For incoming mail, the following are available:
30194
30195 .ilist
30196 SMTP over TCP/IP (Exim daemon or &'inetd'&);
30197 .next
30198 SMTP over the standard input and output (the &%-bs%& option);
30199 .next
30200 Batched SMTP on the standard input (the &%-bS%& option).
30201 .endlist
30202
30203 For mail delivery, the following are available:
30204
30205 .ilist
30206 SMTP over TCP/IP (the &(smtp)& transport);
30207 .next
30208 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
30209 &"lmtp"&);
30210 .next
30211 LMTP over a pipe to a process running in the local host (the &(lmtp)&
30212 transport);
30213 .next
30214 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
30215 the &%use_bsmtp%& option set).
30216 .endlist
30217
30218 &'Batched SMTP'& is the name for a process in which batches of messages are
30219 stored in or read from files (or pipes), in a format in which SMTP commands are
30220 used to contain the envelope information.
30221
30222
30223
30224 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
30225 .cindex "SMTP" "outgoing over TCP/IP"
30226 .cindex "outgoing SMTP over TCP/IP"
30227 .cindex "LMTP" "over TCP/IP"
30228 .cindex "outgoing LMTP over TCP/IP"
30229 .cindex "EHLO"
30230 .cindex "HELO"
30231 .cindex "SIZE option on MAIL command"
30232 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
30233 The &%protocol%& option selects which protocol is to be used, but the actual
30234 processing is the same in both cases.
30235
30236 If, in response to its EHLO command, Exim is told that the SIZE
30237 parameter is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
30238 command. The value of <&'n'&> is the message size plus the value of the
30239 &%size_addition%& option (default 1024) to allow for additions to the message
30240 such as per-transport header lines, or changes made in a
30241 .cindex "transport" "filter"
30242 .cindex "filter" "transport filter"
30243 transport filter. If &%size_addition%& is set negative, the use of SIZE is
30244 suppressed.
30245
30246 If the remote server advertises support for PIPELINING, Exim uses the
30247 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
30248 required for the transaction.
30249
30250 If the remote server advertises support for the STARTTLS command, and Exim
30251 was built to support TLS encryption, it tries to start a TLS session unless the
30252 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
30253
30254 If the remote server advertises support for the AUTH command, Exim scans
30255 the authenticators configuration for any suitable client settings, as described
30256 in chapter &<<CHAPSMTPAUTH>>&.
30257
30258 .cindex "carriage return"
30259 .cindex "linefeed"
30260 Responses from the remote host are supposed to be terminated by CR followed by
30261 LF. However, there are known to be hosts that do not send CR characters, so in
30262 order to be able to interwork with such hosts, Exim treats LF on its own as a
30263 line terminator.
30264
30265 If a message contains a number of different addresses, all those with the same
30266 characteristics (for example, the same envelope sender) that resolve to the
30267 same set of hosts, in the same order, are sent in a single SMTP transaction,
30268 even if they are for different domains, unless there are more than the setting
30269 of the &%max_rcpts%& option in the &(smtp)& transport allows, in which case
30270 they are split into groups containing no more than &%max_rcpts%& addresses
30271 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
30272 in parallel sessions. The order of hosts with identical MX values is not
30273 significant when checking whether addresses can be batched in this way.
30274
30275 When the &(smtp)& transport suffers a temporary failure that is not
30276 message-related, Exim updates its transport-specific database, which contains
30277 records indexed by host name that remember which messages are waiting for each
30278 particular host. It also updates the retry database with new retry times.
30279
30280 .cindex "hints database" "retry keys"
30281 Exim's retry hints are based on host name plus IP address, so if one address of
30282 a multi-homed host is broken, it will soon be skipped most of the time.
30283 See the next section for more detail about error handling.
30284
30285 .cindex "SMTP" "passed connection"
30286 .cindex "SMTP" "batching over TCP/IP"
30287 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
30288 looks in the hints database for the transport to see if there are any queued
30289 messages waiting for the host to which it is connected. If it finds one, it
30290 creates a new Exim process using the &%-MC%& option (which can only be used by
30291 a process running as root or the Exim user) and passes the TCP/IP socket to it
30292 so that it can deliver another message using the same socket. The new process
30293 does only those deliveries that are routed to the connected host, and may in
30294 turn pass the socket on to a third process, and so on.
30295
30296 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
30297 limit the number of messages sent down a single TCP/IP connection.
30298
30299 .cindex "asterisk" "after IP address"
30300 The second and subsequent messages delivered down an existing connection are
30301 identified in the main log by the addition of an asterisk after the closing
30302 square bracket of the IP address.
30303
30304
30305
30306
30307 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
30308 .cindex "error" "in outgoing SMTP"
30309 .cindex "SMTP" "errors in outgoing"
30310 .cindex "host" "error"
30311 Three different kinds of error are recognized for outgoing SMTP: host errors,
30312 message errors, and recipient errors.
30313
30314 .vlist
30315 .vitem "&*Host errors*&"
30316 A host error is not associated with a particular message or with a
30317 particular recipient of a message. The host errors are:
30318
30319 .ilist
30320 Connection refused or timed out,
30321 .next
30322 Any error response code on connection,
30323 .next
30324 Any error response code to EHLO or HELO,
30325 .next
30326 Loss of connection at any time, except after &"."&,
30327 .next
30328 I/O errors at any time,
30329 .next
30330 Timeouts during the session, other than in response to MAIL, RCPT or
30331 the &"."& at the end of the data.
30332 .endlist ilist
30333
30334 For a host error, a permanent error response on connection, or in response to
30335 EHLO, causes all addresses routed to the host to be failed. Any other host
30336 error causes all addresses to be deferred, and retry data to be created for the
30337 host. It is not tried again, for any message, until its retry time arrives. If
30338 the current set of addresses are not all delivered in this run (to some
30339 alternative host), the message is added to the list of those waiting for this
30340 host, so if it is still undelivered when a subsequent successful delivery is
30341 made to the host, it will be sent down the same SMTP connection.
30342
30343 .vitem "&*Message errors*&"
30344 .cindex "message" "error"
30345 A message error is associated with a particular message when sent to a
30346 particular host, but not with a particular recipient of the message. The
30347 message errors are:
30348
30349 .ilist
30350 Any error response code to MAIL, DATA, or the &"."& that terminates
30351 the data,
30352 .next
30353 Timeout after MAIL,
30354 .next
30355 Timeout or loss of connection after the &"."& that terminates the data. A
30356 timeout after the DATA command itself is treated as a host error, as is loss of
30357 connection at any other time.
30358 .endlist ilist
30359
30360 For a message error, a permanent error response (5&'xx'&) causes all addresses
30361 to be failed, and a delivery error report to be returned to the sender. A
30362 temporary error response (4&'xx'&), or one of the timeouts, causes all
30363 addresses to be deferred. Retry data is not created for the host, but instead,
30364 a retry record for the combination of host plus message id is created. The
30365 message is not added to the list of those waiting for this host. This ensures
30366 that the failing message will not be sent to this host again until the retry
30367 time arrives. However, other messages that are routed to the host are not
30368 affected, so if it is some property of the message that is causing the error,
30369 it will not stop the delivery of other mail.
30370
30371 If the remote host specified support for the SIZE parameter in its response
30372 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
30373 over-large message will cause a message error because the error arrives as a
30374 response to MAIL.
30375
30376 .vitem "&*Recipient errors*&"
30377 .cindex "recipient" "error"
30378 A recipient error is associated with a particular recipient of a message. The
30379 recipient errors are:
30380
30381 .ilist
30382 Any error response to RCPT,
30383 .next
30384 Timeout after RCPT.
30385 .endlist
30386
30387 For a recipient error, a permanent error response (5&'xx'&) causes the
30388 recipient address to be failed, and a bounce message to be returned to the
30389 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
30390 address to be deferred, and routing retry data to be created for it. This is
30391 used to delay processing of the address in subsequent queue runs, until its
30392 routing retry time arrives. This applies to all messages, but because it
30393 operates only in queue runs, one attempt will be made to deliver a new message
30394 to the failing address before the delay starts to operate. This ensures that,
30395 if the failure is really related to the message rather than the recipient
30396 (&"message too big for this recipient"& is a possible example), other messages
30397 have a chance of getting delivered. If a delivery to the address does succeed,
30398 the retry information gets cleared, so all stuck messages get tried again, and
30399 the retry clock is reset.
30400
30401 The message is not added to the list of those waiting for this host. Use of the
30402 host for other messages is unaffected, and except in the case of a timeout,
30403 other recipients are processed independently, and may be successfully delivered
30404 in the current SMTP session. After a timeout it is of course impossible to
30405 proceed with the session, so all addresses get deferred. However, those other
30406 than the one that failed do not suffer any subsequent retry delays. Therefore,
30407 if one recipient is causing trouble, the others have a chance of getting
30408 through when a subsequent delivery attempt occurs before the failing
30409 recipient's retry time.
30410 .endlist
30411
30412 In all cases, if there are other hosts (or IP addresses) available for the
30413 current set of addresses (for example, from multiple MX records), they are
30414 tried in this run for any undelivered addresses, subject of course to their
30415 own retry data. In other words, recipient error retry data does not take effect
30416 until the next delivery attempt.
30417
30418 Some hosts have been observed to give temporary error responses to every
30419 MAIL command at certain times (&"insufficient space"& has been seen). It
30420 would be nice if such circumstances could be recognized, and defer data for the
30421 host itself created, but this is not possible within the current Exim design.
30422 What actually happens is that retry data for every (host, message) combination
30423 is created.
30424
30425 The reason that timeouts after MAIL and RCPT are treated specially is that
30426 these can sometimes arise as a result of the remote host's verification
30427 procedures. Exim makes this assumption, and treats them as if a temporary error
30428 response had been received. A timeout after &"."& is treated specially because
30429 it is known that some broken implementations fail to recognize the end of the
30430 message if the last character of the last line is a binary zero. Thus, it is
30431 helpful to treat this case as a message error.
30432
30433 Timeouts at other times are treated as host errors, assuming a problem with the
30434 host, or the connection to it. If a timeout after MAIL, RCPT,
30435 or &"."& is really a connection problem, the assumption is that at the next try
30436 the timeout is likely to occur at some other point in the dialogue, causing it
30437 then to be treated as a host error.
30438
30439 There is experimental evidence that some MTAs drop the connection after the
30440 terminating &"."& if they do not like the contents of the message for some
30441 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
30442 should be given. That is why Exim treats this case as a message rather than a
30443 host error, in order not to delay other messages to the same host.
30444
30445
30446
30447
30448 .section "Incoming SMTP messages over TCP/IP" "SECID233"
30449 .cindex "SMTP" "incoming over TCP/IP"
30450 .cindex "incoming SMTP over TCP/IP"
30451 .cindex "inetd"
30452 .cindex "daemon"
30453 Incoming SMTP messages can be accepted in one of two ways: by running a
30454 listening daemon, or by using &'inetd'&. In the latter case, the entry in
30455 &_/etc/inetd.conf_& should be like this:
30456 .code
30457 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
30458 .endd
30459 Exim distinguishes between this case and the case of a locally running user
30460 agent using the &%-bs%& option by checking whether or not the standard input is
30461 a socket. When it is, either the port must be privileged (less than 1024), or
30462 the caller must be root or the Exim user. If any other user passes a socket
30463 with an unprivileged port number, Exim prints a message on the standard error
30464 stream and exits with an error code.
30465
30466 By default, Exim does not make a log entry when a remote host connects or
30467 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
30468 unexpected. It can be made to write such log entries by setting the
30469 &%smtp_connection%& log selector.
30470
30471 .cindex "carriage return"
30472 .cindex "linefeed"
30473 Commands from the remote host are supposed to be terminated by CR followed by
30474 LF. However, there are known to be hosts that do not send CR characters. In
30475 order to be able to interwork with such hosts, Exim treats LF on its own as a
30476 line terminator.
30477 Furthermore, because common code is used for receiving messages from all
30478 sources, a CR on its own is also interpreted as a line terminator. However, the
30479 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
30480
30481 .cindex "EHLO" "invalid data"
30482 .cindex "HELO" "invalid data"
30483 One area that sometimes gives rise to problems concerns the EHLO or
30484 HELO commands. Some clients send syntactically invalid versions of these
30485 commands, which Exim rejects by default. (This is nothing to do with verifying
30486 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
30487 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
30488 match the broken hosts that send invalid commands.
30489
30490 .cindex "SIZE option on MAIL command"
30491 .cindex "MAIL" "SIZE option"
30492 The amount of disk space available is checked whenever SIZE is received on
30493 a MAIL command, independently of whether &%message_size_limit%& or
30494 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
30495 false. A temporary error is given if there is not enough space. If
30496 &%check_spool_space%& is set, the check is for that amount of space plus the
30497 value given with SIZE, that is, it checks that the addition of the incoming
30498 message will not reduce the space below the threshold.
30499
30500 When a message is successfully received, Exim includes the local message id in
30501 its response to the final &"."& that terminates the data. If the remote host
30502 logs this text it can help with tracing what has happened to a message.
30503
30504 The Exim daemon can limit the number of simultaneous incoming connections it is
30505 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
30506 number of simultaneous incoming connections from a single remote host (see the
30507 &%smtp_accept_max_per_host%& option). Additional connection attempts are
30508 rejected using the SMTP temporary error code 421.
30509
30510 The Exim daemon does not rely on the SIGCHLD signal to detect when a
30511 subprocess has finished, as this can get lost at busy times. Instead, it looks
30512 for completed subprocesses every time it wakes up. Provided there are other
30513 things happening (new incoming calls, starts of queue runs), completed
30514 processes will be noticed and tidied away. On very quiet systems you may
30515 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
30516 it will be noticed when the daemon next wakes up.
30517
30518 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
30519 and can also be set up to reject SMTP calls from non-reserved hosts at times of
30520 high system load &-- for details see the &%smtp_accept_reserve%&,
30521 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
30522 applies in both the daemon and &'inetd'& cases.
30523
30524 Exim normally starts a delivery process for each message received, though this
30525 can be varied by means of the &%-odq%& command line option and the
30526 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
30527 number of simultaneously running delivery processes started in this way from
30528 SMTP input can be limited by the &%smtp_accept_queue%& and
30529 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
30530 subsequently received messages are just put on the input queue without starting
30531 a delivery process.
30532
30533 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
30534 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
30535 started up from the &'inetd'& daemon, because in that case each connection is
30536 handled by an entirely independent Exim process. Control by load average is,
30537 however, available with &'inetd'&.
30538
30539 Exim can be configured to verify addresses in incoming SMTP commands as they
30540 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
30541 to rewrite addresses at this time &-- before any syntax checking is done. See
30542 section &<<SECTrewriteS>>&.
30543
30544 Exim can also be configured to limit the rate at which a client host submits
30545 MAIL and RCPT commands in a single SMTP session. See the
30546 &%smtp_ratelimit_hosts%& option.
30547
30548
30549
30550 .section "Unrecognized SMTP commands" "SECID234"
30551 .cindex "SMTP" "unrecognized commands"
30552 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
30553 commands during a single SMTP connection, it drops the connection after sending
30554 the error response to the last command. The default value for
30555 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
30556 abuse that subvert web servers into making connections to SMTP ports; in these
30557 circumstances, a number of non-SMTP lines are sent first.
30558
30559
30560 .section "Syntax and protocol errors in SMTP commands" "SECID235"
30561 .cindex "SMTP" "syntax errors"
30562 .cindex "SMTP" "protocol errors"
30563 A syntax error is detected if an SMTP command is recognized, but there is
30564 something syntactically wrong with its data, for example, a malformed email
30565 address in a RCPT command. Protocol errors include invalid command
30566 sequencing such as RCPT before MAIL. If Exim receives more than
30567 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
30568 drops the connection after sending the error response to the last command. The
30569 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
30570 broken clients that loop sending bad commands (yes, it has been seen).
30571
30572
30573
30574 .section "Use of non-mail SMTP commands" "SECID236"
30575 .cindex "SMTP" "non-mail commands"
30576 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
30577 DATA. Exim counts such commands, and drops the connection if there are too
30578 many of them in a single SMTP session. This action catches some
30579 denial-of-service attempts and things like repeated failing AUTHs, or a mad
30580 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
30581 defines what &"too many"& means. Its default value is 10.
30582
30583 When a new message is expected, one occurrence of RSET is not counted. This
30584 allows a client to send one RSET between messages (this is not necessary,
30585 but some clients do it). Exim also allows one uncounted occurrence of HELO
30586 or EHLO, and one occurrence of STARTTLS between messages. After
30587 starting up a TLS session, another EHLO is expected, and so it too is not
30588 counted.
30589
30590 The first occurrence of AUTH in a connection, or immediately following
30591 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
30592 RCPT, DATA, and QUIT are counted.
30593
30594 You can control which hosts are subject to the limit set by
30595 &%smtp_accept_max_nonmail%& by setting
30596 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
30597 the limit apply to all hosts. This option means that you can exclude any
30598 specific badly-behaved hosts that you have to live with.
30599
30600
30601
30602
30603 .section "The VRFY and EXPN commands" "SECID237"
30604 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
30605 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
30606 appropriate) in order to decide whether the command should be accepted or not.
30607 If no ACL is defined, the command is rejected.
30608
30609 .cindex "VRFY" "processing"
30610 When VRFY is accepted, it runs exactly the same code as when Exim is
30611 called with the &%-bv%& option.
30612
30613 .cindex "EXPN" "processing"
30614 When EXPN is accepted, a single-level expansion of the address is done.
30615 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
30616 than a verification (the &%-bv%& option). If an unqualified local part is given
30617 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
30618 of VRFY and EXPN commands are logged on the main and reject logs, and
30619 VRFY verification failures are logged on the main log for consistency with
30620 RCPT failures.
30621
30622
30623
30624 .section "The ETRN command" "SECTETRN"
30625 .cindex "ETRN" "processing"
30626 RFC 1985 describes an SMTP command called ETRN that is designed to
30627 overcome the security problems of the TURN command (which has fallen into
30628 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
30629 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
30630 should be accepted or not. If no ACL is defined, the command is rejected.
30631
30632 The ETRN command is concerned with &"releasing"& messages that are awaiting
30633 delivery to certain hosts. As Exim does not organize its message queue by host,
30634 the only form of ETRN that is supported by default is the one where the
30635 text starts with the &"#"& prefix, in which case the remainder of the text is
30636 specific to the SMTP server. A valid ETRN command causes a run of Exim with
30637 the &%-R%& option to happen, with the remainder of the ETRN text as its
30638 argument. For example,
30639 .code
30640 ETRN #brigadoon
30641 .endd
30642 runs the command
30643 .code
30644 exim -R brigadoon
30645 .endd
30646 which causes a delivery attempt on all messages with undelivered addresses
30647 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
30648 default), Exim prevents the simultaneous execution of more than one queue run
30649 for the same argument string as a result of an ETRN command. This stops
30650 a misbehaving client from starting more than one queue runner at once.
30651
30652 .cindex "hints database" "ETRN serialization"
30653 Exim implements the serialization by means of a hints database in which a
30654 record is written whenever a process is started by ETRN, and deleted when
30655 the process completes. However, Exim does not keep the SMTP session waiting for
30656 the ETRN process to complete. Once ETRN is accepted, the client is sent
30657 a &"success"& return code. Obviously there is scope for hints records to get
30658 left lying around if there is a system or program crash. To guard against this,
30659 Exim ignores any records that are more than six hours old.
30660
30661 .oindex "&%smtp_etrn_command%&"
30662 For more control over what ETRN does, the &%smtp_etrn_command%& option can
30663 used. This specifies a command that is run whenever ETRN is received,
30664 whatever the form of its argument. For
30665 example:
30666 .code
30667 smtp_etrn_command = /etc/etrn_command $domain \
30668 $sender_host_address
30669 .endd
30670 .vindex "&$domain$&"
30671 The string is split up into arguments which are independently expanded. The
30672 expansion variable &$domain$& is set to the argument of the ETRN command,
30673 and no syntax checking is done on the contents of this argument. Exim does not
30674 wait for the command to complete, so its status code is not checked. Exim runs
30675 under its own uid and gid when receiving incoming SMTP, so it is not possible
30676 for it to change them before running the command.
30677
30678
30679
30680 .section "Incoming local SMTP" "SECID238"
30681 .cindex "SMTP" "local incoming"
30682 Some user agents use SMTP to pass messages to their local MTA using the
30683 standard input and output, as opposed to passing the envelope on the command
30684 line and writing the message to the standard input. This is supported by the
30685 &%-bs%& option. This form of SMTP is handled in the same way as incoming
30686 messages over TCP/IP (including the use of ACLs), except that the envelope
30687 sender given in a MAIL command is ignored unless the caller is trusted. In
30688 an ACL you can detect this form of SMTP input by testing for an empty host
30689 identification. It is common to have this as the first line in the ACL that
30690 runs for RCPT commands:
30691 .code
30692 accept hosts = :
30693 .endd
30694 This accepts SMTP messages from local processes without doing any other tests.
30695
30696
30697
30698 .section "Outgoing batched SMTP" "SECTbatchSMTP"
30699 .cindex "SMTP" "batched outgoing"
30700 .cindex "batched SMTP output"
30701 Both the &(appendfile)& and &(pipe)& transports can be used for handling
30702 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
30703 be output in BSMTP format. No SMTP responses are possible for this form of
30704 delivery. All it is doing is using SMTP commands as a way of transmitting the
30705 envelope along with the message.
30706
30707 The message is written to the file or pipe preceded by the SMTP commands
30708 MAIL and RCPT, and followed by a line containing a single dot. Lines in
30709 the message that start with a dot have an extra dot added. The SMTP command
30710 HELO is not normally used. If it is required, the &%message_prefix%& option
30711 can be used to specify it.
30712
30713 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
30714 one recipient address at a time by default. However, you can arrange for them
30715 to handle several addresses at once by setting the &%batch_max%& option. When
30716 this is done for BSMTP, messages may contain multiple RCPT commands. See
30717 chapter &<<CHAPbatching>>& for more details.
30718
30719 .vindex "&$host$&"
30720 When one or more addresses are routed to a BSMTP transport by a router that
30721 sets up a host list, the name of the first host on the list is available to the
30722 transport in the variable &$host$&. Here is an example of such a transport and
30723 router:
30724 .code
30725 begin routers
30726 route_append:
30727 driver = manualroute
30728 transport = smtp_appendfile
30729 route_list = domain.example batch.host.example
30730
30731 begin transports
30732 smtp_appendfile:
30733 driver = appendfile
30734 directory = /var/bsmtp/$host
30735 batch_max = 1000
30736 use_bsmtp
30737 user = exim
30738 .endd
30739 This causes messages addressed to &'domain.example'& to be written in BSMTP
30740 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
30741 message (unless there are more than 1000 recipients).
30742
30743
30744
30745 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
30746 .cindex "SMTP" "batched incoming"
30747 .cindex "batched SMTP input"
30748 The &%-bS%& command line option causes Exim to accept one or more messages by
30749 reading SMTP on the standard input, but to generate no responses. If the caller
30750 is trusted, the senders in the MAIL commands are believed; otherwise the
30751 sender is always the caller of Exim. Unqualified senders and receivers are not
30752 rejected (there seems little point) but instead just get qualified. HELO
30753 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
30754 as NOOP; QUIT quits.
30755
30756 No policy checking is done for BSMTP input. That is, no ACL is run at anytime.
30757 In this respect it is like non-SMTP local input.
30758
30759 If an error is detected while reading a message, including a missing &"."& at
30760 the end, Exim gives up immediately. It writes details of the error to the
30761 standard output in a stylized way that the calling program should be able to
30762 make some use of automatically, for example:
30763 .code
30764 554 Unexpected end of file
30765 Transaction started in line 10
30766 Error detected in line 14
30767 .endd
30768 It writes a more verbose version, for human consumption, to the standard error
30769 file, for example:
30770 .code
30771 An error was detected while processing a file of BSMTP input.
30772 The error message was:
30773
30774 501 '>' missing at end of address
30775
30776 The SMTP transaction started in line 10.
30777 The error was detected in line 12.
30778 The SMTP command at fault was:
30779
30780 rcpt to:<malformed@in.com.plete
30781
30782 1 previous message was successfully processed.
30783 The rest of the batch was abandoned.
30784 .endd
30785 The return code from Exim is zero only if there were no errors. It is 1 if some
30786 messages were accepted before an error was detected, and 2 if no messages were
30787 accepted.
30788 .ecindex IIDsmtpproc1
30789 .ecindex IIDsmtpproc2
30790
30791
30792
30793 . ////////////////////////////////////////////////////////////////////////////
30794 . ////////////////////////////////////////////////////////////////////////////
30795
30796 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
30797 "Customizing messages"
30798 When a message fails to be delivered, or remains on the queue for more than a
30799 configured amount of time, Exim sends a message to the original sender, or
30800 to an alternative configured address. The text of these messages is built into
30801 the code of Exim, but it is possible to change it, either by adding a single
30802 string, or by replacing each of the paragraphs by text supplied in a file.
30803
30804 The &'From:'& and &'To:'& header lines are automatically generated; you can
30805 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
30806 option. Exim also adds the line
30807 .code
30808 Auto-Submitted: auto-generated
30809 .endd
30810 to all warning and bounce messages,
30811
30812
30813 .section "Customizing bounce messages" "SECID239"
30814 .cindex "customizing" "bounce message"
30815 .cindex "bounce message" "customizing"
30816 If &%bounce_message_text%& is set, its contents are included in the default
30817 message immediately after &"This message was created automatically by mail
30818 delivery software."& The string is not expanded. It is not used if
30819 &%bounce_message_file%& is set.
30820
30821 When &%bounce_message_file%& is set, it must point to a template file for
30822 constructing error messages. The file consists of a series of text items,
30823 separated by lines consisting of exactly four asterisks. If the file cannot be
30824 opened, default text is used and a message is written to the main and panic
30825 logs. If any text item in the file is empty, default text is used for that
30826 item.
30827
30828 .vindex "&$bounce_recipient$&"
30829 .vindex "&$bounce_return_size_limit$&"
30830 Each item of text that is read from the file is expanded, and there are two
30831 expansion variables which can be of use here: &$bounce_recipient$& is set to
30832 the recipient of an error message while it is being created, and
30833 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
30834 option, rounded to a whole number.
30835
30836 The items must appear in the file in the following order:
30837
30838 .ilist
30839 The first item is included in the headers, and should include at least a
30840 &'Subject:'& header. Exim does not check the syntax of these headers.
30841 .next
30842 The second item forms the start of the error message. After it, Exim lists the
30843 failing addresses with their error messages.
30844 .next
30845 The third item is used to introduce any text from pipe transports that is to be
30846 returned to the sender. It is omitted if there is no such text.
30847 .next
30848 The fourth item is used to introduce the copy of the message that is returned
30849 as part of the error report.
30850 .next
30851 The fifth item is added after the fourth one if the returned message is
30852 truncated because it is bigger than &%return_size_limit%&.
30853 .next
30854 The sixth item is added after the copy of the original message.
30855 .endlist
30856
30857 The default state (&%bounce_message_file%& unset) is equivalent to the
30858 following file, in which the sixth item is empty. The &'Subject:'& and some
30859 other lines have been split in order to fit them on the page:
30860 .code
30861 Subject: Mail delivery failed
30862 ${if eq{$sender_address}{$bounce_recipient}
30863 {: returning message to sender}}
30864 ****
30865 This message was created automatically by mail delivery software.
30866
30867 A message ${if eq{$sender_address}{$bounce_recipient}
30868 {that you sent }{sent by
30869
30870 <$sender_address>
30871
30872 }}could not be delivered to all of its recipients.
30873 This is a permanent error. The following address(es) failed:
30874 ****
30875 The following text was generated during the delivery attempt(s):
30876 ****
30877 ------ This is a copy of the message, including all the headers.
30878 ------
30879 ****
30880 ------ The body of the message is $message_size characters long;
30881 only the first
30882 ------ $bounce_return_size_limit or so are included here.
30883 ****
30884 .endd
30885 .section "Customizing warning messages" "SECTcustwarn"
30886 .cindex "customizing" "warning message"
30887 .cindex "warning of delay" "customizing the message"
30888 The option &%warn_message_file%& can be pointed at a template file for use when
30889 warnings about message delays are created. In this case there are only three
30890 text sections:
30891
30892 .ilist
30893 The first item is included in the headers, and should include at least a
30894 &'Subject:'& header. Exim does not check the syntax of these headers.
30895 .next
30896 The second item forms the start of the warning message. After it, Exim lists
30897 the delayed addresses.
30898 .next
30899 The third item then ends the message.
30900 .endlist
30901
30902 The default state is equivalent to the following file, except that some lines
30903 have been split here, in order to fit them on the page:
30904 .code
30905 Subject: Warning: message $message_exim_id delayed
30906 $warn_message_delay
30907 ****
30908 This message was created automatically by mail delivery software.
30909
30910 A message ${if eq{$sender_address}{$warn_message_recipients}
30911 {that you sent }{sent by
30912
30913 <$sender_address>
30914
30915 }}has not been delivered to all of its recipients after
30916 more than $warn_message_delay on the queue on $primary_hostname.
30917
30918 The message identifier is: $message_exim_id
30919 The subject of the message is: $h_subject
30920 The date of the message is: $h_date
30921
30922 The following address(es) have not yet been delivered:
30923 ****
30924 No action is required on your part. Delivery attempts will
30925 continue for some time, and this warning may be repeated at
30926 intervals if the message remains undelivered. Eventually the
30927 mail delivery software will give up, and when that happens,
30928 the message will be returned to you.
30929 .endd
30930 .vindex "&$warn_message_delay$&"
30931 .vindex "&$warn_message_recipients$&"
30932 However, in the default state the subject and date lines are omitted if no
30933 appropriate headers exist. During the expansion of this file,
30934 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
30935 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
30936 of recipients for the warning message. There may be more than one if there are
30937 multiple addresses with different &%errors_to%& settings on the routers that
30938 handled them.
30939
30940
30941
30942
30943 . ////////////////////////////////////////////////////////////////////////////
30944 . ////////////////////////////////////////////////////////////////////////////
30945
30946 .chapter "Some common configuration settings" "CHAPcomconreq"
30947 This chapter discusses some configuration settings that seem to be fairly
30948 common. More examples and discussion can be found in the Exim book.
30949
30950
30951
30952 .section "Sending mail to a smart host" "SECID240"
30953 .cindex "smart host" "example router"
30954 If you want to send all mail for non-local domains to a &"smart host"&, you
30955 should replace the default &(dnslookup)& router with a router which does the
30956 routing explicitly:
30957 .code
30958 send_to_smart_host:
30959 driver = manualroute
30960 route_list = !+local_domains smart.host.name
30961 transport = remote_smtp
30962 .endd
30963 You can use the smart host's IP address instead of the name if you wish.
30964 If you are using Exim only to submit messages to a smart host, and not for
30965 receiving incoming messages, you can arrange for it to do the submission
30966 synchronously by setting the &%mua_wrapper%& option (see chapter
30967 &<<CHAPnonqueueing>>&).
30968
30969
30970
30971
30972 .section "Using Exim to handle mailing lists" "SECTmailinglists"
30973 .cindex "mailing lists"
30974 Exim can be used to run simple mailing lists, but for large and/or complicated
30975 requirements, the use of additional specialized mailing list software such as
30976 Majordomo or Mailman is recommended.
30977
30978 The &(redirect)& router can be used to handle mailing lists where each list
30979 is maintained in a separate file, which can therefore be managed by an
30980 independent manager. The &%domains%& router option can be used to run these
30981 lists in a separate domain from normal mail. For example:
30982 .code
30983 lists:
30984 driver = redirect
30985 domains = lists.example
30986 file = /usr/lists/$local_part
30987 forbid_pipe
30988 forbid_file
30989 errors_to = $local_part-request@lists.example
30990 no_more
30991 .endd
30992 This router is skipped for domains other than &'lists.example'&. For addresses
30993 in that domain, it looks for a file that matches the local part. If there is no
30994 such file, the router declines, but because &%no_more%& is set, no subsequent
30995 routers are tried, and so the whole delivery fails.
30996
30997 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
30998 expanded into a file name or a pipe delivery, which is usually inappropriate in
30999 a mailing list.
31000
31001 .oindex "&%errors_to%&"
31002 The &%errors_to%& option specifies that any delivery errors caused by addresses
31003 taken from a mailing list are to be sent to the given address rather than the
31004 original sender of the message. However, before acting on this, Exim verifies
31005 the error address, and ignores it if verification fails.
31006
31007 For example, using the configuration above, mail sent to
31008 &'dicts@lists.example'& is passed on to those addresses contained in
31009 &_/usr/lists/dicts_&, with error reports directed to
31010 &'dicts-request@lists.example'&, provided that this address can be verified.
31011 There could be a file called &_/usr/lists/dicts-request_& containing
31012 the address(es) of this particular list's manager(s), but other approaches,
31013 such as setting up an earlier router (possibly using the &%local_part_prefix%&
31014 or &%local_part_suffix%& options) to handle addresses of the form
31015 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
31016
31017
31018
31019 .section "Syntax errors in mailing lists" "SECID241"
31020 .cindex "mailing lists" "syntax errors in"
31021 If an entry in redirection data contains a syntax error, Exim normally defers
31022 delivery of the original address. That means that a syntax error in a mailing
31023 list holds up all deliveries to the list. This may not be appropriate when a
31024 list is being maintained automatically from data supplied by users, and the
31025 addresses are not rigorously checked.
31026
31027 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
31028 entries that fail to parse, noting the incident in the log. If in addition
31029 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
31030 whenever a broken address is skipped. It is usually appropriate to set
31031 &%syntax_errors_to%& to the same address as &%errors_to%&.
31032
31033
31034
31035 .section "Re-expansion of mailing lists" "SECID242"
31036 .cindex "mailing lists" "re-expansion of"
31037 Exim remembers every individual address to which a message has been delivered,
31038 in order to avoid duplication, but it normally stores only the original
31039 recipient addresses with a message. If all the deliveries to a mailing list
31040 cannot be done at the first attempt, the mailing list is re-expanded when the
31041 delivery is next tried. This means that alterations to the list are taken into
31042 account at each delivery attempt, so addresses that have been added to
31043 the list since the message arrived will therefore receive a copy of the
31044 message, even though it pre-dates their subscription.
31045
31046 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
31047 on the &(redirect)& router. If this is done, any addresses generated by the
31048 router that fail to deliver at the first attempt are added to the message as
31049 &"top level"& addresses, and the parent address that generated them is marked
31050 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
31051 subsequent delivery attempts. The disadvantage of this is that if any of the
31052 failing addresses are incorrect, correcting them in the file has no effect on
31053 pre-existing messages.
31054
31055 The original top-level address is remembered with each of the generated
31056 addresses, and is output in any log messages. However, any intermediate parent
31057 addresses are not recorded. This makes a difference to the log only if the
31058 &%all_parents%& selector is set, but for mailing lists there is normally only
31059 one level of expansion anyway.
31060
31061
31062
31063 .section "Closed mailing lists" "SECID243"
31064 .cindex "mailing lists" "closed"
31065 The examples so far have assumed open mailing lists, to which anybody may
31066 send mail. It is also possible to set up closed lists, where mail is accepted
31067 from specified senders only. This is done by making use of the generic
31068 &%senders%& option to restrict the router that handles the list.
31069
31070 The following example uses the same file as a list of recipients and as a list
31071 of permitted senders. It requires three routers:
31072 .code
31073 lists_request:
31074 driver = redirect
31075 domains = lists.example
31076 local_part_suffix = -request
31077 file = /usr/lists/$local_part$local_part_suffix
31078 no_more
31079
31080 lists_post:
31081 driver = redirect
31082 domains = lists.example
31083 senders = ${if exists {/usr/lists/$local_part}\
31084 {lsearch;/usr/lists/$local_part}{*}}
31085 file = /usr/lists/$local_part
31086 forbid_pipe
31087 forbid_file
31088 errors_to = $local_part-request@lists.example
31089 no_more
31090
31091 lists_closed:
31092 driver = redirect
31093 domains = lists.example
31094 allow_fail
31095 data = :fail: $local_part@lists.example is a closed mailing list
31096 .endd
31097 All three routers have the same &%domains%& setting, so for any other domains,
31098 they are all skipped. The first router runs only if the local part ends in
31099 &%-request%&. It handles messages to the list manager(s) by means of an open
31100 mailing list.
31101
31102 The second router runs only if the &%senders%& precondition is satisfied. It
31103 checks for the existence of a list that corresponds to the local part, and then
31104 checks that the sender is on the list by means of a linear search. It is
31105 necessary to check for the existence of the file before trying to search it,
31106 because otherwise Exim thinks there is a configuration error. If the file does
31107 not exist, the expansion of &%senders%& is *, which matches all senders. This
31108 means that the router runs, but because there is no list, declines, and
31109 &%no_more%& ensures that no further routers are run. The address fails with an
31110 &"unrouteable address"& error.
31111
31112 The third router runs only if the second router is skipped, which happens when
31113 a mailing list exists, but the sender is not on it. This router forcibly fails
31114 the address, giving a suitable error message.
31115
31116
31117
31118
31119 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
31120 .cindex "VERP"
31121 .cindex "Variable Envelope Return Paths"
31122 .cindex "envelope sender"
31123 Variable Envelope Return Paths &-- see &url(http://cr.yp.to/proto/verp.txt) &--
31124 are a way of helping mailing list administrators discover which subscription
31125 address is the cause of a particular delivery failure. The idea is to encode
31126 the original recipient address in the outgoing envelope sender address, so that
31127 if the message is forwarded by another host and then subsequently bounces, the
31128 original recipient can be extracted from the recipient address of the bounce.
31129
31130 .oindex &%errors_to%&
31131 .oindex &%return_path%&
31132 Envelope sender addresses can be modified by Exim using two different
31133 facilities: the &%errors_to%& option on a router (as shown in previous mailing
31134 list examples), or the &%return_path%& option on a transport. The second of
31135 these is effective only if the message is successfully delivered to another
31136 host; it is not used for errors detected on the local host (see the description
31137 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
31138 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
31139 .code
31140 verp_smtp:
31141 driver = smtp
31142 max_rcpt = 1
31143 return_path = \
31144 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
31145 {$1-request+$local_part=$domain@your.dom.example}fail}
31146 .endd
31147 This has the effect of rewriting the return path (envelope sender) on outgoing
31148 SMTP messages, if the local part of the original return path ends in
31149 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
31150 local part and domain of the recipient into the return path. Suppose, for
31151 example, that a message whose return path has been set to
31152 &'somelist-request@your.dom.example'& is sent to
31153 &'subscriber@other.dom.example'&. In the transport, the return path is
31154 rewritten as
31155 .code
31156 somelist-request+subscriber=other.dom.example@your.dom.example
31157 .endd
31158 .vindex "&$local_part$&"
31159 For this to work, you must tell Exim to send multiple copies of messages that
31160 have more than one recipient, so that each copy has just one recipient. This is
31161 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
31162 might be sent to several different recipients in the same domain, in which case
31163 &$local_part$& is not available in the transport, because it is not unique.
31164
31165 Unless your host is doing nothing but mailing list deliveries, you should
31166 probably use a separate transport for the VERP deliveries, so as not to use
31167 extra resources in making one-per-recipient copies for other deliveries. This
31168 can easily be done by expanding the &%transport%& option in the router:
31169 .code
31170 dnslookup:
31171 driver = dnslookup
31172 domains = ! +local_domains
31173 transport = \
31174 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
31175 {verp_smtp}{remote_smtp}}
31176 no_more
31177 .endd
31178 If you want to change the return path using &%errors_to%& in a router instead
31179 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
31180 routers that handle mailing list addresses. This will ensure that all delivery
31181 errors, including those detected on the local host, are sent to the VERP
31182 address.
31183
31184 On a host that does no local deliveries and has no manual routing, only the
31185 &(dnslookup)& router needs to be changed. A special transport is not needed for
31186 SMTP deliveries. Every mailing list recipient has its own return path value,
31187 and so Exim must hand them to the transport one at a time. Here is an example
31188 of a &(dnslookup)& router that implements VERP:
31189 .code
31190 verp_dnslookup:
31191 driver = dnslookup
31192 domains = ! +local_domains
31193 transport = remote_smtp
31194 errors_to = \
31195 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
31196 {$1-request+$local_part=$domain@your.dom.example}fail}
31197 no_more
31198 .endd
31199 Before you start sending out messages with VERPed return paths, you must also
31200 configure Exim to accept the bounce messages that come back to those paths.
31201 Typically this is done by setting a &%local_part_suffix%& option for a
31202 router, and using this to route the messages to wherever you want to handle
31203 them.
31204
31205 The overhead incurred in using VERP depends very much on the size of the
31206 message, the number of recipient addresses that resolve to the same remote
31207 host, and the speed of the connection over which the message is being sent. If
31208 a lot of addresses resolve to the same host and the connection is slow, sending
31209 a separate copy of the message for each address may take substantially longer
31210 than sending a single copy with many recipients (for which VERP cannot be
31211 used).
31212
31213
31214
31215
31216
31217
31218 .section "Virtual domains" "SECTvirtualdomains"
31219 .cindex "virtual domains"
31220 .cindex "domain" "virtual"
31221 The phrase &'virtual domain'& is unfortunately used with two rather different
31222 meanings:
31223
31224 .ilist
31225 A domain for which there are no real mailboxes; all valid local parts are
31226 aliases for other email addresses. Common examples are organizational
31227 top-level domains and &"vanity"& domains.
31228 .next
31229 One of a number of independent domains that are all handled by the same host,
31230 with mailboxes on that host, but where the mailbox owners do not necessarily
31231 have login accounts on that host.
31232 .endlist
31233
31234 The first usage is probably more common, and does seem more &"virtual"& than
31235 the second. This kind of domain can be handled in Exim with a straightforward
31236 aliasing router. One approach is to create a separate alias file for each
31237 virtual domain. Exim can test for the existence of the alias file to determine
31238 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
31239 to a router of this form:
31240 .code
31241 virtual:
31242 driver = redirect
31243 domains = dsearch;/etc/mail/virtual
31244 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
31245 no_more
31246 .endd
31247 The &%domains%& option specifies that the router is to be skipped, unless there
31248 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
31249 domain that is being processed. When the router runs, it looks up the local
31250 part in the file to find a new address (or list of addresses). The &%no_more%&
31251 setting ensures that if the lookup fails (leading to &%data%& being an empty
31252 string), Exim gives up on the address without trying any subsequent routers.
31253
31254 This one router can handle all the virtual domains because the alias file names
31255 follow a fixed pattern. Permissions can be arranged so that appropriate people
31256 can edit the different alias files. A successful aliasing operation results in
31257 a new envelope recipient address, which is then routed from scratch.
31258
31259 The other kind of &"virtual"& domain can also be handled in a straightforward
31260 way. One approach is to create a file for each domain containing a list of
31261 valid local parts, and use it in a router like this:
31262 .code
31263 my_domains:
31264 driver = accept
31265 domains = dsearch;/etc/mail/domains
31266 local_parts = lsearch;/etc/mail/domains/$domain
31267 transport = my_mailboxes
31268 .endd
31269 The address is accepted if there is a file for the domain, and the local part
31270 can be found in the file. The &%domains%& option is used to check for the
31271 file's existence because &%domains%& is tested before the &%local_parts%&
31272 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
31273 because that option is tested after &%local_parts%&. The transport is as
31274 follows:
31275 .code
31276 my_mailboxes:
31277 driver = appendfile
31278 file = /var/mail/$domain/$local_part
31279 user = mail
31280 .endd
31281 This uses a directory of mailboxes for each domain. The &%user%& setting is
31282 required, to specify which uid is to be used for writing to the mailboxes.
31283
31284 The configuration shown here is just one example of how you might support this
31285 requirement. There are many other ways this kind of configuration can be set
31286 up, for example, by using a database instead of separate files to hold all the
31287 information about the domains.
31288
31289
31290
31291 .section "Multiple user mailboxes" "SECTmulbox"
31292 .cindex "multiple mailboxes"
31293 .cindex "mailbox" "multiple"
31294 .cindex "local part" "prefix"
31295 .cindex "local part" "suffix"
31296 Heavy email users often want to operate with multiple mailboxes, into which
31297 incoming mail is automatically sorted. A popular way of handling this is to
31298 allow users to use multiple sender addresses, so that replies can easily be
31299 identified. Users are permitted to add prefixes or suffixes to their local
31300 parts for this purpose. The wildcard facility of the generic router options
31301 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
31302 example, consider this router:
31303 .code
31304 userforward:
31305 driver = redirect
31306 check_local_user
31307 file = $home/.forward
31308 local_part_suffix = -*
31309 local_part_suffix_optional
31310 allow_filter
31311 .endd
31312 .vindex "&$local_part_suffix$&"
31313 It runs a user's &_.forward_& file for all local parts of the form
31314 &'username-*'&. Within the filter file the user can distinguish different
31315 cases by testing the variable &$local_part_suffix$&. For example:
31316 .code
31317 if $local_part_suffix contains -special then
31318 save /home/$local_part/Mail/special
31319 endif
31320 .endd
31321 If the filter file does not exist, or does not deal with such addresses, they
31322 fall through to subsequent routers, and, assuming no subsequent use of the
31323 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
31324 control over which suffixes are valid.
31325
31326 Alternatively, a suffix can be used to trigger the use of a different
31327 &_.forward_& file &-- which is the way a similar facility is implemented in
31328 another MTA:
31329 .code
31330 userforward:
31331 driver = redirect
31332 check_local_user
31333 file = $home/.forward$local_part_suffix
31334 local_part_suffix = -*
31335 local_part_suffix_optional
31336 allow_filter
31337 .endd
31338 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
31339 example, &_.forward-special_& is used. Once again, if the appropriate file
31340 does not exist, or does not deal with the address, it is passed on to
31341 subsequent routers, which could, if required, look for an unqualified
31342 &_.forward_& file to use as a default.
31343
31344
31345
31346 .section "Simplified vacation processing" "SECID244"
31347 .cindex "vacation processing"
31348 The traditional way of running the &'vacation'& program is for a user to set up
31349 a pipe command in a &_.forward_& file
31350 (see section &<<SECTspecitredli>>& for syntax details).
31351 This is prone to error by inexperienced users. There are two features of Exim
31352 that can be used to make this process simpler for users:
31353
31354 .ilist
31355 A local part prefix such as &"vacation-"& can be specified on a router which
31356 can cause the message to be delivered directly to the &'vacation'& program, or
31357 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
31358 &_.forward_& file are then much simpler. For example:
31359 .code
31360 spqr, vacation-spqr
31361 .endd
31362 .next
31363 The &%require_files%& generic router option can be used to trigger a
31364 vacation delivery by checking for the existence of a certain file in the
31365 user's home directory. The &%unseen%& generic option should also be used, to
31366 ensure that the original delivery also proceeds. In this case, all the user has
31367 to do is to create a file called, say, &_.vacation_&, containing a vacation
31368 message.
31369 .endlist
31370
31371 Another advantage of both these methods is that they both work even when the
31372 use of arbitrary pipes by users is locked out.
31373
31374
31375
31376 .section "Taking copies of mail" "SECID245"
31377 .cindex "message" "copying every"
31378 Some installations have policies that require archive copies of all messages to
31379 be made. A single copy of each message can easily be taken by an appropriate
31380 command in a system filter, which could, for example, use a different file for
31381 each day's messages.
31382
31383 There is also a shadow transport mechanism that can be used to take copies of
31384 messages that are successfully delivered by local transports, one copy per
31385 delivery. This could be used, &'inter alia'&, to implement automatic
31386 notification of delivery by sites that insist on doing such things.
31387
31388
31389
31390 .section "Intermittently connected hosts" "SECID246"
31391 .cindex "intermittently connected hosts"
31392 It has become quite common (because it is cheaper) for hosts to connect to the
31393 Internet periodically rather than remain connected all the time. The normal
31394 arrangement is that mail for such hosts accumulates on a system that is
31395 permanently connected.
31396
31397 Exim was designed for use on permanently connected hosts, and so it is not
31398 particularly well-suited to use in an intermittently connected environment.
31399 Nevertheless there are some features that can be used.
31400
31401
31402 .section "Exim on the upstream server host" "SECID247"
31403 It is tempting to arrange for incoming mail for the intermittently connected
31404 host to remain on Exim's queue until the client connects. However, this
31405 approach does not scale very well. Two different kinds of waiting message are
31406 being mixed up in the same queue &-- those that cannot be delivered because of
31407 some temporary problem, and those that are waiting for their destination host
31408 to connect. This makes it hard to manage the queue, as well as wasting
31409 resources, because each queue runner scans the entire queue.
31410
31411 A better approach is to separate off those messages that are waiting for an
31412 intermittently connected host. This can be done by delivering these messages
31413 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
31414 format, from where they are transmitted by other software when their
31415 destination connects. This makes it easy to collect all the mail for one host
31416 in a single directory, and to apply local timeout rules on a per-message basis
31417 if required.
31418
31419 On a very small scale, leaving the mail on Exim's queue can be made to work. If
31420 you are doing this, you should configure Exim with a long retry period for the
31421 intermittent host. For example:
31422 .code
31423 cheshire.wonderland.fict.example * F,5d,24h
31424 .endd
31425 This stops a lot of failed delivery attempts from occurring, but Exim remembers
31426 which messages it has queued up for that host. Once the intermittent host comes
31427 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
31428 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
31429 causes all the queued up messages to be delivered, often down a single SMTP
31430 connection. While the host remains connected, any new messages get delivered
31431 immediately.
31432
31433 If the connecting hosts do not have fixed IP addresses, that is, if a host is
31434 issued with a different IP address each time it connects, Exim's retry
31435 mechanisms on the holding host get confused, because the IP address is normally
31436 used as part of the key string for holding retry information. This can be
31437 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
31438 Since this has disadvantages for permanently connected hosts, it is best to
31439 arrange a separate transport for the intermittently connected ones.
31440
31441
31442
31443 .section "Exim on the intermittently connected client host" "SECID248"
31444 The value of &%smtp_accept_queue_per_connection%& should probably be
31445 increased, or even set to zero (that is, disabled) on the intermittently
31446 connected host, so that all incoming messages down a single connection get
31447 delivered immediately.
31448
31449 .cindex "SMTP" "passed connection"
31450 .cindex "SMTP" "multiple deliveries"
31451 .cindex "multiple SMTP deliveries"
31452 Mail waiting to be sent from an intermittently connected host will probably
31453 not have been routed, because without a connection DNS lookups are not
31454 possible. This means that if a normal queue run is done at connection time,
31455 each message is likely to be sent in a separate SMTP session. This can be
31456 avoided by starting the queue run with a command line option beginning with
31457 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
31458 first pass, routing is done but no deliveries take place. The second pass is a
31459 normal queue run; since all the messages have been previously routed, those
31460 destined for the same host are likely to get sent as multiple deliveries in a
31461 single SMTP connection.
31462
31463
31464
31465 . ////////////////////////////////////////////////////////////////////////////
31466 . ////////////////////////////////////////////////////////////////////////////
31467
31468 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
31469 "Exim as a non-queueing client"
31470 .cindex "client, non-queueing"
31471 .cindex "smart host" "suppressing queueing"
31472 On a personal computer, it is a common requirement for all
31473 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
31474 configured to operate that way, for all the popular operating systems.
31475 However, there are some MUAs for Unix-like systems that cannot be so
31476 configured: they submit messages using the command line interface of
31477 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
31478 messages this way.
31479
31480 If the personal computer runs continuously, there is no problem, because it can
31481 run a conventional MTA that handles delivery to the smart host, and deal with
31482 any delays via its queueing mechanism. However, if the computer does not run
31483 continuously or runs different operating systems at different times, queueing
31484 email is not desirable.
31485
31486 There is therefore a requirement for something that can provide the
31487 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
31488 any queueing or retrying facilities. Furthermore, the delivery to the smart
31489 host should be synchronous, so that if it fails, the sending MUA is immediately
31490 informed. In other words, we want something that extends an MUA that submits
31491 to a local MTA via the command line so that it behaves like one that submits
31492 to a remote smart host using TCP/SMTP.
31493
31494 There are a number of applications (for example, there is one called &'ssmtp'&)
31495 that do this job. However, people have found them to be lacking in various
31496 ways. For instance, you might want to allow aliasing and forwarding to be done
31497 before sending a message to the smart host.
31498
31499 Exim already had the necessary infrastructure for doing this job. Just a few
31500 tweaks were needed to make it behave as required, though it is somewhat of an
31501 overkill to use a fully-featured MTA for this purpose.
31502
31503 .oindex "&%mua_wrapper%&"
31504 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
31505 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
31506 assumes that it is being used to &"wrap"& a command-line MUA in the manner
31507 just described. As well as setting &%mua_wrapper%&, you also need to provide a
31508 compatible router and transport configuration. Typically there will be just one
31509 router and one transport, sending everything to a smart host.
31510
31511 When run in MUA wrapping mode, the behaviour of Exim changes in the
31512 following ways:
31513
31514 .ilist
31515 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
31516 In other words, the only way to submit messages is via the command line.
31517 .next
31518 Each message is synchronously delivered as soon as it is received (&%-odi%& is
31519 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
31520 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
31521 does not finish until the delivery attempt is complete. If the delivery is
31522 successful, a zero return code is given.
31523 .next
31524 Address redirection is permitted, but the final routing for all addresses must
31525 be to the same remote transport, and to the same list of hosts. Furthermore,
31526 the return address (envelope sender) must be the same for all recipients, as
31527 must any added or deleted header lines. In other words, it must be possible to
31528 deliver the message in a single SMTP transaction, however many recipients there
31529 are.
31530 .next
31531 If these conditions are not met, or if routing any address results in a
31532 failure or defer status, or if Exim is unable to deliver all the recipients
31533 successfully to one of the smart hosts, delivery of the entire message fails.
31534 .next
31535 Because no queueing is allowed, all failures are treated as permanent; there
31536 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
31537 smart host. Furthermore, because only a single yes/no response can be given to
31538 the caller, it is not possible to deliver to some recipients and not others. If
31539 there is an error (temporary or permanent) for any recipient, all are failed.
31540 .next
31541 If more than one smart host is listed, Exim will try another host after a
31542 connection failure or a timeout, in the normal way. However, if this kind of
31543 failure happens for all the hosts, the delivery fails.
31544 .next
31545 When delivery fails, an error message is written to the standard error stream
31546 (as well as to Exim's log), and Exim exits to the caller with a return code
31547 value 1. The message is expunged from Exim's spool files. No bounce messages
31548 are ever generated.
31549 .next
31550 No retry data is maintained, and any retry rules are ignored.
31551 .next
31552 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
31553 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
31554 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
31555 .endlist
31556
31557 The overall effect is that Exim makes a single synchronous attempt to deliver
31558 the message, failing if there is any kind of problem. Because no local
31559 deliveries are done and no daemon can be run, Exim does not need root
31560 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
31561 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
31562 the advantages and disadvantages of running without root privilege.
31563
31564
31565
31566
31567 . ////////////////////////////////////////////////////////////////////////////
31568 . ////////////////////////////////////////////////////////////////////////////
31569
31570 .chapter "Log files" "CHAPlog"
31571 .scindex IIDloggen "log" "general description"
31572 .cindex "log" "types of"
31573 Exim writes three different logs, referred to as the main log, the reject log,
31574 and the panic log:
31575
31576 .ilist
31577 .cindex "main log"
31578 The main log records the arrival of each message and each delivery in a single
31579 line in each case. The format is as compact as possible, in an attempt to keep
31580 down the size of log files. Two-character flag sequences make it easy to pick
31581 out these lines. A number of other events are recorded in the main log. Some of
31582 them are optional, in which case the &%log_selector%& option controls whether
31583 they are included or not. A Perl script called &'eximstats'&, which does simple
31584 analysis of main log files, is provided in the Exim distribution (see section
31585 &<<SECTmailstat>>&).
31586 .next
31587 .cindex "reject log"
31588 The reject log records information from messages that are rejected as a result
31589 of a configuration option (that is, for policy reasons).
31590 The first line of each rejection is a copy of the line that is also written to
31591 the main log. Then, if the message's header has been read at the time the log
31592 is written, its contents are written to this log. Only the original header
31593 lines are available; header lines added by ACLs are not logged. You can use the
31594 reject log to check that your policy controls are working correctly; on a busy
31595 host this may be easier than scanning the main log for rejection messages. You
31596 can suppress the writing of the reject log by setting &%write_rejectlog%&
31597 false.
31598 .next
31599 .cindex "panic log"
31600 .cindex "system log"
31601 When certain serious errors occur, Exim writes entries to its panic log. If the
31602 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
31603 are usually written to the main log as well, but can get lost amid the mass of
31604 other entries. The panic log should be empty under normal circumstances. It is
31605 therefore a good idea to check it (or to have a &'cron'& script check it)
31606 regularly, in order to become aware of any problems. When Exim cannot open its
31607 panic log, it tries as a last resort to write to the system log (syslog). This
31608 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
31609 message itself is written at priority LOG_CRIT.
31610 .endlist
31611
31612 Every log line starts with a timestamp, in the format shown in the following
31613 example. Note that many of the examples shown in this chapter are line-wrapped.
31614 In the log file, this would be all on one line:
31615 .code
31616 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
31617 by QUIT
31618 .endd
31619 By default, the timestamps are in the local timezone. There are two
31620 ways of changing this:
31621
31622 .ilist
31623 You can set the &%timezone%& option to a different time zone; in particular, if
31624 you set
31625 .code
31626 timezone = UTC
31627 .endd
31628 the timestamps will be in UTC (aka GMT).
31629 .next
31630 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
31631 example:
31632 .code
31633 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
31634 .endd
31635 .endlist
31636
31637 .cindex "log" "process ids in"
31638 .cindex "pid (process id)" "in log lines"
31639 Exim does not include its process id in log lines by default, but you can
31640 request that it does so by specifying the &`pid`& log selector (see section
31641 &<<SECTlogselector>>&). When this is set, the process id is output, in square
31642 brackets, immediately after the time and date.
31643
31644
31645
31646
31647 .section "Where the logs are written" "SECTwhelogwri"
31648 .cindex "log" "destination"
31649 .cindex "log" "to file"
31650 .cindex "log" "to syslog"
31651 .cindex "syslog"
31652 The logs may be written to local files, or to syslog, or both. However, it
31653 should be noted that many syslog implementations use UDP as a transport, and
31654 are therefore unreliable in the sense that messages are not guaranteed to
31655 arrive at the loghost, nor is the ordering of messages necessarily maintained.
31656 It has also been reported that on large log files (tens of megabytes) you may
31657 need to tweak syslog to prevent it syncing the file with each write &-- on
31658 Linux this has been seen to make syslog take 90% plus of CPU time.
31659
31660 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
31661 &_Local/Makefile_& or by setting &%log_file_path%& in the run time
31662 configuration. This latter string is expanded, so it can contain, for example,
31663 references to the host name:
31664 .code
31665 log_file_path = /var/log/$primary_hostname/exim_%slog
31666 .endd
31667 It is generally advisable, however, to set the string in &_Local/Makefile_&
31668 rather than at run time, because then the setting is available right from the
31669 start of Exim's execution. Otherwise, if there's something it wants to log
31670 before it has read the configuration file (for example, an error in the
31671 configuration file) it will not use the path you want, and may not be able to
31672 log at all.
31673
31674 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
31675 list, currently limited to at most two items. This is one option where the
31676 facility for changing a list separator may not be used. The list must always be
31677 colon-separated. If an item in the list is &"syslog"& then syslog is used;
31678 otherwise the item must either be an absolute path, containing &`%s`& at the
31679 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
31680 implying the use of a default path.
31681
31682 When Exim encounters an empty item in the list, it searches the list defined by
31683 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
31684 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
31685 mean &"use the path specified at build time"&. It no such item exists, log
31686 files are written in the &_log_& subdirectory of the spool directory. This is
31687 equivalent to the setting:
31688 .code
31689 log_file_path = $spool_directory/log/%slog
31690 .endd
31691 If you do not specify anything at build time or run time, that is where the
31692 logs are written.
31693
31694 A log file path may also contain &`%D`& if datestamped log file names are in
31695 use &-- see section &<<SECTdatlogfil>>& below.
31696
31697 Here are some examples of possible settings:
31698 .display
31699 &`LOG_FILE_PATH=syslog `& syslog only
31700 &`LOG_FILE_PATH=:syslog `& syslog and default path
31701 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
31702 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
31703 .endd
31704 If there are more than two paths in the list, the first is used and a panic
31705 error is logged.
31706
31707
31708
31709 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
31710 .cindex "log" "cycling local files"
31711 .cindex "cycling logs"
31712 .cindex "&'exicyclog'&"
31713 .cindex "log" "local files; writing to"
31714 Some operating systems provide centralized and standardized methods for cycling
31715 log files. For those that do not, a utility script called &'exicyclog'& is
31716 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
31717 main and reject logs each time it is called. The maximum number of old logs to
31718 keep can be set. It is suggested this script is run as a daily &'cron'& job.
31719
31720 An Exim delivery process opens the main log when it first needs to write to it,
31721 and it keeps the file open in case subsequent entries are required &-- for
31722 example, if a number of different deliveries are being done for the same
31723 message. However, remote SMTP deliveries can take a long time, and this means
31724 that the file may be kept open long after it is renamed if &'exicyclog'& or
31725 something similar is being used to rename log files on a regular basis. To
31726 ensure that a switch of log files is noticed as soon as possible, Exim calls
31727 &[stat()]& on the main log's name before reusing an open file, and if the file
31728 does not exist, or its inode has changed, the old file is closed and Exim
31729 tries to open the main log from scratch. Thus, an old log file may remain open
31730 for quite some time, but no Exim processes should write to it once it has been
31731 renamed.
31732
31733
31734
31735 .section "Datestamped log files" "SECTdatlogfil"
31736 .cindex "log" "datestamped files"
31737 Instead of cycling the main and reject log files by renaming them
31738 periodically, some sites like to use files whose names contain a datestamp,
31739 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_&.
31740 Exim has support for this way of working. It is enabled by setting the
31741 &%log_file_path%& option to a path that includes &`%D`& at the point where the
31742 datestamp is required. For example:
31743 .code
31744 log_file_path = /var/spool/exim/log/%slog-%D
31745 log_file_path = /var/log/exim-%s-%D.log
31746 log_file_path = /var/spool/exim/log/%D-%slog
31747 .endd
31748 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
31749 examples of names generated by the above examples:
31750 .code
31751 /var/spool/exim/log/mainlog-20021225
31752 /var/log/exim-reject-20021225.log
31753 /var/spool/exim/log/20021225-mainlog
31754 .endd
31755 When this form of log file is specified, Exim automatically switches to new
31756 files at midnight. It does not make any attempt to compress old logs; you
31757 will need to write your own script if you require this. You should not
31758 run &'exicyclog'& with this form of logging.
31759
31760 The location of the panic log is also determined by &%log_file_path%&, but it
31761 is not datestamped, because rotation of the panic log does not make sense.
31762 When generating the name of the panic log, &`%D`& is removed from the string.
31763 In addition, if it immediately follows a slash, a following non-alphanumeric
31764 character is removed; otherwise a preceding non-alphanumeric character is
31765 removed. Thus, the three examples above would give these panic log names:
31766 .code
31767 /var/spool/exim/log/paniclog
31768 /var/log/exim-panic.log
31769 /var/spool/exim/log/paniclog
31770 .endd
31771
31772
31773 .section "Logging to syslog" "SECID249"
31774 .cindex "log" "syslog; writing to"
31775 The use of syslog does not change what Exim logs or the format of its messages,
31776 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
31777 Exim's log lines are omitted when these lines are sent to syslog. Apart from
31778 that, the same strings are written to syslog as to log files. The syslog
31779 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
31780 by default, but you can change these by setting the &%syslog_facility%& and
31781 &%syslog_processname%& options, respectively. If Exim was compiled with
31782 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
31783 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
31784 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
31785 the time and host name to each line.
31786 The three log streams are mapped onto syslog priorities as follows:
31787
31788 .ilist
31789 &'mainlog'& is mapped to LOG_INFO
31790 .next
31791 &'rejectlog'& is mapped to LOG_NOTICE
31792 .next
31793 &'paniclog'& is mapped to LOG_ALERT
31794 .endlist
31795
31796 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
31797 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
31798 these are routed by syslog to the same place. You can suppress this duplication
31799 by setting &%syslog_duplication%& false.
31800
31801 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
31802 entries contain multiple lines when headers are included. To cope with both
31803 these cases, entries written to syslog are split into separate &[syslog()]&
31804 calls at each internal newline, and also after a maximum of
31805 870 data characters. (This allows for a total syslog line length of 1024, when
31806 additions such as timestamps are added.) If you are running a syslog
31807 replacement that can handle lines longer than the 1024 characters allowed by
31808 RFC 3164, you should set
31809 .code
31810 SYSLOG_LONG_LINES=yes
31811 .endd
31812 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
31813 lines, but it still splits at internal newlines in &'reject'& log entries.
31814
31815 To make it easy to re-assemble split lines later, each component of a split
31816 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
31817 where <&'n'&> is the component number and <&'m'&> is the total number of
31818 components in the entry. The / delimiter is used when the line was split
31819 because it was too long; if it was split because of an internal newline, the \
31820 delimiter is used. For example, supposing the length limit to be 50 instead of
31821 870, the following would be the result of a typical rejection message to
31822 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
31823 name, and pid as added by syslog:
31824 .code
31825 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
31826 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
31827 [3/5] when scanning for sender: missing or malformed lo
31828 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
31829 [5/5] mple>)
31830 .endd
31831 The same error might cause the following lines to be written to &"rejectlog"&
31832 (LOG_NOTICE):
31833 .code
31834 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
31835 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
31836 [3/18] er when scanning for sender: missing or malformed
31837 [4/18] local part in "<>" (envelope sender is <ph10@cam
31838 [5\18] .example>)
31839 [6\18] Recipients: ph10@some.domain.cam.example
31840 [7\18] P Received: from [127.0.0.1] (ident=ph10)
31841 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
31842 [9\18] id 16RdAL-0006pc-00
31843 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
31844 [11\18] 09:43 +0100
31845 [12\18] F From: <>
31846 [13\18] Subject: this is a test header
31847 [18\18] X-something: this is another header
31848 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
31849 [16\18] le>
31850 [17\18] B Bcc:
31851 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
31852 .endd
31853 Log lines that are neither too long nor contain newlines are written to syslog
31854 without modification.
31855
31856 If only syslog is being used, the Exim monitor is unable to provide a log tail
31857 display, unless syslog is routing &'mainlog'& to a file on the local host and
31858 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
31859 where it is.
31860
31861
31862
31863 .section "Log line flags" "SECID250"
31864 One line is written to the main log for each message received, and for each
31865 successful, unsuccessful, and delayed delivery. These lines can readily be
31866 picked out by the distinctive two-character flags that immediately follow the
31867 timestamp. The flags are:
31868 .display
31869 &`<=`& message arrival
31870 &`=>`& normal message delivery
31871 &`->`& additional address in same delivery
31872 &`*>`& delivery suppressed by &%-N%&
31873 &`**`& delivery failed; address bounced
31874 &`==`& delivery deferred; temporary problem
31875 .endd
31876
31877
31878 .section "Logging message reception" "SECID251"
31879 .cindex "log" "reception line"
31880 The format of the single-line entry in the main log that is written for every
31881 message received is shown in the basic example below, which is split over
31882 several lines in order to fit it on the page:
31883 .code
31884 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
31885 H=mailer.fict.example [192.168.123.123] U=exim
31886 P=smtp S=5678 id=<incoming message id>
31887 .endd
31888 The address immediately following &"<="& is the envelope sender address. A
31889 bounce message is shown with the sender address &"<>"&, and if it is locally
31890 generated, this is followed by an item of the form
31891 .code
31892 R=<message id>
31893 .endd
31894 which is a reference to the message that caused the bounce to be sent.
31895
31896 .cindex "HELO"
31897 .cindex "EHLO"
31898 For messages from other hosts, the H and U fields identify the remote host and
31899 record the RFC 1413 identity of the user that sent the message, if one was
31900 received. The number given in square brackets is the IP address of the sending
31901 host. If there is a single, unparenthesized host name in the H field, as
31902 above, it has been verified to correspond to the IP address (see the
31903 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
31904 by the remote host in the SMTP HELO or EHLO command, and has not been
31905 verified. If verification yields a different name to that given for HELO or
31906 EHLO, the verified name appears first, followed by the HELO or EHLO
31907 name in parentheses.
31908
31909 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
31910 without brackets, in the HELO or EHLO command, leading to entries in
31911 the log containing text like these examples:
31912 .code
31913 H=(10.21.32.43) [192.168.8.34]
31914 H=([10.21.32.43]) [192.168.8.34]
31915 .endd
31916 This can be confusing. Only the final address in square brackets can be relied
31917 on.
31918
31919 For locally generated messages (that is, messages not received over TCP/IP),
31920 the H field is omitted, and the U field contains the login name of the caller
31921 of Exim.
31922
31923 .cindex "authentication" "logging"
31924 .cindex "AUTH" "logging"
31925 For all messages, the P field specifies the protocol used to receive the
31926 message. This is the value that is stored in &$received_protocol$&. In the case
31927 of incoming SMTP messages, the value indicates whether or not any SMTP
31928 extensions (ESMTP), encryption, or authentication were used. If the SMTP
31929 session was encrypted, there is an additional X field that records the cipher
31930 suite that was used.
31931
31932 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
31933 hosts that have authenticated themselves using the SMTP AUTH command. The first
31934 value is used when the SMTP connection was encrypted (&"secure"&). In this case
31935 there is an additional item A= followed by the name of the authenticator that
31936 was used. If an authenticated identification was set up by the authenticator's
31937 &%server_set_id%& option, this is logged too, separated by a colon from the
31938 authenticator name.
31939
31940 .cindex "size" "of message"
31941 The id field records the existing message id, if present. The size of the
31942 received message is given by the S field. When the message is delivered,
31943 headers may be removed or added, so that the size of delivered copies of the
31944 message may not correspond with this value (and indeed may be different to each
31945 other).
31946
31947 The &%log_selector%& option can be used to request the logging of additional
31948 data when a message is received. See section &<<SECTlogselector>>& below.
31949
31950
31951
31952 .section "Logging deliveries" "SECID252"
31953 .cindex "log" "delivery line"
31954 The format of the single-line entry in the main log that is written for every
31955 delivery is shown in one of the examples below, for local and remote
31956 deliveries, respectively. Each example has been split into two lines in order
31957 to fit it on the page:
31958 .code
31959 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
31960 <marv@hitch.fict.example> R=localuser T=local_delivery
31961 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
31962 monk@holistic.fict.example R=dnslookup T=remote_smtp
31963 H=holistic.fict.example [192.168.234.234]
31964 .endd
31965 For ordinary local deliveries, the original address is given in angle brackets
31966 after the final delivery address, which might be a pipe or a file. If
31967 intermediate address(es) exist between the original and the final address, the
31968 last of these is given in parentheses after the final address. The R and T
31969 fields record the router and transport that were used to process the address.
31970
31971 If a shadow transport was run after a successful local delivery, the log line
31972 for the successful delivery has an item added on the end, of the form
31973 .display
31974 &`ST=<`&&'shadow transport name'&&`>`&
31975 .endd
31976 If the shadow transport did not succeed, the error message is put in
31977 parentheses afterwards.
31978
31979 .cindex "asterisk" "after IP address"
31980 When more than one address is included in a single delivery (for example, two
31981 SMTP RCPT commands in one transaction) the second and subsequent addresses are
31982 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
31983 down a single SMTP connection, an asterisk follows the IP address in the log
31984 lines for the second and subsequent messages.
31985
31986 The generation of a reply message by a filter file gets logged as a
31987 &"delivery"& to the addressee, preceded by &">"&.
31988
31989 The &%log_selector%& option can be used to request the logging of additional
31990 data when a message is delivered. See section &<<SECTlogselector>>& below.
31991
31992
31993 .section "Discarded deliveries" "SECID253"
31994 .cindex "discarded messages"
31995 .cindex "message" "discarded"
31996 .cindex "delivery" "discarded; logging"
31997 When a message is discarded as a result of the command &"seen finish"& being
31998 obeyed in a filter file which generates no deliveries, a log entry of the form
31999 .code
32000 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
32001 <low.club@bridge.example> R=userforward
32002 .endd
32003 is written, to record why no deliveries are logged. When a message is discarded
32004 because it is aliased to &":blackhole:"& the log line is like this:
32005 .code
32006 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
32007 <hole@nowhere.example> R=blackhole_router
32008 .endd
32009
32010
32011 .section "Deferred deliveries" "SECID254"
32012 When a delivery is deferred, a line of the following form is logged:
32013 .code
32014 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
32015 R=dnslookup T=smtp defer (146): Connection refused
32016 .endd
32017 In the case of remote deliveries, the error is the one that was given for the
32018 last IP address that was tried. Details of individual SMTP failures are also
32019 written to the log, so the above line would be preceded by something like
32020 .code
32021 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
32022 mail1.endrest.example [192.168.239.239]: Connection refused
32023 .endd
32024 When a deferred address is skipped because its retry time has not been reached,
32025 a message is written to the log, but this can be suppressed by setting an
32026 appropriate value in &%log_selector%&.
32027
32028
32029
32030 .section "Delivery failures" "SECID255"
32031 .cindex "delivery" "failure; logging"
32032 If a delivery fails because an address cannot be routed, a line of the
32033 following form is logged:
32034 .code
32035 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
32036 <jim@trek99.example>: unknown mail domain
32037 .endd
32038 If a delivery fails at transport time, the router and transport are shown, and
32039 the response from the remote host is included, as in this example:
32040 .code
32041 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
32042 R=dnslookup T=remote_smtp: SMTP error from remote mailer
32043 after pipelined RCPT TO:<ace400@pb.example>: host
32044 pbmail3.py.example [192.168.63.111]: 553 5.3.0
32045 <ace400@pb.example>...Addressee unknown
32046 .endd
32047 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
32048 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
32049 disabling PIPELINING. The log lines for all forms of delivery failure are
32050 flagged with &`**`&.
32051
32052
32053
32054 .section "Fake deliveries" "SECID256"
32055 .cindex "delivery" "fake; logging"
32056 If a delivery does not actually take place because the &%-N%& option has been
32057 used to suppress it, a normal delivery line is written to the log, except that
32058 &"=>"& is replaced by &"*>"&.
32059
32060
32061
32062 .section "Completion" "SECID257"
32063 A line of the form
32064 .code
32065 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
32066 .endd
32067 is written to the main log when a message is about to be removed from the spool
32068 at the end of its processing.
32069
32070
32071
32072
32073 .section "Summary of Fields in Log Lines" "SECID258"
32074 .cindex "log" "summary of fields"
32075 A summary of the field identifiers that are used in log lines is shown in
32076 the following table:
32077 .display
32078 &`A `& authenticator name (and optional id)
32079 &`C `& SMTP confirmation on delivery
32080 &` `& command list for &"no mail in SMTP session"&
32081 &`CV `& certificate verification status
32082 &`D `& duration of &"no mail in SMTP session"&
32083 &`DN `& distinguished name from peer certificate
32084 &`DT `& on &`=>`& lines: time taken for a delivery
32085 &`F `& sender address (on delivery lines)
32086 &`H `& host name and IP address
32087 &`I `& local interface used
32088 &`id `& message id for incoming message
32089 &`P `& on &`<=`& lines: protocol used
32090 &` `& on &`=>`& and &`**`& lines: return path
32091 &`QT `& on &`=>`& lines: time spent on queue so far
32092 &` `& on &"Completed"& lines: time spent on queue
32093 &`R `& on &`<=`& lines: reference for local bounce
32094 &` `& on &`=>`& &`**`& and &`==`& lines: router name
32095 &`S `& size of message
32096 &`ST `& shadow transport name
32097 &`T `& on &`<=`& lines: message subject (topic)
32098 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
32099 &`U `& local user or RFC 1413 identity
32100 &`X `& TLS cipher suite
32101 .endd
32102
32103
32104 .section "Other log entries" "SECID259"
32105 Various other types of log entry are written from time to time. Most should be
32106 self-explanatory. Among the more common are:
32107
32108 .ilist
32109 .cindex "retry" "time not reached"
32110 &'retry time not reached'&&~&~An address previously suffered a temporary error
32111 during routing or local delivery, and the time to retry has not yet arrived.
32112 This message is not written to an individual message log file unless it happens
32113 during the first delivery attempt.
32114 .next
32115 &'retry time not reached for any host'&&~&~An address previously suffered
32116 temporary errors during remote delivery, and the retry time has not yet arrived
32117 for any of the hosts to which it is routed.
32118 .next
32119 .cindex "spool directory" "file locked"
32120 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
32121 some other Exim process is already working on the message. This can be quite
32122 common if queue running processes are started at frequent intervals. The
32123 &'exiwhat'& utility script can be used to find out what Exim processes are
32124 doing.
32125 .next
32126 .cindex "error" "ignored"
32127 &'error ignored'&&~&~There are several circumstances that give rise to this
32128 message:
32129 .olist
32130 Exim failed to deliver a bounce message whose age was greater than
32131 &%ignore_bounce_errors_after%&. The bounce was discarded.
32132 .next
32133 A filter file set up a delivery using the &"noerror"& option, and the delivery
32134 failed. The delivery was discarded.
32135 .next
32136 A delivery set up by a router configured with
32137 . ==== As this is a nested list, any displays it contains must be indented
32138 . ==== as otherwise they are too far to the left.
32139 .code
32140 errors_to = <>
32141 .endd
32142 failed. The delivery was discarded.
32143 .endlist olist
32144 .endlist ilist
32145
32146
32147
32148
32149
32150 .section "Reducing or increasing what is logged" "SECTlogselector"
32151 .cindex "log" "selectors"
32152 By setting the &%log_selector%& global option, you can disable some of Exim's
32153 default logging, or you can request additional logging. The value of
32154 &%log_selector%& is made up of names preceded by plus or minus characters. For
32155 example:
32156 .code
32157 log_selector = +arguments -retry_defer
32158 .endd
32159 The list of optional log items is in the following table, with the default
32160 selection marked by asterisks:
32161 .display
32162 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
32163 &` address_rewrite `& address rewriting
32164 &` all_parents `& all parents in => lines
32165 &` arguments `& command line arguments
32166 &`*connection_reject `& connection rejections
32167 &`*delay_delivery `& immediate delivery delayed
32168 &` deliver_time `& time taken to perform delivery
32169 &` delivery_size `& add &`S=`&&'nnn'& to => lines
32170 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
32171 &`*etrn `& ETRN commands
32172 &`*host_lookup_failed `& as it says
32173 &` ident_timeout `& timeout for ident connection
32174 &` incoming_interface `& incoming interface on <= lines
32175 &` incoming_port `& incoming port on <= lines
32176 &`*lost_incoming_connection `& as it says (includes timeouts)
32177 &` outgoing_port `& add remote port to => lines
32178 &`*queue_run `& start and end queue runs
32179 &` queue_time `& time on queue for one recipient
32180 &` queue_time_overall `& time on queue for whole message
32181 &` pid `& Exim process id
32182 &` received_recipients `& recipients on <= lines
32183 &` received_sender `& sender on <= lines
32184 &`*rejected_header `& header contents on reject log
32185 &`*retry_defer `& &"retry time not reached"&
32186 &` return_path_on_delivery `& put return path on => and ** lines
32187 &` sender_on_delivery `& add sender to => lines
32188 &`*sender_verify_fail `& sender verification failures
32189 &`*size_reject `& rejection because too big
32190 &`*skip_delivery `& delivery skipped in a queue run
32191 &` smtp_confirmation `& SMTP confirmation on => lines
32192 &` smtp_connection `& SMTP connections
32193 &` smtp_incomplete_transaction`& incomplete SMTP transactions
32194 &` smtp_no_mail `& session with no MAIL commands
32195 &` smtp_protocol_error `& SMTP protocol errors
32196 &` smtp_syntax_error `& SMTP syntax errors
32197 &` subject `& contents of &'Subject:'& on <= lines
32198 &` tls_certificate_verified `& certificate verification status
32199 &`*tls_cipher `& TLS cipher suite on <= and => lines
32200 &` tls_peerdn `& TLS peer DN on <= and => lines
32201 &` unknown_in_list `& DNS lookup failed in list match
32202
32203 &` all `& all of the above
32204 .endd
32205 More details on each of these items follows:
32206
32207 .ilist
32208 .cindex "&%warn%& ACL verb" "log when skipping"
32209 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
32210 its conditions cannot be evaluated, a log line to this effect is written if
32211 this log selector is set.
32212 .next
32213 .cindex "log" "rewriting"
32214 .cindex "rewriting" "logging"
32215 &%address_rewrite%&: This applies both to global rewrites and per-transport
32216 rewrites, but not to rewrites in filters run as an unprivileged user (because
32217 such users cannot access the log).
32218 .next
32219 .cindex "log" "full parentage"
32220 &%all_parents%&: Normally only the original and final addresses are logged on
32221 delivery lines; with this selector, intermediate parents are given in
32222 parentheses between them.
32223 .next
32224 .cindex "log" "Exim arguments"
32225 .cindex "Exim arguments, logging"
32226 &%arguments%&: This causes Exim to write the arguments with which it was called
32227 to the main log, preceded by the current working directory. This is a debugging
32228 feature, added to make it easier to find out how certain MUAs call
32229 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
32230 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
32231 that are empty or that contain white space are quoted. Non-printing characters
32232 are shown as escape sequences. This facility cannot log unrecognized arguments,
32233 because the arguments are checked before the configuration file is read. The
32234 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
32235 between the caller and Exim.
32236 .next
32237 .cindex "log" "connection rejections"
32238 &%connection_reject%&: A log entry is written whenever an incoming SMTP
32239 connection is rejected, for whatever reason.
32240 .next
32241 .cindex "log" "delayed delivery"
32242 .cindex "delayed delivery, logging"
32243 &%delay_delivery%&: A log entry is written whenever a delivery process is not
32244 started for an incoming message because the load is too high or too many
32245 messages were received on one connection. Logging does not occur if no delivery
32246 process is started because &%queue_only%& is set or &%-odq%& was used.
32247 .next
32248 .cindex "log" "delivery duration"
32249 &%deliver_time%&: For each delivery, the amount of real time it has taken to
32250 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
32251 .next
32252 .cindex "log" "message size on delivery"
32253 .cindex "size" "of message"
32254 &%delivery_size%&: For each delivery, the size of message delivered is added to
32255 the &"=>"& line, tagged with S=.
32256 .next
32257 .cindex "log" "dnslist defer"
32258 .cindex "DNS list" "logging defer"
32259 .cindex "black list (DNS)"
32260 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
32261 DNS black list suffers a temporary error.
32262 .next
32263 .cindex "log" "ETRN commands"
32264 .cindex "ETRN" "logging"
32265 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
32266 is run to determine whether or not it is actually accepted. An invalid ETRN
32267 command, or one received within a message transaction is not logged by this
32268 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
32269 .next
32270 .cindex "log" "host lookup failure"
32271 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
32272 any addresses, or when a lookup of an IP address fails to find a host name, a
32273 log line is written. This logging does not apply to direct DNS lookups when
32274 routing email addresses, but it does apply to &"byname"& lookups.
32275 .next
32276 .cindex "log" "ident timeout"
32277 .cindex "RFC 1413" "logging timeout"
32278 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
32279 client's ident port times out.
32280 .next
32281 .cindex "log" "incoming interface"
32282 .cindex "interface" "logging"
32283 &%incoming_interface%&: The interface on which a message was received is added
32284 to the &"<="& line as an IP address in square brackets, tagged by I= and
32285 followed by a colon and the port number. The local interface and port are also
32286 added to other SMTP log lines, for example &"SMTP connection from"&, and to
32287 rejection lines.
32288 .next
32289 .cindex "log" "incoming remote port"
32290 .cindex "port" "logging remote"
32291 .cindex "TCP/IP" "logging incoming remote port"
32292 .vindex "&$sender_fullhost$&"
32293 .vindex "&$sender_rcvhost$&"
32294 &%incoming_port%&: The remote port number from which a message was received is
32295 added to log entries and &'Received:'& header lines, following the IP address
32296 in square brackets, and separated from it by a colon. This is implemented by
32297 changing the value that is put in the &$sender_fullhost$& and
32298 &$sender_rcvhost$& variables. Recording the remote port number has become more
32299 important with the widening use of NAT (see RFC 2505).
32300 .next
32301 .cindex "log" "dropped connection"
32302 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
32303 connection is unexpectedly dropped.
32304 .next
32305 .cindex "log" "outgoing remote port"
32306 .cindex "port" "logging outgoint remote"
32307 .cindex "TCP/IP" "logging ougtoing remote port"
32308 &%outgoing_port%&: The remote port number is added to delivery log lines (those
32309 containing => tags) following the IP address. This option is not included in
32310 the default setting, because for most ordinary configurations, the remote port
32311 number is always 25 (the SMTP port).
32312 .next
32313 .cindex "log" "process ids in"
32314 .cindex "pid (process id)" "in log lines"
32315 &%pid%&: The current process id is added to every log line, in square brackets,
32316 immediately after the time and date.
32317 .next
32318 .cindex "log" "queue run"
32319 .cindex "queue runner" "logging"
32320 &%queue_run%&: The start and end of every queue run are logged.
32321 .next
32322 .cindex "log" "queue time"
32323 &%queue_time%&: The amount of time the message has been in the queue on the
32324 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
32325 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
32326 includes reception time as well as the delivery time for the current address.
32327 This means that it may be longer than the difference between the arrival and
32328 delivery log line times, because the arrival log line is not written until the
32329 message has been successfully received.
32330 .next
32331 &%queue_time_overall%&: The amount of time the message has been in the queue on
32332 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
32333 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
32334 message, so it includes reception time as well as the total delivery time.
32335 .next
32336 .cindex "log" "recipients"
32337 &%received_recipients%&: The recipients of a message are listed in the main log
32338 as soon as the message is received. The list appears at the end of the log line
32339 that is written when a message is received, preceded by the word &"for"&. The
32340 addresses are listed after they have been qualified, but before any rewriting
32341 has taken place.
32342 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
32343 in the list.
32344 .next
32345 .cindex "log" "sender reception"
32346 &%received_sender%&: The unrewritten original sender of a message is added to
32347 the end of the log line that records the message's arrival, after the word
32348 &"from"& (before the recipients if &%received_recipients%& is also set).
32349 .next
32350 .cindex "log" "header lines for rejection"
32351 &%rejected_header%&: If a message's header has been received at the time a
32352 rejection is written to the reject log, the complete header is added to the
32353 log. Header logging can be turned off individually for messages that are
32354 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
32355 .next
32356 .cindex "log" "retry defer"
32357 &%retry_defer%&: A log line is written if a delivery is deferred because a
32358 retry time has not yet been reached. However, this &"retry time not reached"&
32359 message is always omitted from individual message logs after the first delivery
32360 attempt.
32361 .next
32362 .cindex "log" "return path"
32363 &%return_path_on_delivery%&: The return path that is being transmitted with
32364 the message is included in delivery and bounce lines, using the tag P=.
32365 This is omitted if no delivery actually happens, for example, if routing fails,
32366 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
32367 .next
32368 .cindex "log" "sender on delivery"
32369 &%sender_on_delivery%&: The message's sender address is added to every delivery
32370 and bounce line, tagged by F= (for &"from"&).
32371 This is the original sender that was received with the message; it is not
32372 necessarily the same as the outgoing return path.
32373 .next
32374 .cindex "log" "sender verify failure"
32375 &%sender_verify_fail%&: If this selector is unset, the separate log line that
32376 gives details of a sender verification failure is not written. Log lines for
32377 the rejection of SMTP commands contain just &"sender verify failed"&, so some
32378 detail is lost.
32379 .next
32380 .cindex "log" "size rejection"
32381 &%size_reject%&: A log line is written whenever a message is rejected because
32382 it is too big.
32383 .next
32384 .cindex "log" "frozen messages; skipped"
32385 .cindex "frozen messages" "logging skipping"
32386 &%skip_delivery%&: A log line is written whenever a message is skipped during a
32387 queue run because it is frozen or because another process is already delivering
32388 it.
32389 .cindex "&""spool file is locked""&"
32390 The message that is written is &"spool file is locked"&.
32391 .next
32392 .cindex "log" "smtp confirmation"
32393 .cindex "SMTP" "logging confirmation"
32394 &%smtp_confirmation%&: The response to the final &"."& in the SMTP dialogue for
32395 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
32396 A number of MTAs (including Exim) return an identifying string in this
32397 response.
32398 .next
32399 .cindex "log" "SMTP connections"
32400 .cindex "SMTP" "logging connections"
32401 &%smtp_connection%&: A log line is written whenever an SMTP connection is
32402 established or closed, unless the connection is from a host that matches
32403 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
32404 only when the closure is unexpected.) This applies to connections from local
32405 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
32406 dropped in the middle of a message, a log line is always written, whether or
32407 not this selector is set, but otherwise nothing is written at the start and end
32408 of connections unless this selector is enabled.
32409
32410 For TCP/IP connections to an Exim daemon, the current number of connections is
32411 included in the log message for each new connection, but note that the count is
32412 reset if the daemon is restarted.
32413 Also, because connections are closed (and the closure is logged) in
32414 subprocesses, the count may not include connections that have been closed but
32415 whose termination the daemon has not yet noticed. Thus, while it is possible to
32416 match up the opening and closing of connections in the log, the value of the
32417 logged counts may not be entirely accurate.
32418 .next
32419 .cindex "log" "SMTP transaction; incomplete"
32420 .cindex "SMTP" "logging incomplete transactions"
32421 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
32422 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
32423 and the message sender plus any accepted recipients are included in the log
32424 line. This can provide evidence of dictionary attacks.
32425 .next
32426 .cindex "log" "non-MAIL SMTP sessions"
32427 .cindex "MAIL" "logging session without"
32428 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
32429 connection terminates without having issued a MAIL command. This includes both
32430 the case when the connection is dropped, and the case when QUIT is used. It
32431 does not include cases where the connection is rejected right at the start (by
32432 an ACL, or because there are too many connections, or whatever). These cases
32433 already have their own log lines.
32434
32435 The log line that is written contains the identity of the client in the usual
32436 way, followed by D= and a time, which records the duration of the connection.
32437 If the connection was authenticated, this fact is logged exactly as it is for
32438 an incoming message, with an A= item. If the connection was encrypted, CV=,
32439 DN=, and X= items may appear as they do for an incoming message, controlled by
32440 the same logging options.
32441
32442 Finally, if any SMTP commands were issued during the connection, a C= item
32443 is added to the line, listing the commands that were used. For example,
32444 .code
32445 C=EHLO,QUIT
32446 .endd
32447 shows that the client issued QUIT straight after EHLO. If there were fewer
32448 than 20 commands, they are all listed. If there were more than 20 commands,
32449 the last 20 are listed, preceded by &"..."&. However, with the default
32450 setting of 10 for &%smtp_accep_max_nonmail%&, the connection will in any case
32451 have been aborted before 20 non-mail commands are processed.
32452 .next
32453 .cindex "log" "SMTP protocol error"
32454 .cindex "SMTP" "logging protocol error"
32455 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
32456 encountered. Exim does not have perfect detection of all protocol errors
32457 because of transmission delays and the use of pipelining. If PIPELINING has
32458 been advertised to a client, an Exim server assumes that the client will use
32459 it, and therefore it does not count &"expected"& errors (for example, RCPT
32460 received after rejecting MAIL) as protocol errors.
32461 .next
32462 .cindex "SMTP" "logging syntax errors"
32463 .cindex "SMTP" "syntax errors; logging"
32464 .cindex "SMTP" "unknown command; logging"
32465 .cindex "log" "unknown SMTP command"
32466 .cindex "log" "SMTP syntax error"
32467 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
32468 encountered. An unrecognized command is treated as a syntax error. For an
32469 external connection, the host identity is given; for an internal connection
32470 using &%-bs%& the sender identification (normally the calling user) is given.
32471 .next
32472 .cindex "log" "subject"
32473 .cindex "subject, logging"
32474 &%subject%&: The subject of the message is added to the arrival log line,
32475 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
32476 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
32477 specifies whether characters with values greater than 127 should be logged
32478 unchanged, or whether they should be rendered as escape sequences.
32479 .next
32480 .cindex "log" "certificate verification"
32481 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
32482 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
32483 verified, and &`CV=no`& if not.
32484 .next
32485 .cindex "log" "TLS cipher"
32486 .cindex "TLS" "logging cipher"
32487 &%tls_cipher%&: When a message is sent or received over an encrypted
32488 connection, the cipher suite used is added to the log line, preceded by X=.
32489 .next
32490 .cindex "log" "TLS peer DN"
32491 .cindex "TLS" "logging peer DN"
32492 &%tls_peerdn%&: When a message is sent or received over an encrypted
32493 connection, and a certificate is supplied by the remote host, the peer DN is
32494 added to the log line, preceded by DN=.
32495 .next
32496 .cindex "log" "DNS failure in list"
32497 &%unknown_in_list%&: This setting causes a log entry to be written when the
32498 result of a list match is failure because a DNS lookup failed.
32499 .endlist
32500
32501
32502 .section "Message log" "SECID260"
32503 .cindex "message" "log file for"
32504 .cindex "log" "message log; description of"
32505 .cindex "&_msglog_& directory"
32506 .oindex "&%preserve_message_logs%&"
32507 In addition to the general log files, Exim writes a log file for each message
32508 that it handles. The names of these per-message logs are the message ids, and
32509 they are kept in the &_msglog_& sub-directory of the spool directory. Each
32510 message log contains copies of the log lines that apply to the message. This
32511 makes it easier to inspect the status of an individual message without having
32512 to search the main log. A message log is deleted when processing of the message
32513 is complete, unless &%preserve_message_logs%& is set, but this should be used
32514 only with great care because they can fill up your disk very quickly.
32515
32516 On a heavily loaded system, it may be desirable to disable the use of
32517 per-message logs, in order to reduce disk I/O. This can be done by setting the
32518 &%message_logs%& option false.
32519 .ecindex IIDloggen
32520
32521
32522
32523
32524 . ////////////////////////////////////////////////////////////////////////////
32525 . ////////////////////////////////////////////////////////////////////////////
32526
32527 .chapter "Exim utilities" "CHAPutils"
32528 .scindex IIDutils "utilities"
32529 A number of utility scripts and programs are supplied with Exim and are
32530 described in this chapter. There is also the Exim Monitor, which is covered in
32531 the next chapter. The utilities described here are:
32532
32533 .itable none 0 0 3 7* left 15* left 40* left
32534 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
32535 "list what Exim processes are doing"
32536 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
32537 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
32538 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
32539 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
32540 various criteria"
32541 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
32542 .irow &<<SECTmailstat>>& &'eximstats'& &&&
32543 "extract statistics from the log"
32544 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
32545 "check address acceptance from given IP"
32546 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
32547 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
32548 .irow &<<SECThindatmai>>& &'exim_dumpdb'& "dump a hints database"
32549 .irow &<<SECThindatmai>>& &'exim_tidydb'& "clean up a hints database"
32550 .irow &<<SECThindatmai>>& &'exim_fixdb'& "patch a hints database"
32551 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
32552 .endtable
32553
32554 Another utility that might be of use to sites with many MTAs is Tom Kistner's
32555 &'exilog'&. It provides log visualizations across multiple Exim servers. See
32556 &url(http://duncanthrax.net/exilog/) for details.
32557
32558
32559
32560
32561 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
32562 .cindex "&'exiwhat'&"
32563 .cindex "process, querying"
32564 .cindex "SIGUSR1"
32565 On operating systems that can restart a system call after receiving a signal
32566 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
32567 a line describing what it is doing to the file &_exim-process.info_& in the
32568 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
32569 processes it can find, having first emptied the file. It then waits for one
32570 second to allow the Exim processes to react before displaying the results. In
32571 order to run &'exiwhat'& successfully you have to have sufficient privilege to
32572 send the signal to the Exim processes, so it is normally run as root.
32573
32574 &*Warning*&: This is not an efficient process. It is intended for occasional
32575 use by system administrators. It is not sensible, for example, to set up a
32576 script that sends SIGUSR1 signals to Exim processes at short intervals.
32577
32578
32579 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
32580 varies in different operating systems. Not only are different options used,
32581 but the format of the output is different. For this reason, there are some
32582 system configuration options that configure exactly how &'exiwhat'& works. If
32583 it doesn't seem to be working for you, check the following compile-time
32584 options:
32585 .display
32586 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
32587 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
32588 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
32589 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
32590 .endd
32591 An example of typical output from &'exiwhat'& is
32592 .code
32593 164 daemon: -q1h, listening on port 25
32594 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
32595 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
32596 [10.19.42.42] (editor@ref.example)
32597 10592 handling incoming call from [192.168.243.242]
32598 10628 accepting a local non-SMTP message
32599 .endd
32600 The first number in the output line is the process number. The third line has
32601 been split here, in order to fit it on the page.
32602
32603
32604
32605 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
32606 .cindex "&'exiqgrep'&"
32607 .cindex "queue" "grepping"
32608 This utility is a Perl script contributed by Matt Hubbard. It runs
32609 .code
32610 exim -bpu
32611 .endd
32612 to obtain a queue listing with undelivered recipients only, and then greps the
32613 output to select messages that match given criteria. The following selection
32614 options are available:
32615
32616 .vlist
32617 .vitem &*-f*&&~<&'regex'&>
32618 Match the sender address. The field that is tested is enclosed in angle
32619 brackets, so you can test for bounce messages with
32620 .code
32621 exiqgrep -f '^<>$'
32622 .endd
32623 .vitem &*-r*&&~<&'regex'&>
32624 Match a recipient address. The field that is tested is not enclosed in angle
32625 brackets.
32626
32627 .vitem &*-s*&&~<&'regex'&>
32628 Match against the size field.
32629
32630 .vitem &*-y*&&~<&'seconds'&>
32631 Match messages that are younger than the given time.
32632
32633 .vitem &*-o*&&~<&'seconds'&>
32634 Match messages that are older than the given time.
32635
32636 .vitem &*-z*&
32637 Match only frozen messages.
32638
32639 .vitem &*-x*&
32640 Match only non-frozen messages.
32641 .endlist
32642
32643 The following options control the format of the output:
32644
32645 .vlist
32646 .vitem &*-c*&
32647 Display only the count of matching messages.
32648
32649 .vitem &*-l*&
32650 Long format &-- display the full message information as output by Exim. This is
32651 the default.
32652
32653 .vitem &*-i*&
32654 Display message ids only.
32655
32656 .vitem &*-b*&
32657 Brief format &-- one line per message.
32658
32659 .vitem &*-R*&
32660 Display messages in reverse order.
32661 .endlist
32662
32663 There is one more option, &%-h%&, which outputs a list of options.
32664
32665
32666
32667 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
32668 .cindex "&'exiqsumm'&"
32669 .cindex "queue" "summary"
32670 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
32671 -bp`& and produces a summary of the messages on the queue. Thus, you use it by
32672 running a command such as
32673 .code
32674 exim -bp | exiqsumm
32675 .endd
32676 The output consists of one line for each domain that has messages waiting for
32677 it, as in the following example:
32678 .code
32679 3 2322 74m 66m msn.com.example
32680 .endd
32681 Each line lists the number of pending deliveries for a domain, their total
32682 volume, and the length of time that the oldest and the newest messages have
32683 been waiting. Note that the number of pending deliveries is greater than the
32684 number of messages when messages have more than one recipient.
32685
32686 A summary line is output at the end. By default the output is sorted on the
32687 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
32688 the output to be sorted by oldest message and by count of messages,
32689 respectively. There are also three options that split the messages for each
32690 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
32691 separates frozen messages, and &%-s%& separates messages according to their
32692 sender.
32693
32694 The output of &'exim -bp'& contains the original addresses in the message, so
32695 this also applies to the output from &'exiqsumm'&. No domains from addresses
32696 generated by aliasing or forwarding are included (unless the &%one_time%&
32697 option of the &(redirect)& router has been used to convert them into &"top
32698 level"& addresses).
32699
32700
32701
32702
32703 .section "Extracting specific information from the log (exigrep)" &&&
32704 "SECTextspeinf"
32705 .cindex "&'exigrep'&"
32706 .cindex "log" "extracts; grepping for"
32707 The &'exigrep'& utility is a Perl script that searches one or more main log
32708 files for entries that match a given pattern. When it finds a match, it
32709 extracts all the log entries for the relevant message, not just those that
32710 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
32711 given message, or all mail for a given user, or for a given host, for example.
32712 The input files can be in Exim log format or syslog format.
32713 If a matching log line is not associated with a specific message, it is
32714 included in &'exigrep'&'s output without any additional lines. The usage is:
32715 .display
32716 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
32717 .endd
32718 If no log file names are given on the command line, the standard input is read.
32719
32720 The &%-t%& argument specifies a number of seconds. It adds an additional
32721 condition for message selection. Messages that are complete are shown only if
32722 they spent more than <&'n'&> seconds on the queue.
32723
32724 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
32725 makes it case-sensitive. This may give a performance improvement when searching
32726 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
32727 option; with &%-I%& they do not. In both cases it is possible to change the
32728 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
32729
32730 The &%-l%& option means &"literal"&, that is, treat all characters in the
32731 pattern as standing for themselves. Otherwise the pattern must be a Perl
32732 regular expression.
32733
32734 The &%-v%& option inverts the matching condition. That is, a line is selected
32735 if it does &'not'& match the pattern.
32736
32737 If the location of a &'zcat'& command is known from the definition of
32738 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
32739 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
32740
32741
32742 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
32743 .cindex "&'exipick'&"
32744 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
32745 lists messages from the queue according to a variety of criteria. For details
32746 of &'exipick'&'s facilities, visit the web page at
32747 &url(http://www.exim.org/eximwiki/ToolExipickManPage) or run &'exipick'& with
32748 the &%--help%& option.
32749
32750
32751 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
32752 .cindex "log" "cycling local files"
32753 .cindex "cycling logs"
32754 .cindex "&'exicyclog'&"
32755 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
32756 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
32757 you are using log files with datestamps in their names (see section
32758 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
32759 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
32760 There are two command line options for &'exicyclog'&:
32761 .ilist
32762 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
32763 default that is set when Exim is built. The default default is 10.
32764 .next
32765 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
32766 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
32767 overriding the script's default, which is to find the setting from Exim's
32768 configuration.
32769 .endlist
32770
32771 Each time &'exicyclog'& is run the file names get &"shuffled down"& by one. If
32772 the main log file name is &_mainlog_& (the default) then when &'exicyclog'& is
32773 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
32774 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
32775 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
32776 logs are handled similarly.
32777
32778 If the limit is greater than 99, the script uses 3-digit numbers such as
32779 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
32780 to one that is greater, or &'vice versa'&, you will have to fix the names of
32781 any existing log files.
32782
32783 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
32784 the end are deleted. All files with numbers greater than 01 are compressed,
32785 using a compression command which is configured by the COMPRESS_COMMAND
32786 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
32787 root &%crontab%& entry of the form
32788 .code
32789 1 0 * * * su exim -c /usr/exim/bin/exicyclog
32790 .endd
32791 assuming you have used the name &"exim"& for the Exim user. You can run
32792 &'exicyclog'& as root if you wish, but there is no need.
32793
32794
32795
32796 .section "Mail statistics (eximstats)" "SECTmailstat"
32797 .cindex "statistics"
32798 .cindex "&'eximstats'&"
32799 A Perl script called &'eximstats'& is provided for extracting statistical
32800 information from log files. The output is either plain text, or HTML.
32801 Exim log files are also supported by the &'Lire'& system produced by the
32802 LogReport Foundation &url(http://www.logreport.org).
32803
32804 The &'eximstats'& script has been hacked about quite a bit over time. The
32805 latest version is the result of some extensive revision by Steve Campbell. A
32806 lot of information is given by default, but there are options for suppressing
32807 various parts of it. Following any options, the arguments to the script are a
32808 list of files, which should be main log files. For example:
32809 .code
32810 eximstats -nr /var/spool/exim/log/mainlog.01
32811 .endd
32812 By default, &'eximstats'& extracts information about the number and volume of
32813 messages received from or delivered to various hosts. The information is sorted
32814 both by message count and by volume, and the top fifty hosts in each category
32815 are listed on the standard output. Similar information, based on email
32816 addresses or domains instead of hosts can be requested by means of various
32817 options. For messages delivered and received locally, similar statistics are
32818 also produced per user.
32819
32820 The output also includes total counts and statistics about delivery errors, and
32821 histograms showing the number of messages received and deliveries made in each
32822 hour of the day. A delivery with more than one address in its envelope (for
32823 example, an SMTP transaction with more than one RCPT command) is counted
32824 as a single delivery by &'eximstats'&.
32825
32826 Though normally more deliveries than receipts are reported (as messages may
32827 have multiple recipients), it is possible for &'eximstats'& to report more
32828 messages received than delivered, even though the queue is empty at the start
32829 and end of the period in question. If an incoming message contains no valid
32830 recipients, no deliveries are recorded for it. A bounce message is handled as
32831 an entirely separate message.
32832
32833 &'eximstats'& always outputs a grand total summary giving the volume and number
32834 of messages received and deliveries made, and the number of hosts involved in
32835 each case. It also outputs the number of messages that were delayed (that is,
32836 not completely delivered at the first attempt), and the number that had at
32837 least one address that failed.
32838
32839 The remainder of the output is in sections that can be independently disabled
32840 or modified by various options. It consists of a summary of deliveries by
32841 transport, histograms of messages received and delivered per time interval
32842 (default per hour), information about the time messages spent on the queue,
32843 a list of relayed messages, lists of the top fifty sending hosts, local
32844 senders, destination hosts, and destination local users by count and by volume,
32845 and a list of delivery errors that occurred.
32846
32847 The relay information lists messages that were actually relayed, that is, they
32848 came from a remote host and were directly delivered to some other remote host,
32849 without being processed (for example, for aliasing or forwarding) locally.
32850
32851 There are quite a few options for &'eximstats'& to control exactly what it
32852 outputs. These are documented in the Perl script itself, and can be extracted
32853 by running the command &(perldoc)& on the script. For example:
32854 .code
32855 perldoc /usr/exim/bin/eximstats
32856 .endd
32857
32858 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
32859 .cindex "&'exim_checkaccess'&"
32860 .cindex "policy control" "checking access"
32861 .cindex "checking access"
32862 The &%-bh%& command line argument allows you to run a fake SMTP session with
32863 debugging output, in order to check what Exim is doing when it is applying
32864 policy controls to incoming SMTP mail. However, not everybody is sufficiently
32865 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
32866 sometimes you just want to answer the question &"Does this address have
32867 access?"& without bothering with any further details.
32868
32869 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
32870 two arguments, an IP address and an email address:
32871 .code
32872 exim_checkaccess 10.9.8.7 A.User@a.domain.example
32873 .endd
32874 The utility runs a call to Exim with the &%-bh%& option, to test whether the
32875 given email address would be accepted in a RCPT command in a TCP/IP
32876 connection from the host with the given IP address. The output of the utility
32877 is either the word &"accepted"&, or the SMTP error response, for example:
32878 .code
32879 Rejected:
32880 550 Relay not permitted
32881 .endd
32882 When running this test, the utility uses &`<>`& as the envelope sender address
32883 for the MAIL command, but you can change this by providing additional
32884 options. These are passed directly to the Exim command. For example, to specify
32885 that the test is to be run with the sender address &'himself@there.example'&
32886 you can use:
32887 .code
32888 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
32889 -f himself@there.example
32890 .endd
32891 Note that these additional Exim command line items must be given after the two
32892 mandatory arguments.
32893
32894 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
32895 while running its checks. You can run checks that include callouts by using
32896 &%-bhc%&, but this is not yet available in a &"packaged"& form.
32897
32898
32899
32900 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
32901 .cindex "DBM" "building dbm files"
32902 .cindex "building DBM files"
32903 .cindex "&'exim_dbmbuild'&"
32904 .cindex "lower casing"
32905 .cindex "binary zero" "in lookup key"
32906 The &'exim_dbmbuild'& program reads an input file containing keys and data in
32907 the format used by the &(lsearch)& lookup (see section
32908 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
32909 names as keys and the remainder of the information as data. The lower-casing
32910 can be prevented by calling the program with the &%-nolc%& option.
32911
32912 A terminating zero is included as part of the key string. This is expected by
32913 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
32914 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
32915 strings or the data strings. The &(dbmnz)& lookup type can be used with such
32916 files.
32917
32918 The program requires two arguments: the name of the input file (which can be a
32919 single hyphen to indicate the standard input), and the name of the output file.
32920 It creates the output under a temporary name, and then renames it if all went
32921 well.
32922
32923 .cindex "USE_DB"
32924 If the native DB interface is in use (USE_DB is set in a compile-time
32925 configuration file &-- this is common in free versions of Unix) the two file
32926 names must be different, because in this mode the Berkeley DB functions create
32927 a single output file using exactly the name given. For example,
32928 .code
32929 exim_dbmbuild /etc/aliases /etc/aliases.db
32930 .endd
32931 reads the system alias file and creates a DBM version of it in
32932 &_/etc/aliases.db_&.
32933
32934 In systems that use the &'ndbm'& routines (mostly proprietary versions of
32935 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
32936 environment, the suffixes are added to the second argument of
32937 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
32938 when the Berkeley functions are used in compatibility mode (though this is not
32939 recommended), because in that case it adds a &_.db_& suffix to the file name.
32940
32941 If a duplicate key is encountered, the program outputs a warning, and when it
32942 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
32943 option is used. By default, only the first of a set of duplicates is used &--
32944 this makes it compatible with &(lsearch)& lookups. There is an option
32945 &%-lastdup%& which causes it to use the data for the last duplicate instead.
32946 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
32947 &%stderr%&. For other errors, where it doesn't actually make a new file, the
32948 return code is 2.
32949
32950
32951
32952
32953 .section "Finding individual retry times (exinext)" "SECTfinindret"
32954 .cindex "retry" "times"
32955 .cindex "&'exinext'&"
32956 A utility called &'exinext'& (mostly a Perl script) provides the ability to
32957 fish specific information out of the retry database. Given a mail domain (or a
32958 complete address), it looks up the hosts for that domain, and outputs any retry
32959 information for the hosts or for the domain. At present, the retry information
32960 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
32961 output. For example:
32962 .code
32963 $ exinext piglet@milne.fict.example
32964 kanga.milne.example:192.168.8.1 error 146: Connection refused
32965 first failed: 21-Feb-1996 14:57:34
32966 last tried: 21-Feb-1996 14:57:34
32967 next try at: 21-Feb-1996 15:02:34
32968 roo.milne.example:192.168.8.3 error 146: Connection refused
32969 first failed: 20-Jan-1996 13:12:08
32970 last tried: 21-Feb-1996 11:42:03
32971 next try at: 21-Feb-1996 19:42:03
32972 past final cutoff time
32973 .endd
32974 You can also give &'exinext'& a local part, without a domain, and it
32975 will give any retry information for that local part in your default domain.
32976 A message id can be used to obtain retry information pertaining to a specific
32977 message. This exists only when an attempt to deliver a message to a remote host
32978 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
32979 &'exinext'& is not particularly efficient, but then it is not expected to be
32980 run very often.
32981
32982 The &'exinext'& utility calls Exim to find out information such as the location
32983 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
32984 passed on to the &'exim'& commands. The first specifies an alternate Exim
32985 configuration file, and the second sets macros for use within the configuration
32986 file. These features are mainly to help in testing, but might also be useful in
32987 environments where more than one configuration file is in use.
32988
32989
32990
32991 .section "Hints database maintenance" "SECThindatmai"
32992 .cindex "hints database" "maintenance"
32993 .cindex "maintaining Exim's hints database"
32994 Three utility programs are provided for maintaining the DBM files that Exim
32995 uses to contain its delivery hint information. Each program requires two
32996 arguments. The first specifies the name of Exim's spool directory, and the
32997 second is the name of the database it is to operate on. These are as follows:
32998
32999 .ilist
33000 &'retry'&: the database of retry information
33001 .next
33002 &'wait-'&<&'transport name'&>: databases of information about messages waiting
33003 for remote hosts
33004 .next
33005 &'callout'&: the callout cache
33006 .next
33007 &'ratelimit'&: the data for implementing the ratelimit ACL condition
33008 .next
33009 &'misc'&: other hints data
33010 .endlist
33011
33012 The &'misc'& database is used for
33013
33014 .ilist
33015 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
33016 .next
33017 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
33018 &(smtp)& transport)
33019 .endlist
33020
33021
33022
33023 .section "exim_dumpdb" "SECID261"
33024 .cindex "&'exim_dumpdb'&"
33025 The entire contents of a database are written to the standard output by the
33026 &'exim_dumpdb'& program, which has no options or arguments other than the
33027 spool and database names. For example, to dump the retry database:
33028 .code
33029 exim_dumpdb /var/spool/exim retry
33030 .endd
33031 Two lines of output are produced for each entry:
33032 .code
33033 T:mail.ref.example:192.168.242.242 146 77 Connection refused
33034 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
33035 .endd
33036 The first item on the first line is the key of the record. It starts with one
33037 of the letters R, or T, depending on whether it refers to a routing or
33038 transport retry. For a local delivery, the next part is the local address; for
33039 a remote delivery it is the name of the remote host, followed by its failing IP
33040 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
33041 transport). If the remote port is not the standard one (port 25), it is added
33042 to the IP address. Then there follows an error code, an additional error code,
33043 and a textual description of the error.
33044
33045 The three times on the second line are the time of first failure, the time of
33046 the last delivery attempt, and the computed time for the next attempt. The line
33047 ends with an asterisk if the cutoff time for the last retry rule has been
33048 exceeded.
33049
33050 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
33051 consists of a host name followed by a list of ids for messages that are or were
33052 waiting to be delivered to that host. If there are a very large number for any
33053 one host, continuation records, with a sequence number added to the host name,
33054 may be seen. The data in these records is often out of date, because a message
33055 may be routed to several alternative hosts, and Exim makes no effort to keep
33056 cross-references.
33057
33058
33059
33060 .section "exim_tidydb" "SECID262"
33061 .cindex "&'exim_tidydb'&"
33062 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
33063 database. If run with no options, it removes all records that are more than 30
33064 days old. The age is calculated from the date and time that the record was last
33065 updated. Note that, in the case of the retry database, it is &'not'& the time
33066 since the first delivery failure. Information about a host that has been down
33067 for more than 30 days will remain in the database, provided that the record is
33068 updated sufficiently often.
33069
33070 The cutoff date can be altered by means of the &%-t%& option, which must be
33071 followed by a time. For example, to remove all records older than a week from
33072 the retry database:
33073 .code
33074 exim_tidydb -t 7d /var/spool/exim retry
33075 .endd
33076 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
33077 message ids. In the former these appear as data in records keyed by host &--
33078 they were messages that were waiting for that host &-- and in the latter they
33079 are the keys for retry information for messages that have suffered certain
33080 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
33081 message ids in database records are those of messages that are still on the
33082 queue. Message ids for messages that no longer exist are removed from
33083 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
33084 For the &'retry'& database, records whose keys are non-existent message ids are
33085 removed. The &'exim_tidydb'& utility outputs comments on the standard output
33086 whenever it removes information from the database.
33087
33088 Certain records are automatically removed by Exim when they are no longer
33089 needed, but others are not. For example, if all the MX hosts for a domain are
33090 down, a retry record is created for each one. If the primary MX host comes back
33091 first, its record is removed when Exim successfully delivers to it, but the
33092 records for the others remain because Exim has not tried to use those hosts.
33093
33094 It is important, therefore, to run &'exim_tidydb'& periodically on all the
33095 hints databases. You should do this at a quiet time of day, because it requires
33096 a database to be locked (and therefore inaccessible to Exim) while it does its
33097 work. Removing records from a DBM file does not normally make the file smaller,
33098 but all the common DBM libraries are able to re-use the space that is released.
33099 After an initial phase of increasing in size, the databases normally reach a
33100 point at which they no longer get any bigger, as long as they are regularly
33101 tidied.
33102
33103 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
33104 databases is likely to keep on increasing.
33105
33106
33107
33108
33109 .section "exim_fixdb" "SECID263"
33110 .cindex "&'exim_fixdb'&"
33111 The &'exim_fixdb'& program is a utility for interactively modifying databases.
33112 Its main use is for testing Exim, but it might also be occasionally useful for
33113 getting round problems in a live system. It has no options, and its interface
33114 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
33115 key of a database record can then be entered, and the data for that record is
33116 displayed.
33117
33118 If &"d"& is typed at the next prompt, the entire record is deleted. For all
33119 except the &'retry'& database, that is the only operation that can be carried
33120 out. For the &'retry'& database, each field is output preceded by a number, and
33121 data for individual fields can be changed by typing the field number followed
33122 by new data, for example:
33123 .code
33124 > 4 951102:1000
33125 .endd
33126 resets the time of the next delivery attempt. Time values are given as a
33127 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
33128 used as optional separators.
33129
33130
33131
33132
33133 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
33134 .cindex "mailbox" "maintenance"
33135 .cindex "&'exim_lock'&"
33136 .cindex "locking mailboxes"
33137 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
33138 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
33139 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
33140 a user agent while investigating a problem. The utility requires the name of
33141 the file as its first argument. If the locking is successful, the second
33142 argument is run as a command (using C's &[system()]& function); if there is no
33143 second argument, the value of the SHELL environment variable is used; if this
33144 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
33145 is unlocked and the utility ends. The following options are available:
33146
33147 .vlist
33148 .vitem &%-fcntl%&
33149 Use &[fcntl()]& locking on the open mailbox.
33150
33151 .vitem &%-flock%&
33152 Use &[flock()]& locking on the open mailbox, provided the operating system
33153 supports it.
33154
33155 .vitem &%-interval%&
33156 This must be followed by a number, which is a number of seconds; it sets the
33157 interval to sleep between retries (default 3).
33158
33159 .vitem &%-lockfile%&
33160 Create a lock file before opening the mailbox.
33161
33162 .vitem &%-mbx%&
33163 Lock the mailbox using MBX rules.
33164
33165 .vitem &%-q%&
33166 Suppress verification output.
33167
33168 .vitem &%-retries%&
33169 This must be followed by a number; it sets the number of times to try to get
33170 the lock (default 10).
33171
33172 .vitem &%-restore_time%&
33173 This option causes &%exim_lock%& to restore the modified and read times to the
33174 locked file before exiting. This allows you to access a locked mailbox (for
33175 example, to take a backup copy) without disturbing the times that the user
33176 subsequently sees.
33177
33178 .vitem &%-timeout%&
33179 This must be followed by a number, which is a number of seconds; it sets a
33180 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
33181 default), a non-blocking call is used.
33182
33183 .vitem &%-v%&
33184 Generate verbose output.
33185 .endlist
33186
33187 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
33188 default is to create a lock file and also to use &[fcntl()]& locking on the
33189 mailbox, which is the same as Exim's default. The use of &%-flock%& or
33190 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
33191 requires that the directory containing the file be writeable. Locking by lock
33192 file does not last for ever; Exim assumes that a lock file is expired if it is
33193 more than 30 minutes old.
33194
33195 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
33196 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
33197 to be taken out on the open mailbox, and an exclusive lock on the file
33198 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
33199 number of the mailbox file. When the locking is released, if an exclusive lock
33200 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
33201
33202 The default output contains verification of the locking that takes place. The
33203 &%-v%& option causes some additional information to be given. The &%-q%& option
33204 suppresses all output except error messages.
33205
33206 A command such as
33207 .code
33208 exim_lock /var/spool/mail/spqr
33209 .endd
33210 runs an interactive shell while the file is locked, whereas
33211 .display
33212 &`exim_lock -q /var/spool/mail/spqr <<End`&
33213 <&'some commands'&>
33214 &`End`&
33215 .endd
33216 runs a specific non-interactive sequence of commands while the file is locked,
33217 suppressing all verification output. A single command can be run by a command
33218 such as
33219 .code
33220 exim_lock -q /var/spool/mail/spqr \
33221 "cp /var/spool/mail/spqr /some/where"
33222 .endd
33223 Note that if a command is supplied, it must be entirely contained within the
33224 second argument &-- hence the quotes.
33225 .ecindex IIDutils
33226
33227
33228 . ////////////////////////////////////////////////////////////////////////////
33229 . ////////////////////////////////////////////////////////////////////////////
33230
33231 .chapter "The Exim monitor" "CHAPeximon"
33232 .scindex IIDeximon "Exim monitor" "description"
33233 .cindex "X-windows"
33234 .cindex "&'eximon'&"
33235 .cindex "Local/eximon.conf"
33236 .cindex "&_exim_monitor/EDITME_&"
33237 The Exim monitor is an application which displays in an X window information
33238 about the state of Exim's queue and what Exim is doing. An admin user can
33239 perform certain operations on messages from this GUI interface; however all
33240 such facilities are also available from the command line, and indeed, the
33241 monitor itself makes use of the command line to perform any actions requested.
33242
33243
33244
33245 .section "Running the monitor" "SECID264"
33246 The monitor is started by running the script called &'eximon'&. This is a shell
33247 script that sets up a number of environment variables, and then runs the
33248 binary called &_eximon.bin_&. The default appearance of the monitor window can
33249 be changed by editing the &_Local/eximon.conf_& file created by editing
33250 &_exim_monitor/EDITME_&. Comments in that file describe what the various
33251 parameters are for.
33252
33253 The parameters that get built into the &'eximon'& script can be overridden for
33254 a particular invocation by setting up environment variables of the same names,
33255 preceded by &`EXIMON_`&. For example, a shell command such as
33256 .code
33257 EXIMON_LOG_DEPTH=400 eximon
33258 .endd
33259 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
33260 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
33261 overrides the Exim log file configuration. This makes it possible to have
33262 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
33263 syslog messages are routed to a file on the local host.
33264
33265 X resources can be used to change the appearance of the window in the normal
33266 way. For example, a resource setting of the form
33267 .code
33268 Eximon*background: gray94
33269 .endd
33270 changes the colour of the background to light grey rather than white. The
33271 stripcharts are drawn with both the data lines and the reference lines in
33272 black. This means that the reference lines are not visible when on top of the
33273 data. However, their colour can be changed by setting a resource called
33274 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
33275 For example, if your X server is running Unix, you could set up lighter
33276 reference lines in the stripcharts by obeying
33277 .code
33278 xrdb -merge <<End
33279 Eximon*highlight: gray
33280 End
33281 .endd
33282 .cindex "admin user"
33283 In order to see the contents of messages on the queue, and to operate on them,
33284 &'eximon'& must either be run as root or by an admin user.
33285
33286 The monitor's window is divided into three parts. The first contains one or
33287 more stripcharts and two action buttons, the second contains a &"tail"& of the
33288 main log file, and the third is a display of the queue of messages awaiting
33289 delivery, with two more action buttons. The following sections describe these
33290 different parts of the display.
33291
33292
33293
33294
33295 .section "The stripcharts" "SECID265"
33296 .cindex "stripchart"
33297 The first stripchart is always a count of messages on the queue. Its name can
33298 be configured by setting QUEUE_STRIPCHART_NAME in the
33299 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
33300 configuration script by regular expression matches on log file entries, making
33301 it possible to display, for example, counts of messages delivered to certain
33302 hosts or using certain transports. The supplied defaults display counts of
33303 received and delivered messages, and of local and SMTP deliveries. The default
33304 period between stripchart updates is one minute; this can be adjusted by a
33305 parameter in the &_Local/eximon.conf_& file.
33306
33307 The stripchart displays rescale themselves automatically as the value they are
33308 displaying changes. There are always 10 horizontal lines in each chart; the
33309 title string indicates the value of each division when it is greater than one.
33310 For example, &"x2"& means that each division represents a value of 2.
33311
33312 It is also possible to have a stripchart which shows the percentage fullness of
33313 a particular disk partition, which is useful when local deliveries are confined
33314 to a single partition.
33315
33316 .cindex "&%statvfs%& function"
33317 This relies on the availability of the &[statvfs()]& function or equivalent in
33318 the operating system. Most, but not all versions of Unix that support Exim have
33319 this. For this particular stripchart, the top of the chart always represents
33320 100%, and the scale is given as &"x10%"&. This chart is configured by setting
33321 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
33322 &_Local/eximon.conf_& file.
33323
33324
33325
33326
33327 .section "Main action buttons" "SECID266"
33328 .cindex "size" "of monitor window"
33329 .cindex "Exim monitor" "window size"
33330 .cindex "window size"
33331 Below the stripcharts there is an action button for quitting the monitor. Next
33332 to this is another button marked &"Size"&. They are placed here so that
33333 shrinking the window to its default minimum size leaves just the queue count
33334 stripchart and these two buttons visible. Pressing the &"Size"& button causes
33335 the window to expand to its maximum size, unless it is already at the maximum,
33336 in which case it is reduced to its minimum.
33337
33338 When expanding to the maximum, if the window cannot be fully seen where it
33339 currently is, it is moved back to where it was the last time it was at full
33340 size. When it is expanding from its minimum size, the old position is
33341 remembered, and next time it is reduced to the minimum it is moved back there.
33342
33343 The idea is that you can keep a reduced window just showing one or two
33344 stripcharts at a convenient place on your screen, easily expand it to show
33345 the full window when required, and just as easily put it back to what it was.
33346 The idea is copied from what the &'twm'& window manager does for its
33347 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
33348 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
33349
33350 Normally, the monitor starts up with the window at its full size, but it can be
33351 built so that it starts up with the window at its smallest size, by setting
33352 START_SMALL=yes in &_Local/eximon.conf_&.
33353
33354
33355
33356 .section "The log display" "SECID267"
33357 .cindex "log" "tail of; in monitor"
33358 The second section of the window is an area in which a display of the tail of
33359 the main log is maintained.
33360 To save space on the screen, the timestamp on each log line is shortened by
33361 removing the date and, if &%log_timezone%& is set, the timezone.
33362 The log tail is not available when the only destination for logging data is
33363 syslog, unless the syslog lines are routed to a local file whose name is passed
33364 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
33365
33366 The log sub-window has a scroll bar at its lefthand side which can be used to
33367 move back to look at earlier text, and the up and down arrow keys also have a
33368 scrolling effect. The amount of log that is kept depends on the setting of
33369 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
33370 to use. When this is full, the earlier 50% of data is discarded &-- this is
33371 much more efficient than throwing it away line by line. The sub-window also has
33372 a horizontal scroll bar for accessing the ends of long log lines. This is the
33373 only means of horizontal scrolling; the right and left arrow keys are not
33374 available. Text can be cut from this part of the window using the mouse in the
33375 normal way. The size of this subwindow is controlled by parameters in the
33376 configuration file &_Local/eximon.conf_&.
33377
33378 Searches of the text in the log window can be carried out by means of the ^R
33379 and ^S keystrokes, which default to a reverse and a forward search,
33380 respectively. The search covers only the text that is displayed in the window.
33381 It cannot go further back up the log.
33382
33383 The point from which the search starts is indicated by a caret marker. This is
33384 normally at the end of the text in the window, but can be positioned explicitly
33385 by pointing and clicking with the left mouse button, and is moved automatically
33386 by a successful search. If new text arrives in the window when it is scrolled
33387 back, the caret remains where it is, but if the window is not scrolled back,
33388 the caret is moved to the end of the new text.
33389
33390 Pressing ^R or ^S pops up a window into which the search text can be typed.
33391 There are buttons for selecting forward or reverse searching, for carrying out
33392 the search, and for cancelling. If the &"Search"& button is pressed, the search
33393 happens and the window remains so that further searches can be done. If the
33394 &"Return"& key is pressed, a single search is done and the window is closed. If
33395 ^C is typed the search is cancelled.
33396
33397 The searching facility is implemented using the facilities of the Athena text
33398 widget. By default this pops up a window containing both &"search"& and
33399 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
33400 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
33401 However, the linkers in BSDI and HP-UX seem unable to handle an externally
33402 provided version of &%TextPop%& when the remaining parts of the text widget
33403 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
33404 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
33405 on these systems, at the expense of having unwanted items in the search popup
33406 window.
33407
33408
33409
33410 .section "The queue display" "SECID268"
33411 .cindex "queue" "display in monitor"
33412 The bottom section of the monitor window contains a list of all messages that
33413 are on the queue, which includes those currently being received or delivered,
33414 as well as those awaiting delivery. The size of this subwindow is controlled by
33415 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
33416 at which it is updated is controlled by another parameter in the same file &--
33417 the default is 5 minutes, since queue scans can be quite expensive. However,
33418 there is an &"Update"& action button just above the display which can be used
33419 to force an update of the queue display at any time.
33420
33421 When a host is down for some time, a lot of pending mail can build up for it,
33422 and this can make it hard to deal with other messages on the queue. To help
33423 with this situation there is a button next to &"Update"& called &"Hide"&. If
33424 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
33425 type anything in here and press &"Return"&, the text is added to a chain of
33426 such texts, and if every undelivered address in a message matches at least one
33427 of the texts, the message is not displayed.
33428
33429 If there is an address that does not match any of the texts, all the addresses
33430 are displayed as normal. The matching happens on the ends of addresses so, for
33431 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
33432 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
33433 has been set up, a button called &"Unhide"& is displayed. If pressed, it
33434 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
33435 a hide request is automatically cancelled after one hour.
33436
33437 While the dialogue box is displayed, you can't press any buttons or do anything
33438 else to the monitor window. For this reason, if you want to cut text from the
33439 queue display to use in the dialogue box, you have to do the cutting before
33440 pressing the &"Hide"& button.
33441
33442 The queue display contains, for each unhidden queued message, the length of
33443 time it has been on the queue, the size of the message, the message id, the
33444 message sender, and the first undelivered recipient, all on one line. If it is
33445 a bounce message, the sender is shown as &"<>"&. If there is more than one
33446 recipient to which the message has not yet been delivered, subsequent ones are
33447 listed on additional lines, up to a maximum configured number, following which
33448 an ellipsis is displayed. Recipients that have already received the message are
33449 not shown.
33450
33451 .cindex "frozen messages" "display"
33452 If a message is frozen, an asterisk is displayed at the left-hand side.
33453
33454 The queue display has a vertical scroll bar, and can also be scrolled by means
33455 of the arrow keys. Text can be cut from it using the mouse in the normal way.
33456 The text searching facilities, as described above for the log window, are also
33457 available, but the caret is always moved to the end of the text when the queue
33458 display is updated.
33459
33460
33461
33462 .section "The queue menu" "SECID269"
33463 .cindex "queue" "menu in monitor"
33464 If the &%shift%& key is held down and the left button is clicked when the mouse
33465 pointer is over the text for any message, an action menu pops up, and the first
33466 line of the queue display for the message is highlighted. This does not affect
33467 any selected text.
33468
33469 If you want to use some other event for popping up the menu, you can set the
33470 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
33471 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
33472 value set in this parameter is a standard X event description. For example, to
33473 run eximon using &%ctrl%& rather than &%shift%& you could use
33474 .code
33475 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
33476 .endd
33477 The title of the menu is the message id, and it contains entries which act as
33478 follows:
33479
33480 .ilist
33481 &'message log'&: The contents of the message log for the message are displayed
33482 in a new text window.
33483 .next
33484 &'headers'&: Information from the spool file that contains the envelope
33485 information and headers is displayed in a new text window. See chapter
33486 &<<CHAPspool>>& for a description of the format of spool files.
33487 .next
33488 &'body'&: The contents of the spool file containing the body of the message are
33489 displayed in a new text window. There is a default limit of 20,000 bytes to the
33490 amount of data displayed. This can be changed by setting the BODY_MAX
33491 option at compile time, or the EXIMON_BODY_MAX option at run time.
33492 .next
33493 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
33494 delivery of the message. This causes an automatic thaw if the message is
33495 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
33496 a new text window. The delivery is run in a separate process, to avoid holding
33497 up the monitor while the delivery proceeds.
33498 .next
33499 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
33500 that the message be frozen.
33501 .next
33502 .cindex "thawing messages"
33503 .cindex "unfreezing messages"
33504 .cindex "frozen messages" "thawing"
33505 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
33506 that the message be thawed.
33507 .next
33508 .cindex "delivery" "forcing failure"
33509 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
33510 that Exim gives up trying to deliver the message. A bounce message is generated
33511 for any remaining undelivered addresses.
33512 .next
33513 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
33514 that the message be deleted from the system without generating a bounce
33515 message.
33516 .next
33517 &'add recipient'&: A dialog box is displayed into which a recipient address can
33518 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
33519 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
33520 Otherwise it must be entered as a fully qualified address. Pressing RETURN
33521 causes a call to Exim to be made using the &%-Mar%& option to request that an
33522 additional recipient be added to the message, unless the entry box is empty, in
33523 which case no action is taken.
33524 .next
33525 &'mark delivered'&: A dialog box is displayed into which a recipient address
33526 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
33527 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
33528 Otherwise it must be entered as a fully qualified address. Pressing RETURN
33529 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
33530 recipient address as already delivered, unless the entry box is empty, in which
33531 case no action is taken.
33532 .next
33533 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
33534 mark all recipient addresses as already delivered.
33535 .next
33536 &'edit sender'&: A dialog box is displayed initialized with the current
33537 sender's address. Pressing RETURN causes a call to Exim to be made using the
33538 &%-Mes%& option to replace the sender address, unless the entry box is empty,
33539 in which case no action is taken. If you want to set an empty sender (as in
33540 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
33541 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
33542 the address is qualified with that domain.
33543 .endlist
33544
33545 When a delivery is forced, a window showing the &%-v%& output is displayed. In
33546 other cases when a call to Exim is made, if there is any output from Exim (in
33547 particular, if the command fails) a window containing the command and the
33548 output is displayed. Otherwise, the results of the action are normally apparent
33549 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
33550 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
33551 if no output is generated.
33552
33553 The queue display is automatically updated for actions such as freezing and
33554 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
33555 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
33556 force an update of the display after one of these actions.
33557
33558 In any text window that is displayed as result of a menu action, the normal
33559 cut-and-paste facility is available, and searching can be carried out using ^R
33560 and ^S, as described above for the log tail window.
33561 .ecindex IIDeximon
33562
33563
33564
33565
33566
33567 . ////////////////////////////////////////////////////////////////////////////
33568 . ////////////////////////////////////////////////////////////////////////////
33569
33570 .chapter "Security considerations" "CHAPsecurity"
33571 .scindex IIDsecurcon "security" "discussion of"
33572 This chapter discusses a number of issues concerned with security, some of
33573 which are also covered in other parts of this manual.
33574
33575 For reasons that this author does not understand, some people have promoted
33576 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
33577 existence of this chapter in the documentation. However, the intent of the
33578 chapter is simply to describe the way Exim works in relation to certain
33579 security concerns, not to make any specific claims about the effectiveness of
33580 its security as compared with other MTAs.
33581
33582 What follows is a description of the way Exim is supposed to be. Best efforts
33583 have been made to try to ensure that the code agrees with the theory, but an
33584 absence of bugs can never be guaranteed. Any that are reported will get fixed
33585 as soon as possible.
33586
33587
33588 .section "Building a more &""hardened""& Exim" "SECID286"
33589 .cindex "security" "build-time features"
33590 There are a number of build-time options that can be set in &_Local/Makefile_&
33591 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
33592 Exim administrator who does not have the root password, or by someone who has
33593 penetrated the Exim (but not the root) account. These options are as follows:
33594
33595 .ilist
33596 ALT_CONFIG_PREFIX can be set to a string that is required to match the
33597 start of any file names used with the &%-C%& option. When it is set, these file
33598 names are also not allowed to contain the sequence &"/../"&. (However, if the
33599 value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
33600 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
33601 default setting for &%ALT_CONFIG_PREFIX%&.
33602
33603 If the permitted configuration files are confined to a directory to
33604 which only root has access, this guards against someone who has broken
33605 into the Exim account from running a privileged Exim with an arbitrary
33606 configuration file, and using it to break into other accounts.
33607 .next
33608 If ALT_CONFIG_ROOT_ONLY is defined, root privilege is retained for &%-C%&
33609 and &%-D%& only if the caller of Exim is root. Without it, the Exim user may
33610 also use &%-C%& and &%-D%& and retain privilege. Setting this option locks out
33611 the possibility of testing a configuration using &%-C%& right through message
33612 reception and delivery, even if the caller is root. The reception works, but by
33613 that time, Exim is running as the Exim user, so when it re-execs to regain
33614 privilege for the delivery, the use of &%-C%& causes privilege to be lost.
33615 However, root can test reception and delivery using two separate commands.
33616 ALT_CONFIG_ROOT_ONLY is not set by default.
33617 .next
33618 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
33619 is disabled.
33620 .next
33621 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
33622 never to be used for any deliveries. This is like the &%never_users%& runtime
33623 option, but it cannot be overridden; the runtime option adds additional users
33624 to the list. The default setting is &"root"&; this prevents a non-root user who
33625 is permitted to modify the runtime file from using Exim as a way to get root.
33626 .endlist
33627
33628
33629
33630
33631 .section "Root privilege" "SECID270"
33632 .cindex "setuid"
33633 .cindex "root privilege"
33634 The Exim binary is normally setuid to root, which means that it gains root
33635 privilege (runs as root) when it starts execution. In some special cases (for
33636 example, when the daemon is not in use and there are no local deliveries), it
33637 may be possible to run Exim setuid to some user other than root. This is
33638 discussed in the next section. However, in most installations, root privilege
33639 is required for two things:
33640
33641 .ilist
33642 To set up a socket connected to the standard SMTP port (25) when initialising
33643 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
33644 not required.
33645 .next
33646 To be able to change uid and gid in order to read users' &_.forward_& files and
33647 perform local deliveries as the receiving user or as specified in the
33648 configuration.
33649 .endlist
33650
33651 It is not necessary to be root to do any of the other things Exim does, such as
33652 receiving messages and delivering them externally over SMTP, and it is
33653 obviously more secure if Exim does not run as root except when necessary.
33654 For this reason, a user and group for Exim to use must be defined in
33655 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
33656 group"&. Their values can be changed by the run time configuration, though this
33657 is not recommended. Often a user called &'exim'& is used, but some sites use
33658 &'mail'& or another user name altogether.
33659
33660 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
33661 abdication; the process cannot regain root afterwards. Prior to release 4.00,
33662 &[seteuid()]& was used in some circumstances, but this is no longer the case.
33663
33664 After a new Exim process has interpreted its command line options, it changes
33665 uid and gid in the following cases:
33666
33667 .ilist
33668 .oindex "&%-C%&"
33669 .oindex "&%-D%&"
33670 If the &%-C%& option is used to specify an alternate configuration file, or if
33671 the &%-D%& option is used to define macro values for the configuration, and the
33672 calling process is not running as root or the Exim user, the uid and gid are
33673 changed to those of the calling process.
33674 However, if ALT_CONFIG_ROOT_ONLY is defined in &_Local/Makefile_&, only
33675 root callers may use &%-C%& and &%-D%& without losing privilege, and if
33676 DISABLE_D_OPTION is set, the &%-D%& option may not be used at all.
33677 .next
33678 .oindex "&%-be%&"
33679 .oindex "&%-bf%&"
33680 .oindex "&%-bF%&"
33681 If the expansion test option (&%-be%&) or one of the filter testing options
33682 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
33683 calling process.
33684 .next
33685 If the process is not a daemon process or a queue runner process or a delivery
33686 process or a process for testing address routing (started with &%-bt%&), the
33687 uid and gid are changed to the Exim user and group. This means that Exim always
33688 runs under its own uid and gid when receiving messages. This also applies when
33689 testing address verification
33690 .oindex "&%-bv%&"
33691 .oindex "&%-bh%&"
33692 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
33693 option).
33694 .next
33695 For a daemon, queue runner, delivery, or address testing process, the uid
33696 remains as root at this stage, but the gid is changed to the Exim group.
33697 .endlist
33698
33699 The processes that initially retain root privilege behave as follows:
33700
33701 .ilist
33702 A daemon process changes the gid to the Exim group and the uid to the Exim
33703 user after setting up one or more listening sockets. The &[initgroups()]&
33704 function is called, so that if the Exim user is in any additional groups, they
33705 will be used during message reception.
33706 .next
33707 A queue runner process retains root privilege throughout its execution. Its
33708 job is to fork a controlled sequence of delivery processes.
33709 .next
33710 A delivery process retains root privilege throughout most of its execution,
33711 but any actual deliveries (that is, the transports themselves) are run in
33712 subprocesses which always change to a non-root uid and gid. For local
33713 deliveries this is typically the uid and gid of the owner of the mailbox; for
33714 remote deliveries, the Exim uid and gid are used. Once all the delivery
33715 subprocesses have been run, a delivery process changes to the Exim uid and gid
33716 while doing post-delivery tidying up such as updating the retry database and
33717 generating bounce and warning messages.
33718
33719 While the recipient addresses in a message are being routed, the delivery
33720 process runs as root. However, if a user's filter file has to be processed,
33721 this is done in a subprocess that runs under the individual user's uid and
33722 gid. A system filter is run as root unless &%system_filter_user%& is set.
33723 .next
33724 A process that is testing addresses (the &%-bt%& option) runs as root so that
33725 the routing is done in the same environment as a message delivery.
33726 .endlist
33727
33728
33729
33730
33731 .section "Running Exim without privilege" "SECTrunexiwitpri"
33732 .cindex "privilege, running without"
33733 .cindex "unprivileged running"
33734 .cindex "root privilege" "running without"
33735 Some installations like to run Exim in an unprivileged state for more of its
33736 operation, for added security. Support for this mode of operation is provided
33737 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
33738 gid are changed to the Exim user and group at the start of a delivery process
33739 (and also queue runner and address testing processes). This means that address
33740 routing is no longer run as root, and the deliveries themselves cannot change
33741 to any other uid.
33742
33743 .cindex SIGHUP
33744 .cindex "daemon" "restarting"
33745 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
33746 that the daemon can still be started in the usual way, and it can respond
33747 correctly to SIGHUP because the re-invocation regains root privilege.
33748
33749 An alternative approach is to make Exim setuid to the Exim user and also setgid
33750 to the Exim group. If you do this, the daemon must be started from a root
33751 process. (Calling Exim from a root process makes it behave in the way it does
33752 when it is setuid root.) However, the daemon cannot restart itself after a
33753 SIGHUP signal because it cannot regain privilege.
33754
33755 It is still useful to set &%deliver_drop_privilege%& in this case, because it
33756 stops Exim from trying to re-invoke itself to do a delivery after a message has
33757 been received. Such a re-invocation is a waste of resources because it has no
33758 effect.
33759
33760 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
33761 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
33762 to the Exim user seems a clean approach, but there is one complication:
33763
33764 In this style of operation, Exim is running with the real uid and gid set to
33765 those of the calling process, and the effective uid/gid set to Exim's values.
33766 Ideally, any association with the calling process' uid/gid should be dropped,
33767 that is, the real uid/gid should be reset to the effective values so as to
33768 discard any privileges that the caller may have. While some operating systems
33769 have a function that permits this action for a non-root effective uid, quite a
33770 number of them do not. Because of this lack of standardization, Exim does not
33771 address this problem at this time.
33772
33773 For this reason, the recommended approach for &"mostly unprivileged"& running
33774 is to keep the Exim binary setuid to root, and to set
33775 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
33776 be used in the most straightforward way.
33777
33778 If you configure Exim not to run delivery processes as root, there are a
33779 number of restrictions on what you can do:
33780
33781 .ilist
33782 You can deliver only as the Exim user/group. You should explicitly use the
33783 &%user%& and &%group%& options to override routers or local transports that
33784 normally deliver as the recipient. This makes sure that configurations that
33785 work in this mode function the same way in normal mode. Any implicit or
33786 explicit specification of another user causes an error.
33787 .next
33788 Use of &_.forward_& files is severely restricted, such that it is usually
33789 not worthwhile to include them in the configuration.
33790 .next
33791 Users who wish to use &_.forward_& would have to make their home directory and
33792 the file itself accessible to the Exim user. Pipe and append-to-file entries,
33793 and their equivalents in Exim filters, cannot be used. While they could be
33794 enabled in the Exim user's name, that would be insecure and not very useful.
33795 .next
33796 Unless the local user mailboxes are all owned by the Exim user (possible in
33797 some POP3 or IMAP-only environments):
33798
33799 .olist
33800 They must be owned by the Exim group and be writeable by that group. This
33801 implies you must set &%mode%& in the appendfile configuration, as well as the
33802 mode of the mailbox files themselves.
33803 .next
33804 You must set &%no_check_owner%&, since most or all of the files will not be
33805 owned by the Exim user.
33806 .next
33807 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
33808 on a newly created mailbox when unprivileged. This also implies that new
33809 mailboxes need to be created manually.
33810 .endlist olist
33811 .endlist ilist
33812
33813
33814 These restrictions severely restrict what can be done in local deliveries.
33815 However, there are no restrictions on remote deliveries. If you are running a
33816 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
33817 gives more security at essentially no cost.
33818
33819 If you are using the &%mua_wrapper%& facility (see chapter
33820 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
33821
33822
33823
33824
33825 .section "Delivering to local files" "SECID271"
33826 Full details of the checks applied by &(appendfile)& before it writes to a file
33827 are given in chapter &<<CHAPappendfile>>&.
33828
33829
33830
33831 .section "IPv4 source routing" "SECID272"
33832 .cindex "source routing" "in IP packets"
33833 .cindex "IP source routing"
33834 Many operating systems suppress IP source-routed packets in the kernel, but
33835 some cannot be made to do this, so Exim does its own check. It logs incoming
33836 IPv4 source-routed TCP calls, and then drops them. Things are all different in
33837 IPv6. No special checking is currently done.
33838
33839
33840
33841 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
33842 Support for these SMTP commands is disabled by default. If required, they can
33843 be enabled by defining suitable ACLs.
33844
33845
33846
33847
33848 .section "Privileged users" "SECID274"
33849 .cindex "trusted users"
33850 .cindex "admin user"
33851 .cindex "privileged user"
33852 .cindex "user" "trusted"
33853 .cindex "user" "admin"
33854 Exim recognizes two sets of users with special privileges. Trusted users are
33855 able to submit new messages to Exim locally, but supply their own sender
33856 addresses and information about a sending host. For other users submitting
33857 local messages, Exim sets up the sender address from the uid, and doesn't
33858 permit a remote host to be specified.
33859
33860 .oindex "&%-f%&"
33861 However, an untrusted user is permitted to use the &%-f%& command line option
33862 in the special form &%-f <>%& to indicate that a delivery failure for the
33863 message should not cause an error report. This affects the message's envelope,
33864 but it does not affect the &'Sender:'& header. Untrusted users may also be
33865 permitted to use specific forms of address with the &%-f%& option by setting
33866 the &%untrusted_set_sender%& option.
33867
33868 Trusted users are used to run processes that receive mail messages from some
33869 other mail domain and pass them on to Exim for delivery either locally, or over
33870 the Internet. Exim trusts a caller that is running as root, as the Exim user,
33871 as any user listed in the &%trusted_users%& configuration option, or under any
33872 group listed in the &%trusted_groups%& option.
33873
33874 Admin users are permitted to do things to the messages on Exim's queue. They
33875 can freeze or thaw messages, cause them to be returned to their senders, remove
33876 them entirely, or modify them in various ways. In addition, admin users can run
33877 the Exim monitor and see all the information it is capable of providing, which
33878 includes the contents of files on the spool.
33879
33880 .oindex "&%-M%&"
33881 .oindex "&%-q%&"
33882 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
33883 delivery of messages on its queue is restricted to admin users. This
33884 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
33885 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
33886 queue is also restricted to admin users. This restriction can be relaxed by
33887 setting &%no_queue_list_requires_admin%&.
33888
33889 Exim recognizes an admin user if the calling process is running as root or as
33890 the Exim user or if any of the groups associated with the calling process is
33891 the Exim group. It is not necessary actually to be running under the Exim
33892 group. However, if admin users who are not root or the Exim user are to access
33893 the contents of files on the spool via the Exim monitor (which runs
33894 unprivileged), Exim must be built to allow group read access to its spool
33895 files.
33896
33897
33898
33899 .section "Spool files" "SECID275"
33900 .cindex "spool directory" "files"
33901 Exim's spool directory and everything it contains is owned by the Exim user and
33902 set to the Exim group. The mode for spool files is defined in the
33903 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
33904 any user who is a member of the Exim group can access these files.
33905
33906
33907
33908 .section "Use of argv[0]" "SECID276"
33909 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
33910 of specific strings, Exim assumes certain options. For example, calling Exim
33911 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
33912 to calling it with the option &%-bS%&. There are no security implications in
33913 this.
33914
33915
33916
33917 .section "Use of %f formatting" "SECID277"
33918 The only use made of &"%f"& by Exim is in formatting load average values. These
33919 are actually stored in integer variables as 1000 times the load average.
33920 Consequently, their range is limited and so therefore is the length of the
33921 converted output.
33922
33923
33924
33925 .section "Embedded Exim path" "SECID278"
33926 Exim uses its own path name, which is embedded in the code, only when it needs
33927 to re-exec in order to regain root privilege. Therefore, it is not root when it
33928 does so. If some bug allowed the path to get overwritten, it would lead to an
33929 arbitrary program's being run as exim, not as root.
33930
33931
33932
33933 .section "Use of sprintf()" "SECID279"
33934 .cindex "&[sprintf()]&"
33935 A large number of occurrences of &"sprintf"& in the code are actually calls to
33936 &'string_sprintf()'&, a function that returns the result in malloc'd store.
33937 The intermediate formatting is done into a large fixed buffer by a function
33938 that runs through the format string itself, and checks the length of each
33939 conversion before performing it, thus preventing buffer overruns.
33940
33941 The remaining uses of &[sprintf()]& happen in controlled circumstances where
33942 the output buffer is known to be sufficiently long to contain the converted
33943 string.
33944
33945
33946
33947 .section "Use of debug_printf() and log_write()" "SECID280"
33948 Arbitrary strings are passed to both these functions, but they do their
33949 formatting by calling the function &'string_vformat()'&, which runs through
33950 the format string itself, and checks the length of each conversion.
33951
33952
33953
33954 .section "Use of strcat() and strcpy()" "SECID281"
33955 These are used only in cases where the output buffer is known to be large
33956 enough to hold the result.
33957 .ecindex IIDsecurcon
33958
33959
33960
33961
33962 . ////////////////////////////////////////////////////////////////////////////
33963 . ////////////////////////////////////////////////////////////////////////////
33964
33965 .chapter "Format of spool files" "CHAPspool"
33966 .scindex IIDforspo1 "format" "spool files"
33967 .scindex IIDforspo2 "spool directory" "format of files"
33968 .scindex IIDforspo3 "spool files" "format of"
33969 .cindex "spool files" "editing"
33970 A message on Exim's queue consists of two files, whose names are the message id
33971 followed by -D and -H, respectively. The data portion of the message is kept in
33972 the -D file on its own. The message's envelope, status, and headers are all
33973 kept in the -H file, whose format is described in this chapter. Each of these
33974 two files contains the final component of its own name as its first line. This
33975 is insurance against disk crashes where the directory is lost but the files
33976 themselves are recoverable.
33977
33978 Some people are tempted into editing -D files in order to modify messages. You
33979 need to be extremely careful if you do this; it is not recommended and you are
33980 on your own if you do it. Here are some of the pitfalls:
33981
33982 .ilist
33983 You must ensure that Exim does not try to deliver the message while you are
33984 fiddling with it. The safest way is to take out a write lock on the -D file,
33985 which is what Exim itself does, using &[fcntl()]&. If you update the file in
33986 place, the lock will be retained. If you write a new file and rename it, the
33987 lock will be lost at the instant of rename.
33988 .next
33989 .vindex "&$body_linecount$&"
33990 If you change the number of lines in the file, the value of
33991 &$body_linecount$&, which is stored in the -H file, will be incorrect. At
33992 present, this value is not used by Exim, but there is no guarantee that this
33993 will always be the case.
33994 .next
33995 If the message is in MIME format, you must take care not to break it.
33996 .next
33997 If the message is cryptographically signed, any change will invalidate the
33998 signature.
33999 .endlist
34000 All in all, modifying -D files is fraught with danger.
34001
34002 Files whose names end with -J may also be seen in the &_input_& directory (or
34003 its subdirectories when &%split_spool_directory%& is set). These are journal
34004 files, used to record addresses to which the message has been delivered during
34005 the course of a delivery attempt. If there are still undelivered recipients at
34006 the end, the -H file is updated, and the -J file is deleted. If, however, there
34007 is some kind of crash (for example, a power outage) before this happens, the -J
34008 file remains in existence. When Exim next processes the message, it notices the
34009 -J file and uses it to update the -H file before starting the next delivery
34010 attempt.
34011
34012 .section "Format of the -H file" "SECID282"
34013 .cindex "uid (user id)" "in spool file"
34014 .cindex "gid (group id)" "in spool file"
34015 The second line of the -H file contains the login name for the uid of the
34016 process that called Exim to read the message, followed by the numerical uid and
34017 gid. For a locally generated message, this is normally the user who sent the
34018 message. For a message received over TCP/IP via the daemon, it is
34019 normally the Exim user.
34020
34021 The third line of the file contains the address of the message's sender as
34022 transmitted in the envelope, contained in angle brackets. The sender address is
34023 empty for bounce messages. For incoming SMTP mail, the sender address is given
34024 in the MAIL command. For locally generated mail, the sender address is
34025 created by Exim from the login name of the current user and the configured
34026 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
34027 leading &"From&~"& line if the caller is trusted, or if the supplied address is
34028 &"<>"& or an address that matches &%untrusted_set_senders%&.
34029
34030 The fourth line contains two numbers. The first is the time that the message
34031 was received, in the conventional Unix form &-- the number of seconds since the
34032 start of the epoch. The second number is a count of the number of messages
34033 warning of delayed delivery that have been sent to the sender.
34034
34035 There follow a number of lines starting with a hyphen. These can appear in any
34036 order, and are omitted when not relevant:
34037
34038 .vlist
34039 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
34040 This item is obsolete, and is not generated from Exim release 4.61 onwards;
34041 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
34042 recognized, to provide backward compatibility. In the old format, a line of
34043 this form is present for every ACL variable that is not empty. The number
34044 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
34045 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
34046 the data string for the variable. The string itself starts at the beginning of
34047 the next line, and is followed by a newline character. It may contain internal
34048 newlines.
34049
34050 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
34051 A line of this form is present for every ACL connection variable that is
34052 defined. Note that there is a space between &%-aclc%& and the rest of the name.
34053 The length is the length of the data string for the variable. The string itself
34054 starts at the beginning of the next line, and is followed by a newline
34055 character. It may contain internal newlines.
34056
34057 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
34058 A line of this form is present for every ACL message variable that is defined.
34059 Note that there is a space between &%-aclm%& and the rest of the name. The
34060 length is the length of the data string for the variable. The string itself
34061 starts at the beginning of the next line, and is followed by a newline
34062 character. It may contain internal newlines.
34063
34064 .vitem "&%-active_hostname%&&~<&'hostname'&>"
34065 This is present if, when the message was received over SMTP, the value of
34066 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
34067
34068 .vitem &%-allow_unqualified_recipient%&
34069 This is present if unqualified recipient addresses are permitted in header
34070 lines (to stop such addresses from being qualified if rewriting occurs at
34071 transport time). Local messages that were input using &%-bnq%& and remote
34072 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
34073
34074 .vitem &%-allow_unqualified_sender%&
34075 This is present if unqualified sender addresses are permitted in header lines
34076 (to stop such addresses from being qualified if rewriting occurs at transport
34077 time). Local messages that were input using &%-bnq%& and remote messages from
34078 hosts that match &%sender_unqualified_hosts%& set this flag.
34079
34080 .vitem "&%-auth_id%&&~<&'text'&>"
34081 The id information for a message received on an authenticated SMTP connection
34082 &-- the value of the &$authenticated_id$& variable.
34083
34084 .vitem "&%-auth_sender%&&~<&'address'&>"
34085 The address of an authenticated sender &-- the value of the
34086 &$authenticated_sender$& variable.
34087
34088 .vitem "&%-body_linecount%&&~<&'number'&>"
34089 This records the number of lines in the body of the message, and is always
34090 present.
34091
34092 .vitem "&%-body_zerocount%&&~<&'number'&>"
34093 This records the number of binary zero bytes in the body of the message, and is
34094 present if the number is greater than zero.
34095
34096 .vitem &%-deliver_firsttime%&
34097 This is written when a new message is first added to the spool. When the spool
34098 file is updated after a deferral, it is omitted.
34099
34100 .vitem "&%-frozen%&&~<&'time'&>"
34101 .cindex "frozen messages" "spool data"
34102 The message is frozen, and the freezing happened at <&'time'&>.
34103
34104 .vitem "&%-helo_name%&&~<&'text'&>"
34105 This records the host name as specified by a remote host in a HELO or EHLO
34106 command.
34107
34108 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
34109 This records the IP address of the host from which the message was received and
34110 the remote port number that was used. It is omitted for locally generated
34111 messages.
34112
34113 .vitem "&%-host_auth%&&~<&'text'&>"
34114 If the message was received on an authenticated SMTP connection, this records
34115 the name of the authenticator &-- the value of the
34116 &$sender_host_authenticated$& variable.
34117
34118 .vitem &%-host_lookup_failed%&
34119 This is present if an attempt to look up the sending host's name from its IP
34120 address failed. It corresponds to the &$host_lookup_failed$& variable.
34121
34122 .vitem "&%-host_name%&&~<&'text'&>"
34123 .cindex "reverse DNS lookup"
34124 .cindex "DNS" "reverse lookup"
34125 This records the name of the remote host from which the message was received,
34126 if the host name was looked up from the IP address when the message was being
34127 received. It is not present if no reverse lookup was done.
34128
34129 .vitem "&%-ident%&&~<&'text'&>"
34130 For locally submitted messages, this records the login of the originating user,
34131 unless it was a trusted user and the &%-oMt%& option was used to specify an
34132 ident value. For messages received over TCP/IP, this records the ident string
34133 supplied by the remote host, if any.
34134
34135 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
34136 This records the IP address of the local interface and the port number through
34137 which a message was received from a remote host. It is omitted for locally
34138 generated messages.
34139
34140 .vitem &%-local%&
34141 The message is from a local sender.
34142
34143 .vitem &%-localerror%&
34144 The message is a locally-generated bounce message.
34145
34146 .vitem "&%-local_scan%&&~<&'string'&>"
34147 This records the data string that was returned by the &[local_scan()]& function
34148 when the message was received &-- the value of the &$local_scan_data$&
34149 variable. It is omitted if no data was returned.
34150
34151 .vitem &%-manual_thaw%&
34152 The message was frozen but has been thawed manually, that is, by an explicit
34153 Exim command rather than via the auto-thaw process.
34154
34155 .vitem &%-N%&
34156 A testing delivery process was started using the &%-N%& option to suppress any
34157 actual deliveries, but delivery was deferred. At any further delivery attempts,
34158 &%-N%& is assumed.
34159
34160 .vitem &%-received_protocol%&
34161 This records the value of the &$received_protocol$& variable, which contains
34162 the name of the protocol by which the message was received.
34163
34164 .vitem &%-sender_set_untrusted%&
34165 The envelope sender of this message was set by an untrusted local caller (used
34166 to ensure that the caller is displayed in queue listings).
34167
34168 .vitem "&%-spam_score_int%&&~<&'number'&>"
34169 If a message was scanned by SpamAssassin, this is present. It records the value
34170 of &$spam_score_int$&.
34171
34172 .vitem &%-tls_certificate_verified%&
34173 A TLS certificate was received from the client that sent this message, and the
34174 certificate was verified by the server.
34175
34176 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
34177 When the message was received over an encrypted connection, this records the
34178 name of the cipher suite that was used.
34179
34180 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
34181 When the message was received over an encrypted connection, and a certificate
34182 was received from the client, this records the Distinguished Name from that
34183 certificate.
34184 .endlist
34185
34186 Following the options there is a list of those addresses to which the message
34187 is not to be delivered. This set of addresses is initialized from the command
34188 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
34189 is set; otherwise it starts out empty. Whenever a successful delivery is made,
34190 the address is added to this set. The addresses are kept internally as a
34191 balanced binary tree, and it is a representation of that tree which is written
34192 to the spool file. If an address is expanded via an alias or forward file, the
34193 original address is added to the tree when deliveries to all its child
34194 addresses are complete.
34195
34196 If the tree is empty, there is a single line in the spool file containing just
34197 the text &"XX"&. Otherwise, each line consists of two letters, which are either
34198 Y or N, followed by an address. The address is the value for the node of the
34199 tree, and the letters indicate whether the node has a left branch and/or a
34200 right branch attached to it, respectively. If branches exist, they immediately
34201 follow. Here is an example of a three-node tree:
34202 .code
34203 YY darcy@austen.fict.example
34204 NN alice@wonderland.fict.example
34205 NN editor@thesaurus.ref.example
34206 .endd
34207 After the non-recipients tree, there is a list of the message's recipients.
34208 This is a simple list, preceded by a count. It includes all the original
34209 recipients of the message, including those to whom the message has already been
34210 delivered. In the simplest case, the list contains one address per line. For
34211 example:
34212 .code
34213 4
34214 editor@thesaurus.ref.example
34215 darcy@austen.fict.example
34216 rdo@foundation
34217 alice@wonderland.fict.example
34218 .endd
34219 However, when a child address has been added to the top-level addresses as a
34220 result of the use of the &%one_time%& option on a &(redirect)& router, each
34221 line is of the following form:
34222 .display
34223 <&'top-level address'&> <&'errors_to address'&> &&&
34224 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
34225 .endd
34226 The 01 flag bit indicates the presence of the three other fields that follow
34227 the top-level address. Other bits may be used in future to support additional
34228 fields. The <&'parent number'&> is the offset in the recipients list of the
34229 original parent of the &"one time"& address. The first two fields are the
34230 envelope sender that is associated with this address and its length. If the
34231 length is zero, there is no special envelope sender (there are then two space
34232 characters in the line). A non-empty field can arise from a &(redirect)& router
34233 that has an &%errors_to%& setting.
34234
34235
34236 A blank line separates the envelope and status information from the headers
34237 which follow. A header may occupy several lines of the file, and to save effort
34238 when reading it in, each header is preceded by a number and an identifying
34239 character. The number is the number of characters in the header, including any
34240 embedded newlines and the terminating newline. The character is one of the
34241 following:
34242
34243 .table2 50pt
34244 .row <&'blank'&> "header in which Exim has no special interest"
34245 .row &`B`& "&'Bcc:'& header"
34246 .row &`C`& "&'Cc:'& header"
34247 .row &`F`& "&'From:'& header"
34248 .row &`I`& "&'Message-id:'& header"
34249 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
34250 .row &`R`& "&'Reply-To:'& header"
34251 .row &`S`& "&'Sender:'& header"
34252 .row &`T`& "&'To:'& header"
34253 .row &`*`& "replaced or deleted header"
34254 .endtable
34255
34256 Deleted or replaced (rewritten) headers remain in the spool file for debugging
34257 purposes. They are not transmitted when the message is delivered. Here is a
34258 typical set of headers:
34259 .code
34260 111P Received: by hobbit.fict.example with local (Exim 4.00)
34261 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
34262 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
34263 038* X-rewrote-sender: bb@hobbit.fict.example
34264 042* From: Bilbo Baggins <bb@hobbit.fict.example>
34265 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
34266 099* To: alice@wonderland.fict.example, rdo@foundation,
34267 darcy@austen.fict.example, editor@thesaurus.ref.example
34268 104T To: alice@wonderland.fict.example, rdo@foundation.example,
34269 darcy@austen.fict.example, editor@thesaurus.ref.example
34270 038 Date: Fri, 11 May 2001 10:28:59 +0100
34271 .endd
34272 The asterisked headers indicate that the envelope sender, &'From:'& header, and
34273 &'To:'& header have been rewritten, the last one because routing expanded the
34274 unqualified domain &'foundation'&.
34275 .ecindex IIDforspo1
34276 .ecindex IIDforspo2
34277 .ecindex IIDforspo3
34278
34279
34280
34281
34282 . ////////////////////////////////////////////////////////////////////////////
34283 . ////////////////////////////////////////////////////////////////////////////
34284
34285 .chapter "Adding new drivers or lookup types" "CHID12" &&&
34286 "Adding drivers or lookups"
34287 .cindex "adding drivers"
34288 .cindex "new drivers, adding"
34289 .cindex "drivers" "adding new"
34290 The following actions have to be taken in order to add a new router, transport,
34291 authenticator, or lookup type to Exim:
34292
34293 .olist
34294 Choose a name for the driver or lookup type that does not conflict with any
34295 existing name; I will use &"newdriver"& in what follows.
34296 .next
34297 Add to &_src/EDITME_& the line:
34298 .display
34299 <&'type'&>&`_NEWDRIVER=yes`&
34300 .endd
34301 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
34302 code is not to be included in the binary by default, comment this line out. You
34303 should also add any relevant comments about the driver or lookup type.
34304 .next
34305 Add to &_src/config.h.defaults_& the line:
34306 .code
34307 #define <type>_NEWDRIVER
34308 .endd
34309 .next
34310 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
34311 and create a table entry as is done for all the other drivers and lookup types.
34312 .next
34313 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
34314 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
34315 driver or lookup type and add it to the definition of OBJ.
34316 .next
34317 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
34318 &_src_&.
34319 .next
34320 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
34321 as for other drivers and lookups.
34322 .endlist
34323
34324 Then all you need to do is write the code! A good way to start is to make a
34325 proforma by copying an existing module of the same type, globally changing all
34326 occurrences of the name, and cutting out most of the code. Note that any
34327 options you create must be listed in alphabetical order, because the tables are
34328 searched using a binary chop procedure.
34329
34330 There is a &_README_& file in each of the sub-directories of &_src_& describing
34331 the interface that is expected.
34332
34333
34334
34335
34336 . ////////////////////////////////////////////////////////////////////////////
34337 . ////////////////////////////////////////////////////////////////////////////
34338
34339 . /////////////////////////////////////////////////////////////////////////////
34340 . These lines are processing instructions for the Simple DocBook Processor that
34341 . Philip Hazel has developed as a less cumbersome way of making PostScript and
34342 . PDFs than using xmlto and fop. They will be ignored by all other XML
34343 . processors.
34344 . /////////////////////////////////////////////////////////////////////////////
34345
34346 .literal xml
34347 <?sdop
34348 format="newpage"
34349 foot_right_recto="&chaptertitle;"
34350 foot_right_verso="&chaptertitle;"
34351 ?>
34352 .literal off
34353
34354 .makeindex "Options index" "option"
34355 .makeindex "Variables index" "variable"
34356 .makeindex "Concept index" "concept"
34357
34358
34359 . /////////////////////////////////////////////////////////////////////////////
34360 . /////////////////////////////////////////////////////////////////////////////